rear deck baffle idea (1 Viewer)

[Phoenix]

In the rear deck of my car, I want to seal the 6x9s from the trunk to 1. To increase power-handling, and 2. most importantly, to avoid blowing the speakers due to the pressure of my 12" infinitys. The way the rear sheet metal is in my car, (90 bonneville) it would be a bit difficult to seal them off 100%. I am looking at DYI install only. There is a plastic cover that screws onto the underside of the deck. Would it be possible if I packed the back of the deck with this insulation? Before you laugh, I think it would work because it would dampen the speakers and would have the effect of stuffing a sub box. I've heard of somethig like this it was called an aperiodic membrane. Am I just hallucinating, or could this actually work?

 

[David.G]

you won't blow your 6x9s from the pressure of your subs i doubt theres that much. Mine aren't even effected by my subs and my subs are way better than the Infinity perfects(i've used them before). You can seal them but make sure you have the right internal volume if you do. I'd say do fiberglass enclosure if any type. Takes less room up and if your factory screws have bolts on the underside you can screw it in and bolt it down. You could also see if there's the foam baffles out for a 6x9....don't remember seeing them but they may have them out. If anything, put a cap on your positive wire to cross them over or cross them over on an amp or HU (if available) to get better sound from them. I used to use 6x9s for rear fill but found that they suck for high volume SQ and opted not to use them and go with a nice strong front stage and simple rear fill.

 

[Phoenix]

Are you sure that the pressure won't damage the subs? Would you reccomend that I use the 80hz high pass x-over built into mt amp? its a rockford 500x btw. Im just worried that my 6x9s will go for crap with the subs beating on them.

 

[KenWong]

No, your subs will not put "pressure" on your 6x9's... they will be perfectly fine. If you are worried about your rear speakers, I think you should also remember that subs causes strain on the electrical system including your battery and altenator, those have a much higher chance of dying then your 6x9. (something else to worry about) I would be more fearful of even the trunk lock breaking, then your 6x9 (which I have seen happen before.) Also, the High Pass crossover is for you to tune your subwoofers to how low, or which frequencies to play. Depending on your subwoofer, and what type of music you listen to, play around with it until you get what you like. And again, I have never ever heard any speakers break due to the impact or pressure of subwoofers, unless they're 10 years old factory paper cone that has been beaten by the sun, they'll be fine.

 

[Phoenix]

OK ill give it a shot. The amp I was referring to is the one that is driving my mains (4 ch) It has a low/all/high (80 hz, 12db/octave)pass filter switch. (I dont like to use single caps b/c it shifts the phase) I don't have a sub amp as of yet, but when I do I will get one with a variable low pass filter. I am also looking for something to clean up the 6x9s, I wanted to use the stuffing to dampen the cones and hopefully smooth out their response (I think its called and aperiodic membrane) and comments about that? Soon I a getting an optima red top and a 160 amp alt when I can afford it.

 

[Phoenix]

UPDATE!!!

I tried hooking up my subs without sealing the 6x9s. Guess what! The "pressure" of the subs BLEW MY LEFT 6X9. So much for that theory, The subs weren't even at HALF excursion. I guess that answers my question. Now I need to seal them for sure :frowning: I've decided to only use one sub because 2 is WAY overkill for what I want, rattles the hell out of the car too. Well thanks for your input though. But theres nothing like trying something yourself to see what happens.

 

[David.G]

dude unless you 6x9s are the cheapest things ever, your sub didn't blow it. Considering i used Polk 6x9s and got 140.7db in my trunk from my subs on 700RMS to each ED sub and my 6x9s didn't blow then yours off Infinity subs and that low amt of power you're using isn't the problem.

There's two things i did see you mention that may have caused the problem. One you need to mat your rear deck down or its going to sound awful. Your 6x9s do have enough power to move and will cause a horrible rattle and could make the SQ terrible. Also you don't want your speakers to touch metal to weatherstrip the bottom or mat the metal around the speaker. Make sure you speaker connectins don't touch metal either. Also you said you were going to use the high cross at 80hz???? Thats not right. You want to use a low pass on the subs and a high pass on the tweets. The high pass should be somewhere in the khz range and the low pass should be no more than 100hz for your subs. Full is good for a setup using a passive crossover and bandpass is good for mids. If you hooked you 6x9s on a high pass at 80hz you probably screwed them up because all thats going through it is 80hz and below. High pass only lets the highs "pass" through it.

But if your subs "blew" your speaker either your speaker was improperly installed or you connected it wrong, but no way that the subs caused it.

 

[Phoenix]

Hmm.
1. yes, it sounds like A$$ without matting ,the whole back of the car rattles so bad that I would be embarassed for people to hear it from the outside.
2. When I blew the 6x9 they were unpowered, (only the subs were hooked up to the amp) I unhooked the rear speaker leads at the HU. The speaker blew due to over excursion. (or it would seem)
3. They have 1/2" x 1/2" weather stripping around them, and they mount into a plastic base.
4. What I meant is that my amp has a low pass crossover from 20-80hz and a high pass crossover from 80-22khz
5. Everyting worked and sounded fine before I put my subs in (except for the bass obviously)

P.S. I made a list because its less confusing for me :b and would dynamat really stop the sheet metal from physically flexing?

 

[KenWong]

I agree with David in that the excursion probably didn't cause your rear speakers to blow... but I still don't understand what you're asking... are you asking which filter to use for your sub? Also, dynamat will really help your trunk with the rattling, what dynamat does is basically give a better/more solid weight to your car as well as one that can control the sound waves better. There are tons of options out there, not just dynamat, look for edead, cascade, etc.

 

[Phoenix]

I was originally asking if packing the plastic cover on the back or the 6x9s with insulating material would perform as if they were in a sealed enclosure. I was talking about crossovers because I must have explained it wrong. I know what crossovers to use. Now I need to look for a dynamat type material because the rattling is unacceptable.

 

[David.G]

unless you get something to make an enclosure for the 6x9 it won't really work. You'll need to seal the entire 6x9 but in doing so you need to make sure its the right enclosure size and thats its solid like a sub box. Plastic won't really do any good for it and polyfill won't stop the SPL from getting to the 6x9. I'm not sure how you can tell a speaker is blown if it was unplugged. What exactly do you mean by blown? You can't blow a speaker if there's no power. Only thing i can think of is that your rear deck rattles way too much and is causing the speakers to sound terrible because the metal is constantly flexing. In my car my rear deck is matted with 2layers on the top and a layer on the bottom. not saying infinity's are bad but with just 2 12" subs they aren't going to blow a speaker. if anything you're putting too much power to the 6x9s and that amt of power plus the fact you have no deadening has made them speakers either comes lose or you're getting alot of movement from them speakers and the woofer part can't handle the power going to it. I could see that since 6x9s are terrible speakers to play at high volumes.

 

[Phoenix]

The 6x9s were unpowered during the bass test, but after, when I plugged them in by themselves at low volumes, you can hear that the speaker is damaged internally, it crackles and distorts even when it is barely turned on. I didn't know the speaker was damaged until I turned off the subs and hooked the 6x9s back up. I just don't want to take a chance on damaging the new 6x9s that I will be putting in soon. The 6x9s are acting as passive radiators and the rule of thumb is that a passove radiator should have a larger displacement than that of the powered drivers. All I know is that I saw the 6x9s moving over 3/8 of an inch peak to peak and the subs weren't even at half excursion.

 

[David.G]

they should not have a problem but if you're that worried work on getting a full front stage and get rid of the rear speakers.

 

[gadgeteer123]

Hey just to let you know I have a single 1000 watt rms sub and im only putting 600 watts rms into it and it pushes so hard I can see the back window actually push outward on every thump in my wagon, plus i can feel a breeze from it in the front seat.