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Dave A

KP-904 questions, crackle in HF

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I have some KP-904's with 510 horns and B&C DE75 drivers. There is a crackle that comes out of the 510's with the stock crossovers in some music and less when I bi-amp these with recommended PEQ cinema settings. Now there was still some and while fiddling with the xilica settings I notice the 4 and 5khz eq at -2db seems to tame a lot of that. Not a whiz at using REW or TrueRTA and a UMike to analyze this so still guessing at what will work. For those of you who have been here before what are all the settings you have used?  Also would a simple rack mount two channel EQ solve this with the passive crossover sets?

 

  The other thing I am wondering about besides the EQ aspect is if these were made to work behind screens and thus a little hot what could I change on the crossover to tame the HF down and possibly reduce the crackle?

 

  The third thing is I have begun to wonder if my music files have been hurt with too much tinkering through Audacity and considering starting over from original source material. Some of these just sound a bit un-natural now and I have to say I really hope Chris A can spend some time in Hope with Audacity best practices.

 

  As an aside here looking into the drivers to see about setting the diaphragms up with a frequency sweep generator and note what looks visually to be the same phase plug as is in the 1132's. I wonder if the latest B&C DE75 drivers Klipsch uses have also been switched out to the new SLA build phase plugs.

 

  Oh forgot to mention that the xilica crossover frequencies I am using are HF 900hz and LF 920hz which is what the Klipsch literature said but that seems a bit high to me.

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Anybody with this setup care to answer?

  • Haha 1

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Hello, I don't have the 904, but that won't stop my keyboard from spinning "the wheel of thought"... with one question, that being, "Ground", of which the "crackle" seems to unfold, more related to location perhaps, since I'm sure there is no dust or loose nuts and bolt's within the confines...

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Get you some "snap", and "pop", and some marshmallow to go with them!  Makes a sticky mess in the pan, but momma'l clean that up!

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Everything is checked and no it is not the Xilica since other speakers work just fine. I figure it is A, needs better settings in the Xilica or B, the crossover is set up to work through a movie screen and as a result is 510 is hot to accomplish this.

 

  Looking for someone who has worked with this setup and has practical hands on knowledge of what to do and is familiar with this problem.

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@Dave A none of the 904's  I've owned have had a crackle sound to them. I found them to be hot around 3khz to my ears so I used an old school analog 2 channel eq to tame them. Sorry I can't be of more help.

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4 to 5 khz seemed  to tame the majority of it but I have not spent much time fiddling either. Hoping to learn REW and approach this kind of problem the right way. Perhaps hot is a better word than crackly. 

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5 minutes ago, Dave A said:

4 to 5 khz seemed  to tame the majority of it but I have not spent much time fiddling either. Hoping to learn REW and approach this kind of problem the right way. Perhaps hot is a better word than crackly. 

Me too I think we will both be in a better place after Chris A's class in April.

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Isn't Claude coming to your house?  I would think he can help identify the issue.  

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Yes, tomorrow, but instead of staying here two to three days it is now just one so I am not sure what all we will get done.

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2 hours ago, Dave A said:

Yes, tomorrow, but instead of staying here two to three days it is now just one so I am not sure what all we will get done.

keep us posted whenever you put a finger on the problem -

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Will do. The KPT-456's sounded fabulous with crossovers and needed no tinkering. Different horn and that lovely 1132 driver on them though. These 904's are a different animal.

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15 hours ago, Dave A said:

Yes, tomorrow, but instead of staying here two to three days it is now just one so I am not sure what all we will get done.

Is he saving his vacation days for April?  :D

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I've noticed it too but can't isolate it...

 

The high Q value and distance from the crossover point make me think it is whatever is causing  "PEQ2: 3.7kHz  Q: 5 Gain: -3db" in the active settings.

 

Surprisingly the KPT-Grand HF-T (510/69) similarly requires

"PEQ4: 3.5kHz  Q: 7 Gain: -2db"

"PEQ2: 3.8kHz  Q: 5 Gain: -3db"

in certain applications despite being crossed at roughly 4kHz in those applications

 

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Actually the 335 has an LCR in the MF circuit that is centered at about 3650kHz as well...

 

I wonder if Roy would ever consider supplying 904 owners an LCR design, that could be inserted between the supplied passive network and driver, that could be used to tame this issue?

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I have had the 904's for several years. They came with 510 horns and BEC DE75 drivers. They were too hot for what I liked so a forum friend of mine made me some jumpers to tone them down and it worked well. Later I went to the 402 horns with pAudio BM-750 drivers and have enjoyed them with no issues.

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On 1/21/2020 at 9:33 AM, Pete H said:

Is he saving his vacation days for April?  :D

Don't know  you will have to ask him. SWAG never came up in topic except to contemplate the faces of attendees when they heard the S-MWM's

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22 hours ago, CANT said:

I've noticed it too but can't isolate it...

 

The high Q value and distance from the crossover point make me think it is whatever is causing  "PEQ2: 3.7kHz  Q: 5 Gain: -3db" in the active settings.

 

Surprisingly the KPT-Grand HF-T (510/69) similarly requires

"PEQ4: 3.5kHz  Q: 7 Gain: -2db"

"PEQ2: 3.8kHz  Q: 5 Gain: -3db"

in certain applications despite being crossed at roughly 4kHz in those applications

 

I think this is the right direction too when I have time to fiddle around.

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