Amp power higher than speaker rating

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vonchief

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Dec 21, 2008
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Hi all,

I am currently running two Rotel 1070 power amps,one for the left and one for the right channel.

As they are rated at 130w per channel i guess that means i now have 260w per channel.

I never listen at loud volumes but as i had a spare amp lying about i thought it would be worth trying this bi-amped way of setting things up. It all sounds fine with my ATC SCM7 speakers ,but i would like to try some spendor S3e with my amps to compare.

The problem is they are only rated at 125w, so would this damage the speakers ?

Should i just try them with the one amp or would the bi-amp method still offer the better sound quality as it does with the ATC speakers.

Cheers.
 
vonchief:
Hi all,

I am currently running two Rotel 1070 power amps,one for the left and one for the right channel.

As they are rated at 130w per channel i guess that means i now have 260w per channel.

I never listen at loud volumes but as i had a spare amp lying about i thought it would be worth trying this bi-amped way of setting things up. It all sounds fine with my ATC SCM7 speakers ,but i would like to try some spendor S3e with my amps to compare.

The problem is they are only rated at 125w, so would this damage the speakers ?

Should i just try them with the one amp or would the bi-amp method still offer the better sound quality as it does with the ATC speakers.

Cheers.

No problem whatsoever.
 
power rating quadruples in this case although it all wont be useable.
 
Hi vonchief

If you are running one RB-1070 per SCM7 then you've got them bridged in which case they are around triple the power (360w). You can still safely use them in this mode with the Spendor speakers even though they can accept up to 125w each. You just need to keep the volume in check. This also applies with the SCM7 speakers.

Alternatively you could unbridge the power amps and bi amp the speakers (which i feel gives better performance most of the time then bridging amps).

Btw, in case you are not aware please ensure which ever speakers you use are of 8ohms when the amps are bridged as the amps will see a 4ohm load.

All the best

Rick @ Musicraft
 
Thanks for the replies.

I don't have the amps bridged,I am running both left outputs of my pre amp to one amp and both right outputs to the other.

I am then running a speaker off each amp to bi-wire.
 
vonchief:
Thanks for the replies.

I don't have the amps bridged,I am running both left outputs of my pre amp to one amp and both right outputs to the other.

I am then running a speaker off each amp to bi-wire.

You will damage your eardrums before your equipment.
 
vonchief:I don't have the amps bridged,I am running both left outputs of my pre amp to one amp and both right outputs to the other.
I am then running a speaker off each amp to bi-wire.

In which case you only have 130W per channel.
 
Sounds wrong to me

The rotels are stereo amps? If so you should have one driving HF on both speakers and the other driving LF on both speakers
 
You can biamp both ways with stereo power amps, but agreed it's usually thought best to use one amp for the LF drivers in both speakers and the other for the HF, so that the requirements of keeping a grip on mid/bass drivers don't impinge on the amp powering the tweeters.
 
I must admit i haven't tried wiring up that way so it would be interesting to hear any differences.

The reason i wired up the way i have was because i read about it

EDITED BY MODS - House Rules

I also was under the impression that as each amp has 130w per channel then it would be double this way., not that i need this much power.
 
Nope

Its 130 watts per channel

Doing one amp for LF and another for HF keeps the signals apart which should help with biamping

HOWEVER. You may find that theres a 'gap' where the frequencies split (Loudspeaker dependant) so may prefer it how you have it now anyways
 
No: each crossover section is still only 'seeing' a 130W amp, as it would were you to single-wire using just one of the amps.
 
So it seems i am worrying about nothing with regards to having too much power for the speakers.

I'll just take your word for it about the power not rising by using two amps as you should know about these things.

Still cant see it myself but i won't argue as i am no expert.

Thanks anyway for putting my mind at rest, even though i am slightly puzzled.
 
vonchief:I don't fully understand but surely using two power amps instead of one increases the power ?

Think of one stereo amp as being 2 mono blocks. Each mono block is rated at 130 Watts into 8 ohms (Taking the speakers as being exactly 8 ohms)

If you split them then there's still 130 watts per channel as each amp still only 'sees' one speaker at 8 ohms

So putting that into 2 stereo amps, both amps still only 'see' one speaker which means 130 watts max (the bass and the tweeter will still equal 8 ohms whether one or 2 amps is driving them). One amp driving means one amp is taking the full 8 ohms. 2 amps means they're sharing the 8 ohm load. Both still = 130 watts

If however you could 'bridge' the 2 internal amps (I very much doubt you can, but ive not looked into it so unsure), then that would double the wattage (Theoretically). Bridging is physically joining the 2 internal amps together to create one big one.

(If anyone disagrees with the above, please post my error as I'm not 100% about this)

Bi amping though is a curious game. The more I've looked into it the more I believe that 'generally speaking' (There's nearly always exceptions to the rule) 'passive' bi amping can be a bad thing ('Passive' meaning the internal crossovers of the speakers are still used, which is how 99% of people bi amp)

True bi amping means opening up the speakers and removing the crossover and using an 'active' crossover in-between the pre and power amps (Very technical though, as the crossover must be made specifically for the speakers theyre driving)

With regards to passive bi amping (And biwiring), you can hear subjective benefits with 'some' speakers. But theres just about always 'phase shift distortion' where the bass stops and the tweeter starts (meaning mid level detail is distorted)

Your probably better wiring up single wires (Not biwired) from each amp (Use the same speaker wire as jumpers). So one amp drives left and one amp drives right

Experiment and see what you think
 
I did try the amps bridged but was advised on this forum to try bi-amping as a way to improve quality.

How would i use a single speaker cable run if i used an amp for each speaker ?

Are you saying that i should just run the left channel to one amp and the right to the other, then just connect the speakers to one side of each amp ?
 
vonchief:
I did try the amps bridged but was advised on this forum to try bi-amping as a way to improve quality.

How would i use a single speaker cable run if i used an amp for each speaker ?

Are you saying that i should just run the left channel to one amp and the right to the other, then just connect the speakers to one side of each amp ?

Yes thats correct

Im saying thats the safest way to keep the frequency response level. Bridging WILL give more power (And therefore more control than without bridging) so id definitely bridge if your going to run left to left and right to right

Many people swear by passive bi amping. But a lot of those that did have gradually gone back to standard single wire runs as they didnt like the midrange cutoff (Again, this is speaker specific)

I cant say for sure what YOU would like best obviously

What have been your personal experiences so far?
 
I have an old Rotel RC 970 pre with x2 RB 970mk2's powers amps as my second system and having tried bi-amping horizontally, vertically and also bridging, for me, bridging the power amps really brought the system to life. I can't say I noticed much difference bi-amping compared to using just one of the power amp's in stereo mode (bi-wired to Mission 735i). If you do decide on the bridged mode then with the extra power you'll have on tap you really shouldn't push the volume round too quickly. Another advantage of bridging the power amps, from a cost point of view, is that you use one less set of interconnects
emotion-2.gif


As for the wiring side of things, I'd look for the instructions for that particular amp. It should be easy enough to find it on the web if you don't have it at home but I found the instructions with my Rotels very useful re: bi-amping, bridging and bi-wiring etc etc.
 
To be quite honest i was happy with the sound using just the one amp.It was only when my other one became spare that i thought about bridging and bi-amping.

You need to take the top off each amp and move jumpers around to bridge and the time this takes makes comparisons quite hard.Saying that,when bridged everything seemed more dynamic but this is what i was expecting so may have all been in the mind.

Going to a bi-amped set up seemed to give greater detail but again this is something i was expecting to hear.

The other problem is one person will advise that bridging is the best way ,where others will say you only bridge if you need more power and that it increases distortion and quality will suffer.I really don't need masses of power as i only listen at lowish volumes late at night.There is also the original worry of damaging the speakers.

I was just going to sell the spare amp but before i do i thought it was worth trying a few combinations to see if using two would be of benefit.I suppose the only answer is to retry all combinations and make my own mind up as to which sounds the best.
 
vonchief:
You need to take the top off each amp and move jumpers around to bridge and the time this takes makes comparisons quite hard.Saying that,when bridged everything seemed more dynamic but this is what i was expecting so may have all been in the mind.
where others will say you only bridge if you need more power and that it increases distortion and quality will suffer.

According to figures ive just read, bridging the rotel changes its distortion from 0.03% to 0.1% (not good)

So my personal recommendation is left to left and right to right without bridging (Should certainly be better than one of them driving left and right as the 2 signals are kept apart)

As ive stated, you may prefer passive bi amping - just bear in mind your creating phase shifts when its done.
 
Really appreciate all the advise,thanks for that.

Is there any disadvantages to only using one channel of an amp ?

Can't think there would be but probably best to check.

I suppose there is no danger of damage to the amp by not having a speaker connected to one side.
 
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