VIFA tweeter response

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Mr. “whatamIdoinwron” made some new measurements on a brand new ScanSpeak 9700 driver which was already on the shelf. Using the same and exact setup as before.
The (no-go) Current Feedback amplifier, the “non calibrated” microphone and feedback loop was used even the “sabotaging” passive preamp.
Attached is the frequency response of the Scanspeak 9700 tweeter.

It roughly matches the data that Scanspeak provides for this SS-9700 tweeter.
No roll-off beyond 10kHz as seen on the Vifa tweeter.
The only and valid conclusion: the used setup works sufficient, the Vifa XT tweeter fails for unknown reasons.

Thanks for all your contributions.
 

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  • Scanspeak 9700 respons 1m outside.png
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ICG

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Mr. “whatamIdoinwron” made some new measurements on a brand new ScanSpeak 9700 driver which was already on the shelf. Using the same and exact setup as before.
The (no-go) Current Feedback amplifier, the “non calibrated” microphone and feedback loop was used even the “sabotaging” passive preamp.
Attached is the frequency response of the Scanspeak 9700 tweeter.

It roughly matches the data that Scanspeak provides for this SS-9700 tweeter.
No roll-off beyond 10kHz as seen on the Vifa tweeter.
The only and valid conclusion: the used setup works sufficient, the Vifa XT tweeter fails for unknown reasons.

What is wrong with you? Since when was the "there's no world hunger because I've just eaten"-Logic valid? :rolleyes: Firstly, I did NOT say your mic isn't calibrated. I said your SETUP isn't. That includes also items besides the microphone. Secondly, the SS-9700 is 8 ohm and the VIFA XT25SC30-04 is 4 Ohm. That's the best example why your setup is anything but NOT okay! If there's something wrong with the measurement at a 4 Ohm speaker and it's okay-ish with a 8 Ohm, then that's the most [insert f-word here] obvious sign the chain is not suited for the measurements! Even before that, the first thing which makes doubt on the seupt is the impulse response - there's no way it measures one time a positive and without any changes in the setup a negative first impulse.

Now look at the measurement of the ScanSpeak D2905/9700:

attachment.php


It dives already at 12kHz, where at your measurement it loses only 2dB at 20kHz, the SS measurement says it's losing 6dB! And compared with the nosedive of the XT tweeter (keep in mind, the XT got an impedance of ~3,3-3,5 Ohm) and the normal behaviour of the SS (7 Ohm at the top end), that looks extremely like the behaviour of a class D amplifier. This is how a class-d amp behaves:

amp-class-f7.gif


The behaviour comes from the output inductance, it can divert from that graph, mainly the curves stay the same/match bit different impedances but the tendency 'response changes with the impedance' is the same. Do you want to know why your measurements fail or not? If yes, tell honestly which amp you are using for measurements (inc. model) and list what you are using, every single component. If you are not interested, then say so and save everyones time and effort.
 

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Whatever the quality of the measurements, if the gear used to make them is the same that used for listening to music, it seems that the SS will sound better with it than the Vifa, whatever the reason for the rolled off response...

And btw, there is a huge squad of rolled off highs followers too that might enjoy the Vifa measured response, and will praise the electronic set up able to deliver such a soft ( dark side dull rubbish...) performance...:D
 

ICG

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You can get a lot of drivers to sound good with the crossover handling it. If they don't get linear up to 20kHz that can be fine too and I did not say at any point anything about the quality or sound of the driver. The thing is though, if you are using a calibrated mic and get significant differences in measuring, then there is something wrong.

If the (mis-)behaviour changes with the driver impedance, then there's something very wrong and such measurements are completely useless. That's then not a problem in the mic path, that's a problem in the signal source side. Since the mic and everything after that cannot 'know' what impedance is in play, changed behaviour with the impedance can only be a problem of the amplifier.
 
I didn't know Sakuma measures with an triode amp. :rolleyes: Most tube amps are still linear with changing impedances. The requirements for a measuring amp aren't very high either and I'm surprised you don't seem to know them.

No, tube stuff is the least linear of all, poisonous stuff, not so much because of the vaccum involved, simply owing to the pesky iron needed, thanks god i finally got rid of all that jazz, and no Sakuma have no interest at all in measurements and calculations, you know simply quoting him, he just tries to get the phone number of the girl, simply a different way of making numbers...:D

The japanese way of making numbers, overlooking numbers, philosophical attitude beyond science, almost despising science... The anti occidental way of making science... And please dont answer that there is only one way of making science, i have no interest in borin calvinist religious wars of that kind...:p
 
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ICG

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Joined 2007
No, tube stuff is the least linear of all, poisonous stuff, not so much because of the vaccum involved, simply owing to the pesky iron needed, thanks god i finally got rid of all that jazz

Well, any drop at the ends of the spectrum of a tube amp is less than the peak at higher impedances at class d amps. So I'd prefer a tube amp for measurement anytime over a class d one. But did you know there are also transformerless tube amps?
 
Well, any drop at the ends of the spectrum of a tube amp is less than the peak at higher impedances at class d amps. So I'd prefer a tube amp for measurement anytime over a class d one. But did you know there are also transformerless tube amps?

Yes, and the HT involved always frightened me, at leat i felt somewhat more secure under OT shelter...

Btw, i got married with T-amps years ago, and my only concern is the dc offset/ bridge mode for measuremts..
 
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