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Jez_Ultra View Drop Down
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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 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tony Wilkes Quote  Post ReplyReply Direct Link To This Post Posted: 08 December 2004 at 8:34am
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timber_MG Quote  Post ReplyReply Direct Link To This Post Posted: 08 December 2004 at 3:34pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2004 at 6:57am
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2004 at 6:58am
and

http://homepages.paradise.net.nz/sbk1/ssi.htm


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freddyi View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote freddyi Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2004 at 4:24pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jez_Ultra Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2004 at 8:44pm

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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Post Options Post Options   Thanks (0) Thanks(0)   Quote freddyi Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2004 at 8:58pm
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 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jez_Ultra Quote  Post ReplyReply Direct Link To This Post Posted: 09 December 2004 at 10:40pm

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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timber_MG Quote  Post ReplyReply Direct Link To This Post Posted: 10 December 2004 at 7:51am
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 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave Slater Quote  Post ReplyReply Direct Link To This Post Posted: 10 December 2004 at 10:46pm

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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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 11 December 2004 at 1:44am
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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