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[Eytan Gidron]

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?

[Langston Holland]

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.

[Franz Francis]

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

[Iain_Macdonald]

Hi,

Well all good things come to those who wait!   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   Handbags at dawn!

Iain.

[Iain_Macdonald]

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 ( TH118’s? Heck yes.

Surely 3db peak output.  

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.

[Jeff Wheeler]

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.

[Langston Holland]

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.

[Bob Lee (QSC)]

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.

Thank you for that!

[Jason Joseph]

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..?