$500 Subwoofer? - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 29 Old 11-03-07, 08:49 AM
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Re: $500 Subwoofer?

Their sealed kits are servo. I still think that the sealed servo 15" kit would be pretty close to what you are looking for. As I said before I don't know of anyone that's actually built a ported, servo controlled rythmik kit, but their site seems to suggest that it is feasible. I just thought that it sounded interesting.

Have you read through Illka's test threads? He's got a review of a 12" rhythmik kit(not to mention a ton of other options).
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post #12 of 29 Old 11-03-07, 12:01 PM Thread Starter
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Re: $500 Subwoofer?

No, I haven't been on here or looking at subs in a while so haven't gone through his stuff. Thanks for the reminder.
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post #13 of 29 Old 11-03-07, 08:14 PM
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Re: $500 Subwoofer?

The PE sealed sub boxes come in 2 ft^3 and 3ft^3 versions and have been used successfully with the Rythmik kits.

You can get solid anechoic 20hz output with either of the Dayton 12" Reference Series drivers in ported boxes. Regularly about $130, frequently on sale. PE's running a free shipping promo thorugh January. The 12" HiFi in 3 - 4 ft^3 tuned to 20hz with the BASH 300 ($130 or less) is a hard value to beat, IMO.

Download a copy of WinISD Pro or Unibox and start modelling to see what strikes your interest.

-Brent
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post #14 of 29 Old 11-03-07, 10:23 PM Thread Starter
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Re: $500 Subwoofer?

Looking at Illka's measurements of the 12" Rythmik Sealed Servo sub, it actually doesn't look like the best choice for trying to reach 20Hz because it's about -10dB at 20Hz. The Hsu VTF-3 or SVS PB12 look like better options.

I think at this point, I'm going to wait a little bit before figuring out what to do, and keep looking around. Thanks for all the feedback though.
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post #15 of 29 Old 11-03-07, 11:28 PM
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Re: $500 Subwoofer?

That's about as good as it's going to get for a single 12" driver in a sealed box. Ultimately, SPL is a function of displacement. If you look at Illka's frequency response graph, he rates it +/- 3 down to 14hz or so at a 95db drive level. 95db is pretty close to the displacement limited output of that driver at 20hz. You must be getting the -10db number using the compression testing where at higher frequencies he got as much as 105db. Also, Illka's measuring at 2m ground plane, IIRC. Boundary reinforcement, not to be confused with room gain, will give you a theoretical max of +6db per boundary (wall). Somewhere, you mentioned this was a bedroom...how close will you be sitting...you also gain/lose 6db from halving/doubling distance. So, at 2m, corner loaded in room, you could be looking at 117db at 20hz...even the 95db 2m ground plane would qualify as more than moderate SPL in my book, with my typical listening levels only measuring 95db peaks. I don't think I've seen a bedroom where the Rythmik shouldn't produce more than adequate 20hz output..at least not one where someone would be limited to a $500 budget.

Ed also use 2m ground plane measurements in the UFW-12 review, measuring 93db @25hz and 102 @30hz. The Rythmik has slighly more output at 20hz than the UFW at 25 while using a box half the size and less than half the amplifier.

I'm not trying to convince you to buy Rythmik, but I think you might be interpreting the numbers incorrectly. The Hsu and SVS are certainly excellent products, but they're much larger and produce considerably more than moderate SPL while also exceeding your stated budget. All IMO of course.

-Brent
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post #16 of 29 Old 11-04-07, 12:19 PM Thread Starter
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Re: $500 Subwoofer?

Ah, perhaps that is how I am interpreting the numbers incorrectly. I guess I need to see frequency response graphs at different SPL levels to see the correct picture. Did I look in the wrong place? Are those graphs somewhere else? I seem to recall Illka having those types of graphs before.
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post #17 of 29 Old 11-04-07, 02:08 PM
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Re: $500 Subwoofer?

The first graph is the frequency response graph. Per his explanation of measurements, it was made with a nominal 90dB drive level. The Rythmik's 2m 90dB sweep is essentially flat down to 12.5 hz. Pretty impressive for such a small box.

The second graph is maximum sustained output, starting with the 90db baseline and increasing drive level by 5dB with each sweep until power compression was clearly evident. From reading the explanation, I'd say it's much more punishing on a driver than anything you're likely to do with real world content. You can see what I presume is the Servo doing its thing as the 20hz output stops increasing around 95-96ish dB, but higher frequency output keep increasing for the 100/105 sweeps. With a 105dB peak output at higher frequencies, but 20hz limited to 95ish, I can see where you'd say it was 10db down at 20hz according to that graph...but that is relative to a 50hz drive level of 105dB. And it's all ground plane, etc. 20hz response won't be -10dB down at all drive levels.

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post #18 of 29 Old 11-04-07, 02:31 PM
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Re: $500 Subwoofer?

Just some quick back of the envelope scratching, but here's another $500ish DIY option...well $514 according to my shopping cart at PE. Free shipping currently at PE.

Get the 3 ft^3 finished subwoofer cabinet, the DVC15 passive radiator, RS315-HO, and BASH 300. Add 700 grams to the PR for a 21hz tuning based on a 2.5 ft^3 net box after driver/PR are added. If I've over estimated the displacement of the driver/PR, then more net volume will just lower the tuning for an overal improvement. This will most likely require a separate cabinet for the amp since the internal brace in the PE cabinet looks to only allow room for the driver/PR.

WinISD predicts 105.5dB @ 20hz, 1m groundplane...or 99.5dB if you subract 6dB to approximate Ed/Illka's 2m measurements. Relatively flat at that level all the way up to 108.8dB @ 100hz @ 1m. The 1m output is still good for 95dB @ 15hz. Overall, output at 20hz is comparable to the Rythmik and a little less at say 50hz, but the DS12 kit would be around $565 if used with PE's 2 ft^3 sealed cabinet.

-Brent
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post #19 of 29 Old 11-04-07, 07:00 PM Thread Starter
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Re: $500 Subwoofer?

I was looking at the chart of subwoofers compared with just their SPL numbers listed, so obviously I was looking at the wrong stuff.

Thanks for the PE kit suggestion. I guess I just have to see what I'm going to get around to doing now.
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post #20 of 29 Old 11-05-07, 12:55 PM
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Re: $500 Subwoofer?

You may not be concerned about SPL but going to a 15" will help the quality of bass. Being as a 15" isn't working nearly as hard as the same design 12" distortion will be lower. This isn't theoretical btw. Besides the 15" model is typically very little more considering how much more you get for the money. Just a thought.
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