Very Narrow Small Subwoofer

[jcmjrt]

I have a back loaded horn driven by a tannoy coaxial. It sounds wonderful and fast but doesn't go low - maybe 80 - 100 HZ. I'm working in limited space so just making it huge doesn't work. I saw that tang band makes 4" subwoofer drivers and I was wondering if I could make a subwoofer to go under each speaker (maybe separated by a sand box to reduce vibrations) that including box would be no larger than:

6 inches tall, 18 inches wide and 16 inches deep

that would be fast and good for 2 channel music, go up to about 125HZ and maybe down to 40HZ?

I have good woodworking skills so complexity of the box isn't an issue...transmission line, whatever...

I brought up tang band because I saw the 4" drivers and suddenly thought that my low height requirement might be doable...but I'm not married to tang band. I'm looking for ideas on accomplishing my design specs.

[badman]

Do you have space to work with behind the speaker? You could do a bandpass venting under the speaker or some such. It'll take a real nice sub to keep up with the tannoys, a 4" isn't even really a sub. Is an 'infinite baffle' (mounted in the wall/floor/celing) install out of the question? That's a good way to get great bass from limited space.

[MJL21193]

Hi,
Given any thought to a Linkwitz transform? Using 2 or more small subs, such as the W5-1126SC from Tangband and a suitable amp, could give good results.

[jcmjrt]

Originally posted by badman
Do you have space to work with behind the speaker? You could do a bandpass venting under the speaker or some such. It'll take a real nice sub to keep up with the tannoys, a 4" isn't even really a sub. Is an 'infinite baffle' (mounted in the wall/floor/celing) install out of the question? That's a good way to get great bass from limited space.

I dont' have a lot of space behind the speaker. I was hoping that the 4" driver (or maybe a couple per sub) would be adequate for going down to only 40 HZ...which you are right isn't really sub territory. I thought that infinite baffle subs were really more for home theatre than music systems....more shake the earth rather than fast/precise...and with my requirement to go up to about 125HZ the sound should be locatable rather easily and need to be colocated with the speakers. I can't build an IB sub directly under or over each speaker

Originally posted by MJL21193
Hi,
Given any thought to a Linkwitz transform? Using 2 or more small subs, such as the W5-1126SC from Tangband and a suitable amp, could give good results.

I'm not sure what you mean with "given a thought to a Linkwitz transform?" I've heard of Linkwitz XOs?

I was thinking that I would colocate a sub with each speaker. When you mention that W5-1126SC...are you saying that I'd need to use a 5" vice 4" driver? I doubt that I could meet my 6 inch height requirement with a 5 inch driver but thought it might be possible with a 4 inch one..leaving 1 inch on each side for cabinet.

I've been doing some searching and the PMC sub (TLE-1) looks somewhat hopeful. It's a little too big (and I'm thinking about it on it's side not standing up) but then I'm not wanting my sub to go very deep.

[MJL21193]

A Linkwitz transform is an electronic equalizer that is tailor made to the specs of the drivers. The main benefit is the small box size and a sealed alignment. Need a reasonably powerful amp though.

Another possibility is isobarik or compound loading, two drivers in the same volume as one.

For an overall height of 6 inches a 5 inch will fit if mounted from the outside. The cutout size for a 5" is around 4".

[rjb]

Your available volume is less than one cub.ft.. That limits your driver choice, and also the type of loading. TL's and their variations will be bigger than BR or sealed with L-T.
Also be aware that you will be requiring a small cone to move a long way at these low frequencies, so to get reasonable power output Xmax will need to be very large indeed.
I suggest you start by considering the decibel output you require. You may find small box/small single driver will not do but multiple drivers may help to get the output, although this also reduces the volume available per driver, forcing you towards a sealed box plus L-T, and a high powered amp.
For an initial idea of possibilities get WinISD Pro and plug different driver combinations and numbers into that.

[jcmjrt]

Originally posted by MJL21193
A Linkwitz transform is an electronic equalizer that is tailor made to the specs of the drivers. The main benefit is the small box size and a sealed alignment. Need a reasonably powerful amp though.

Another possibility is isobarik or compound loading, two drivers in the same volume as one.

For an overall height of 6 inches a 5 inch will fit if mounted from the outside. The cutout size for a 5" is around 4".

I don't know how powerful an amp is necessary but I'm not averse to a good one with watts. Cheap isn't the main criteria and a tailor made equalizer might also be possible but I really have no idea about the cost/requirements to do that.

I was rather thinking that I'd need two drivers per side.

The driver mounted on the outside to get a small size with bigger driver is interesting. Are there any drawbacks to that?

Originally posted by rjb
Your available volume is less than one cub.ft.. That limits your driver choice, and also the type of loading. TL's and their variations will be bigger than BR or sealed with L-T.
Also be aware that you will be requiring a small cone to move a long way at these low frequencies, so to get reasonable power output Xmax will need to be very large indeed.
I suggest you start by considering the decibel output you require. You may find small box/small single driver will not do but multiple drivers may help to get the output, although this also reduces the volume available per driver, forcing you towards a sealed box plus L-T, and a high powered amp.
For an initial idea of possibilities get WinISD Pro and plug different driver combinations and numbers into that.

I might be able to eek an inch wider and/or maybe two - three deeper (but no higher and that's pushing the limits on wider and deeper too) to get a little more if that made a big difference. Multiple drivers/box is definitely a thought. Is there a better small driver than the tang band 4" to give the requirements including Xmax? I'm not singling out any particular design but looking for possibilities to meet the requirements. I'm afraid that WinISD isn't a possibility for me to use because I have macintosh.

[planet10]

A tough one... are the tannoys limited on the bottom because of their box? Or the driver?

dave

[MJL21193]

Originally posted by jcmjrt

I don't know how powerful an amp is necessary but I'm not averse to a good one with watts. Cheap isn't the main criteria and a tailor made equalizer might also be possible but I really have no idea about the cost/requirements to do that.

The amp would have to have plenty of headroom for transients. The Linkwitz transform circuit provides a proportional amount of boost below the tuning frequency of the enclosure. That could be as much as 20db gain.
The problem with Linkwitz transforms (LT) is that they are pretty much DIY - you need to calculate the proper values for many of the components. If you are not into electronic work, this can be daunting.
I picked the W5-1126SC because it has a huge Xmax for such a small driver. 2,3 or 4 could be installed in a small box (size you noted would be in the ballpark, maybe a little too big). This driver looks good for an LT.

At this point I need to correct myself (yet again). Compound loading will cut box size in half. In theory. you could calculate box size foe one driver and put two pairs, compound configuration. Thats four drivers in a box sized for one.

[badman]

Can you do us up a diagram, with how much space you have and where? A 4" driver (or multiples) represent a huge performance sacrifice. If we were able to get you up into 6.5" territory we could get you going with an Extremis or the like.