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heya gm.in two posts in the past couple of days in re: crossovers, you mentioned 'high output impedance' in calculating crossovers.
i run an eico hf89-- which i really don't know the output impedance of.. but i've calculated an asymmetrical crossover (2nd order on the bottom, 1st on the top) of about 1450hz, which was in part to do with yer advice previously (thanks again!). i'm wondering, however, if what i CALCULATED is actually what i've got, if there is indeed shifts induced by output impedance-- or if that'd be mitigated by the fact that both drivers are subject to the same high output impedance.
if indeed the OZ is an x factor-- what're the calculations involved to overcome it, or at least incorporate it into the figgers for an XO-- or would it cause some sort of relatively 'standard' shift to 'normal' calculations? i know all passives are reactive.. but that's a part of the scene i had never figured for!
just curious if i missed something along the way!
Follow Ups:
Greets!In my previous posts I was referring to the impact any series resistance from OPTs, inductors, resistors, speaker wiring, had on the driver's Qts, which can be significant for a given alignment. For instance, in the early days the goal was most efficient power transfer because they had so little of it, ergo a damping factor (DF) = 1, which required a very efficient (ultra low Qts) driver so that when matched up to the system was still well damped (Qts = 0.3-0.4). Using T/S for a 515B (Qts = ~0.166), with no series R requires a ~1.21 ft^3/57.2 Hz max flat alignment, but double Re and Qts rises to ~0.325 with the cab ballooning to ~10.03 ft^3/30.3 Hz!
Anyway, as you surmised, all this affects the XO design and why 'textbook' XOs typically don't work as predicted. If you started with measured impedances at the desired XO point, then you're 'golden', otherwise no telling what you wound up with, though if you've physically aligned the horn and satisfied with how it sounds, then it's academic.
GM
gotcha-what a crazy art/science intersection this crossover stuff is...
thanks for the math lesson! i was more curious because of the possible ramifications-- but with what i've got... i'm pretty happy-- so even without that portion of the calcs.. it seems to've turned out AOK!
someday if i ever have access to some serious measurement tools, it'll be really fun to see how close my ear's ideal is to the 'flat measurement' ideal!
thanks again!
Greets!You're welcome! Unless you have perfect pitch and/or a trained ear, then like most folks you'll probably find it a humbling experience.
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