View Full Version : dual head and attenuator conondrum
09-02-2007, 08:12 PM
Ok , I am using a twin head setup, ftr 37, rsa 23. and have been running each into its own cab with an 8 ohm hotplate on each one for rehearsal.. I want to try running both heads in to the ftr cab with the blue / gh30 one head into each speaker.make it easier to transport and possibly lower the volume some I f I want to use the attenuators I know I have heard that you can be off one size ohms wise..
So would I do best to run out of the 16 ohm jacks on the amps into the 8 ohm hotplates into the 16 ohm speaker?
Or out of the 8 ohm jacks into the 8 ohnm hotplate ,into the 160hm speaker.. My thought is eaither way its 8 ohms into the 16 ohm speaker so I should just use the 8 ohm output jacks on the heads.
But I dont really know what the hell I'm talking about lol
Sorry to beat the:horse but I guess he's not dead yet.Thanks in advance
09-02-2007, 10:33 PM
I think 8 into 8 into 16. At least the match is then correct between amp and the next 'link' - and it's the amp that'll have damage done to it if anything. However I'm not an expert and have heard various issues with any sort of mismatch. My guess is you're OK, but it's only a guess.
09-03-2007, 05:53 AM
What Jim said is right.
The amp must match (or be a safe mismatch with) the attenuator, not the speaker, if you can't do both at the same time. At any attenuation of more than -3dB, the attenuator is the bulk of what the amp 'sees', and the further down you go the less important the speaker impedance is.
An 8-ohm Hotplate is not a safe mismatch for 16-ohm amp output (in theory, it's still 2:1, but the Hotplate's impedance characteristic is not the same as that of a real speaker), but a 16-ohm speaker is a safe mismatch for an 8-ohm amp output.
Out of interest john, do you think the mismatch between attenuator and speaker will effect the sound much? Sort of strikes me that as maximum power transfer isn't object then possibly it won't be as big of a deal sonically as when running without an attenuator. Or am I way off?
09-03-2007, 09:42 AM
yes inquiring minds want to know, thanks for the responses. I'[l let you know how it sonds . I have to wait for my tonebone but it should get here tomorrow
09-03-2007, 10:21 AM
Running mismatched always affects the bandwidth (ie less low bass and high treble) to some extent, and depending on which way, both the amount of that at each end or the range, and the dynamics as well. A low mismatch (amp into lower impedance load) generally gives a thicker, flubbier, more 'squashy' sound with less bass definition (although still a lot of bass) and slightly less top end; a high mismatch gives a flatter, more even but less dynamic sound with less deep bass and more midrange and upper mids, a sort of 'drier' sound.
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