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Old 2nd June 2009, 12:02 AM   #1
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Default Good sub

hello I am in the initial stages of designing my first speaker which shall be a nice 8ohm powered sub with a filter to extend the bass response (I think this is called a Linkwitz circuit in the speaker world). Anyway I was thinking about this driver:
http://www.rapidonline.com/netalogue/specs/35-2932.pdf

For an enclosure I was planning on a closed cubic aprox (haven't calculated anything yet) 35L box made of 18mm MDF with box joints and some sort of internal bracing structure.

the driver has a lf cuttoff of about 40Hz and -12dB/octave slope below this turning point. Therefore is aiming for response down to 20Hz realistic? (for flat program matirial this seems to limit me to 7W peaks...). Could I overcome this by using more drivers (and suitibly monster amp), or is there a more elegent solution.

I would like the extended bass response however as I like Albinoni's Adagio in G minor alot.
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Old 2nd June 2009, 12:39 AM   #2
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That woofer works in an Open Baffle but i don't think you can get down anywhere close to 30Hz using it, the advice given to me when I started was that OB speakers do not have much below 40Hz.

One of my favourite pieces of music, needs good clean bass reproduction to do well.

How big is your room??
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Old 2nd June 2009, 01:04 AM   #3
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room will be typical living room, haven't sorted out house for next year yet so can't be more specific. I'm not sure if open baffle is suitible as this is a student house and durability is an issue.
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Old 2nd June 2009, 01:10 AM   #4
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Its big advantage is its price, one of Visatons cheapest woofers, when you say durability do you mean from the power handling or furniture sense?? OB speakers can't handle too much power but as furniture no better or worse that your skills as a chippie will make it
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Old 2nd June 2009, 06:32 AM   #5
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I have done a similar project to this, but with 2x 8" Dual Voice Coil woofers from Dayton, with a Linkwitz circuit. -3db at 28Hz. And still enough headroom for a reasonable all-house party (not a particularly big house - 10m by 10m)

I could get you a schematic of that if you are interested.
two 8"s in a box... is the thread,
If you want to keep it as your own work, I recommed this driver. You can order them from CPC, but this site has the tech specs.

http://cpc.farnell.com/LS00415/audi...branded-55-1455

http://mcmelectronics.com/product/55-1455 - that has the specs and reviews.

Gotta go - school soon.
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Old 2nd June 2009, 09:27 AM   #6
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thanks for the replies. I am now not sure if this driver is suitible as using the spreadsheet here:
http://www.diysubwoofers.org/sld/

It apears I ethier have a huge box (1m^3) or rubbish freq response. The problem apears to be its high Fs and high Qts.

*I think I misunderstood open baffle is this what is ment:
http://www.linkwitzlab.com/proto.htm#PW1

If I could obtain the bass exstension from this configuration it would be ideal as the actual sub would be small in volume (It has to fit in a car boot for transportation).
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Old 2nd June 2009, 09:59 AM   #7
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High Qts usually means very big box, the Linkwitz page shows a top-of-the-line OB woofer arrangement, you could copy that sort of backless box.

But they will be woofers not sub-woofers ( they won't reproduce infrasonic sound)
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Old 3rd June 2009, 08:20 AM   #8
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Thanks for the replies, I think this driver may be more suitible with its F0= 33.5Hz and Qts = 0.52.

http://www.rapidonline.com/netalogue/specs/35-1415.pdf

(It also seems to have quite good results with only a 35L box according to the datasheet).
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Old 3rd June 2009, 10:21 AM   #9
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With no specs on Xmax, means it could be anything and wild a shot in the dark
But high Fs, high Qts, low SPL
Hard to say what driver that is without knowing more
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Old 3rd June 2009, 06:03 PM   #10
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hmm but Xmax only effects the maximum SPL? I am not too bothered about this due to not having huge rooms (and curently upgrading from water damaged mission audio "monitors" from the 80's). (which have a very low max SPL)

I tried to find what brand the sub is but apears to be some OEM job that just gets rebranded everwhere, it's cheap though.

I checked the freq response graph they give and it seems realistic for a 35L closed box, I will have to apply a fair bit of equalisation but this is fine as I the eventual system will use an FPGA based equaliser that samples the actual frequancy response at the listening position and adjusts itself and has a GUI etc for creating a custom frequancy response (FPGA's are fun). Before I do that I guess I will use a passive network for equalisation
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