Erin's 2006 Civic Sedan

erinh

New member
I won't bother getting in to all the nitty gritty details of how this car has evolved. There's plenty of that info elsewhere. I'll just skip to the more recent stuff. I had some big changes in the install thanks to some things that finally clicked in my understanding of audio. Some of the below may be a touch out of date already but I'll try to update when necessary. :)


The following is a direct copy/paste from my build log elsewhere, so if it looks funny, that's why.

I'm no stranger to a build log... in fact, I have a ridiculously long one already on this site here which I started about 5.5 years ago. It documents all the gear I've been through, for better or worse. So, why start another? What's different? Well, as of 3 weeks ago, just about everything. And in a couple weeks the only thing that will remain is my headunit and amps; everything else has been switched out and I've even added a few things extra. All in the name of better sound. At some point, I want to reach the point where I just love rocking out without nitpicking it. The goal isn't as much sonic nirvana as a means to calm my OCD/ADHD tendencies and get back to the root of just really enjoying the music. So far, I think I'm on the best path toward that goal that I've ever been.

About a year ago I started trying to make a video tutorial on how to use the RTA. I realized quickly that I was going numerous directions with it and thought it best to just document steps as I tune my car and post up the measurements/results as I went. However, I spent most of the year changing gear, chasing the elusive quest of sound quality in car audio. I did alright at the end but wasn't happy with myself. I have now pretty much maximized what I'm able to use in the car and, based on all the things I've learned, I've reached the point that I will truly strive to focus solely on the aspects outside of gear chosen (with the exception of a few things I've already purchased but have yet to install). This means tuning and experimentation with new methods of tuning and the norm of car audio itself.

Since I'm starting fresh with a lot of new gear, I wanted to start a new build log. One with a clean slate, much like the install itself. The goal of this thread isn't so much to highlight what I'm using as it is to document how I'm using it and the steps in tuning I'll be taking along the way. In a nutshell, this is going to be my tuning journal with some install type stuff thrown in; mostly at the front.

If there's one thing I've learned since getting engulfed by this hobby it's the fact sound quality is both objective and subjective. Numerous measurements and research are available that explain the fundamentals of human hearing and subjective preference. There is also a lot of gray area because these studies aren't necessarily geared toward the closet sized car audio environment. Though, most of the principles remain and transfer to our hobby.

This is a no secrets, full disclosure build log that will detail - to the best of my ability - the gear I've chosen and why, and the things I'm doing in the car to get the best sound I can. The goal of this build is really to help everyone out. My install choices aren't the same as everyone but there's still a lot to learn from each other as we work toward the goal of achieving the best sound we can in our car. Yea, it's subjective, but the best part is as you adapt and grow more accustomed to good sound, the more you are willing to experiment and try new things to further your knowledge. On the flip side, there are plenty of people with stock systems. Though, I believe those people can still benefit from a little more knowledge. It can't hurt. Right?


Sometimes what I discuss here may work and other times it may not ... but that's kind of the fun of the journey. And, to be fair, I've learned much more from failing at things than I have from getting it right. Ultimately, I hope help folks learn from those mistakes... Help you understand why measurements are so beneficial and also where they have their pitfalls. Help you carry out the same things in your car and share in the enjoyment of a rockin' car stereo system. :D


With that said, here goes...


- Erin
 
First off, the car...


2006 Honda Civic LX Sedan with about 120k miles on the clock. I bought it as a baby with 7 miles on it about 7.5 years ago and I plan (hope) to have it for many more years. I commute roughly 1.5 hours each day to and from work. On a good day, a bit over an hour. I spend a good deal of time in my car and I think that's one reason why I pay as much attention to the audio system as I do. The other reason I'm in this hobby is for the technical aspect of it. I just dig the science stuff and also the ability to use my hands. If not for car audio, I'm not sure I'd have amassed the tool collection I have... and that's a crazy thing to say. ;)


I just took the pictures. I just washed the car (it needed it pretty bad). I wish she always looked as clean... maybe one of these days I'll get it polished and waxed up but the years of interstate travel has taken the luminosity down a notch... or 5. ;)

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The gear I'm using consists of the following:




and now... pictures of how it currently sits. Keep in mind, I'll be updating this with some pictures of the install itself in a bit.


Pioneer P99:

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JL amps under seat. One HD900/5 and RFQ5000 are under the driver's seat. The passenger's seat has the other HD900/5 and HD1200/1.

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Trunk shot which currently has the AE IB15's in an IB wall. This will soon change to a pair of JL's 13tw5 subs for various reasons which I'll address later.

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Rear fill pictures. I removed the OEM rear speaker covers to take these pictures. Otherwise, no one would ever know they're back there.

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Pictures of the front stage:

Grilles on:

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Grilles off:

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I do a lot of speaker testing and post the data to my site (in my sig). I dig it. The cool part is I'm able to share my passion with those who are interested in the science side of things and I am always learning about new things/methods. Most of it isn't really *new*. It's just new to me or I've just now really tried it. I spend a lot of time testing speakers/drivers both objectively and subjectively. I rarely talk about the subjective as it's.. well... subjective. But in the past year or so, I've really started to understand the teachings of the audio 'gods' such as Floyd Toole, Linkwitz, Geddes, etc. Their works have all helped pushed my understanding as a hobbyist further. This ultimately winds up becoming a basis for my current installment of my car stereo, y0!

This is probably going to be a long read so grab some coffee if you care to read further. *shrugs*



Last year I competed in MECA and did alright. Not near as well as I had hoped but given that I was always changing crap, I guess I could only expect to do so good. I made it to Finals and got 5th out of about 9 in my group. I had a fun time hanging out with friends but spent much of my time trying to tune my car thanks to me *once again* switching out all sorts of crap within a few days (though, to be fair, it was mainly due to equipment faults). Anyway, one big thing I took away from MECA Finals last year is I want a car that really takes it to the next level. To do that, I needed to really buckle down on an install and tune what I had rather than switching gear like underwear. That meant getting gear installed the way that made the most sense theoretically and physically and working on the tuning aspect over a period of time; something I hadn't done in ... well... ever. *shrugs*

Listening to Mark Eldridge's car is an experience, to say the least. His car transcends conventional car stereo like nothing I've ever heard. It does a great job of removing the 'sound in a tin can' effect we get in car audio. The soundstage is HUGE; expanding far beyond the physical boundaries of the car. The image is about as perfect as one would expect without sacrificing staging cues (something I constantly run in to personally). Tonality is very nice and enjoyable (I can't define accuracy here as I'm still learning). And this is all from the passenger seat! The driver's seat is even better. ;)

To be frank, listening to Eldridge's NASCAR from the passenger seat beats listening to any other vehicle from the driver's seat. It's just that good. There's a lot of details involved to get this but most of it just isn't feasible for me in a daily driver. And, while I've done some things some people can't do in their cars (ie: larger speaker pods thanks to the Civic's pillar windows), I think most all of us here are in the same boat. That said, I still was aware of things that would be worth a shot to escape the car stereo norm. So, I messed around with a few things over the winter that I thought might help me to achieve the goal of taking my car to the next level. At some point, I really do plan to update this thread with some of these in more detail and explain why I did what I did. I've just not found the time. But, to make a real quick rundown here are the highlights:
  • Ambiophonics
  • Quadrophonics
  • 3 channel front stage using a Center Channel via summed mono
  • 5 channel front stage (L-R, L, C (summed mono), R, R-L)
  • Rear Fill using simple difference signal (ie: L-R)
  • Rear Fill using Dolby PLII


Here's a picture of the setup I used to test rear fill methods:

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The three channel stereo stuff is not new. Initially, stereo was three channels. But mfg's didn't think people could afford three speakers to the standard use of stereo involved two speakers.

There's plenty of info on Google regarding this so I won't bother to link everything. The more interesting things I read can be found here, though:
http://www.audiosignal.co.uk/Resources/Three_channels_A4.pdf
Gerzon Archive
http://www.dolby.com/uploadedFiles/..._Logic_II_Decoder_Principles_of_Operation.pdf

Most of Gerzon's more interesting - to me - work seems to be centered around matrix and recording (mic'ing) procedures.

I tested each of these using some random stereo pieces in my garage. Some of the methods worked really well and were really cool. Others, such as ambio, not so much. I should caveat this with saying that I didn't go through extreme lengths to vet each method. My method was simple: how well does each type of setup perform 'out of the box'. If it performed well, it was worth further pursuit. If not... kick it to the curb.

I settled on a couple from the list above. The next step was to do in car testing. This is where I ran in to trouble. While I had done some testing before, ultimately I realized the car just wasn't going to permit the really cool stuff without considerable dash work and I wasn't for that. That means just about everything was scrapped and I was back to conventional 3-way setup again up front. But, it sure was interesting... maybe one day I can do give it a shot again. Scratch that off the list! :(
 
Let me preface this by again noting:
I'm just a dude playing with stereo using ideas and principles others way smarter than me have provided 20, 30, 40+ years ago. I don't intend to come off as a know it all. These are just my recent endeavors which contribute to my reasons for changing some things in my car.




Around the time my dreams were shot, I ordered some Kef stuff to test. The first was the HTS3001SE followed by the Q100. I chose these because I figured it was time to give a coax a chance. Zaph did testing on the Q100 driver last year and it looked really good but I didn't see a way for me to really use it. Ahhhhh.... anyway, it was just another thing for me to test and wound up being something I really felt hit the mark. Kef wound up making it in the car because of my results.

Unlike standard coax designs, these drivers implement the tangerine waveguide for the tweeter to help provide a more evenly distributed response off-axis. And this is the reason I was so intrigued by these. The more I've experimented with speakers, the more I've found what truly matters is sound power. HD, IMD, etc... that's great to measure to make sure there's no issues. But by far and large the most important aspect of a speaker system performance is the linear distortion (frequency response) on and off-axis. Toole's research shows this and I'm just now realizing the importance of his studies. Linkwitz and Geddes all share similar results. Some links here:
http://www.aes.org/tmpFiles/elib/20130211/5270.pdf
http://www.harmanaudio.com/all_about_audio/loudspeakers_rooms.pdf
Constant directivity loudspeaker designs

The cliff's notes version is that smooth response characteristics is prevalent. And not just on-axis. Off-axis response matters just as much because it contributes to envelopment. That's probably the butchered summary, though. Feel free to do your own research.

A MAJOR component of sound power, outside of smooth off-axis response on the high end, is the fact response matching between two speakers is not trivial. It's the most single important aspect of speaker design that I can think of. Of course, having a good drive unit to start with is still key here as well. It goes back to the whole idea of beaming. We all hear that a sub is omindirectional. This isn't really true. It's omni, but only to a point. This point where it's no longer omni is often referred to as 'beaming'. We see that term used a lot to describe when a speaker gets bright... but that's not really the accurate definition. Beaming is the point where the driver no longer radiates sound evenly based on frequency. However, a driver doesn't just beam at a certain point. It's a gradual effect. At the point where the driver's diameter is approximately equal to 1/2 wavelength it's playing, the response begins to drop off-axis; this is beaming. Note: Really, it's closer to 1/3 or 1/4th, but 1/2 is a good rule of thumb. The further off axis and/or higher in frequency you go, the more directional the sound from the driver is.

For example, let's look at the Scan Speak 10f midrange.
The Madisound Speaker Store

This is called a 4" mid, but the diameter is only about 78mm, measured from surround to surround. That's roughly 3 inches.
13,500 (speed of sound in/s) / 3inches = 4,500 hz.

This number is just the wavelength in sound of 3 inches. We need to get one-half of this to determine approximate beaming. So, we get:
4500hz/2 = ~ 2250hz

The above means at about 2250hz, the response between on axis vs off axis begins to diverge. Looking at the measurements below, you can see this is pretty close to an accurate calculation:
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By the time you reach 4khz, the response between 0 degrees (on axis) and 30 degrees off-axis is about 3dB down. I know Vance Dickison in Voice Coil often references the 3dB point as a notional crossover point. This means you'd want to mate a tweeter with this midrange at (at least) 4khz in order to maintain some type of wavefront symmetry.

Big picture: at the crossover point, there the goal should be to have no difference in the mid's off-axis dispersion and the tweeters's dispersion. Ideally this means, while the tweeter is omni on the low end (again, it doesn't beam until the wavelength is about 1/2 the driver diameter) the mid is - or at least very close to - omnidirectional. This is why tweeters with low Fs are so widely used when paired with a 6.5" midwoofer.

So, two major aspects of speaker/system design:
  1. Good sound power; with no holes in response due to improper crossover points and/or slopes being used between drivers
  2. Smooth off-axis response that doesn't have large peaks and nulls in response. It doesn't have to be flat. But it does need to be smooth! Toole has done research regarding the smoothness of the response of a driver within the crossover points used, which is a bit different than what I'm discussing regarding smooth off-axis response. Essentially, FR smoothness versus directivity index.

Paradigm does a good job at explaining this on their site here:
The Low-Down on Dispersion - Welcome to the New Official Paradigm® Website.

But, here's some pictures they use to describe it.
Mismatched dispersion where the woofer and tweeter have a higher crossover point and the woofer is beaming:
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Now, here's a lower crossover point used where the woofer and tweeter share similar dispersion:
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What does this really mean, though? IME, as stated above, it contributes to envelopment. When the crossovers are set such that the off-axis response between mid and tweeter blend extremely well, there is no 'hole' in the response. The sound is spread throughout the listening environment and what you get is a shared chaos that kind of takes the room by the hand and says "come join me, dude". The soundstage opens up... like BAM! Staging and instruments on the stage are much more spread out (when needed) and things just *sound* more natural. How real it sounds depends on the response curve itself but if you're building a proper crossover point with all the above information in mind, odds are you're also using drivers with very good response or at least crossing within the band before the response gets hideous.


To get good sound power, proper crossover use is absolutely necessary. This isn't trivial. When you separate speakers by some distance you also have to account for lobing of the two wavefronts along with other details that I can't even recall. Ideally, you'd have one driver that does everything. This is why wideband/fullrange drivers are so popular. However, they have issues of their own. One large issue being modal issues which can make for very poor response both on and (especially) off axis. Some companies have gotten to the point where these issues are tamed but no one has perfected it. I just don't see it ever happening. So, it's a tradeoff.

The alternative is to use a Coaxial speaker. They are rife with their own issues. I've used car audio and home audio coax speakers in the past and not been impressed. They all had issues. Especially the ones with the tweeter mounted above the mid. Coax's with the tweeter mounted inside the woofer are considered concentric and have large benefits, yet even those are problematic in response. The Seas designs like these have nasty resonances in the mid and tweeter. A couple years ago my buddy Kirk was trying to get me in to Tannoy dual concentrics but I was too naive to understand the benefits. Since then, I've come around. I tested the Kef HTS3001SE, Q100 and R300 coax drive units recently and was very impressed by the results; both objectively and subjectively.
Kef’s HTS3001SE… I cracked the Egg! | Medley's Musings
Kef Q100 Speaker Drive Unit Testing | Medley's Musings
Kef R300 Midrange Drive Unit Testing | Medley's Musings


Each is a step up with the HTS3001SE drivers being on the low end and the R series being the top. However, even the lower level Q100 bookshelves ($400-450 used on ebay for a set) are far beyond any standard 2-way speaker design I've heard yet. At their price point, there's nothing I've heard better.

Kef also makes and employ smaller, lower cost version concentric speakers in the 1005SE:
KEF KHT1005.2SE Home Audio Speaker System w/ White Satellite Speakers - Newegg.com
I have yet to test these, but the big difference besides size (these are about 3 to 3.5"; the others are no less than 4.5") is the fact they do not use the tangerine waveguide. There are obviously other differences.

After testing these and enjoying them so much, it seemed only natural to make them part of my install. Right?... I mean, I change gear all the time so why not...

The HTS3001SE would be a good choice as it's a bit smaller but I wasn't a fan of the plastic basket so much. The Q100 is a great midwoofer/tweeter combo so that was an option. Unfortunately it's OD is just a touch too large for my use. The R300 driver comes from a $1200 set... OUCH. You can't buy these separately, either. Luckily, someone who is a fan of my site helped me out here and I wound up getting a set of R300's. They're large... very large. And much more a dedicated midrange with design implementations to carry out this task (shorting rings, ribbed cone). So, that's what I chose. And that's what the goal of the recent pillar build was to house. So, here is what is in my pillars now:

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Now, back to this whole crossover design junk... this is where passive systems fail because no one knows where the mid and tweeter will be installed. It's kind of a crap shoot. Active allows you the opportunity to set the crossover points yourself, for your own install, and hopefully get a better sound. Well, you can't really measure the car for crossover points directly, though there are methods you can try that would help you get there... it just would take a while. There's no way to really simulate a car install for the purpose of taking measurements because you can't simulate a tweeter in a pillar and a mid in a door. This is where having the concentric design is really cool. Since the mid and tweeter are designed together I can measure them on my baffle to determine the best crossover points and settings. So, I mounted the drive unit on my test baffle and connected the Arc Audio PS8 to my amp. I ran the speaker active and then started playing with crossover points, focusing on maintaining a smooth response on and off-axis and having no holes or bumps at the crossover point when measured off axis. If the crossover point between these two are good out of the car, then I know I'm starting with the best basis I can before it even gets in the car. One could argue against this but it seems to have worked very well based on my own subjective evaluation.

Here is the result I landed on. The crossover between mid and tweeter was about 3khz with an LR2 slope. The measurements are 0, 30, 45, 60 and 90 degrees. There is no EQ.

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When I averaged all the above together and smoothed the response to 1/3 octave, I get this:
http://medleysmusings.com/wp-content/uploads/2013/02/drive-unit-average-one-third.png

In some ways, it very much emulates the JBL MS-8 target curve. This is simply a function of Kef's design seemingly targeting smooth sound power, which is all rooted in Toole's research mentioned way above.

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Now, on to the car install and results....
 
Once I decided I wanted to use the R300 coax driver, I started ordering supplies. My buddy, Steve Cook, a very highly regarded install and SQL competitor (former SPL with records to show for it) and owner of Audio X in Florence, AL suggested a few items to get the job done.

So, here's a small list of stuff I picked up:


After talking to Steve about this I decided to just have him (all but) do it for me. I suck at fiberglass work. I do really enjoy it.. really. I just suck at making things look good and I don't have a lot of spare time since my wife works nights. For the sake of time and cosmetics, I headed to Steve's.

I purchased a spare set of OEM pillars to hack up. Picked them from a junkyard for about $22 total... I had paid about $80 for a pair on ebay last time. :rolleyes:
I showed up and we decided fitting the 5" drivers wasn't going to be easy. But, we made it work after cutting up the pillars a bit to make room. We secured the rings via CA glue and some plastic staples he has (those things are awesome, btw). Once the rings were secured, we taped off an outer mold with the aluminum tape. Since the tape is sticky on the inside, he showed me that you could just lay FG mat on the tape from the inside and it stays put. Resin was applied. Then the tape was removed. Kitty hair and bondo were used to fill in voids and then sanded smooth.


All in all, it turned out really good in MUCH less time than I would have spent doing it myself.


Here are some build pictures.


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Spray glued:

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Once the build up was complete and the materials dried, we wrapped them in headliner fabric purchased from JoAnn's Fabric Store.. It is backed with about 1/4" of foam. Here's a picture of it:

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I needed to make some rings to hide the speakers when needed. I didn't want anything permanent, such as stretching cloth over the pillars, so rings made sense. Magnets seemed the best way to go for ease of access in case it's ever needed. Steve found a set of chrome rings at a truck stop and had them in his shelves. We checked the size and they fit pretty well. The OD is a bit larger but the cool part is the holes were lined up for my speakers and since they're metal, magnets stick already. So I got those from him and started working on them tonight.

I sanded down the ring where needed then applied CA glue to the ring in the spots needed, placed the magnets in those spots, then sprayed accelerator. I got the glue and accelerator from Amazon. It can be purchased just about anywhere apparently, though. Here:
Bob Smith 106 Insta-Cure 1/2oz Gap Filling - Amazon.com

Insta-set accelerator pump 2oz Bob Smith Ind. - Amazon.com


I cut some grille cloth to a square and got it ready. I used spray glue on the rings and laid them face down on to the cloth, and held in place until dry. Not sure this will hold forever, but I'll see. I then just stretched the cloth tight before the glue dried and then trimmed off the excess. Took me longer than it would a halfway decent installer, but it turned out alright.


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Lessons learned: I sprayed too much glue the first time and when I stretched the cloth it just slid and drug glue across, exposing the chrome. It doesn't really show through unless you're looking for it. But just a caution to anyone that might try this sometime.

Also, keep a roll of painter's tape around. it helps to pick up any overspray or glue that got on your fingers and then on your fresh new cover rings. :rolleyes: ;)
 
So, how does it sound?

The result is easily the best 'out of the box' sound I've ever heard in my car. I spent about two hours on tuning the car, getting basics such as T/A and levels right. Out the gate, the mid and tweeter blending is superb. Absolutely the best I've ever had it in my car. Obviously, at least to me, the concentric design and appropriate crossover points is the fundamental reason why. FWIW, I also chose to use LR2 slopes based on not only measurement, but listening tests as well. I asked my wife to switch presets back and forth on the PS8 so I could demo LR2 vs LR4 and always chose the LR2 as the one that sounded better. I may even have my notebook paper on my bench for proof. The difference I noticed was the dynamics were better. Sound just had more pop to it and it wasn't prematurely cut off. The breadth of the stage actually seemed better as well. This was akin to flipping tweeter phase only back and forth... it sounds different... just couldn't quite put my finger on it. But, outside of depth, there was a pretty nominal improvement. I had somewhat hoped LR4 would sound better as it provides a bit more tweeter protection but it doesn't seem to be an issue anyway so I ran with it.

In the car, I chose to toe the driver's side speaker to about 15-20 deg off axis. This was done to lessen the need to attenuate the top end but also to keep the driver from sticking out on the dash further than I had wanted. There's another reason I did this, too. Stereo research I had done pointed at the best setup as being 30 degrees toward the listener, when the listener is at center. So, I chose to aim for something like this. Where both speakers are aimed the same way with respect to center (of the car). The idea was simply that if I did this, I could then attenuate the near side and delay properly. That would result in the sound arriving closer to the same time.

Even though the direct response on axis isn't the same, it's negligible because the entire radiated sound that I hear is a result of EVERYTHING in the car. This again gets back to what Linkwitz, et al discuss. I don't want to separate the environment. There's no way to do it realistically. So, if you can't beat em... join em. That notion has resulted in the best sound I've had yet. It would not work if I weren't paying special attention to sound power, though.

YMMV.
 
and on to the kicks...


I really wanted to squeeze some shallow 10's up front. Not for basshead reasons as much as basshead oriented SQ reasons. You'll understand in a bit...

I tried my hand at it but there's just no space in the little ol' Civic. Luckily, however, the kicks made it easy to house a set of 8" midbasses. I had used the JL ZR800's a couple years back but they took up more room than I wanted, as I was unable to hollow out the kicks. Flash forward to now and I had no issues with notching the kicks to allow an 8".

If you've followed this build you know the kicks previously housed the Scan Speak Illuminator 18wu which were AP'd to the outside world using the Scan Speak variovents and some material I used to tame the enclosure Qtc. The JL ZR800's like to be open on the back thanks to their higher Qts (and likely higher Vas, I'd imagine) so I simply removed the material I had sandwiched in the variovents and the JLs vent externally with no material to lower the impedance. I have yet to take actual impedance measurements but they work well and I don't really see a need to do this as they are installed in the manner JL recommends (nearly pure IB).

All said and done, the kicks stick out about 1/2" further than they used to which isn't bad at all. A fair trade off for the extra output. I need to trim the carpet so it's not bunched up as shown below but I was in a hurry to get the car together and the last concern on my mind at the time was bunched up carpet.

I used some very heavy duty metal mesh to protect the drivers; the same stuff I used to shield the Scans from damage. I can stomp on the grill and not have worries. And with the automotive carpet overlaid on them, there's weather guard as well.


My impressions of these are: WOW. Of course, what would one expect with 8's in a proper enclosure in the floor. I have had nothing but compliments on the midbass so far. I had to use the usual cuts in EQ to help tame some cabin resonances at the listening position. Namely, 125hz on the left side. This had to be cut about 3dB. Both the left and right EQ have cuts at 125 and 160hz. I have a pretty nasty mode at about 142hz but can't touch it with a graphic EQ so I have to use the 2 bands nearest to that problem frequency I do have. When the PS8 goes back in the car I'll be using it's PEQ extensively for these problems. I also had to do a couple small cuts at 63, 80, and 100hz to shape out some tonality things. But, overall, this is the best midbass response I've had. Not even in terms of sheer output (which they certainly have), but in terms of blending. The JLs are crossed at 40hz/12dB and playing up to 200hz/24dB, if memory serves. To blend the sub all it took was proper level matching and some cutting of the sub at 30hz by about 4dB (if you model the AE's in a largish box which is essentially what the trunk is you'll see why). This helped immensely to get rid of some pull to the rear while still providing the output needed. 40 and 50hz were shaped by about 0.5dB to 1dB depending on driver and side (left or right), again, to help shape out the response and blend the mid/sub together. Overall, I'm extremely happy with the switch the 8's. It afforded me output but most importantly, it made the job of blending to the sub much easier and I have yet to have run out of steam on the low end. It may not be bonecrushing but it certainly can be if I choose to let it be. ;)





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test fit:

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Installed.
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I mentioned some of the EQ things I did above and I thought it would be a nice segueway in to discussing some measurement methods I use. This might be helpful to others and hopefully ultimately save you some time when you start doing your own.


You probably know of the importance of a good spatial average when RTA'ing your system. If not, please read the attached PDF by Geddes which is a study he did for Ford Automotive. It's not too technically heavy which should keep the "I don't like science" excuses to a minimum. ;)

The cliffs version is simply this: your car (and home) are wrought with reflection inducing panels/walls. When measuring response in the environment, you have two options:
  1. "Gate" the response so you obtain only the response of the speaker you're trying to measure and you essentially ignore everything else.
  2. Measure everything: speaker response and reflections.

Doing the first in the car?... good luck. How about... don't bother. At least not until you've gotten really good at measuring and understanding what you're measuring. Let's just say for all intents and purposes you won't be doing the first... like... ever (thank you, Taylor Swift, for making that phrase weird now). Really, it's just pretty much trivial unless you have a very specific goal and understanding of how to achieve it this way.

So, we do the second option. The issue, then, is the fact every measurement you take is a measurement of EVERYTHING occurring at the mic. This is good and it's bad. It's good in the way that there's not a whole lot you can do to the speaker itself so it kind of keeps you from worrying about it. - Although, this is why I really encourage people to study independent tests or do their own to understand the issue(s) with the speakers they've chosen before they use them in the car. - It's bad because, thanks to the nature of the reflective environment, you can't really trust a single point measurement (a measurement taken with the mic in one location). If you move the mic as little as one-half inch you'll get a different result. Most notably in the higher frequencies. This means RTA'ing your car for any desired curve by using one mic measurement is a TOTAL WASTE OF TIME. It's ideal to take multiple measurements in the "head area" and average them together. TrueRTA, OmniMic, and REW allow you to do this pretty easily. Then you have what is known as a good spatial average. It's not an exact method but it's the most realistic and approximates a very realistic response in the seated position.

For this spatial average I usually just do six measurements total at/near the headrest broken in to (2) sets of (3) measurements. Each set is with the mic pointed forward; one in the center and one to each side of the center a couple inches over. The first set at one level. The second set is simply done by raising the seat height up. If your seat moves forward when raising it, keep in mind your level will rise by just a touch thanks to the mic being closer to the speakers. Not an issue but just wanted to note it.

Now I've got 6 measurements. What next? Simple: average them all together to get one measurement.

Here's an example....

All six measurements taken by the method described above (no smoothing applied):

6-drivers-seat-measurements.png





Same as above, but with 1/3 Octave smoothing:

6-drivers-seat-measurements-one-third.png






All of the above averaged in to one response:

average-one-third.png







Let's talk about the above... at least my personal take on the above. I'm sure others may key on to some other aspects I might otherwise ignore or just overlook.

Notice how the response varies more the higher you get in frequency? This is exactly why I said using a single point measurement to tune to a curve is a very bad idea.

I'm going to ignore the shape of the curve, however, for this post... what I really want to focus on is midbass/subbass response, so let's look below 300hz. Anyone notice the one glaringly different thing about the response below this frequency versus the response above it? No matter where the measurement was taken, the response is pretty much the same. This is the critical frequency area (schroeder frequency (Fs)). Linkwitz gives the most simple definition I can think of here:
The frequency fs is also called the Schroeder frequency and denotes approximately the boundary between reverberant room behavior above and discrete room modes below.

Which makes sense, right? Look again at the graphs I provided. Reverberation is occurring above about 300hz as evidenced by the diverging responses from the 6 head area measurements. Below this, the response is pretty constant in this area so it is modally (sp?) dominated. What does this mean to us? You can ignore spatial averaging (multiple measurements) when focusing on low(er) frequency response! This saves you time! Of course, every car is different so I suggest you always do a spatial average to determine where this Fs occurs in your car, but you can expect it to occur around the 200-400hz area, depending on car size. The larger the 'room' the lower the Schroeder frequency. This means once you do a spatial average you'll know where this frequency is. From then on, when you only care about working on the low frequency response, you can ignore spatial averaging and just put the mic at the seated position and measure, tune, measure, tune, rinse, wash, repeat until you're satisfied. I will caveat this by saying that tuning low frequency response with graphic EQ's isn't easy because modal peaks and dips are often too narrow and too specific of a frequency to effectively be targeted by graphic EQs. This is where my subsequent posts will sort of pick up.



Cliffs:
  • Tuning based on one mic measurement is a waste of time. This has a caveat...
  • Take a few measurements in the head area, where you sit. Look at them all overlaid. Where do they really start to diverge? This is your car's Schroeder frequency.
  • Above the Schroeder frequency you must take multiple measurements and average them if you want to tune via RTA.
  • Below the Schroeder frequency, one mic measurement will suffice since the response doesn't change enough to matter.
  • Graphic EQs aren't the best tool for fixing response issues low in frequency. Parametric EQs are MUCH better. But, if all you have is a graphic use it to the best of your potential.

I'll stop there before people gloss over. Next post...
 
Taking off from the above, I'm only going to focus on the response below 300hz (graphs are out to 400hz for the sake of resolution).

The following is with no EQ. Time alignment and levels have been set, however.

First off, let's take a look at the difference measured from the driver's seat vs the passenger's seat.

driver-vs-passenger.png



The results show the same response show pretty much the same curves above 70hz. I've seen this numerous times; almost as if the car has varying Schroeder frequencies. One is for the entire cabin; the other is for one location at a time. Of course, I'm not talking about moving the mic to the rear of the car... that's an entirely different can of worms. The point in this measurement, however, is to show that there is actually a sub-band that really needs attention below the seated Schroeder frequency: the midbass band is entirely subject to this. As shown, 70hz is the starting point for different results between seats but 300hz is about the starting point for different results within the same seat. So, 70hz to 300hz is gonna be a total PITA in my car. Through about 5 years of dealing with this same car, my measurements show me what I already know, so it's definitely been vetted. ;)



Next...
 
After doing that, it's time to get back to the driver's seat and start measuring response from there.

One might choose to measure the system response as a whole and use the RTA that way, but it's a bit more conclusive to study each individual side's response (left and right side response). This is easy to do: just pan the balance to one extreme or the other and measure. When you do, you'll have the left side stereo contribution vs the right side stereo contribution.

So, here we have just that. Panned left is Green. Panned right is Purple. No EQ. 1/12 octave (to show the crappy little modal stuff that 1/3 doesn't get).

left-vs-right-no-eq.png



What this really shows me is that both the left and right side stereo contributions have their own problems. Notice that slight dip around 85hz at the driver's seat? Everyone has that problem to some degree because of their proximity to the speaker. Bottom line, that dip is a cancellation mode. There's nothing I can do to fix it, either. I can EQ it up but what will happen is I'll just keep applying more power to the driver's side midbass, causing distortion to ramp up and likely audible issues due to it. And while it may raise the response there, it'll also make resonant modes more problematic. The potential to damage the driver certainly exists. There's just not a whole lot you can do here. Some EQ will help but if you try to flatten it out by adding 4-5dB of EQ you'll alter the response curve in a negative way and create other issues. The only way to really fix a problem like this is to move from the boundary causing the null or move your driver(s). So, I just ignore this. Truth be told, it's not a real big issue when listening. And this is just one more example of why you should not rely entirely on the RTA. You should always use your own ears to accompany what you've measured. If you have a narrow dip it's not as audible as a broad dip; the same goes for a bump in response.

So, yea... I'm not going to sweat that dip at 85hz measured at the driver's seat. It's a lost cause and serious waste of time to try to flatten it. I just want to smooth it so a bit of EQ here and there will help that.


Now, look at the rest of the curves. That dip around 85hz on the left side is exacerbated by the rise in response around 125hz. After looking at the decay plot, measured by REW, I see why...

left-side-modal-issues.png



This is a plot of response over time, laid out in 2-D. The highest levels are closer to the initial response time. As the graphs change color below one another, you're seeing 'slices' of the response in time. Look at the legend. It shows time in milliseconds (ms). Each color corresponds to a time slice/section. Ideally want to see is each slice dying out quickly and contributing less and less to the results. However, what you actually get is modal issues showing up... these are the ones that linger around and don't taper off smoothly. Looking at these plots is pretty subjective and really should be used with some subjective listening as well. But, I'll give some thoughts on how I look at it...

The 125hz issue showing up in the left side FR plot... now look at the decay plot around that frequency. See how the darker blue looks pretty mountainous here with a dominant spike at about 125hz? Notice how the shade of blue just before this has the same spike? This is an indication of a modal issue. Luckily, I have an EQ band right here... I can cut it some. The problem, however, is cutting here also affects the tonality in other ways. With a parametric EQ, I can set a narrow Q and cut accordingly. But, I don't have that, so I have to cut here with the 31 band EQ. Here is the result when I use the EQ to cut 125hz by 3dB:

left-side-modal-issues-125hz-3db.png



Not surprisingly, there was no miraculous alteration of the issue. It cut the problem by 3dB as it should but it didn't make the ringing issue go away. It did lessen the effect some. This is where subjective listening will tell you if it helped. The drawback here is you also changed the tonality of the system because the Q (bandwidth) of the 1/3 octave equalizer is so wide; it doesn't just change a single frequency.

This site is a great reference for what frequencies influence what you hear and can help you understand the tradeoffs you deal with when changing EQ bands to fix problem areas:
Interactive Frequency Chart - Independent Recording Network



There are other frequencies that do the same thing. 100hz definitely lingers. 83hz lingers as well. Remember earlier my bit about bumping up 80hz to fill in that hole caused by the left side response? What do you think happens when you do that regarding the modal issues? It's a nasty problem. What you really need is a way to target specific modes without negatively affecting the other areas you want to fix with standard EQ methods. This would be a really good intro in to why parametric EQs are so good. So, I'll stop here and pick up there when I have the chance.

Keep in mind I've only really discussed one component of the system response here. The right side response has it's own problems as well.


Cliffs:
  • Room modes suck. They muddy up system response as a whole.
  • When the midbass is muddy it overshadows everything good about the rest of the system.
  • All cars have modal issues smack in the midbass area. :mad:
  • Standard EQ can only go so far. But when properly used, EQ can help tame some of the modes which results in a much more tonally pleasing car stereo and much better blending with sub on the low end and midrange on the high end.

/



Hope this stuff helps you guys out!


- Erin
 
As mentioned above, I use REW for my testing. It's free and pretty easy to use once you figure out how to use it. :blush:
I've used every bit of software under the sun. At this point, I've just grown to like REW more than I used to so I've gone back to it for my tuning measurements. For those wanting to see how I'm using REW, here's some info.

RTA vs Impulse Response Measurement Method:
One thing to note is there are different meanings of the term, at least how we use it:
  1. RTA - Real Time Analyzer:
    • This is simply a real time measurement of what the mic hears. Birds chirping, subs playing... whatever. It records it.
    • RTAs are typically used to record pink noise.
  2. Impulse Response:*
    • This can be a form of RTA, depending on how you look at it. An impulse is used typically to measure something before a reflection because you can gate the response. In other words, let's say I want to measure Speaker A. I know that the walls and floors create reflections occurring after 3 milliseconds (ms) that will 'tarnish' the speaker's response as measured by the mic if I let it. To keep this from happening, I look at the impulse response, tell the software to ignore everything after 3ms. Bammo... no more reflections in the measurement. Just Speaker A.
    • The impulse response is measured by sweeping a sine wave and capturing the response.

* I have severely watered down my explanations here and there are caveats; especially when you get in to different window type methods. But for the sake of this post, it's fine.

The bottom line: In a car, you don't care about impulse gating. You can't really achieve a reflection free zone so there's not much point in trying. -- If you care to disagree please see discussion and reply here (link) so I don't get this one junked up). -- Therefore, we just disregard the whole gating process. That leaves us with a very long impulse response that matches what an RTA would show you, if the signal were the same (ie: pink noise). IOW, using a very long impulse window (100's of milliseconds) in the car will yield an RTA measurement.

Why use this impulse method if it essentially nets you the same thing as an RTA measurement? Because RTA measurement only gives you RTA data; SPL vs frequency. You can't get Decay or some of the other things I am looking to get. More data. That's all. I get in to it more below.



Cliffs:
  • When measuring a car, there are a couple ways to do it.
  • RTA and Impulse are not the same. They each have their own use. However, when the impulse is used without filtering or gating it, it nets you the same result as an RTA.
  • The benefit of using impulse measurements are you get more data such as decay, group delay, etc.
  • Like a standard RTA measurement, multiple impulse responses should be taken and averaged together if you want to tune to a car.
 
I'll discuss how to use either of the two methods listed above. But first off, let's discuss the equipment you need and why you need it.


  • If doing RTA only measurements all you really need is:
    1. A CD with pink noise
    2. A mic to capture the sound.
  • If doing impulse measurements you need two things:
    1. A way to use the software's signal generator and send that signal to your audio system. This can be done by using a soundcard output and run it in to your audio system auxiliary input.
    2. A mic is used to capture the sound.

If you are looking to achieve a target curve of any sort you MUST USE A CALIBRATION FILE with the mic.



-------------------------------------


For impulse measurements, this is the gear I'm using. It's pretty simple:
  1. M-Audio Transit. This sends the signal from REW software via a 3.5mm male/female cable to my P99's auxiliary input.
  2. Dayton Omnimic USB microphone. It comes with a cal file.


You don't have to use what I have. In fact, you can save a good deal of money by simply using:
  1. Your laptop's built-in headphone output
  2. This Dayton mic (click link here). There are numerous other mic alternatives. This is just an easy one with one USB cable. Plug and chug. And it comes with cal files.


------------------------------------------


You know what you have to have. Why do you have to have it?
  1. The soundcard output is used to send the signal to your auxiliary source. Every headunit should now have one of these. This is how I do my testing most of the time. If it doesn't, you may be limited to using the pure RTA method only.
  2. The mic records the system output. Simple as that.



-----------------------------------------


Here's some pictures of my gear:


M-Audio Transit, using the output via a 3.5mm headphone extension cable.

IMG_5813.jpg


IMG_5819.jpg





Dayton Omnimic USB mic (it has electrical tape because I broke the tip; these things are pretty fragile and I made a goof):

IMG_5814.jpg






Mic in the headrest:

IMG_5822.jpg


IMG_5827.jpg






3.5mm aux cable plugged in to my headunit's aux input on the face panel:

IMG_5836.jpg
 
Woke up early before the little one did to make this video so forgive me if I sound half dead and my video has the shakes. ;)

This covers only the RTA aspect of using REW. I'll post another video soon showing how to use the impulse measurement method since I feel it's a bit more complete depending on what you want to do and given I'll be posting results from that kind of measurement.

Let me know if you have questions.



[youtube]bds759UuWiU[/youtube]



- Erin
 
AE IB15's are now out of the car. I'm considering ways of implementing the JL 13tw5's now. Got a few ideas. The good news is that the space savings is going to be about 4" in depth if I go the route I'm most likely going to go. I'll let it sit tonight and think about it a bit. I hope by this weekend to have the JL's in the car and playing music.


IMG_5854.jpg



IMG_5855.jpg



IMG_5860.jpg
 
sub enclosure progress....

IMG_5861.jpg



for what it's worth, what I've decided to do is a bit off the mark of my initial intentions. but for a couple reasons which are somewhat scatterbrained.

One thing I learned from experimentation is the trunk causes problems. It did IB and it does with a sealed enclosure. With any enclosure in the trunk, what you get in to is a cancellation from the sound hitting the rear of the trunk and bouncing back forward in to the cabin. That's just the nature of the beast. In addition, the trunk is one more area that can be excited. As I found through some playing around with over the past few months, this is a problem for me. So, I wanted to eliminate the trunk. I had planned to make a modular setup. One that attached to the existing IB wall and removed. But, I found doing this really was more trouble than it was worth. Instead, I picked up some void free birch in 1/2" size and attached it to the existing wall. Weight added is less than 5lbs which is minimal considering the space savings. Using the existing IB wall as a basis for the enclosure allowed me to only consume about 4" of the trunk as is. A savings of nearly 4 inches itself.

What I'll be doing to finish out the enclosure is placing a piece of wood behind the baffle wall. Picture in your head taking a standard IB setup and just putting a piece of wood behind the woofers. Now you have a sealed setup. Doing this, with the trunk dimensions I have, provides me over 1 cube per driver at 4" depth consumption. This means I have wiggle room. If I want to decrease the enclosure size per driver, I simply move the rear wall forward. If I move it up an inch I can lower the Qtc and save space. I plan to do some testing once the baffle wall glue dries and I get some pieces of wood cut to play with enclosure size.
 
rear wall test fit went well. I had to break out the baby sledge to get the wall in place. It ain't going anywhere without significant effort... and that's without screws. ;)


I'm going to finish it all with carpet. Right now I'm just trying to make sure everything goes where it needs to. I'll be doing some sweeps with the dayton DATS soon.

IMG_5876.jpg



IMG_5877.jpg




13tw5v2's are in. I did an impedance sweep on woofer in its own chamber and the difference in Qts is only 0.01 (0.629 vs 0.619). ;) :D

Initial impressions: I made the right decision to switch. I'll give it a bit more time to sit and discuss my impressions after the new factor has worn off. But for now I'll say that my reasons for going with the wall/enclosure design paid off.

I need to lay some carpet over the baffle but had to put the car together to drive to work tomorrow so that'll come this week.

IMG_5881.jpg



IMG_5879.jpg
 
I did some very minor work on the kicks last night and tonight. I had some serious gaps thanks to the grilles I used to protect the speakers. So, I used some great stuff foam to fill in the transition from floor to kick cover and then sanded it down a bit. Nothing special... and carpet will go over it. But at least now I won't have a large hump from the floor to the speaker.

IMG_5930.jpg



IMG_5931.jpg
 
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