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SH-50 limiters.
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<blockquote data-quote="Langston Holland" data-source="post: 34995" data-attributes="member: 171"><p>Re: SH-50 limiters.</p><p></p><p>Hi Helge:</p><p></p><p>That is a wonderful rig you have - and the Lake limiters are the best I've ever worked with. Your calculations are perfect, but I do have a few thoughts:</p><p></p><p>1. I am confident that Danley intended you to calculate the voltage thresholds using the nominal 4Ω impedance, just as you have.</p><p></p><p>2. Danley will soon clear up this confusion by specifying max. long-term and peak voltages in addition to watts, right Ivan? <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f642.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":)" title="Smile :)" data-smilie="1"data-shortname=":)" /></p><p></p><p>3. The Lake processors use look-ahead peak limiters and nothing gets past the peak threshold. I've fed DLP inputs at 15dBu above the threshold with 6.5ms sine bursts up to 45kHz to prove it to myself.</p><p></p><p>4. Because the peak limiter is so effective, you are free to use the remainder of the limiter functions to optimize sonics at higher SPL's. In that pursuit it is best to use the automatic time constant function for the attack and release values and a -6dB "MaxRMS Corner".</p><p></p><p>Therefore, given your 32dB amp gain, the 6dBu RMS threshold and 9dBu peak threshold follows the mfg recommendations perfectly and I'm confident will protect the loudspeaker from damage, though you may find those are not the best thresholds to use sonically. Also keep in mind that even the most compressed music has a long-term "RMS" level 15dB or more below the peaks.</p><p></p><p>In your case, this is what I'd do:</p><p></p><p>Drop your MaxRMS threshold to 3dBu and MaxPeak threshold to 6dBu. Play some well recorded very dynamic music with good vocals that you really like at the point where either your console's output or processor's input is just about to clip. Does it still sound good? It should with that processor if the loudspeakers are up to the task, which I think they will be. If you felt the loudspeaker sound was getting ugly and you weren't able to go to the console's full output, back both thresholds down 1dBu, rinse, repeat. If you felt everything sounded fine and want more output, increase both thresholds 1dBu, rinse, repeat, but don't go above the mfg recommendation unless you're a nut case like me.</p><p></p><p>===</p><p></p><p>My pet project lately has been limiting. I've been measuring loudspeaker passbands with short-term sine bursts while observing distortion plots, scope displays, and listening to find the mechanical and listenable peak limits of the device (two very different levels in many cases). After a couple of dozen hours at this I've made the following observations:</p><p></p><p>1. Limiter settings on processors are even more deceptive and less transferable between brands/models than filters. This is yet another thing that must be measured to be verified.</p><p></p><p>2. The Lake processor means what is says when you set the peak threshold. Example: set it to +10dBu and feed it with a sine burst at +15dBu and put an RMS reading meter (almost all of them) on the output and you'll read +7dBu. This is because a sine wave has a 3dB crest factor and the Lake limiter really is limiting at the +10dBu peaks. I'm aware of no other processor at this point that does this, i.e., tells the truth.</p><p></p><p>3. Most mfg's of high quality professional loudspeakers correctly specify the long-term power capability of their passbands. They are all over the map on specifying the correct peak capability. Most just add 6dB to the long-term rating and call it a day, but this is a lie (sonically) except in the case of the better designed low and sub passbands. Mids and Highs? With good sound? Forget it.</p><p></p><p>4. The guys that design the limiters in loudspeaker processors apparently have never seen a loudspeaker (excluding the Lake). You put a pretty number in your limiter's dBu field and you get that at the output plus another 3dB due to the crest factor - with continuous sine waves - but much, much higher peaks with real world short-term signals even with the ratio set infinity:1 in many cases. You think you're protecting your loudspeakers from over excursion when those limiter LED's come on? Not if the BE keeps pushing the faders up. Are you getting uncomfortable yet?</p></blockquote><p></p>
[QUOTE="Langston Holland, post: 34995, member: 171"] Re: SH-50 limiters. Hi Helge: That is a wonderful rig you have - and the Lake limiters are the best I've ever worked with. Your calculations are perfect, but I do have a few thoughts: 1. I am confident that Danley intended you to calculate the voltage thresholds using the nominal 4Ω impedance, just as you have. 2. Danley will soon clear up this confusion by specifying max. long-term and peak voltages in addition to watts, right Ivan? :) 3. The Lake processors use look-ahead peak limiters and nothing gets past the peak threshold. I've fed DLP inputs at 15dBu above the threshold with 6.5ms sine bursts up to 45kHz to prove it to myself. 4. Because the peak limiter is so effective, you are free to use the remainder of the limiter functions to optimize sonics at higher SPL's. In that pursuit it is best to use the automatic time constant function for the attack and release values and a -6dB "MaxRMS Corner". Therefore, given your 32dB amp gain, the 6dBu RMS threshold and 9dBu peak threshold follows the mfg recommendations perfectly and I'm confident will protect the loudspeaker from damage, though you may find those are not the best thresholds to use sonically. Also keep in mind that even the most compressed music has a long-term "RMS" level 15dB or more below the peaks. In your case, this is what I'd do: Drop your MaxRMS threshold to 3dBu and MaxPeak threshold to 6dBu. Play some well recorded very dynamic music with good vocals that you really like at the point where either your console's output or processor's input is just about to clip. Does it still sound good? It should with that processor if the loudspeakers are up to the task, which I think they will be. If you felt the loudspeaker sound was getting ugly and you weren't able to go to the console's full output, back both thresholds down 1dBu, rinse, repeat. If you felt everything sounded fine and want more output, increase both thresholds 1dBu, rinse, repeat, but don't go above the mfg recommendation unless you're a nut case like me. === My pet project lately has been limiting. I've been measuring loudspeaker passbands with short-term sine bursts while observing distortion plots, scope displays, and listening to find the mechanical and listenable peak limits of the device (two very different levels in many cases). After a couple of dozen hours at this I've made the following observations: 1. Limiter settings on processors are even more deceptive and less transferable between brands/models than filters. This is yet another thing that must be measured to be verified. 2. The Lake processor means what is says when you set the peak threshold. Example: set it to +10dBu and feed it with a sine burst at +15dBu and put an RMS reading meter (almost all of them) on the output and you'll read +7dBu. This is because a sine wave has a 3dB crest factor and the Lake limiter really is limiting at the +10dBu peaks. I'm aware of no other processor at this point that does this, i.e., tells the truth. 3. Most mfg's of high quality professional loudspeakers correctly specify the long-term power capability of their passbands. They are all over the map on specifying the correct peak capability. Most just add 6dB to the long-term rating and call it a day, but this is a lie (sonically) except in the case of the better designed low and sub passbands. Mids and Highs? With good sound? Forget it. 4. The guys that design the limiters in loudspeaker processors apparently have never seen a loudspeaker (excluding the Lake). You put a pretty number in your limiter's dBu field and you get that at the output plus another 3dB due to the crest factor - with continuous sine waves - but much, much higher peaks with real world short-term signals even with the ratio set infinity:1 in many cases. You think you're protecting your loudspeakers from over excursion when those limiter LED's come on? Not if the BE keeps pushing the faders up. Are you getting uncomfortable yet? [/QUOTE]
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