What is the sweet spot for WPC?

[wyn palmer]

Why do the subs/bass units affect the power required by the amp driving your main speakers?

It's not about power in reality. It's about voltage. Being able to reproduce very low frequencies means that the very low frequencies remain unattenuated through the reproduction path and they contribute disproportionally to the crest factor due to the essentially 1/f nature of music.
The impedance vs frequency characteristic of pretty well all speaker loads is extremely variable- for example my system varies from c. 1.2kohms to 0.9ohm 16Hz-25kHz, so "power" in the sense used in this thread is a meaningless concept. What is meaningful is the driving voltage, and that is sourced by the AHB2s.

 

[spark1]

It's not about power in reality. It's about voltage. Being able to reproduce very low frequencies means that the very low frequencies remain unattenuated through the reproduction path and they contribute disproportionally to the crest factor due to the essentially 1/f nature of music.
The impedance vs frequency characteristic of pretty well all speaker loads is extremely variable- for example my system varies from c. 1.2kohms to 0.9ohm 16Hz-25kHz, so "power" in the sense used in this thread is a meaningless concept. What is meaningful is the driving voltage, and that is sourced by the AHB2s.

I get that. Disagree that voltage is the only variable. Many amps would be unable to handle the current demanded by the load, regardless of voltage available.

My question was related to my assumption OP was not thinking about subwoofer power requirements...but perhaps he did indeed mean to include them in the calculus.

 

[wyn palmer]

I get that. Disagree that voltage is the only variable. Many amps would be unable to handle the current demanded by the load, regardless of voltage available.

My question was related to my assumption OP was not thinking about subwoofer power requirements...but perhaps he did indeed mean to include them in the calculus.

I didn't say that voltage was the only variable, but that it, not W is what matters as far as crest factor is concerned. The AHB2 can source, if I remember correctly, about 40A. The woofer/sub drivers are their own beasts and they specify maximum "watts" (i.e. voltage) compatible with their driving capability.

 

[Hawkeye83]

I honestly have not studied the science behind this question but I will say I have been surprised many times by an amplifier's performance. I've never run into a situation yet where wattage was too low to be a problem, but I have small rooms and don't listen very loud.

I was SHOCKED at how well this 3.5 wpc Magnavox-mod amplifier (called DGSE1 around these parts) drives my Tannoy Ardens. PLENTY of power for these speakers, in this room.

So yeah my vote is "no sweet spot." Highly speaker and room and preference-dependent. Definitely true that some amps won't work with some speakers though, of course.

 

[peterp1]

To solve for power you need:
speaker efficiency
your distance from the speaker
and how loud (peaks) you want to listen
how much headroom you want

https://www.crownaudio.com/en/tools/calculators


My example with 85 dB speakers, sitting 2.5 meters away and sound levels to 95 dB with 3 dB of headroom calls for 125 watts.

I think that formula very significantly overestimates the watts needed in real-world in-home conditions. The formula is mathematically correct, of course, but that equation only applies when the speakers are in an anechoic chamber -- essentially in open air with no walls or anything else to reflect sound back. All real-world home listening rooms have tons of reflection points and, as a result, the volume does not drop off nearly as sharply with distance as that formula states (because the formula is only true for open air).

Of course, Crown is more focused on PA systems. When you have PA speakers in a very large venue, where there are far fewer reflections, then that formula becomes more directly applicable (for that specific use case).

 

[coonmanx]

I have 91dB/2.83v rms @1m sensitive speakers (equivalent to 91dB/W that is cited here). I drive them using mono Benchmark AHB2s that deliver the equivalent of 360W/ch, also the bass units have 200W/ch class D amps and the two sub woofers are 400W/CH class D.
There are times when the clipping approaching indicators flash on the AHB2s.
That's the cost of being able to get down to 16Hz essentially flat and having high dynamic range music with 20dB crest factors- that means the average power is a few watts RMS, but the peak is 100x as much.

How is your hearing? LOL.

 

[peterp1]

Honestly, for 2-chanel music with typical speakers (sensitivity in the range of 87db or higher), I have never cared about wattage almost at all. I have vintage 20wpc receiver with 86db speakers that goes louder than I need it to without straining. Of course, if you have extremely inefficient speakers, they can suck up power -- but for all but notoriously inefficient speakers, 20 good watts of power is more than enough for me. I choose amps and receivers based upon sound quality only, almost completely independent of power output (unless, of course, the output is extraordinarily low).

 

[wyn palmer]

How is your hearing? LOL.

Some time ago I used a HSU recording of Mahler's song of the earth recorded by the Boston Audio Society where they have a point where a voice is at a known volume referenced to a point in the audience. That allowed me to calibrate the loudness of my system. For a 14bit + recording it has remarkable dynamics and detail- you can hear the musicians entering and leaving by a door clearly positioned at the rear, for example.
Generally it doesn't sound particularly loud, but the dynamics are quite impressive to say the least.
The clip warning lights do flash during those moments.

 

[Akustic]

Depends on the load it's driving.. but

For acoustic suspension boxes ..

Yea,...I'm with you... it's been my experience that about 100wpc is where the typical Acoustic Suspension boxes start coming alive ...
Under 100wpc the bass can be a bit or more than a bit starved,... Also lower power amps lack dynamics in general with an AS system .. until you reach that 75-100 watt range.
Over that you may gain some dynamics depending on the speaker .. maybe not.

I've never owned anything that seemed to need more than 200wpc .. but then I've never owned a 300wpc amp.

Acoustic Suspesion systems are power mongers but..
Non Acoustic Suspension, well port the box and all bets are off ..
And I think that you might be able to drive some horns with a whistle ..

 

[egellings]

Power needed depends on speaker efficiency, room size and listening preferences.

 

[Bill Ashton]

I am quite happy with 28-55 watts RMS, 4 - 8 ohms, within two co-joined 12x13 rooms, normal ceiling height. Never get volume knob level more than 9 -10 o'clock...more than that is just stupid loud.

 

[opnly bafld]

For acoustic suspension boxes ..

Yea,...I'm with you... it's been my experience that about 100wpc is where the typical Acoustic Suspension boxes start coming alive ...
Under 100wpc the bass can be a bit or more than a bit starved,... Also lower power amps lack dynamics in general with an AS system .. until you reach that 75-100 watt range.
Over that you may gain some dynamics depending on the speaker .. maybe not.

Are you saying that you listen at louder levels with AS speakers or that they need to be listened to at higher/loud levels?

 

[A/D/Slover]

200

 

[DirtFarmer]

Alright, perhaps there's no "sweet spot", but is there a wet spot?

 

[Akustic]

Are you saying that you listen at louder levels with AS speakers or that they need to be listened to at higher/loud levels?

Neither one ...

Everyone talks about the db level of the music, but nobody talks about the qualities of the music ..

Acoustic Suspension speakers gain in dynamics and naturalness of reproduction with more power ....
Not sure what to call the qualities that improve separation between the instruments and definition of the notes ... just sounds more natural.
The music is more lively and the bass definition is tighter, quicker, little details come alive...
There is less of the constrained, un-natural sound that says "radio" .... not real music.

I would guess that it's related to available peak headroom ..
And I'm addicted to fast, tight well defined AS bass notes ..

It's easy to hear .. listen to an AS speaker with 20wpc and then upwards of 100wpc ..
It will sound like someone changed speakers on the system ..

 

[opnly bafld]

It's easy to hear .. listen to an AS speaker with 20wpc and then upwards of 100wpc ..
It will sound like someone changed speakers on the system ..

That's why I asked, I had a pair of easy to drive low sensitivity (85) sealed bookshelves and 3 amplifiers, 20, 70, and 300 watts. There was no difference between them in the areas you stated at my normal listening levels.

I can't really understand how having more power than I'm using can automatically make it sound better. If one amplifier is obviously better than another, that can be different. I had a pair of difficult to drive speakers with dual 10" woofers that actually were much better being driven by a 15 watt tube amp than a few 100 watt amplifiers that I tried.

 

[spark1]

That's why I asked, I had a pair of easy to drive low sensitivity (85) sealed bookshelves and 3 amplifiers, 20, 70, and 300 watts. There was no difference between them in the areas you stated at my normal listening levels.

I can't really understand how having more power than I'm using can automatically make it sound better. If one amplifier is obviously better than another, that can be different. I had a pair of difficult to drive speakers with dual 10" woofers that actually were much better being driven by a 15 watt tube amp than a few 100 watt amplifiers that I tried.

Agree. Assuming enough power to achieve desired loudness without clipping, I have trouble understanding claims of excess power improving performance. The amp delivers only the power that is required to fully duplicate the signal. More power is delivered only when the signal demands it. Otherwise, it is not in use and therefore irrelevant to performance.

That said, I do believe that some folks are experiencing minor clipping on a regular basis and not aware of its negative effects, especially if/when listening to high-quality recordings at fairly high volumes (those with a crest factor of 15-18dB, or even more). To me, it is clear that adequate headroom to avoid even minimal clipping will improve sound quality...and if you like to listen to high-quality recordings at levels of 85-90dB at 10-12 feet, having enough headroom to do so with speakers of average sensitivity (86-88dB) requires an amp capable of fairly high power output.

Of course, there may well be a trade off for this kind of headroom, in that a lot of such amps do not have as much finesse and detail as good lower-powered amps when running at lower power levels. Getting one that does is expensive.

 

[coonmanx]

Agree. Assuming enough power to achieve desired loudness without clipping, I have trouble understanding claims of excess power improving performance. The amp delivers only the power that is required to fully duplicate the signal. More power is delivered only when the signal demands it. Otherwise, it is not in use and therefore irrelevant to performance.

That said, I do believe that some folks are experiencing minor clipping on a regular basis and not aware of its negative effects, especially if/when listening to high-quality recordings at fairly high volumes (those with a crest factor of 15-18dB, or even more). To me, it is clear that adequate headroom to avoid even minimal clipping will improve sound quality...and if you like to listen to high-quality recordings at levels of 85-90dB at 10-12 feet, having enough headroom to do so with speakers of average sensitivity (86-88dB) requires an amp capable of fairly high power output.

Of course, there may well be a trade off for this kind of headroom, in that a lot of such amps do not have as much finesse and detail as good lower-powered amps when running at lower power levels. Getting one that does is expensive.

You should know that a statement like "I do believe" is proof of nothing....

 

[coonmanx]

The first watt is the most important...

 

[Akustic]

That's why I asked, I had a pair of easy to drive low sensitivity (85) sealed bookshelves and 3 amplifiers, 20, 70, and 300 watts. There was no difference between them in the areas you stated at my normal listening levels.

I can't really understand how having more power than I'm using can automatically make it sound better. If one amplifier is obviously better than another, that can be different. I had a pair of difficult to drive speakers with dual 10" woofers that actually were much better being driven by a 15 watt tube amp than a few 100 watt amplifiers that I tried.

Depends on your ear I suppose .. we're certainly all differently abled ... so my answer is obviously

Yes, there is a sweet spot for power although the the sweet spot is definitely dependent on the type of speaker load that the amp is trying to drive
The concept of dynamic headroom is certainly real and measurable
...
Arguably watts per channel is a flexible definition depending substantially on the power supply of the amp ..

I've heard it multiple times over the years with differing speakers . but was referring to Japenese receivers with similar designs and topologies .. .
What kind of speakers ??