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[Nathan Lehouillier]

I recently had a customer ask me if I had enough subs to do
an outdoor show for a lighting fx company unavailing.
Basically He wants to show off his new toys with audio
accompanying the show. So we set up 4 subs in his ware
house and at 50' he was very pleased with the level.
Basically he wanted earth shakers. I have 12 of these
boxes and would like to find a program that can tell
me with a decent amount of accuracy what kind of Spl
I can anticipate out of them. I have Ease 4.1 at work
but it doesn't go down lower than 125 I think. I don't
do modeling yet but will shortly that part of our business
is really booming. We also have Smart but I have never used
it . A basic calculation for free space and 1/2 space would
be great. The subs are Don Keele W's with Evx 180b's .
It seams like I am the only person running these in any
kind of number or every one else doesn't like to talk about them. I have basically taken the box sensitivity that I have seen
posted on JBL's sight 105db and went up 3db per doubling of power IE 108 2w 111 4w and arrived at RMS 133 program 135
peak 139 than I add 3 or 6db? for every doubling of boxes after that so in theory with all 12 in a stack I should be able to hit
Peak
1  139        1  139
2  142        2  145
4  145        4  151      
8  148        8  157
12  149.5      12 160
*16 151        16 163
*If I buy 4 more witch is the original design 8 per side=40hz

[John Halliburton]

I would recommend this article over in the Study Hall section written by Chuck McGregor:

http://www.prosoundweb.com/studyhall/lastudyhall/dB_calculat ions.shtml

This is a nice walk through of db calculations for many areas of sound and electronics.

Best regards,

John Halliburton

[Nathan Lehouillier]

Thanks.

[Tim Padrick]

You need to take power compression into account.  This will cost you quite a bit.  For instance the JBL 2241 driver that is rated 600w continuous pink noise:

At 60w the power conpression is 0.8dB

At 300w the power compression is 2.6dB

At 600w the power compression is 4.3dB


So basically speaking, once you get to perhaps 25% power, the loudspeaker stops getting louder as you put more power into it.  (And the above was spec'd from 50Hz to 500Hz - I expect it gets worse if you run below 50 and/or all your power is below 100Hz.)

[Nathan Lehouillier]

I am using Evx 180b's and I was thinking about Pd 1850's
because they list the lowest power compression I have ever
seen. I don't know to much about how it works but I bet the
5" voice coil helps. does any body know how the Pd 1850
compares to the Evx 180b's? I am using these drivers in Keele
W's. Thanks Nathan KDS&L

[Ivan Beaver]

First of all you need a spec to start with.  Simply taking the JBL spec is wrong-maybe.  You are running totally different drivers than JBL.  The cabinets were specifically designed for the JBL's.  The EV's-while a better driver in a vented box-may not perform anything like the JBL's in the horn.
 
Also at what freq was this sensitivity taken?  It may not be at your freq of interest.  Many times the sensitivity of bass cabinets is taken at a freq no where near where it will be used but will give higher readings.  Take a look @ EAW SB1000 if you want to see stupid stuff like a sensitivity at 1800 Hz!!!  Yeah that's where I want to run my 2x18's!  BUT it right off EAW's site.

Speaker ratings can be all over the map.  Not that the measurements are wrong-but what were the conditions under which the measurements were made?  You really have to look into the ratings and how they were taken to get the information you really need to make a good decision.

Take a look @ Tom Danley's new comapny www.danleysoundlabs.com if you want some real insight into how the measurements were taken.  More detailed info should be on the site shortly.

Ivan Beaver