lorcoll
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Posts posted by lorcoll
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1 hour ago, glens said:
The midbass horn of the AG has a mechanical cut-off (at 170hz) and doesn't use a crossover filter anymore.
What?
This is what you can read on the Avantgarde web site about the absence of the filter:
CDC stands for “Controlled Dispersion Characteristic“. It is a technology developed by Avantgarde Acoustic™ to precisely align the frequency response, the sensitivity of the driver, the geometry of the membrane and the air chamber at the horn throat to the response curve of the spherical midrange horn. This way we manage to avoid any passive filter components in the signal path – routing the music signal directly to the voice coil of the driver engine. Less components, less interactions, less friction ensuring more detail. This is how CDC works: the lower cut-off frequency of a horn loudspeaker is determined by the size of the horn. The larger the horn, the lower the response. Below the cut-off frequency of the horn, the response falls off steeply at 12 dB/octave. The midrange drivers 6 dB roll-off is set to exactly the same frequency thus achieving a total of 18 dB/octave bottom end attenuation. Avantgarde Acoustic™ speakers thus operate only down to their cut-off frequency limit and require no high pass filters. The upper frequency response is determined by the driver itself. However, it can as well be influenced acoustically by the horn. For this purpose, Avantgarde Acoustic™ places a small chamber between the driver’s membrane and the horn throat. The driver does not emit directly but via a small air chamber into the horn throat opening. This air volume operates as a low-pass filter and automatically filters frequencies above the resonance volume of the chamber (at 6 dB/oct.). Avantgarde Acoustic™ now matches the -6dB roll-off point of the midrange driver to exactly the same frequency of the CDC air chamber. Thus we obtain an acoustic attenuation of the frequency response of 12 dB without any passive frequency crossover. No further low pass filters are necessary! The CDC system thus causes the midrange to only operate within its operational band and steeply fall off at the transition points.
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Thanks for all replies.
The Avantgarde sub has a built-in power amplifier, it sound good but loses the velocity and immediacy of a true horn bass like the Khorn.
The midbass horn of the AG has a mechanical cut-off (at 170hz) and doesn't use a crossover filter anymore.
I have tried the active bi-amp and I have been never satisfied with the result.
Chris, according to your scheme, can I add a series inductor of 0.64mh to the existing 4mh?
Then I can add a parallel 47uf cap to the 140uf in the bass bin.
Is it right?
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I have tried the two mid-high horns of the Avantgarde Duo with the Klipschorn bass bin and the result is incredible: more natural bass with the same extension without any constraint.
In a word: exceptional. But I notice an overlap in the mid-bass due to the frequency cut-off of the Khorn network (in the bass bin I have a 4mh inductor and a 140uf capacitor).
I need help to modify those values to obtain a second order filter with a cut-off of 170hz (12db/octave).
The round mid horn starts at 170hz. The mid-high was extremely good with the standard khorn, but now it reaches a level of purity I cannot imagine before.
I use a passive bi-amp: Golden Tube Audio SE-300B monoblock in the mid-high and a CJ MV-50 for the bass bin (the preamp is a CJ PV-8).
Thanks for your help
Lorenzo
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Hi, if you have to sell the AK2 crossovers I can buy them.
Ciao from Italy.
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On 10/1/2017 at 3:35 PM, Klipschunger said:
I will be getting ak-3 or crites to replace my ak-2's in about a month... i will sell you mine.
I have sent a PM to you
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Ok. I'll buy your AK-2's.
I'm waiting for your news.
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I have a pair of AK2 Khorn and I need another AK2 crossover for an ACR rear system.
I have all ferrite components that are fine with the stock AK2 network.
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Hi.
I need a pair of complete AK2 Crossovers for my rear set of Klipschorn.
Lorenzo
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Bump...
Nobody has a pair of AK2 to sell?
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Frzninvt, I know they aren't the best xovers for the Khorns but I already have one pair with those and I need another pair for the rear system.
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Thank you, but only now I have seen your reply.
I have sent a PM to you.
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Hi, I need a pair of complete AK2 crossovers (I live in Italy), for my second pair of Khorns.
Lorenzo
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Ok, I think I have understand now.
I don't speak english well (I live in Italy) and I have misunderstand your explanation for sure.
But for the mounting board and rails you screwed the woofer directly onto the motor board with positive effects; why don't have I to remove them?
I thought this was fully clear for me.
Thank you for the reply.
Lorenzo
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They use K33P in the 1973 Khorn and K33E (square magnet) in the 1984 speakers.
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Hi.
I have a question for LarryC:
I have two pairs of Khorn (1973 and 1984 year).
The two pairs differ in the motorboard rail that 1984 don't have and for the size of the pyramidal blocks (inserts) inside the 3"x13" hole on the fix motorboard (the 1984 blocks are smaller).
The pics of your mod are now not visible, so I would know if I have to reduce the Pyramidal blocks in the 1973 Khorns or I have to eliminate them definitely.
I have already screwed the woofer directly onto the motor board in the 1973 one.
I have attached pics of the two types.
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Hi Jim.
I have sent a PM to you.
Lorenzo
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The 1984 pair has the best bass but I have still to screw the woofers directly onto the motor board to see the first difference.
For an objective comparation I have to mount the 1984 crossover too.
I hope someone have already done the comparison to tell us his impressions.
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Why Klipsch has reduced the size of these blocks in the end of the 70's?
Even the AK5 type has the reduced blocks.
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Hi.
I have a pair of 1984 Khorn and today I have bought a 1973 pair.
The two pairs differ in the motorboard rail that 1984 don't have and for the size of the pyramidal blocks (inserts) inside the 3"x13" hole on the fix motorboard.
I know that the best results is with the woofer screwed directly onto the motor board, but what the differences (if any) with the two type of blocks (it is smaller in the 1984 Khorns).
I have attached pics of the two types.
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Hi, have you sold the crossovers?
If not, I'm interested to buy them.
Regards.
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Hi Jim.
I can trade your crossovers with a pair of K55-V or vintage tubes.
Please tell me what tubes do you prefer.
I live in Italy and I'll use the crossovers for a diy project.
Lorenzo
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Hi, I have bought a pair of Altec 19 to compare with my Khorn.
They are supposed to be the later model, but my pair are specular: the reflex hole is on the left in one speaker and on the right side in the other.
The drivers are: 416-8C and 909-8A (pascalite diaphragm).
Are these original M19 or a clone?
Many thanks.
Lorenzo.
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I have the hum pots on my amp so I have reduced it to a very very low level.
I have discovered this sublime tube now and I'll try the 245 globes surely (who knows if there will be another surprise).
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Cut-throat,
are your tubes the RCA Radiotron UX-245 globe?
Have you compared them to the Emission Labs 45 meshplate?
I haven't tried the 245 globe but if you think they are the best, I'll try them.
Avantgarde Duo mid-high horns with Klipschorn bass bin: How to modify cut-off frequency
in Technical/Restorations
Posted
Here is another more compact explanation:
The 7-inch midrange drive unit operates in the region between 170 Hz to 2 kHz. Housed in a separate grey painted metal cylinder enclosure, there is no crossover for the midrange driver, in fact it is driven full range. Avantgarde designs the drive unit to have a mechanical filter – high frequencies are gradually filtered off via the moving mass of the cone (mechanical impedance) while the low end extension will be limited by the natural impedance rise of the driver when the frequencies drops to around the fs – the natural ‘resonance’ frequency of the drive unit.