Some speaker driver measurements...

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HiFiCompass

HiFiCompass

Member
Joined 2018
Pida said:
Hificompass: for TW29BN and DN I noticed H5 peak at 5kHz. For DN it is quite low, BN is quite disappointing in that regard. TW29R does not show that behavior. It seems related to damping of the chamber or arrangement behind the dome.
Click to expand...

Yes, I saw it too, but I think the damping is the same in the both tweeters.
I faced up with the same problem when was working with ScanSpeak D2908/7140:

ScanSpeak D2908/714000 | HiFiCompass - всё для акустических систем и не только

In that time I tried different chambers and damping but nothing had helped and I postponed this work for future.
 
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IslandPink

Member
Joined 2005
Very interesting and useful information, thanks HiFiCompass.
It was good to see some data on the very nice Fostex FX120 drivers - including an impedance curve with an accurate scale.
I have one question - are you happy with the Le results shown from your software, in the data boxes by the impedance graph ?
I ask because it shows 0.67mH for the FX120. My understanding ( which may be incorrect ) is that the rising impedance from 1kHz into the HF would be mainly described by Z(f) = Re + 2Pif(Le)
If I solve for Le based on the values on that curve, I get approx. 0.2mH.
This seems reasonable for that sort of small FR driver, I'd expect 0.67mH to be more associated with bass or mid-bass drivers.
 
HiFiCompass

HiFiCompass

Member
Joined 2018
IslandPink said:
Very interesting and useful information, thanks HiFiCompass.
It was good to see some data on the very nice Fostex FX120 drivers - including an impedance curve with an accurate scale.
I have one question - are you happy with the Le results shown from your software, in the data boxes by the impedance graph ?
I ask because it shows 0.67mH for the FX120. My understanding ( which may be incorrect ) is that the rising impedance from 1kHz into the HF would be mainly described by Z(f) = Re + 2Pif(Le)
If I solve for Le based on the values on that curve, I get approx. 0.2mH.
This seems reasonable for that sort of small FR driver, I'd expect 0.67mH to be more associated with bass or mid-bass drivers.
Click to expand...
I know the problem with measuring of a driver inductance using WT3 tester. I tried different frequencies - 1 kHz and 10 kHz, and was never satisfied with measurements. I'm sorry. So, I do recommend to everyone not to pay a much attention to that figures in my impedance measurments data. Fortunately, the inductance is not very useful parameter and you can learn about a motor quality just looking at the behavior of the impedance curve.
 
JasonPJackson

JasonPJackson

Member
Joined 2014
Pida said:
Hificompass: for TW29BN and DN I noticed H5 peak at 5kHz. For DN it is quite low, BN is quite disappointing in that regard. TW29R does not show that behavior. It seems related to damping of the chamber or arrangement behind the dome.
Click to expand...
I noticed that too. It may be an "echo" that has been described in this forum somewhere that relates to the resonance at the top affecting the performance further down. SS Beryllium tweeters are smaller in diameter than SB acoustics which is probably why SS don't have it. You can see this echo effect in other drivers. BTW, These are an extraordinarily interesting set of measurements to look at. It pays to learn to read them correctly however. My conclusions have changed markedly after being more careful with what I'm looking at. Further, application and the resulting changes in the conditions means different measurements.
 
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