Planning a Home Theater Sub

[spidrman]

After reading through several of the SUB design threads here, I think I've decided to build a sub using the Dayton RSS315HF driver. This is for "mostly" home theater but my wife has several concert DVD's that she really enjoys so there will be some "music" use as well. The room is about 2400 cu ft. I'm leaning toward sealed.

I do have a couple of questions for the "experts".

1. Would two boxes of about 4 cu ft each be better than one bigger box with two drivers in the same box?

2. Do you only get the +3db boost from two drivers if they are physically next to each other? (as opposed to being mounted at opposite ends to cancel physical vibrations)

I want clean, tight bass with some decent low extension for movies. But then since currently I'm running a tiny 10" cheapo sub, I'm sure anything I build like this will be waaaay better.


Thanks!!!

[---k---]

1. Yes. much easier to move around. saves on the back. there will be no difference in quality, all others being equal. Though, I haven't run the numbers to determine if 4cuft is right.

2. yes.

[Dennis H]

Two drivers will give you 6dB more SPL assuming they are reasonably close together, say within a few feet at sub frequencies.

[JonMarsh]

One configuration that's popular with some manufacturers and with some DIY folks is what is called a force balanced design; that is, the two drivers are on opposite cabinet walls, and the vibration reaction on the enclosure cancels. Krell's MRS sub is built this way.

OTOH, building everything into one cabinet means one much heavier cabinet, and in some situations, having two subs placed on opposite side walls may work better in some rooms acoustically, or for layout reasons. Depends on your specific situation, or if you have some special layout issues (asymmetrical room, other rooms just off your HT/listening room in an asymmetric placement.

[Brian Bunge]

Two drivers will give you 6dB more SPL assuming they are reasonably close together, say within a few feet at sub frequencies.

Dennis,

Don't forget half of that 6dB is from a doubling of power. I know that you know this, but I just wanted to make sure that the OP knows as well.

[spidrman]

One configuration that's popular with some manufacturers and with some DIY folks is what is called a force balanced design; that is, the two drivers are on opposite cabinet walls, and the vibration reaction on the enclosure cancels. Krell's MRS sub is built this way.

OTOH, building everything into one cabinet means one much heavier cabinet, and in some situations, having two subs placed on opposite side walls may work better in some rooms acoustically, or for layout reasons. Depends on your specific situation, or if you have some special layout issues (asymmetrical room, other rooms just off your HT/listening room in an asymmetric placement.

The room is symmetrical and there are no openings other than a door to other rooms. My main limitation is that I want to keep the depth of the box (outside) to 18 inches as that is the distance from the front of my screen to the back wall and for aesthetic reasons it would look better not sticking out farther than the screen. I can go as tall as 24 inches and any reasonable width to get the proper internal volume. I'm not too concerned with the weight of the box but I like that two boxes is more flexible for "position tuning". Plus if I go that route I could just do one to begin with and see if I even need the second one.

From another thread (here ) it seems like a good sealed volume would be 3 cu ft (or larger) and a 250 watt plate amp would be sufficient although on another thread it was built with a 500 watt plate amp. Decisions, decisions.

[sprint_9]

I have mine slot ported to 19 hz in a 4.5 cuft box with the Dayton 240 W amp and it is pretty good, my room is really crappy as far as acoustics but it is nice and deep. I wish it were a little more tight but like I said the room probably has a factor there, and going sealed will cure that for you.

The 240 W works good for ported and might for sealed as well, with a sealed box you could probably give it a little more power, but these subs dont require a massive amount to put out good bass. Ive read the the Bash 500 that PE sells is actually a little over rated, although I wouldnt read too much into that as I believe it was just and individual not a trusted source. A little head room might not hurt either.