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Author Topic: Amp Review  (Read 18280 times)

Langston Holland

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Amp Review
« on: November 13, 2010, 04:15:20 pm »

Purpose:

My recent upgrade to the Danley TH118 subs has motivated me to look into larger amplifiers than the PL380 that has been perfect for the TH115's. I've also been underpowering the low passband of my KF730 boxes on the order of 3dB. I've justified this mentally because the low passband only covers 90Hz to 200Hz and the fact that I overlap the early part of this spectrum with subs. Now I'm going to drive those hungry 10" drivers to their limits. The KF730's are 16Ω boxes and the series pair of woofers is rated for 700 watts continuous, thus 1,400 watts "program" per box. A daisy chain of (4) to (6) of those boxes demands an amp that effectively didn't exist when the KF730 first came out. That, boys and girls, is not the case anymore.

The net result of the amp upgrade will be approx. 3dB more output from the same loudspeaker arrays from 200Hz downward. Same truck pack, same weight, same size, but more rig for the gigs. Just need to pony up around $10k (assuming sales of my existing amps) and I’m in. Is 3dB under 200Hz worth 10 grand for my (24) KF730’s and (8) TH118’s? Heck yes.

The higher frequencies are powered to their program ratings already with an amp that I've yet to find an equal to sonically. On that note, I’m going to add a fair amount of subjective commentary in this review that I used to shy from. I’m over it. Class D and the variants I’ve heard are not ready for critical HF reproduction yet. There, I said it - and it’s a fact unless you’re deaf, don’t care, think MP3 is good, or are trying to earn a living in this business. :)

Measurement Setup:

Room temperature 20C, voltages at the input and output of the amps were monitored with a Fluke 192C Scopemeter that has fully isolated inputs. Sine waves in various flavors were used for all tests. Long-term tests were done with 500ms on / 500ms off steps with distortion curves monitored via the amazing STEPS module in the ARTA measurement suite. Benchmark DAC1 and ADC1 converters with instrument grade +30dBu I/O capacity were optically connected to my MacBook Pro running XP in Bootcamp. A 21dB pad was used to feed the input of the ADC1 for a 51dBu maximum input capability. At the 4Ω resistive loads I placed on both channels of each amp in the test, this allows a maximum level of 18,904 watts to be measured cleanly. My new SuperBucket™ was used to take the heat. This thing presents (2) 4Ω loads with 14,400 watts long-term dissipation and peaks numerically similar to the national debt. You can also use banana plug jumpers to configure single 8Ω and 2Ω loads at double the wattage, assuming the jumpers survive.

SuperBucket

http://homepage.mac.com/soundscapes/PSW/AmpTests/SuperBucket.jpg


Measurement Theory:

Everybody and their mother have different ideas about how to best measure the performance of an amplifier. Some folks think the old fashioned way of feeding continuous sines is the deal because they apparently use their amps to arc weld during the middle of the week. On the plus side, you’ll get absolutely comparable results from every manufacturer, on the down side those results are not very meaningful for our application. My use of 500ms on / 500ms off sine steps yield effectively identical results as continuous sines in my experience and this is included. Since I use amps for powering loudspeakers with music, I prefer using shorter lengths of sines that approximate musical behavior as much as possible so I can have more meaningful metrics for the intended application. That's where the rub is – just what kind of stimulus comprises the most meaningful metric? For some reason folks keep looking for a _single_ metric to describe amp power, but I think that's a recipe for failure. In our application there is a long-term load as well as much, much higher momentary peaks that need to pass cleanly up to the point where the loudspeaker system begins to sound bad or fails. Those two thresholds are separated by about 6dB of voltage and 20dB of attitude. I've included both long-term and short-term tests in a way that makes the most sense to me. As of today. And it’s my party so I can do what I want. :) I’d love contrasting views as always.

Take a trip around the block and you'll notice that Lab Gruppen and Yamaha/NEXO, to name two, are measuring their amps in ways that attempt to account for the behavior of music as opposed to the behavior of welding machines. Both use sines to allow distortion measurement, which is critical. Lab uses a 33ms on / 66ms off step which seems quite reasonable as a single metric, especially at lower and mid frequencies. It might be a little severe (long) for the higher frequencies, but it keeps things consistent, repeatable and logical. Yamaha/NEXO uses a 20ms on / 500ms off step and only measures the last sine wave in the 20ms burst, and that at 1kHz apparently. This probably yields higher power ratings than reasonable and certainly shouldn’t be the only metric considered.

There's a guy named Don Keele that I've been following since the 80's that has contributed much to the loudspeaker industry, and by extension, the amplifiers that power them. The logic behind his attempts to measure both gizmos in a way that simulates actual usage makes sense to me and correlates with my testing and listening efforts, particularly as applied to limiter settings. As a side point, I think advanced limiter topologies that simultaneously deal with long-term heating and peak mechanical issues of loudspeakers in a sonically pleasing way are the next area of serious improvement in the quest for high SPL and good sound. Driver design will need to go hand-in-hand with this. NEXO is a forerunner here.

So what about Keele's short-term tests? Read Shaped Tone Bursts beginning on pg. 6. The earlier pages are an important intro.

Want his stimuli and have time to wait for 300MB? Click here if you dare. I neutralized a very expensive amplifier that was supposed to go to a little outfit that rhymes with “hair” after I was done with it. I wasn't careful enough with the 20Hz tone burst. Whoops.

Bottom line from Keele? From a post he made last November on the SAC list: "What we need is that 100 Watt continuous power amp that can pass 10 kW peaks for short periods of time."

I've had to chew on this concept for years to appreciate it, but I'm convinced he's right and my tests show more than a few amp manufacturers are convinced as well and are building amps accordingly. According to the needs of music instead of welding, imagine that.

The Players:

Camco Vortex 6

Alluded to earlier, this is simply the best sounding professional amplifier I've ever heard. It's a class H design and somehow manages to reveal the most subtle details in high-end recordings with earphone clarity over (excellent) loudspeakers. To date I've yet to hear a class D variant (including the following amps) that can present the width and depth of a recording anywhere near as well. I have no idea why this is the case - no measurements I've ever made are conclusive. The flatter transfer function certainly doesn't hurt, but it's more than that. Full output at 120v 30 amps works perfectly, no need for the 208/240v model unless it’s more convenient for where you live.

QSC PL380

One of the best bang for the buck ratios on the planet. My (9) PL380's have been rock solid for several years. They are also one of the better sounding class D amps if you have to use one in the mid/high region. Like the Camco, full output at 120v 30 amps works perfectly, no need for the 208/240v model.

Powersoft K10

Oh my - this beast is ready for your welding rods and sine waves masquerading as music. One rack space of pure attitude - it's squirrel fans will go into overdrive if necessary, much like the old Crest 9001's, but this amp will just keep belting out continuous power unlike any amp I've ever come across. It also is solid on the Keele short-term tests. The amp is very well designed and feels as solid as it runs. Very logical layout and very efficient with power, will accept any voltage on earth and do sine waves all night long (trance, electronica, whatever). Optional DSP card available with FIR filtering, but not on the order of either the Crown HD or Lab PLM series. Quite good nevertheless - you can download the software for your PC and see if it fits your needs. Sound is much better than average for class D - about equal with the PL380, though a more forward sounding midrange. You obviously want 208/240v with this amp if you're going to use its full capacity.

Crown IT5000HD, IT9000HD and IT12000HD

The processing in these things simply rocks. Very steep and well-designed FIR filters, plenty of all-pass and parametric EQ filters. Nice average and peak limiter facilities. The software interface to the ITech amps is probably the best I've ever seen, Crown works very hard at this and releases updates frequently. I noticed earlier this year that the 2nd order all-pass filters weren't working and Crown had it fixed in less than a week - wow. It also made me wonder why I was the first to notice this since they’ve been out for a while... The software makes for very nice multiple amp management in larger company or install environments. The sound is greatly improved from my previous experience with the non-HD models. My guess is that it's due to the processing upgrade since the amps measure fairly similarly. I prefer the sound of the other amps in this test in the mid/highs when ignoring the processing, but you shouldn’t do that. I designed FIR filtered, flat-phase presets for Troy’s KF730’s to mimic what I’ve done with the Dolby Lake processor and was amazed at how good the net result was. The limiters sounded good too. I noticed a similar result when doing listening tests with the Lab PLM20000Q with internal processing vs. the FP14000 fed by a DLP. Interesting. Reliability reports are good with the HD series. The ITech's have always been good at making power and these amps are no exception, but it’s silly that they increased the numbers in their model numbers – output has not increased as far as I can tell. Though I don't report it here, short-term output into 2Ω’s will surprise you with either the older or newer ITech’s. You think this is a 4Ω only amp? Nope. It shows a similar increase in output into 2Ω’s that you see in typical amps as long as you don't ask it to do so for un-musically long periods of time. Still, voltage is king and is what SPL is made out of and you should stick to a nominal 4Ω’s regardless of amp IMO. The ITech’s play nicely with others due to worldwide voltage and PFC.

If you push these amps to their limits, you're going to want to feed the 9000 and 12000 with 208/240v. At 120v even at 30 amps, both these amps "groan" when under load. That kind of vibration can't be good in the long run. At the 240v feed they got during my measurements, they were nearly silent other than fan noise, which can get up into the Crest 9001 range. The 5000 is happy with 120v 30 amps into anything that will ever happen in practice, though it did want 240v for continuous sine testing.

Lab Gruppen FP14000

I'm buying (4) of these as a result of these tests. Their output to size, weight, sonics, warranty and cost is a winner. These amps are not auto-ranging, you have to choose either 120v or 208/240v - the latter is the only thing that makes sense given the horsepower involved. This amp is all about allowing the peaks of music to get through without clipping as their testing method indicates. It has both hard (lows and subs) and soft (mids and highs) limiting available as well as several cool protection circuits with a light show on the front panel. I made all the pretty lights come on without letting the smoke out. Too bad they make you buy a thousand dollar gizmo to connect your PC to the amp to monitor its behavior - they should nix that thing and its cost and allow you to connect your computer directly to the amp(s). Maybe the smaller Labs sound better in the mid/highs, but this amp showed its class D heritage in my listening tests, which nixed my thought of replacing the Camco's with a Lab on the mid/highs. Still, this amp is probably the best sounding class D amp I've heard.

Long-term Measurements:

Though I expected this to be boring, I accidentally learned some interesting stuff here about design philosophy between the various manufacturers. All have made reasonable compromises in trying to skin the cat of high output without damaging itself or the stuff at the other end of the loudspeaker cable when operated by a bunch of lunatics.

Each of the below show a reference measurement of magnitude and phase at 50 watts and at about 1dB beyond their maximum output capability with both channels driven into 4Ω. Do not freak out about the max power traces, I could have backed off a hair and made them all pretty, but that wouldn’t have been very helpful, would it? Plus I would have missed out on the flames from some of the manufacturers – and what fun would that be? Actually, I learn from those as well and look forward to it. Be sure to read the caption at the bottom of each graphic for details.

Camco Vortex 6 (low level and 1dB beyond max)

http://homepage.mac.com/soundscapes/PSW/AmpTests/STEPS_V6.PNG

QSC PL380 (low level and 1dB beyond max)

http://homepage.mac.com/soundscapes/PSW/AmpTests/STEPS_PL380.PNG

Powersoft K10 (low level and max)

http://homepage.mac.com/soundscapes/PSW/AmpTests/STEPS_K10.PNG

Lab Gruppen FP14000 (low level and 1dB beyond max)

http://homepage.mac.com/soundscapes/PSW/AmpTests/STEPS_FP14000.PNG

Crown ITech HD (low level)

http://homepage.mac.com/soundscapes/PSW/AmpTests/STEPS_ITech.PNG

Crown ITech HD (1dB beyond max)

http://homepage.mac.com/soundscapes/PSW/AmpTests/STEPS_ITech_Max_+1dB.PNG

Short-term Measurements:

This is really interesting.

The following scope traces are from the FP14000 to demonstrate how I made these measurements. The scope is used to determine the point at which the shaped tone burst begins to deform and plotted with the input signal scaled to for reference. The red trace is the input signal and the blue trace is the output at the point where I judged it to be the maximum. I lost the 100Hz measurement like a dummy, and I’m too lazy to do the measurement again, but it’s immaterial. One thing you’ll notice is at the higher frequencies, the output trace is late to the party – a simple measurement of phase lag as predicted by the long-term STEPS trace. The scope's phase calculations agreed with STEPS. I think I’m getting the hang of this. :)

FP14000 Shaped Tone Burst Measurements

http://homepage.mac.com/soundscapes/PSW/AmpTests/FP14000_Scope.png


And now, ladies and gents… These numbers are per channel in stereo mode into 4Ω. They would have been higher at 2Ω, though voltage and the SPL from your loudspeakers would be lower. Chew on that. I hate this whole watts thing – just did it for the peanut gallery – next time it’s volts like God intended. :)

The Data

http://homepage.mac.com/soundscapes/PSW/AmpTests/Amp_Burst_Table.png


The Picture

http://homepage.mac.com/soundscapes/PSW/AmpTests/Amp_Burst_Graph.png

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Soundscapes <><

Phillip_Graham

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Re: Amp Review
« Reply #1 on: November 13, 2010, 04:38:30 pm »

A single post that is more useful than a year of issues from any of the trade rags, Production Partner excepted.
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Tom Danley

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Re: Amp Review
« Reply #2 on: November 13, 2010, 05:19:31 pm »

Wow, Langston you have been busy!  
Very nice work and it will take a good while before you will have to worry about melting your Abdul-EQ superbucket too.
Again, Nice work!
Best
Tom Danley
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Ivan Beaver

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Re: Amp Review
« Reply #3 on: November 13, 2010, 08:38:26 pm »

It's great that you took the time and put in the effort to really look at how different products perform-and use those results for products that best meet your needs.

Those types of test can yield very interesting results.  

And give good insight into a lot more about the performance of a product than a simple spec sheet would provide.

And another example of why it is hard to describe the complicated performance of an audio product with a couple of "simple" numbers.

For those looking for more specific details about how a product performs-you often have to look a bit deeper.  And it is always a good idea to perform the exact same tests on different products and chart the results to see "trends".

Good work and an interesting read.

Thanks for the review(s).

One thing I would like to see that you didn't post-was how well the amps did producing a sine wave for an "extended" period of time.  Say 1 or 2 seconds.

Yes regular "music" doesn't have usually have durations that long, but electronic music often does, and at very low freq.

It would be interesting to see how things would change (if they did) with that type of test.
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Franz Francis

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Re: Amp Review
« Reply #4 on: November 15, 2010, 08:12:48 am »

+ 1 on the Camco V6. This amplifier seem to have the characteristics of the audiophile types.

Franz  
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Phillip_Graham

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Re: Amp Review
« Reply #5 on: November 16, 2010, 09:27:06 am »

Ivan Beaver wrote on Sat, 13 November 2010 20:38


One thing I would like to see that you didn't post-was how well the amps did producing a sine wave for an "extended" period of time.  Say 1 or 2 seconds.

Yes regular "music" doesn't have usually have durations that long, but electronic music often does, and at very low freq.



Ivan, if you read more carefully, I think you will find that Langston states clearly that the Powersoft amp performed the best for continuous sine wave output.

Langston wrote about the Powersoft K10


Oh my - this beast is ready for your welding rods and sine waves masquerading as music. One rack space of pure attitude - it's squirrel fans will go into overdrive if necessary, much like the old Crest 9001's, but this amp will just keep belting out continuous power unlike any amp I've ever come across. It also is solid on the Keele short-term tests.


I personally see little point in the extended sine wave tests, unless you were working in a very specific area of music, but your suggestion of a 1 second sine wave test seems reasonable.
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John Roberts {JR}

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Re: Amp Review
« Reply #6 on: November 16, 2010, 10:00:21 am »

Phillip Graham wrote on Tue, 16 November 2010 08:27



I personally see little point in the extended sine wave tests, unless you were working in a very specific area of music, but your suggestion of a 1 second sine wave test seems reasonable.


The problem remains that we can not say what is the appropriate test stimulus for everybody.  We were doing dynamic or transient headroom tests several decades ago on the hifi side.

I make this suggestion from time to time and the technology is slowly catching up to make this viable.

How about digital recordings of the actual sends to your power amps in use while doing actual gigs. Ideally, one track for each amp bandpass. These glorified board tapes could be definitive amp tests for each customer.

Since the digital files should be accurate and repeatable, you should be able capture a track from the output of the amplifier under test, tweak it for level and delay, then see how well it nulls with the input. Over time multiple people doing this could identify a handful of board tapes that different amps have difficulty with.

For a happy ending to this story, we could email these sound files to the manufacturers and they could fix their amps, or explain why they choose not to support that test tape.

This investigation may help us identify simpler test signals that reveal the amplifiers weak links,  or not..  While artificial test signals are hopefully representative, it is always an educated guess.

JR

PS: You could do this null in real time, but many amps already do..... look for a flashing red LED.  Cool
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Art Welter

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Re: Amp Review
« Reply #7 on: November 16, 2010, 12:22:15 pm »

Langston,

Nice testing !

Did you do a musical (or test tone)test to see if the additional 3 dB of headroom the FP14000 has over the PL380 actually translated into 3 dB more speaker output, and if so, what the extra headroom did to the speaker distortion levels on the 18” and 10” drivers?

Art Welter
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Josh Ricci

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Re: Amp Review
« Reply #8 on: November 16, 2010, 03:03:35 pm »

Awesome data. Thank you for the effort to collect and post it publicly. Bookmarked.
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Jeff Babcock

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Re: Amp Review
« Reply #9 on: November 16, 2010, 04:26:23 pm »

Phillip Graham wrote on Sat, 13 November 2010 16:38

A single post that is more useful than a year of issues from any of the trade rags, Production Partner excepted.


+1

Great stuff Lang!

Eytan Gidron

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Re: Amp Review
« Reply #10 on: November 20, 2010, 10:06:34 am »

Langston Holland wrote on Sat, 13 November 2010 23:15

:Optional DSP card available with FIR filtering, but not on the order of either the Crown HD or Lab PLM series.



Thanks Langston for this great review. What did you actually mean in this comment of the K10 DSP?
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Langston Holland

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Re: Amp Review
« Reply #11 on: November 20, 2010, 03:35:54 pm »

Eytan wrote on the 20th:

Langston wrote on the 13th:

Optional DSP card available with FIR filtering, but not on the order of either the Crown HD or Lab PLM series.


Thanks Langston for this great review. What did you actually mean in this comment of the K10 DSP?


Good question - I gave no clues other than the non-trival pursuit of downloading the Powersoft software to have a go at it. You'd have to download, install and learn the control software for the other amps as well to make a full comparison. It has become popular with many of these processor mfg.'s to skip the detailed manuals and make you go fishing instead. :(

The built-in processing in the ITech HD and (to an even greater extent) the PLM amps have far more filter selections in type and quantity. Though the optional processing card for the K10 has less power, it can do as good a job in many cases. The Powersoft FIR filtering has a minimum useful frequency around 1kHz, under which the slope attenuation per octave is too shallow and standard IIR filters should probably be used. This is due to a lower maximum number of FIR coefficients allowed. Then again, the Powersoft processor allows direct import of FIR coefficients, which engineers can design very application specific filters with. I've heard that if you know the right people at Crown you can do the same with the ITech HD. This didn't used to be possible with the Lake processing, but with EAW's announcement that the PLM's would support focusing, that may have changed.

The Powersoft engineers obviously feel that there isn't enough of an audible advantage using high slope linear phase filters apart from the mid to high crossover point. One advantage of this is that you incur less of a latency hit with this approach vs. using high slope FIR filters at the low to mid crossover region. For sound reinforcement work where delaying the PA 10 or 15 msec is usually helpful, the ideal hybrid crossover IMO is IIR between subs and lows with high slope linear phase FIR above that.

One more thing - a nicely written Powersoft K10 Review from 2005.
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Franz Francis

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Re: Amp Review
« Reply #12 on: November 20, 2010, 06:42:48 pm »

I forgot to ask, have you auditioned the new Camco vertec 8 silver series, it is suppose to be their answer in the four thousand (4000) watts per channel professional amplifier competition.
Just wondering if the sonic signature of the Vortex 6 is consistent with the entire Camco line or is it just related to the Vortex 6.
Based on the info on their website the Class H output stage is still present with the Vortec 8 Silver. No class D compromises there.

Franz
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Iain_Macdonald

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Re: Amp Review
« Reply #13 on: November 21, 2010, 11:00:38 am »

Hi,

Well all good things come to those who wait!  Rolling Eyes Have a look at this thread and Binks answer further down the page. Maybe now we can move towards getting some meaningful results from all the (often wasted) time and effort spent on speaker, and electronics testing. Though they did seem to be good social occasions.

I agree with Ivan, that there is a still a need for continuous sine wave testing for pro products. Why? In HOW situations the organ/synth is often connected to the PA system, and some of those synth notes are very nearly sine waves. Also some of the 80's bands, and some of the newer indie bands are using bass pedals and lots of continuous low frequency synth notes. In the rave/club world, some genres have sine waves/sweeps added to the original mix.

So class D is not good enough  Shocked Handbags at dawn!

Iain.

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Iain_Macdonald

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Re: Amp Review
« Reply #14 on: November 21, 2010, 11:27:48 am »

Langston wrote

The net result of the amp upgrade will be approx. 3dB more output from the same loudspeaker arrays from 200Hz downward. Same truck pack, same weight, same size, but more rig for the gigs. Just need to pony up around $10k (assuming sales of my existing amps) and I’m in. Is 3dB under 200Hz worth 10 grand for my (24) KF730’s and (Cool TH118’s? Heck yes.


Surely 3db peak output.  Sad

Lanston also wrote

As a side point, I think advanced limiter topologies that simultaneously deal with long-term heating and peak mechanical issues of loudspeakers in a sonically pleasing way are the next area of serious improvement in the quest for high SPL and good sound. Driver design will need to go hand-in-hand with this. NEXO is a forerunner here.


Analogue modeling was used by a number of manufacturers before Nexo's controller - EV Meyer R-H SA etc.

Langston wrote regarding PowerSoft

Optional DSP card available with FIR filtering, but not on the order of either the Crown HD or Lab PLM series


Powersoft do a number of DSP cards for their badged and co-branded models. Some of these have considerably more dsp power than the standard version.

Nice report Langston. Thanks very much for your efforts.

Iain.
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Jeff Wheeler

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Re: Amp Review
« Reply #15 on: November 21, 2010, 04:28:04 pm »

Langston Holland wrote on Sat, 20 November 2010 14:35

One advantage of this is that you incur less of a latency hit with this approach vs. using high slope FIR filters at the low to mid crossover region.

My understanding is that FIR delay is a function of sample rate and number of taps, and that you can basically throw CPU power at the filter to reduce delay while also making the filter more precise.  I could be remembering this incorrectly, though; my notes on this topic are trapped on a PC with a busted mainboard. Sad
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Langston Holland

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Re: Amp Review
« Reply #16 on: November 22, 2010, 12:28:45 pm »

Hi Iain:

Thanks for the link to that 2007 post of yours - don't know how I missed it before - I'd probably been further down the road by now if I'd seen it. :) Might have just been due to how long that thread got at the time...

On that 3dB peak observation, that is true and what you'd expect from the measurements. The fact is that the long-term output increases by about this much as well with a hang of 6 boxes per amp channel (worst case in my rigs). The subjective difference is huge with larger arrays. Maybe I'll figure out a way to measure that someday that reduces the subjective (fun) component.

Since maximum output is tied to limiter settings, it would probably be helpful to describe my approach:

1. Start with the mfg. recommendations.

2. Adjust short-term limiting so that woofer slap is avoided using typical pink noise (12dB crest factor) and Keele's tone bursts through the passband. In the case of the KF730 low passband, I do this using the minimum number of boxes I'd ever use per amp channel (3), so I have the maximum voltage delivered to the boxes that they would ever see in actual use from that amp.

3. Adjust long-term limiting by ear using the now world famous "maximum musical output" test per a condensation of Tom Danley's life-long research into the deep realms of psychoacoustics (aka common sense).

The best objective long-term power test procedure IMO is Pat Brown's "Toaster Test". So far, I'm the only one in my neighborhood that's done it and it works. Yet if you set your long-term limiters by it you'll find the LF passband to be driven at least 3dB hotter than you'd like to listen to it with music, thus the TDMMO test always results in more conservative power limiting. It would be just as valid to use the toaster test for the HF passbands but I don't bother. The ear is obviously far more sensitive to distortions in this area and I fully subscribe to starting with the mfg's recommendation and them applying the "Ugh! Turn it down!" method for the final settings.

A final note - all of this is processor dependent. I'm into the Lake processors at present which have unusual limiter settings. Given the variation I've seen with something as simple as "Q" with parametric EQ between different mfg's processors, I'd expect standard limiter adjustments for "Attack", "Release", etc. to vary as well. Bottom line: measure everything that moves, if it stops moving, fix it and measure it again.

A final, final note - this all assumes you have two adjustable limiters on the processor output for the passband. The Lake processors including those internal to the Lab PLM amps, ITechs and optional Powersoft DSP have separate "RMS" and "Peak" limiters. You could also use the adjustable maximum voltage limiter on non-DSP amps such as the Lab FP+ series combined with a single compressor/limiter you find on a typical loudspeaker processor output. The coolest thing would be designing your own using a free wire processor per Charlie Hughes' article. Don't have time to experiment with that yet - wish I didn't have to sleep. :)
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God bless you and your precious family - Langston

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Bob Lee (QSC)

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Re: Amp Review
« Reply #17 on: November 22, 2010, 04:35:31 pm »

John Roberts  {JR} wrote on Tue, 16 November 2010 07:00

PS: You could do this null in real time, but many amps already do..... look for a flashing red LED.  Cool


Wink Thank you for that!
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Bob Lee
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Jason Joseph

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Re: Amp Review
« Reply #18 on: December 22, 2010, 08:36:47 am »

Interesting read so is it safe to say that compared to the bigger boys the Camco Vortex 6 is better used for high/mid duty than for subs..?
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