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Old 13th November 2002, 12:42 PM   #11
Wizard of Kelts
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I checked the specs at the Precision Devices website. The voice coil winding is 30 mm long. The height of the magnetic gap is 15 mm long.

Linear excursion is generally found to be:
(voice coil length-magnetic gap height)/2, so in this case, the linear excursion of this speaker is (+/- ) 7.5 mm.

Most speakers can go physically farther than their linear excursion. You can generally count on any speaker having a physical maximum excursion between 1.5 and 2 times longer than the linear.

We dealt with the issue of very large woofers on a previous thread here, and quite a few members felt that when you factor in cost, etc., you are better off with 4 12" woofers rather than a 24" woofer. The cone area is approximately the same for four 12" as for a single 24".


The consensus, among people who have hooked them up, is that hooking up four speakers together yields an increase of 6 dB in sensitivity over a single speaker. So hooking four 12" speakers rated 91 dB @ 1W/1M will yield a system that is 97dB @ 1W/1M together.

There is the issue of cone breakup. Even though the Precison Devices has a huge 6" diameter voice coil, the fact remains that the edge of the cone is going to be around 19" away from the edge of the voice coil. In a 12" with a 2" voice coil, the edge of each speaker will be only 8 inches from the voice coil. The shorter the distance from the edge to the voice coil, the less the cone breakup. And cones do break up, no matter how stiff the cone material, at lower frequencies. So four 12" will give cleaner sound.

Just throwing some thoughts around that you might wish to consider.
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Old 13th November 2002, 01:06 PM   #12
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Sounds quite like my current Fane to me. It has quite
the same charasteristics than the PD driver except that it is
18 inch.

But have you looked at Tumult? It has 68 mm Xmax peak
to peak (that is linear excursion).

http://www.adireaudio.com/diy_audio/...ire/tumult.htm

Actually their claim "Tumult is simply the most displacement you can buy, period. " seems to be true since it exceeds even
the 24 inch driver because of its long excursion.
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Old 13th November 2002, 01:21 PM   #13
Wizard of Kelts
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Karoliina:

Tried checking out the Tumult yesterday but could not locate the page. Went there again today, found it and perused the page.

All I can say is: Gulp!!
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Old 13th November 2002, 02:22 PM   #14
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Just to throw some application info on the PD 24" driver in - all the Turbosound rigs I know that use them are 5-ways with the 24s doing a sort of sub-sub-bass, just to really get the trouser flapping going in big venues when you want a bit more welly than you get with 18" subs. They are rarely used over much more than an octave or two, letting the 18" subs do the rest of the bottom end.

To be honest, the 24 is probably a total overkill for home use, unless you have a living room the size of a cinema. Even the PD1850 is probably a little excessive unless you've got very understanding or vibration loving neighbours.
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Old 13th November 2002, 02:34 PM   #15
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Quote:
Originally posted by kelticwizard
Karoliina:

Tried checking out the Tumult yesterday but could not locate the page. Went there again today, found it and perused the page.

All I can say is: Gulp!!
How about using four of these?

127 dB at 20 Hz without exceeding the linear excursion
and maximum power limitation. That requires 6400 W
of amplification, but 127 dB at 20 Hz is quite loud, isn't it.
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Old 13th November 2002, 02:46 PM   #16
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Quote:
Originally posted by Redeye
Just to throw some application info on the PD 24" driver in - all the Turbosound rigs I know that use them are 5-ways with the 24s doing a sort of sub-sub-bass, just to really get the trouser flapping going in big venues when you want a bit more welly than you get with 18" subs. They are rarely used over much more than an octave or two, letting the 18" subs do the rest of the bottom end.

To be honest, the 24 is probably a total overkill for home use, unless you have a living room the size of a cinema. Even the PD1850 is probably a little excessive unless you've got very understanding or vibration loving neighbours.
Actually I have already 18 inch Fane driver that is quite similar
to the 18 inch PD. It is not even nearly enough for me.
Not a overkill. I am planning to get a subwoofer that has
a similar driver than in Velodyne HGS-18. As you know,
the Velodyne is home subwoofer. Exceeding linear Xmax
with PD/Fane type driver is easy. That results audible distortion.
If you compare it to Velodyne, it is really different. Velodyne
causes no audible distortion. It is completely clean and
deep. Velodyne has a driver that has a very long Xmax,
something comparable to Tumult. A friend of mine owns
the Velodyne and it sounds far better than my Fane, no
distortion, no problems with dynamic range etc.

And if you look at Adire Audio Tumult's specs, one 15 inch
Tumult is propably more than one 24 inch PD and it is
3.5 times more (in terms of displacement) than one
18 inch PD/Fane. I am expecting that I could do a
subwoofer from Tumult that could be directly comparable
to Velodyne's HGS series in terms of low distortion.

Guess what. I am living in a row house..... ;-)
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Old 13th November 2002, 04:16 PM   #17
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Quote:
Originally posted by kelticwizard
\you are better off with 4 12" woofers rather than a 24" woofer. The cone area is approximately the same for four 12" as for a single 24".
With even multiples of drivers you can also take advantage of push-push loading to cancel out the newtonian load the driver puts on the box.

dave

A big welcome to the forum Karolina, not many females around here. You will be a bit of a celebrity

dave
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Old 13th November 2002, 11:50 PM   #18
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Default Shake, Rattle and Roll...

If you want to crack walls, loosen ceiling panels and rattle the roof tiles, consider the Genesis-1.
With 2000W+2000W 16Hz-120Hz, at 6 metres back sitting on the couch, these will shake your head and blur your vision.
The bass line array setup works bigtime.

Another technique is the ServoDrive sub cabinet.

Eric.
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Old 14th November 2002, 01:01 AM   #19
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Default Re: Shake, Rattle and Roll...

Quote:
Originally posted by mrfeedback
Another technique is the ServoDrive sub cabinet.
Below 80 Hz there is very little that moves air as effectively as Tom Danley's servo-drive. A fallout of his development of acoustic levitation technology for NASA. You do have to buy complete units at the moment (althou some unused kits may still be loating around from when a kit was offered to BASSList members)

dave
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Old 15th November 2002, 02:31 PM   #20
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Default Re: Re: Shake, Rattle and Roll...

Quote:
Originally posted by planet10


Below 80 Hz there is very little that moves air as effectively as Tom Danley's servo-drive. A fallout of his development of acoustic levitation technology for NASA. You do have to buy complete units at the moment (althou some unused kits may still be loating around from when a kit was offered to BASSList members)

dave
I checked out the ServoDrive web site.
The Contrabass looks interesting (14 Hz cutoff point).
The bass tech 7 was
not interesting to me because of its too high 28 Hz cutoff point.
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