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Difference A & AA xovers


mic

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Al, I can't find the thread where you explained this, but what is it about a double terminated filter section like the AA that makes it "lossy". I believe you mentioned a mismatch in impedance, but what I want to know is where is the energy going?

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Dean,

The AA tweeter filter is simply a bad design. It has 2.87 dB loss at 17 Khz through the tweeter filter even with computer-perfect lossless parts. If you substitute the tweeter filter of my Universal ALK network the loss goes down to .58 dB. It should be zero though. This is power being absorbed by the squawker filter that is still in the circuit. The majority of the 2.87 dB loss is due to the mismatch generated by a tweeter filter that should operate between two terminations, that is, between an 8 ohms source and 8 Ohms load but is actually operating between and amp, which is about .2 Ohms and an 8 ohm termination (the tweeter). The fact is, it's not even a good filter at 8 ohms! It's some odd-ball impedance other then 8 Ohms! I forgot what it actually is.

Al K

I just went back and reverse engineered it. The AA tweeter filter is actually a 11.67 Ohm filter and cuts off at 4.76 Khz with a smooth response with that impedance at both ends.

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Hi all,

this evening I replaced the original ACR K 55 1" drivers with a pair of new EMINENCE EMD2002S-8 drivers and I have to say that there is now more detail and better resolution. Also they seem to be more dynamic ....

Problem is that the Eminence are a bit too loud so I have to put in place a L-Pad as well, I think.

However, for 66 (= $ 55)/pcs. it's a fairly good investment.

So I'll keep going on playing around hoping that the Tractrix Horns will arivve soon.

Yours,

Mic

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Hi,

You are right, indeed I took a look to the specs but I discovered at www.eckhorn.com that they use this drivers for the squawker but coupled to a wooden radial horn ....

But if I did not understand everything wrong regarding horns, the lowest frequency for a driver as specified in the data sheets does not take into account the horn coupled to it in reality.

That means that a certain driver could have a lower lowest frequency in function of the horn attached to it. Am I right ?

Any help is appreciated ....

Regards,

Mic

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"..the lowest frequency for a driver as specified in the data sheets does not take into account the horn coupled to it..."

It is true that drivers are rarely if ever measured with the exact horn one has in mind, however, they do measure the driver with a horn of some kind or a plane wave tube. The overall response of the driver will vary between different horns, but the low end response of the driver is pretty much set in stone. In this case, you have a driver whos -3dB point is at 1.2kHz, and then rapidly falls off. Coupling it to a horn crossed over at 400Hz won't change that much. I would imagine you now have quite a hole in your response between 500 and 1000. You should return the drivers if possible and put your K-55's back in. For Klipschorn users there are only a very small handful of suitable replacement drivers, and truthfully -- none of them do as well down low as the K-55.

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Hi,

listening to the new drivers, You are right ....

So my "improvement" turned out to be counterproductive .... Strange that the guys from eckhorn.com use them on the Khorns ...

Yours,

Mic

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that driver looks alot thinner than the drivers I used on my eckhorns.

i remember the wooden horn being able to go down to 235hz, but none of the acr swiss drivers really went down that low.

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  • 2 weeks later...

Hi all,

this evening I installed finally the Jabo Tractrix horns to the K 55s with an 1" 2" adapter. I have to say: it's the best investment I ever made. It's virtually impossible to describe the improvements in definition .....

So, if someone succeeds to find a pair of Jabo horns (maybe on Ebay), take them, it's really incredible ...

Nice evening,

Mic

SO, HERE ARE THE PHOTOS ....

post-22510-13819298445656_thumb.jpg

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Hi all,

this evening I installed finally the Jabo Tractrix horns to the K 55s with an 1" 2" adapter. I have to say: it's the best investment I ever made. It's virtually impossible to describe the improvements in definition .....

So, if someone succeeds to find a pair of Jabo horns (maybe on Ebay), take them, it's really incredible ...

Nice evening,

Mic

how about a pic

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  • 3 years later...

Mic,

The AA network is identical to the A except the AA has a 3rd order tweeter filter and the A has 1st order. The AA offers more protection from blown tweeters but the filter is lossey and has a rough response. The A can't be run at high levels becuase of danger to the tweeter but has a smoother response.

Al K.

Al other than replacing the K-77 with Bobs CT-125 what modification could be done to the A's network to protect the K-77?
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had a bad overload recently hooking up a Promitheus TVC (their inputs/outs aren't marked and it had been a long time) to SM70 amp and amp was pushed very hard into clipping into AA-Khorn - horribly loud ! - tweeters survived - I've killed T35 in khorn/Edgar setup with just a cap highpass - I luv the zeners [;)]

hey Elso - I run CDs and will look for Epcos MKV B25832 to see if they have 12-13uF (if available in US) for my Type A for fake La Scala - got obbligato oil caps coming for Khorn - would a dry film cap do better on the tweeter?

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