Gentlemen,
My first time here so... Hello!
And best wishes to all. Thanks Carl, for letting me in the door.
Thought I'd stop in and offer some possible insight regarding your experience with Ken's Timepieces. If the Manleys are 100 w/ch (?), then all I would need to do some calculations would be the SPL and distance from the speakers the measurement was taken at.
Regardless of the exact numbers, I'd like to ask if you guys are familiar with what the results of amplifier clipping are? I don't want to "talk down" to or offend anyone, but I'll take liberty and elaborate a little.
First, be it tube or solid state...ALL amplifiers turn musical signal peaks into "square waves" when they are driven into clipping. Square waves examined under under Fourier analysis (a mathmatical process) are equivalent to an infinite series of odd-ordered (1/3, 1/5, 1/7 etc.) harmonics with decreasing amplitude as the harmonic order increases, starting with the fundamental tone that has been "clipped." This is a very ugly thing to hear.
Now...a fast rising transient can be clipped without the listener ever detecting it as such. Only when severe clipping (i.e., gross distortion) occurs is the listener fully aware that the amplifier is being over driven. Short duration clipping on the order of 1 or 2 millisecond long transients are virtually never detected by our hearing as "obvious" distortion. Rather, as very slight clipping begins to occur (once every few seconds) the listener wil virtually never know - regardless of hearing accuity. Such small amounts of clipping occur on virtually all systems of less than several hundred watts of power when playing back the wide dynamic range music being provided by todays digital formats.
It is not uncommon for a signal to be anywhare from 10 to 20dB higher in amplitude than the "average" signal level that our brains unerstand as "volume" or SPL. 10dB peaks require the amplifier to put out 10 times the power as that required to achieve the average volume. A 20dB peak would require that same amp to put out 100 times the power! So...say your cruising along at 10 watts average power and a 20dB signal comes along (remember...it only lasts maybe for 1/1000th of a second). Now that same amp has to produce 1000 watts to keep from clipping that signal. You can see where I'm going with this.
Fortunately, 20dB peaks aren't really all that common, but 10dB ones certainly are - very common in fact.
Now, your having a little rave and you swap out one speaker (95dB SPL @ 2.83V/1M) for another and the new speaker is about 10dB less efficient/sensitive (85dB SPL @ 2.83V/1M) than the other. There goes 10dB of amplifier headroom right out the window. Oh...and lest you start comparing impedance curves, the 8-Ohm rating/output voltage ability of the amp is all that really matters. A 1 millisecond wide peak is equivalent to 1/2 cycle of a 500Hz tone. Few 4-Ohm rated speakers are actually 4-Ohms at 500Hz - they're usually closer to 8-Ohms (even ours). A 2mS wide transient is equivalent to 1/2 cycle at 250Hz - still out of the "low Z" region (bass) for most speakers. In any case, the issue of clipping is far more voltage dependant than current and hence sensitivity of each speaker at 2.83V is more indicative of the difference between models than their actual 1 watt rating. Even if we compare watts to watts, in this case that means we loose "only" 7dB of headroom. Ask any amp manufacturer if he would like "only" another 7dB of headroom in his amp at no extra cost.
So now you're not clipping once every few seconds - you're clipping maybe several times a second. Still short duration pulses - but far more frequent. Now many more of those "odd-ordered" harmonics begin to "splash" all over your nice clean "average level" signals. What do you suppose that would sound like? That's right...it creates a presentation that is somewhat bright and forward. Now, how much the more so would this be evident in a speaker that is KNOWN for being extremely revealing and offers a flat response out to about 24KHz?
Then, you put the original speaker back in the system and remember...it's at least 6dB more sensitive. All of a sudden that bright, forward quality is gone and a "laid back" sound emerges. Ooops! Crap!!! AFTER we turn the volume back down, that is. Gotta remember to turn that knob down first next time. Thank God we didn't blow that higher sensitivity speaker.
Yeah... that's a real good indicator as to just how much you were pushing that amp. But... seeing that you guys learned that lesson many years ago, that event never took place. Instead, you're an experienced audiophile now so you
always turn the volume down first before you change anything in the system. And in so doing...you don't have that blast or ear shattering volume to make you realize just how hard you were really pushing that amp. That darned lower sensitivity speaker is just too bright and forward sounding - that's the problem. Sorry, just not my cup of tea.
NOW...you know why I have recommended a pretty big amp for the Timepieces for years now. Without that, they often get the blame. I'm just thankful you were using a tube amp with it's "softer" clipping characteristics or all of you would have run screaming out of the room.
Sorry, don't mean to offend anyone - that's just been my experience with our speakers on many occasions. I can't stand to even listen to the TPs on less than about 150w/ch of SS amplification. 100 watts of tube power will work...but back off on your SPL expectations. Either that...or sit closer.
Oh well, maybe next time.
Take care,
-Bob