$500 Subwoofer? - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 29 Old 01-23-08, 08:14 PM
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Re: $500 Subwoofer?

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brent_s wrote: View Post
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
Brent,
I plugged in your numbers and am not seeing anywhere near the same response. I am using the latest WinISD and the parameters are taken directly from PartsExpress' CLIO data:
Qes .420
Qms 3.91
Fs 27.76
Vas 43.38 l
Re 3.4
Dd 250.0 mm
Xmax 12mm
Pe 700

For the DVC 15 passive radiator (part 295-194) I have:
Vas 10.6l
Fs 18.5
Xmax 22mm
Qms 5.40
Sd 805 cm^2

Really odd thing here is adding mass to the driver is just going to make Fs lower. Also, how do you add 700g (greater then 1lb) do a passive radiator?

I get 97.3db @ 20Hz and frequency response is dropping like a rock at 20hz (second "knee" in the curve). This is the "Maximum SPL" curve.

By the way it looks like Rythmik is selling SVC 12" TC drivers for ~160 shipped :
http://cgi.ebay.com/12-hi-SQ-high-ex...ayphotohosting

Xmax of 1.4"

I modeled this driver vented in 2.3^ft tuned to 21.5Hz and it looked like it could be very nice in-room. ~9db down at 20Hz. Vent length would require a bend.

Last edited by eyekode; 01-23-08 at 08:36 PM.
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post #22 of 29 Old 01-23-08, 08:35 PM
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Re: $500 Subwoofer?

Ah, never mind on the adding mass thing. I RTM from PartsExpress

Last edited by brent_s; 01-23-08 at 09:13 PM. Reason: language rules
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post #23 of 29 Old 01-23-08, 09:16 PM
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Re: $500 Subwoofer?

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By the way it looks like Rythmik is selling SVC 12" TC drivers for ~160 shipped :
http://cgi.ebay.com/12-hi-SQ-high-ex...ayphotohosting

Xmax of 1.4"
That's "peak-to-peak" Xmax. One way would be .7" or 18mm.

-Brent
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post #24 of 29 Old 01-23-08, 09:23 PM
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Re: $500 Subwoofer?

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Ah, never mind on the adding mass thing. I RTM from PartsExpress
So your model is closer now? My T/S numbers for the 315-HO are slightly different since I probably entered them before PE published the CLIO numbers and never bothered to update my driver database. Main difference appears to be that I used a slightly larger Sd based on estimating D=10" before CLIO data measured D=250mm=9.84".

-Brent
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post #25 of 29 Old 01-23-08, 09:33 PM
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Re: $500 Subwoofer?

How would the RSS315 and the TS/Rythmik compare? Beyond the increased X-max is there any other benefits?
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post #26 of 29 Old 01-23-08, 09:49 PM
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Re: $500 Subwoofer?

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brent_s wrote: View Post
So your model is closer now? My T/S numbers for the 315-HO are slightly different since I probably entered them before PE published the CLIO numbers and never bothered to update my driver database. Main difference appears to be that I used a slightly larger Sd based on estimating D=10" before CLIO data measured D=250mm=9.84".

-Brent
Nope, my model is not any closer. I just now understand how to physically add mass to a passive radiator .

I was wondering about that Xmax, it seemed to high.

Note however that I am a newby at this and I would trust your result better then mine. There is no telling what a green user will do with software!
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post #27 of 29 Old 01-23-08, 09:59 PM
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Re: $500 Subwoofer?

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happy wrote: View Post
How would the RSS315 and the TS/Rythmik compare? Beyond the increased X-max is there any other benefits?
When I plugged in the numbers it looks like the RSS315-HO will be happier in a smaller box then the Rythmik (TC?). But the Rythmik looks ok to me in a relatively small 2.4ft^3. And the Rythmik plays a little lower.

One thing that scares me about the Rythmik is the low Re. I wonder if this is going to be tough on an amplifier.
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post #28 of 29 Old 01-23-08, 10:26 PM
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Re: $500 Subwoofer?

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eyekode wrote: View Post
Nope, my model is not any closer. I just now understand how to physically add mass to a passive radiator .

I was wondering about that Xmax, it seemed to high.

Note however that I am a newby at this and I would trust your result better then mine. There is no telling what a green user will do with software!
No guarantees on my work just because I've been doing this for a few years, but I do tend to double/triple/Six Sigma check my work before publishing it for the world to se.

That said, I just changed my 315HO/DVC15PR model on the fly to use the CLIO numbers. I actually gained almost 0.5dB at 100hz. 20hz might have lost 0.1dB.

If you added mass to the 315HO, you not only lowered Fs, but decreased efficiency. The mass only gets added to the PR.

Need to go to bed, but we can discuss more tomorrow to determine the differences, if you'd like.

-Brent
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post #29 of 29 Old 01-23-08, 11:11 PM
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Re: $500 Subwoofer?

I'm weighing in a bit late on this, but subjectively I like my Rythmik 15 servo. You can find some info about it here WAF limited Sub System .

I know that when I tested it in my 3,500 cu. ft. room it was flat to 18hz, and I thought I had posted the graphs, but I couldn't find them. If I get motivated perhaps I will test and calibrate the sub again, posting the graphs this time.

Paul
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