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9k Hz


Schu

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K55X:

Didn't they eliminate that 9K bounce back when they started crossing over at 4.5K?  I don't know about the La Scala, but in the Khorn, in about 2002, or so, they started rolling off the K55X at about 4.5K, at 12 dB per octave, so at 9K the response through the K55X would be about 12 dB lower than it is in the c1982 graph @JohnA posted, wouldn't it ?   I believe, previously, there was no K55 roll off at all.

 

K77F:

In my room, at about 13 feet away, the K77F doesn't seem to have a peak at 9K. 

image.png.d752db2aa0cca77f4d5abded614fafcd.png

5 dB vertical divisions

 

 

 

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That is isnteresting... indeed it's a 55x.

 

It's fairly universal no matter what I am listening to... although some individual songs that region goes fairly flat... but it's rare.

I am pretty sure it's NOT a room mode and unrelated to amplification because both of those variables can be changed at will with little affect.

 

I am not really sure it's even audible because the region is very narrow and definetely contained between 9-10k.

 

It's the La Scala AK4 XO I think. (Maybe it's the AL4?)

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3 hours ago, Deang said:

So, that tone is being generated through a tablet, right?

 

Some of the older spring loaded K-55s had "the problem", not all of them.

 

More of a K-77 problem than a squawker problem, imho.

 the tone/tune is being generated independent of the tablet D... freestanding handheld.

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  Looks like you have sold your original LS ii. Guess that eliminates the small change in the crossover. 

  My first thought is it is a resonance in the midrange horn. But that is also the second harmonic of the crossover point between the K-55 and K-77. High order crossovers can ring. 

  If I understand the graphical display, there is a peak at 13.5 KHz. Which is the 3rd harmonic. That makes me think it is the high pass to the tweeter causing this.

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Oh sorry... yes, the original LSiis are long gone. The scale of the waterfall, its not completely symmetrical from left to right. The scale from 10k to 20k is compressed (that's why there is such a step roll off) so that peak you see might be around 14-16k.

 

To me, purely a guess, it looks like a roll off crossover issue, but I guess it could definetely be a resonance issue also.

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  The high pass filter could be a “trap”. The capacitor and choke resonate and dump energy between them. The “quality” of the components plays a role here.

  ALK, Deano, BEC, and others are more qualified to offer suggestions. I usually damp capacitors electrically. But in this case a swamping resistor across the final choke might be the most effective. 

  Something like a 2 - 3K thick film, non-inductive in parallel with choke would identify if this is the issue. For the output coupling cap, a 0.536 ohm resistor in series with 0.1 ufd cap would be a start as a damper in parallel with the stock large  value film cap.

If I had a test rig I could check mine to see if they show the same peaks. I need an analyzer. 

  It would be easy to drop back panel and jumper in components to see if damping the choke, caps, or both effect the amplitudes and width of the anomalies. 

  BTW, I do not hear any misbehavior in my LS ii either. 

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10 hours ago, garyrc said:

K55X:

Didn't they eliminate that 9K bounce back when they started crossing over at 4.5K?  I don't know about the La Scala, but in the Khorn, in about 2002, or so, they started rolling off the K55X at about 4.5K, at 12 dB per octave, so at 9K the response through the K55X would be about 12 dB lower than it is in the c1982 graph @JohnA posted, wouldn't it ?   I believe, previously, there was no K55 roll off at all.

 

K77F:

In my room, at about 13 feet away, the K77F doesn't seem to have a peak at 9K. 

image.png.d752db2aa0cca77f4d5abded614fafcd.png

5 dB vertical divisions

 

 

 

 

The Atlas PD5-VH also shows the 9k bounce in its plane wave tube response.  Putting it on a horn like a K-400 that has some HF gain would exaggerate it.  So, I'm sure the K-55-X also has it.  Depending on the design, the AK4 xover would knock it down quite a bit.  If it is a 2nd order slope, the bounce should be down at least 20 dB. 

 

Nothing I have on K-77s shows a peak anywhere near 9k.  I'm sure the K-77-? Is not part of the problem.  Schu,  I would not place any faith in results obtained by a tablet or when using music as a source.   Your AL4 xovers should tame the squawkers bounce well.

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I understand its dynamic data as opposed to fixed... and therefore less ideal. However, it appears across the board of most all recordings... so I have been watching it for sometime now and thinking about it. I tried moving room items around, no affect. I tried multiple amp configurations, no affect. 

I am fairly certain it's NOT an instrument item because I can generate sound that clearly fills that 9k region... and like I had said, there are a handful of songs that also fill that region.

 

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