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Digbethdave 
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Joined: 16 November 2018 Status: Offline Points: 406 |
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 Posted: 05 June 2020 at 9:59pm |
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doober
Young Croc 
Joined: 03 January 2006 Location: Cornwall UK Status: Offline Points: 1118 |
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Posted: 05 June 2020 at 10:16pm |
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The whole box is a bit wonky, the cheap ply is warped. Shouldn't be too far out though, I marked out the base and top accurately to get that 100 degrees correct.
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Digbethdave
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Joined: 16 November 2018 Status: Offline Points: 406 |
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Posted: 05 June 2020 at 10:28pm |
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Fair
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dlyxover
Old Croc 
Joined: 14 June 2007 Location: Liverpool Status: Offline Points: 1502 |
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Posted: 05 June 2020 at 10:35pm |
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As a prototype/proof of concept, it docent matter. great work
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In the Truth there is no news, and in the News there is no truth
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studio45
Old Croc
Joined: 16 October 2007 Location: United Kingdom Status: Offline Points: 3864 |
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Posted: 06 June 2020 at 4:02pm |
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Fantastic work! Especially with that whaney ply!
Are you concerned at all about reflections inside the horn mouth? Seems like a large parallel area there, I might be tempted to put some absorbent material on the top and bottom to catch some errant waves? |
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Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
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doober
Young Croc
Joined: 03 January 2006 Location: Cornwall UK Status: Offline Points: 1118 |
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Posted: 08 June 2020 at 10:47am |
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That is a very good point. I didn't consider the parallel top and bottom of the mouth, my main interest in this prototype is the interaction of the individual horns in the horizontal plane, and achieving smooth horizontal coverage. If I build a proper version it will be curved in the vertical plane and not have these parallel walls.
Interestingly the dip I am getting in the mid horn plots has a wavelength equal to the height of the box. I might try some van lining carpet on the top and bottom and see what happens. More testing will happen today. |
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doober
Young Croc
Joined: 03 January 2006 Location: Cornwall UK Status: Offline Points: 1118 |
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Posted: 09 June 2020 at 6:13pm |
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I did some more testing today. Putting some thin carpet covering on the top and bottom horn walls made a sight difference, so I left it there. I also made some phase bungs out of plasticine, this helped the top end of the 6" drivers a bit, but they still need more top end.
Testing was done in the garden. I think the sharp dips in some of the plots were caused by the walls, the dips moved if I tried in another part of the garden. Low mid. This is the average of 5 measurements from 0 to 40 degrees horizontally.  Mid next, again an average of 5 measurements.  HF, average of 5 again.  A huge loss of HF in the above plot. The plot was done with the speaker and mic on the ground. Here's one I did earlier with the cab on the workbench and the mic on axis  Looking at the individual plots which made the averages, they do vary slightly, but are within ~2dB at all points from 0-40 degrees, with a fairly smooth roll off after that. |
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doober
Young Croc
Joined: 03 January 2006 Location: Cornwall UK Status: Offline Points: 1118 |
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Posted: 09 June 2020 at 8:32pm |
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Timebomb
Old Croc
Joined: 11 October 2004 Location: Lancaster Status: Offline Points: 2716 |
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Posted: 10 June 2020 at 12:01pm |
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Nice, like it
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James Secker facebook.com/soundgearuk
James@soundgear.co.uk www.soundgear.co.uk |
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Sound Chippy
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Joined: 14 August 2013 Location: Aus / Melbourne Status: Offline Points: 19 |
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Posted: 15 June 2020 at 3:21pm |
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Awesome stuff Kieran, really enjoy absorbing myself in the projects you have shared with us. Its a wonderful sight seeing sawdust getting made on S.P again. Top work. Thanks again.
Kind regards Dave |
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doober
Young Croc
Joined: 03 January 2006 Location: Cornwall UK Status: Offline Points: 1118 |
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Posted: 17 June 2020 at 8:20pm |
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I got some proper mid drivers and made some bowls for the back
 This is new drivers versus the unknown 'hi-fi' ones I was using. The traces aren't exactly matched for level, the actual improvement in overall level isn't quite as big as it looks on here, there is a very noticeable increase at the upper end though.  I've still got that nasty dip just below 2kHz, I'm still trying to work out what's causing it. |
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doober
Young Croc
Joined: 03 January 2006 Location: Cornwall UK Status: Offline Points: 1118 |
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Posted: 19 June 2020 at 10:39am |
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I had a good poke around with the measuring mic, putting it right inside the mid horns, and the dip below 2k is still there right inside the horns. This makes me think it is not some interaction between the individual horns or some mouth reflections, the problem lies closer to the baffle.
Out of curiosity I decided to measure the drivers without horns, just in the rear bowl. This was measured approx. 50cm from the driver, on axis.  Interesting dip still there, so I tried some wadding in the bowl, this made little difference, so I tried some 'egg box' foam.  A small improvement, nothing to get excited about though. Next I tried moving the mic up close to the driver.  Dips are back. Not surprising really. I tried this with and without foam or wadding, foam made a very small improvement, but clearly these dips are the result of arrival time/phase differences across the cone. I have now made another baffle so I can try front chamber tweaks to try and reduce these dips. |
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doober wrote: