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Author Topic: 21" Cones - Why Not?  (Read 8520 times)

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21" Cones - Why Not?
« on: October 13, 2004, 07:59:28 pm »

I see a lot of people using single and dual 18" boxes. It's like the industry standard or something, for pro sound companies to have a large inventory of dual-18" enclosures. But what I'd like to know is, why aren't 21" woofers like this one (see picture) in wider use?

P-Audio SD-21 http://www.paudio-europe.com/products/foto/foto_sd-21.jpg

This has a 6" Voice Coil (!) and extends down to 30 Hz. It also handles 1000w per driver RMS, 2000w max. A dual-12" cabinet could handle 4000 watts with just one unit.
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Dietrich Sider

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Re: 21" Cones - Why Not?
« Reply #1 on: October 13, 2004, 11:30:52 pm »

Any product decision in Live Audio will be made for the following reasons (not necessarily in order of importance): size and weight, cost, reliability, performance.

Why aren't 21" drivers used more often for subwoofers?

1) size and weight - 21" loudspeakers are HEAVY and need a bigger, stronger box - this impacts load crew and truck pack. The  one you show from P-Audio weighs in at 68 lbs just for the driver - about double the weight of most 18" speakers

2) they cost significantly more than the 'industry standard' 18" drivers or boxes.

3) reliability? couldn't tell you as I've never owned one - maybe someone else has some facts and figures or a personal experience. I would have to say though that they have yet to prove themselves in the market.

4) performance - I've heard several people argue that 21" subs are not the nicest sounding boxes - they lack clarity or punch. Sure, they go low, but they don't give the sound that most live audio engineers are looking for.

There ya go . . . Very Happy
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Graeme Goodacre [Centauri

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Re: 21" Cones - Why Not?
« Reply #2 on: October 14, 2004, 08:03:12 am »

Would echo dsider's comments and add that this particular speaker mentioned doesn't model very well either.  Doesn't seem to like going low in any cabinet and its 5mm Xmax limits it to about 300W at 30Hz.  Maximum output is around 115dB at 30Hz - would do better with a Labsub with less power and less $ outlay...

You also mention 18s as "industry standard" - this only comes about from the thinking that "bigger must be better (deeper)" and is actively encouraged by speaker manufacturers marketing departments.  EAW's top performance sub uses 12s....

Cheers
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Mike {AB} Butler

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Re: 21" Cones - Why Not?
« Reply #3 on: October 14, 2004, 11:45:50 am »

BHFProfessional wrote on Wed, 13 October 2004 16:59

I see a lot of people using single and dual 18" boxes. It's like the industry standard or something, for pro sound companies to have a large inventory of dual-18" enclosures. But what I'd like to know is, why aren't 21" woofers like this one (see picture) in wider use?




Simple answer. Transient response. An 18" woofer is commonly considered the largest size woofer that will effectively reproduce transients. The larger the cone surface area, typically thicker material is required to make the cone rigid enough to withstand the immense push of the voice coil.
EV had their 30" woofer 20+ years ago (Mitsubishi and possibly others had King Size woofers as well), and it put out some IMPRESSIVE low end. But no punch. Notice it isn't widely used or available anymore?
It IS possible that through new materials that these guys have overcome this issue - but I don't believe it..
Regards,
Mike
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Jim Brooks

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Re: 21" Cones - Why Not?
« Reply #4 on: October 14, 2004, 12:40:45 pm »

I'm not saying I'm into 21" speakers,
But there is an awful lot of
Turbosound TSW-21 cabinets out there
for something that 's not supposed to work so well.

Just a thought,
Jim Brooks
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John Roberts {JR}

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Re: 21" Cones - Why Not?
« Reply #5 on: October 14, 2004, 02:03:52 pm »

21" will work OK within their bandpass but you will probably use another smaller woofer above them.

JR
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Mikael Holm (the old one)

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Re: 21" Cones - Why Not?
« Reply #6 on: October 14, 2004, 07:14:41 pm »

JR wrote on Thu, 14 October 2004 21:03

21" will work OK within their bandpass but you will probably use another smaller woofer above them.


Up to 150Hz w/ Flashlight and 180Hz w/ Floodlight. OTOH Turbo recommend TSW-718 (double 18") w/ Floods because of the upper limit of the bandpass horn.

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Mikael Holm (the old one)

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Re: 21" Cones - Why Not?
« Reply #7 on: October 14, 2004, 07:18:05 pm »

jbrooks wrote on Thu, 14 October 2004 19:40

But there is an awful lot of
Turbosound TSW-21 cabinets out there
for something that 's not supposed to work so well.


I remember seeing a figure of over 3000 Turbosound Flashlight TFS-780H sold so there must be AT LEAST 3000 TFS-780L boxes laying around somewhere. Add to that the sister box TSW-721 (without flyware) and we are counting some huge numbers of 21" drivers being in use today.

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Tim Padrick

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Re: 21" Cones - Why Not?
« Reply #8 on: October 14, 2004, 09:16:50 pm »

Quote:

Mike AB wrote on Thu, 14 October 2004 10:45
Simple answer. Transient response. An 18" woofer is commonly considered the largest size woofer that will effectively reproduce transients. The larger the cone surface area, typically thicker material is required to make the cone rigid enough to withstand the immense push of the voice coil.
EV had their 30" woofer 20+ years ago (Mitsubishi and possibly others had King Size woofers as well), and it put out some IMPRESSIVE low end. But no punch. Notice it isn't widely used or available anymore?
It IS possible that through new materials that these guys have overcome this issue - but I don't believe it..
Regards,
Mike


Nope.  The rise time of the signals produced by subs is very long (in other words, the signals are "slow").  Driver speed is just not an issue.  If subwoofer 'A' "sounds faster" or "has more punch" than subwoofer 'B', it is almost certainly because of one of the following:

'A' is producing more distortion than is 'B'.  The distortion products are more audible than the fundamental frequency.  Most PA subs are junk - 40Hz in at a decent level gives as much 80Hz and 160Hz out as 40Hz out.  (Many Hi-Fi subs aren't a lot better.)

'A' has better phase/time alignment to the rest of the system than does 'B'. Owing to the various box designs and the crossover and EQ filters, subs require that the top boxes be delayed to the subs to align the boxes properly.  (My subs are front loaded, and I have to delay the tops 12.5 feet to line them up.  It makes quite a differenc.)

'B' has a badly tuned port (or a badly designed horn) and is resonating excessively (it is 'ringing' or has a lot of 'overhang').



Scott Shaw

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Re: 21" Cones - Why Not?
« Reply #9 on: October 14, 2004, 11:19:21 pm »

While I'm certainly no expert on this subject, or any other in pro sound, I would think the mechanical damping of a speaker that size would be a factor. I prefer 10's over 15's or 18's on my bass rig because of their abilty to produce very tight response. Each speaker size seems to have it's own characteristics.

Scott
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