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Powersoft K3, K20, M50Q (Part II)
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<blockquote data-quote="Langston Holland" data-source="post: 48921" data-attributes="member: 171"><p>Re: Powersoft Digam K3, K20, M50Q (Part 2e)</p><p></p><p><strong>Powersoft Damping Control</strong>:</p><p></p><p>This is so unusual that I've devoted a special section to it. Wouldn't it be lovely if you could, say, drive a subwoofer array with a net nominal impedance of 2Ω with a 100' 14 AWG cable and have it sound the same as if it were at the end of a 10' 4 AWG cable? That was what went through my mind the first moment I heard of this feature, the next moment brought: So… What's the Catch?</p><p></p><p>Crown released a cool amp called the "Delta Omega 2000" in 1983 with "active control for the speaker voice coil". Otherwise known as an adjustable feedback loop from the amplifier's output to input to simulate a negative resistor. This is done in an attempt to offset the loudspeaker cable resistance, voice coil resistance and heating, or maybe just for fun to do the opposite and turn your tight, low distortion horn loaded subs into sloppy sounding direct radiators for a DJ! Infinite damping factor or none. Simple huh? How many amps do YOU know on the market that have this feature? Like dude, if this makes my subs sound better, I'll just turn that little knob more and more and it'll sound better and better AND smoke. Runaway oscillation. This is one of those simple concepts that obviously is not so simple to execute.</p><p></p><p>Powersoft's damping control works by sensing output current and returning a calculated voltage back to the DSP's input. It's basic I*R = E from Ohm's Law that uses the resistor value you select (range +/-2 Ohms) to multiply by the actual current the amp delivers to its load. Very clever. When you engage the damping control feature you'll notice that a 400Hz low pass filter is inserted regardless of resistor size selected. The longer wavelengths probably make the unavoidable latency (this is DSP) of the feedback loop much less of an issue and reduce the potential for oscillation. Only the LF passbands really benefit from this sort of thing anyway.</p><p></p><p>The following measurement is not at all indicative of the effect this damping control feature will have on a real loudspeaker. This measurement is into a flat resistance, nothing like the typical double-humped impedance curve of a direct radiator subwoofer. What this measurement shows is that the voltage adjustment does in fact respond directly to current flow into the load. The general idea is that you add a negative resistance value into the Powersoft amp that equals the positive resistance of the cable. The amp will then output more voltage to regions of the passband in proportion to current flow. Since it follows Ohm's Law, it works. The amp will run out of voltage swing the same as before, but the sonic contribution of the cable will be gone. Technically this is very cool, but I do wonder if the market may have become used to what they hear now and not like the cable-less sound. TBD.</p><p></p><p><u>K20 Damping Control Transfer Functions into Fixed Resistances</u>:</p><p></p><p><img src="http://soundscapesweb.com/files/PSW/AmpTests4/K20Damping.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><u>Harsh Reality</u>:</p><p></p><p>You cannot overcome the laws of physics with clever engineering, only politicians are able to do this. This cool feature can allow you to achieve the SONIC characteristics of a short loudspeaker cable run, or no cable run at all, or even of a much longer cable than is being used. Nevertheless, you will still have voltage division going on due to the actual loudspeaker cable resistance in use and you are still throwing away output with that resistance.</p><p></p><p><u>Application of Harsh Reality</u>:</p><p></p><p>Keep the round-trip loudspeaker cable resistance down to about 5% of the voice coil(s) resistance you're driving, which will limit cable losses to less than 1/2dB. Practically speaking, using 12 AWG 2 wire cable will allow a 50 foot run to a 4Ω load, twice that into an 8Ω load and half that into a 2Ω load. With subs use all four wires of the NL4 cable. Paralleling each pair of wires will obviously cut your resistance in half, it also drops the effective AWG by 3. Typical 14 AWG 4 wire cable used in this way is equivalent to an 11 AWG cable. Your amp racks and subs will need to be wired appropriately of course.</p><p></p><p><strong>FIR Filters</strong>:</p><p></p><p>The quantity and power of the processing available in both the Powersoft and Lake products are a dream come true for the loudspeaker designer and end user. Both offer loads of parametric EQ with independently adjustable skirts. Both allow multiple input filter "pages" that I find useful for separating preset personalities relating to HF absorption compensation, etc. Both have 2nd order all pass filters. There are differences in implementation that are well thought out on both sides, but it would take months of experience with the Powersoft amps for me to comment in depth. My bias is that the Lake is the standard by which all others are judged and the Powersoft processing is a very serious competitor. One significant advantage with the Powersoft processing is that it allows direct FIR coefficient download for manufacturers to implement processing characteristics that are impossible any other way. Powersoft makes both EAW focusing and Fulcrum Acoustic TQ processing available in this way. It is the future and it's about time. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p></p><p>Powersoft chose to make its user selectable FIR filters a mid to high transition tool with a fixed latency of about 5ms. The Lake also allows for crossing lows to mids while staying within useable latencies for live sound (generally </= 10ms). Keep in mind that in the following measurements the Powersoft traces are through an amplifier while the Lake is a stand alone line level processor only. An interesting note that some (or many) Lake users may not be aware of is that the control software doesn't always show differences between FIR filter skirts at different latency selections. I've noticed this with the 8th order LR shaped FIR filters at lower frequencies, such as with the 250Hz filter measurements below.</p><p></p><p><u>Powersoft 400Hz</u>:</p><p></p><p><img src="http://soundscapesweb.com/files/PSW/AmpTests4/PS400Hz.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><u>Powersoft 2.5kHz</u>:</p><p></p><p><img src="http://soundscapesweb.com/files/PSW/AmpTests4/PS2.5kHz.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><u>Lake 250Hz</u>:</p><p></p><p><img src="http://soundscapesweb.com/files/PSW/AmpTests4/Lake250Hz.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><u>Lake 2.5kHz</u>:</p><p></p><p><img src="http://soundscapesweb.com/files/PSW/AmpTests4/Lake2.5kHz.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>(End Part 2e)</p></blockquote><p></p>
[QUOTE="Langston Holland, post: 48921, member: 171"] Re: Powersoft Digam K3, K20, M50Q (Part 2e) [B]Powersoft Damping Control[/B]: This is so unusual that I've devoted a special section to it. Wouldn't it be lovely if you could, say, drive a subwoofer array with a net nominal impedance of 2Ω with a 100' 14 AWG cable and have it sound the same as if it were at the end of a 10' 4 AWG cable? That was what went through my mind the first moment I heard of this feature, the next moment brought: So… What's the Catch? Crown released a cool amp called the "Delta Omega 2000" in 1983 with "active control for the speaker voice coil". Otherwise known as an adjustable feedback loop from the amplifier's output to input to simulate a negative resistor. This is done in an attempt to offset the loudspeaker cable resistance, voice coil resistance and heating, or maybe just for fun to do the opposite and turn your tight, low distortion horn loaded subs into sloppy sounding direct radiators for a DJ! Infinite damping factor or none. Simple huh? How many amps do YOU know on the market that have this feature? Like dude, if this makes my subs sound better, I'll just turn that little knob more and more and it'll sound better and better AND smoke. Runaway oscillation. This is one of those simple concepts that obviously is not so simple to execute. Powersoft's damping control works by sensing output current and returning a calculated voltage back to the DSP's input. It's basic I*R = E from Ohm's Law that uses the resistor value you select (range +/-2 Ohms) to multiply by the actual current the amp delivers to its load. Very clever. When you engage the damping control feature you'll notice that a 400Hz low pass filter is inserted regardless of resistor size selected. The longer wavelengths probably make the unavoidable latency (this is DSP) of the feedback loop much less of an issue and reduce the potential for oscillation. Only the LF passbands really benefit from this sort of thing anyway. The following measurement is not at all indicative of the effect this damping control feature will have on a real loudspeaker. This measurement is into a flat resistance, nothing like the typical double-humped impedance curve of a direct radiator subwoofer. What this measurement shows is that the voltage adjustment does in fact respond directly to current flow into the load. The general idea is that you add a negative resistance value into the Powersoft amp that equals the positive resistance of the cable. The amp will then output more voltage to regions of the passband in proportion to current flow. Since it follows Ohm's Law, it works. The amp will run out of voltage swing the same as before, but the sonic contribution of the cable will be gone. Technically this is very cool, but I do wonder if the market may have become used to what they hear now and not like the cable-less sound. TBD. [U]K20 Damping Control Transfer Functions into Fixed Resistances[/U]: [IMG]http://soundscapesweb.com/files/PSW/AmpTests4/K20Damping.png[/IMG] [U]Harsh Reality[/U]: You cannot overcome the laws of physics with clever engineering, only politicians are able to do this. This cool feature can allow you to achieve the SONIC characteristics of a short loudspeaker cable run, or no cable run at all, or even of a much longer cable than is being used. Nevertheless, you will still have voltage division going on due to the actual loudspeaker cable resistance in use and you are still throwing away output with that resistance. [U]Application of Harsh Reality[/U]: Keep the round-trip loudspeaker cable resistance down to about 5% of the voice coil(s) resistance you're driving, which will limit cable losses to less than 1/2dB. Practically speaking, using 12 AWG 2 wire cable will allow a 50 foot run to a 4Ω load, twice that into an 8Ω load and half that into a 2Ω load. With subs use all four wires of the NL4 cable. Paralleling each pair of wires will obviously cut your resistance in half, it also drops the effective AWG by 3. Typical 14 AWG 4 wire cable used in this way is equivalent to an 11 AWG cable. Your amp racks and subs will need to be wired appropriately of course. [B]FIR Filters[/B]: The quantity and power of the processing available in both the Powersoft and Lake products are a dream come true for the loudspeaker designer and end user. Both offer loads of parametric EQ with independently adjustable skirts. Both allow multiple input filter "pages" that I find useful for separating preset personalities relating to HF absorption compensation, etc. Both have 2nd order all pass filters. There are differences in implementation that are well thought out on both sides, but it would take months of experience with the Powersoft amps for me to comment in depth. My bias is that the Lake is the standard by which all others are judged and the Powersoft processing is a very serious competitor. One significant advantage with the Powersoft processing is that it allows direct FIR coefficient download for manufacturers to implement processing characteristics that are impossible any other way. Powersoft makes both EAW focusing and Fulcrum Acoustic TQ processing available in this way. It is the future and it's about time. :) Powersoft chose to make its user selectable FIR filters a mid to high transition tool with a fixed latency of about 5ms. The Lake also allows for crossing lows to mids while staying within useable latencies for live sound (generally </= 10ms). Keep in mind that in the following measurements the Powersoft traces are through an amplifier while the Lake is a stand alone line level processor only. An interesting note that some (or many) Lake users may not be aware of is that the control software doesn't always show differences between FIR filter skirts at different latency selections. I've noticed this with the 8th order LR shaped FIR filters at lower frequencies, such as with the 250Hz filter measurements below. [U]Powersoft 400Hz[/U]: [IMG]http://soundscapesweb.com/files/PSW/AmpTests4/PS400Hz.png[/IMG] [U]Powersoft 2.5kHz[/U]: [IMG]http://soundscapesweb.com/files/PSW/AmpTests4/PS2.5kHz.png[/IMG] [U]Lake 250Hz[/U]: [IMG]http://soundscapesweb.com/files/PSW/AmpTests4/Lake250Hz.png[/IMG] [U]Lake 2.5kHz[/U]: [IMG]http://soundscapesweb.com/files/PSW/AmpTests4/Lake2.5kHz.png[/IMG] (End Part 2e) [/QUOTE]
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