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ClaudeJ1

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

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I modelled Baby QP in Hornresp. With EVM12L, 40 sq. inch slot and smaller back chamber it looks nice.

Dimensions are not too precise, I just wanted to find a broad picture. Probably Claude could (and will :-) do that better.

 

 

 

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post-60882-0-37860000-1448982887_thumb.j

post-60882-0-93380000-1448982891_thumb.j

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I modelled Baby QP in Hornresp. With EVM12L, 40 sq. inch slot and smaller back chamber it looks nice.

Dimensions are not too precise, I just wanted to find a broad picture. Probably Claude could (and will :-) do that better.

 

 

 

That looks pretty good. Thanks for the numbers.  I am really looking forward to this...

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Overlaid on a LaScala plot in Photoshop shows significant extension on both ends of the plot. I would almost say this is horn bass to 65Hz and better as a two way...

 

(This is all just speculative and by no means exact ...until I actually build a pair.)

post-58443-0-17700000-1449003956_thumb.p

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Probably Claude could (and will :-) do that better.
Probably not. You did a fine job. 

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(This is all just speculative and by no means exact ...until I actually build a pair.) Attached Thumbnails

Now you know why I built mine and measured before I posted the Horn resp data. I had to be sure.

Edited by ClaudeJ1

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My QP in pi/2 space when measured tracks Hornresp simulation very closely (after I changed some woofer data as I found some inaccuracies in Monacor T/S parameters).

LaScala looks better in real life than modelled in Hornresp.

I suppose that BQP will play like modelled too.

Edited by Mariusz_

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I suppose that BQP will play like modelled too.
Even if it only gets down to 80 Hz., it's a perfect hand off to a THX subwoofer, maintaining superior bass definition in the range where it counts the most.

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When I spent a day with PWK, the photo in my Avatar was taken by my wife in front of the old building in Hope, where Paul did most of his development work on speakers. I distinctly remember him saying to me that when he did the K-500 horn for the Belle, it made him realize that the K-400 horn was longer than it needed to be. Perhaps the Baby Quarter Pie will show my full Quarter Pie (mini MWM) to be larger than it needed to be also. LOL.

 

Either way, it's nice to have a choice.

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Probably Claude could (and will :-) do that better.
Probably not. You did a fine job. 

 

Fine and refined: the new dimensions are more precise.

And I put Peavey 1508-8 HE BWX inside.

 

Black: Baby QP

Gray: Regular QP

post-60882-0-78460000-1449055456_thumb.j

post-60882-0-86540000-1449055464_thumb.j

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ine and refined: the new dimensions are more precise. And I put Peavey 1508-8 HE BWX inside.   Black: Baby QP Gray: Regular QP

 

It's modeling better than I thought it would. If the model is correct, it should go lower than my worst case scenario. As you know it's also very room dependent below 100 Hz. so we shall see if there are measurements.

 

As you also know, they sound much better than they measure, right?

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Overlaid on a LaScala plot in Photoshop shows significant extension on both ends of the plot. I would almost say this is horn bass to 65Hz and better as a two way...   (This is all just speculative and by no means exact ...until I actually build a pair.)

 

Well, it would be nice for you if it was useful between 60 to 600 Hz. The pattern control of 90 degrees on the K-402 starts to falter below 600 hz. but it would meet the dispersion of the Baby Qpie, approximately. Another super easy build is the LAB 12 tapped horn I built that got me hooked on Danley commercial subwoofer technology. I you added just one of those you would be rocking about 15 Hz. to 18 Khz pretty flat. So any low synthersizer or big pipe organ notes would be yours to enjoy. 

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I assumed 7x13 slot, 15.5 internal height and lenght measured on axis of 3 sections. 

post-60882-0-14340000-1449058811_thumb.j

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Ok I will when I am back home. As far as I remember 15C gives same bottom and earlier rolloff at top.

 

 

 

-------------

 

Edited:

Kappa 15C

post-60882-0-29860000-1449086170_thumb.j

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Edited by Mariusz_

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wow, the top really rolls off on that one. I would have expected better considering Claude's post that it is a better top end LaScala...

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wow, the top really rolls off on that one.

 

I haven't even done detailed measurements of the high frequency response, as I use a steep low pass filter @ ~300Hz .....   but I would expect there's quite a few problems in the response above ~ 300Hz due to the dimensions of the horn (40cm height), and the 'approximate' expansion of the horn path.

 

----

 

I'm working out what sort of bracing to put in on mine at the moment.   I've built it from fairly good quality "marine" 3/4 inch plywood....   but there is a lot of vibration (not really surprising), even at 'home' levels.

 

Making bass (well, the couple of octaves above 50Hz) with such low cone excursion, is just so nice.    The tone and detail, really do make for a 'velvet sledgehammer' effect.   <3

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wow, the top really rolls off on that one. I would have expected better considering Claude's post that it is a better top end LaScala...

15C is 4 db better in the 400-500 Hz range on a LaScala than a stock K-33, and as good as a K-43, which costs almost 3X as much. The difference will be similar on a QPie or BQpie. You will hear it, I promise.

Edited by ClaudeJ1

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wow, the top really rolls off on that one.

 

I haven't even done detailed measurements of the high frequency response, as I use a steep low pass filter @ ~300Hz .....   but I would expect there's quite a few problems in the response above ~ 300Hz due to the dimensions of the horn (40cm height), and the 'approximate' expansion of the horn path.

 

----

 

I'm working out what sort of bracing to put in on mine at the moment.   I've built it from fairly good quality "marine" 3/4 inch plywood....   but there is a lot of vibration (not really surprising), even at 'home' levels.

 

Making bass (well, the couple of octaves above 50Hz) with such low cone excursion, is just so nice.    The tone and detail, really do make for a 'velvet sledgehammer' effect.   <3

 

Sledge hammer for sure in the bass notes that matter most. Anyway, I never used mine above 300 hz. because I had Klipsch K-402's with the amazing K1133 driver from 300-5,000 Hz.then to a tweeter. I do prefer 3 way with sub when it's done right, and that is what I have now.

 

Your musings about what happens in that horn above 300 hz. have yet to be proven in the real application. I know that others who have built the QP have used it at 400 and 500 Hz. without any complaints. However, like you, I have not heard or measured for myself, so it's all hearsay and feedback from the field, so to speak, by both of us. Looking forward to more feedback once the BQP is built and measured/heard.

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wow, the top really rolls off on that one. I would have expected better considering Claude's post that it is a better top end LaScala...

I should go for it anyway.

Look at my chart when models and measurments are overlayed and scaled:

Blue - measured QP with Monacor woofer in my room.

Green - modelled Monacor in QP

Red - modelled Kappa 15C in BQP

In my case I don't filter QP at all and let it play all the way. My midhorn starts from 350-400Hz (1st order slope).

As one can see, Kappa should give similar response.

post-60882-0-19900000-1449154531_thumb.j

Edited by Mariusz_
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I prefer an active Xover on a Quarter Pie, or any bass horn, since I can control the slope, Xover point and EQ if necessary. Remember that the distortion penalty of EQing at higher frequencies is negligible, whereas EQing the low end adds a significant amount of IM distorting by overdriving the cone.

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