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Old 29th January 2009, 08:23 PM   #1
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Default Help in subwoofer design.

I know you probably get a zillion requests like this, but I thank you for your forbearance anyway.

I am an experienced woodworker with a full shop. I am handy enough with electronics. I like music and appreciate good quality sound, but an not an "audiophile" in the modern sense of the word.

The Application
----------------------
The sub will be in a room about 17'x17' with a cathedral ceiling. The room is relatively live. Sub size is not a big concern, as long as it doesn't get seriously out of hand. It can (and quite possibly will) be placed in a corner.

The sub will complement a current system consisting of Infinity tower front left and rights, and a middling set of Bose back speakers (AM-3's or something) and Infinity center. Yamaha receiver with pre-amp sub out (actually 2 sub outs). Not a high end system by any means but doesn't wreck the sound.

Primary uses are Music, Home Theater and Games, but Music overrides all else; I won't sacrifice that for HT or games. It just needs to fill in the very bottom and be clean. I like electronica, house, techno, dance and a bunch of other stuff which is typically less bass demanding.

Restraints: I am trying to keep the cost sane. WW supplies are a non-issue, cost wise. I'd prefer to source the parts in Canada, much easier. I'd prefer, if possible and reasonable, to source NA or European made parts.

The questions
----------------------
The plate amp seems to be a significant cost. I presume buying a used power amp off and running it bridged would be more sensible, save lots of money and probably sound better, yes? The receiver will handle cross-over duties (and is programmable). What power range would be suitable? The couch doesn't need to dance.

So, we get to design issues.
Ported, sealed or passive radiators?
Size of driver?
Etc.

I'd greatly appreciate and direction, plans, etc.
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Old 29th January 2009, 08:58 PM   #2
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Hi, not an expert but I can get you started.

You will need a minimum of a 12" woofer.

I am guessing you like the sound of a sealed unit. (clean sound)

A plate amp is not expensive and comes with level controls and XO's and the like so in the long run you save money versus a used amp and passive XO's. It is also much more versatile in pairing with your main speakers.

Contact CSS if you like to buy in Canada. Bob Reimer is a good man to deal with.
http://www.creativesound.ca/
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Old 29th January 2009, 09:10 PM   #3
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I tend to agree with Cal here, unless you already have the spare stereo amp.

http://oaudio.com/500W_SUBAMP.html

If you do have a spare stereo amp run dual subs, much better, I like big drivers so I would have said 15 inch.
I have been looking at this Eb8 site, factory reconditioned JL car subs, perfect for a biggish sealed box, if I could afford the freight 2 of the 18's would already be on the way

http://cgi.ebay.com.au/JL-AUDIO-SUBW...742.m153.l1262
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Old 30th January 2009, 10:04 PM   #4
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I read up some and I'm sold on the sealed design; it kind of surprises me, because the diagrams often show poor response and so many other designs are ported, etc. However, my reading definitely agree with your assessment of the cleanest sound. One decision down!! Most excellent!

Note I do not need a cross over at all; I have a fully functional one as part of the receiver (yeah, I am a heathen...)

I'm not sure about a plate amp being "cheap"; it comes in at higher cost then many large drivers. Considerably more then the fairly decent amps that can come up on Kijiji. But that is not critical.


So more specific questions: How would a driver like an SDX15 be? Is it a good performer? How does one get from having a driver and basic design style to a box design? Or are there good, known, designs for that driver or similar one?
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Old 30th January 2009, 10:14 PM   #5
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When you say the XO is part of the receiver, do you mean the line out is already XO'd and that you'd just need to run another amp off of it? If so ok but make sure that's the case. My Harman Kardon has a subwoofer line level output that is full range, no XO.

When we say cheap, we mean that compared with doing a 24 dB XO with passive components it is cheap. It will cost as much as a plate amp and not give you a variable XO, phase switch and all the other goodies you get with it.

The SDX15 is a fine woofer. I just happen to own the SD version (no X) and am quite happy. The SD never went to market as the cost to build them was the same as the SDX so there was no reason to do so. I am the proud owner of a very lonely woofer as this is the only one made. Talk to Bob at CSS and he will be able to offer you some design ideas.
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Old 30th January 2009, 10:24 PM   #6
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Ok you've made one decision, and I admit ti being a "Frugalphile" myself.
Run the output of the receiver to the input of ANY stereo amp and run stereo subs.
Box design for sealed boxes is relatively easy, pick a drive "Q" to start with and as you are after quality that "Q" factor has to be 0.7071 or below and the boxes get big quickly, check the WIKI, closed box formulae should be there,
You need a driver with a low resonant frequency a fairly high Qts and reasonable power handling.
I'm not familiar with the driver you mentioned, LINK??
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Old 30th January 2009, 10:30 PM   #7
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Linkee:

http://www.creativesound.ca/details.php?model=SDX15
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Old 30th January 2009, 11:05 PM   #8
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Nice woofer
150 litre sealed box but IMO would need a little EQ, passive EQ can't be used as the Qms is too low. Love the price if I could buy hre for that price I would.
I would still go for a pair tho
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Old 30th January 2009, 11:09 PM   #9
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Nice woofer, sealed box between 100 and 150 liters, but I'd still use 2

Looking at the graph some EQ may still be needed which is where plate amps come in, the Qms on this woofer is to low to use a first order passive bass boost.

Seriously jealous of the price you blokes in the US./. Canada pay for top notch drivers
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Old 30th January 2009, 11:17 PM   #10
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Quote:
Originally posted by Moondog55

I would still go for a pair tho
There are different schools of thought. I am one who prefers a single bass driver.

Quote:
Originally posted by Moondog55

Seriously jealous of the price you blokes in the US./. Canada pay for top notch drivers
Helps us deal with the snow better.
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