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Discussion Starter · #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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Discussion Starter · #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.
 

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Discussion Starter · #6 ·
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.
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).

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Discussion Starter · #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.
 

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Discussion Starter · #11 ·
I've been following your post... IB 8" is no bueno! Dude if Ida didn't have my balls in a sling I'd bring my laptop and mic over and see what's what. I live in Metairie and just got back in my house with power Monday. Bet you're glad that bad b!tch took a last minute turn to the right! My project has moved to the back burner temporarily! Stay in touch and let's try and get together sooner than later. Dave
Yea maybe one day I can ride out your way. Ive been looking at mic setups today, just contemplating. Then I think to myself, just throw the dang sub box back in the trunk and be done with it! But i hate giving up the little room i have.
Yea we actually got hammered pretty hard in my area. We were lucky though, i only lost power for 8-9 days. We just got it back.
 

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Discussion Starter · #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.....
 

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Discussion Starter · #20 ·
Scroll up and see the pictures I posted. Without the mounts, you can't fit any speaker in there at all, as the magnet will hit the fuel tank. I'm surprised he got 8" in there to begin with!
This. I printed them with a lot of infill. I doubt they flex at all and the are about 1/4” thick.
 

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Discussion Starter · #27 ·
Certainly no expert on the sound stuff, but I know 3D printing pretty well. Those look like really solid adapter rings but I wonder if they are causing an issue by tunneling the sound waves. Kinda like yelling down a paper towel tube.
For IB don’t you want as much open space behind the subwoofer as possible?
you could be on to something. Maybe I should try opening the holes up in the back deck.
 

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Discussion Starter · #30 ·
If you don’t mind opening them up so they can mount flush without the adapters it would probably be worth it.
Yea that would be impossible. Not enough depth. They touch the gas tank as it is now. I mean I could take the gas tank out....,but....lol
 

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Discussion Starter · #31 ·
Have you thought about building enclosures for the 8" woofers, to fit behind the rear sail panels? I think you would get more of what you're looking for by doing that, instead of trying to make an IB setup work in the rear deck.

There's a guy in Australia who printed enclosures for 9" woofers to fit that space ... He's a great guy too, and might be willing to share his 3D printer files with you? Let me know if you want his contact info.

View attachment 310806



There's not enough depth to flush mount anything back there. There really is no room under that rear deck.
I can’t imagine the sound being able to make its way out of that little 4-4.5” grill on the side panel...and it not rattle badly.
 

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Discussion Starter · #33 ·
Subwoofers work very well in that location. The sound doesn't need to make its way out of the 4.5" grill, as sub frequencies are not stopped by the trim panel.

Many guys have installed 8", 10", 12" and even 13" shallow subs in there with great results. Hendrix engineering used to make fiberglass enclosures for it even, but they stopped offering them a few years back due to such low demand (ie: limited number of GTOs on the road).
How does the plastic panel not rattle tho? For that matter, I bet I could stuff some bazooka tubes in there. I’m kidding. Wait...am I? I need to do some measuring now..... that wouldn’t be a bad idea.....
 

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Discussion Starter · #35 ·
You just deaden the panel.

Here's some info I found a while back, when I was researching it. This guy put 8" woofers inside MDF boxes he built for the space. I think the 3D printed designs are MUCH better, but this gives you an idea of what can be done with the space.

View attachment 310809

View attachment 310811
Yea I saw those boxes long ago, I have that picture of the measurements saved in my phone. I never really considered that because I thought the panels would rattle.
 

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Discussion Starter · #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.
 

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Discussion Starter · #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.
 

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Discussion Starter · #44 ·
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.
Car is apart right now. I’m going measure. Be right back.
 

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Discussion Starter · #53 ·
I think you have mistaken me for someone else, as that was my first post in this thread.
Well I didn’t go back and look who posted, I was just in a hurry to prove someone wrong. In which it backfired on me. Lol
 
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