aperiodic venting

[UMWDawg92 10+ year member]

Anyone using this method for your midbass? How does it compare to IB and sealed? Basically I'm just wanting to know if anyone is doing this and getting great results. It seems like a pretty good idea only having to use a tiny enclosure but getting similar response to a large sealed box.

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[winkychevelle 10+ year member]

try diyma they can help u better than most of the guys on here. And I can say when built right that speaker enclosure can do some wonders but I have little experience with them other than listening to a friends over my sealed up doors his play so much cleaner

 

[keep_hope_alive Premium Member]

i've ran an aperiodic midbass, midrange, and sub. i can answer your questions right here.

no such thing as IB in a car unless you had the speaker exposed to the elements. best we can get is Trunk Baffle which is usually incorrectly termed "IB".

small sealed enclosures have low frequency roll-off but higher power handling. for midbass you really want a large volume. you can get good midbass with a small vented cavity - like the kicks, but you need lots of power and careful attention to de-couple the speaker baffle from the floor or you'll get structural resonances. I had a ~125Hz resonance from my floor woofers. Scott Buwalda recommended a two-part epoxy resin on the floor with lead added in to substantially increase mass. i want to try Green Glue between the baffle and vehicle to see if that damping helps. non-hardening modeling clay can also work.

you'll never get a similar response to a large enclosure with aperiodic or vented. each one sounds quite different. i had 6.5's in my kicks, vented to the outside, and i tried both with aperiodic mat and without. now the midbass are in the doors, playing with a 160Hz 30dB/oct LPF and a 63Hz 6dB/oct HPF. my mids in the kicks are 160Hz 30dB/oct to like 4kHz or so. with T/A my bass is centered above the dash with a proper soundstage for vocals and instruments. door midbass can work well with proper midrange placement and crossovers. course, i've also heard 2-way comps with woofers in doors with tons of bass and midbass as well as amazing vocals and a great sound stage (with T/A). all depends on the install and tweeter location.

can small, vented midbass enclosures work? certainly, they have won world finals in all divisions. are they difficult? you bet. lots of tuning and modifications are required to get it right.

 

[FtheNutHuggers]

Try using a circular collapsible collander. You can bolt weights to it and the whole thing is silicon and does not capture moisture.

 

[keep_hope_alive Premium Member]

the aperiodic mat is usually sandwiched fiberglass or open cell foam. the thickness vs. area determines tuning. you can tune the Q of the enclosure with the vent. you can also control the fs impedance spike.

pics of your colander? are you saying this is outside the car protecting the speaker?

 

[UMWDawg92 10+ year member]

the aperiodic mat is usually sandwiched fiberglass or open cell foam. the thickness vs. area determines tuning. you can tune the Q of the enclosure with the vent. you can also control the fs impedance spike.
pics of your colander? are you saying this is outside the car protecting the speaker?

Can you tune the enclosure by ear or do you really need an RTA mic or the WT3? I was reading over on DIYMA that you have to use one of these tools to find the impedence curve and tune by adding or removing from the membrane until your curve is at its flattest. I was thinking can it really be that bad to just add and remove until it sounds the best? I'm not planning on competing or anything.

 

[UMWDawg92 10+ year member]

oh and the reason I was wanting to try this is my mids aren't great at running IB, they're more designed to run ported and I read that doing this helps get a good response out of woofers that are designed to be ported

 

[VWBobby 10+ year member]

I had a ~125Hz resonance from my floor woofers. Scott Buwalda recommended a two-part epoxy resin on the floor with lead added in to substantially increase mass. i want to try Green Glue between the baffle and vehicle to see if that damping helps. non-hardening modeling clay can also work.

Mass loading is a great way to kill resonance, but so is structural rigidity and decoupling by insulating layers.

You can laminate a strip of steel to the back of the floor boards using 2-part automotive epoxy or urethane body panel adhesive. Think of panel resonance like a drum skin. Prevent the drum skin from moving, problem solved. I've found that anchoring door panels, etc with screws directly from the speaker holes through the steel of the door itself (sandwiching the door panel) will usually make a rigid enough connection. If I need more rigidity I will add steel or make MDF baffles to mount the speakers into and fiberglass these to the panels. Between rigidity and decoupling through sound deadener, most rattles and harmonics can be killed pretty easily at moderate power levels. Other rattles and harmonics are usually traced down to door mechanisms, window regulators or loose interior trim. Fix these problems and you don't have to worry about resonances as much. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[FtheNutHuggers]

It is a passive radiator, not an AP membrane. But here is a link to something like what i used. I typed colander, thinking about the collapsible kitchen ware i use at home. It is a collapsible bowl. http://item.mobileweb.ebay.com/viewitem?itemId=390267936277

They are fun to play with. A little silicon, few screws and some yellow eraser clay to sample weighting.

 

[keep_hope_alive Premium Member]

Mass loading is a great way to kill resonance, but so is structural rigidity and decoupling by insulating layers.You can laminate a strip of steel to the back of the floor boards using 2-part automotive epoxy or urethane body panel adhesive. Think of panel resonance like a drum skin. Prevent the drum skin from moving, problem solved. I've found that anchoring door panels, etc with screws directly from the speaker holes through the steel of the door itself (sandwiching the door panel) will usually make a rigid enough connection. If I need more rigidity I will add steel or make MDF baffles to mount the speakers into and fiberglass these to the panels. Between rigidity and decoupling through sound deadener, most rattles and harmonics can be killed pretty easily at moderate power levels. Other rattles and harmonics are usually traced down to door mechanisms, window regulators or loose interior trim. Fix these problems and you don't have to worry about resonances as much. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

all good points. my kickpanel baffles are rigidly connected to the floor. i have multiple layers of deadener and closed cell foam isolating the woofer, but still, 125Hz killed me. a very measurable spike. so now i just don't run the floor that low.

BXT II on the baffles. I also added 1.5lbs of non-hardening modeling clay inside the midbass cavity - in the nooks and crannies, along the baffle inside seams, etc. I also put in a ribbed rubber mat to mimic a deflex pad.

Then I did the passenger side as well, new deadening, another 1.5lbs of modeling clay, rubber mat, etc.

new baffle is same as previous. i designed these baffles to be removable and swappable - good thing. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[keep_hope_alive Premium Member]

some more details on the vented kicks, all details are in my build log on SoundDomain.

 

[keep_hope_alive Premium Member]

yes, the WT3 or an RTA are the best ways to tune an aperiodic membrane. by ear can work to, but you'll never really know what it's doing.

 

[UMWDawg92 10+ year member]

Thanks you guys helped alot and gave me some ideas on to make sure my mids are decoupled from my doors as well. I'm going to tune by ear for now until I have the cash to order myself a WT3 then I'll go back and make adjustments from there.

 

[VWBobby 10+ year member]

Keep_Hope_Alive,

Very nice install!! I bet your stage sounds perfect. Nice placement and aiming of the speakers. Only thing I would be worried about is stepping on them, other than that, very cool. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[keep_hope_alive Premium Member]

i have grills to protect them and carpet over that. they've also handled two winters (in northwest IL) with ease. yes, the soundstage is very good with a little T/A.

i want to recarpet the floors so they are completely stealth. since they don't take up any floor space, people don't see them.