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converting ohms

superbassman2000

superbassman2000

Dec 20, 2000
11,338
56
Minnesota
#1
hello,
so i wondering...is there something that can convert ohms? for example...i have an 8-ohm head and i am looking at a 4 ohm cab. the head doesn't say anything about being 4 ohms, and suggest that you only use 8 ohms. is there something that i can put in between to convert one to the other? or would it be safe to go ahead and use that setup?

any advice is welcome!

Charlie
 
#5
superbassman2000 said:
hello,
so i wondering...is there something that can convert ohms? for example...i have an 8-ohm head and i am looking at a 4 ohm cab. the head doesn't say anything about being 4 ohms, and suggest that you only use 8 ohms. is there something that i can put in between to convert one to the other? or would it be safe to go ahead and use that setup?

any advice is welcome!

Charlie
Click to expand...
I'd say it's not worth the trouble. There are a lot of decent 8 ohm cabs out there, so it would IMO make more sense to look at one of those. Or esle consider a different amp, depending of course on budget, availability, and what works for you.
 
#6
well, its a Gallien-Krueger 250BL, i had plans to use it with my 8 ohm ashdown mini10T, but then i had the idea to use it with my 1810, which is 4 ohms. i know many amps can do either 4 or 8 ohms, but GK is one company that i notice always say that 8 ohm is the only way to go, and say nothing about being capable to run at 4 ohms...


Charlie
 
#7
that's very odd. i would contact gk and ask them if the amp can do 4 ohms. Most heads can do 4 ohms, i can't even think of any that i know of that are only safe down to 8 ohms. The only amps i can think of that can only do 8 ohms would be some small combos that have an 8 ohm speaker and no extension speaker jacks.
 
#8
IvanMike said:
that's very odd. i would contact gk and ask them if the amp can do 4 ohms. Most heads can do 4 ohms, i can't even think of any that i know of that are only safe down to 8 ohms. The only amps i can think of that can only do 8 ohms would be some small combos that have an 8 ohm speaker and no extension speaker jacks.
Click to expand...
now thats what i was thinking...but if you read the manual, it tells you to match it with an 8 ohm cab...anywhere else you look on the net or wherever, you'll only get info on 8 ohms...bizzarre...maybe i will contact them....
 
#11
I believe the BackLine series only goes down to 8 ohms.

If your Peavey 1810 cabinet has a Black Widow 18, you could always buy an 8 ohm replacement basket on eBay for pretty low bux. It's just a matter of a few screws to move the magnet from one to the other.

An example of a closed eBay auction

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=47094&item=3764863170&rd=1&ssPageName=WDVW

I'm not sure how the 10s play into that...I know that they're crossed over, but don't know whether the 2x10 section is 4 ohms or 8 ohms. If they're combined impedance is 4 ohms, I doubt that it would have the same negative effect on the amp as a 4 ohm woofer would (since the power burden on an amp is less at higher frequencies).

Besides, the 4 ohm rating would be the nominal impedance which usually occurs at a lower frequency anyway and they may very well present an 8 ohm impedance (or higher) above the internal crossover point.
 
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#12
The .pdf manual is available right there on Musicians Fiend and it is pretty clear:

"Be sure not to exceed the recommended
speaker load listed below.
Maximum Recommended Speaker Load:
One 8 Ohm cabinet."

"2- Speaker Out:
115/250BL: 125W power amp output. It delivers 125
watts into 8 Ohms.
Lower impedances should not be used. Higher impedances
such as 16 Ohms or No Load are acceptable. No
damage will result from operating the amplifier with
the speakers disconnected."

They go on about 50 amp current capability, and also state the output section has no current limiting/safety cutoff. It sounds like they are offering an amp with limited continuous rms power capacity but loads of transient headroom. So, with no limiting circuitry, running it into low impedences would risk blowing the output up. I would maybe be running it into 2 nominal 4-ohm cabs in series, or any 4-speaker 8 ohm cab.
 

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