[Randyhandy]

Apologies if the answer to this is obvious. I'm curious about the the effects on headroom on a passive vs active speaker system and amplification. For example, is there any difference between  passive model T speakers with a 14B3 amp, and an active model T setup with 21B3 amps. Or, would passive model Ts with a 14B3 be more equivalent to a 3 channel 9B3? Can somebody explain the math? Note, I'm speaking of effective sound pressure, not necessarily sound 'quality', if that makes sense.

[JLM]

Passive crossovers rob lots of power.  Active designs OTOH link amps more effectively to each driver.  My Buchardt A500SE's use (4) 150 watt mono-block amps per channel.  Imagine that in a monitor sized cabinet.

[Randyhandy]

Thanks for the reply. I suppose what I was looking for was the effect of amplification in a passive system vs active system. For example, what would be the equivalent of a 14B3 (900W @ 4ohm) in a passive system. A bunch of 14B3 amps driving highs, mids, lows individually? 21B3 (900/500/500W at 4 ohms) for hi/mid/lo? Maybe a trio of 3B3 amps (300W @ 4ohm) for the hi/mid/lo? Are the effects of individual amplification cumulative in an active system, or something less?

Thanks

[opnly bafld]

If you need it LOUD for a large dance club or for a stadium you would be better off getting different speakers.

You question seems a bit like, which will get me down the street to the market faster an F1 car or Top Fuel drag car?

[Randyhandy]

Yeah, my communication skills really suck. Let me try this another way. No, I'm not trying to build a system that will blow my windows out...that's not the purpose of my question. Let's say, for example, I have a pair of 'passive' Model Ts connected to a 14B3 stereo amp (and it doesn't HAVE to be a 14B3, it could be 4B3...whatever). I know I can drive the speakers to a certain (SPL) level without clipping. Now, in the pursuit of enhanced sound 'quality' (not quantity), I decide to purchase a pair of 'active' Model Ts. How do I determine what amplification I need to get the equivalent sound 'quantity' I had with the passives without clipping. I'm trying to understand the effect of having an amplifier drive 3 drivers, through a crossover, versus an amplifier per driver, not passing through a crossover....quantity wise. Hopefully I got it right this time.

[veloceleste]

I’m not sure an equivalence can be made between passive and active amplification regarding headroom.  The active system more finely controls the behavior of each driver. Attached is the Bryston White paper on their speaker design philosophy and includes a section on active vs. passive speaker set-up. I hope this helps.
https://www.dropbox.com/s/ya5hf6s9fc986a3/Bryston%20Speaker%20Whitepaper.pdf?dl=0

[Randyhandy]

Thanks for the whitepaper...I'll have a look through and see if it offers any clues. I know that going with an active system will cost more due to additional amps. What I'm trying to avoid is overspending for extra amplification (i.e. watts) if I don't need it.

[James Tanner]

Not sure if this helps but going Active typically gets you about 4dB more in efficiency. 
So for 3dB you need double the power ... so if you needed 200 watts to get 85dB on a passive system you would only need 80 watts on an Active.

But the real reason for going Active is driver control and lack of components between the amp output stage and the driver.

best
james

[Randyhandy]

Not sure if this helps but going Active typically gets you about 4dB more in efficiency. 
So for 3dB you need double the power ... so if you needed 200 watts to get 85dB on a passive system you would only need 80 watts on an Active.

But the real reason for going Active is driver control and lack of components between the amp output stage and the driver.

best
james

Yep, that's what I was looking for. Thanks a bunch!
RH