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Old 12th February 2013, 02:42 PM   #101
DrBoar is offline DrBoar  Sweden
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Corner loading it is!
Quadral midrange
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And combined nearfield and horn opening (in corner) all horn opening responses are adjusted so that the peak output is level with the highest output of the driver, so they are combined but not properly summed in these graphs
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The very high quality CSX 5.5" woofer that should have an Fr of 48 Hz
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The next one is a shielded Peerless I go on a sale at Parts Express 10 years ago
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And finaly the responses at 2m
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That is 2 m from the corner so the distance to the driver is a bit shorter, this is not the same corner as priviously. Why the hornmouth response of the Quadral has more 40 Hz output but less at 2 meters I do not know

A breif listening suggest better slam but then I have it in an other corner and other drivers, so that is for other builders to find out.

I think this will be the end of this research of the CBLH the restart of the Dorspen One BC project.

Last edited by DrBoar; 12th February 2013 at 02:43 PM. Reason: forgotten image
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Old 11th March 2013, 03:25 PM   #102
Sus is offline Sus  United States
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As a noobie I have no idea what the graphs mean,good or bad. Credit is due Dr Boar as fast moving and well educated in the art of the audio. Can any one help me by recommending a good book or two?

I've been meandering though this unfathomable swamp called audio for a few weeks now. I'm not ashamed to acknowledge I know little of what I read.

A question is- is sound absorbing ceiling tile every used for sound damping in a speaker.? I have had very good results with this in Muffler design on reducing noise levels in Shop Vacs Mufflers. Cars have used them for years.. The Helmholtz resonators can easily be made that can be variable tuned. This might be of assistance in matching a speaker to a room. I was not aware speakers used these.
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Old 11th March 2013, 04:19 PM   #103
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by Sus View Post
As a noobie I have no idea what the graphs mean,good or bad. Credit is due Dr Boar as fast moving and well educated in the art of the audio. Can any one help me by recommending a good book or two?

I've been meandering though this unfathomable swamp called audio for a few weeks now. I'm not ashamed to acknowledge I know little of what I read.

A question is- is sound absorbing ceiling tile every used for sound damping in a speaker.? I have had very good results with this in Muffler design on reducing noise levels in Shop Vacs Mufflers. Cars have used them for years.. The Helmholtz resonators can easily be made that can be variable tuned. This might be of assistance in matching a speaker to a room. I was not aware speakers used these.
Welcome to the world of diy speakers - you are in for a lot of fun...

There is some good reading in the technical papers by MJK on his website Quarter Wavelength Loudspeaker Design.

The use of ceiling tile is used extensively by @hm as internal partitions inside his horns.
http://www.hm-moreart.de/1.htm

Here are some scans of the Dinsdale papers.

http://www.metaleater.narod.ru/Dinsdale_Horns_1.pdf

http://www.metaleater.narod.ru/Dinsdale_Horns_2.pdf

http://www.metaleater.narod.ru/Dinsdale_Horns_3.pdf

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Old 12th March 2013, 05:49 AM   #104
DrBoar is offline DrBoar  Sweden
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I would not go for the Dinsdale papers as they only cover horns and are quite dated by now, that is the recomended drivers are not avaible any more and things like Thiele Small parameters are not discussed.

There is a lot on the net and if you want it collected in a book
High Performance Loudspeakers: Martin Colloms: 9780470094303: Amazon.com: Books. It might be in larger libraries as well.

I have the first and second edition, the current one is the sixth.

If you find books from the 1950-1970s DIY loudspeakers, you build boxes and screw drivers into holes of the boxes and make a crossover from a table or simle formula. Computer simulations and gated response measurement that costed millions in the 1970s can now be had with free software and a microphone for 100 dollars.

The upside is that we now are so much more in controll of the design and building of DIY speakers, the down side is there is a technical maze to get lost in. It is still just a tool to listen to music and have some fun building it. (Smile)
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Old 12th March 2013, 04:37 PM   #105
xrk971 is offline xrk971  United States
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Dr Boar,

Thanks for tip on book. I will check i tout.

I was warned that the Dinsdale papers have errors - but nonetheless useful for understanding some of the same overall goals of speaker building.

The software for modeling has been a paradigm shift - just like sims for camera lenses have made modern optics so good and free of trial and error.

A very good flat-response microphone for purposes of designing speakers can be had for $2 (Panasonic WM61A capsule ) and the software is free (Holmimpulse). Very nice product and great tool for diy'er.

John Conover: Using the Panasonic WM61A as a Measurement Microphone

HOLM Acoustics
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Old 9th June 2013, 11:50 PM   #106
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I just completed a test box of this design and loaded it up with a tang band W5-1611. Using test tones I found it to have good output to about 45hz before rolling off. Have not had time to run a FR sweep yet. I found that it needed BSC, and running it filterless it sounded pretty thin. However with some BSC in place it sounded good and it's clear that the horn/TL is doing its job. I'll try and post measurements and a picture or two in the coming days.
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Old 10th June 2013, 12:05 AM   #107
xrk971 is offline xrk971  United States
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Chaz,
Looking forward to your photos and freq sweep. I am surprised it needs BSC as there should be plenty of bass gain to offset baffle step losses.
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Old 10th June 2013, 12:15 AM   #108
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Originally Posted by xrk971 View Post
Chaz,
Looking forward to your photos and freq sweep. I am surprised it needs BSC as there should be plenty of bass gain to offset baffle step losses.
I had thought so too, but it sounded very thin out of the gate. 3db of bsc around 500hz up balanced things out (I was not being terribly scientific about the whole thing). MJK's article seems to hint at this, though I wasn't sure:

Quote:
Looking back at my previous documents addressing back loaded horn designs, the original goal was for the horn geometry to be so efficient that when its low frequency SPL output was combined with the driverís SPL output the need for any form of baffle step compensation would be eliminated. In a no compromise system where size is not an issue, this approach is probably still valid. Unfortunately as nice as this concept sounds, I no longer believe that this is possible for a reasonably sized back loaded horn enclosure design.
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Old 10th June 2013, 06:19 PM   #109
DrBoar is offline DrBoar  Sweden
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How are the horn loaded? A corner with flimsy plaster walls as is common in the US really is a very different corner than a brick/ concrete wall corner. I did measurements with corner horns comparing true concrete corner to one with concrete floor and side wall but backwall in 1/2" plaster wall. I do not have the graphs at hand but as I recall at 80 Hz downwards I lost about 6 dB.

Good to see other builders trying them out
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Old 10th June 2013, 06:39 PM   #110
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That 6 dB loss with plaster walls is the BSC right there. I am surprised it is that lossy vs concrete/brick.
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