Is 25 W into 8 ohms good enough?

[Bromiley]

Hi

Just curious if the Denon PMA-50 which is reated at 25 W into 8 ohms is good enough for my B&W 685 S2 speakers. I'm using an old Denon AVR (1610) at the moment and am looking for an alternative.

I like the small form factor of the PMA-50, plus the USB-B Dac would be great for my MacBook Pro.

Any thoughts?

 

[Laurens_B]

It really depends on what kind of music you listen, and on what levels you like to listen, which in turn depends on your room and listening distance.

I found the next video on the Harbeth User Group yesterday, which presents quite shocking results on the required amplifier power in certain circumstances. I think most people will find this interesting/educational.

Check out the video in post #9:

http://www.harbeth.co.uk/usergroup/showthread.php?2613-How-much-amplifier-power-do-I-REALLY-need

 

[iQ Speakers]

Interesting thats why you need a large PSU with large a reservoir of power (capacitance) in your amp to deliver lots of current when required.

 

[drummerman]

Interesting thats why you need a large PSU with large a reservoir of power (capacitance) in your amp to deliver lots of current when required.

In normal use, most people use very little power, even when listening relatively loud. Maybe one or two watts with higher peaks. That is why dynamic headroom (or good wattage) is relatively important if you regularely listen very loud.

Huge PSU's (without overzealous current limitation/safety ... as happens quite frequently) have their place, mostly when having to match electrically very difficult to drive speakers which are relatively rare these days.

After a certain point it becomes academic unless you want to weld with your amplifier.

Match your amplifier sympathetically with a modern and modestly efficient speaker and a good, well regulated/designed amplifier will suffice. What an oversized power supply will give you is more options as to what transducers you may use.

Using the Abrahamsen and other similar products as examples, the designs, big supplies but relatively small wattages, for the size at least, really hark back to a couple/three decades ago when Magnepans and other speakers were more prevelant.

I am of course generalising and my comments are not related to sound quality or value (which seems high in my example) but these days it is possible to engineer more efficiently.

As to the OP's question, I have not looked up the specs of his B&W's but many modern speakers use 4ohm bass units in which case the amplifiers output into lets say an average 4 to 6 ohm is more what he can expect in terms of power.

Being a small standmount I would not expect the speaker to be more efficient than perhaps 83 to 85db/w so a 30 or so watt amplifier will play reasonably loud without distorting but not at concert levels.

I would personally probably aim for a little more power but think his choice amplifier will suffice in theory for a small/ish room/flat. Can't comment on quality as I don't know the product/s

Talking of quality, I use regulated power supplies with my amplifier and cd players and I can't overstate how important a well designed supply is. Apart from high current/high capacity the old adage of 'its not only size that matter but ... ' holds true too.

A good electronic designer will pay attention to all these parameters and you, the punter have to choose according to your environment (and wallet). - Good design and craftmanship/parts usually costs a little more. You pays your money.

All in my humble onion of course.

 

[Laurens_B]

Interesting thats why you need a large PSU with large a reservoir of power (capacitance) in your amp to deliver lots of current when required.

In normal use, most people use very little power, even when listening relatively loud. Maybe one or two watts with higher peaks. That is why dynamic headroom (or good wattage) is relatively important if you regularely listen very loud.

Huge PSU's (without overzealous current limitation/safety ... as happens quite frequently) have their place, mostly when having to match electrically very difficult to drive speakers which are relatively rare these days.

After a certain point it becomes academic unless you want to weld with your amplifier.

Match your amplifier sympathetically with a modern and modestly efficient speaker and a good, well regulated/designed amplifier will suffice. What an oversized power supply will give you is more options as to what transducers you may use.

Using the Abrahamsen and other similar products as examples, the designs, big supplies but relatively small wattages, for the size at least, really hark back to a couple/three decades ago when Magnepans and other speakers were more prevelant.

I am of course generalising and my comments are not related to sound quality or value (which seems high in my example) but these days it is possible to engineer more efficiently.

As to the OP's question, I have not looked up the specs of his B&W's but many modern speakers use 4ohm bass units in which case the amplifiers output into lets say an average 4 to 6 ohm is more what he can expect in terms of power.

Being a small standmount I would not expect the speaker to be more efficient than perhaps 83 to 85db/w so a 30 or so watt amplifier will play reasonably loud without distorting but not at concert levels.

I would personally probably aim for a little more power but think his choice amplifier will suffice in theory for a small/ish room/flat. Can't comment on quality as I don't know the product/s

Talking of quality, I use regulated power supplies with my amplifier and cd players and I can't overstate how important a well designed supply is. Apart from high current/high capacity the old adage of 'its not only size that matter but ... ' holds true too.

A good electronic designer will pay attention to all these parameters and you, the punter have to choose according to your environment (and wallet). - Good design and craftmanship/parts usually costs a little more. You pays your money.

All in my humble onion of course.

Have you checked out the movie in the link I posted? He plays electronic music (quite loud though), and uses 500-750 watts with the peaks. Classical music at the same volume about 25 watts. Per channel that is.

 

[drummerman]

Interesting thats why you need a large PSU with large a reservoir of power (capacitance) in your amp to deliver lots of current when required.

In normal use, most people use very little power, even when listening relatively loud. Maybe one or two watts with higher peaks. That is why dynamic headroom (or good wattage) is relatively important if you regularely listen very loud.

Huge PSU's (without overzealous current limitation/safety ... as happens quite frequently) have their place, mostly when having to match electrically very difficult to drive speakers which are relatively rare these days.

After a certain point it becomes academic unless you want to weld with your amplifier.

Match your amplifier sympathetically with a modern and modestly efficient speaker and a good, well regulated/designed amplifier will suffice. What an oversized power supply will give you is more options as to what transducers you may use.

Using the Abrahamsen and other similar products as examples, the designs, big supplies but relatively small wattages, for the size at least, really hark back to a couple/three decades ago when Magnepans and other speakers were more prevelant.

I am of course generalising and my comments are not related to sound quality or value (which seems high in my example) but these days it is possible to engineer more efficiently.

As to the OP's question, I have not looked up the specs of his B&W's but many modern speakers use 4ohm bass units in which case the amplifiers output into lets say an average 4 to 6 ohm is more what he can expect in terms of power.

Being a small standmount I would not expect the speaker to be more efficient than perhaps 83 to 85db/w so a 30 or so watt amplifier will play reasonably loud without distorting but not at concert levels.

I would personally probably aim for a little more power but think his choice amplifier will suffice in theory for a small/ish room/flat. Can't comment on quality as I don't know the product/s

Talking of quality, I use regulated power supplies with my amplifier and cd players and I can't overstate how important a well designed supply is. Apart from high current/high capacity the old adage of 'its not only size that matter but ... ' holds true too.

A good electronic designer will pay attention to all these parameters and you, the punter have to choose according to your environment (and wallet). - Good design and craftmanship/parts usually costs a little more. You pays your money.

All in my humble onion of course.

Have you checked out the movie in the link I posted? He plays electronic music (quite loud though), and uses 500-750 watts with the peaks. Classical music at the same volume about 25 watts. Per channel that is.

I watched it

 

[Thompsonuxb]

That Alan Shaw don't half go on a bit without making any points.

That amp will drive those speakers fine at moderate volumes - just don't expect too much from complex pieces at volume.

Those speakers will benefit from better amplification though.

 

[Laurens_B]

That Alan Shaw don't half go on a bit without making any points.

That amp will drive those speakers fine at moderate volumes - just don't expect too much from complex pieces at volume.

Those speakers will benefit from better amplification though.

True, but regardless, I found the video quite interesting, didn't expect those results.

 

[iQ Speakers]

That Alan Shaw don't half go on a bit without making any points.

That amp will drive those speakers fine at moderate volumes - just don't expect too much from complex pieces at volume.

Those speakers will benefit from better amplification though.

I suspect this is an area far more expensive systems are better. Complex loud pieces and the ability to organise these. Unfortunately systems in show hotel rooms at low relatively low volumes don't really give you an incling of what might be.

 

[drummerman]

That Alan Shaw don't half go on a bit without making any points.

That amp will drive those speakers fine at moderate volumes - just don't expect too much from complex pieces at volume.

Those speakers will benefit from better amplification though.

True, but regardless, I found the video quite interesting, didn't expect those results.

Sorry, I didn't mean to be dismissive.

It is indeed interesting.

However, it bears little relevance to the 'average' listener to which I referred in my previous post.

If you are blessed with an income to be able to afford the Harbeths and the space to house them plus listen to material at high volumes, I would not for a moment disagree with him. You are then probably also in the lucky position to afford quality high power amplifiers.

For me and many like me, I really don't need multi hundred watt amplification. Actually I couldn't reasonable do that to my neighbours (although would like to try, just for a smidgen) and I doubt my speakers would take 700 odd watt, even for short periods.

It also raised another interesting subject, the one of listening to distortion in lower powered amplifiers.

Now, I did own a low powered 20 or so watt/channel valve amplifier. Even with very inefficient, sealed Ruark Standmounters, the volume I could achieve without being aware of any distortion was beyond comfortable. I often listened to big band stuff, such as sinatra and it never made me really feel wanting and we lived in a two flat conversion with neighbours frequently out.

It could, when turned up to maximum soften and eventually break up but that was not an issue ever and it probably didn't have the bass solidity of even my modest current cyrus set-up (or Sony STR-DB930 system) but it was wonderful to listen to all the same (from memory)

So, my point was, the quality of amplification is as important as the quantity, more so actually imho.

You can never have to much power (that includes obviously the supply) but it really is not always necessary to get to hung up on it. Allan Shaw was totally right in saying you have to adapt your system to your listening habits.

No arguments here.