Extend The High End Of Heresy 2s

[Shock-Late]

look at townshend audio's fantastic ribbon super tweeters. Supposed to "sound" great, and they look the part.

i think it's now an established fact that a super tweeter adds perceived air and speed i the music, even tho you can't really "hear" those extreme frequencies. it's all about harmonics, i think. Acts like it's virtually modifying the response of the existing tweeter, or something like that... Of course it's another "cable and snake oil" never ending discussion. But i'd say we know virtually nothing about human hearing, we just know what current measurements are able to tell us! So why not. i'd like to give it a try if i had the money (but i need a good sub first )

[JJJeffries]

Hello Fellow Posters!

I asked about an updated crossover for the Heresy 2s and at this time as far as I can determine, no onr has a modified board. There's a chap in South Carolina that plans on building one soon and as for Al, he told me not now.

So, I will listen to the Murata Super Tweeters later today and will post an impression and plan on either buying the MST or go with a modified Altec high horn and a new tube amp or a Monarchy SM-70 stereo amp.

More to follow, please come back now you hear? LOL!

Best,

Craig

Broadcast Standard equipment. Too many to list!

[JJJeffries]

The Murata Super tweeters are singing as I make this first judgement call on them.

They really open up the sound stage. I am hearing lower mids up through the spectrum I never heard before.

I can almost reach out and touch Ole Blue Eyes. Every type of music I have thrown at them is spectacular. At $1825 it better be.

Wonder what they would do for the cornerhorns. Mmm! Very interesting.

Will I go out and order a pair. Will keep you posted. First honest impression is: The Heresy 2s have opened up and are playing their finest to date.

Best,

Craig

Broadcast Standard Equipment. Too numerous to mention!

[JJJeffries]

This is one sweet post I am typing right now. The owner of the super tweeters was a huge fan of Stan Kenton and when he saw my LP collection he went crazy.

Back in the 1970s I did some PR for Mr. Kenton in Boston being a Broadcast Journalist and in addition to a nice check he shipped me three complete sets of all his LPs over 100 in each set.

The super tweeter owner asked what I would sell the Kenton collection for and I said trade them for the tweeters. The collection is worth around $2k and he agreed.

I am listening right now to Arthur Prysock with the Basie band backing him up and those Murata Super Tweeters are so sweet.

Good things do indeed happen once in a while.

Best,

Craig

Broadcast Standard Equipment. Too numerous to mention!

[John Warren]

I've provided the manufacturers data sheet on this device below.

The resonance frequency of the moving mass, based on the impedance plot, is ~27kHz. Below resonance the piezo element is working against the suspension that supports it within the structure and above it is working against the mass of the element. Above Fs in a dynamic moving coil loudspeaker system the acceleration of the cone is independent of frequency (a requirement for linear response). Below Fs, the acceleration depends of frequency and non-linearities dominate the output and output drops as a function of it.

The point is that examination of the impedance and SPL vs. frequency shows that this tweeter, in the audible operating range, has a sensitivity below Fs of ~80dB/W/m, very low and certainly a problem when one attampts to integrate this unit with a Heresy. Above Fs, the sensitivity improves but we are now in the range where only a few dogs can here it so what's the point(?).

Also, a bandwidth of 15-100kHz is claimed suggesting that the horn throat diameter, which dictates the HF bandwidth limit, is about .02 inches (wavelength of 100kHz) in diameter, i.e. a pinhole?

[John Warren]

PDF of tweeter is provided>>>>>>>>>

[STL]

On 4/26/2004 8:22:17 PM John Warren wrote:

The resonance frequency of the moving mass, based on the impedance plot, is ~27kHz.

...

Above Fs, the sensitivity improves but we are now in the range where only a few dogs can here it so what's the point(?).

I totally agree. I myself find it quite amazing that people will fall for these "snake oil" products.

[John Warren]

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On 4/27/2004 7:23:00 AM STL wrote:

I totally agree. I myself find it quite amazing that people will fall for these "snake oil" products.

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A super tweeter that claims 15kHz to 30kHz would, in principle, sound "better" than a unit with a bandwidth of 15-25kHz (all things being equal) simply because bandwith is a measure of the transient behavior of a transducer. So, to some extent, what we cannot hear "does" provide some insight into the performance in the range that is audible.

What I don't like about this unit is that the resonance frequency is well into the supposed operating bandwidth of the device.

Below Fs the system behaves differently than above it. Looking at the sensitivity plot provided in the PDF, the output below Fs is consistent with the physics associated with stiffness-controlled behavior, i.e. the output is a function of frequency and drops when frequency drops.

Piezos are not linear devices. Dynamic loudspeakers are not perfect either but they do a much better job at "approaching linearity" above Fs. In this region, F=ma is the rule. Since the moving mass is (essentially) constant, the acceleration is determined soley by the force of the motor structure which is F=i x B x L where i is the current in the coil, B is the magnetic flux in the gap and L is the length of wire in the coil. If the magnet field in the gap is axially symmetric and uniform circumferentially then the driver will provide decent response. Easier said then done but the problem is tractable.