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A time-aligned top end - Part II


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Thanks guys - I'm not trying to hijack or drive a wedge here. I was just trying to understand:

1) what Bentz meant in his response to the multiple-entry horn approach (thanks for explaining, Mike, I appreciate it), and

2) whether or not the multiply-tapped horn approach has merit in response to the time-alignment discussions here. One thing that might help with convergence is to be able to hear SH-50s or -60s. I've not heard any negative stories about the Synergy designs (not that I'm in the market for any).

What surprises me is the lack of discussion on using a single midrange/tweeter horn with a single wide-range driver of high quality to avoid much of the issues discussed here. This eliminates the tweeter altogether (i.e., for home-use systems), and in terms of power handling and audible FM distortion, I don't believe that there is much of a downside by going to a 2-way, thus avoiding the midrange to tweeter crossover/time alignment issues since they are apparently difficult to resolve without employing active digital crossovers... [;)]

Chris

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"I'm sure you will find a way to improve on B&Ws method and share it with us"

Yes.. Get the lossy all-pass equalizers out and position the direct radiators they use equi-distant from the listener. Oh, that's right, they already do that! Now.. show me a buildable network of all-pass filters that will delay a K77 enough in time to equal a K55 on a K400 horn. If you can't, I WILL and show what it would take to do it and why it's not practical!

OR -- Design a network for me that has sharp enough skirts that there is nothing to time align. That is, Go to a catalog of singly-terminated normalized elliptic filters and scale them into a 6000 Hz diplexer. When you are done you will have something that will make it sound better. BTW: have fun finding the 3 dB point on an elliptic filter normalized to last-ripple at 1 radian!

All-pass equalizers cause for more trouble than they solve.

Al K.

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"If you can't, I WILL and show what it would take to do it and why it's not practical!"

OOPS, I forgot, I already did half of that already.

Sounds travels 13500 feet / sec. The K400 is 22 Inch long and the K77 sits back about 2 inch. That says we need to dealy the tweeter by 20 Inches. 20 / 13500 = 1.48 mSec. The example earlier used four 2-nd order all-pass sections for an equal ripple delay of about .266 mSec. So.. all we need is 1.48 / .266 = 5.56 times as many sections. We had 4, so all we need is 22 sections. That's just plain DUMB!

Al K.

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"Now.. show me a buildable network of all-pass filters that will delay a K77 enough in time to equal a K55 on a K400 horn. "

I've stated twice in this thread that that is not practical.

Delay the woofer to match a K600/K700 in a Cornwall/Heresy, can do. Delay the tweeter, not practical (now there, I've said it three times in this thread).

Please look at this and calculate the delay on the tweeter at the crossover point (the acoustic center of the tweeter is in front of the woofer in this model).

http://www.bwgroup-support.com/downloads/techmanuals/bw/DM3000-TM.pdf

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"Please look at this and calculate the delay on the tweeter at the crossover point (the acoustic center of the tweeter is in front of the woofer in this model)."

Group delay comes to a peak at around the 2 dB point down the slope of most filters. A group dealt peak is NOT TIME DELAY because it is not flat over the area. This represents phase non-linearity which is inaudible and attempts to correct for it in any way is detrimental!

Al K.

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Al. I have been thinking about what to do all weekend and am starting to lean in the direction of attempting my own build. I will need to read up on the Tractrix horn and run down some of the programs that will allow me to draw the profile.

In your suggestion, you mention a cut off of 328Hz. If I get near a cutoff in the mid 250's, will I be able to go from 500Hz to 20kHz? Ideally, I would like to be able to go as low as 500Hz up to whatever the Faital Pro driver can give me....

Once again I have a steep learning curve ahead of me. I beleive building a round horn will be fairly straight forward. The Eliptrac, on the other hand, is one heck of a project.

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Guest David H

In your suggestion, you mention a cut off of 328Hz. If I get near a cutoff in the mid 250's, will I be able to go from 500Hz to 20kHz? Ideally, I would like to be able to go as low as 500Hz up to whatever the Faital Pro driver can give me....

Rudy, crossing a half an octave above the Fc should be ideal. Sent you a pm.

Dave

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  • Posted by
tomservo (M) on February 15, 2011 at 14:39:37

In Reply to: RE: why did this type network improve the sound of a coaxial? posted by freddyi on February 15, 2011 at 09:00:44

C3,4 and L3,4 form an all pass filter.

This normally produces a flat amplitude response but exhibits a phase shift such that the lower part is delayed relative to the upper part (like a loudspeaker)..

Best,

tom

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Reading some of these posts makes me wish I knew half of what you guys have forgotten about audio!

Thanks Dave.

The goal is reach the best possible solution for a time aligned top end using either the K69 or the Faital Pro driver Al mentioned.

Since I am not limited to fitting the horn in a top hat, I'd like to experiment with a round Tractrix....I think I'll give it a shot and see what happens. Now I have to try out some of the online calculators and graphing aids. I found one .js script that works with Illustrator to draw a Tractrix curve.

I will also check out the other threads on the forum regarding Tractrix horns etc.

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Good luck Rudy, I am anxios to see your progress.

Dave

Thanks Dave. Once again I'm in deep over my head! I smell more excuses for getting more tools. So far, I built the DBB and the TH subwoofer. I guess adding a DIY horn to my system can't hurt.

I just need to get at least some basic knowledge of the Tractrix horn design. Surfing build pages, there are some interesting things guys have done to build these horns.

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Well folks, It seems the coaxial B&C DCX50 plus the 9KHz Linkwitz-Riley crossover idea that started this thread is already obsolete! With a HUGE thank you to Lee Clinton (Arkytype), we have both horizontal and vertical polar plots of the Faital pro HF200 driver on the Eliptrac 400 prototype horn. It looks like we have what we have all been waiting for, a good two-way Khorn!

Here is the polar plots all overlaid for direct comparison.

BTW: Bob Crites has the HF200 drivers in stock at what looks to be a very good price.

Al K.

post-2934-13819637206982_thumb.gif

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Guest David H

It looks like we have what we have all been waiting for, a good two-way Khorn!

I am pleased to announce one of ouf first customers to use this horn in a 2-way is thrilled with the results.

A quote from the reviewer:

3. The soundstage is massive and almost delivers a total wrap around effect but stays focused across the listening spectrum. There is exquisite center focus imaging ...and even though the soundstage it larger than the (<<<Edit>>>) it stays tight and focused. Never gets sloppy. Another big thing is the clean character of the sound. I have two requirements clean and smooth and man I have got both.I had both before but i have even more now PROBABLY due to authority in the mid highs and highs which makes them seem more "right there in the room"

post-24405-13819637211662_thumb.jpg

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