Toilet Paper Tweeter Test - on 3 ways

[onplane]

If you never done the toilet paper tweeter test (TPTT) on your 3-ways (AR-3, AR-3a, AR-2ax, AR-5, etc), you are in for a treat.

Put on your favorite music and get a roll of tp. Now, place one end of the open core over the tweeter (center the tweeter as best you can). Then put your ear up to the other end. (The soft fibers of the tp will help absorb some of the unwanted frequencies.)

What you hear is the tweeter and it's simply amazing how little sound it actually produces!

Then move the core to the mid-driver and it's just about overwheling how much sound it produces.

Regards,

Jerry

[ninohernes]

This is due in part by the way we hear. At the extremes, both low and high, the human ear is not as sensitive. We preceive midrange frequencies as being the loudest. Since the AR-3a is a farily flat speaker, if you measured the output of the drivers, you would find that their output would be within a few dB of each other.

[soundminded]

>What you hear is the tweeter and it's simply amazing how

>little sound it actually produces!

This is my observation as well. In my biamplification setup, it's possible to switch the main drivers off. Even when the system is very loud and adjusted to be on the "bright" side, the tweeters produce remarkably little sound. In my setup, they produce most of the sound above 9khz and nearly all of it above 12 khz. The apparant level is low for at least two reasons, the sensitivity of the human ear is very low at high frequencies as can be seen from the Fletcher-Munsen perceived loudness curves and the actual content is also low. In fact, at the Lansing Heritage site, JBL says that prior to the development of the Paragon D44000 in the late 1950s, they never had to contend with program material above around 12 khz. This agrees with my own experience. Vinyl phonograph recordings made before around 1958 in the US and around 1960 or 1961 in Europe have little or no sound in the top octave the way I hear it. And you can hear it not only on vinyl but on CDs made from the original master tapes as well (this is not due to deterioration of the tapes over time.) Anthologies which package recordings of the same artist made at different times can be very revealing of how the state of the art of recordings advanced. Take a collection of Heifetz recordings and there is a world of difference between recordings made around 1955-1957 and those make around 1958 to 1960. I have concluded that while the loudness of this top octave is a relatively small percentage of the perceived overall sound, its precise nature is very critical in importance, way out of proportion to its amount. It's relative loudness, spectral balance, and directions of arrival IMO have a great influence over how the brain interprets the overall sound, especially in perceiving the direction of the source, critical in the stereophonic effect. Small differences in timing are also critical especially if the same sound arrives from multiple directions with slight delays. The beaming of all high frequencies from a single direction gives recordings of music a characteristic shrillness which is not similar to the sound of actual acoustical instruments. Most acoustical instruments direct most or all of their sound energy away from the audience. Failure to take this into consideration in their design precludes the possiblity of subjectively accurate timbral reproduction of acoustic musical instruments by home high fidelity loudspeakers IMO.

[onplane]

>This is due in part by the way we hear. At the extremes, both

>low and high, the human ear is not as sensitive. We preceive

>midrange frequencies as being the loudest. Since the AR-3a is

>a farily flat speaker, if you measured the output of the

>drivers, you would find that their output would be within a

>few dB of each other.

Hi, Joe!!

I don't doubt for a minute your comments about the non-linear nature of human hearing. Further, I have zero interest in starting a war over "which speaker is better".

Nevertheless, I think folks should know that when I do the TPTT on my TSW-610's (Teleydyne era AR's), I can hear a LOT more sound coming from those titanium tweeters. When I say a lot, I mean double?? maybe triple?? In any event, it's very significant.

Further, according to AR's literature, the TSW-610's cross at exactly the same frequency 5000Hz. (I've never seen the 610 xover schematic, so can't be certain of this.)

(As an aside and I mentioned to Roy as well, my feeling is while the 610's have a superior tweeter, their 5 inch cone mid-range doesn't produce the mid frequencies with anything near the clarity or detail of the 3a's 1.5 inch dome.)

Regards,

Jerry

[onplane]

>I have concluded that while the

>loudness of this top octave is a relatively small percentage

>of the perceived overall sound, its precise nature is very

>critical in importance, way out of proportion to its amount.

>It's relative loudness, spectral balance, and directions of

>arrival IMO have a great influence over how the brain

>interprets the overall sound, especially in perceiving the

>direction of the source, critical in the stereophonic effect.

Soundminded, we have had our differences, but I think you are right on the money here. When I listen to my 610's that produce FAR, FAR more sound out of the tweeters (than my 3a's), I don't perceive a major change in the timbre of the instruments, but I do sense a huge difference in stereo imaging.

I'm guessing this difference is due to the superior tweeter coupled with the acoustic blanket that's trying to minimize spurious reflections.

In any event, soundedminded, your comment about high frequencies and direction appear to have a lot of merit.

Regards,

Jerry