punisher - measuring |
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Jez_Ultra
Registered User Joined: 26 February 2004 Location: United Kingdom Status: Offline Points: 334 |
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Posted: 07 December 2004 at 11:43pm |
I'll hopefully be building a punisher horn nxt week, with a second hopefully following over the christmas period (if i don't get too wasted). I'll post photos of the build once their complete. The first thing I want to do though is to make some decent measurments of the cab. what should i be measuring, how should i be meausing it and what should i be measuring it with. A computer is no problem and I have a pretty good sound card, i've heard mention of special microphones and pre-amps. I'm expecting to run four of these horns off a Inifinite8 (2 x 2400Watts), any thoughts on this anyone?
Jez |
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Tony Wilkes
Old Croc Joined: 02 August 2004 Location: West Midlands Status: Offline Points: 4840 |
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Get True RTA for the comp, a small mixer with phantom power i.e.
Behringer MX802a and a Berry ECM8000 Mic. This will do the response for
you but to do SPL you will need an SPL meter to calibrate your system.
Tony |
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Timber_MG
Registered User Joined: 27 March 2004 Location: South Africa Status: Offline Points: 1454 |
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Try and get a mixer that will give you an output pre-chanel fader &
eq. I have a little Yamaha 4-chanel mono mixer that works a dream in
conjunction with the Behringer ECM8000 running pre-aux. I have had
great results with Speaker Workshop.
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tb_mike
Old Croc Joined: 01 October 2004 Location: New Zealand Status: Offline Points: 2744 |
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Make sure that your levels are both adaquate but not clipping
Make sure that you measure your frequency response at a SANE spl where the mic will be linear eg at 1watt input. Use a couple of programs for variety and repeatability,and interest. Learn how to use/practise Speakerworkshop BEFORE the day - some hate it! The ECM8000 will be nonlinear above 110db probably-it Definately is at 120db according to linkwitz. so SPL measurements wont be happening unless you can find the local car audio SPL meter...(usually linear to 130db but give too high readings above that unless the latest models) Goodluck! Cheers! |
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tb_mike
Old Croc Joined: 01 October 2004 Location: New Zealand Status: Offline Points: 2744 |
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and
http://homepages.paradise.net.nz/sbk1/ssi.htm |
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freddyi
Registered User Joined: 22 September 2004 Status: Offline Points: 936 |
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I like to look at ground plane and above - put mic on floor or ground for GP - outdoors will reveak ripple
mic IMO could go back further than 1M - EV used ~3M indoors - take 1M then further back and if wideband horn/direct raditoar, plot in an arc at center height of horn going in 15 degree increments at distance where it wil typcially be heard. take a note pad to keep track of plots, conditions, obervations if outdoors, mark your mic and speaker spots for future reference as nearby objects such as house will have effect so at least these effects will be constant in future testing. look for noise floor and mains frequency leakage - I'm sloppy and sometimes get 60Hz US plus ~15K monitor watch all levels to avoid clipping - with something like TureRTA , sine overtones can be checked vs indicated level. U can make attempt at two tone sine modulation test - -(google John Allen + modulation distorion) but first - do some harmonic distortion testing with various sine frequencies and low wattage. don't fry anything with sine!!! climbing distortion rate on my PV FH1 will set in by 10 watts re:Mike E. & ECM8000 will have to look at mic overload - am probably OK outdoors on sine seeps and pink noise will be cool to see hi-res on Punisher & Tuba |
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Jez_Ultra
Registered User Joined: 26 February 2004 Location: United Kingdom Status: Offline Points: 334 |
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the ECM8000 is seriously cheap at £39, doesn't really shout precision equipment at me. neither does it's datasheet make reference to any specifictions/standards i'd expect to be linked to a measuement device. spl meters obviously use a microphone so is it just a case of the ECM8000 not being up to the task, or something else. I'd never use a car audio SPL meter, its bound to give a reading of 400dB .
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freddyi
Registered User Joined: 22 September 2004 Status: Offline Points: 936 |
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imo cheap ECM8000 aint' gonna miss much - should be good nuff
from 20-15K - John Murphy (TrueRTA) recommends them (and they're OK for
recording) - one could have 8000 calibrated agasinst a known
standard - but not sure if worth cost - goes way lower flat
than my EV dynamic omnis.
dunno ECM8000 overload point w. 48vdc phantom provided by MX602, etc mixers here's hear-port of my little BP6B box : http://home.earthlink.net/~buddhaboy2/BP6B.jpg |
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Jez_Ultra
Registered User Joined: 26 February 2004 Location: United Kingdom Status: Offline Points: 334 |
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i guess it'll do for the job in hand, i#ll be able to buy another driver instead of spending more money on a mic.
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Timber_MG
Registered User Joined: 27 March 2004 Location: South Africa Status: Offline Points: 1454 |
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An electret capsule will be very, very accurate at LF, so I wouldn't
worry too much about that. One can get the mic calibrated and determine
its sensitivity for true SPL measurements if you want to, but it's
still an invaluable tool in setting up one's loudspeakers (esp. with
LMSs).
Edited by Timber_MG |
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Dave Slater
Registered User Joined: 28 February 2004 Location: United Kingdom Status: Offline Points: 373 |
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can't remember who but someone got their ECM8000 calibrated (thank you if you're reading!) anyways whilst it's exactly right for theirs it can act as a generic guide for us it's an FRD file so you'll have to use SPL Viewer to actually look at it but a fair number of programs will let you import it (speaker workshop does i believe) anyways here you go - ECM8000cal.zip
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tb_mike
Old Croc Joined: 01 October 2004 Location: New Zealand Status: Offline Points: 2744 |
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Interesting.I wonder how much difference there is between various
products of that model,considering its electromechanical its probably a
decent variation.
Cheers! |
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