Question for you car stereo guys/bassheads

[yotsuya]

Hey guys, quick question for those of you who build your own speaker enclosures...

I'm building a custom audio project for my daughter's birthday. It's basically a radio-sized box powered by a Lepai amp pushing out to two 4x6 speakers. Within the box I plan to isolate each speaker so it's basically in it's own chamber. My question to those of you who have built speaker boxes before is should I use some sort of caulk to seal the seams on the inside? I plan to put ports in the back for bass, but I'm looking for any tips. Thanks!

[yotsuya]

Ok, in doing some research, I see builders recommending using a caulk to seal the seams to make it airtight. So if I do that, should I not worry about adding a port for the bass? It's not a subwoofer, so I'm not really expecting to push a lot of bass. I'm more interested in clarity and it sounding good than anything else.

[dkersten]

It is very dependent on the woofers in the enclosure.  A 4x6 has a midrange/midbass woofer that probably doesn't extend much below 150 hz, so while the enclosure will help with that lower end, you won't gain much from it unless you can tune it to match the speaker.  Those speakers are really designed to just work in a situation where you isolate the front from the back (ie infinite baffle).  But isolating them from each other is not a bad idea.

Bottom line is that a small enclosure will help with bass but since you won't have any idea how to tune the enclosure to fit the speaker, all you can really do here is punt.  You might end up with a spike at a frequency that makes it sound muddy, or you might end up with a nice boost in the lower frequencies.  So don't make the enclosures too small, the bigger they are the less boost you will get but also the lower the frequency of the boost.  A half cubic foot or more should be good.  Just seal it up and don't even think about trying to port it.  Add a little polyfill or Dacron behind the speakers to break up standing waves.  Be careful with the bass because since the speakers are not designed to go very low in frequency, running full range to them with any amount of power can damage them.  If you hear any distortion on music with a lot of bass, either turn it down or use some kind of equalization or crossover to dial down the bass.  Under normal volumes this should sound just fine and have a little "punch" from the increased midbass. 

[yotsuya]

Thanks, Dave.

[roknrol]

Yep, I concur with Dave. Isolate the speakers, seal to be airtight (can use DAP Alex Plus), and loosely fill half of each chamber with polyfill; do not port.

[yotsuya]

Thanks, guys! Any idea on places I can find polyfill?

[dkersten]

any fabric store, walmart, hobby lobby, Michaels, etc.. 

[roknrol]

Step 1: Go to michaels.com and print out 40% or 50% off coupon. Pretty much always have one of them available.
Step 2: Go to Michael's and pick it up in the Quilting(?) department. I think one 20 oz. bag'll run you about $5.99 before the coupon.
Step 3: Fluff it a little when placing it in the baffle box. You want it pretty loose and taking up about 1/2 the overall space.

[dkersten]

I always preferred the polyester quilt filler on a roll or in sheets as opposed to the polyfill in the bag.  Not so important in a small enclosure like this, but in any tuned enclosure there are a few reasons to use the sheets as opposed to the bagged fill.  The stuff in the bags is for pillows and has no structure, so it can bunch up and might settle and end up bouncing around inside the enclosure, possibly even interfering with the speaker's mechanical parts (ie the cone).  The sheet stuff retains its density and will stay in place and not bunch up.  Dacron is a brand of polyester fiber that is often used in quilting filler and has the best properties for speaker damping. 

Just sayin... 

[jaharr01]

That's a pretty cool gift there Dad. Are you going to put any artwork on it. Maybe a touchscreen?
Jay

[yotsuya]

That's a pretty cool gift there Dad. Are you going to put any artwork on it. Maybe a touchscreen?
Jay

Naw, keeping it simple. I painted it metallica blue and put a Doctor Who sticker on it. I put a sound-reactive element on it, but other than that, I'll leave the bling for Kaneda. All she cares about is streaming her music to it.