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Old 17th August 2012, 09:14 AM   #1
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▀art West-VL.'s Avatar
 
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Default 2 rss390hf's sealed+LT and woofer test described by Rod Elliot

Mr Elliot has this test to see if a woofer can work in a small sealed cabinet.
Did anyone actually do this test? Results?
- A good quick test is to stick the speaker in a box, and drive it to 100W or so at 20 Hz - you should see a lot of cone movement, a few things will rattle, but you shouldn't actually hear a tone. A "bad" speaker will generate 60 Hz (third harmonic) - if you don't hear anything, the speaker will work in an equalised sub.
from:Sub-Woofer Controller

I'm currently thinking about the Dayton rss390hf and using a LT from Rod Elliot.
Two drivers in a sealed cab of 400l, one driver magnet out. (f3 is at 31hz)
Any thoughts on that?
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Old 17th August 2012, 11:44 AM   #2
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I've been looking at that sub for years now.

2 drivers in a 11ft3 box makes qtc .707, The FSB=F3 is right around 30hz, and it is sealed, so it will go very low in a simple box without eq. I wouldn't bother linkwitz boosting the bass. But you might want to run a subsonic filter maybe 25hz or lower.

On the other hand using different drivers, tuning to 27hz, a sub's cone would be moving less under 40hz to tuning frequency, so it would be cleaner, go louder, and to me stop and start better, but will unload below that (back to a subsonic filter again).

Another option is the epic 12's in a small sealed box then boosting the schmoo out of it for 25hz or less operation.

I gave up on "transient response" because when I stuffed my ports (woofers used as subs), they weren't any quicker or cleaner, just 6db less bass (and that is a lot).

You are on the right track with a push pull design, regardless of sealed, ported, or tapped horn, etc.

Norman

Last edited by norman bates; 17th August 2012 at 11:46 AM.
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Old 17th August 2012, 01:06 PM   #3
breez is offline breez  Finland
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Two small sealed RSS390HF is what I have, each in its own 56 liter box. Effective volume turned out to be about 70 liters with dense filling of fiberglass. I have some old backyard measurements: Index of /~lmela/dayton

The SPL figures you can take with a grain of salt, but indicated drive levels (Vrms sine) and distortion should be quite accurate aside from noise floor and below 20 Hz data. Driven by a cheap but plentiful 2x700W proaudio amp during measurements. Results shown for one sub.

It isn't great at 20 Hz anymore, that is just physics, but down to 30 Hz I would say it has nice performance per size.

Last edited by breez; 17th August 2012 at 01:11 PM.
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Old 17th August 2012, 02:46 PM   #4
tb46 is offline tb46  United States
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Hi ▀art West-VL.

As to your question in Post #1, yes that's the test I used once upon a time, but, don't use 100W sine wave (and don't get stuck on 20Hz), it's just not necessary, and a lot of woofers do not like that much concentrated power; pick a frequency and power where you can see a lot of cone movement (and no smoke). I still have some test boxes I use occasionally, and - additionally - I will always test the driver for T/S parameters before I actually build something.

As to the RSS390HF-4:

Completed build, for inspiration..

and,

my "little" build

You may also want to think about PPSL mounting of the drivers.

Regards,

Regards,
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Last edited by tb46; 17th August 2012 at 03:06 PM.
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Old 17th August 2012, 08:29 PM   #5
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Thanks for the responses.

Someone was kind enough to mail me and said that the Dayton has some weaknesses. A weak bl and highish mms.
Even though the Dayton sims very well, the Monacor SPH-380TC, for example, would perform better because of the stronger motor and lower moving mass.

I do lean towards sealed, it's simple, low delay, 'fast'
PPSL has certainly been considered, but apparently hard to get the right configuration┐

Breez, did you consider putting the driver in a larger cab, should be 2.4 times larger then your cab's apparent volume.

[slightly irritated]Will I ever be able to decide which woofer(s) to buy!?!

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Old 18th August 2012, 02:19 PM   #6
breez is offline breez  Finland
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Quote:
Originally Posted by ▀art West-VL. View Post
Breez, did you consider putting the driver in a larger cab, should be 2.4 times larger then your cab's apparent volume.
Not really, reasonably small size was the primary design goal for my sub. The higher Q of the resonance is correctable electronically (or DSP in my case) and the loss of efficiency is not a big problem with high power amplifiers.

Distortion wise (below resonance) it may be somewhat worse than a one in a conventionally sized box, but I think I'm getting 90 % of the performance in less than 50 % footprint. Another way think about it is comparing a 1 driver in bigger box vs. 2 drivers in two smaller boxes. The 2 driver solution would always have better performance and more flexibility in placement too. Cost is of course higher. A big ported box design would surpass this solution below 30 Hz for sure.
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