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Old 30th January 2013, 10:10 AM   #81
xrk971 is offline xrk971  United States
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You can record short sound clips as mp3 and save as zip file in a post on this forum. I do that all the time.
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Old 30th January 2013, 07:41 PM   #82
Ivo is offline Ivo  Netherlands
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Quote:
Originally Posted by DrBoar View Post
I am getting to the finish line with this horn soon. But lets not forget that it is it a compact horn
Click the image to open in full size.
Dr Boar, I love that Schmackshorn behind it!

I had one of those myself, I loved it.
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Old 30th January 2013, 08:53 PM   #83
DrBoar is offline DrBoar  Sweden
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Thanks for the tip about the mp3 I have already glued braces now, next time
That is not the Schmacks for 8-9" drivers but the Klinger for 12" drivers.

The glued box (green) is has sharper peaks than the final open one (blue). Using flexing walls to absorb vibrations is not new the Decca Corner horn from the 50s was "improved" by removing a brace. Still I am surpriced that me on top of the side of the box was not enough to make it inert. I have to make some frequency measurements as well to see how far of I am. Those last minute surprices...

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Old 30th January 2013, 09:18 PM   #84
xrk971 is offline xrk971  United States
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Dr Boar,
Could the sharper response be more due to a tight seal rather than stiffer walls? If it is indeed a seal issue, could tiny pinhole controlled "leaks" be added to smooth it back down? Yes, the efficiency will suffer but it looked like there was already plenty of output with the clamped and gasketed version.
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Old 31st January 2013, 07:15 AM   #85
DrBoar is offline DrBoar  Sweden
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Regarding leaks vs wall vibration, I have no way of measure either way, your guess is as good as mine. But with continous closed foam strips on the edges and horn side facing down on a flat suface and the strips being compressed by the weight of the horn and then some 175 lb of me as well, I find leaks unlikely but not impossible.

I have noted that free edges makes walls prone to vibrate, like the opening of the horn. In the gasketed version the top, bottom, front, back and all internal partitions are all with a free edge. Free to vibrate with not much of mechanical interlocking being done by the gasket compared to glued board.

If I could go back in time the control experiment would be to measure impedance and frequency in gasketed version and gasket plus extensive crossbraces close to the free edges that would mechnically lock the varius partitions and walls to each other.

While not the same thing I could try to knock out the braces I put in remeasure and then both glue in some braces as well as use clamps externaly to reduce vibrations. The third harmonic has pressure maxima at 1/3 and 2/3 of the lenght of the pipe, shifted by flare and folds but somewhere in those regions.
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Old 31st January 2013, 11:23 AM   #86
xrk971 is offline xrk971  United States
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What do you think of building a horn like this out of polyisocyanurate foam sheathing instead of osb?
Shop Rmax 1/2-in x 4-ft x 8-ft Polyisocyanurate Insulated Sheathing at Lowes.com
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Old 31st January 2013, 11:42 AM   #87
DrBoar is offline DrBoar  Sweden
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Why not, the idea of building speakers out of low mass material to get a low energy storage is something that has been tested over the years. The big Klinger horn on a previous post is built in soft and very light soft board, this date 50-60 years back. In the 80s Celestion had the 600 speaker with airolam walls, thin alumnium skins draped over a honeycomb lattice, light and stiff. I do not know how stiff the "polyisocyanurate foam sheathing" is stiff enough otherwise one could buy those fake plastic "glass panes" and laminate with that on both sides, that ought to become very stiff.

I have some left over MDF that I intend to use to test how different foldning affects the harmonics of a pipe. Now it appears I have to be carful about how I design access points into the box. Build and learn!
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Old 2nd February 2013, 09:15 PM   #88
DrBoar is offline DrBoar  Sweden
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This is the combined responce and it looks pretty good, the near field measurement is very close to the phase plug as close to the voice coil as I could get it. Horn is measured at center of opening as before.

Cone output is supressed from 90 to 150 Hz and also at 38-50 Hz. How much the 40-80 Hz octave can be brought up to level with the 80-160 Hz remains to be seen.

Now I have to ponder on were to put my horn for the listening session and for measurement of room integration.

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Old 7th February 2013, 12:39 PM   #89
DrBoar is offline DrBoar  Sweden
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Click the image to open in full size.

I tested some other drivers, from Altec Lansing, Audax, Bravox, Coral and Quadral. They are hardly current of the shelf units but they cover a range of parameters that should cover the space of many current drivers.

They were all mounted with the face towards the cabinet as they all were bigger than the cutout. So the driver close range is as close as I could get to the cone

Altec Lansing A 405

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Bravox 5FDRPRP polopropylene cone and foam edge.

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Coral 4L-81

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Quadral M132/25/8/PF

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Click the image to open in full size.


I will get back about the Audax driver...
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Old 7th February 2013, 01:39 PM   #90
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Cone output is supressed from 90 to 150 Hz and also at 38-50 Hz. How much the 40-80 Hz octave can be brought up to level with the 80-160 Hz remains to be seen.

Now I have to ponder on were to put my horn for the listening session and for measurement of room integration.
Dr Boar, did you make the above measurements with the horn in the corner of a room? It seems from MJK's white paper that this is really critical for testing the design.
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