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Old 15th April 2010, 03:41 AM   #1
ervinl is offline ervinl  Indonesia
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Default Want to know: small sub woofer speaker

Hi,

I just want to know is there any good, sound quality subwoofer speaker with low wattage but high efficiency (e.g. > 90db), so that I do not have to drive it with high wattage amplifier. May be just a GC amplifier or Class A SE or PP, which is usually < 60 watt RMS.

The room is only around 4x5 or 5x6 max, so no need for high wattage except good sound.

Thanks,

Ervin L
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Old 15th April 2010, 05:32 AM   #2
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Sensitivity and Hoffman’s Iron Law, or “why you can’t have your cake and eat it too” ? Audioblog
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Old 15th April 2010, 07:03 AM   #3
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Yeah, what he said!

What you want does not commercially exist, or is very rare. You need a large box with a PA-style woofer.
- Are you willing to build yourself?
- How big a box are you willing to live with?

If the room is small, and you don't crank Motorhead or expect to hear low organ pipes, 60W might be OK with a 1-2 cubic foot sub. But I question if you'll really get 60W out of the amps you mentioned. I also question if the sonic advantages of an SE etc would really apply to subs.

You could consider dual drivers with dual coils each, driven by a 4-ch chip amp. That would get more total power. But again, dunno that much sonic advantage exists.

P.S. "Sensitivity" is a midrange spec. It is should not be considered for subwoofers. High sensitivity only helps IF you are willing to use a large enclosure, and IF the parameters of the driver will match that enclosure and extend the bass down low. (The enclosure will be ported, by the way, to maximize sensitivity in the actual bass region). Otherwise, a "lower sensitivity" driver might actually have higher actual sensitivity at bass frequencies.

You might also consider a long tube enclosure in a corner of the room-good size, but out of the way.

Last edited by head_unit; 15th April 2010 at 07:08 AM.
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Old 15th April 2010, 08:30 AM   #4
MaVo is offline MaVo  Germany
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Old 15th April 2010, 03:57 PM   #5
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by ervinl View Post
Hi,

I just want to know is there any good, sound quality subwoofer speaker with low wattage but high efficiency (e.g. > 90db), so that I do not have to drive it with high wattage amplifier. May be just a GC amplifier or Class A SE or PP, which is usually < 60 watt RMS.

The room is only around 4x5 or 5x6 max, so no need for high wattage except good sound.

Thanks,

Ervin L
Hi Ervin,

Here is a simulation showing a high efficiency/SQ (94dB/1W/1m) T-TQWT using EminenceBassLite-S2012 driver, which when stuffed with wool to half-length of the airways path will present a high impedance load (>8 ohms) to any hooked up amplifier throughout the whole usable BW = 28 Hz-133 Hz.

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Old 17th April 2010, 03:19 AM   #6
Pashley is offline Pashley  Canada
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Your title mentions "small", we are talking about subwoofers so you need low frequencies, and you want "good sound quality" using a low-power amp. You didn't ask for high sound levels or simple construction, but you come close to wanting everything.

My guess is you cannot have all those simultaneously and you are going to have to make trade-offs. See the excellent link earlier in the thread on Hoffman's Law.

That said, there are quite a few plausible design choices. Something like a 10 inch woofer in a small sealed box with Linkwitz equalisation (Linkwitz Transform Subwoofer Equaliser) could meet all your other requirements, but it would need a much beefier amp. A transmission line design goes low and is efficient (see, for example Perfectionist Audio Subwoofer) but for bass frequencies it needs a huge cabinet. There's a link for a horn design in a earlier post. Any of those might suit you, but with trade-offs.

At least in theory, a route to high performance with low power in a reasonable-size box is a QB5 alignment (Satellites and Subwoofers). The box is designed for a distinctly humped response and there's a filter before the power amp that compensates. Looking at the tables in the above article, there are a couple of values of Qt where F3~=Fs, around Qt=.32 in Group 1 and Qt=.445 in Group 2.

Parts Express have a woofer selection guide. Speaker Building Guide Click on any parameter heading to sort by it -- most people would likely look at "sealed F3" and "sealed volume" or the corresponding "vented" numbers. If you sort on Qts, you can look for .32 or .45 to use in a QB5 alignment.

The design I came up with that way used a cheap Pioneer woofer (15" woofer) Qts=.32 so F3~=Fs=24 Hz, efficiency 96 Db 1W/1m, and only about $50 for the driver. I haven't looked, but there are almost certainly smaller woofers that could work in a similar design.

Last edited by Pashley; 17th April 2010 at 03:35 AM. Reason: minor formatting
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Old 17th April 2010, 12:39 PM   #7
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bjorno, do you have some simulations of MLTQWT going down to 20Hz and using Eminence LAB12 or 3015LF drivers?
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Old 17th April 2010, 07:08 PM   #8
vadi is offline vadi  Austria
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Bjorno kindly designed a subwoofer for me here. It's for a budget 4Ohms 10" driver. The picture shows the response and maximum SPL in 1 Pi space at 4mm displacement and 50W. I did increase the length slightly since the woofer's Fs suggests so. I haven't measured mine yet but if it's similar this box could be quite good.
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Last edited by vadi; 17th April 2010 at 07:10 PM.
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Old 18th April 2010, 03:27 AM   #9
ervinl is offline ervinl  Indonesia
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a nice graph, i think it could be cut off at 80 hz and should get nice sound started at 20hz. Actually small i ask not just diameter, but small power. if there is no small wattage but nice sound, then it means we should go for conventional one, usually around 400 watt (is not it too high for just a small room).

currently i run small wattage power amp, but class A single ended mosfet (posted in another topics), with high sens full range + tweeter and it sounds nice but i can not get deeper bass like sub. 17 watt class A is more than enough for regular room, so i wanna ask about sub if i added one.
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Old 18th April 2010, 04:13 AM   #10
kroto is offline kroto  Indonesia
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