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18" 4 ohm

jondog

jondog

Mar 14, 2002
2,715
20
NYC metro area
#1
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#2
You'll want to watch the impedance. Someone on this forum reminded me that it comes to 2.67 ohms. (8 x 4 / 8 + 4 = 2.67) You don't want to go lower than your amp's ohm rating. So if you're amp is rated at 2 ohms you're ok, if it's rated at 4 or 8 ohms, you could damage it.
CV speakers are ok, but they're usually for stereo use. There are others that are better.
 
#3
Going to a 4 ohm driver doesn't necessarily mean you'll get any more headroom at all, and you may end up worse off as a less sensitive driver will cost you output. The only way you can make an informed choice is to model your current rig in a box program such as WinISD and then do the same with the driver/cabinet combination you're considering, and that's not possible without knowing the TS specs of the driver. All the seller seems sure of in this case is the driver size.
 
#4
I'm running my sub off one side of my power amp. 8 ohm load = 230W, which is not a lot for lows. 4 ohm load = 400W, which is almost double so it should be noticable. Yes I have no data on this CV, that's why I'm asking here :) It's within my budget and he used it for the same app. I'm going to . . . I'm wondering if it's worth the $ to take a chance.
 
#8
Jondog, that speaker looks suspiciously like the one inside the Cerwin Vega Jnr Earthquake, which was a folded horn enclosure. Actually those Jrn earthquakes weren't too bad as a PA sub, but to get any real thump from them, we had to use 2 of them on each side.

Here's the thing. You're thinking that doubling the wattage will give more headroom and SPL. This is true if the "new" speaker is equally efficient as the old one. But a mere 3dB drop in sensitivity between drivers could mean the new speaker is actually quieter then the old one.

This can be shown mathematically. The formula for SPL is:-

SPL = (Log "Watts" x 10) + Sensitivity.

We don't have exact figures to work with but lets pretend the 8 Ohm EV has a sensitivity of 99dB. At 230W this translates to:-

SPL = (Log230 x 10) +99.
SPL = 122.62dB

Now lets replace the EV with a speaker that's 3dB less sensitive, but is 4 ohms. So 96dB sensitivity and 400W:-

SPL = (Log400 x 10) + 96
SPL = 122.02dB

You've gained nothing. You've actually lost 0.6 of a dB.
 
#11
OK, it looks like they used that driver in several different PA cabs. Here's what I found on Pro Sound Web . . .

"Hi
its look like the old PD-18C
specifications are
useable frequency response 30hz to 16khz
eia power hanling 300w
spl 1m 1w 100db
max spl 125db
dispersion 100h 70v
components
lf 188eb 18"
mf er124 12"
hi h-25 (fostex tw?)
crossover 300hz and 3khz"

So, if all I have is the 188EB, will I still get 100 db sensitivity? Also, I found that it costs more than $100 to recone one of these.
 

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