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ClaudeJ1

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

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The above showed were my first simple calculations.

 

Now, to be more formal, for Kappa 15C it looks like this:

 

St=72 inches

Fo=37Hz

m=0.52

Sm=1325 sq inches (corner placement)

Vb=40 litres

 

So expansion area is:

 

x      Area
0      72,0
10    87,9
20    111,2
30    144,6
40    192,2
50    259,7
60    355,2
65    416,8
80    680,5
90    949,3
100 1328,7

In Hornresp it returns nice freq and SPL <chart 1>.

 

And now the most difficult task: folding. This part is still under development :-). One of the trials is showed below. When simulated in Hornresp it returns <chart 2>. Still not bad but Hornresp knows nothing about 180 degree fold. 

 

The other way is to build a "chimney". It would be simpler, for me to make it, for air to move through only one 90 degree fold. The height including back chamber is 100 inches.  

The graph looks amazing! Second configuration is very interesting.

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I like it. every fold will cost you high end, so the L-horn should be wonderful.

 

Bruce

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Here is an idea... combine the L horn with multiple woofers in the side of the initial horn like the SH50s are, but with a 6' plus folded horn.

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Here is an idea... combine the L horn with multiple woofers in the side of the initial horn like the SH50s are, but with a 6' plus folded horn.

 

Go for it. 

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Working with Claude, I have drafted up the Baby QP. This represents the smallest version possible. It should be horn loaded into the mid 70s; a full 30Hz below a Lascala. As well, the upper end should still have the extended smooth characteristics of the full size QP. 

Whatever happened to the Baby QP?

 

Spring is around the corner and still no pix?

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I'm hoping to put the finishing touches on to my set this weekend.     Just really need to finish bracing the mouth, and then put the lids on.

 

 

I've not seen anyone else using any bracing in the horn mouth?     In my prototypes, even though I didn't play particularly loud, I felt bracing was really essential.

 

Perhaps, I'm being a bit over cautious?    What does everyone else think of their unbraced horns?   Mine are made from 3/4" marine plywood  (quite heavy)

 

 

I don't mind about the accoustic interference from any bracing as I have a 48/dB octave LPF filter, with the corner at 280Hz.

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I have not heard any need for bracing. Perhaps at very loud volume, but I have not gone there. It wouldn't hurt anything, and it would protect the mouth in case someone sat on it.  :lol:

 

Edited by tromprof

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Working with Claude, I have drafted up the Baby QP. This represents the smallest version possible. It should be horn loaded into the mid 70s; a full 30Hz below a Lascala. As well, the upper end should still have the extended smooth characteristics of the full size QP. 

Whatever happened to the Baby QP?

 

Spring is around the corner and still no pix?

 

 

Having a few real-estate issues. The project is on hold until those issues get sorted out. Sorry for the let down.

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*waves*

 

Life has also been getting in the way down here  (soon to be father, and mashed at work) ... but there is hope to be finished well before the weather turns wet/cold

 

post-108814-0-14088100-1455153782.jpg

 

 

The bracing isn't enough to stop the need for panel damping, especially on the top.    Currently my temporary solution is to use a sheet of 1/2" rigid cardboard, and another 3/4" plywood on top.   It makes a very significant difference.

 

(built from 3/4" marine plywood)

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Thanks guys!     Just need to clean up a few more unfinished bits .... and then decide how I'm going to get some more bracing into the back chamber  (the driver is a tight fit already)

 

 

 

I think they will look the business with the horn sitting on top   (although I am scheming up a plan to hang those from the ceiling eventually)

 

post-108814-0-93858800-1448784367_thumb.

 

 

 

My rear speakers also have the look of   "DIY in black with varnished plywood", so the theme is coming together nicely.

 

post-108814-0-68410100-1415885589_thumb.

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Nice OB speakers. Do they serve as a better tech for surround? I still like your "velvet sledgehammer" comment about the Quarter Pies, that is the best review of their sound I have read so far.

Edited by ClaudeJ1

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Nice OB speakers. Do they serve as a better tech for surround?

 

Thanks.

 

 

I start by saying I don't see 'surround' speakers as having any different requirements to any other speaker  (these open baffles have been my on and off, main speakers, for the past few years).      So from that perspective, don't be confused about their "dipole" nature.    I'm not going for the traditional "surround dipole" idea, where the dipole null is pointed at the listener, and a "spacious decorrelated" sound field is created....     As an aside, I'm perplexed to see that concept still in use today, as it is not high performance.

 

 

The 'openbaffleness' is simply another way to control the coverage angle (directivity) of the speaker.     It's achieving the same goal as a horn, just with a different method.

 

If you want to limit the coverage angle of a speaker   (and ideally keep that coverage angle constant, or at least smoothly changing, with frequency) ....  ie.  prevent so much sound from going to the sides of the speaker, and aim the sound where you want it  ..... then there's two ways to go about it.

 

Use a physical barrier which constrains the radiation angle  .....   ie.  a horn  (or waveguide).

OR

Use destructive acoustic interference to cancel the output to the sides of the speaker, by allowing a front wave and (out of phase) back wave, to combine at the sides.       ie.   a dipole  (or open baffle)

 

 

The funny shape of the baffle, is done specifically to keep the coverage angle constant with frequency.    A traditional dipole (open baffle, or panel/ESL speaker) which has one or more drivers on a rectangular baffle - is very problematic.    Yes, it has a narrower coverage pattern than a typical cone/dome in a box speaker .....   but the coverage angle (and also diffraction) varies with frequency  (because the baffle size is constant, and the wavelength of sound is not)

 

This OB design is lifted from JohnK (musicanddesign.com) .... and my own small tweaks were applied to the build, and the crossover.     It is extremely similar in concept to the Linkwitz LX521  (which is the replacement for the fairly famous, "Orion" speaker).

 

It is quite nice to get comments (from people who have experienced above average hifi) who say that these (open baffle) speakers are the nicest sounding speakers they have ever heard often by a significant margin .....  and they're just the surround speakers.    :cool:

 

I'm of the firm belief that a very significant factor in that is simply the frequency response with angle .....  or whatever the term people want to use for that .....   polar response ....  directivity ..... coverage pattern.    Whatever.

 

 

I still like your "velvet sledgehammer" comment about the Quarter Pies

 

Hah.  Yes  :)

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I'm of the firm belief that a very significant factor in that is simply the frequency response with angle .....  or whatever the term people want to use for that .....   polar response ....  directivity ..... coverage pattern.    Whatever.  

 

This is why CD horns, Danley derived Unity Horns, CBT, and other skinny arrays, Linkwitz, King, and Geddes speaker designs represent the "top of the pile" in my opinon 

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I'm of the firm belief that a very significant factor in that is simply the frequency response with angle .....  or whatever the term people want to use for that .....   polar response ....  directivity ..... coverage pattern.    Whatever.

 

This is why CD horns, Danley derived Unity Horns, CBT, and other skinny arrays, Linkwitz, King, and Geddes speaker designs represent the "top of the pile" in my opinon

This is why I am so hooked to my Bastanis Mandala first and now Klipsch Heritage line.

post-61702-0-09600000-1455330032_thumb.j

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