Understanding power amps and how they interact with speakers

[Sal1950]

My amp..,

A very clean well laid out chassis keeping the power supply distantced from the input and lots of room for air circulation. All things being equal should be a long lived design.
Mine look very similar.

 

[Cosmik]

Maybe this whole discussion is like comparing a V8 to a hybrid vehicle. Not only does it turn out that a 'divide and conquer' approach can make the system more efficient, it can also make it more powerful overall, and introduces opportunities for subtle dynamic tweaks that improve handling and stability.

Porsche expects the 918 Spyder to emit 70 grams of carbon dioxide per kilometre travelled, which is about the same as the output of a tiny city car. Yet it will be able to accelerate to 100kph in under 3.2 seconds (a second faster than a Porsche GT3 with a combustion engine) and will have a top speed of more than 320kph. Moreover, if driven carefully, it will consume just 3 litres of petrol per 100km (or 78 miles per American gallon).

Porsche and Lotus both use a trick called “torque vectoring” to improve handling. When wheels are being driven directly by electric motors, different levels of torque can be applied to improve stability on corners. At low speeds, torque vectoring can be used on the Porsche to assist with steering by powering the rear wheels at different rates to create a turning action. This can make parking easier.

A few of us here will already have made the move into the hi fi equivalent of the hybrid vehicle: DSP active. The Beolab 90 and Kii Three are two examples where the interaction of the amp and speaker is hardly worth commenting on: the amp only has to handle a small portion of the signal and only has to drive a single drive unit so the load is trivial. In such speakers, the amps are regarded as simple, scalable building blocks, which makes a conventional amplifier look quaint and primitive. No doubt people will point out that driving a V8 is a lot of "fun" even if it is slow and inefficient, but that is elevating the foibles of the hardware itself above the end result - something that I think the world of audio is thoroughly confused over.

 

[Fitzcaraldo215]

Recommended Amplifier Power 20‒500 watts per channel

My amps are rated for 700@4 ohms, but the wall outlet's breaker will pop before those levels are ever seen here.

The amps claim 1700W maximum draw, they are both on a single 1800W circuit (15A x 120V) along with all the other AV gear and some of the kitchen.

If I listen while the kitchen overhead tubes (240W) and the PC (300W or so) are on and run the vacuum cleaner (750W) the breaker has popped.

I figure a big double handful of watts going to the speakers is about right for loud listening here.

(They aren't green, I know - 100W each at idle, and good for a couple of watts output, with, I think, seven levels of increasing bias, and corresponding increases in draw and output above that. I usually listen with occasional jumps into bias level 2, 3 is loud 4 is real loud. The highest draw I've seen is 500W each, and they get warm quickly)

Ray - I had Krell KAS-2 monoblocks for about 15 years. 175w/350w. I replaced them with an Ulrick-designed Spectron Musician III Class D about 6 years ago, which is 600/900w. It was then that I saw my electric bill drop by about 15-20%, as I recall. I did not need or hear hear any added dynamics, though, via my own Martin Logans. I did like the sound of the Spectron better, though. And, the Krells still had some decent resale value.

But, I have always had multiple 20A circuits put in. In my current home, there are 4 dedicated circuits plus 1 normal wall outlet circuit. The dedicated circuits are all identical in length and terminate on adjacent breakers and adjacent neutral and ground connections at the box. Nothing fancy. Same electrical phase, of course. No breaker has ever tripped. The XLR interconnected system is dead silent.

I use the circuits as follows:

1. Main amp - Spectron
2. Subwoofer JL Audio f113 - 2,500 watts peak
3. Front end gear - DAC, TV plus center amp(Bryston Powerpac 120 - 120/200w)
4. PC, NAS, etc. (in the adjoining utility room)

The other 15A room circuit powers 2 Parasound A23 stereo amps (120/200w) in the back of the room for the surround and back channels (7.1) plus lighting.

The 4 dedicated circuits are probably overkill, but it was not that much more expensive vs. installing just one.

 

[RayDunzl]

The 4 dedicated circuits are probably overkill

That would be my guess, too.

I saw my electric bill drop by about 15-20%

I bought some shares in the local electric utility and let the dividend (about 5%) pay the bill. The very interesting part of that is they are being acquired and I'll get a $20,000 capital gain. That will pretty much cover all my hardware purchases, ever, to date.

"Emera said the $27.55 a share it will pay for TECO is a 48 percent premium to the Tampa power company's closing stock price on July 15, 2015."

Had I not bought the power-hog amps I probably wouldn't have parked idle funds in the shares.

 

[Sal1950]

The 4 dedicated circuits are probably overkill

That would be my guess, too.

Hey, If ya got it, flaunt it. You can never have too much clean power.
Besides it's been proven that fuses vary in resistance with current draw and modulate all the functions of a audio system. Kind of like inverse global feedback at it's worse.
The more you can distribute the load the better.

And Ray, since you own stock, will you talk to the power company about re-instating the 5 free light bulbs a month deal. Now a days they want me to purchase these new $10 a piece, high tech, florescent or LED bulbs that won't even fit into half my table lamps or light fixtures. I mean they're still only light bulbs for Gods sake.

 

[Blumlein 88]

If you look at the amount of Acoustic Power actually radiated, virtually all of the electrical power supplied goes up in heat.

http://images.klipsch.com/Brochure_491101_635164772981548000.pdf

Klipsch claimed near 50% for a portion of their famous Khorn's range. 15 watts in for 7 acoustical watts out.

I know someone with some nice Khorns that use a 20 watt class D amp with them. I guess that is a green option.

Edit to add: I think Klipsch may have been guilty of a little marketing hyperbole. Likely they can put out more like one acoustical watt which is impressive itself. That is roughly the power of a full symphony orchestra according to some sources.

 

[NorthSky]

 

[Phelonious Ponk]

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It's kind of frightening to imagine some poor bastard sitting in the sweet spot between those behemoths. Maybe he's getting excellent fidelity, maybe not. But he won't be able to hear it for long.

Tim

 

[NorthSky]

From the pics it looks like extra care was taken in the interaction between speakers, power amps, and the room.

* Best would be to assist in person in order to experience the magnitude of the listening apotheosis.
I can imagine a rock music recording sounding like a live music concert.
...Or being @ a live classical opera concert hall.

Yes, the pics open our imagination. When I saw them I thought they were appropriate to show the meticulous dedication of some in "marrying" the speakers to the power amps. Are the speakers too big? No. Are there too many power amps? No. ...But anyone else is free to think the opposite. It's only a picture; no one was there to report his listening impression, or to take measurements @ both low and high volume.

There are no music sources; no turntable visible in that pic, no open-reel-tape deck, no CD player, no separate DAC, no digital music server box, no laptop, no power purifiers, no power cords, no emphasis on cables (XLR balanced interconnects are used though), ...the pic is for the speakers and power amps interaction.
It seems to be about right.