I've found some posts on this topic but nothing really satisfactory. I'm brainstorming a semi-active 3 way speaker system where the woofer (working up to 300-400 hertz) would be active but the low level input signal for its dedicated amplifier would be taken from the speaker level that's driving the mid and tweeter (which are passive).
I know this has been done before and is being done for example in the new Paradigm Founder 120H speakers. Unless those speakers suck, which I don't think they do since they are the flagship of the line, it appears that this can be successfully pulled off.
I understand that the one seemingly obvious downside is that you are compounding the inherent distortion of two amplifiers but since there is no mid and treble frequencies involved and most amplifiers have low enough distortion in that range I'm assuming any deleterious effects would be inconsequential.
My question is to those that have experience in this or can shed some well informed light on the subject. How much would you lose in transparency and dynamics (if at all) in those first few octaves (up to 300-400hz) by converting the speaker level down to line level? Is there a better way to implement this asides from using just resistors? What drawbacks are there to doing this?
I know this has been done before and is being done for example in the new Paradigm Founder 120H speakers. Unless those speakers suck, which I don't think they do since they are the flagship of the line, it appears that this can be successfully pulled off.
I understand that the one seemingly obvious downside is that you are compounding the inherent distortion of two amplifiers but since there is no mid and treble frequencies involved and most amplifiers have low enough distortion in that range I'm assuming any deleterious effects would be inconsequential.
My question is to those that have experience in this or can shed some well informed light on the subject. How much would you lose in transparency and dynamics (if at all) in those first few octaves (up to 300-400hz) by converting the speaker level down to line level? Is there a better way to implement this asides from using just resistors? What drawbacks are there to doing this?
Not something I would do because there is no advantage to the mid and high frequencies because their amp is still playing full range. The high to low level converters are also not renowned for their sound quality. You would be better off doing it at preamp level even if you run a preamp cable for the lows and a speaker cable to the mids and highs from their amp. If you were able to do a high pass for the mud and highs you would take the load off their amp enabling cleaner, louder output.
I never said the mid and tweeter wouldn't have a high pass filter. In fact I mentioned in brackets that the mid and tweeter are passive, so by default they will have a passive crossover network, including a high pass on the mid.
The mids and highs have crossovers but the amp is still running full range to feed the bass amp. That is less than optimal as the power is basically being wasted. All that power going to the low frequencies could be used on the muds and highs with an active XO. Those high level to low level adaptors are notoriously bad plus you are amplifying the distortion of the first amp to drive the bass.
Umm no, I don't think so. Anything I've ever read about it states the the amplifier driving the high-to-low circuit is virtually unaffected as it's driving a high impedance dummy load which just essentially sniffs the signal.
Yes I did mention I was aware of the compounded distortion in my OP, but two things to remember is that distortion is less perceptible/objectionable at low frequencies, and amplifiers have significantly lower distortion in low frequencies as opposed to higher up. Why would Paradigm, Gryphon, Adam, and i'm sure many others I don't know of take this approach in their extremely expensive/flagship speakers if it was notoriously bad?
The problem is not that the upper amp is driving the lower amp via high level inputs, it is that the power used in the lower spectrum is being wasted as it is not actually driving a speaker. If you use and active crossover before both amps the upper amp is relieved of the power sent to the bass. More energy van be used to run the high end as a result. You can get an electronic XO for not much more than a wasteful high to low adaptor. I’ve been there and seen how much more dynamic the system is with an active XO. You may like it your way so give it a shot!
No power is being wasted in a passive speaker that's just a mid/high box with high pass at 300-400Hz. The passive crossover increases the impedance with falling frequency so that the power amplifier doesn't have to deliver any current down low.
Sure the power amplifier is passing the entire bandwidth but it's only going to be delivering current into the mid and tweeter, nothing else.
And as to high impedances troubling the power amplifier? It won't have a high impedance load it's going to be driving the high level thingy in parallel with the mid/tweeter box.
Besides no amplifiers I've ever used, or come across, have a problem driving high impedances, it's the low impedances that cause trouble.
Sure the power amplifier is passing the entire bandwidth but it's only going to be delivering current into the mid and tweeter, nothing else.
And as to high impedances troubling the power amplifier? It won't have a high impedance load it's going to be driving the high level thingy in parallel with the mid/tweeter box.
Besides no amplifiers I've ever used, or come across, have a problem driving high impedances, it's the low impedances that cause trouble.
Thank you, 5th Element. Someone that knows what they're talking about. I was writing my reply but you beat me to it!
No power is being wasted at the lower frequencies because there is no load there, BUT amplifier driving the passive part must still swing voltage s much as before.
Which brings it closer to clipping anyway and will actually make it clip often as much as if it were driving woofers.
So it´s a waste of power/headroom even if no woofer is driven.
Again, first amplifier will clip as much as before.
You have a voltage problem, not a current/power one.
EDIT: I see you don´t even mention an active crossover, only the passive highpass present in the first cabinet.
So I must deduce your attenuator sends full range to the woofer amp.
That is also a waste of power, resources, and will make for a distorted/clipped mid/high signal coming out of the woofer when you play loud.
The solution, of course, is to use an active crossover at the preamp output, use its mid/high signal to drive your current amplifier, and low signal to drive Woofer amp.
Cleanest setup and best of both Worlds.
And only passive crossover still needed will be that separating Mids from Highs.
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Hehe OK but if your amplifier is clipping, then you have chosen an inadequate amplifier for the purpose either way you flip it. That's an entirely different problem, no?
No no, the intention would be to use an active low pass filter prior to the amplifier driving the woofer. No passive filter there.
Edit: No preamp involved. Take it out out of the equation. Lets assume we're using a low power integrated tube amp for the passive mid high section.
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