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JF Vented Horn (P-audio E18-600a) |
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ceharden 
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Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11851 |
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 Posted: 07 April 2008 at 4:03pm |
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Surely in a ported horn, both sides of the driver has a air path to the outside world so it doesn't matter which way round it's mounted?
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Jake_Fielder
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Joined: 08 October 2007 Status: Offline Points: 4236 |
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Posted: 07 April 2008 at 4:24pm |
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Perhaps i should tweak the design so the driver can go in either way then meausure the temp over time in either way to see if theres a difference,
also it may just happen that with one way round the drivers is closer to my modle than another way round....? so i can try both. although there may not be enough room for that.....
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Disco Stu
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Joined: 03 March 2005 Location: United Kingdom Status: Offline Points: 2492 |
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Posted: 07 April 2008 at 5:53pm |
Bearing in mind kick horns appear to push a lot of air out of the box with every movement of the driver, if the magnet is in the throat chamber one would 'assume' with all that air being pushed out, its also pushing the hot air coming from the rear of the driver away more efficiently If I am getting my BP theory right, the port is only working at very low frequencies below the cutoff of the horn so the heat would only get pushed away efficiently from that chamber if the driver was having to reproduce those low frequencies all the time. Would you concur with that? I don't know for sure, its just an assumption. Stu Edited by Disco Stu - 07 April 2008 at 5:53pm |
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All you need to know is:
Sensitivity + Power Handling - Power Compression = Max Output My acts: www.myspace.com/thebowiexperience www.myspace.com/scheisseelektronisches |
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Jake_Fielder
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Posted: 07 April 2008 at 6:19pm |
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At the tuning frequency the driver will hardly move (i picture it that every movement is being opposed by the delayed pressure change in the rear chamber, but JaKe described what was happening better.) so there is no air movement in the horn mouth, and loads of air rushing through the port.
Any higher than the tuning frequency and the horn mouth will have loads of air movment, and the higher the frequency gets the less the driver will "see" the port.
The higher frequencys on my hornresp plot is the same as if there is no port.
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Disco Stu
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Posted: 07 April 2008 at 6:48pm |
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Which would back up what I said about there being more benefit in having the magnet in the throat
Stu |
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All you need to know is:
Sensitivity + Power Handling - Power Compression = Max Output My acts: www.myspace.com/thebowiexperience www.myspace.com/scheisseelektronisches |
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tommysb
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Joined: 24 April 2006 Location: Finland Status: Offline Points: 1036 |
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Posted: 07 April 2008 at 7:38pm |
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Been modelling this in AkAbak.
If you take the chamber behind the driver at 85L, the port as 80cmlong, and with a cross section of 5cmx60cm, you get a resonance at apporx 33Hz ;)
Driver excursion goes a bit nuts about 52Hz with 700W(ish) in, (1.1cm) but then drops right off at the tuning frequency 33Hz, so a bit boost could be applied there, I think that's the idea right?
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Jake_Fielder
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Posted: 07 April 2008 at 7:44pm |
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Im just going to post my plot again to compare:
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Jake_Fielder
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Posted: 07 April 2008 at 7:45pm |
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ARSE now its on a new page....
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Jake_Fielder
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Posted: 07 April 2008 at 7:52pm |
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Hmmm they not too disimilar... the efficiency looks generally the same, the dip @ 130/140 on hornresp seems to be at 70ish on akabak,
Excursion is worrying!
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Jake_Fielder
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Posted: 07 April 2008 at 8:06pm |
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It seems like AkAbak recons the tuning is slightly lower than Hornresp. I think once the folded port has been accounted for, the tuning will be even lower.
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JaKe
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Joined: 14 September 2007 Location: N.E. Wales Status: Offline Points: 684 |
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Posted: 07 April 2008 at 8:34pm |
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Gotta get my head around the Akabak thing and model my cab's, notice the new addition to the latest release of HornResponse about the port being inside the horn?
The excursion looks good to me - making full use of the excursion capabilities of the driver at a reasonable voltage input, should be a good match for a STR3000 with 2 drivers per channel assuming your using something with 14mm + xdam. You need roughly 4 times the power to double the excursion of the driver. JaKe |
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Jake_Fielder
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Posted: 07 April 2008 at 8:47pm |
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30mm p-p i think, brilliant,
this seems to be alright!
im redesigning the shape to unfold the port, so the real life prototype is nearer what i have modeled, i'll be back later with plans,
(but first i have to fix my brothers bands active midtop, it fell over in the wind at a festival and is playing at about 20% volume....?)
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ceharden wrote: