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Old 8th September 2003, 09:56 AM   #1
Ralph is offline Ralph  Netherlands
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Default Changing the filter to remove harshness

I'm looking for some help with my filter. Both units are ScanSpeak (18W8546 en D2904/9900). I really like the lows en low-mids, very detailed. The higer-mids and highs are a little on the forward/harsh-ish side of neutral. Most apparent with trumpets and female voices. Can someone advise me in a direction to change the filtering to remove this problem?

Thanks, Ralph
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Old 8th September 2003, 12:01 PM   #2
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I would start with the voltage divider, i.e. decreasing the tweeter level a little.

Regards

Charles
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Old 8th September 2003, 04:28 PM   #3
jan is offline jan  Europe
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It´s not the same question but with lots of answers about harshness.
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Old 8th September 2003, 04:29 PM   #4
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Removing harshness is done by implementing an impedance compensation network. A capacitor-resistor network in parallel with your tweeter. Ideally you have to measure the driver impedance response.
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Old 8th September 2003, 05:05 PM   #5
Ralph is offline Ralph  Netherlands
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Jan, thanks great info.

Quote:
Removing harshness is done by implementing an impedance compensation network. A capacitor-resistor network in parallel with your tweeter.
François, does this mean that I add a CR network to the existing 18R and use this formulas to calculate C and R:

R = Re + (Qes * Re / Qms)
C = 1 / (2 * pi * Fs * Qes * Re)

L = Qes * Rs / (2 * pi * Fs)


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Old 9th September 2003, 04:22 AM   #6
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From my experience, the harshness (and forwardness) comes from peaking in some frequency range that spans approximately 2 octaves (500Hz - 2kHz, 1kHz - 4kHz, for example). If you can source a graphic equalizer (or better a parametric one), you may try reducing a few DB in certain frequency regions to see if harshness is gone. Then, you can add certain impedance equalization (R-L-C) to certain parts of your crossover to obtain the result without using EQ.

Zobel network (R-C) will gradually drop SPL as frequency increase. While it could solve the harshness, it sometimes excessively dull the high frequency sound. Personally, I prefer maintaining flat SPL at high frequency (5kHz up) as I see that it's critical to the airiness of the sound.
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Old 9th September 2003, 05:16 AM   #7
Jay is offline Jay  Indonesia
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That's a Scan-Speak refference monitor, right? If you see the impedance response of this system, there is a bump at 2kHz. That's where the harshness come from, the frequencies of female vocals. Although there is a bump, this filter is phase linier, so I will prefer to improve the performance of the amplifier or source than changing the filter or adding a compensation notch filter (RLC, not zobel/RC). But adding a notch filter (in the input of the filter) seems to be the most promising and easier approach (I guess a pair of good notch filter around 2kHz will cost almost $50, cheap? Then go ahead )
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Old 9th September 2003, 07:39 AM   #8
Ralph is offline Ralph  Netherlands
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Jay,

Quote:
so I will prefer to improve the performance of the amplifier or source than changing the filter or adding a compensation notch filter (RLC, not zobel/RC).
That's a good one CDP and amplifier are more or less fixed and should do the trick.

Quote:
But adding a notch filter (in the input of the filter) seems to be the most promising and easier approach
Do I need measuring equipment for this? Don't suppose to go to the shop and ask for a 2K notch filter, am I right?
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Old 9th September 2003, 07:43 AM   #9
navin is offline navin  India
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Quote:
Originally posted by François
Removing harshness is done by implementing an impedance compensation network. A capacitor-resistor network in parallel with your tweeter. Ideally you have to measure the driver impedance response.
could u please draw this ckt?

Quote:
Originally posted by Jay
That's a Scan-Speak refference monitor, right? If you see the impedance response of this system, there is a bump at 2kHz. But adding a notch filter (in the input of the filter)
what sort of notch filter series or parallel.

i looked at the the XO and noticed that the XO is effectively a 3.9uf cap and a 0.82mh inductor. while the tweeter starts getting rolled of early, the 0.82 mh inductor means that the roll off is not fast enough. try reducing the 0.82mh to 0.7, or 0.6 or 0.5mh. see if that helps.

BTW should apply any solution to the 500Hz impedance peak or jus tleave this peak alone?
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Old 9th September 2003, 07:50 AM   #10
Ralph is offline Ralph  Netherlands
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This is the impedance of the speaker. I only need to address the 1K5 rise I guess.

I found this article on series notch filters
http://www.speakerbuilding.com/content/1041/
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