Help in subwoofer design.

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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
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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
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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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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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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?
 
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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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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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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Hi Cal, one extreme to another, at the moment it is seriously dangerous to go outside because of the heat, 47 Celsius, I think that's 113 in Fahrenheit, cool change just arriving so will drop to a bearable 35, All my garden plants have drooped dead and the surrounds on my party system have just separated as did the Kicker 15in the shed which was waiting to move to new house.
What is your opinion on those JL 18's ??
 
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pmkierst said:
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!


You should not write off vented so easily. A well designed vented subwoofer will outperform (where it counts - bass extension) a sealed sub any day.
The best sealed subs are equalized with a Linkwitz transform.
 
Moondog55 said:
47 Celsius

10 degrees warmer than it's ever been here (officially) I've been watching them close the roof at the Australian Open because of the heat.

Sorry to hear about the drivers.

What is your opinion on those JL 18's ?? [/B]


Not familiar with it.

MJL21193 said:

The best sealed subs are equalized with a Linkwitz transform.

I think this driver would jump out of it's basket. ;)
 
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Cal Weldon said:


I think this driver would jump out of it's basket. ;)


Hi Cal,
That driver you linked above would really shine in a 150 litre vented box. Response down to 20Hz and power handling up to 500watts before over excursion. That's how I'd use it.

Linkwitz transform needs a suitable driver, Fs needs to be higher, Qts needs to be higher. Unbeatable when done right though.
 
MJL21193 said:
That driver you linked above would really shine

Hi John,
I haven't actually heard the SDX just the SD and it doesn't disappoint so I'm sure the SDX would be that much nicer. The shallow honeycomb cone is what I noticed as a departure from others. When on it's back it barely hold more than a half bag of chips. I hear the motor is a good one for linearity.

Linkwitz transform needs a suitable driver[/B]


Fair enough, my thought is that if you need the LT why are you starting with that driver? Is that primarily used with smaller drivers with big motors? It doesn't sound like it by your description but I'm asking 'cause my knowledge of the LT is quite low. It's another of them newfangled things the kids are up to these days.
 
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