# aperiodic vent baffle how to



## spmpdr

step 1 : apply 2 medium coats of f/g resin with crushed up matting to baffle allow 1st coat of f/g resin to get tacky then apply second coat.for this install i used a 5:1 f/g resin to bondo mixture








step2: measure baffle to proper depth ,i.e. these are used for door applications,so measure your mounting depth with the window down cut baffle to length








step 3 cut carpet ,should be medium dense fiber carpet (like speaker box carpet) to about 1/8" bigger than the hole you cut in the baffle. hot glue it to the baffle and you have this:








aperiodic vent enclosure!!!! these things worked great for my dedicated mid bass project in my doors .total cost about $30.00,hope it helps


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## inoii

hmm interesting does it affect the midbass? seems like it limits the air space?


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## spmpdr

inoii said:


> hmm interesting does it affect the midbass? seems like it limits the air space?



It made my peerless sls 6.5"s alot more tight and punchy sounding when they were in the doors i/b they had alot of resignation. I guess its just how you prefer your mid bass


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## jbholsters

You are limiting your ability to tune the vent using carpet as your resistive layer. You would get better results glassing a ring into the back with mesh (could use some Parts Express mesh grills of the appropriate size) ad fiberglass insulation (this is your resistive membrane) and another grill on the side that faces into the door or kick-making a sandwich. This way you can tune the membrane (mechanically) by adding/removing material and/or by compressing/decompressing material (resistive layer). By adding/removing material you are adjusting the impedance of the driver over a given set of frequencies. You will never get it perfectly flat, but you will be able to flatten it out quite a bit. I have posted tuning instructions for this on the board.


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## ErinH

One word: water.


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## Oliver

plenty of tutorials on aperiodic membranes. [ adjusting the fill, etc.., ], measuring the impedance w/pics.

Then EQing it to get back what you gave up to make it the way it sounds best!


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## ErinH

^ true.

A woofer tester from parts express is a very valuable tool for AP enclosures, to measure impedance. Doing it manually with test tones, a DMM, and excel sucks.


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## Mless5

Roughly speaking, how restrictive should these layers be? I am going to do 8" midbass and I will certainly be interested in doing something like that instead of IB/sealing...


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## 03blueSI

Use fiberglass insulation instead. Easier to tune. Start with one sheet and either add or remove from there based on measuring impedance. This is exactly what I plan to do when I install my Scan 18Ws in the doors. They are more suited to ported than anything else and model like they would work well in AP.


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## spmpdr

jbholsters said:


> You are limiting your ability to tune the vent using carpet as your resistive layer. You would get better results glassing a ring into the back with mesh (could use some Parts Express mesh grills of the appropriate size) ad fiberglass insulation (this is your resistive membrane) and another grill on the side that faces into the door or kick-making a sandwich. This way you can tune the membrane (mechanically) by adding/removing material and/or by compressing/decompressing material (resistive layer). By adding/removing material you are adjusting the impedance of the driver over a given set of frequencies. You will never get it perfectly flat, but you will be able to flatten it out quite a bit. I have posted tuning instructions for this on the board.


good idea, next time i have my door panels off i think ill try that


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## jbholsters

bikinpunk said:


> ^ true.
> 
> A woofer tester from parts express is a very valuable tool for AP enclosures, to measure impedance. Doing it manually with test tones, a DMM, and excel sucks.


You can also run a sweep with a pc based program as well. There are several free ones that work very well.


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## jbholsters

03blueSI said:


> Use fiberglass insulation instead. Easier to tune.


I mentioned using fiberglass insulation. Actually thin pieces of duct board or thin pieces of Rmax work even better as you don't have to be concerned with the compression, only thickness. When I was an installer for a living I built lots of AP enclosures with this stuff.


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## 03blueSI

Thanks. I'll have to give it a try.


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## Elgrosso

I just tried something similar, but with PVC adapters + old socks + polyfill.



I wanted something easy to fill/unfill from inside.
Well I still have to remove the driver, but then I have direct access.

So far I just measured 3 states:
- driver free air
- driver in enclosure, but not in door, hole open just behind the driver
- driver in enclosure, but not in door, hole filled (not maximum possible but closed, but still pretty easy to blow through)



Now the enclosures are in doors so I'll make some more measurements.
I could try something much more blocking like glass/rock insulation.
Or even one of the standard AP from PE/scanspeak etc.
Do you think I'm on the right path?


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## beak81champ

What a great creative solution!


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## Elgrosso

beak81champ said:


> What a great creative solution!


Thanks beak81champ!
It works well, I didn't change anything for a week and didn't find anything strange like before with the too small boxes.
I'll measure more today, but guys do you know what kind of impedance curve I should try to reach?
Like flatter and smooth as possible, or just minimizing both peaks?


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## Eric Stevens

I suggest you lower the primary impedance peak as much as possible without raisng the minimum impedance above and below that peak.


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## Elgrosso

Ok will try that, thanks very much Eric!


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## Joe r

Amazing idea. Something I will be trying out.


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