Compression Ratio for Bass Horn |
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DMorison
Old Croc Joined: 14 March 2007 Location: Aberdeen Status: Offline Points: 1647 |
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Posted: 14 March 2007 at 9:51am |
Hi all,
Does anyone know of any reliable guidelines for appropriate compression ratio's for bass horns please?
Also, what are the likely results of using a high-ish ratio (eg 3:1)
I'm playing around with Hornresp and have what seems to be a useful design, but want to be sure I'm not leaving myself open to bad things happening.
Cheers,
David.
EDIT - corrected typo. Edited by DMorison - 14 March 2007 at 9:52am |
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mark68
Registered User Joined: 07 March 2007 Status: Offline Points: 19 |
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keep in mind that with high compression ratio you could have high pressure in the throat and in the front chamber and so more distortion, someone suggest more than half of SD for the throat but for me I think that maybe could change by using a right driver.
I used the ratio 3:1 with a PD1550 and I have a Bang sound and air overload in the throat but maybe beacause my driver move to much air. if you use hornresp you could see what happens by changing the throat area with the 2 armonic distortion, but there are also other type of distortion like doppler effect bye Marco |
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unclejam
Young Croc Joined: 14 January 2006 Location: United States Status: Offline Points: 525 |
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check mobile enneid's post on win isd and horn response thatt should help some i think meybe i dont kno
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tb_mike
Old Croc Joined: 01 October 2004 Location: New Zealand Status: Offline Points: 2744 |
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mark68 I think you should diagnose the cause of the distortion before attributing it to a high compression ratio - which should only produce distortion if the bandwidth is too high.which on a basshorn,it isnt.
There is an equation to calculate approximate 2HD on a particular horn,but the version I had,was misstyped.Mentioned on audioasylum. eg http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=40053&highlight=throat+distortion+Tomservo&r=&session= |
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mark68
Registered User Joined: 07 March 2007 Status: Offline Points: 19 |
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I know that but for the
2° HD I had used this formula for exponential horns: 2° HD = 0,00173 x (F/FC) x RADQ(PAR/ST) Where : F= generic frequency in Hz FC= Cut off of horn in Hz PAR = acoustic power irradiated in Wac ST= area of throat in mq You will notice that if you have very small ST the 2°HD will rise and of course if you have large bandwidth 2°HD will rise too. There is a table also taken from Beranek that explains this. In Horn resp program is possible to estimate 2°HD |
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JD01
Young Croc Joined: 23 August 2004 Status: Offline Points: 819 |
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A high compression ratio needs speakers able to handle the load (As do big stacks of horns... it all comes down to load). The bang mark68 described could well be the cones outer parts slapping back because of the pressure.... (but it's a PD1550, so this is not THAT likely.... I have seen this on speakers like Kappa15lf, mainly intended for BR use).
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tb_mike
Old Croc Joined: 01 October 2004 Location: New Zealand Status: Offline Points: 2744 |
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Doesnt seem to change much with practical 2:1 and 3:1 compression ratios and two octave bandwidths with hornresp 2HD.
Problem with strong cones,how do you tell without trying one?Apart from building a labhorn. |
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JD01
Young Croc Joined: 23 August 2004 Status: Offline Points: 819 |
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There are some 'obvious' characteristics.... they aren't THAT exact, you can still have a speaker that looks extremely stiff and sucks and you can have a speaker that looks fragile and won't break. But for starters the look is ok. Deep cone, not too hard surround (no hard plastic filled into the surround), and depending on the application (kick or 'infra') a progressiv suspension that kicks in slightly above Xmax (kick lower xmax, infra depending... 'big stack' with similar speakers as kick, 'small stack' with high xmax speakers).
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mark68
Registered User Joined: 07 March 2007 Status: Offline Points: 19 |
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>Doesnt seem to change much with practical 2:1 and 3:1 compression ratios and two octave bandwidths with hornresp 2HD.
Problem with strong cones,how do you tell without trying one?Apart from building a labhorn. < I Don't know with the formula I had different value little more higher. In hornresp with a PD1550 with Eg=63V in the frequency of 150 Hz I see that for compression ratio 1:3 I Have the 2° HD 2,10% I see that for compression ratio 1:2 I Have the 2° HD 1,50% I see that for compression ratio 1:1 I Have the 2° HD 0,70% |
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