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Can you mix speakers of different impedance? |
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Steevo 
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Joined: 21 December 2009 Location: Glos. Status: Offline Points: 58 |
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 Topic: Can you mix speakers of different impedance?Posted: 21 December 2009 at 11:39pm |
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In the short time I've been into sound kit I've always been of the opinion you can't mix sets of speakers with different impedance. Not sure why, but it's always seemed that way to me.
Anyhow, was talking to a guy about this the other evening and he showed me a setup he ran using some Peavey HiSyS speakers with 4 Ohm tops and 8 Ohm bass cabs, both plugged into each other on the same amp. He said that the guy who sold it to him in the shop said they were designed to work that way and he's used them like that ever since.
Can someone enlighten me about all this impedance malarky please?
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backlash
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Joined: 11 November 2008 Location: Devon Status: Offline Points: 3532 |
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Posted: 21 December 2009 at 11:54pm |
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If this is on one channel, surely the amplifier has a load of 2.6ohms present?
Basically, running one 8ohm driver or speaker on one channel of an amp is an 8 ohm load, 2 8ohm drivers wired in parallel again on one channel of an amp is a 4 ohm load, 3 8ohm drivers in parallel is 2.6ohm load etc etc Edit - so with regards your post, a 4ohm load and an 8ohm load = 2.6 ohm load. Hope his amplifier is rated to take a 2.6ohm load Edited by backlash - 21 December 2009 at 11:56pm |
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djshaney
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Joined: 12 May 2009 Location: middlesex Status: Offline Points: 830 |
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Posted: 21 December 2009 at 11:57pm |
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yep, but the 4 ohm drivers will be twice as loud as the 8ohm's...
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cravings
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Joined: 30 January 2007 Location: Ireland Status: Offline Points: 7441 |
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Posted: 22 December 2009 at 12:15am |
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do his bass cabs definitely not have a passive xover / filter in them, with an output to the tops?
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backlash
Old Croc
Joined: 11 November 2008 Location: Devon Status: Offline Points: 3532 |
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Posted: 22 December 2009 at 12:33am |
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thats what I have been thinking....
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rich_gale
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Posted: 22 December 2009 at 1:07am |
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i guess if it is a 2 way passive the amp will see 4ohm mid/high and 8ohm in the freq band the sub runs at. and i recon the built in crossover in the sub is configured to be at the right freq when using a 8ohm mid top. if this is the case you will either loose a band of frequencies around the crossover point, or have a band where both cabs are doing the same freq's.
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REFLEX ALL THE WAY.... (however, im playing with horns again...) That ok Mister Valiant? :)
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FUBARD303
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Contentiously righteous Joined: 29 September 2008 Location: Allup Inyo MOUF Status: Offline Points: 120 |
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Posted: 22 December 2009 at 1:22am |
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My short answer is I AGREE... My JRX 125's Have two parallel 15" woofers and a single 1' comp driver all at 8ohm, making 4 ohms of woofer and 8ohm of hi-freq. This is the exact inverse of what you're describing and seems more appropriate but I'm pretty sure the point that "speakers don't always have to be exactly the same" still stands. Maybe they're counting on there being less 'tops' in a bass guitar's signal and wanna counteract that by making em louder to achieve a particular sound? I also agree that this IS in fact odd and openly admit that instrument amping is def NOT my area of expert. There indeed might be a crossover involved... might you ask? |
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DjMidKnight
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Joined: 31 August 2009 Location: Abq NM Status: Offline Points: 298 |
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Posted: 22 December 2009 at 2:04am |
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rich gale is correct, if the sub has a passive cross over in it then its just a complex load, if the xover isnt designed for 4ohm speaker then its puting the xover point higher than it should for the tops, which isnt the biggest problem with the roll off from the sub and the top those frequencies are covered but just not as well as would normaly be covered in a L-R allignment.
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reality is meerly a compilation of what our limited sences precieve as being fact therefore there is no true universal reality and as such i propose that space and time can be bent twisted and altered
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Steevo
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Joined: 21 December 2009 Location: Glos. Status: Offline Points: 58 |
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Posted: 22 December 2009 at 10:22am |
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Errrr...think I understand this!
But yes, all of you are right there is a crossover in the bass speakers.
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backlash
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Joined: 11 November 2008 Location: Devon Status: Offline Points: 3532 |
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Posted: 22 December 2009 at 11:14pm |
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The jbl jrx125 are most definately a 4 ohm load we have tested it and we are not sure either how, maybe something to do with internal wiring on the crossover. But I see where your coming from. If i was you fubard, ditch the 1" comps on those cabinets, as they are awful and replace them - it will be the best thing you ever did it was for us and they sound great now!
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FUBARD303
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Posted: 22 December 2009 at 11:26pm |
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Yeh! I just hooked up the selenium refit and WOW! next step is to bypass te cover n biamp... I'm thinking Alesis's reference series might sound pretty clear! Mmmm... Crispy highs.... I <3 hi-fi @ PA levels!!!
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"Always look on the bright side of life" -Brian
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backlash
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Joined: 11 November 2008 Location: Devon Status: Offline Points: 3532 |
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Posted: 22 December 2009 at 11:29pm |
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we used a P audio driver worked well. be careful on the bi-amping, either keep the top 15 and 1" running on the crossover still and put 250 to 300w rms into it, and run the bottom 15 90hz to say 160 hz on another amp 200w rms or you might loose some of the trademark kick on those cabinets!
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