Quiet pro amps?

[Verdinut]

Aren’t most pro audio speakers very high sensitivity?

Yes, most pro audio speakers feature high efficiency. Oh, I don't like the the term sensitivity for a loudspeaker, simply by the fact that a speaker is a converter; it converts an AC current into a sound wave. IMHO, it is more appropriate to use the word efficiency. I don't know who suddenly decided that efficiency was not right term but sensitivity was.

By the way, for the 12v trigger for a pro amp, Amazon have a
Xantech AC1 Controlled AC Outlet.

It has been discontinued by the manufacturer, but you can get one if you don't hesitate too long. They have a few left for around $115 apiece.

For your question about quiet pro amps, the QSC DCA (Digital Cinema Amp) Series are rather quiet amps. If you prefer Class A/B amps, the Model DCA1222 provides a clean 325 watts/ch at 4 ohms. It is cooled by a rather silent variable speed fan.

I am at present using two of those 2 channel amps for my front left and right actively biamped speaker enclosures. My listening position is 6 feet away from the fans and I can't hear them. I intend to purchase a third one to drive the front center system also in a biamplified configuration.

Those cinema amps are actually being used in many theaters in the US and in Canada and they provide an excellent and reliable performance. They are also manufactured in the USA. They are not normally sold in musician's or pro audio shops, but a few on line stores in California sell them or a distributor which you can find on QSC's website. For instance, the DCA1222 retails for over $900 in US but two stores in California were asking $729 when I recently looked on their websites.

 

[lovinthehd]

Sensitivity vs efficiency are basically different measurements that indicate the same thing but if one says 92dB that's sensitivity, not efficiency. Sensitivity is generally provided with speakers, not efficiency. Here's one explanation http://www.sengpielaudio.com/calculator-efficiency.htm

 

[Verdinut]

Sensitivity vs efficiency are basically different measurements that indicate the same thing but if one says 92dB that's sensitivity, not efficiency. Sensitivity is generally provided with speakers, not efficiency. Here's one explanation http://www.sengpielaudio.com/calculator-efficiency.htm

I agree most of the time with you, but this time I don't. In the 1950-60's, there was never a mention of sensitivity in speaker drivers. Altec, JBL and other serious manufacturers were always talking about efficiency. As I said, I don't know what smart aleck decided to replace efficiency with sensitivity.

In fact, the efficiency then was published in decibels for a 1 watt input at 4 feet for instance, which is less confusing than using a voltage input which changes the figure depending on the transducer's impedance. For amplifier output, we use watts, but why don't we still use watt input for a speaker?
Not very coherent, is it?

For a converting devise, you want to know how efficient it is in converting. Sensitivity is a misnomer IMO.

 

[lovinthehd]

I agree most of the time with you, but this time I don't. In the 1950-60's, there was never a mention of sensitivity in speaker drivers. Altec, JBL and other serious manufacturers were always talking about efficiency. As I said, I don't know what smart aleck decided to replace efficiency with sensitivity.

In fact, the efficiency then was published in decibels for a 1 watt input at 4 feet for instance, which is less confusing than using a voltage input which changes the figure depending on the transducer's impedance. For amplifier output, we use watts, but why don't we still use watt input for a speaker?
Not very coherent, is it?

For a converting devise, you want to know how efficient it is in converting. Sensitivity is a misnomer IMO.

LOL I'm not defending it but this is the breakdown I've used and seems to be favored. Since they can be converted to each other it's more a matter of what scale you're used to thinking of it as. That efficiency would be expressed not in dB but percentage as it expresses a ratio makes complete sense to me....

 

[Verdinut]

We can't ignore the fact that some speaker manufacturers will quote the sensitivity for a 2.83 volt input while others will quote for 1 watt input.
That implies a +3dB difference for the 4 ohm driver in comparison with the 8 ohm one, as it receives 2 watts rather than 1.

 

[lovinthehd]

We can't ignore the fact that some speaker manufacturers will quote the sensitivity for a 2.83 volt input while others will quote for 1 watt input. That implies a 3dB difference between the 4 ohm and the 8 ohm impedance transducers.

Ok, but who particularly does this? If the spec is defined (hopefully 2.83V/1m) it's one thing of course vs one that just provides a number in dB alone, too. Then again impedance varies Having comprable specs can be a challenge, tho....

BTW I took that sensitivity vs efficiency thing from a post where you were endorsing the link

 

[agarwalro]

I thought Sensitivity pertains to a single driver while efficiency is for the complete speaker (driver, crossover, losses, etc.). I suspect the marketing teams adopted sensitivity metrics over an efficiency standard as a means to obfuscate speaker load on amps.

 

[slipperybidness]

I have the XLS 2502 and I love it, but it does have a hiss in the speakers, not a real loud hiss, but you can hear it in the background.

Hiss is typically a gain structure problem. You should be able to eliminate hiss with a properly set gain structure.

i.e. you have too much gain

 

[panteragstk]

Hiss is typically a gain structure problem. You should be able to eliminate hiss with a properly set gain structure.

i.e. you have too much gain

Yep. My XLS1500 has no audible hiss. I don't think I've ever heard the fans turn on either...

 

[equate]

From your seat?

Yes. Barely.

 

[equate]

What speakers? Could be an issue with very high sensitivity speakers, but then so can other amps....

Magnepan MMG

 

[AcuDefTechGuy]

I have the XLS 2502 and I love it, but it does have a hiss in the speakers, not a real loud hiss, but you can hear it in the background.

I've heard plenty of tweeter hiss from Emotiva and Classe Amps and the XLS2500 I used to own made the same tweeter hissing sound. I bet some other amps have that hiss.

 

[lovinthehd]

I thought Sensitivity pertains to a single driver while efficiency is for the complete speaker (driver, crossover, losses, etc.). I suspect the marketing teams adopted sensitivity metrics over an efficiency standard as a means to obfuscate speaker load on amps.

Never heard this one before, altho that marketing efforts have confused the terms wouldn't surprise me a bit. Sensitivity is a measure of a speaker or driver at 2.83 volts at one meter expressed in dB, efficiency is a ratio of input power to output power expressed as a percentage. You can convert back and forth between the two measurements, though.

 

[lovinthehd]

Magnepan MMG

Wonder why, those are far from high sensitivity speakers....suspect also gain structure issues.

 

[Verdinut]

Wonder why, those are far from high sensitivity speakers....suspect also gain structure issues.

Gain structure issues or bad amplifier design.

On the other hand, a slight hiss is far less objectionable than hum!

 

[Verdinut]

Ok, but who particularly does this? If the spec is defined (hopefully 2.83V/1m) it's one thing of course vs one that just provides a number in dB alone, too. Then again impedance varies Having comprable specs can be a challenge, tho....

BTW I took that sensitivity vs efficiency thing from a post where you were endorsing the link

Here is an example for a spec sheet with sensitivity for 1 watt input:
https://solen.ca/wp-content/uploads/6891220.pdf

 

[PENG]

We can't ignore the fact that some speaker manufacturers will quote the sensitivity for a 2.83 volt input while others will quote for 1 watt input.
That implies a +3dB difference for the 4 ohm driver in comparison with the 8 ohm one, as it receives 2 watts rather than 1.

Either way should be fine as long as the so called "nominal" impedance is also specified. Either way would not be as useful if the nominal impedance (preferably the impedance vs frequency graph) is not specified.

Speakers are powered by amplifiers after all; and amplifier outputs are normally specified in watts into specified impedance values, so it does make some sense to specify loudspeaker's sensitivity in dB/W/1m, again, as long as we know the nominal impedance/impedance vs frequency graphs, we can figure things out either way.

I have no issues with, and actually prefer, the voltage sensitivity method, i.e. 2.83V/1m, but that's just a preference. If we are going to relate the specs to amplifier power output requirements anyway, we still need to know the nominal impedance/impedance vs freq graph or at least the minimum impedance/dips. So, whatever turns you on more.

 

[PENG]

Here is an example for a spec sheet with sensitivity for 1 watt input:
https://solen.ca/wp-content/uploads/6891220.pdf

So do PSB, Monitor Audio, and I am sure there are many more manufacturers who still use the 1W/1m method. See also post# 37.

 

[William Lemmerhirt]

FWIW, I use a Yamaha p2500s. No hiss, or hum or fans. Just good clean power. You can usually find them on eBay for a good price.
https://www.crutchfield.com/p_845P2500S/Yamaha-P2500S.html

 

[Verdinut]

FWIW, I use a Yamaha p2500s. No hiss, or hum or fans. Just good clean power. You can usually find them on eBay for a good price.
https://www.crutchfield.com/p_845P2500S/Yamaha-P2500S.html

FYI, that product is discontinued, but someone can still find a few new ones on eBay.

Are you sure it has no fan? Maybe you never heard it run? Yamaha specifies variable speed fans for their P Series amps.