This is a Danley support question but I thought it might be of broader interest, so I post here.
I'm not trying to wring every last dB out of the system and I run "normal" (high crest factor) music and speech. I consider the limiters a protective device and an indicator of maximum output and do not, as a matter of course, run the system into the limiters.
For the peak limiter setting I'm using the peak voltage corresponding to 2 times the AES power rating into the nominal impedance, with instantaneous attack. This is 150 V for the SH-46 and 165 V for the TH-118.
For the average limiter I'm using the RMS voltage mode, as opposed to true power, so that the limiter continues to protect even when parallel speakers are not present or a connection to a parallel speaker is lost. For the power value I'm using 1/2 the AES power rating of the largest driver(s). This is 700 W for the SH-46 and 850 W for the TH-118. This is consistent with both Danley's and Powersoft's recommendations. (And, yes, I've taken into account the speaker impedance in powersoft's "Power vs V @ 8 Ohms" mode so the actual settings are 350 W and 425 W, respectively.)
My question is, what time constants to use, or, what is the thermal time constant of the affected VCs (voice coils)? Powersoft recommends 4 s attack and 8 s release for speakers with a 4 in. VC woofer. This sounds reasonable for the TH-118 given that it has a 4.5 in. VC and the release could be 1 minute so far as I am concerned since I don't plan routinely to run into limiting.
The SH-46 is a bit more of a quandary since, theoretically at least, the high power could occur at higher frequencies and affect the smaller drivers. This is complicated by the fact that there is a passive crossover that involves attenuation, so the power rating and thermal time constants of the resistors might come into play, but probably not, so long as I keep away evil people with sine wave generators. Any guidance is appreciated.
As an aside, this got me thinking about ways to measure VC thermal time constant by, for example, running program of known average power for a certain time and then quickly bringing the cone to rest and measuring the DC resistance, from which the VC temperature can be extrapolated. I assume this is what loudspeaker manufacturers do. Since the time constant is affected by the forced convection of the moving assembly, this gets interesting.
--Frank
I'm not trying to wring every last dB out of the system and I run "normal" (high crest factor) music and speech. I consider the limiters a protective device and an indicator of maximum output and do not, as a matter of course, run the system into the limiters.
For the peak limiter setting I'm using the peak voltage corresponding to 2 times the AES power rating into the nominal impedance, with instantaneous attack. This is 150 V for the SH-46 and 165 V for the TH-118.
For the average limiter I'm using the RMS voltage mode, as opposed to true power, so that the limiter continues to protect even when parallel speakers are not present or a connection to a parallel speaker is lost. For the power value I'm using 1/2 the AES power rating of the largest driver(s). This is 700 W for the SH-46 and 850 W for the TH-118. This is consistent with both Danley's and Powersoft's recommendations. (And, yes, I've taken into account the speaker impedance in powersoft's "Power vs V @ 8 Ohms" mode so the actual settings are 350 W and 425 W, respectively.)
My question is, what time constants to use, or, what is the thermal time constant of the affected VCs (voice coils)? Powersoft recommends 4 s attack and 8 s release for speakers with a 4 in. VC woofer. This sounds reasonable for the TH-118 given that it has a 4.5 in. VC and the release could be 1 minute so far as I am concerned since I don't plan routinely to run into limiting.
The SH-46 is a bit more of a quandary since, theoretically at least, the high power could occur at higher frequencies and affect the smaller drivers. This is complicated by the fact that there is a passive crossover that involves attenuation, so the power rating and thermal time constants of the resistors might come into play, but probably not, so long as I keep away evil people with sine wave generators. Any guidance is appreciated.
As an aside, this got me thinking about ways to measure VC thermal time constant by, for example, running program of known average power for a certain time and then quickly bringing the cone to rest and measuring the DC resistance, from which the VC temperature can be extrapolated. I assume this is what loudspeaker manufacturers do. Since the time constant is affected by the forced convection of the moving assembly, this gets interesting.
--Frank
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