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ClaudeJ1

Quarter Pie Bass Horn: Measured FR, How2Build, and Hornresp

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I'm working with Claude on an idea of his. There wasn't a K-402 drawing, so I made one for Sketchup and thought I might share it with you all. Download the attached zip file and extract the sketchup (skp) file. The dimensions match those in the Cinema Series 2012 brochure of the KPT-402-HF which is 27.25 x 39.75 x 23.75

 

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Klipsch K-402.zip

Edited by mustang guy
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As long as it's dimensionally accurate, it's more than a piece of art. It's useful to design a matching bass horn.

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Hi Claude

 

Firstly, great work and thanks for the fantastic build journey.

 

After reading just about every post in the thread I’ve decided it’s time to stop talking about horns and start building!!!

Is there an updated set of drawings available?

The only other question I’d have would be around a suitable driver, you mentioned the JBL2225, would there be any dimensional changes required?

What other suitable drivers would you recommend?

 

Once again thanks for sharing your results.

 

Regards Dave

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Well, it's in post #1 in RED. The Eminence Kappa 15C is my favorite, even though my original design used EVM 15L woofers, which are very good also. The 15C 4 ohms, so it draws more power from the amp to try and keep up with the treble section more easily, and it has slightly better response in the midrange than a K33 or it's replacements, Also, it's very affordable and has lower and more defined bass response. IOW, the best balance of performance and price.

Edited by ClaudeJ1

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I have used 3 different woofers that Claude recommends in my QPs, the K33, Kappa 15c, and EV 15L. All work fine and with a bit of EQ will sound more or less the same. I recently had the EV 15L in one  QP and the 15c in another and did an unscientific back and forth comparison. The 15c was the winner with me with its fatter bottom end, though again with a bit of EQ that can be coaxed out of the EV driver as well.

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I have used 3 different woofers that Claude recommends in my QPs, the K33, Kappa 15c, and EV 15L. All work fine and with a bit of EQ will sound more or less the same. I recently had the EV 15L in one  QP and the 15c in another and did an unscientific back and forth comparison. The 15c was the winner with me with its fatter bottom end, though again with a bit of EQ that can be coaxed out of the EV driver as well.

Agreed. Just keep in mind that boosting the midrange causes less IM distortion and cone excursion as boosting the bass, but, to get the same output, the cone motion would be the same in all cases. The EVM is about 1.5 db more efficient, so would still draw a bit less power (even with the slightly higher drive voltage required for the impedance difference and the EQ). All of these drivers will do the job, and in all cases, the HORN is doing most of the work. The rest is just tweaks for your ROOM and personal preference on how bass should sound. You still should have a subwoofer below 60 Hz., although this horn sounds good without one. WAY better than a LaScala with the same drivers. The 15C is easiest to implement and in all cases, I would recommend bi-amping with active Xover on the bass section at least. Even if you do the treble section actively, I would still recommend a series capacitor for protection and/or maybe only using a Tripath chip amp of less than 10 watts if you don't use a cap. You will never use more than milliwatts in the treble section, 10W in the woofer horn on peaks, and maybe 100 W in a subwoofer, unless it's an F-20 or Tuba, then 10W is plenty there also.

Edited by ClaudeJ1
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The only other question I’d have would be around a suitable driver, you mentioned the JBL2225, would there be any dimensional changes required?

 

That woofer would work fine in the Quarter Pie. No problem. 

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I’ve decided it’s time to stop talking about horns and start building!!!

 

Be sure and post photographs of your progress. 

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Progress.....

Decided to build them out of MDF as they're going to be paint finish. I'm no master cabinet maker so paint finish will be safest.

Using a couple of stiffening blocks and an extra rib on the long plain side. (external)

I'm going to install the driver then put the top on so i won't have an access door, if i need to open it up at any stage I'll cut the end out. To stiffen the panel where the access door would be I'm going the put a brace between the driver magnet and outter panel.

The Yamaha 6681's and Kappa 15c are on the way.

Need to start thinking about cross over....

c1e19feadd4fca24fb2279d209fd599b.jpgbd68a442e2e7445580118013db36d219.jpg3718ca712afe316089d59dd114ca558f.jpg441d961cc6a3fa6d4471d61f7f8b1ee5.jpg

Sent from my D5833 using Tapatalk

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Nice variation on a build. Because of your material choice, you will own the "best bang for buck" award AND be rewarded with superior bass definition, smoothness, and impact!

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Good looking build!

I have found bracing the front to be optional sound-wise, but with MDF I would brace it in at least a couple of places. Not for sound but structural integrity. Plywood bends, MDF not so much. These things are too easy to sit on.

Edited by tromprof

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Thanks guys, i was planning to put some braces around the front of the opening as shown in a previous post.

Also had a question about the rear chamber volume, the construction drawing shows 8" from the driver mounting face to inside of the rear panel, correct? Looks quite a small volume chamber for a 15 driver, sure its right but it just looks small.....

Also now looking at cross over as drivers are underway.

From memory the call was to cross over at 400hz with first order, correct?

From what I understand the 340 horn with the Yamaha 6681 should be ok crossing around there as well.

Appreciate your thoughts on this.

Regards Dave

Sent from my D5833 using Tapatalk

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Thanks guys, i was planning to put some braces around the front of the opening as shown in a previous post.

Also had a question about the rear chamber volume, the construction drawing shows 8" from the driver mounting face to inside of the rear panel, correct? Looks quite a small volume chamber for a 15 driver, sure its right but it just looks small.....

Also now looking at cross over as drivers are underway.

From memory the call was to cross over at 400hz with first order, correct?

From what I understand the 340 horn with the Yamaha 6681 should be ok crossing around there as well.

Appreciate your thoughts on this.

Regards Dave

Sent from my D5833 using Tapatalk

The rear chamber volume could be made larger, but it will just shorten the horn. All that would do is reduce a tiny peak before cutoff, so it's not a good trade off. Stuff the chamber full of foam is a better thing to do.

 

Xover sounds about right since the Yamaha driver is 1.4" and the best compromise between 1" and 2"

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Also had a question about the rear chamber volume, the construction drawing shows 8" from the driver mounting face to inside of the rear panel, correct? Looks quite a small volume chamber for a 15 driver, sure its right but it just looks small.....

 

My instinctive reaction was the opposite....   but it depends on the driver parameters.

 

(of course you also have the internal triangular volume of the first horn section)

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From memory the call was to cross over at 400hz with first order, correct?

From what I understand the 340 horn with the Yamaha 6681 should be ok crossing around there as well.

 

 

 

For the woofer you are using, if you add a first order filter at ~ 400hz, that will add to the already existing first order low pass response (which is also ~ 400hz from memory), to make a linkwitz riley second order low pass response at 400hz.

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Thanks Claude. So i should fill the rear chamber and long triangle sections of the chamber with foam, is it ok to use polyester type foam or does it need to be something special? (pillow or quilt filling type)

Also.....

I remember reading a post mentioning standing the quarter pie horns on their side so the driver would be at the top firing down. Would there be any issues running them this way?

Thanks again for keeping me on track....

Dave

Sent from my D5833 using Tapatalk

Edited by nzlowie

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Thanks Claude. So i should fill the rear chamber and long triangle sections of the chamber with foam, is it ok to use polyester type foam or does it need to be something special? (pillow or quilt filling type)

Also.....

I remember reading a post mentioning standing the quarter pie horns on their side so the driver would be at the top firing down. Would there be any issues running them this way?

Thanks again for keeping me on track....

Dave

 

Both these questions affect the high frequency response, so it depends on how far up you want to run the horn.   Anything below ~ 300hz is relatively unaffected.

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Thanks Claude. So i should fill the rear chamber and long triangle sections of the chamber with foam, is it ok to use polyester type foam or does it need to be something special? (pillow or quilt filling type)

Also.....

I remember reading a post mentioning standing the quarter pie horns on their side so the driver would be at the top firing down. Would there be any issues running them this way?

Thanks again for keeping me on track....

Dave

 

Both these questions affect the high frequency response, so it depends on how far up you want to run the horn.   Anything below ~ 300hz is relatively unaffected.

 

I used leftover seat cushion foam just around the woofer itself. It measured smoother with it than without. I concur with Dave's comment, but just try it and see. Tromprof had no issues with it at 400 Hz. but it was a surround, not the main.

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One last question before i put the tops on...

Because the horn driver opening is smaller than the cone surround the cone can only move a very limited amount in positive direction before it contacts the mounting board. Sure this isn't an issue but i just thought I'd ask....

4f6b15ce63f93c7cbbec38b96449d2e3.jpg

299dff81479da7fbf38df2816d009938.jpg

Primed ready for tops...

6a4fba33c70a0cad3b15da80d34d2a92.jpg

Thanks

Sent from my SM-T800 using Tapatalk

Edited by nzlowie

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The cone excursion will be typically less than 1/16" at normal to loud listening levels. If you had an issue with cone bottoming out, you would be too loud and damaging your hearing.

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