# 68 Cougar SQ System (early planning)



## stanger89 (Jan 8, 2022)

Hey all.

I've been "out" of car audio since the 90's probably, but I've always appreciated good sound. Anyway, I've got a car project underway, and a friend of mine has been trying to convince me to do HLCDs for a while but I had always written them off because of the size. The irony is, HLCDs might actually be easier than tweeters in this car since there's actually more room under the dash than my newer cars.

Here's what I'm thinking:

Stevens HLCDs
Stevens MB6
Rear Fill (yes or no?)
Sub(s) in/through the rear deck with box underneath.
DSP Amp
The overall goal is to have the audio system "match" the level of quality/care/effort I'm putting into the rest of the car, and I also want it relatively stealth such that it doesn't look out of place in a classic (but significantly updated/upgraded) car. Some more details/questions:

I'm debating between the large and mini HLCDs. Passenger side is no problem, but on the driver's side the minis would fit better due to the steering column. Unless I could "notch" that horn slightly to fit around the column. So the question is, what are the compelling arguments for the large horns? It sounds like they play a bit lower from what I've read.

I've got room for 6.5's in the kicks so the MB6s seem like the natural choice there.

For power, I really like the idea of a single, DSP/Amp. At one point I was looking at the Zapco ADSP-Z8 IV, which looked about perfect, but it seems that support from Zapco isn't that great, so now I've been looking at Helix. I'm quite liking the V EIGHT DSP MK2. I've been reading about them and playing with their software in Demo mode and like the ACO features. I do sort of wonder if that would have enough power for the sub(s).

On the sub topic, I just want something to fill in the low end that's missing if you have just 6.5's, I had my fun with shooting for high SPL when I was younger, and I don't listen super loud, but I do like to turn things up a bit for my favorite songs. With that in mind, my thought has been to put the sub(s) in/through the rear deck with the enclosure underneath. I'm somewhat trying to minimize the volume. I can fit a couple 8" subs easy, 10"s are possible... The first option that popped up in my research was the Focal P 20 FSE, later I saw the AudioFrog GS8ND2, and after deciding I had more room to play with I started looking a bit at 10's like Stevens/AudioFrog. I've been doing a lot of playing in WinISD with different subs and box volumes, and also using it to roughly simulate cabin gain, which has all be both enlightening and confusing.

I'm sort of inclined to write off the Focal because it seems to have a pretty large peak in response depending on enclosure volume, which makes me wonder if it might be "boomy" for lack of a better description, though it is intriguing that from WinISD it's at least 3-6dB louder than the other options from 20-70Hz or so, but it sort of seems "too good to be true".

Now the confusing part is in relation some of the other options I've looked at. If I assume about .7 ft^3 per sub, the AF GS8ND2, GB10D2, and Stevens SA10, all have a response in WinISD within about 2dB of each other. Intuition tells me that I'm overlooking something (large signal vs small signal?) and that the 8's would be underwhelming. But the flip side is I know I'm not going for SPL records, I listen at < 100dB, probably <80dB most of the time, and since I just want that bottom end that 6.5 midbass' can't do filled in, that maybe processing can mitigate the differences.

OK, that's probably enough rambling, I realize this is more of a "help me design my system" but I'm hoping to get a bit more SQ-focused input and since I'm thinking of HLCDs I figured I'd try here first.

Thanks for any input!


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## oabeieo (Feb 22, 2015)

The focal fse has a high Q, I’ve installed many of those in small sealed, the peak is nothing but helpful in frequencies you need it. High Q speaker vs high Q enclosure are two very different things. I don’t know how as I am not a speaker designer. But they sound very different as far as how the speaker takes power at lower frequencies…


Example, put a mid Q driver in a tiny tiny box to get the box Q to 1.2, put substantial power and it sounds spitty in its peak. 

Put a high Q driver in a box that keeps it’s Q , like a driver Q of 1 and a box Q of 1.1 and it’s smooth through the peak…. The box is ob much bigger then the other example, but speaking of Quality (Q) the high Q speaker works excellent throughout the peak 

This is just what I’ve studied using that same focal driver. And the 8” fse also….

As to why…. I don’t know , but it was an obvious observation


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## Eric Stevens (Dec 29, 2007)

stanger89 said:


> I'm debating between the large and mini HLCDs. Passenger side is no problem, but on the driver's side the minis would fit better due to the steering column. Unless I could "notch" that horn slightly to fit around the column. So the question is, what are the compelling arguments for the large horns? It sounds like they play a bit lower from what I've read.
> 
> You can notch into the FS horns to allow you to clear the column. Both will work excellent, I prefer the FS.
> 
> ...


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## stanger89 (Jan 8, 2022)

oabeieo,

Thanks for the info, maybe that's my real question, how much to trust simulations in picking drivers.... It's been a while since I've built a box, and back when I did it was generally with a known/specified driver and available volume. For this project, maybe I've got too many degrees of freedom to choose from 

Eric,

Thanks, I did a little measuring and it looks like the "line" from the passenger side driver location to the drive's seating location would be about 45 degrees to the dash, would that make any difference in choice?

I totally know what you're saying about "no replacement for area", that's my intuitive starting point. In this case the car is a blank slate, but I'm trying to optimize across both performance and "stealth". I'm not going for SPL records or anything like that, just want good, full sound that you can't get with just 6.5" mids. 

Maybe an example of where I'm stuck would help. Here's WinISD plots for 4 subs, all are 25L sealed enclosures:
Red: Focal P20FSE (8" shallow)
Orange: Stevens SA10
Blue: AudioFrog GS8ND2
Magenta: AudioFrog GB12D2









I guess this is where my wires get crossed. By the chart, and given that max output isn't my goal, the Focal would seem like the clear winner....

Now I thought the problem was I wasn't taking sensitivity into account, here's the plot if I apply a static gain filter in WinISD based off the published sensitivities:









From that it still seems like the P20FSE would still be the best fit for my situation. I realize it wouldn't have the raw output of 10's or 12's, but since that's not really an issue for me it seems like the extra extension at the low end, being +4-5dB over GS8ND2 or SA10, would be of more benefit to me. I'm not sure I really want to give up the space for GB12's. At least as far as these particular options go. 

Wondering if I'm way off base here? And I'm sorry for taking this way OT from HLCDs.


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## oabeieo (Feb 22, 2015)

The p20fse is going to play flat to about 50hz, Sealed. 

Your room gain should start between 45-80hz (approximately) the fse may drop in the 50s or 40s but the car should boost below that and should net a pretty flat response…

All I’m saying is that driver in sealed is astonishing. Whimsy looking basket and magnet but huge clean output for its size…. 

All I’m saying is you’ll like that driver, it’s parameters are a bit different then most, don’t let that fool you. From your list of sub drivers , and as a horn user, you’ll like that sub. A lot.
I have t seen the SA10 yet tho , that might be better , I need to see one, so knowing stevens drivers , I bet it’s pretty hard to beat.


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## stanger89 (Jan 8, 2022)

Thanks for the first hand report, greatly appreciated. What size enclosure did you use? The spec sheet recommends 6-9L which would be great for minimizing the space, but I was calculating larger volumes in WinISD since it seems to flatten things out. Of course I realize I'll probably just have to try different sizes and see what I like.


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## oabeieo (Feb 22, 2015)

stanger89 said:


> Thanks for the first hand report, greatly appreciated. What size enclosure did you use? The spec sheet recommends 6-9L which would be great for minimizing the space, but I was calculating larger volumes in WinISD since it seems to flatten things out. Of course I realize I'll probably just have to try different sizes and see what I like.


I also used WINisd, I was a tiny bit more then recommended by focal. I think I was .8cuft net per. It wasn’t super big, it wasn’t tiny tiny tho however. Small enough tho.


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## stanger89 (Jan 8, 2022)

Cool, that's in the ballpark of what I was thinking too.


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## Eric Stevens (Dec 29, 2007)

I would still choose the FS but both will work with some small differences.


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## stanger89 (Jan 8, 2022)

Cool, I mocked something up in cardboard based off the pics in this thread, and it's a little tight, but almost like they were made for the application. Now I just need to get through everything else that needs to be done first, like, oh, getting the engine back in, some wiring in the car, etc


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## oabeieo (Feb 22, 2015)

stanger89 said:


> Cool, I mocked something up in cardboard based off the pics in this thread, and it's a little tight, but almost like they were made for the application. Now I just need to get through everything else that needs to be done first, like, oh, getting the engine back in, some wiring in the car, etc


can we see some pics of it ? 
sounds like a really cool build.


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## stanger89 (Jan 8, 2022)

Here ya go

Cardboard should be the size of a full horn. And no, the gas pedal isn't installed yet.









As you can probably see, I'll probably need to notch around the steering column, depends on how stuff lines up though.









Interestingly, factory kick speakers were actually an option on some of these cars. They were 5-1/4" and would have had a plastic pod. Well that obviously wasn't going to be good enough with the other work I'm doing, so I took a page from Detroit Speed's playbook and I cut holes for 6.5"s, and built my own pods/enclosures.










And then there's the planning debating for what subs, and where they should go. The rear deck is pretty good sized, 8's are easy. 10's might be possible. 


















I suppose the other option is to mount the subs "in" the bulkhead behind the rear seats. But for some reason I can't formulate, I don't necessarily want to have the subs fire through the seats. Regardless of which subs, I've got about 1.75 ft^3 or so back there (that's net with one of my current box configurations)t


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## oabeieo (Feb 22, 2015)

That thing is awesome, have you considered doing an IB setup ?

i truly love the Quality of this build, we’ll done. Amazing …… I love it


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## stanger89 (Jan 8, 2022)

I've sort of thought about IB, but maybe not seriously enough. What I don't want is to end up fighting trunk rattles, maybe I'm overthinking that though since my goal is reasonable sound levels and sound quality.

Hm... Might be able to fit 12's in the rear seat bulkhead, but depending on the rear seats I use, they've got a rigid frame. I've got the factory rear seat still, but I got a whole set of seats out of a 2017 Mustang (mainly for the fronts). That had fold down rear seats for a passthrough. Those could probably be modified though.

And thanks! I'm having a lot of fun with this, we'll see how it all comes together.


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## oabeieo (Feb 22, 2015)

yeah trunk rattles or any rattles from spl is from spl , not so much the box design or lack of box.

having an 8” mounted to the rear deck in boxes will give less rattles, the only thing I can think of is even though you want moderate volume levels, your front end will be able to get pretty rippin loud. Using a 6” midbass, I can see augmenting some of the response with a sub that is capable of sound quality with no ringing or artifacts.

your6.5s sealed like that will surely ring between 100-160hz and have a huge peak that will need to use eq and brought down. If you have a sub that if you crossed at 80 with a 4th order slope will still reach into the low 100s and blend with that 6.5

if your sub also has a box peak then you may have some colorations to the low midbass and could negatively affect your tilt. If your going for a really flat response what your doing should work just fine . If you want even a 1.5db tilt per octave under 300hz , I can see where a IB sub would definitely help with blending to the midbass.

the surface area of let’s say a pair of 12s compared to a pair of 8s is substantial, and even though you won’t use even 20% of most it’s usable capabilities, there may be a Neurofrequency band, that the sub could be used at full power to mitigate.

sub bass is nice, really good sub bass is just to die for. And with horns and how much output potential you will have, I can definitely see you using more than you think you are anticipating with road noise and just the sheer fun of being able to listen at moderate volume without any distortion or clipping


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## oabeieo (Feb 22, 2015)

You also have enough rear deck for 5 of the focal 8” it looks like IB would work maybe …. Man that would be something….. no ringing , that focal would perform well in IB, you were just need to control the excursion as that is not a very high excursion driver….., a simple 1st order HPF at about 26hz should do it approximately just guessing without measurements, and net you pretty flat response to DC. That and some eq cuts on the peaks which will be where most of your excursion is anyway.

that could be pretty cool also  with that high of a Q that focal would be an excellent sounding low output IB subwoofer.


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## stanger89 (Jan 8, 2022)

No doubt a pair of 12's is a ton more area than 8's, over double if I did the math in my head right, and no doubt that's valuable. Ironically the freedom I have with this blank slate is also a bit of a curse. With a more normal build, where the car was "complete" and I was just installing the audio, I'd be able to experiment, I could get a pair of 8's and try them, or 12's, see how I like it, maybe try the other. As it is, there won't be an interior, heck, there won't be glass in it  until well past all the heavy fabrication needs to be done. That, plus the time I've got to plan/make decisions, means I've got plenty of time to overthink things. Well, except I do need to decide things like what speakers and where before I call the fabrication done.

I totally get you on the subbass, I've got a pair of SVS PB12 NSDs in my HT, and it's great, to an extent it's sort of the reference I'm shooting for with the car. Flip side is, being a muscle car, it's far from an ideal listening environment, and heck with a nice V8 and dual exhaust, who'd want it to be  So the whole build is, I guess, balanced overkill.


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## oabeieo (Feb 22, 2015)

stanger89 said:


> No doubt a pair of 12's is a ton more area than 8's, over double if I did the math in my head right, and no doubt that's valuable. Ironically the freedom I have with this blank slate is also a bit of a curse. With a more normal build, where the car was "complete" and I was just installing the audio, I'd be able to experiment, I could get a pair of 8's and try them, or 12's, see how I like it, maybe try the other. As it is, there won't be an interior, heck, there won't be glass in it  until well past all the heavy fabrication needs to be done. That, plus the time I've got to plan/make decisions, means I've got plenty of time to overthink things. Well, except I do need to decide things like what speakers and where before I call the fabrication done.
> 
> I totally get you on the subbass, I've got a pair of SVS PB12 NSDs in my HT, and it's great, to an extent it's sort of the reference I'm shooting for with the car. Flip side is, being a muscle car, it's far from an ideal listening environment, and heck with a nice V8 and dual exhaust, who'd want it to be  So the whole build is, I guess, balanced overkill.


I’m pretty sure you’ll get it exactly right, looking at your extensive fab on that thing, you seem like your the kind of person that wants it done right first time.

it’s going to be so awesome. I have no doubt you won’t get it wrong.


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## dowheelies (Jan 7, 2012)

Very nice build you have going! I’m in the midst of a very similar ‘67 Mustang build. It was a bit further along when I got my mitts on it but not much. It’s now wired, running and driving. The interior and audio are the frontiers I’m trying to conquer now.

As far as rattles…. Previous owner used excessive dynamat extreme, pretty much 100% coverage on the entire floor, roof and doors. With 2 Alpine 8” Type R’s in a 1.4CF tuned to 37hz (I think have to check) and ~700 watts from JBL MS-A5001 firing through the rear seat bulkhead the rattles are definitely there still. Not so much the interior but surprisingly the trunk, undercarriage and under hood/grill etc. Going to tackle 1 by 1 what I can.

I considered IB, as like horns I always wanted to try. These cars look pretty easy at first glance to seal trunk to cabin, the trick will be above the wheel house to pillar/rear side panels. Pretty large complex shape cavern there on each side to truly seal up. Doable at your stage no doubt but considerable work.

Thank you so much for the front kick speaker info! I never noticed that stamped area as the fenders were on when I got it, sure enough I pulled the fender inner liner plate a voila! Stamped and even dimpled screw holes! My mind is now in overdrive, can I fit an Stevens MB-8 with enough airspace 

Keep up the progress and fine work, look forward to watching this one develope.

Eric


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## stanger89 (Jan 8, 2022)

oabeieo said:


> it’s going to be so awesome. I have no doubt you won’t get it wrong.


Yeah, I'm pretty sure it'll be great (one way or another), but the pace of progress gives me plenty of time to over think it 



dowheelies said:


> Very nice build you have going! I’m in the midst of a very similar ‘67 Mustang build. It was a bit further along when I got my mitts on it but not much. It’s now wired, running and driving. The interior and audio are the frontiers I’m trying to conquer now.


I'd had it in the plan to build a car, always wanted to do a 69 Fastback since I was a kid, but there's a ton of those, and not many Cougars, which have their own cool features like the hideaway headlights, sequential rear turn signals, and the headlight/taillight grills, plus they're like 6" longer so should be a bit more comfortable practical for road trips.

Anyway, this car popped up surprisingly close, and was a blank slate. Best guess from what I know of it's history is someone had started a restoration, but never finished. It was in primer when I got it, the shop had pictures of it in (mostly) bare metal from when they primed it, so I knew it was mostly rust-free. Though there were some surprises, like some really poorly done dent repair on the quarters. Ended up being easier to just replace the driver's side quarter than to patch the swiss cheese and bondo mess.

I took a welding class and got a welder so I could do as much myself as possible. There's an amazing custom shop in town here that does some really high end builds (unfortunately we don't have anything comparable for audio in the state) and are super friendly and helpful, but there's no way I could afford to have them do all the work. Builds like I'm trying to do are ridiculously expensive if you have "professionals" do it, but I know I can pull it off if I do everything I can and and utilize professionals for just the really specialized stuff (paint and interior basically).



> As far as rattles…. Previous owner used excessive dynamat extreme, pretty much 100% coverage on the entire floor, roof and doors. With 2 Alpine 8” Type R’s in a 1.4CF tuned to 37hz (I think have to check) and ~700 watts from JBL MS-A5001 firing through the rear seat bulkhead the rattles are definitely there still. Not so much the interior but surprisingly the trunk, undercarriage and under hood/grill etc. Going to tackle 1 by 1 what I can.


How do like the 8's? The simulations I've done lead me to believe I can get something that should work pretty well, but the only 8 I've heard is the factory one in my truck, which isn't tuned very good. As for sound treatments, I was looking at the Resonix stuff, I was pretty impressed by the technical writeup they've got, and Nick was pretty helpful when I emailed him.



> I considered IB, as like horns I always wanted to try. These cars look pretty easy at first glance to seal trunk to cabin, the trick will be above the wheel house to pillar/rear side panels. Pretty large complex shape cavern there on each side to truly seal up. Doable at your stage no doubt but considerable work.


Yeah, it would be no trivial matter to seal off the trunk for IB, and I'm not really keen on the idea of just using spray foam (at least not as I imagine it to seal off the quarter panels. I keep going back and forth, messing around with WinISD, the difference between Sealed and IB with those Focal P20FSEs is about 3-4dB @ 20Hz in favor of the IB. And most of the other subs I've modeled all seem to fall in the -8 to -12dB & 20Hz range, so within about 3-4dB or so, which seems to be within the realm of what you could even out with EQ, especially with cabin gain helping.

Actually the craziest thing I threw together in WinISD is a ported box with the P20FSE, .7ft^3 tuned to 25Hz. That's actually only ~-1dB @ 20Hz, though it falls off like a rock after that, but doesn't drop below the sealed/IB options until about 15Hz.



> Thank you so much for the front kick speaker info! I never noticed that stamped area as the fenders were on when I got it, sure enough I pulled the fender inner liner plate a voila! Stamped and even dimpled screw holes! My mind is now in overdrive, can I fit an Stevens MB-8 with enough airspace


This is what actually started me down the that path, realizing it was an option:








Kick Panel - Stereo Speaker Enclosures / Pods - PAIR - Repro ~ 1967 - 1968 Mercury Cougar / Ford Torino


These were installed behind the kick panels on 1967-68 Cougars & 1968-69 Fairlanes, Torinos, and Cyclones equipped with a factory AM-FM or AM-8 track radio. Easy to install...




secure.cougarpartscatalog.com




"These were installed behind the kick panels on 1967-68 Cougars & the 1968-69 Fairlane, Torino, Cobra and Cyclone equipped with a factory AM-FM or AM-8 track radio."

Then since I put a DSE suspension in it, I've been following their work. They did the fab'd metal pods on a 66 they did, which gave me the idea to do that. I know it's not ideal, but it seems like a better compromise than normal kick panels (at least from an aesthetic/stealth perspective, or trying to put them in the doors. Plus it's a nod to a factory option which is cool.

Here's the 66 they did, it's been a huge inspiration, and a ton of help. It's also where I got the idea to put a late model Cobra tunnel in to make room for the transmission.








Chris' 1966 Mustang


Explore this photo album by Detroit Speed & Engineering on Flickr!




www.flickr.com


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## oabeieo (Feb 22, 2015)

That mustang is titts, what a beautiful car. 
can’t wait to see the cougar. I love builds like this. Ain’t no _good from far-far from good _. This is a real restore, love seeing horns go in.


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## oabeieo (Feb 22, 2015)

Patiently wait for more pics….. any more news on this one?


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## stanger89 (Jan 8, 2022)

Nothing audio wise. Ended up replacing the taillight panels, there was some minor damage there from some sort of collision (maybe fell off a jack stand and into something at some point?) and it was way easier faster to replace the panels than to try and straighten it out. Then getting the Control Pack (ECU/harness) installed and routed, which is tricky to do neatly with the length constraints of the harnesses. Also been making some radiator mounts since I'm not using the stock radiator. I keep thinking I'm about done with fabrication, but then, well, I'm not, . 

So, making progress, but the audio stuff is still going to be a while still.


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## oabeieo (Feb 22, 2015)

stanger89 said:


> Nothing audio wise. Ended up replacing the taillight panels, there was some minor damage there from some sort of collision (maybe fell off a jack stand and into something at some point?) and it was way easier faster to replace the panels than to try and straighten it out. Then getting the Control Pack (ECU/harness) installed and routed, which is tricky to do neatly with the length constraints of the harnesses. Also been making some radiator mounts since I'm not using the stock radiator. I keep thinking I'm about done with fabrication, but then, well, I'm not, .
> 
> So, making progress, but the audio stuff is still going to be a while still.


awe dang it !!! Lol 🙂

okay well please keep us posted. It’s going to be really sweet.


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## stanger89 (Jan 8, 2022)

Yeah, in some sense I really jumped the gun on getting into the audio stuff. Though at the same time, there's definitely going to be fab involved, like the front mid enclosures and the rear deck for subs, so I don't want to wait too long on those.


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## stanger89 (Jan 8, 2022)

Speaking of audio... 

I'm not sure why this didn't register as a good option before now, and I know I'd read about this, even saw a video from CAF the other day of a (new) Mustang JL Audio was showing. What they did was a "normal"-ish box with the subs in the trunk below the rear deck, but blocked off from the trunk, and guided through a port in the rear deck. I guess the dots that just connected is the Cougar had a provision for a rear defrost module in the rear deck, so there's already a hole there, and a grill wouldn't be out of place.

So wondering:
Is that hole big enough, looks like it's ~7" square (49 in^2)?
How do you "focus" the sound to go through that port rather than filling the trunk?
Are there design parameters/rules of thumb so that doing this doesn't end up as a bandpass box?


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## Eric Stevens (Dec 29, 2007)

If you keep the area small or smallish in front of the woofers before the opening and keep the opening short it wont act like a bandpass. I recommend at least 1/2 of the cone area measured at the center of the surround so you would be good for subwoofers with a cone are of 100 sq in. (note this can be pushed a bit before there is any effects on performance. Dont need to guide the output it is a pressure wave so it will just come out.


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## oabeieo (Feb 22, 2015)

And Make sure you seal that ***** off. Lol

don’t want it to sound like a 6 inch speaker in a 10 inch hole 🙈

I’ve done a few of those port Throughs, sometimes you don’t have to seal them off but sometimes you do.

it’s like the SPL gets stuck in the trunk and wants to find its way back into the trunk

and the totally weird thing about cars that do that is when you open the trunk the bass just to the front and it sounds super good in the front seat and has lots of spl ….(but nobody wants to drive around with their trunk open) ha! 😒… I have no idea what causes it I’ve suspected trunk vents, but have no clue. It’s weird 

so just make sure it’s super sealed off and you should be good to go

and I also includes the pathway behind the backseat… that will need to be sealed off completely as well

# freakish acoustics


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## stanger89 (Jan 8, 2022)

Thanks, I'll have to think about this some more (got plenty of time I guess ). Good to know it could work. I was thinking it might open up my options a bit (larger subs), but the more I think about it, like the design constraints of making it installable with geometry in there, I might be better off just going with plan A of 8's directly through the rear deck in a box mounted underneath. I'll probably have to sketch something up and see how it looks.


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## stanger89 (Jan 8, 2022)

Just threw this together in Fusion as sort of a concept of what I was thinking. I think I'd probably have to open up hole a bit for the size of the woofers. Thought is at least part of the back (side we're looking at) would be acrylic, the top board is to seal off from the trunk. But the more I think about this, and even trying to run the subs through the rear deck (box mounted under), the more I wonder if this whole thing won't work without rather extreme work to seal off the trunk from the cabin. Maybe I should just go with a normal, rear-firing box in the same space.


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## oabeieo (Feb 22, 2015)

stanger89 said:


> Just threw this together in Fusion as sort of a concept of what I was thinking. I think I'd probably have to open up hole a bit for the size of the woofers. Thought is at least part of the back (side we're looking at) would be acrylic, the top board is to seal off from the trunk. But the more I think about this, and even trying to run the subs through the rear deck (box mounted under), the more I wonder if this whole thing won't work without rather extreme work to seal off the trunk from the cabin. Maybe I should just go with a normal, rear-firing box in the same space.
> 
> View attachment 331678


that will act like a single reflex bandpass, tuned high (A three-quarter inch long port the side of mdf) but that’s not a bad thing!!! The port being that short will be out of band your active filter will be the majority of its filtering.

you’ll have to plot it out. it will affect the impedance of the system, but I don’t think it’s going to be affected negatively…. In fact you might get some gain.

GD be out of band, your active filter should push it most of the way out, but it still will be affected but nothing simple signal delay can’t fix.

it might drop off a little early at the very bottom end also, like 20-35hz ish area (that’s very dependent on the size of the back chamber and the speaker you’re using) Again you’ll want to plot it as a bandpass and see what it looks like

it will be punchy as hell and play low also….. 

what I really like about the design is that they’re really punchy, they don’t have gobs of group delay, and even though they don’t play as low. You can add a Linkwitz transform and get it back very easily (at the cost of maybe 2db of efficiency) you’re just eliminating the efficiency gain of it being a bandpass . And you feel the bass a lot!

you’ll probably notice it’s gonna be tuned around 150 or 250 Hz or something way out of band. you got a remember that’s the high side. having it above your active filter is a good thing. you’re not trying to get efficiency in the passband. you’re only trying to replicate a seal box. It will just have a little bit of upper harmonics ringing but it will not sound bad…

you could line the inside of the front side with some foam and it will negate some of the ringing. but it also could cause some whistling at the port if velocities get too high… it looks like that is a three-quarter inch long port. I would actually make it about 2 inches long that will reduce some of the whistling. Only because the top of the inside of the box is flat edged to the opening.

having a drop down into the box by even just 1 inch will make the air move more evenly out the port instead of the air wanting to move faster out of the edge of the port.

any residual group delay that’s out of band can simply be corrected with some signal delay…
Meaning you can add one or 2 ms additional to all of the interior speakers delaying them against the sub box which would effectively pull back phase of the sub system…. You’ll have to take some measurements when you get there and see how things line up.

it’s really nothing to be concerned about it looks like it will work really nice…. but again I would still plot it as a single reflex tuned super high.


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## stanger89 (Jan 8, 2022)

Yeah, I was playing around a bit with the design in WinISD. I didn't see a way to tweak the port length but I was messing with the tuning frequency to get an approximate length, ended up with a tuning frequency of ~300Hz.

So what about sealing, would this sort of thing require sealing off the trunk? Or since the box contains everything except the port, does that make it so I don't need to worry about filtering/cancellation from the pressure being able to get into the trunk?


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## oabeieo (Feb 22, 2015)

stanger89 said:


> Yeah, I was playing around a bit with the design in WinISD. I didn't see a way to tweak the port length but I was messing with the tuning frequency to get an approximate length, ended up with a tuning frequency of ~300Hz.
> 
> So what about sealing, would this sort of thing require sealing off the trunk? Or since the box contains everything except the port, does that make it so I don't need to worry about filtering/cancellation from the pressure being able to get into the trunk?


yea 300hz tuning will work just fine
Your active filter will be way below that….
it’s just going to have a lot of gain at 300hz….. which equates to a very punchy sound with an 80hz crossover….. you’ll dig it 

the low side maybe an f3 around 50 or so would good, as long as it’s below 65 you’ll still have decent efficiency…

and yeah like I said about the sealing thing, I would build it and throw it in there and see what it does first…. And not worry about sealing it off because the acoystic‘s are so freaky you just cannot predict it. But if the SPL is so low and then you open the trunk and all of a sudden it’s bumpin good, then you know you’re gonna have to spend considerable time tunneling that into the cabin, and sealing off the trunk completely.
Then you should have adequate SPL upfront


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## Eric Stevens (Dec 29, 2007)

I prefer to seal it off and take the trunk out of the equation. The volume in the trunk will act like a large helmholz resonator which can really affect the response. you could try without just in case its a good option, but pretty certain sealed off is the better option.


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## oabeieo (Feb 22, 2015)

Never thought about it like that Eric, 

I’ve been thinking of the function and you just described it perfectly…. Thank you!


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## stanger89 (Jan 8, 2022)

Eric Stevens said:


> I prefer to seal it off and take the trunk out of the equation. The volume in the trunk will act like a large helmholz resonator which can really affect the response. you could try without just in case its a good option, but pretty certain sealed off is the better option.


Yeah, that's what I've been reading, and why I'm wondering if just a regular rear-firing (into the trunk) setup would be "best". Part of the trick is I'm not really sure of the process for getting the interior done, I may not really have an interior in before I have to do things like get the sub box built/installed. So it's really not going to be practical to try it and see, since I'm really not going to want to pull out a custom interior to seal off the trunk. Tied to that, sealing off the trunk in some sort of "elegant" way (not just spray expanding foam into the quarter panel) is kind of an enormous task (though admittedly, now would be the time to do it).

I should probably add, one of my original goals was to keep the sub box from intruding into the trunk too much, which is why I sort of got hung up on putting the subs in the deck in the first place. But since I've been drawing up boxes and looking at options, I've realized that with the new rear crossmember, the space between that and the rear deck is somewhat "wasted space" anyway, so filling that with a box doesn't really lose me any practical cargo space.


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## Eric Stevens (Dec 29, 2007)

Firing up into the rear deck sealed into the passenger compartment is much better than firing into the trunk and then finding its way into the interior. There is no negative with sealing it off.


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## stanger89 (Jan 8, 2022)

Eric Stevens said:


> Firing up into the rear deck sealed into the passenger compartment is much better than firing into the trunk and then finding its way into the interior.


Good to know.



> There is no negative with sealing it off.


Except the work 

I'll have to take a look and see what my options are.


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## oabeieo (Feb 22, 2015)

All I know is it’s going to be awesome !!!!

get to work! I can’t wait to see more


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## stanger89 (Jan 8, 2022)

Ok Mike Patey 

You know it's kind of interesting how much of a difference a slight change in perspective can make. I kept thinking "gotta seal off the trunk from the cabin, how am I going to do that, how would I fabricate a "firewall" between the inner and outer quarter panels, and how would I get it in there.










The shapes, the access, it would be a nightmare to first fabricate something to fit in there, and then to figure out how to install it and seal it.

But then after I replied last, somehow my perspective changed, and I thought, I don't have to seal the trunk from the cabin, but the cabin from the trunk. Now technically it's a very slight (if any) difference, but when you look at the car from inside the cabin, and how to seal that barrier, it looks a lot more doable.









The rear deck is already taken care of with the sub box, and maybe make an enclosure around the 6x9's if I install any. I already have a rear bulkhead made up to stiffen the car (instead of the two braces that were already broken loose when I got the car). After that, while it is quite a few holes, it's "just" flat holes to fill. Those are easy with some sort of block off plates that can be just screwed/bolted or bonded in. I've seen plenty of that done in car doors. That seems very doable.

But that'll probably wait until after I finish the plumbing and wiring 😓


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## Eric Stevens (Dec 29, 2007)

Sealing those areas off is done by stuffing them very densly. Dont use Spray foam it will deform panels. I have used old towels and sheets to test and ended up using them in certain areas because they worked great. Does not have to be a rigid baffle just needs to block the rear wave.


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## oabeieo (Feb 22, 2015)

Haha! Now your thinkin!
Some expansion foam (ouch on a mint chassis) haha

But yeah your paneling and some even mild cld around it would be awesome along with some towels like eric said , as a barrier to the pressure and some cld around your panels as a finish …. Nothing damaged on that chassis

One time I plugged a port with a towel, guess what; it worked. And it wasn’t super tight
no air escaped , didn’t act A-periodical at all


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## stanger89 (Jan 8, 2022)

OK, sending up the bat signal....

Not directly related to this, but I've been trying to tune/wring out the system in my Mustang that I've been fighting with for quite a long time. I've documented that over here if anyone wants to take a look: Mustang Active 2-way Tune Help (Fighting Sibilance)

I mention it here mainly because I'm treating it as sort of a trial run/proof of concept, to see how good I can get a system set up, and find out if it's going to be worth going to a fair bit of trouble and money into the Cougar. (Beyond I want to get the Mustang sorted out in it's own right).


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## Eric Stevens (Dec 29, 2007)

stanger89 said:


> OK, sending up the bat signal....
> 
> Not directly related to this, but I've been trying to tune/wring out the system in my Mustang that I've been fighting with for quite a long time. I've documented that over here if anyone wants to take a look: Mustang Active 2-way Tune Help (Fighting Sibilance)
> 
> I mention it here mainly because I'm treating it as sort of a trial run/proof of concept, to see how good I can get a system set up, and find out if it's going to be worth going to a fair bit of trouble and money into the Cougar. (Beyond I want to get the Mustang sorted out in it's own right).


Brightness or sibilance can be driver related and / or installation / tuning, along with environment related issues like reflections etc.. Comb filtering with mids and tweeters mounted up high can cause this in a big way, crossover settings also. 

To see if its driver or environment you can measure near field and compare the two. 

forwardness is 2k to 4k sibilance is 5 k to 8 k


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## stanger89 (Jan 8, 2022)

Thanks, I was out this morning with the o-scope and had it hooked up, tapped into the input of the amp and the output, and there's something more fundamental wrong in my install. There's got to be something really basic I did wrong or has gone wrong. I've got to go back out again this afternoon and dig in some more.


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## stanger89 (Jan 8, 2022)

I went back to square one, reset everything and I think I resolved the setup issue causing the "painful" sound. But looking at all my measurements, one thing that sticks out is in that car (89 Mustang) I've got a huge null at 1kHz. The question for this thread, HLCD related, if I have a similar issue in the Cougar, what does that mean for HLCDs. I've been reading a bunch and watching quite a few tuning videos, and one thing I'm noticing is that, lets just say a common way to deal with some of these issues is to go 3-way. A specific example is the AudioFrog tuning guide, it's got a section/chart discussing the issues of trying to get a 2-way system, especially one with 6.5" woofers to have a smooth response due to the tendency of the larger speakers to beam at higher frequencies. It suggests a hypothetical system with a 6" woofer crossed at about 500Hz, tweeter crossed at 5kHz and 2.5" mid to cover the gap.

Maybe I'll put it this way, if I were to try to add large horns to the Mustang, with that huge dip at 1kHz would it work to cross them at or below 1kHz (I think I remember reading the large horns work down to 800 or 900Hz?).

Thanks


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## Eric Stevens (Dec 29, 2007)

stanger89 said:


> I went back to square one, reset everything and I think I resolved the setup issue causing the "painful" sound. But looking at all my measurements, one thing that sticks out is in that car (89 Mustang) I've got a huge null at 1kHz. The question for this thread, HLCD related, if I have a similar issue in the Cougar, what does that mean for HLCDs. I've been reading a bunch and watching quite a few tuning videos, and one thing I'm noticing is that, lets just say a common way to deal with some of these issues is to go 3-way. A specific example is the AudioFrog tuning guide, it's got a section/chart discussing the issues of trying to get a 2-way system, especially one with 6.5" woofers to have a smooth response due to the tendency of the larger speakers to beam at higher frequencies. It suggests a hypothetical system with a 6" woofer crossed at about 500Hz, tweeter crossed at 5kHz and 2.5" mid to cover the gap.
> 
> Maybe I'll put it this way, if I were to try to add large horns to the Mustang, with that huge dip at 1kHz would it work to cross them at or below 1kHz (I think I remember reading the large horns work down to 800 or 900Hz?).
> 
> Thanks


Most vehicles have an issue in the 500 to 600 hz range and its best to just leave it alone and not worry about it.

I doubt you have a null or cancellation at 1khz, possibly a measurement technique issue or driver specific issue. In all my years of measuring cars most have a rise in the response in this area. Even beaming of a 6.5" isnt a real issue to well above 1500 Hz and in my experience with a typical midsize car appilication even at 2500 it is not enough of an issue to have an effect on the results.

With HLCD you will not have an issue.


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## stanger89 (Jan 8, 2022)

I'll have to try and measure the drivers up close to try and isolate it from the car and see if it shows up there too. For reference, here's the measurements of the mids I took a while ago. Each is the average (by REW) of 5 positions, center and about 4-6" left/right/front/back.









Drivers are Morel Tempo Ultra 6.5's. Microphone is a UMIK-1.



Eric Stevens said:


> With HLCD you will not have an issue.




Now I've just got to get to the audio system portion of building the Cougar.


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## Eric Stevens (Dec 29, 2007)

Noise type (pink noise, burst, or sweep) and measuring one side in isolation will have an effect also. Pink noise because its random produces the best results, sweep based measurements are only useful for trying isolate a specific problem, burst is good but you need to take many and average and smooth. 

For tuning a system I like using pink noise with and RTA and doing 10 second averages while moving the microphone in a figure 8 pattern the size of your head in the listening position.

taking near field measurements can tell if its a driver/install issue or an environment issue.




stanger89 said:


> I'll have to try and measure the drivers up close to try and isolate it from the car and see if it shows up there too. For reference, here's the measurements of the mids I took a while ago. Each is the average (by REW) of 5 positions, center and about 4-6" left/right/front/back.


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## stanger89 (Jan 8, 2022)

Thanks gain.

Back on the Cougar topic, I was thinking and did some measuring, I'm wondering if the side of the trunk "inside" the driver's quarter panel might be a better solution. I've got a bit over 1 cubic foot net volume there (I drew up an enclosure quick to figure out the net volume). And with the depth and frontal area, I could easily fit a 10", or even a 12" sub in there.


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## oabeieo (Feb 22, 2015)

yeah if you dames the trunk and so rattles are minimized it could be ok 

probably not enough for a sq+ system but should fill in lows (and nothing more then a fill) but will work


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## stanger89 (Jan 8, 2022)

Just thinking options, sounds like the rear deck is still the way to go.


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## oabeieo (Feb 22, 2015)

stanger89 said:


> Just thinking options, sounds like the rear deck is still the way to go.


If your after substantial output yes , and arguably less rattles 

a sub in trunk can still be pretty good , would be plenty for me , but I’m not everybody


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## stanger89 (Jan 8, 2022)

Definitely not after crazy output, just looking to fill in below what 6.5" mids can do, and do it well ("SQ"). Side of the trunk might be "slightly" easier to build but would utilize mostly unusable space. Under the deck isn't super usable either, but more so than the side. Building wise the main downside of the side of the trunk is I'd have to fabricate/weld in supports for the box. Though I'd have to come up with something to put it under the deck too.

I'm getting a little closer to having to make a decision, I finally ordered the bulk of the main power wiring for the car. The trick is my current plan has the interior being the very last thing to get installed so I really want to nail down anything that requires (metal) fabrication before I take it apart again for pain. i.e. fabrication->system check->disassemble->paint->(sound deadening)->interior


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## oabeieo (Feb 22, 2015)

I can’t wait to see it ……


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## stanger89 (Jan 8, 2022)

You're going to have to


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