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Old 15th April 2004, 12:41 PM   #1
daniels is offline daniels  Denmark
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Default Subwoofer with ScanSpeak

I have got four 7" ScanSpeak 18W8546-00 woofers and I would like to make two subwoofers (left+right side) but I have some problems figurering out how to make the subwoofers so they will play as low (Hz) as possible.

www.d-s-t.com/scs/data/18w_8546-00a.htm

I have tried a lot of software simulations but I am not well experienced in constructing loudspeakers so they do confuse quite a bit.

Does anyone have some suggestions for two subwoofers, each with two 18W8546-00 woofers?

And what about the crossover?
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Old 15th April 2004, 08:23 PM   #2
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They're not my first choice for "subwoofers," but if you already have them...
Having such a low Qts (0.19) you'd definitely want them in a vented box. Play around with WinISD.
As for the x-over frequency, these should go higher than your typical "subwoofer." If you plan to have them as stand-alone subs, however, don't cross too high or you can easily localize them. 80 Hz would be ideal but 100 Hz (or even a bit higher) should be fine.

Hope this helps.
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Old 15th April 2004, 09:08 PM   #3
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OK he is using stereo subs so locational problems are not anywhere near as important. If the subs are close to the main speakers you can cross over much higher without any localisation.
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Old 15th April 2004, 10:35 PM   #4
daniels is offline daniels  Denmark
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They would not be my first choice as subwoofers, but I have had them lying around for a year now and now I want to make some use of them.

I did consider integrating the two subwoofers with my existing loudspeakers by placing my current loudspeakers (small 2-ways) on top of the new subwoofers making it into a 2,5 or a 3-way system.

But would a closed cabinet of 30-40 litres be enough? Perhaps with a linkwitz-grainer combination to add some "sub" to the woofers?

If I am going to make a vented cabinet I propably have to use an isobaric soulution because of space requirements.
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Old 16th April 2004, 08:45 PM   #5
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Quote:
Originally posted by 5th element
OK he is using stereo subs so locational problems are not anywhere near as important. If the subs are close to the main speakers you can cross over much higher without any localisation.

I did realize this; that's why an X-over of, say, 110 Hz is still acceptable IMO...otherwise I'd opt for not much higher than 80 Hz.

daniels,

I haven't modeled, but I think a sealed box for these woofers would yield a quite high F3 and are not acceptable for subwoofer duty.
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Old 16th April 2004, 10:01 PM   #6
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Quote:
originally posted by daniels
I did consider integrating the two subwoofers with my existing loudspeakers by placing my current loudspeakers (small 2-ways) on top of the new subwoofers making it into a 2,5 or a 3-way system.

But would a closed cabinet of 30-40 litres be enough? Perhaps with a linkwitz-grainer combination to add some "sub" to the woofers?
This is what I`d do!

Quote:
originally posted by coolkhoa
I haven't modeled, but I think a sealed box for these woofers would yield a quite high F3 and are not acceptable for subwoofer duty.
Thats right - at least without electronic help of a Linkwitz transform but with a Ot of 0.19, 7" drivers in a vented box IMO isn`t a good solution for sub application either.
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Old 17th April 2004, 09:17 PM   #7
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Quote:
Originally posted by cocolino

Thats right - at least without electronic help of a Linkwitz transform but with a Ot of 0.19, 7" drivers in a vented box IMO isn`t a good solution for sub application either.

Sorry, I didn't read carefully...daniels did consider a Linkwitz transform.
I suppose that would work then.
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Old 17th April 2004, 11:13 PM   #8
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The linkwitz transform circuit can also put large demands on woofer excursion so your max SPL may be limited with them.
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Old 17th April 2004, 11:36 PM   #9
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Quote:
The linkwitz transform circuit can also put large demands on woofer excursion so your max SPL may be limited with them.
The Scan Speaks are high max. linear excursion drivers. Two of them (per channel) can take quite a bit SPL on low frequencies when the Linkwitz transform is adjusted "reasonable".
Moreover, when the LR circuit is adjusted for low Q (0.5) this also helps to keep X-max. within reasonable limits.
The loss in level in the lower frequency spectrum due to the low Q alignment is equalized because of room gain in most cases.
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Old 18th April 2004, 01:18 AM   #10
daniels is offline daniels  Denmark
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So I could get an okay result if I combine the stereosubwoofers with a Linkwitz circuit in a 2,5-way combination with my small loudspeakers?

It is not 110db at 20Hz I am looking for. I am much more interrested in improoving the midrange and add a quick dynamic (but not abyss deep) bass.

From what I can read from the replies so far, It is not entirely impossible for me to reach that goal.... Right?
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