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I'm close to throwing the towel in on infinite baffle...

28K views 513 replies 31 participants last post by  KFXGUY 
#1 ·
I'm getting flustered, Just when I think I have it dialed in, I'll listen to a song that I know has bass, but i can barely hear it. I'll turn up the level....and it doesnt get any louder, just sounds like crap.
The 4 6.5" flutes almost do it for me on their own, but some songs just need the extra hit of subs. Especially when i have the windows rolled down. I have some ideas on what i want to try, but wanted to see what you guys think would be my better choice...

(equipment is pioneer 1500nex headunit, punch 4x100 and 1x750 amps, dayton DSP-LP for the subs, (2) 8" audiophile subs, (4) 6.5" silverflutes, Whispers in the dash along with some dayton AMT tweets, 2004 GTO)

SO heres my thoughts.... I could order a set of cerwin vega 8's and a set of kicker comp C 8's and see what sounds better, hate to do it but amazon has a great return policy so i could test both. Maybe I'll get lucky. I was also planning on trying the tangband w6 6.5" subs i have since i added that LP dsp AND trying the blaupunkt 8's I had in there also. Since then i've sealed and deadened the trunk much better and the dsp-LP helps too. OR>>>>>>>>>>>>>

I could get a set of 8" flutes for the back deck and add those on the rear channels with the rear 6.5" flutes in the side panels and then just bite the bullet and put my sub in the box back in the trunk. Or I could do the same with the tangband 6.5's or even the blaupunkts. That will give me a little more accurate "kick" inside the car and use the box sub for like 80hz and below.
Or...I could use the factory amp on the rear deck speakers and still add my sub back in. I'm just more or less brain storming. I may get a wild hair this evening and pull the back seat and deck out and start swapping speakers. I dunno...I'm just getting aggravated because its just not what I want yet.
 
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#2 · (Edited)
How well is the front and back wave separated? Do you have the rear seats, and the rear deck baffled?

Swapping 8" subs will most likely just add to your frustration, similar sized subs will have similar output, you shouldn't expect a different pair of the same sized subs to have drastically different output. Sure, there may be a pair that out perform the others, but I wouldn't expect it to be by much, and the trial and error that it will take to find out may leave you even more frustrated.

Do you know anybody close by that can come check it out, maybe someone with a microphone and REW? It's tough to suggest fixes without knowing where the problem is, but as I said before I wouldn't expect drastically different results unless you step up to much more displacement. Most people would say that a pair of 8's IB won't cut it, I ran a pair of 15's and although I didn't need to push them very hard, I can't imagine 8's being satisfying.
 
#5 ·
How well is the front and back wave separated? Do you have the rear seats, and the rear deck baffled?

Swapping 8" subs will most likely just add to your frustration, similar sized subs will have similar output, you shouldn't expect a different pair of the same sized subs to have drastically different output. Sure, there may be a pair that out perform the others, but I wouldn't expect it to be by much, and the trial and error that it will take to find out may leave you even more frustrated.

Do you know anybody close by that can come check it out, maybe someone with a microphone and REW? It's tough to suggest fixes without knowing where the problem is, but as I said before I wouldn't expect drastically different results unless you step up to much more displacement. Most people would say that a pair of 8's IB won't cut it, I ran a pair of 15's and although I didn't need to push them very hard, I can't imagine 8's being satisfying.
Well the car has a metal fire wall separating the seat and the trunk because of a gas tank. Then I used dynamat all over to seal off the holes. Most holes have dynamat on the cabin side and truck side to serve as double thickness on the holes.
the 8’s have enough output for me. The problem is the current 8’s I have get silent below 30hz, peak by about 15db more at 40hz then get quiet again around 100hz with dips in volume around 50-60hz. I used the dsp to compensate but I just think these subs aren’t doing it. The Blaupunkts propped lower, cleaner and went higher. But the 40hz peak (cabin gain?) caused them to bottom badly before I had the dsp to control that. I’ve yet to try them again, but I need to.
 
#3 ·
My output increased with a third of the power when I went IB. Don't get me wrong the high end cut had to be lowered considerably but the low end increased noticably.

I'm with Gijoe. You may have cancellation or lost output at certain frequencies do to a flexing baffle or the front and rear waves interacting.
 
#4 ·
Where are your IB subs located, in the rear deck?

I have a 2005 GTO, and am having a hard time visualizing where you have subs mounted in an IB config with the fuel tank in the way.

BTW: I'm finally getting my car to sound great, just with front components and a sub box in the trunk. No rear side speakers, and no rear deck speakers. I did do a LOT of sound treatment though.
 
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#6 ·
in the rear deck. I did a lot of deadening too. The interior speakers sound great, it’s just the subs don’t sound right. Not enough frequency spread to them. (Note, this isn’t the deadening I have now. I pulled that out and used better stuff and did a better job).

Motor vehicle Car Hood Automotive tire Automotive lighting
 
#7 ·
I really don't think you're going to get anything below 30hz from a pair of 8's. Low frequencies require big displacement. We aren't very sensitive to frequencies that low so they need to be loud in order to be perceived as the same volume as the higher frequencies.

Cabin gain will not cause the subs to bottom out, cabin gain is "free" output. The vehicles interior reinforces certain frequencies, so the speaker actually works less to produce those frequencies.
 
#10 ·
I really don't think you're going to get anything below 30hz from a pair of 8's. Low frequencies require big displacement. We aren't very sensitive to frequencies that low so they need to be loud in order to be perceived as the same volume as the higher frequencies.

Cabin gain will not cause the subs to bottom out, cabin gain is "free" output. The vehicles interior reinforces certain frequencies, so the speaker actually works less to produce those frequencies.
I misunderstood what "cabin gain" meant. At 40hz, with all subs i've tried so far, the output if far greater than other frequencies and without a way to pull some volume from that particular frequency, all the subs i tried will rattle and bottom out. The blau's actually sounded good below 30hz but the 40hz rattle ould be unbearable if I turned it up. Now that i can control that, they may work out better.
 
#9 ·
I tried 6.5" Tang Band subs in that location, and was never satisfied with them. When I treated the interior, I put CLD tiles on the rear wall, and then hung MLV over it as well. I left the 6.5" holes in the rear deck open, but put a 6.5" round, 4" thick piece of OCF in there, along with a 1/4" piece of CCF on top. So the high frequency noise of the fuel pump is blocked, but low frequencies can pass.

Then I just dropped in the Rockford P300-12 unit, and it's been great! I have it crossed over at 63hHz, and my door speakers (Hertz 6.5" mids) crossed over at 80Hz. The sound is very well balanced, and imaged out onto the hood ... and the bass is perfect. My trunk space is significantly compromised though ... which I assume you are trying to avoid?


If you happen to be somewhere near Central Texas, I'd be happy to let you listen?

These cars are definitely a pain to figure out, and I'm doubtful you'll ever be satisfied with an IB setup in the rear deck.

For those who don't know, here is what it looks like under the rear deck. This pic was taken when I still had the 6.5" Tang Band woofers in place ... and I had to trim the fuel tank strap a bit for them to clear. Yes, that large black plastic thing is the cover over the fuel tank.

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Here's what it looks like on the inside, with the seat cushions removed

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I did CLD:

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And MLV:

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And I'm still not sure an IB setup would work ... there are more holes on the sides, where the wheel wells are, which extend into the trunk area. I used these to pass signal and power cables through.

But for an IB setup, they would all have to be damped and air sealed. I don't think CLD alone (ie: Dynamat) is enough to seal it off completely.
 
#12 ·
I tried 6.5" Tang Band subs in that location, and was never satisfied with them. When I treated the interior, I put CLD tiles on the rear wall, and then hung MLV over it as well. I left the 6.5" holes in the rear deck open, but put a 6.5" round, 4" thick piece of OCF in there, along with a 1/4" piece of CCF on top. So the high frequency noise of the fuel pump is blocked, but low frequencies can pass.

Then I just dropped in the Rockford P300-12 unit, and it's been great! I have it crossed over at 63hHz, and my door speakers (Hertz 6.5" mids) crossed over at 80Hz. The sound is very well balanced, and imaged out onto the hood ... and the bass is perfect. My trunk space is significantly compromised though ... which I assume you are trying to avoid?


If you happen to be somewhere near Central Texas, I'd be happy to let you listen?

These cars are definitely a pain to figure out, and I'm doubtful you'll ever be satisfied with an IB setup in the rear deck.

For those who don't know, here is what it looks like under the rear deck. This pic was taken when I still had the 6.5" Tang Band woofers in place ... and I had to trim the fuel tank strap a bit for them to clear. Yes, that large black plastic thing is the cover over the fuel tank.

View attachment 310767

Here's what it looks like on the inside, with the seat cushions removed

View attachment 310768

I did CLD:

View attachment 310769

And MLV:

View attachment 310770

And I'm still not sure an IB setup would work ... there are more holes on the sides, where the wheel wells are, which extend into the trunk area. I used these to pass signal and power cables through.

But for an IB setup, they would all have to be damped and air sealed. I don't think CLD alone (ie: Dynamat) is enough to seal it off completely.


I'm glad you posted those pics! Lets everyone see what I'm dealing with. I did seal off all of the areas in the trunk including the big crevices' in the 1/4 panels that lead up behind the real panel speakers. I have more deadener on mine tho, I pretty much left no meatal surfaces uncovered. What exactly did you use to block out the fuel pump noise? I was thinking passive radiators or leave the speaker holes open and put sound deadener INSIDE the plastic casing on the fuel tank. I have two aeromotive 340's in my tank.....
 
#13 ·
You will always want more from your ib 8s man.
You need more cone area for ib
For reference a popular sub on here is the sql 12.
In a sealed box with 1500 watts guys are happy.
The 2 8s have about the same amount of cone area.
Ib has limited output compared to sealed.
So you want to much man.
I have a ported 6.5 in the passenger foot well of a 19 kia rio and it sounds decent.
So maybe try that man.
 
#16 ·
+1000 to what MiniSQ said.

A single 15 in IB is my favorite sub setup. What's with the rectangular sheet metal spot dead center in the rear fire wall? Can that be replaced with a 1.5" thick plywood baffle for a 12 or 15? Or is there something lurking there?

8s are for midbass, unless you're driving a tiny hatchback like a Fit or Yaris.

Bigger sub equals lower bass. Especially free air/I.B.

Two 10s might work, if you can get them to squeeze in the rear deck, but in IB setups, I'm not a fan of the cones facing up in a rear deck. They have no rear spring aside from the suspension of the woofer. They are gonna fight themselves in a rear deck. Even tiny little 8s.
 
#37 ·
Maybe I missed it, but I dont see anything here about a SS filter. With only 2 8in subs for your sub-stage you don't have nearly enough displacement for anything below 40hz with any sort of authority.
So you are probably distorting them to death and running them hard into xmax when you touch your gain knob.
You have no sort of air spring on the cone. So it wants to move like crazy. Unless you limit that, it's going to sound rough at high volumes if there is any sub 40hz content in the music you are listening to.
If you want to run IB and not make an enclosure for them, your gonna have to fab something up for larger drivers with more displacement imo.
 
#38 ·
So I just got through taking it all apart again. I yanked one of the audiophile subs out and replaced it with a Blaupunkt. Did some swapping back and forth testing. Now I see why I took the Blaupunkts out. No matter what, they bottom too easy. Even with all the deadening and sealing I did. And the dsp. Dont matter. The audiophile subs pretty much trounce them. I’m leaving my interior apart and order a few other subs to try. No point in trying the 6.5’s I have because I remember the Blaupunkts beat those. I think I’m gonna order some cerwin Vega Vegas to try and some kicker comp c’s. I may order one of each. Skar has an 8” sub so I may order that too. I’m determined to make this work. I dunno why. I guess I’m seeing it as a challenge at this point.
 
#41 ·
Man....stop wasting your money. All of the subs you just mentioned have about the same SD and xmax. So just physically speaking they will all sound the same.
Except for the kicker comp. That might be the worst sub kicker has ever sold.
If printed a better bracket and used 10 inch subs it would be much better suited.
You said you might cut the back deck to open it up a little? Cut it. Print better adapters and problems solved.
 
#39 ·
Think of it in terms of displacement alone. You have four 6.5in mids, each of them has a cone area of 132cm each. Then you have two 8 in subs with a cone area of roughly 216cm each. You have 18% more cone area with your mids than you do with your subs. So it's not a surprise your mids are giving you nearly what you want and the subs are underwhelming.
132 x 4 = 528cm vs 216 x 2 = 432cm

That doesn't take into account linear travel, but even if your subs have 2x the xmax of your mids, that's still only 60% more air moved at xmax.
With have the same SPL level at one octave lower, you need to move 4x the amount of air.
So if you wanted to be able to match the spl capability of your mids running at 80hz @ xmax w/ 528cm, you would need to be displacing 2112cm. Drop that down to 30hz and you need 4224cm displaced. That also doesn't take into account the rise in the lower octave that is typically wanted.
Moral of the story, if you want to keep up with the 4 6.5in mids, you need to displace much more air than two 8in subs will provide when running in IB without a SS filter in place.
 
#43 ·
Think of it in terms of displacement alone. You have four 6.5in mids, each of them has a cone area of 132cm each. Then you have two 8 in subs with a cone area of roughly 216cm each. You have 18% more cone area with your mids than you do with your subs. So it's not a surprise your mids are giving you nearly what you want and the subs are underwhelming.
132 x 4 = 528cm vs 216 x 2 = 432cm

That doesn't take into account linear travel, but even if your subs have 2x the xmax of your mids, that's still only 60% more air moved at xmax.
With have the same SPL level at one octave lower, you need to move 4x the amount of air.
So if you wanted to be able to match the spl capability of your mids running at 80hz @ xmax w/ 528cm, you would need to be displacing 2112cm. Drop that down to 30hz and you need 4224cm displaced. That also doesn't take into account the rise in the lower octave that is typically wanted.
Moral of the story, if you want to keep up with the 4 6.5in mids, you need to displace much more air than two 8in subs will provide when running in IB without a SS filter in place.
Maybe you are right when you are talking about just the total air displacement, considering just spl, but one larger speaker with more cone area than two smaller speakers with drop lower. For example, two 8” subs displace 50.24 square inches of cone area whereas a single 15” sub has 47.1” of cone area but we all know that the 15” is going to catch a lower note much easier. This isn’t about just overall spl. I want good sound over a wider range of frequencies. I know two 8’s can do what I want, I just haven’t found the right driver yet. I’ve only tried two anyways. The bad thing about this is I can’t change the volume of the trunk (think changing box design or size) to change the sound, so I’m having to try different drivers. I keep seeing you guys keep harping on bigger subs, bigger subs....I get it. But it’s not an option. I don’t have the room in the deck for it. Or the depth. I wish I did because this would be much easier.
 
#54 ·
#49 ·
I will say this one last time before I give up.
If you want to have more low end than your 4 6in speakers will provide, 2 8in subs will NOT give you what you are looking for in IB. If you want response below 40hz at a reasonable SPL, you plain and simple need more cone area or you need to go to a higher order enclosure like ported or a bandpass.
If you are fine with +45hz, than a subsonic filter at 40hz and more power MAY give you what you are after.
 
#60 ·
He's talking about opening up the hole in the sheet metal, since it's barely large enough to allow the magnet to fit through.

Hood Automotive lighting Motor vehicle Bumper Vehicle


That's the fuel tank under the sub, and you can see where the magnet is making contact with the fuel tank strap.

I don't think opening up this hole will help the 8" subs ... now if opening up this hole, and printing new mounts to allow 10" subs to be mounted would work ... that's a good choice.

@KFXGUY ... Have you considered shallow 10" woofers and a new mount design to allow them to fit under the rear deck cover? I think a 10" woofer's magnet could fit through the rear deck sheet metal, without having to modify the base footprint of your adapters where they mount to the deck.
 
#76 ·
Maybe the rear deck cover is rattling, and that's what you are hearing? Mine rattled pretty badly until I put closed cell foam on the entire underside, and that was without any speakers in the rear deck at all. It was rattling due to the sealed 12" sub I have in the trunk.
 
#78 ·
Surprisingly its not rattling. I'll try to explain it better....

so at low volume, it sounds good, catches some really low notes, and after discovering a feature on my dsp I wasnt aware of, it now catches some higher notes. But when i turn it up, the bass almost stops being bass (lower frequencies with higher more cone movements) and starts to sound distorted and turbulent. Then when a member earlier on mentioned something the sound being tunneled. Then I looked at it last night and realized those lips being like that and the subs being barely able to "breathe" may be causing me issues. Airflow and sound can be tricky.....
 
#77 ·
Oh, and check your 3rd brake light clips. They have a tendency to crack/break, and when they do, the 3rd brake light housing rattles really badly as well. One of mine is broken, so I used butyl rope to affix it, and keep it from rattling when it's mounted in place.

The more you describe what's going on, the more I wonder if you are hearing stuff rattling, and mistaking it for distortion.
 
#79 ·
Oh, and check your 3rd brake light clips. They have a tendency to crack/break, and when they do, the 3rd brake light housing rattles really badly as well. One of mine is broken, so I used butyl rope to affix it, and keep it from rattling when it's mounted in place.

The more you describe what's going on, the more I wonder if you are hearing stuff rattling, and mistaking it for distortion.
the brake light.... the clips have anti rattle foam and so does the rest of it. There's no rattling..oddly...


edit..... does it with the back deck cover and brake light off too... forgot to mention that...
 
#83 ·
The woofer should be sealed to the mount you printed, and the mount should be sealed to the rear deck metal. So long as the backwave is separated from the front wave, you won't get cancellations.

I would put soaking wet bath towels on top of the fuel tank cover.
 
#84 ·
The woofer should be sealed to the mount you printed, and the mount should be sealed to the rear deck metal. So long as the backwave is separated from the front wave, you won't get cancellations.

I would put soaking wet bath towels on top of the fuel tank cover.
thats an excellent idea.....I was over thinking it again!

The sub is sealed to the mount and the mount is sealed to the deck.
 
#87 ·
This will give an idea as to what I'm talking about ... a picture is worth how many words?

Motor vehicle Automotive design Car Audio equipment Trunk
 
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