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If you pick it, it will never heal

Hi guys

You know, its funny sort of, I think you guys probably have a lot more in common than you imagine, I mean in addition to a love of sound.
It appears that largely the differences may be a result of which camp each associates themselves with.
Keep in mind, this division is one that the magazines have constructed, there is no reason not to be lead by ones ears and measurements, logical conclusions and acceptance / investigation of the unknown.

Tubeguy, keep in mind in particular, you are not experiencing the typical SET setup, you said you had a 40W class A amp. Class A amplifiers may statically measure more THD than what people are used to BUT they exhibit a favorable property according to what Earl Geddes found, that is, ones ears are more sensitive to nonlinearity as one approaches Zero crossing AND as the level falls.
Here, on a class A system, the system generally becomes increasingly linear as the signal decreases, with class AB or B systems, the crossover distortion becomes proportionally larger and larger and the level falls.
With your amplifier, you may well have a +3dB head room to asymmetric clipping (which is 2nd order distortion which is hard to hear) and so you may have +6dB over RMS in “effective” peak output. This is 160Watts.

To me at least, when you say SET, what comes to mind is 4 Watts at clipping with 90dB sensitivity speakers.
I forget what you said your current speakers are but your RCA’s ought to be about 95-98 dB 1W1M depending on the woofer and low cutoff so your not talking about an anemic system by any means. For a speaker that had a sensitivity of say 90 dB, your talking about an equivalent output as you would get with 640Watts.

So far as SS amplifiers and CD horns, well, that’s what I use too.
The speakers are 100dB 1W 1M with an amplifier that can putout 1300Watts into each at 1% THD. While it is a pro sound amplifier (QSC pl236), I had a chance to compare it side by side with my old amplifier, a Threshold stasis.
While I could hear small to medium differences between them and the other amplifiers (curiously, it was always in the dynamic tails of sounds), the pl236 and stasis were identical up to some level. At that point, the pl began to sound more lively.
A check with an oscilloscope showed that there level where they began to sound different corresponded to instantaneous clipping on the threshold.
This was significantly below the level where the 0dB indicator was illuminated; this was very very short and NOT audible as “clipping”

So far as religion, this like so many things that probably should be talked about, someone decided they had authority to decide that it is no longer P.C. in our media controlled America anymore.
Personally, Religion is like a personal Bet you make within your conscience, that can effect how you live your life and interact with those around you. For sure, every one will eventually know the truth, either way, no one can know for sure until then..
While there have been many religious appearing crooks and buffoons, the Hollywood / Madison Ave popular culture which is replacing religion (which generally formed peoples morals) is only good for retailers etc and of course, for greatly increased police and security forces to “protect us from us”, various forms of government Nanny’s and the layers of government staff needed to over see it all.
I would comment that I enjoyed singing in the choir and it is a good way to hear singing and became interested in low frequency sound at Church.
This lead to the Servodrive woofer 20 some years ago.
http://systemscontractor.com/articles/publish/article_977.shtml

Tubeguy, I would be delighted to help work on your RCA’s, these are classic speakers.
You are correct, the crossovers are normally not interchangeable and they way they were done “back then” was without the wonders of a 3Ghz Pentium or even a 4MHz 286.
If you don’t have any drivers then I would urge you to go with one of the very good modern ones. (If Paul has / will part with a pair of those TAD’s he had a while back, these would be good.)
This, when driven directly will not have perfectly flat response as what you measure on axis is partly governed by the horns radiation patterns as well as the drivers acoustic power at each frequency.
Also, the typical horn driver has a very complicated impedance, it is not a “resistor” by any means. This is partly why horn crossovers are hard to design, you cannot “look it up” and get something flat.

What I do for work stuff is measure the speaker up on a tower with the TEF machine.
I take a response magnitude and acoustic phase curve for each driver and in impedance magnitude and phase and import these into a Spice like modeling program.
The impedance curve can be defined by an equivalent circuit if R’s L’s and C’s which produce the same response. As may be no surprise, all of the drivers dynamic elements like mass and compliance, radiation resistance, once reflected through the Motor’s electrodynamic conversion, become these electrical elements.
This way, the computer program knows exactly what the load looks like, knows where the response needs to be changed and so on.

Does Paul or one of the audio guys down their have or have access to a TEF machine?
I could explain what / how to measure and they could e-mail the files I need.
Best.

Tom



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