Gamma Horn loaded Ribbon VLD-13 - Application Advice Needed

[icefox]

Hi there,

Recently acquired a pair of the caption hornloaded ribbon used. THere is very little info on this beast.

For picture of it, see http://www.audiocircle.com/circles/m...view_photo.php

I want to mate this with a pair of full range Tannoy Silver 15" as "Supertweeter" . Here is my questions,

1. Does the speaker come with any crossover at all?
2. If not, how can I calculate the kind of capacitor required at a desirable frequency.
3. As I want the unit playing the role of super tweeter, I assume I need a +16000 Hz cross over point. What's your opinion on crossover point for fullranger like Tannoy.

Thanks a lot for your help.

iCefoX

[icefox]

Does anyone know the different between Gamma VLD-12 and VLD-13?

[PMik]

I have used "Stripped" Gamma VLD-12 as super-tweeter for Magneplanar MG-II with great result
(80Hz/6dB active filter, passive 1000Hz 6dB/oct.)
Audio Pro 2B50 mod. active subwoofer was used below 80Hz

Crossover freq. for the Gamma's was 13.200Hz/6dB (1.5µF/250V-) and no lowpass filter used for the maggie tweeters.

The power limit for the Gamma tweeter when supplied with a clean (non-clipped) signal is for me unknown!

A heavy mod. Musical Fidelity P270 with 5 pairs of MOS-FETs messured to deliver aprox. 225w/8Ohm RMS....didnt harm the Gamma's when the clean and massive power-amp made the "Maggie" bass panels hit the grills/magnets.

For instance a "brute" clipping amp like the 100watt/8Ohm Quad 405-II will burn the Gamma alu-strip ever so fast if the amp is driven hard....you will be noticed by crakling sound and next a fine dence white smoke from the tweeters............tried that one


I think the difference betwin VLD-12 and VLD-13 is/could be lack of cobolt for the magnet in VLD-13.
please ....correct me if im am wrong

[Tim Moorman]

The Tannoys are fairly efficient so you should not need a lot of power - a few watts. Good tube amp or class a ss would do well.

Any idea what the Fs is on the ribbon? Efficiency? 8 ohm? Power handling?

I would start high with say a .47 uf capacitor in series with the + on the tweeter, then listen with low power and the Tannoys. You will hear very little in "tone", just more ambiance or added "air". At this frequency the effect is fairly subtle, though noticeable.

Remember, when using the single cap in series, you will still have significant output well below the crossover point due to the shallow slope (6dB/octave) of roll-off. As you increase the capacitor size you allow more lower frequencies through, and more overlap with the Tannoys. And as you near the free air resonance of the ribbon, there is usually substantial distortion first, then nothing. The ribbon fails. Particularly, when high power is used, or the amp is clipped that's feeding them. Fortunately, there is so little going on this high that power needed is usually minimal.

If the ribbon plays too loud, then you will have to add resistance to pad down the output. This will also provide a bit more protection for the device. Fostex makes a nice "L" pad if output adjustment is desired.

Tim

[Tim Moorman]

I found a bit more info on the ribbon at a Swedish site, but not entirely sure of the accuracy.

Frequency Range - 2400 - 40K Hz.

Assume FS is close to lower limit.

Power Handling - 60 watts at 4000 Hz.

Sensitivity - 94 dB/watt/meter.

Impedence - 8 ohm.

The Tannoy Silver 15" are about 92 dB, so some attenuation may be needed on the ribbon.

Also, the ribbon has a low enough Fs and high enough power handling to use a larger capacitor, so you may want to experiment with values from 1.0 uF to 1.5 uF.

Tim

[PMik]

The Swedish Gamma agent shows data which cant be used for evaluate which filter or use is best for the VLD-13

I cant support the advice to start with 41.500 Hz as suggested crossover freq..............thats ultrasonic soundwaves
go for 1µF (-3dB/20KHz) which believe me will be hardly audible


Gamma did in 70's sell 2 and 3 way speakers

the showed data is taken from a 1975 Hi-Fi yearbook.

Gamma Classic:
Freq. +- 4dB 45-30.000Hz
Freq. +4/-8 dB 40-35.000Hz
3.5watt/96dB SPL
30Watt RMS power
55Watt music power
8 Ohm
Bassreflex Cab. volume 26L.
Tweeter: VLD-12
Bass: GAMMA BBK 200
Filter: 3000Hz 12/18 dB



Gamma Monitor:

Freq. +- 4dB 35-30.000Hz
Freq. +4/-8 dB 30-35.000Hz
2.5watt/96dB SPL
50Watt RMS power
85Watt music power
8 Ohm
Bassreflex Cab. volume 57L.
units
Tweeter: VLD-12
Mid: BK 138-A
Bass: 12" LA-1231
Filter: 650/3500Hz 12/12/18dB (no LP-filter for the mid-range unit)

[PMik]

I think i said somthing about using the Gamma's with a 1.5µF...didnt i, didnt i

[Tim Moorman]

Pmik,

Better to error on the safe side with ribbons by using a high crossover. They have a tendency to fail, although this one seems fairly stout (60 watts). Can find very little on them. Where are (were) they made?

The Tannoys may or may not match up well with your crossover point for the Maggie's. Different breed entirely, but maybe icefox will get lucky.

Your Gamma data says 96 dB for the VLD-12, the Swedish site says 94 dB for the 13. Close, but a different model. What makes you believe one is bad information, or the other good? Besides, they both could be 94 or 96 dB, but at what frequency? Measurements are needed, reliable frequency response plots, that sort of thing, if one were crossing at 3K Hz.

I have a set of open baffles with a Fostex horn run with only a .47uF capacitor as the crossover. Sounds good mated to a full range driver similar to the Tannoy. Adds just enough "air". Some tweeter roll-off is a good thing when paired with a less efficient midrange, and the slope is so gentle there is still noticeable output this low (14K- 16K Hz). Matter of taste, really.

Tim

[PMik]

You got a point and the data you refere to maybe shows,
its lack of (expencive) Cobolt thats missing in VLD-13's which gives less flux, less sensitivity....

I read an article in the late 80's about growing world pricesresulted in less speaker-units with ALNICO magnets..........im pretty sure..but many years has gone since

Its rather difficualt for me to express exactly how easy and flawless the use of Gamma VLD's are, its build and fine sound quality not to far behind the Decca
i have use my Gamma VLD's (with and without the horn) for more than ten years

I have also tried to use my Gamma with my pair of Tannoy T-165 (10" dual concentric 1978) speakers and i would expect Firefox to end up using his VLD-13 with par. 1.0 + 0,22µF capacitors for a crossover point of aprox 16KHz.

For the moment i use my "stripped" Gammas with a pair of Dali Dacapo which is a 2way hybrid speaker (8" bass-unit + 40"x1" ribbon tweeter) and my always faithful Audiopro Subwoofer

Cheers

[PMik]

LOL!!!
i renamed Icefox...........to firefox


sry for that