A PC, a decent soundcard and a measurement program will do the trick as well.
A scope is always a nice piece of equipment, but you may prefer to take your time purchasing/finding the right one.
You may download a free trial-version of "HobbyBox" for instance:
http://www.audio-software.de/downloads.html
Regards
Charles
Hi Charles,
Downloaded HobbyBox, made a cable and got my first own impedance measurement
Impedance (black) and phase (blue) http://www.jonkers.net/audio/impedantiecurve.jpg
TS Parameters http://www.jonkers.net/audio/ts.jpg
Peak is measured at 1566,78hz 36,6 ohm.
Now we can start doing something about that peak?
Ralph
Downloaded HobbyBox, made a cable and got my first own impedance measurement
Impedance (black) and phase (blue) http://www.jonkers.net/audio/impedantiecurve.jpg
TS Parameters http://www.jonkers.net/audio/ts.jpg
Peak is measured at 1566,78hz 36,6 ohm.
Now we can start doing something about that peak?
Ralph
Entering the data in a online calculator gives me this: http://www.jonkers.net/audio/notch.jpg
Am I on the right track here?
Am I on the right track here?
Hi Ralph
The idea of treating the impedance-rise as if it was a tweeter's fundamental resonance is quite a cool one !!
We do not have the same situation here though. Only a mathematical analysis could give an exact answer.
But my guess (and it is only a guess) tells me that you should try it with the values that you got and measure again (and of course listen). Since you have two identical speakers you could even do an easy A/B comparison.
Regards
Charles
BTW: Forgot to mention: You don't need a fancy, extremely low Rdc, coil to do this. You can simply take it's DC resistance into account and make the "real" resistor smaller!
The idea of treating the impedance-rise as if it was a tweeter's fundamental resonance is quite a cool one !!
We do not have the same situation here though. Only a mathematical analysis could give an exact answer.
But my guess (and it is only a guess) tells me that you should try it with the values that you got and measure again (and of course listen). Since you have two identical speakers you could even do an easy A/B comparison.
Regards
Charles
BTW: Forgot to mention: You don't need a fancy, extremely low Rdc, coil to do this. You can simply take it's DC resistance into account and make the "real" resistor smaller!
Ralph said:
i dont think so. many years ago i was also working on my system (MTM using 8546 adn 9900). I have the same harshness. TO kill this i was adviased to add a notch filter. assuming Fs = 500Hz (from SS website) i got a parallel filter like you have sown however R=6.5ohms, C=64uf, and L=1.71mh. This filter did not help much so i removed it.
then i was adviased to add a 10 ohm resistor in parallel with the tweeter. the speaker would "shout" at mid levels but was ok at low levels. to reudce this I was told to increase the parallel resistor to 20 ohms. the "shouting" effect it still there but at higher volume levels. I would like to eliminate it some day.
In any case I am now looking at rebuilding this system so that it becomes a Push Push TL yet the box should have curved sides and no parallel surfaces. I have not got a viable box idea to incorporate all these features so my system continues as it is.
My first assumprions were:
Tweeter too loud or too much thd from tweeter. The latter should not be a problem with 2.8. kHz cutoff approx.
When he wrote that he uses an SET amp I wasn't convinced of the too loud tweeter anmore. The high output rsistance of an SET would give a frequency-dependant voltage divider together with the speaker's impedance.
Even if this isn't the case, it is always a good idea to achieve a "flat impedance" for mid- and high frequencies.
Regards
Charles
Tweeter too loud or too much thd from tweeter. The latter should not be a problem with 2.8. kHz cutoff approx.
When he wrote that he uses an SET amp I wasn't convinced of the too loud tweeter anmore. The high output rsistance of an SET would give a frequency-dependant voltage divider together with the speaker's impedance.
Even if this isn't the case, it is always a good idea to achieve a "flat impedance" for mid- and high frequencies.
Regards
Charles
I did the first experiments with my LCR filter like the one on the link http://www.jonkers.net/audio/notch.jpg. I used components with values closest to the calculated ones. Got good (measurement) results, the peak around 1K5 is completely gone: http://www.jonkers.net/audio/correctie.jpg Black is without, red is with correction.
So far so good. Than I hooked them up to my amplifier. Gone were the high frequencies Sounded very very dulll... And I smelled something burning, or was that my imagination .... so I switched it off right away. I'm very curious what this filter does to the frequence response and cross over points, but got no means to measure it....
Ralph
So far so good. Than I hooked them up to my amplifier. Gone were the high frequencies
Sounded very very dulll... And I smelled something burning, or was that my imagination .... so I switched it off right away. I'm very curious what this filter does to the frequence response and cross over points, but got no means to measure it....Ralph
Ralph said:
Ralph,
Without going into a depth of discussion about the ways in witch the electrical resonators kill sound I would propose you to pay attention to following…
There is a differents between harshness and excessive amount of HF. The excessive amount of HF (or the forwardness) could be eliminated by decreasing your tweeter’s dB-output. However, the “harshness” will not be “fixed” by this. You might try “softening” of your 3.9uF cap or use any other methods… on the other hand take under consideration that this HF harshness in very many cases derives from the nastiness in the electric lines. I do not know how in Netherlands but in US during summer 95% of all so-called High-end systems do have this harshness at much higher level then during winter. Be advised that any conditionings, regenerations or filtering are not really affective to fix the problem. Monitor the presents of this “harshness” during a day and during the different temperature conditions (more or less stress to the power lines by air-conditioners) and you might find the source of your problem.
Rgs,
Romy the Cat
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