Pro audio amps

[jared555]

So what is the real quality difference in a pro audio amp and a home audio separates amp? The main thing I notice is that the THD is usually 0.1% or so with the pro audio

 

[WmAx]

So what is the real quality difference in a pro audio amp and a home audio separates amp? The main thing I notice is that the THD is usually 0.1% or so with the pro audio

Actually, distortion is typically far lower than 0.1 %; that percent rating is just a reflection of the power rating method they typically use.

Pro amps may be built with higher quality PCB boards(to withstand physical shock/abuse), have a stronger chassis and be designed to output high power for long durations. One common difference is that most of the pro amps have fans that can be a source of distraction in home applications. On some amps, you can get silent replacement fans. You usually get far higher power for your dollar with pro amps.

For reference, year ago, I used to use McIntosh amplification. When I realized that the only substantial thing offered by the McIntosh (and other high end offerings) was a very pretty looking chassis, I sold them off. Today, I use mainly pro amplifiers and could not be happier with their performance.

-Chris

 

[jared555]

So what % THD is typically actually noticable? And do you add the % from each component or do something like multiply the inverses together?

 

[WmAx]

So what % THD is typically actually noticable? And do you add the % from each component or do something like multiply the inverses together?

Harmonic distortion can not be said to be audible at any specific minimum value unless many conditions are known. But to be clear, the typical THD of a properly designed, properly operating amplifier is several magnitudes below audibility for the purposes of music playback. However, assuming average harmonic spectrum profile of an average solid state amplifier, it is generally agreed that over 1 percent THD would be required to become audible to the most sensitive listeners for musical playback purposes. But in a non typical situation where the spectrum of harmonics of the distortion spread into high orders, a much lower percent value could become audible.

As for as distortion summing, if two components(for example, the pre-amp and then amp) happen to have exactly the same distortion profile, this would cause distortion to increase by 6dB relative to the main signal, there by doubling distortion magnitude. In reality, the distortion profiles are not likely to match up this close, there for distortion would not increase by this much.

-Chris

 

[jared555]

So what equipment do you use? (amps, speakers, processor are the main things I am wondering about)

 

[WmAx]

So what equipment do you use? (amps, speakers, processor are the main things I am wondering about)

Well, the system where I use the pro amps is my computer audio monitor system, and the speakers are DIY/heavily modified retail speaker, with an objective response superior in most aspects to most audio monitors used in most studio monitoring systems, and the processor is a Behringer DCX2496, the tweeter amp is a Crown XLS202D, the midrange amp is a Crown XLS202D and the woofer amp is a Behringer EP2500.

-Chris

 

[jared555]

any particular reason for those choices of brands for amps?

 

[cbraver]

As far as the fans, both the Crown and Behringer amps have easy fan mods. I've never opened up a QSC, but maybe someone else could chime in if they have modded one. I replaced the fans in my XLS402 the other day and now it's silent. Took about 20min, including heating the soldering gun. haha.

Stock, though, both of those are pretty noisey if you keep you're equipment near you. If it's in an equipment closet it's a non-issue.

The Crown XTi series amplifiers are more expensive, but the fan's aren't triggered until 50C stock, and with the new firmware you can adjust the fan triggers. Same with the DSi's.

What it comes down to is for under a grand bucks you can have a Crown XLS (fyi, http://www.thx.com/products/professional/pdf/ApprovedEquipList.pdf) or Behringer Europower 5.1 system. For under two grand you can have a full Crown XTi 5.1 setup. Add an extra amp for 7.1, *shrug*. It's just a good deal.

 

[jared555]

Thanks, so why is it that more people don't go the route of pro audio compared to the home audio when it comes to some of the electronics?

(Looking at I think the emotiva amp that is 1000 watts bridged.... that seems extremely common with pro amps)

 

[cbraver]

Thanks, so why is it that more people don't go the route of pro audio compared to the home audio when it comes to some of the electronics?

(Looking at I think the emotiva amp that is 1000 watts bridged.... that seems extremely common with pro amps)

Well, they are intended to be in an equipment both of a movie theater, nightclub or on a rack of a stage... so they are ugly and noisier. Even if you mod the fan, there is no doubt that pro-equipment doesn't look as nice as consumer equipment (look at my signature link). Also, if you design a system using 2-channel pro-amps, you're generally going to need an equipment rack and it simply takes up more space. The alternative is buying a Denon receiver or something that has everything contained in one box and conduction cooled. Then tucking the gear away in cabinet or something isn't so hard. Also, some people believe that pro-amplification is overkill and not neccessary.

 

[jared555]

Unfortunately I am fairly used to fan noise.... my room actually sounds strange without it.... I even have to adjust my computer/receiver's sound output when the "server" that normally sits behind me is off. I have a fan controller on my main system.... if I turn the fans up to max (temperatures aren't affected so I never do) and have my door open I can here them 2 rooms away.... not too bad normally though.

I am looking at going rackmount for my computer equipment eventually. I know I am odd but I think some of the rackmount amps look cool. If I felt like voiding the warranty on them I could just stick some LEDs or a cathode light inside and do watercooling LOL

Why would pro audio be overkill/not necessary when you can get similar wattages as the home audio separates for the same price or cheaper?

Amps are way down the line for me though (my onkyo receiver hooked into my parent's floorstanding speakers is incredible, so I know better speakers will help a lot)

 

[cbraver]

Unfortunately I am fairly used to fan noise.... my room actually sounds strange without it....

Well, lowering the ambient noise in you're room allows you to keep the volume lower. Also, it's distracting to some people who enjoy classical recordings and such, or quiet moments in film.

I am looking at going rackmount for my computer equipment eventually. I know I am odd but I think some of the rackmount amps look cool. If I felt like voiding the warranty on them I could just stick some LEDs or a cathode light inside and do watercooling LOL

For work my computer is a rackmount and I'll probably eventually throw a 202 in there to power a pair of bookshelves I have. I wouldn't recommend watercooling you're amplifier, some quiet fans will be more than enough.

Why would pro audio be overkill/not necessary when you can get similar wattages as the home audio separates for the same price or cheaper?

Well, you generally end up with more power for less money. Some say the power isn't neccessary based upon the wattage required to drive their speakers to the levels they desire.

Check this article out:
http://www.crownaudio.com/amp_htm/amp_info/how_much_power.htm

And this power calculator:
http://www.crownaudio.com/apps_htm/designtools/elect-pwr-req.htm

 

[fmw]

Let me add some comments to support what Cbraver offered. Let's take a speaker system with average sensitivity. Let's say its sensitivity is 90 to 95 db. That measurement corresponds to applying a test signal to the speakers with 1 watt of amplifier power and measuring the resultant signal's sound pressure 1 meter from the front of the speaker.

If you didn't know it, 90 to 95 db is loud. And this would be a continuous signal, not an average one. If you want to raise the volume level to double that continuous signal that would put it at an ear splitting 180-190 db. Trust me you don't want to be in same room with that loud a signal. Not at 1 meter listening distance or 5 meters or 10 meters. What would it take to double the sound pressure. Why, 10 times the power actually. We would need to apply 10 watts to the speakers at 1 meter of listening distance.

So why do audio nuts have 100 watts per channel and feel they need 200? good question. If the speakers are less sensitive then we need more power. Let's run them down to and 80 db sensitivity rating. That's still reasonably loud and we still need only 1 watt to handle it. We would need to double our amplifier power for each 3 db of increased sound pressure level. That means our 1 watt of power would have to become 6 or 8 watts to reach the 90-95 db level of the more sensitive speakers. Doubling that sound pressure level would require 60 or 80 watts to break your ear drums.

Remember, these aren't average sound pressure levels, they are continuous ones. We are actually using the overhead in the amp.

Trust me, audio nuts have unreasonable opinions of how much amplifier power they need.

 

[WmAx]

the front of the speaker.

If you didn't know it, 90 to 95 db is loud. And this would be a continuous signal, not an average one. If you want to raise the volume level to double that continuous signal that would put it at an ear splitting 180-190 db.

Twice the SPL would be 96-101dB. 6dB = doubling of sound pressure level. 20 log function.

What would it take to double the sound pressure. Why, 10 times the power actually.

It would require 4x the power to double the actual measured SPL. Power to SPL increase is a 10 log function.

-Chris

 

[WmAx]

any particular reason for those choices of brands for amps?

They seemed like reasonable choices, that's all. In hind sight, the Behringer is made to an appreciably higher standard so far as durability as compared to the Crown XLS units. Fortunately, this is a fixed install; I don't have any reason to haul amplifiers around.

-Chris

 

[fredk]

This is an interesting thread. I have been trying to understand amps and power requirements for a while now and didn't quite get it.

Last night I found a power requirements calculator on a pro-amp website here:

(Edit: Sigh can't post links yet...)

crownaudio dot com/apps_htm/designtools/elect-pwr-req.htm

If I understand correctly, to know what your power requirements might be you need to know the following: average listening volume, listening distance, the dynamic peaks above average in your music.

So, if we have a speaker with a sensitivity of 85db at an average listening level of 85db (both reasonable levels), dynamic peaks of 10db, and a listening distance of 8 feet thats a modest requirement of 62 db.

If we bump the dynamic peaks to 15db the power requirement jumps to 198w, a fair amount of power to deliver.

What happens if you are in a larger room and you are 12 feet from your speakers (still a reasonable disance)? Now you need 285w to produce all the music cleanly. Thats a fair chunk of power.

If you like to get that 'concert hall' feeling in your livingroom when you listen to music I don't think the last scenario is unreasonable.

FWIW, the page that links to the calculator is a very interesting read. It gives you an idea of what sort of volumes and peaks you can expect from different types of live music.

For instance: "Because music has transient peaks that are 6 to 25 dB above the average level, the power amplifier needs to produce enough power to handle those peaks without distortion."

Here is another one to think on. Do you think of folk music as ever being loud?
"Listed below are typical sound pressure levels (SPLs) for various types of music
Folk: 75-90 dB"

75db is no big deal, but 90db is considered loud around here. How about classical? 100db AND it has much higher dynamic range.

One last gem: "Home stereo: 150 W for 85 dB SPL average (with 15 dB peaks), 1,500 W for 95 dB SPL average (with 15 dB peaks)"

Here is the URL:

crownaudio dot com/amp_htm/amp_info/how_much_power.htm

Fred

Edit: doh!! links are in a post above.

 

[WmAx]

This is an interesting thread. I have been trying to understand amps and power requirements for a while now and didn't quite get it.

Last night I found a power requirements calculator on a pro-amp website here:

It should be pointed out that the calculator you referenced does not account for factors at play in a domestic listening environment. Consider the following.....

1) Distance vs. SPL compensation: In a listening room, due to the complex interactions of the room, typically SPL reduces 3 to 4 db per doubling of distance with a practical point source, vs. 6db reduction per doubling of distance in a free field environment or auditorium.

2) In stereo, the 2nd channel adds 3-4dB to the average SPL.

3) The room re-enforcement acoustics add about 2-3dB to the sensitivity, overall, in the mid-treble bandwidth. In the sub-bass range, 10dB gain in sensitivity is possible.

Considering the above factors, in an average size domestic room, at 3 meters to listening position, in stereo, 1 watt per channel would produce about 88-90 dB, with 90dB 1W/1M speakers.

-Chris