How much power do you need?

I'm sorry, but I have to disagree with these 'target' figures for sound output.

Anyone who listens regularly to music at anything over 90dB is going to have _serious_ ear problems within a fairly short space of time. 100dB+ is complete insanity!

I spent years continually improving my car stereo - always striving for sound quality as opposed to the boy racer 'max power' approach. When I finished, I had well over 6 grands worth of kit and an amp that delivered 2x150w into the main speakers plus 300w into the subwoofer and could easily hit 118dB+ (somewhat helped by the cabin gain of the car).

I regularly listened at volumes far higher than sensible and now have significant hearing loss (-18dB at 6kHz), tinitus and great difficulty understanding people when there are several conversations going on - none of this is fixable :(

Dolby reference level is far too loud for me now.

Aside from this, different amplifiers clip at different points in their range and this is often power supply based. As long as the amp can drive the speakers with around 100w of _clean_ power then that is usually enough at most listening levels.

You need 10x as much power for you to perceive the sound as being twice as loud (10dB) so to get something twice as loud as your 100w amp, you need to go to 1kW!

The only other thing I'd say is that power amplifiers are truly the one piece of equipment where the numbers mean absolutely nothing. Take a random sample of 5 amplifiers (lets say a cheapo own make one from dixons, a rotel, an arcam, a chord and a krell reference) - now, give someone the specifications alone and ask them to decide which will sound best - bet they don't even get close!

The only thing that's worth doing for poweramp choice is deciding a budget and then going and listening to the amps that are in your budget!
 
Originally posted by pwiles
I believe it is only true if the cones that are being driven are identical, in most cases one of the them will be the tweeter which will output comparatively very little SPL compared to the Mid/Bass drivers, therefore in reality Bi-Amping gives no SPL gain,
This confused me when I took Before and after measurements of my system when I Bi-Amped, I had expected a +3dB lift which I did not get even at 1m. It did give benefits in control, soundstage etc.:clap:
Did you biamp with amps of the same gain? Did you then check the calibration or try to measure the maximum output?

I doubt you'd see the calibration levels change at all, but the maximum output should have gone up.

Oh and tweeters normally have a much higher acoustic efficiency, due to the small wavelengths, which is why tweeters can get away with being much smaller than mids or bass units. That's also why in active speakers it's common to find the amp driving the HF unit(s) is usually lower powered than the one driving the bass.

And, if you think about it in terms of harmonic distortion, the lower the fundamental frequency, the more the harmonics of this intrude on the mid-range.
 
kryten...I get your point about "target" SPL's....certainly if you listened to an average SPL of 100dB or even close to that,you would be at serious risk of hearing damage.
I think that what most people are aiming for is a system capable of reproducing transients in music with a wide dynamic range without clipping or other forms of distortion...certainly what I want from my system,but like you,I would never want to have it running constantly at that level.

The other pint about specs on amplifiers counting for little is quite right.....SET's in particular measure very poorly in general,and yet a properly designed one can offer superb sound quality...likewise my example of the Crown DC300A....superb measurements and power delivery,but awful,flat sound.
 
Originally posted by EvilMudge
Did you biamp with amps of the same gain? Did you then check the calibration or try to measure the maximum output?

I doubt you'd see the calibration levels change at all, but the maximum output should have gone up.

Yes they have the same gain, I used an SPL meter on a tripod about 4 feet from the RH 603 this was not moved through the experiment, the Bi-Amped system did not give me any more SPL than the system with just the MA6100's the 6100's gave me about 1dB more than the SR5300 but I put this down to a greater ability to drive the speakers at low frequencies.

I am not saying it was not am improvement, it is the best money I have ever spent, just no increase in SPL.
 
I'm sorry but this is all fine in theory, but please everyone go home tonight and listen to how really awefull your HiFi/Home Cinema sounds at reference level (hope it's not just mine anyway).

Get anywhere near reference level and even after doing obvious stuff like blu-tak on pictures etc. I get light bulbs buzzing, hinges ratling, floor boards up stairs wobbling, glass in picture frames ratling, not too mention neighbours banging on the door and windows.

I'm sure if I had 600 watts instead of the totally inadequate 85 watts I really have my room would still sound bad.

Sure It's nice to know what your system's capable of, but limiting yourself to only auditioning amps the produce at least X watts of power doesn't sound like a clever idea to me.

Slingshot
 
Originally posted by kryten
I'm sorry, but I have to disagree with these 'target' figures for sound output.

Anyone who listens regularly to music at anything over 90dB is going to have _serious_ ear problems within a fairly short space of time. 100dB+ is complete insanity!

Dependant on the Country (UK and US are Different) the guideline for SPL in a workplace is between 85 and 90dBA for a period of 8 hours, 90dBC with pink noise relates to about 83dBA (I just measured it) this is well under the guidelines and not insane, it is however fairly loud. 6k worth of audio in a car and 114dB (I assume that is dBC) well IMO that is insane, what I could buy with 6K Ummm.
 
Silly question. What is the reference level?:blush:
 
Originally posted by pwiles
This confused me when I took Before and after measurements of my system when I Bi-Amped, I had expected a +3dB lift which I did not get even at 1m. It did give benefits in control, soundstage etc

But when bi-amping you are not actually doubling the amplifier power to the speaker at all, which is why there is no increase in output.

Previously, you had X watts going to the speaker which was split by the crossover between the tweeter and woofer - however, a passive crossover gives the signal above the x-over point to the tweeter and the signal below it to the woofer: they both get (almost) 100% of the power in their respective frequency range so the tweeter has X watts and the woofer has X watts (you need to allow for the power requirements of the crossover itself, which will be pretty small).

Now you are simply powering the tweeter with X watts and the woofer with X watts but from a different amp (and still using the same crossover I assume, so the losses from that are the same) - you see, each speaker still only has X watts to play with!

If you had bridged the two amps together and given the speakers 2 * X watts you would have got a 3dB gain.
 
Originally posted by slingshot
I'm sorry but this is all fine in theory, but please everyone go home tonight and listen to how really awefull your HiFi/Home Cinema sounds at reference level (hope it's not just mine anyway).

Get anywhere near reference level and even after doing obvious stuff like blu-tak on pictures etc. I get light bulbs buzzing, hinges ratling, floor boards up stairs wobbling, glass in picture frames ratling, not too mention neighbours banging on the door and windows.

I'm sure if I had 600 watts instead of the totally inadequate 85 watts I really have my room would still sound bad.

Sure It's nice to know what your system's capable of, but limiting yourself to only auditioning amps the produce at least X watts of power doesn't sound like a clever idea to me.

Slingshot

Thankfully not a problem here apart from my wife complaining that it's too loud(never a problem when it's something she wants to listen to though...strange that...)...it's not just the 600W though...it's the whole thing...speakers/amp/processor etc....and then the costs!
 
Originally posted by kryten
But when bi-amping you are not actually doubling the amplifier power to the speaker at all, which is why there is no increase in output.

Previously, you had X watts going to the speaker which was split by the crossover between the tweeter and woofer - however, a passive crossover gives the signal above the x-over point to the tweeter and the signal below it to the woofer: they both get (almost) 100% of the power in their respective frequency range so the tweeter has X watts and the woofer has X watts (you need to allow for the power requirements of the crossover itself, which will be pretty small).

Now you are simply powering the tweeter with X watts and the woofer with X watts but from a different amp (and still using the same crossover I assume, so the losses from that are the same) - you see, each speaker still only has X watts to play with!

If you had bridged the two amps together and given the speakers 2 * X watts you would have got a 3dB gain.
Hang on a minute.
Let's say that to produce SPL Z, you need X Watts for LF and Y Watts for HF.
Now with a single amp you need an amp capable of X+Y watts for a given SPL. With two amps, you need one of X and one of Y. The reason you don't get a 3dB gain is that X is nearly always much larger than Y. However you do get an increase of Y watts in headroom for the LF (ignoring the much larger increase for HF) by bi-amping the system. Power is a function of voltage x current, where current is a function of the impedance at that frequency. With a properly designed crossover the power actually driven at HF into the LF section is negligible.
If you bridged two amps together you should get a x2 increase in voltage across the terminals, but this does not always mean a corresponding x2 increase in maximum current.
 
Originally posted by mylo
Silly question. What is the reference level?:blush:

According to Dolby. Reference Level is peaks of 105db for each main channel, Front Left, Centre etc and 115db for the LFE channel. If all speakers are set to small and all bass routed to the sub then the LFE peak increases to 121db. Assuming you have balanced all channels correctly with a test disc or the amp/receiver/processors test tones.

Reference Level is way too loud for me and I tend to watch movies at around -20db sometimes -15db below Reference.
 
Originally posted by Jase
According to Dolby. Reference Level is peaks of 105db for each main channel, Front Left, Centre etc and 115db for the LFE channel. If all speakers are set to small and all bass routed to the sub then the LFE peak increases to 121db. Assuming you have balanced all channels correctly with a test disc or the amp/receiver/processors test tones.

Reference Level is way too loud for me and I tend to watch movies at around -20db sometimes -15db below Reference.
Not entirely sure I've met the speaker than can do 105dB at 20Hz yet. And not many subwoofers can either :eek: Let alone 115dB or 121dB...:devil:
 
I'm sure you lot would try it out though.:devil:
 
Originally posted by EvilMudge
Not entirely sure I've met the speaker than can do 105dB at 20Hz yet. And not many subwoofers can either :eek: Let alone 115dB or 121dB...:devil:

Don't think I have either!:D Certainly right about the subs, hardly any can hit that sort of output. Maybe some in Dual configuration perhaps?
 
Originally posted by EvilMudge
Not entirely sure I've met the speaker than can do 105dB at 20Hz yet. And not many subwoofers can either :eek: Let alone 115dB or 121dB...:devil:

LOL....I think you'd be looking for perhaps a Linn Komri or Wilson System7....the Keltik(now discontinued) will also go pretty much flat to 20Hz,but you need some very heavy amps to go with that.
 
Originally posted by kryten


Previously, you had X watts going to the speaker which was split by the crossover between the tweeter and woofer - however, a passive crossover gives the signal above the x-over point to the tweeter and the signal below it to the woofer: they both get (almost) 100% of the power in their respective frequency range so the tweeter has X watts and the woofer has X watts (you need to allow for the power requirements of the crossover itself, which will be pretty small).

Had not thought about it in that respect and it does make a sort of sense. I am sure I could find an argument as to why it is not true, maybe The Beekeeper can tell you and it probably has something to the increase in current capability and music not being flat across the frequency range etc, I still like my (tweeter will output comparatively very little SPL & draw very little power compared to the Mid/Bass drivers) idea.

Well had a hard day and I am going to listen to a music system instead of talking about it.

I was only Joking about the car I’m sure it sounded great.

Cheers :smashin:
 
Bi amping IM distortion will gain a 4 dB advantage (plus other advantages)

Levels are for Peaks, many of you are quoting the average value and are therefore missing the point. Using a sub will take a HUGE load off the system, USE YOUR SUBS, that is what they are there for :). Anyone over 95 to 100dB is mad. If anyone is operating near ref levels the thing will sound crap, use every amp to within it’s limitations.

I have NO connection with the AV industry at all, I run a technical team for a large company and spend most of my working life ‘educating’ professors at university (;)) and funding their research grants. I am an AV amateur. I do know how to build amplifiers however (another hobby).

The post was just written to ‘start’ a debate. If anyone has any other figures I would be please to hear them but I suspect many amplifier companies won’t disagree strongly with what I have quoted. I suspect they are largely in line with ref levels (105 dB?)

I am still amazed why active speakers are not more ‘endorsed’ by the community, it is the logical extension of what I am arguing here, they are simply better and cheaper but we all still insist on our separate amplifiers. :(

Sorry I haven’t got long to comment as I am being sent away for the 4th conference in 3 weeks tomorrow :(. I will try an answer as many Qs as poss on the weekend if I can
 
PS if we need so little power why do all the 'serious' subs have silly numbers associated with them. 1200w to a 10 inch is quite common (look at the big V, popular here). This sub working at 79 Hz, how much different is it to 81 Hz from you 100w receiver?
 
Originally posted by The Beekeeper
I am an AV amateur. I do know how to build amplifiers however (another hobby).
Shouldn't that read I do know how not to build amplifiers

Still haven't figured out my power supply problem (but that's another subject).:confused:
 
Then again...... ive heard a couple of awfully sweet valve amps at only 10 watts or so.....

oh and i dont know what the significance is, but alot of big sub amps seem to be class D as opposed to A/AB

Ad
 
Class D is PWM switching technology, 90% efficient, which is a damn sight better than pure Class A - and anyone whose seen a big class A Krell will tell you they have lot's of fins. Trying to shoehorn one into a sub would be a nightmare!

With a 10W SET and a pair of really efficient speakers (97dB is the best I've seen for a conventional box) you could get to 100dB, but probably not with a flat frequency response. Measured speaker efficiencies are usually done with white noise (which has a higher HF content than Pink) and are a bit misleading. Though most SETs are voltage rather than current limited, so if that's an 8Ohm rating, it will probably drive a 2Ohm load quite happily.
 
time to upgrade then ;)

Mark, you may be right, much of what I have learned has been through failure not sucess, luckily now I make perfect amps :):)
 
May i order three "perfect" amps in that case?

Steven
 

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