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Measuring Amplifiers - Page 50

post #1471 of 1917
Quote:
Originally Posted by whoaru99 View Post

I don't dispute any of what you've said, except that more air flow probably equals more noise. Sure, there are some fans quieter than others, but in the same form factor probably not significantly so at any given CFM.

In the PLX amps, there really isn't room for adding more fans or changing the fan layout without significant redesign. Perhaps you already know that...I'm just saying...

That is true, but i meant to specify, more "smaller" fans. Depending on their individual specs, two smaller fans at a lower rpms may be quieter than a large fan at a higher rpm and may reach the same cfm. Then again, the smaller you go generally the more noise you'll produce, so you will probably reach of a point of degradated return. Then again, you could then also cool more key areas directly.
And i've never specifically taken apart of PLX amp myself, but after a quick google of a few models, it looks like it is a bit tight, but you should be able to do it. But these are only guess-timations based on photos, so i'll take your word for it.

"but in the same form factor probably not significantly so at any given CFM."
Quite true, for the exact rpm, size, shape, and design, you don't have too many choices
But slight differences in fin designs and depth can really help with CFM ratings.

"except that more air flow probably equals more noise."
That is not true, except if you're dealing with the same fan. A larger fan can move a ton more air than a smaller fan, and move at a lower rpm, therefore less noise. The rpm's is what creates the noise, the sound comes from the fins cutting through the air. A fan of the same size but with more depth can move more air at a lower rpm, therefore create less noise...etc.
post #1472 of 1917
Quote:


Depth is often a figure that most forget about, this can affect both noise and CFM. Then you also have fin designs and sizes, these also affect the CFM.

Im not forgetting about it, I was being really general when I said "Size"

In the end, you are right with what you are posting but like all cautionary tales (fans, cheater plugs.... Strip clubs) there are those that do and those that worry

My amps have worked well for a while so I have no worries about the choice of my fans.
post #1473 of 1917
Quote:
Originally Posted by penngray View Post

Im not forgetting about it, I was being really general when I said "Size"

In the end, you are right with what you are posting but like all cautionary tales (fans, cheater plugs.... Strip clubs) there are those that do and those that worry

My amps have worked well for a while so I have no worries about the choice of my fans.

True i guess, if you don't worry about any possible downsides, then why not...
post #1474 of 1917
Quote:


True i guess, if you don't worry about any possible downsides, then why not...


If actually downsides results exist then their would be threads on them. The problem with your position is that you have no idea about the specs of the fans in the amps and the fans replacing them. Add to that you also do not know how people run their amps or how they have them installed either. You are just posting hypothetical, which I already said its right but its not real life so its meaningless to us

I would say that Pro-amp fans SUCK because QSC, Behringer, etc do not care one bit about how loud they are, they are just cheap fans. This does mean we can replace them with comparable fans that are just silent and the CFM difference if any isnt very meaningful.
post #1475 of 1917
Quote:
Originally Posted by penngray View Post

I would say that Pro-amp fans SUCK because QSC, Behringer, etc do not care one bit about how loud they are, they are just cheap fans. This does mean we can replace them with comparable fans that are just silent and the CFM difference if any isnt very meaningful.


I think that's taking it a bit too far.

Pro amps are meant for ruggedness and are designed to hold up under less than ideal conditions.

I guarantee you that the replacement "quiet" fan does NOT put anywhere near as much air through the amp as the stock fan, therefore isn't similar in that regard. The "L" fan that has been recommended for the PLXs puts out 24 CFM whereas the stock fan says 53 CFM. So, the quiet fan is only 45% of the CFM and spins at roughly 42% of RPM of the original.

And, as far as cheap goes, the Sanyo Denki original fan lists for $10.76 from Newark, while the recommended quiet replacement fan lists for $9.17 from Newark. Of course, this doesn't reflect large qty. OEM purchase, but the point is that the OEM fan isn't a bargain bin jobbie comparatively speaking.

Is the low CFM fan OK in home use? Yeah...seems to be. Would it work in the design intent of these amps out on the road...unlikely, IMO.

Received another 3402 yesterday that hasn't had a fan mod yet. It blows a very distinct breeze out of the front grille whereas my other 3402 with the "L" fan you can barely feel anything blowing out.

It's pretty easy to see quiet in this case comes from less RPM/less airflow, not cheap.
post #1476 of 1917
Quote:


I think that's taking it a bit too far.

Dont rain on my exaggerations!!!
post #1477 of 1917
There is quite the breeze out of these QSC's, but surprisingly quiet for having 4 fans.

I'm a fan of putting the amps in another room if that's possible.


post #1478 of 1917
In another room with the stock fans would be the best option, I agree.

Is that the PL 9.0, or something else?
post #1479 of 1917
Quote:
Originally Posted by penngray View Post

If actually downsides results exist then their would be threads on them. The problem with your position is that you have no idea about the specs of the fans in the amps and the fans replacing them. Add to that you also do not know how people run their amps or how they have them installed either. You are just posting hypothetical, which I already said its right but its not real life so its meaningless to us

I would say that Pro-amp fans SUCK because QSC, Behringer, etc do not care one bit about how loud they are, they are just cheap fans. This does mean we can replace them with comparable fans that are just silent and the CFM difference if any isnt very meaningful.

Fans are chosen by the engineers to meet the minimum CFM to cool the amp at a minimum during its peak use. They don't just throw fans in there and see if they work.
While i respect your opinion, you're taking the idea a bit too far by saying:
"The problem with your position is that you have no idea about the specs of the fans in the amps and the fans replacing them."
My point was that you should pay attention to CFM, not RPM. Because, whether you realize it or not, CFM can vary widely within the same RPM range. To wide to not worry about it.
As an example, two random fans i picked out:
http://www.newegg.com/Product/Produc...82E16835220024

size: 80mm
RPM: 1600
CFM: 31.52 CFM

http://www.newegg.com/Product/Produc...82E16835226001

size: 80mm
RPM: 1600
CFM: 18 CFM

However, i will admit, the a difference may not be noticed, as it depends on how hard you run the amp and the environment its in. I never stated it was a bad idea to replace the fans with quieter ones, only to match them with equal CFM ratings. If you do that there are no down sides, if you don't, you may be creating some.
But as with all things, its your equipment and your decision. If its your choice i'm not going to argue against it, i just want to make sure you're aware.
post #1480 of 1917
Quote:
Originally Posted by jarrod1937 View Post

My point was that you should pay attention to CFM, not RPM. Because, whether you realize it or not, CFM can vary widely within the same RPM range.


Yup, and you also have to ascertain whether or not the listed CFM is given at same static pressure. That's not alway clear unless you go to the detailed fan specs.
post #1481 of 1917
Quote:
Originally Posted by jarrod1937 View Post

Fans are chosen by the engineers to meet the minimum CFM to cool the amp at a minimum during its peak use. They don't just throw fans in there and see if they work.
While i respect your opinion, you're taking the idea a bit too far by saying:
"The problem with your position is that you have no idea about the specs of the fans in the amps and the fans replacing them."
My point was that you should pay attention to CFM, not RPM. Because, whether you realize it or not, CFM can vary widely within the same RPM range. To wide to not worry about it.
As an example, two random fans i picked out:
http://www.newegg.com/Product/Produc...82E16835220024

size: 80mm
RPM: 1600
CFM: 31.52 CFM

http://www.newegg.com/Product/Produc...82E16835226001

size: 80mm
RPM: 1600
CFM: 18 CFM

However, i will admit, the a difference may not be noticed, as it depends on how hard you run the amp and the environment its in. I never stated it was a bad idea to replace the fans with quieter ones, only to match them with equal CFM ratings. If you do that there are no down sides, if you don't, you may be creating some.
But as with all things, its your equipment and your decision. If its your choice i'm not going to argue against it, i just want to make sure you're aware.

And how much would you like to bet that those fans do not meet those ratings?

Better yet, do you know how they were measured?
post #1482 of 1917
Quote:
Originally Posted by matt5112 View Post

And how much would you like to bet that those fans do not meet those ratings?

Better yet, do you know how they were measured?

I am sure they don't meet their ratings, they are usually exageratted. Though i am not sure what your point is, that just means we can't fully trust their CFM ratings. But it is all we have, unless we find a 3rd party measurement or do it ourselves
post #1483 of 1917
Quote:
Originally Posted by jarrod1937 View Post

I am sure they don't meet their ratings, they are usually exageratted. Though i am not sure what your point is, that just means we can't fully trust their CFM ratings. But it is all we have, unless we find a 3rd party measurement or do it ourselves

If you need help finding one let me know.
post #1484 of 1917
(Emphasis added)
Quote:
Originally Posted by jarrod1937 View Post

The point of those fans are not always to keep the amp from shutting down. But rather to keep components cool for the best sound. Electrical components resistance changes with heat, the more heat, the more resistance. You may not get a protective shutdown but you're probably raising distortion figures.

If anything, i'd add more fans. You can then lower the noise while getting the same, or more CFM.

I think that is an extreme position for a amp used for a subwoofer in a home environment. It is likely an opinion held by few experienced people.

But hey, whatever floats your boat.

This is a silly back-and-forth discussion which reminds my why I stopped posting here.
post #1485 of 1917
Quote:
Originally Posted by ---k--- View Post

(Emphasis added)

I think that is an extreme position for a amp used for a subwoofer in a home environment. It is likely an opinion held by few experienced people.

But hey, whatever floats your boat.

This is a silly back-and-forth discussion which reminds my why I stopped posting here.

I only offered that as a suggestion to those who felt those two things were important (same cooling while offering less noise), so i see no need for it to be held as an "extreme" position. If you don't find both of those as being important, then simply just ignore the suggestion. Not like it was a command or anything

"This is a silly back-and-forth discussion which reminds my why I stopped posting here."
Its a forum, what do you expect? A monologue?
post #1486 of 1917
My 2000 W/ch Peavey amp fans are variable speed and I have to put my ear up to the front (where air is drawn in) to hear them.
post #1487 of 1917
Quote:
Originally Posted by whoaru99 View Post

In another room with the stock fans would be the best option, I agree.

Is that the PL 9.0, or something else?

Yep that's a niner. It seems to be quieter than a CE4000. Not super quiet but not bad considering it has 4 fans and the Crown only has 1 big one.
post #1488 of 1917
Quote:
Originally Posted by thylantyr View Post

That load isn't good for testing kilowatt amplifiers.
There is a reason why too.

Each resistor is 1.75 inch by 3.5 inch in its own heatsink.. this individual resistor/heatsink bolted to a 3 foot car audio heatsink extrusion with 7 other resistors. resistor measured after 2 ohm test witch didn't last long because of dual 20 amp breakers on back of amp.... 8 resistors series parrallel on each channel didn't warm up much due to breakers. Amp has dual mono power supplies so one channel tested at a time. I have 56 resistors available should I want to bypass those breakers. I have one rmx 5050 on my back system with 8 older cerwin vega le/xl 15 inch woofers in 4.5 cubic feet per woofer. The amp can easily overdrive all of these speakers at once, but the surprise was the detail and ability to hear multiple instruments/sound sources in the music is much improved over the outgoing adcom 565 mono amp that had let out its magic genie a month ago. The adcom had won simple listening tests with parasound 2002 and 3500 and rotel 1090's and an old crown psa2. I expected the 5050 to be just louder, but it is has proven to be much better much more control over the speaker.. The other 5050 will find it's way to my front system when I get the time to tear it down... Possibly driving 4 orion HCCA 15's. The Front system already has 2 previously installed 5050's driving 8 buttkickers
post #1489 of 1917
When do we get to see some more amps tested? I have been enjoying seeing the numbers put up by some of the amps in this thread and the controversy thereafter.
post #1490 of 1917
We should get the EP4000 tested so we stop all the silly conclusions!
post #1491 of 1917
Quote:
Originally Posted by penngray View Post

We should get the EP4000 tested so we stop all the silly conclusions!

There is nothing silly about math and electronics
post #1492 of 1917
Quote:


We should get the EP4000 tested so we stop all the silly conclusions!

yep!

Quote:


There is nothing silly about math and electronics

yep! x2
post #1493 of 1917
Nice setup.
I would however, liked to see DF at 20, 50 and 100 Hz. I am into low distortion, not loud.
What I don't know how to measure is recovery time. How does an amp handle big pulses one after another? A lot of the new amps have very small caps. My experience by ear is "not very well". Maybe the low Z of the toroid transformers is compensating. In the old days, if you wanted "punch" you needed 250,000uF per 100W or so.
post #1494 of 1917
Quote:
Originally Posted by tvrgeek View Post

In the old days, if you wanted "punch" you needed 250,000uF per 100W or so.

Do you have some examples of amps with 250,000uF per 100W, or more?

That seems like quite a high number to me.
post #1495 of 1917
That would appear as a dead short initially. I would think you would have to have one heck of a transformer at that point also.. Especially if you are talking an amp with a few hundred watts!
post #1496 of 1917
I added 2 F at 56V to an amp I had. It was a CM Labs. Probably before your time. Yes, you had to charge the caps through 60W light bulbs with a bypass relay. Only 100W x 2 driving a pair of 12"s in a really big box, but what transients! The box with the caps was 5U, and another 3U box for the bulbs and relays. In those days, the Dyna 400 and Ampzilla were the monsters. It would produce odd noises out of the speakers for about a day and a half after turning it off until I added a circuit to discharge the caps back through the bulbs.
post #1497 of 1917
Quote:
Originally Posted by tvrgeek View Post

In the old days, if you wanted "punch" you needed 250,000uF per 100W or so.

LOL, that WAS the OLD DAYS! There's been an awful lot of materials and technology gone under the bridge since those days.

You want PUNCH . . . . get a PRO amp (I Tech 8000) and hook it up to ANY driver in a box and look out!
The caps in ALL of todays amps PRO or otherwise have "small" caps. Caps technology has changed along with the materials used inside em.

Check out a POWERSOFT AMP. Try counting the
caps.
post #1498 of 1917
Yep and today 1U or 2U amp will blow out of the water that amp and no pain in the butt thing to do to power it up thank you god for soft start all this in a 12 lbs package.


Quote:
Originally Posted by tvrgeek View Post

I added 2 F at 56V to an amp I had. It was a CM Labs. Probably before your time. Yes, you had to charge the caps through 60W light bulbs with a bypass relay. Only 100W x 2 driving a pair of 12"s in a really big box, but what transients! The box with the caps was 5U, and another 3U box for the bulbs and relays. In those days, the Dyna 400 and Ampzilla were the monsters. It would produce odd noises out of the speakers for about a day and a half after turning it off until I added a circuit to discharge the caps back through the bulbs.
post #1499 of 1917
some interesting info from powersoft faq:

1. About power measurements of digital audio amplifiers As explained in the DIGAM Series data sheets , one of the main advantages of Digital Audio Amplifiers is the possibility to handle in a considerately more efficient way the musical power with respect to conventional linear amplifiers, taking in to account that music average power energy is considerably lower with respect to continuous sine wave signals of the same peak level.

In few words the main advantage of Digital Audio Amplifiers is to underperform the continuous signal power output (unusefull from the musical point of view) in order to strongly protect the loudspeakers loads and greatly enhance power output of the useful
musical signals. To this regard, in order to have more clear picture about the scientific approach, please make also reference to the enclosed document "Design Criteria for an innovative professional high power audio amplifier".

Therefore the Audio Power outputs stated in Digam Series Catalog must be measured in the following conditions:
1. Power RMS x Channel (1kHz, 0.5%THD):
• Maximum continuous output power delivered to the load for at least 5 seconds, then internal limiting processor reduces output
voltage swing to _ maximum output.
2. Power RMS x Channel in stereo working:
• Maximum EIAJ standard test output power: average of RMS output voltage squared divided by load impedance.
• Test signal 1kHz tone burst 8 cycles 0dB, 24 cycles no signal, THD 1%.

If the power measurements will follow the above conditions there will be founded the power figures very close to those stated in the data sheets.
In the case that measurement are done with the non significant method of continuous sine wave input signals (applied for more than 5 seconds), the system is self-protected from that unusefull signals, and lower output values will be found.



2. Design criteria for DIGAM, the Powersoft innovative digital professional high power audio amplifier It is well known that the qualitative analysis of audio spectrum characteristics for different typologies of music is showing the presence of sequence of short burst with different peak power values and duration.

Taking in account these peculiar spectrum characteristics it is possible to introduce a new approach in designing Audio Amplifiers, especially when a very high audio output power is required. In effect in the normal operation the amplifier's useful output music usually is limited by its short term power capabilities and not by the heating that results from high continuous power emission.Based o the above consideration, our assumption was that it is possible to minimize the non realistic usual requirement for
continuous power rating, typical of conventional analogue amplifiers, and to design much more efficient Audio Amplifiers increasing their burst power capability with respect to the continuous power rating.

For the correct design it is moreover necessary to define as valid for any typologies of music two basic parameters as: the ratio for the peak output power to continuous power rating and the max. burst duration.
About the first parameter from specific research and analysis performed by DeMarinis (1) it results that in the worst case of rock music compressed for FM broadcast the ratio of r.m.s to peak power is around 8 dB. This means that if an amplifiers volume
control is set to place the high peaks at the on set of clipping, the most severe continuous power demand is less than 15% (usually under 10% ) of the amplifier's max. peak power.

About the second parameter - max. burst duration - other studies and tests as been performed (2),(3), in the past and specific confirmations as been obtained in the Powersoft Co. Laboratory, confirming that for all the music types the burst peak power Is always reducing with the increasing of the duration of the bursts.
This general rule is represented by the following expression, and takes in to account all possible music worst cases:
10 log p/pc =-0.16 Log t
were 't' is the toneburst in milliseconds and ' pc' is the power level at 0 dB (the clipping point)
This means that the distribution of peak power bursts in function of duration can be represented in the following table:
• burst duration max r.m.s level
• 1 ms 0 dB clipping
• 10 ms -2 dB
• 100 ms -3 dB
• 1 sec. -5 dB
• 10 sec. -7dB

Based on the above results Powersoft has been in the position to define the basic requirements to design of an innovative very efficient Audio Professional high power amplifier:
• To obtain extended duration of headroom, able to delivery burst of 1 sec. or longer at substantially higher level then normal linear
amplifiers 'continuous power rating.
• To obtain an optimized thermal design suitable to manage very high r.m.s output power within 3 dB with respect to the peak power.
This requirement will allows a margin with respect of to above mentioned experimental results.
• To obtain an automated gain control suitable to maintain for any input signal level the full dynamic capability. This requirement in
order to avoid clipping distortion and ensure the nominal r.m.s power.
Moreover it was recognized necessary also to have a very high efficiency power supply system together with a power factor corrector to keep the system independent from variations of mains and to be also in full compliance with the new European regulations.
The right solution to the above requirements was founded utilizing digital switching technologies (based on the principle of PWM modulation ) with some patented circuitry topologies solutions.
In effect this PWM technology, through a very high frequency sampling of audio input signal (over 250 kHz) allows with the necessary accuracy to process the signal in digital form and provides the highest power outputs with extreme efficiency (near to 95 %).
A patented output filtering and processing solution provides output capabilities at the highest level of quality in terms of low distortion, noise and bandwidth .
Based on the above, Powersoft has developed a new generation of digital audio amplifiers branded DIGAM.
DIGAM series of Professional Audio Amplifiers is a complete range of products from 2000 W to 9000 W on 2 ohms load in 1 unit 19"
rack size and 9.5 Kg weight.
Other main features of DIGAM series are PFC (power factor correction); overheating power control and significant options in
professional applications as multiple remote control and pre-processing signal.
The global audio result of such new generation of Audio Amplifiers is that with such innovative design criteria it was obtained a very
cost-effective product with the best adherence to the real music professional requirements.

References
• J.V. De Marinis: "How valid is the FTC Preconditioning Rule? " - Audio Sept 75.
• P.J. Mitchell: "A musically Appropriate Dynamic Headroom Test for Power Amplifiers. "A.E.S. Pre-print 2504, Oct. 87.
• A.E.S. Convention 7/10 Oct. 93 - Pre-print: "The Dynamics of Recorded Music". Presented by J.A. Mc. Manus, Chris Evans and
P. J. Mitchell.

http://pro-audio.powersoft.it/faq_li...menu=325&obj=3
post #1500 of 1917
All major amp designers including Powersoft have at one time or another attempted to explain why their particular amp can or cannot supply the high watt figures continuously. The 4000, 5000, 8000, and 9000, watt output figures are short duration numbers and many times will be specified at only certain frequencies (1KHZ). But the AMPS many times DO what they advertise but only under manufacturers lab conditions.
Chasw98 opened this thread with his amp testing methodology and specialized equipment. The tests he's performed have been extremely useful and have been responsible for creating reams of discussion and have opened eyes as to amp performance. It's really been good stuff.
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