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Modifying AA crossover to cross at 4500hz


geoff.
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Was just reading another post and noticed @Dave MacKay asking a question that has crossed (no pun intended) my mind more than a few times now.

 

EVERYTHING Klipsch now designs crosses lower to the tweeter.

 

The latest La Scalas have crossed at 4500hz for two generations now.

 

Since the AA seems to hold it’s own amongst the competition how would it be modified to cross at 4500hz?

 

Has anyone tried this? 

 

And if so how were the results?

 

 

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I build all of my Heritage crossovers to the AA configuration, with very good caps, new coils, new autotransformers.  I listened to the Crites A4500 a while back, and gave it about two weeks.  I much prefer the AA for the tonal balance (admittedly with my somewhat senior ears.....)

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12 minutes ago, JerryC said:

Do you find it helpful (or not) to test the crossovers for match. This would require an oscilloscope and signal generator. Or is choosing your component tolerance enough?

Using high quality components with factory specified tolerances is good for me.

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58 minutes ago, JerryC said:

Do you find it helpful (or not) to test the crossovers for match. This would require an oscilloscope and signal generator. Or is choosing your component tolerance enough?

 

I use REW.   I don't have an AL-X crossover, but the high pass of the ALK ES5800 is almost identical.  Here is a plot of the voltage across a real K-77M.

Still can't figure out why REW gets cranky at the lower SPL.

 

 

Screenshot (77).png

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1 hour ago, geoff. said:

EVERYTHING Klipsch now designs crosses lower to the tweeter.

 

The latest La Scalas have crossed at 4500hz for two generations now.

With the soldered lug 55v or A55-g mid drivers it really isn't needed and risks damaging the stock tweeter from what I understand. This would be a good mod for those using a stock single phase plug 55v and aftermarket tweeter like the CT-120 that can easily handle the lower crossover point.

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I cannot speak for anyone else, but the thought of using the stock K-77 in anything this century is as far from the plan as it gets.

 

Even the original CT-125 drop-in tweeter option sounded nicer to me. And now with the CT-120 and the SMAHL as options it only gets better. 

 

I was thoroughly impressed with the Crites A/4500 crossovers and always wondered what capacitor changes would be needed to be made to the AA crossover, for starters.

 

I am surprised nobody else has tried this yet, or was it that bad, lol?

 

 

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7 minutes ago, geoff. said:

I was thoroughly impressed with the Crites A/4500 crossovers and always wondered what capacitor changes would be needed to be made to the AA crossover, for starters.

 

I am surprised nobody else has tried this yet, or was it that bad, lol?

 

 

Looking at the pictures on Crites site the type "A" has a single 13uf and 2uf cap-- the type A/4500 has a single 13uf and 4uf cap but it also has the little coil from the AA? 

 

From what I understand the AA is pretty much the same thing as the A but with added tweeter protection, since you're running the 120's don't think you need that so you could probably just use / make a pair of A/4500's with what you have and a pair of 4uf caps.

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3 hours ago, geoff. said:

The latest La Scalas have crossed at 4500hz for two generations now.

 

Since the AA seems to hold it’s own amongst the competition how would it be modified to cross at 4500hz?

 

 

 

In order to use a modified AA at 4500Hz, you will need to use a different tweeter than the K77, but you probably already know that. Just FYI. 

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15 minutes ago, Curious_George said:

 

In order to use a modified AA at 4500Hz, you will need to use a different tweeter than the K77,

 the klipsch AK4-AK5 4500Hz crossovers use the K-77  tweeter   , why would the AA be any different with the EV-T35 or the EV-T-350  or  the EV tweeters that use the same diaphragm -

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2 hours ago, 000 said:

@Dave MacKay    easy answer ,go active with the miniDSP 2x4 HD-  it's also a lot cheaper

I didn't think that I could run a DSP with my setup. I would benefit from some education about how they are employed.

 

I drive my La Scalas with a Yamaha R-N803 receiver.

 

My understanding is that, to use a DSP, I'd need to replace my receiver with a separate input stage (tying together a streamer, etc.) and a separate amp. In fact, I thought I might need  as many as 3 amps. The signal would be sent from the input to the DSP. The DSP would then go into the amps (one for each pair of tweeters, squawkers, and woofers). The existing networks would be disconnected. The exercise seemed too expensive and disruptive to be attractive.

 

Please correct me where my understanding is faulty.

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33 minutes ago, Curious_George said:

The "A" crossover is one capacitor, 6dB/octave.

 

The "AA" crossover is two caps & coil, 18dB/octave + back to back Zener diodes for "more" tweeter protection. 

So from what I gather looking at these three crossovers the A, A/4500 and the AA I would have to guess to get the AA down to 4500 like the A/4500 one would need to replace both of the 2uf caps in each of the AA's with 4uf caps-- 

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6 minutes ago, Dave MacKay said:

I didn't think that I could run a DSP with my setup. I would benefit from some education about how they are employed.

 

I drive my La Scalas with a Yamaha R-N803 receiver.

 

My understanding is that, to use a DSP, I'd need to replace my receiver with a separate input stage (tying together a streamer, etc.) and a separate amp. In fact, I thought I might need  as many as 3 amps. The signal would be sent from the input to the DSP. The DSP would then go into the amps (one for each pair of tweeters, squawkers, and woofers). The existing networks would be disconnected. The exercise seemed too expensive and disruptive to be attractive.

 

Please correct me where my understanding is faulty.

You are correct.  It's not cheaper nor easy.

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3 minutes ago, jjptkd said:

So from what I gather looking at these three crossovers the A, A/4500 and the AA I would have to guess to get the AA down to 4500 like the A/4500 one would need to replace both of the 2uf caps in each of the AA's with 4uf caps-- 

 

Switch the two 2uF's for two 4uF's and add the 500uH coil.

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