Can four of 8" drivers build up a subwoofer? - diyAudio
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Old 14th May 2004, 03:36 AM   #1
Peleus is offline Peleus  Taiwan
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Default Can four of 8" drivers build up a subwoofer?

hi, guys!

I got some 8" drivers from local manufacture. Although these drivers are not famous brand, they are quite great. Here are some information of this driver:

Fo 45Hz
Qts 0.5
Frequency Resopnse 45~20000
pressure sensitivity: 92db
flux densitity: 16000 gauss
with sub cone

Yes, these drivers are full-range drivers.

Now I wonder if it is work using them to build up subwoofer (four unit per channel). I would like them produced some low frequency sound like between 35~1000 Hz.

Can it be done?

Any recommendation or suggestion will be appreciated!
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Old 14th May 2004, 03:50 AM   #2
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the JBL control1 subwoofer uses 4 8" cones in a double bandpass enclosure to achieve exactly this. I always thought it sounded a bit crap though. But it certainly can be done. Also the low frequency unit in certain KEF reference speakers uses small speakers facing inwards onto 5 faces of a cube shaped enclosure with a large port on the sixth face to let the bass out. And those sound incredible.
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Old 14th May 2004, 03:52 AM   #3
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Yes, you can use 4X of those drivers to make a SW.

Put them in an appropriately sized and tuned vented enclosure. You need speaker modelling software. You also need to know the Vas parameter for the drivers in order to run the software.

You will have to be SURE that HF energy does not get into the SW, given the full range nature of the drivers.
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Old 14th May 2004, 03:53 AM   #4
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I would say that with a an Fs of 45 Hz and a Qts of 0.5, you can get pretty flat response down to 35 Hz or so in a box that is abut six times the Vas of ONE driver.

Do you know what the Vas of one single driver is?

Also, if you arrange the speakers in a square pattern, two sets of two, like this:
00
00

your sensitivity goes up about 6 dB, to 98 dB. Pretty good deal.

Again, what is the Vas of one driver, if you have the spec?
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Old 14th May 2004, 04:11 AM   #5
Peleus is offline Peleus  Taiwan
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Thanks you guys reply so quickly!

Thanks!

I don't know of the Vas of this driver, but I can ask the supplier to get the information.

I made my decision to bluild SW using the suggestion form kelticwizard.

Can the enclosure be Onken form? If so, I can put another same dirver on the top to get mid- and hige-ragne sound.
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Old 14th May 2004, 05:11 AM   #6
Wizard of Kelts
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Quote:
Originally posted by Peleus

I made my decision to bluild SW using the suggestion form kelticwizard.

Can the enclosure be Onken form? If so, I can put another same dirver on the top to get mid- and hige-ragne sound.
I don't see any good reason not to make the enclosure Onken form at all.

If you are going to add a mid and high range, remember the dispersion pattern will be somewhat similar to a 16" driver. So try to make the crossover low-below 500 Hz, even better to cross over at 200 Hz.
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Old 14th May 2004, 11:28 AM   #7
Wizard of Kelts
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Try to get all the Thiele-Small parameters for the driver, including DC resistance.

Don't forget that if you do use a mid/tweet combo with these, the mid has to be about 98 dB sensitive as well to match. This would require either an expensive hifi speaker, or a PA speaker for the mid.

The other method is to take two 8 ohm mids of 91 or 92 dB sensitivity and run them in parallel. The two speaker unit will rate out at 97 or 98 dB sensitive at the 8 ohm voltage rating of 2.8 volts. Will explain in more detail later, if you want.

Would be very interested in knowing if your 8 inchers are 8 ohmers or 4 ohmers, and how that 92 dB sensitivity rating was achieved-at 2.8 volts or at one watt-there can be a difference.
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Old 14th May 2004, 11:58 AM   #8
sreten is offline sreten  United Kingdom
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Default Re: Can four of 8" drivers build up a subwoofer?

Quote:
Originally posted by Peleus
hi, guys!

I got some 8" drivers from local manufacture. Although these drivers are not famous brand, they are quite great. Here are some information of this driver:
Yes, these drivers are full-range drivers.

Now I wonder if it is work using them to build up subwoofer (four unit per channel). I would like them produced some low frequency sound like between 35~1000 Hz.

Can it be done?
In my considered opinion, no not really, it won't work well.

The parameters for the full range driver, especially dual cone
and top end response IMO point to extremely limited excursion.

(This is true for all good efficiency full range drivers)

For 4 drivers efficiency will be high - 98dB/W but power handling
low, and maximum SPL's in the bass extremely limited compared
to using 8" bass only or bass/mid only units.

The endeavour only makes sense if driving power < ~15 watts.

sreten.
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Old 14th May 2004, 12:55 PM   #9
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I have to agree with sreten on this one.
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Old 14th May 2004, 01:45 PM   #10
Peleus is offline Peleus  Taiwan
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hi, Kelticwizard,

I very appreciate your reply.

Today, I got the Vas of this driver and it is 60 around, and the supplied didn't sure the Vas. So, It may not be correct!
The resistence of this driver is 8 ohm, but I didn'g know the DC resistence. As usual, I can ask the supplier.

In my original plan, I will use these 10 full-range 8" drivers to build a loudspeaker. Now I used them to build a open-baffle form loudspeaker and 5 units per channel. The size of baffle is 100cm X 160cm. The speaker now I used is not only quit big but also getting almost no low frequency sound. I check fomula of open-baffle form and found if I need the 40 Hz around sound, the size of baffle will need 2 Meter aquare! That is too huge to build and use. And, most important, my wife will kick me off if I put them in the living room!

So, The ten dirvers are only what I have, and no more budget to buy new ones. If I use four units to build SW, then I got only one for Mid- and High-range. One friedn of mine try to build LS with this driver and Altec 515 B and comment "May not need the mid-range drivers!"

Any suggestion?



Hi, Sreten, thanks for your comments!

Due to the limited budget, I have to use these drivers as well as I can, although they are full-range. One point, I believed, could be a good reason for building SW with this unit. That is high flux densitity, 16000 gauss! May be I am wrong! But I think this point make the unit to produce good bass! My ideal bass is deep and fast!

About the Amp, I will build a se tube amp for the SW, using 5965 DC 6528, or 6C45PE DC 300B. This kind tube amp will produced very dynamic sound. In my personal impression, this kind amp make music kind "fast", coming soon and stop soon.
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