speaker excursion..."mo power"..and bass..Sean

I forgot to mention the "bad things" about clipping. The one thing that everyone forgets to mention when talking about clipping is amplifier stability. Mr Dartford alludes to this when he talks about instability. That is, a note may have a duration of anywhere from milliseconds to a couple of seconds. When an amplifier goes into hard clipping, the duration of that note can be drastically increased due to smearing / saturation. As such, the speaker not only has to deal with more power to dissipate and a greater percentage of power centered higher in frequency ( harmonics ), but it also has to deal with all of that over an increased amount of time ( longer duration ).

It is a combo of the increased power with longer duty cycles that typically "cooks" the voice coil of dynamic drivers. As mentioned above, the driver can't dissipate the heat fast enough, so the end result is "thermal meltdown" ( literally ).

As a side note, this is yet another reason why i feel that it is important to measure the efficiency of a speaker, not just the sensitivity. As most of you may know, the impedance of a speaker changes with frequency. As such, one might be pulling "X" amount of watts at 1 KHz due to the speaker being appr 8 ohms, but at lower frequencies, where it already needs more power to reproduce deep bass, the amp might be producing "XX" watts of power. This increased power comes from the demands of the music AND the demands of an impedance swing. Now if we knew that the amp was more stable ( able to deliver suitable amounts of power into various speaker loads ) and / or factored in this impedance swing in the efficiency of the speaker rating so we knew more of what we were dealing with, this wouldn't be a big deal. Given that not all amps are stable at all impedances, and not all speakers are rated properly ( efficiency vs sensitivity ), this makes our job of selecting suitable amps / speaker combo's even harder. That's because one amp may go into clipping sooner at lower impedances than another amp with identical power ratings as listed at 8 ohms.

Other than that, amplifier loading characteristics and the type of load that each individual speaker presents to the amp is a very difficult thing to try and summarize briefly. What i will say is that, so long as quality is not compromised, you'll never be hurt by having more power. Not only do you reduce the risks and distortions of clipping, but your potential to achieve greater and more consisten levels of control over the driver are also improved. Sean
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Sean, execllent post and I concur with your opinion regarding "direct drive" versus passive designs. As has been explained many times on this board... the logic behind why an active design is generally better seems straight forward and convincing.

Off the top of my head I'm trying to recall an active floorstanding design that's not ported and for some reason I'm drawing a blank.

Sean...you need to start charging people for your responses...at least it will help with your future carpal tunnel syndrome ;o)

All I can say is "wow"...thanks to all for taking the time to explain this. The big-power pathway does make sense and as usual there are always excpetions, like the Orion/active-types, to generalities.

Drew...your numbers-based approach really explains it well. No surprise that Linkwitz has designed the Orions very well. The more I learn about the active approach & Linkwitz in particular the more interesting the Orions become.

Sean...you are an amazing person. Your explanation makes a lot of sense. I caught a little of the past discussion on active speakers, but now that I look into them deeper it really is surprising that they are not more popular. SL's DIY approach is fairly inexpensive when you consider the parts that make them up. Undoubtedly if active types were more common (read: commercially available on wide basis) the "value-based" prices would be stiff. 6000 watts you say... :-)) Some folks warm up the house by tossing a log or two into the wood-burner...I'm guessing you just turn on an amp or two.

Sean...Of course I am a long time believer in biamping, but I do think that the original reason (and I am talking about 50 years ago) was to avoid intermodulation distortion. Power amps have improved so that this is no longer a significant issue. As you say there are power delivery advantages also, but in this regard amplifiers have also improved about tenfold. (Back then a "big" amp was about 25 watts, and now it would be 250 watts or more).

Which leaves us with the elimination of the passive crossover as the remaining advantage. I cannot understand how many people seem to think that driving two separate full range amps into the passive crossover is "biamping".
I have two comments here.

1...It is dangerous to run a tweeter directly from a power amp. Turnon and turnoff can be accompanied by "thumps" that the tweeter won't like, and a loose interconnect can be an instant disaster.

2...Passive crossovers do not absorb power to the degree that you suggest. The simple test for this is to consider how hot they would get if they did absorb a lot of power, particularly since they are usually mounted inside a closed box, and surrounded by insulation. To take the scientific approach: Capacitors (ideal) dissipate zero power. EE101. Real capacitors are near ideal in this regard. Inductors will dissipate power because they cannot be made with zero resistance. The externally mounted 3.5mH inductors of my MG1.6 are 10 AWG air core coils with dc resistance of 0.2 ohms, which is about the same as the original equipment iron core inductors. Since the driver is 4 ohms, 0.2/4 which is 5 percent of the power will end up as heat in the inductor. (But they never feel warm). Resistors are used in crossovers, but not in the signal path except for the tweeter, where some power loss is usually necessary to balance SPL. If the tweeter padding resistor needs to be a large value, the wrong model of tweeter has been used.

What is the basis of your suggestion that lost power will be 50 percent?