Subs @ 30 for an install

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Re: Subs @ 30 for an install

Peter Morris said:
Ramsdell Pro Audio - Products - Sub Woofers - The Sub Engine


P.Audio SD21 21" woofer - The P.Audio SD21 is a 21" speaker for subwoofer speaker systems. P.Audio SD21 21" woofer here at US Speaker.
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But wasn't it XS-21 Chimera 21" Bass Horn - Ramsdell Pro Audio Products that was referenced, which is a different product (although it may use the same driver)?

I'd definitely like to see more information such as whether the sensitivity, response and maximum output are based on whole space or half space conditions and a response curve that might also help determine whether the stated sensitivity and output are the overall output over some bandwidth, the peak over some bandwidth, the minimum over some bandwidth or what. Since the stated 140dB maximum output, assumed to be at 1m since that is not noted, does not seem to relate directly to the 108dB sensitivity and the 1,000W/2,000W/4,000W power rating it would also be nice to know how it was derived.
 
Re: Subs @ 30 for an install

Brad Weber said:
I'd definitely like to see more information such as whether the sensitivity, response and maximum output are based on whole space or half space conditions and a response curve that might also help determine whether the stated sensitivity and output are the overall output over some bandwidth, the peak over some bandwidth, the minimum over some bandwidth or what.
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Well I can at least verify that the B&C 21SW152 specifications are 100% as advertised.
 
Re: Subs @ 30 for an install

Brad Weber said:
But wasn't it XS-21 Chimera 21" Bass Horn - Ramsdell Pro Audio Products that was referenced, which is a different product (although it may use the same driver)?

I'd definitely like to see more information such as whether the sensitivity, response and maximum output are based on whole space or half space conditions and a response curve that might also help determine whether the stated sensitivity and output are the overall output over some bandwidth, the peak over some bandwidth, the minimum over some bandwidth or what. Since the stated 140dB maximum output, assumed to be at 1m since that is not noted, does not seem to relate directly to the 108dB sensitivity and the 1,000W/2,000W/4,000W power rating it would also be nice to know how it was derived.
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Yes ... but, that was the only picture where you could clearly see the driver :)~:-)~:smile:. There are very few 6 inch VC speakers that only handle1000W, and as Mark noted there are no ribs on the basket - the baskets look the same on the XS-21 and the BP -SD21 . P Audio’s new driver does much better and the basket is ribbed … the B&C looks quite different and handles more power (2000 /4000 W).

B&C SPEAKERS
P.Audio System Co., LTD
 
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Re: Subs @ 30 for an install

Peter Morris said:
P Audio’s new driver does much better and the basket is ribbed … the B&C looks quite different and handles more power (2000 /4000 W).
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Well the 21 everyone really needs has the BL of the p.audio and the power handling of the B&C. I keep waiting for it to come out. Most people that want a 21in are going to ask it to do 30 Hz. I think most of the offerings out there have upped the BL to get a higher sensitivity number at the sacrifice of LF efficiency.

P.S. I forgot to mention the extended Xmax required to do it also, without burning up the coil. Come on guys build some motors that work!!!!
 
Re: Subs @ 30 for an install

Mark DeArman said:
Well the 21 everyone really needs has the BL of the p.audio and the power handling of the B&C. I keep waiting for it to come out. Most people that want a 21in are going to ask it to do 30 Hz. I think most of the offerings out there have upped the BL to get a higher sensitivity number at the sacrifice of LF efficiency.

P.S. I forgot to mention the extended Xmax required to do it also, without burning up the coil. Come on guys build some motors that work!!!!
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there is one, it’s a little different .... http://www.bcspeakers.com/product.php?id=374
http://www.powersoft-audio.com/en/products/amp-modules/ipal.html
 
Re: Subs @ 30 for an install

Mark DeArman said:
From the pictures on their site it looks nothing like the B&C. Also doesn't look like the Celestion or the Bema. So I'm not sure.
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Yeah I guess you are right about the picture...at first I didn't look closely enough through the grill to see the basket. I just wasn't aware of other 21" drivers available with a 6" voice coil aside from the B&C, but I was just thinking out loud.
 
Re: Subs @ 30 for an install

Matt Lillie said:
The "target" I've been assigned by management is to match a rig MSI brought ...6 JBL 4881 powered with IT-12000HDs ....The 4881 claims -10dB @ 25, -3dB @ 35.
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So you do not actually need what you originally asked for in your first post. You just need a high quality sub with good extension into the 30's. Big difference. I think there are lots of options that would do the job.
 
Re: Subs @ 30 for an install

Glad to see the Ramsdell "Chimera" series getting the attention it deserves. The 21" version does what a lot of the modern music needs. I've only heard them with the P-Audio 21 in them powered by Xti type Crowns. The real magic would be when you get bigger better amps and upgrade to that B&C 21. (I think that was the one that they had there but it got returned before they could test it in a Chimera type cab.)
 
Re: Subs @ 30 for an install

Jeff Babcock said:
So you do not actually need what you originally asked for in your first post. You just need a high quality sub with good extension into the 30's. Big difference. I think there are lots of options that would do the job.
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Semantics, I suppose. I didn't say "MUST BE FLAT FROM 30-120Hz, +/- 1db full space with calculated max output of 132.5db". An honest 30, yes. I suggest an "honest 30" is a slightly different way of saying "good extension into the 30's. The JBL spec, -10dB @ 25, -3dB @ 35 certainly qualifies in my mind. Which is why I also mentioned I know there are plenty of road boxes that can get there, or something like that. Then again, my mind is always in several places at once so stuff that makes sense to me could be complete gibberish to anyone else.... I currently have six windows open, three programs running, and am writing a spec for another install in Word. And I should be on the phone, too. Why am I here? Taking a break, I guess. I want to go back on vacation, where I could only get phone and net when the wind was blowing just right! :^)
 
Re: Subs @ 30 for an install

Loren Jones said:
Well, the B&C driver does have 60% greater Xmax compared to the 21" drivers on the P-Audio website.
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Yeah and the B&C has a really good 'sound' to it when when loaded in a proper cabinet. But if you look at all of the B&C offerings with their new big neo motor, the 15, 18 and 21in models, the increased BL has significantly rolled off the LF. That's all I was saying. There is no reason with proper processing you can't compensate for the effect.

I see people ripping on manufacturers for posting DSP settings with the LF boosted but there is really little else you can do if you decide to go with a high BL speaker to up the efficiency. I'm not totally sure if I agree with that as a solution because it starts to cause all sorts of dynamic range problems farther up the signal chain (from the speaker). But if you can make it work.

Gene Hardage said:
The real magic would be when you get bigger better amps and upgrade to that B&C 21. (I think that was the one that they had there but it got returned before they could test it in a Chimera type cab.)
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I really don't think that would work well without changing the cabinet. You definitely wont get the same frequency response from the box with increased output. But who knows, maybe it would be better.
 
Re: Subs @ 30 for an install

Matt,

When you were on vacation, you complained about not having enough access to this place!

P.S. An cabinet that can do 30Hz should do it at -3dB from rated sensitivity or better, IMHO. Otherwise, what are we comparing?
 
Re: Subs @ 30 for an install

Bennett Prescott said:
Matt,

When you were on vacation, you complained about not having enough access to this place!

P.S. An cabinet that can do 30Hz should do it at -3dB from rated sensitivity or better, IMHO. Otherwise, what are we comparing?
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I know, Bennett! Now I want to go back on vacation! Permanently, of course. Two weeks was too long, I'm still catching up as well as dealing with current stuff.
I surely could have explained my target goal better, see my above reply to Jeff. You know I know better, but stuff happens
 
Re: Subs @ 30 for an install

Mark DeArman said:
Yeah and the B&C has a really good 'sound' to it when when loaded in a proper cabinet. But if you look at all of the B&C offerings with their new big neo motor, the 15, 18 and 21in models, the increased BL has significantly rolled off the LF. That's all I was saying. There is no reason with proper processing you can't compensate for the effect.

I see people ripping on manufacturers for posting DSP settings with the LF boosted but there is really little else you can do if you decide to go with a high BL speaker to up the efficiency. I'm not totally sure if I agree with that as a solution because it starts to cause all sorts of dynamic range problems farther up the signal chain (from the speaker). But if you can make it work.



I really don't think that would work well without changing the cabinet. You definitely wont get the same frequency response from the box with increased output. But who knows, maybe it would be better.
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So Mark,

How does the high BL roll off the LF? Based on your posts here it is obvious you know your way around this stuff. Just trying to learn...

Loren
 
Re: Subs @ 30 for an install

Loren Jones said:
So Mark,

How does the high BL roll off the LF? Based on your posts here it is obvious you know your way around this stuff. Just trying to learn...

Loren
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It happens because as you increase BL you make the dynamic system (the speaker) over damped. This has some real advantages and disadvantages depending on what your trying to do with the speaker/enclosure system. John Vanderkooy had a really good summary paper on the subject about 10 year ago.
I'll put the link in here
AES E-Library » Direct-Radiator Loudspeaker Systems with High Bl

Attachment is a plot from the paper. Moderator can delete it if in violation.
 

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  • BL.jpg
    BL.jpg
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Re: Subs @ 30 for an install

Brad Weber said:
But wasn't it XS-21 Chimera 21" Bass Horn - Ramsdell Pro Audio Products that was referenced, which is a different product (although it may use the same driver)?

I'd definitely like to see more information such as whether the sensitivity, response and maximum output are based on whole space or half space conditions and a response curve that might also help determine whether the stated sensitivity and output are the overall output over some bandwidth, the peak over some bandwidth, the minimum over some bandwidth or what. Since the stated 140dB maximum output, assumed to be at 1m since that is not noted, does not seem to relate directly to the 108dB sensitivity and the 1,000W/2,000W/4,000W power rating it would also be nice to know how it was derived.
Click to expand...
One of the "interesting" things of note in the specs is the sensitivity number stating the use of pink noise.

It also says 1watt. How is the 1 watt calculated/measured? Since pink noise has a crest factor (6-8-10dB are very common). So assuming a 2.83V at 8 ohms=1 watt, what is the voltage actually used is it some sort of average or a peak or the continuous etc? What were the settings on the SPL meter-slow? fast? peak? etc You can get very different numbers based on the speed of the meter.

I have started doing a "comparison" between different loudspeakers (by different manufacturers) using a common method to all.

My standard voltmeter is the old analog HP 400e. When viewing normal pink noise on this meter-the scale jumps all over the place. On a 3 volt scale-it bounces between below 2.5 volts and off scale. You can "kinda" average the readings-but it does vary. an SPL meter measuring pink noise will also jump all over the place-remember the continuous to peak ratio.

So I have started using the TEF sync pink noise. This has a different "sound" but is still 6dB crest factor-but allows the volt meter to be MUCH more steady-only varying 1-2 tenths of a volt. It also make the SPL meter stay rock solid on a slow response measurement.

Anyway-back to what I have found. The comparison is very simple. Have the TEF supply noise-and the volt meter read 2.83V (or as close as I can get it). Put the loudspeaker on the floor and the SPL meter on the floor 1 M away on unweighted response and slow. Read the number.

Yes there can be all kinds of variations-depending on a lot of variables-but it does give a good "reference" between different cabinets.

What I have found by using this method is that pretty much across the board-the SPL reading on the calibrated meter (The same calibrator is used for the SPL meter as well as the swept sine measurement of the TEF) is 2-3dB higher than the published sensitivity of the loudspeakers.

Now granted-there are all different kinds of ways to "measure with a standard input of pink noise".

All I am saying is that the same loudspeaker can have different numbers assigned to it-depending on the test procedure.

Here is what
 
Re: Subs @ 30 for an install

Bennett Prescott said:
Ivan,

While we certainly enjoy your technical exposition, please be a little more careful when doing so in the context of someone else's product.
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I wasn't commenting directly on the particular product (although it may have appeared to be that way-sorry), just that the use of a particular test procedure can produce different results.

Since I have recently started taking some "reference" measurements-using pink noise-and finding out that they don't corrilate to other more conventional methods (while being comparable to eadh other-they are consistantly reading several dB higher than other methods)-I thought it might be of interest.

I have no opinion on the actual spec numbers of those particular products-not having measured them myself-using a different method.

And products measured is different ways can produce different results-particularly in the "simple numbers" spec.

And of course-how the numbers by whatever method is used are "interrupted", is another very interesting area that people need to look at.

Of course the only way to truly compare products is to measure them both using the same method-same gear etc and then to listen to them-in the same conditions.
 
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