Compression Driver wattage.??

Mark Batchelor

New member
Aug 2, 2020
5
1
3
55
Australia
Hi there ,
my first post . I have a question that bugs me . I fix , make two way monitor and FOH cabinets,and my dumb question is. If the woofer is ,say 300 watts rms @ 8 ohms. What should the compression driver wattage and ohms be.?Given there is a Xover involved.
any help greatly aprieciated Thanx.
 

Caleb Dueck

Junior
Jan 11, 2011
519
7
18
Montana
Need a lot more information. What is the model of each driver? Who designed the crossover? A crossover is designed for the specific drivers and specific box; a generic crossover is nothing but a wild guess if it will perform as desired. Who designed the speaker? I see you mentioned 'fix' - if so, that implies the speaker system isn't stock.

If everything is properly designed (unknown) - and if the program rating of the driver is [email protected] - then you would send [email protected] to the speaker. The crossover would filter out and pad down the power going to the HF driver so that it and the low driver would hit their limits together.

If it's a cheap speaker that was attempted to be used to reproduce more SPL than it was capable of - just swapping the drivers with 'better' drivers is a waste of money. At best - replace with stock drivers and sell the speakers and put the money toward something that will provide the performance you need.
 

Mark Batchelor

New member
Aug 2, 2020
5
1
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55
Australia
Yeah thanks,
its old school wedge just wanted a ball park idea no way of knowing the woofer wattage but I imagine they would be around 300 watt Etone vintage drivers. So I got 30 watt compression drivers off eBay to replace the pezio Motorola bullets I found in them. I just wanted to know the rough differences eg do I need 300 watt drivers to match.as for the xover who knows the specs on that . Someone wrote in marker 1600hz. Anyway they sound great now but with the horn blow??
 
Oct 25, 2018
88
10
8
59
Bideford, Devon. UK
Given the relative efficiencies which I would estimate to be around 105db/W and 95db/W for the compression driver and 15" respectively, the power rating would be about -10dB compared with the power required by the 15", ie 30W, so you are probably not too far off with the driver and crossover point you have. There are endless 'fixes' which could be applied, requiring time, measurements, and expense, however if you are happy with the sound (not too 'toppy' due to the efficiency of the HF driver - this might need a tweak), and the data you have supplied is correct, I would say Party on Dude.
 

Mark Batchelor

New member
Aug 2, 2020
5
1
3
55
Australia
Given the relative efficiencies which I would estimate to be around 105db/W and 95db/W for the compression driver and 15" respectively, the power rating would be about -10dB compared with the power required by the 15", ie 30W, so you are probably not too far off with the driver and crossover point you have. There are endless 'fixes' which could be applied, requiring time, measurements, and expense, however if you are happy with the sound (not too 'toppy' due to the efficiency of the HF driver - this might need a tweak), and the data you have supplied is correct, I would say Party on Dude.

Yes........ Thankyou Carl thats the spirit! may be a capacitor or something here or there But Ive got a better idea now thanks again . So as rule of thumb I could say use a compression driver of 10% of the woofer wattage and turn it up.!!
 

David Morison

Freshman
Aug 21, 2012
153
8
18
Aberdeen, Scotland
One thing to be careful of - if the original HF drivers were piezo's as you say, the crossover for them may well be much more basic than needed for a proper compression driver.
This is because piezo's have a rising impedance as frequency decreases, so they naturally draw less power down low, making them more tolerant of very basic crossover circuits.
Real compression drivers do not behave in the same way so often need more comprehensive crossovers.
If you can, draw out the circuit from your crossovers and post it here, or at least post pics of it (both front & back so we can see what's connected where) before putting any power through your new compression drivers.
 
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Riley Casey

Sophomore
Jan 12, 2011
252
18
18
WDC in the USA
www.espsound.com
Without a background in speaker design you would probably do well to simply read up on the recommendations of the makers of your woofers and compression drivers and use what ever crossovers they make or recommend. Randomly assembling what ever parts are a good deal on eBay is not the best way to achieve a good sounding speaker.
 
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Mark Batchelor

New member
Aug 2, 2020
5
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55
Australia
Thanks everyone
The wedges are 30 years old I got them off Facebook $100 pair . After gutting them re painting and re wiring I was left with two bangers for the Band room . Tweeters were a bit week so I pinched couple of driers out of another set .Bingo all working x-overs all good so I got replica drivers off eBay . All good. My question was is there a rough relationship with wattage.im sure as I’m not trying to win audio awards that these $30 titanium drivers will do. Again thanks it was fun.
 
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Perry Wright

New member
Jan 17, 2019
3
1
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70
Waverly Iowa
Simple answer: About 10 : 1. So with a 300 watt woofer, a 30 watt hf driver (tweeter)
Without a doubt the best value, and certainly one of the best drivers anywhere is PRV D280Ti
PRV from Brazil grew out of Selenium after it was bought by JBL in ’06, and some there did not like being owned by an American company. The Selenium drivers (nearly identical) were equally impressive, which is why they got the attention of JBL.
The D280Ti will outperform Peavey, Yamaha, ElectroVoice, and even cheaper JBL in all cases.
• The xover gets more credit than it deserves. It will make a slight difference, but it can’t make a bad driver sound good, and a good driver will sound good no matter other factors.
I'm glad you found a cheap solution, I just posted this for other readers who may stumble on this forum.
36E6EF6E-7301-4A89-A834-439FD7AB8B0B.jpeg
if you are designing a horn or have a choice, use bolt on style. The threaded throat adds a tubular section which makes the highs much more directional. It is best to expand as soon as possible for maximum high dispersion.