How many watts?

[Filterlab]

As I’m sitting here reading more and more about the Aleph 5 amplifier (60wpc) - an amp which I’m seriously considering, I wonder how many watts do I really use?

My power amp has ludicrous amounts of power; 250wpc into 8Ω and 500wpc into 4Ω. Given that my speakers are 95dB/W/m and that my active sub has an input impedance so high it barely presents a load, I’m sure I never even tickle the surface of the available oomph.

I rarely listen at high volumes, mostly I listen at low to moderate volumes.

So, my question is, how would one actually find out how many watts are being ‘used’ during listening? Is there a device one can connect to the speaker terminals to monitor such a thing?

[Mand]

Been thinking about this as well. Get a decibel app for your phone.
If the speakers are rated at 88db per 1watt at 1m sensitivty and the app shows 88 db, then does that mean you’re using 1 watt?

[Filterlab]

I guess it would. I never even thought about doing that way. I was thinking of a method to measure AC RMS voltage. :lol:

I suppose that once set up as a reference, one could see how much one watt was actually doing.

[Barry]

How far away from your speakers do you listen?

If you listen 2 metres away then you reduce the speaker sensitivity by 6dB, thus 89dB/W.

Orchestral peaks can be as high as 120dB, so you would need 120 - 89 = 31dBW. Call it 30dBW, or 1,000W. But since you have two speakers, a 500W/channel amplifier would suffice. But as you say, for the great majority of the time the average power called upon is less than 0.5W, so you only need the high power reserve for volume peaks of very short duration.

If you assume a typical speaker impedance of 8 Ohm, 0dBW (= 1W) corresponds to a r.m.s voltage of 2.83V. Thus an amplifier producing 20dBW (or 100W) will present a voltage of 28.3V across the speaker terminals.

[Macca]

For a pair of speakers you get an extra 3dB

For watts it is always better to have too many rather than too few.

[Filterlab]

I’ve got ya. The speakers are 3m from my listening position so if the first equation is linear then that would be 83dB/W.

I don’t really listen to orchestral music and the source is only digital. Most of the time it’s sound from Netflix and Prime (so not dynamic at all), my girlfriend listens to YouTube music during the day (mostly electronic, if not entirely), and my listening is mostly electronic but also acoustic and prog or similar. Redbook maximum dynamic range with dithering (which I have enabled on Fidelia) is 115dB (IIRC) so would be 115 - 86 (including the 3dB for the pair) = 29dB/W.

The Aleph 5 is rated at 60wpc into 8Ω and has a maximum output of 30v at 8a. I’d imagine this would be ample for my needs given the lack of dynamic peaks in the choice of audio and the relatively moderate volumes?

[Macca]

Yes should give you plenty of headroom assuming the speaker sensitivity rating is correct, usually you can deduct a couple of dB from what the manufacture claims. Even so you'd still be good.

Don't really understand why you want to swap to the Arcam though?

[Barry]

Sound pressure level (SPL) falls off as the inverse square of the distance. So compared with that at 1m (as quoted in your speaker sensitivity of 95dB/W), listening at double that distance of 2m will reduce the SPL by a factor of 4, or 6dB, to 89dB/W. Thus trebling the distance to 3m will reduce the SPL by a factor of 9, or 14dB, to 81dB/W.

Your amp can produce 60W/channel (or 17.8dBW), so the maximum SPL from each speaker will be 81 +17.8 = 98.8dB, and since there are two speakers an SPL of 101.8dB in total.

102dB (above the threshold of hearing) is classed as very loud (https://audiology-web.s3.amazonaws.com/migrated/NoiseChart_Poster-%208.5x11.pdf_5399b289427535.32730330.pdf) and if maintained at that level (assuming the amplifier doesn't overheat) would cause some hearing loss after about 10 minutes.

Or to put it another way - you have plenty of power for your needs, provided you don't listen to continuous sine waves at a high level for long periods of time.

[Light Dependant Resistor]

As I’m sitting here reading more and more about the Aleph 5 amplifier (60wpc) - an amp which I’m seriously considering, I wonder how many watts do I really use?

My power amp has ludicrous amounts of power; 250wpc into 8Ω and 500wpc into 4Ω. Given that my speakers are 95dB/W/m and that my active sub has an input impedance so high it barely presents a load, I’m sure I never even tickle the surface of the available oomph.

I rarely listen at high volumes, mostly I listen at low to moderate volumes.

So, my question is, how would one actually find out how many watts are being ‘used’ during listening? Is there a device one can connect to the speaker terminals to monitor such a thing?

Unlike the majority of amplifier manufacturers Pass, does not appear to state the input sensitivity - Volts or fractions of a Volt RMS that allows full output from the amplifier from a input signal, making it very difficult to reliably assess the 60 watt output figure, relative to a input signal.... one is just left to guess I suppose ?

[Filterlab]

Don't really understand why you want to swap to the Arcam though?

Aleph 5, not Alpha 5. The Aleph 5 is a Nelson Pass design. If I wanted an Arcam I'd get my A85 out of the office. :lol:



Or to put it another way - you have plenty of power for your needs, provided you don't listen to continuous sine waves at high level for long periods of time.

Thanks Barry, that was my feeling too.

[Macca]

Aleph 5, not Alpha 5. The Aleph 5 is a Nelson Pass design..

Doh, :doh: I need to learn to read more carefully.

You know NP likes to tailor his sound?

[Qwin]

There are many factors to consider, not just watts.
My 3 way system is bi amped.
I use a 12w valve amp into the 8ohm mids/twt, both 93dB sensitivity.
The bass driver is 4ohm and 89dB sensitive, I use a 4ohm/700w class D to power this.
I can take this to ear bleeding levels and the 12w keeps up for mid/twt, I can't hear it, but if it is clipping it is the typical valve situation of gradual less obvious clipping, until you reach the extremes.
When balancing the levels of mid/twt to bass, I have to attenuate the 12w valve amp, as its output is too loud. This is due to a combination of driver sensitivity and the gain of the respective amps. The valve amp has relatively high gain and typically class D are lower gain. Gain is the multiplying factor of the Amp.
I also use a Linkwitz Transform circuit on the bass at line level, it gives a 10dB boost at 20Hz giving my sealed box 12" driver a flat response to 21Hz and an f3 of around 18Hz, so a Sub is not needed here.
With a LT circuit, for every 3dB in boost, you double the watts required at that frequency, so x2x2x2 would be appropriate for a 9dB boost. The headroom on my class D comes into play here.
Your source output level is part of your total gain chain, is it a line level signal like a phono stage, or a hot output from a modern DAC. The power amp is a multiplier so what goes in, dictates what comes out. Its sensitivity comes into play here.
For good bass at high SPL you need plenty of watts and current on hand.
The upper frequencies are far less demanding.
So driver sensitivity, amp gain, source signal strength, room size and your take on what an acceptable SPL is, are all part of the equation.

[Filterlab]

Doh, :doh: I need to learn to read more carefully.

You know NP likes to tailor his sound?

I do. I have one to listen to in my system available, so I'll do that before committing to a purchase. I'm not in a hurry, plus Edward's Neurochrome 686 is on its way to me in the meantime for a week or so for a bit of a listen. :)

[Macca]

Will await your write-up with interest. :)

[Filterlab]

Me too. :)

[cooky]

Sound pressure level (SPL) falls off as the inverse square of the distance. So compared with that at 1m (as quoted in your speaker sensitivity of 95dB/W), listening at double that distance of 2m will reduce the SPL by a factor of 4, or 6dB, to 89dB/W. Thus trebling the distance to 3m will reduce the SPL by a factor of 9, or 14dB, to 81dB/W.

Your amp can produce 60W/channel (or 17.8dBW), so the maximum SPL from each speaker will be 81 +17.8 = 98.8dB, and since there are two speakers an SPL of 101.8dB in total.

102dB (above the threshold of hearing) is classed as very loud (https://audiology-web.s3.amazonaws.com/migrated/NoiseChart_Poster-%208.5x11.pdf_5399b289427535.32730330.pdf) and if maintained at that level (assuming the amplifier doesn't overheat) would cause some hearing loss after about 10 minutes.

Or to put it another way - you have plenty of power for your needs, provided you don't listen to continuous sine waves at a high level for long periods of time.

Slight calculation error above: 95dB@1=89dB@2m=83dB@4m= 85.6dB@3m so max from a pair is 85.6+17.8+3=106.4dB. Even more reasons to look after your hearing.

[Audioflyer]

I found this interesting on YouTube.

https://www.youtube.com/watch?v=vaiEDYB5c9M

[Macca]

I found this interesting on YouTube.

https://www.youtube.com/watch?v=vaiEDYB5c9M

As someone says in the comments I'd like to see him try that again with an amp that has a maximum output of 1 watt.

If I am using amps with level meters (and with more slightly more efficient speakers in a smaller room than his), it is true that most of the time less than a watt is being used. But you can see on the meters that occasionally 40 watts and more are used on peaks. Knock the sensitivity down 3dB and that would be 80-plus watts on peaks.

I worked out long ago I need at least a 50 watt amp to get the levels I like without clipping. And I don't listen at high volumes.

[Pigmy Pony]

Like a car with a big powerful engine, you don't need to drives at ten tenths to feel the benefit :)

[Macca]

Like a car with a big powerful engine, you don't need to drives at ten tenths to feel the benefit :)

“The pace of the Megane is too leisurely to be called quick. Uphill runs become power sappingly mundane whilst overtaking National Express coaches becomes a long, drawn-out affair. Not my words, Carol, those are the words of Top Gear Magazine.”

[anthonyTD]

With any class of amplfiier other than class A, power supplies, and their ability to deliver instant current at a sustained constant voltage becomes all important! :)

[Edward]

I find the online calculators useful to give a ballpark amp wattage required.

such as https://www.extron.com/calculators/amplifier-power/?tab=tools

[Filterlab]

8 watts then. :lol:

[anthonyTD]

Mine was around 15 watts for 93db, with 6db headroom!

[Edward]

8 watts then. :lol:

So 400 W into 4 Ω will be enough then? :)

[Filterlab]

I think it should suffice. :D

[Pharos]

I used to run a 10W class A amp at just below clipping and get 103dB. I think that this factor is exaggerated in importance, but some headroom id needed.

If the speakers are a difficult load, for example one which produces such a difficult phasing of current that it becomes very high, current delivery is a factor. But this is a different consideration from having enough power to follow peaks.

I went in the 70s for an interview with Redifusion, Orpington, and they said that their headroom was running only 1dB higher than the program peaks.

[Barry]

Slight calculation error above: 95dB@1=89dB@2m=83dB@4m= 85.6dB@3m so max from a pair is 85.6+17.8+3=106.4dB. Even more reasons to look after your hearing.

Oops! - my mistake :o. You are correct, a factor of 1/9 (= 1/32) correspond to -9.54dB.

Moral: avoid doing mental calculations after half a bottle of wine! :doh:

[Macca]

I used to run a 10W class A amp at just below clipping and get 103dB. I think that this factor is exaggerated in importance, but some headroom id needed.

If the speakers are a difficult load, for example one which produces such a difficult phasing of current that it becomes very high, current delivery is a factor. But this is a different consideration from having enough power to follow peaks.

I went in the 70s for an interview with Redifusion, Orpington, and they said that their headroom was running only 1dB higher than the program peaks.

I don't think it is exaggerated, although I have noticed that people don't seem to notice when their amp is clipping on peaks. I notice and when I had the cat, who would sit and listen with me, he would react to the clipping. I'd say 10-14 dB of headroom is needed for hi-fidelity.

I'd guess 1970s analogue TV sound was heavily compressed, back then you had one little elliptical speaker in a TV and about a 4 watt amp so it needed to be.

[Pharos]

I used that Nelson-Jones amp with Tannoy Gold Lancs, and had a PPM, so peaks were accurately measured, and the Quad 33's volume pot was at just over 8 1/3, if I went higher it got rough. So as long as clipping is avoided there is enough headroom.

[bumpy]

I use a low powered valve amp of 1.8wpc on a variety of (efficient) drivers. There is always a fear that SQ is subtly affected as the amp begins to run out of steam, not enough to be an annoyance, but enough to negate some of that extra money spent to squeeze out the last bit of SQ.

My simple tip is to wind the volume well past where you normally listen and retreat outside the room where distortion remains quite noticeable. The sound should remain sweet enough to invite you back in.