help with a small bipolar speaker

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I am designing a portable indoor/outdoor speaker and I am inspired by the boominator thread. Those folks are really into making great sound, outdoors, with very little power.

Enter my situation. I've been interested in the same thing, but much smaller. and with a strong emphasis on esthetic design.

To make this as short as possible, I would like to build a very small, ported bipolar enclosure using the components below.... (I am thinking around .1 cubic feet for the whole thing)

Dayton RS100-4 4" full range speakers

and powered by the lepai ta2020

What might I expect from this arrangement, compared to these two speakers mounted together on the same side? I have heard that there may be some bass reinforcement in the bipolar setup. Would another speaker choice achieve more volume than these in this size of enclosure? Perhaps two small PA or guitar speakers?

Anyone got a port size recommendation? Or how to I calculate that?

Many thanks,

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The volume required for two in one box will double as will size of port. The advantage of bipole is that you wont have the loss of bass due to baffle step. That is, the bass will still sound as deep with the speakers in the middle of the room as if they were placed next to a wall. You will need to have a divider between left and right channels though.
The idea with regard to bass enhancement is this: with two speakers firing in opposite directions, all frequencies are being radiated in both directions equally and therefore bass frequencies, which at a certain level begin to radiate 360°, achieve parity with higher frequencies. That's not a particularly good explanation but the point is that you don't get bass enhancement as such, rather just a balanced sound.

I've never built a boom box, however it occurred to me that if this is to be used in wide open spaces, such as a park, I might intentionally design it with a bit of a bass peak to compensate for the lack of room reinforcement that we're typically used to. Going by the specs at parts express, I would do something like 3.5L tuned to 80hz, for a little peak around 100hz and then a rolloff at 70.
thanks xrk97 and chazdrumzalot

That helps me out a ton. What do you two know about the magnets touching.... the people in that boominator thread talk a lot about this.

also, chazdrumzalot... I'm going to do just what you mentioned... is there any chance I could bum a port length from you? I'm not so hot with the enclosure calculators.

lastly, what is the proper way to think about a crossover to spare these little speakers from subsonic and or just too much bass that it can't handle? Even though they are expensive, those little fmod preamp crossovers cutting things out below say, 60 hz sounds like a smart idea when I'm trying to get the most volume out of this. But I'm only guessing at this. I'm unsure if those Lepai 2020 amps have a subsonic crossover built in.

Port lengths are easy! Go here:


Put in the box volume (in liters, in this case), put in the tuning frequency (80hz, in this case), and your desired port width; here is where you can play around a bit, or try and match the port length/width to something available at madisound or partsexpress.

Since this is going to be a shared enclosure, I tried putting in 7 liters with one vent. A 1" port would be way too short: 0.6". A 2" wide vent would be 3.88" long, which is an awkward length. So instead I tried 79hz and I got a length of almost precisely 4". So a 2" wide, 4" long port should work pretty well for your application.
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