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Frequency responce slope question [message #49651] Wed, 21 June 2006 13:37 Go to next message
Garland is currently offline  Garland
Messages: 269
Registered: May 2009
Grand Master
Hi guys, I posed this question over on the Bottlehead forum but thought I'd ask Wayne and anyone else here. The problem I have is not new and not really a problem except when I listen at louder levels which is fairly often. I'm looking for a way to cool the treble a bit and was wondering if there was a way to do this gradually with a constant slope through out the compression driver's range. Here is my question as posed on the B'head forum:

"I recall reading a few years back about some way to affect the responce curve of an amplifier to compensate for room/ loudspeaker characteristics. A quick search turned up nothing. What I was hoping to try was a way to tame the upward sounding tilt in my system's responce without adding room treatments (Wife says no stuff). Any ideas? I guess I'm looking for a very long slow roll-off of the highs. (Amps are Paramours, speaks are Pi Theater 4: 15" bass reflex/ horn loaded compression driver.)"


What about doing this in the crossover, ie. the tweeter compensation circuit?

Thanks for any tips!

G.


Re: Frequency response slope question [message #49652 is a reply to message #49651] Wed, 21 June 2006 15:03 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18786
Registered: January 2001
Illuminati (33rd Degree)

If you're looking for a generic answer, an easy way to rolloff highs is with shunt capacitance. Change the value of capacitance to affect where it starts; Resistance can be placed in series with the cap to reduce the amount shunted.

If this is specifically related to π Speakers, as you've indicated you want to do this to a Theater four π, then you'll want to modify the values in the tweeter compensation circuit. Remove the bypass capacitor and possibly increase attenuation. The Theater four π uses a 10dB attenuator; Change the values to 12dB, 14dB or whatever desired. There's a chart showing what resistors to use in the crossover document.


Re: Frequency responce slope question [message #49654 is a reply to message #49651] Wed, 21 June 2006 17:36 Go to previous messageGo to next message
GarMan is currently offline  GarMan
Messages: 960
Registered: May 2009
Illuminati (2nd Degree)
Garland. I read your first paragraph several times and wonder if it's not an issue with different compression rates between woofer and drivers. It sounds like the treble is hot as volume goes up. I've experienced the same thing with high volumes and wonder if the woofer is compressing before tweeter.

Re: Frequency responce slope question [message #49656 is a reply to message #49651] Thu, 22 June 2006 02:29 Go to previous message
dB is currently offline  dB
Messages: 234
Registered: May 2009
Master
Hi,
After testing various configurations values for the attenuation (confirm with Wayne) you can also use a 3 point attenuator selector as in the old times or a continuos L-Pad knob from many manufactures.
VISATON LC 95 100W, Monacor, Parts Express. (http://www.partsexpress.com/projectshowcase/d2w/2-Mann-DW2.jpg)
Your problem might be different if you get a crazy peak like the one's from inductive resistors. But you might have good one's already (non inductive). Did you checked the voltage on the cap and the wattage, is it high enough in the resistors? If not they will get hot.
Keep us informed.
Best Regards


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