amps and ratings?

[Scp53]

thanks to all for imput. im learning a LOT

scp53

[michael hurd]

Read the full review http://www.jbl.com/car/featured/sponsors/hot_news/JBLA6000GTireview.pdf

[psg]

On 11/19/2004 2:19:01 PM Colin wrote:

A truly powerful amplifier has twice as much power into 4-ohms as it does into an 8-ohm load. A super amplifier, like the Pass x250 (EnjoyTheMusic.com review on classic Klipsch corner Khorns, see archives) has even more power: twice as much yet again into 2-ohms!

On the www.quebecaudio.com forum a few days ago, someone was bragging that he was going to buy a CREEK A50I integrated amp and posted a picture and specs, which included:

Power output (both channels) 50W into 8 Ohms -

Power output (one channel) 60W into 4 Ohms -

Max current > 18 amps -

I posted that it wasn't encouraging that such an expensive amplifier has poor lower impedance specs; it can't drive nearly double wattage into 4 ohms as it does into 8 ohms (into a single channel at that!), and yields only 18 amp of current. My much much cheaper h/k avr-325 pumps out 35 amps.

I was shot down by snob audiophiles that say there's more to an amp than specs and so forth. Perhaps, but I think it should at least begin with good specs (otherwise why even post them?). A cheap amp that doesn't sound very good might also have managed to get good specs, but I think a amp without them probably isn't very good to begin with.

[dodger]

Hi Colin:

Same gray hairs, same remembering the battle of the ratings.

RMS can be measured and applied to any amp.

We agree on 99 % I remember the IHF, EMI, Total Output (that one was funny.)

I get the feeling the question was aimed toward automotive stereo.

You're dead on in tweaking, room acoustics - see my sig - and horns.

I should have qualified my answer to actual listening besides looking at numbers.

The same is to be said for car automotive, with one important factor - ability to hear emergency vehicles sirens while listening. I am amazed that there has not been a higher number of collisions.

It seemed that the question was car audio. That also brings speakers into the factor.

When the switch was made from any of the other ratings, RMS (root mean square) was a more an Industry wide reliable figure. So we could go back and measure RMS from any amplifier made. Distortion and Total Harmonic Distortion figures can be looked at - but should be across the entire spectrum. McIntosh tubed amplifiers have a high distortion and THD amount be do sound well with horns as they are not being pushed to their maximum power ratings, whether thay are IHF, EMI, Total Output Power, or RMS.

So no real disagreement, just how I viewed the question as stated in the first paragraph.

dodger

[dodger]

Hi Colin:

Same gray hairs, same remembering the battle of the ratings.

RMS can be measured and applied to any amp.

We agree on 99 % I remember the IHF, EMI, Total Output (that one was funny.)

I get the feeling the question was aimed toward automotive stereo.

You're dead on in tweaking, room acoustics - see my sig - and horns.

I should have qualified my answer to actual listening besides looking at numbers.

The same is to be said for car automotive, with one important factor - ability to hear emergency vehicles sirens while listening. I am amazed that there has not been a higher number of collisions.

It seemed that the question was car audio. That also brings speakers into the factor.

When the switch was made from any of the other ratings, RMS (root mean square) was a more an Industry wide reliable figure. So we could go back and measure RMS from any amplifier made. Distortion and Total Harmonic Distortion figures can be looked at - but should be across the entire spectrum. McIntosh tubed amplifiers have a high distortion and THD amount be do sound well with horns as they are not being pushed to their maximum power ratings, whether thay are IHF, EMI, Total Output Power, or RMS.

So no real disagreement, just how I viewed the question as stated in the first paragraph.

dodger

[michael hurd]

Rms into 1khz, or 20-20 khz? Driving resistive loads or reactive loads? There are many ways manufactures can derive " rms " measurements that are far from the truth. Driving a purely resistive load is an easy task for an amplifier, especially if there is a simple sine wave involved at a fixed frequency like 1 khz.

Take an amp that "measures" 100w into an 8r pad, with a 1 khz sine, and put it on a reactive load ( moving coil loudspeaker ), like a large diameter woofer in a ported enclosure. Drive it to dervived rms power with a complex low frequency signal, and see how much distortion goes up.

[michael hurd]

"A truly powerful amplifier has twice as much power into 4-ohms as it does into an 8-ohm load. "

Mostly correct. Due to increased thermal dissipation and increased internal resistance, most amps will not quite double the wattage into half the impedance.

Again, this can be fixed in amplifier "specmanship". How can you advertise a 200 watt amplifier that doubles it's wattage into half the impedance? Call it 200 watts into 8r, when it can actually put out 280 watts into 8r, and only 400 into 4r.

[dodger]

I believe it was 1000 HZ into resistive loads. Not truly the full 20 - 20,000 HZ.

That's my memory. I have all of the Audio and Stereo Reviews that have the glossarys going back to 1966.

But I believe Colin could answer that, saving me from the dust .

dodger

[michael hurd]

In the car audio world, there is a new standard emerging, which is a more realistic portrayal of the actual output power of an amplifier. You can read about this new standard here:

http://www.jbl.com/car/support/AUTOMEDIA_CEA2006.pdf

[dodger]

In the 1969 "Modern HI-FI & Stero Guide" and the "High Fidelity's 1968 Guide to Home Stereo," both note that RMS, or Continuous Power should be applied to throughout the 20 - 20,000 HZ.

One does note that the usual test is at 1000 HZ.

Both note that RMS is more reliable than IPP - Instantaneous Peak Power. That is one that I had forgotten.

But, both do support both Colin and my sig, that the type of speaker, room acoustics, etc. need to be taken in account.

Also both mention the Physics portion that a 100 watt amplifier will not sound twice as loud. A 3 db gain will be had, but the 100 watts will give more headroom.

Neither note whether the load is resistive or reactive. Though interpretation it would seem resistive.

It is funny to read of high powered amplifiers of 35 watts per channel.

It also makes wish I had invested in tubes. In the "1969 Edition of Stereo, published by High Fidelity Magazine," there is a nice photo of the Klipsch H-700 Speaker - looks like a Heresy to me. They give no further info on it.

Anyone want Genalex Gold Lion Matched Pairs for $29.95 per pair?

They are listed in 2 of the 4 magazines I pulled.

Colin gives a much more understandable and comprehensive explanation in fewer words than any of the 4 regarding power, distortion and high efficiency speakers - afraid to say Horns I guess.

Ah, sweet memories of my younger days. Hats off to you Colin.

dodger

[dodger]

In the 1969 "Modern HI-FI & Stero Guide" and the "High Fidelity's 1968 Guide to Home Stereo," both note that RMS, or Continuous Power should be applied to throughout the 20 - 20,000 HZ.

One does note that the usual test is at 1000 HZ.

Both note that RMS is more reliable than IPP - Instantaneous Peak Power. That is one that I had forgotten.

But, both do support both Colin and my sig, that the type of speaker, room acoustics, etc. need to be taken in account.

Also both mention the Physics portion that a 100 watt amplifier will not sound twice as loud. A 3 db gain will be had, but the 100 watts will give more headroom.

Neither note whether the load is resistive or reactive. Though interpretation it would seem resistive.

It is funny to read of high powered amplifiers of 35 watts per channel.

It also makes wish I had invested in tubes. In the "1969 Edition of Stereo, published by High Fidelity Magazine," there is a nice photo of the Klipsch H-700 Speaker - looks like a Heresy to me. They give no further info on it.

Anyone want Genalex Gold Lion Matched Pairs for $29.95 per pair?

They are listed in 2 of the 4 magazines I pulled.

Colin gives a much more understandable and comprehensive explanation in fewer words than any of the 4 regarding power, distortion and high efficiency speakers - afraid to say Horns I guess.

Ah, sweet memories of my younger days. Hats off to you Colin.

dodger

[Scp53]

michael, thanks for the link

[Arkytype]

There used to be two things in life that got my dander up: Toilet paper loaded bassackwards and the term "RMS power".

After adding a second TP holder for my lovely significant other, that left only the RMS power issue to deal with.

There is no such quantity as "RMS power". You won't find it in any textbook or in the National Electrical Code. You will, however, find it in the sales brochures of most amplifier manufacturers.

McIntosh Laboratories has used the correct power rating terminology of their amplifiers for many years. It is: "Continuous average sine wave power".

While we should measure the voltage across the load with a true RMS voltmeter or the current through the load with a true RMS ammeter, that doesn't mean the resulting power quantity computed using Ohm's law is "RMS watts".

Assuming the source is a sine wave, you are measuring the average power delivered by the amplifier. This is equivalent to the DC heating power delivered to a specified load resistor.

I suspect the RMS power term came into use as a result of the FTC's misguided attempts to standardize power amplifier meaasurements in 1978. Back then, an honest 30 watt amplifier could be rated at some inflated value using the now-infamous Instantaneous Peak Power rating.