what protection lamps do i need?
in [Live Sound]
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From: TimPerry on 12 Jun 2007 19:44 non-biz(a)hotmail.com wrote: > I have some R&D cases wedges loaded with a 2226h 15" ventagap woofer > and a 2426h comp 1" exit driver. The HF is protected by a 1 amp fuse > and i want to change them over to a lightbulb type circuit. The > amplifier used for these wedges is a QSC EX4000 rated at 1250w/side @ > 4ohms. I am needing advice on lamp # to handle protecting the HF > drivers from burnout, but not starve them for power. > > Thanks in advance to all for your help. > > Eric WHite > Pro Audio Services You might consider using appropriatly sized back to back zeners in parallel with the driver. In effect this makes something called a Diac. It won't effect x-over leading at least until it starts limiting. I believe I saw something like this in an EV cabinet lately. It was a pretty hefty pair of solid state devices in series. Personally i think you will probably get the best sound by bi-amping. Get a smaller amp like a QSC RMX850 for the horns and use and active x-over.
From: Phil Allison on 12 Jun 2007 23:00 "TimPerry" > > You might consider using appropriatly sized back to back zeners in > parallel > with the driver. ** Very bad idea - forget it. > In effect this makes something called a Diac. ** No way it does any such thing. > It won't > effect x-over leading at least until it starts limiting. ** Huh ? Same goes for all limiting methods - fool. > I believe I saw something like this in an EV cabinet lately. It was a > pretty > hefty pair of solid state devices in series. ** EV used a simple voltage clamping cct to protect their puny tweeter horns. Consists of a pair of power transistors wired as active zeners - IIRC. Horrendous idea. The HUGE advantage of thermal ( ie lamp) limiting is that is it effectively a SLOW acting, fast resetting, distortion free, audio limiter which derives its action from the rms current flow in the coil of the driver being protected. If correctly designed ( ie not cobbled together by some idiot roadie ) the outcome is NO effect on the sound quality until the driver concerned cops so much power it is at risk of burn out, THEN the audio power to that driver is reduced to a level that is not destructive. Most useful for situations where high frequency, acoustic feedback puts driver survival at risk. ....... Phil
From: Eeyore on 13 Jun 2007 03:28 TimPerry wrote: > non-biz(a)hotmail.com wrote: > > I have some R&D cases wedges loaded with a 2226h 15" ventagap woofer > > and a 2426h comp 1" exit driver. The HF is protected by a 1 amp fuse > > and i want to change them over to a lightbulb type circuit. The > > amplifier used for these wedges is a QSC EX4000 rated at 1250w/side @ > > 4ohms. I am needing advice on lamp # to handle protecting the HF > > drivers from burnout, but not starve them for power. > > You might consider using appropriatly sized back to back zeners in parallel > with the driver. Might you ? I wouldn't ! Some ppl do have the strangest ideas. > In effect this makes something called a Diac. It does NO SUCH THING at all ! > It won't effect x-over leading at least until it starts limiting. > > I believe I saw something like this in an EV cabinet lately. You didn't. Get some glasses. > It was a pretty hefty pair of solid state devices in series. What EV cabinet ? > Personally i think you will probably get the best sound by bi-amping. You always do. > Get a smaller amp like a QSC RMX850 for the horns and use and active x-over. Yes. Graham
From: TimPerry on 13 Jun 2007 21:24 >> You might consider using appropriatly sized back to back zeners in >> parallel with the driver. > > Might you ? I wouldn't ! Some ppl do have the strangest ideas. sure, and then we can restart the semiannual war about if clipping blows speakers. > > >> In effect this makes something called a Diac. > > It does NO SUCH THING at all ! petty close... either could be used as a clipper. either are used to fire the gate of a triac > > >> It won't effect x-over leading at least until it starts limiting. >> >> I believe I saw something like this in an EV cabinet lately. > > You didn't. Get some glasses. > > >> It was a pretty hefty pair of solid state devices in series. > > What EV cabinet ? i dont remember the model. i have done a couple pair of EV lately for buddies with the same problem... worn out / intermittant jacks. the circuit must work as the horns still work despite being DJized. > > >> Personally i think you will probably get the best sound by bi-amping. > > You always do. > > >> Get a smaller amp like a QSC RMX850 for the horns and use and active >> x-over. > > Yes. > > Graham
From: Phil Allison on 13 Jun 2007 21:34
"TimPerry" > >> >>> In effect this makes something called a Diac. >> >> It does NO SUCH THING at all ! > > petty close... either could be used as a clipper. either are used to fire > the gate of a triac ** Where did you get that IDIOT idea from ?? A "diac" is NOT a simple voltage clamping device like a zener. http://en.wikipedia.org/wiki/DIAC ........ Phil |