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mt102’s + phase plugs |
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roborg 
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Joined: 05 July 2004 Location: United Kingdom Status: Offline Points: 1026 |
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 Topic: mt102’s + phase plugsPosted: 30 October 2004 at 10:31pm |
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Heres a first plot of what they do....
I'm gonna try to calibrate the mic i'm using better etc... But i'm pretty pumped 
funny hole @900hz, maybe the rear chamber or the room i'm, testing in? |
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What I cannot create, I do not understand
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Timber_MG
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Posted: 30 October 2004 at 10:40pm |
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Hey roborg
Good to see that your project has turned out so well for you. That resonance at 900 might well be a room artifact or some form of resonance in the horn/rear chamber. I take it the neighbours are loving you all over again? How about a plot off-axis? should be 6dB down at the angle and frequency you cross over to the horns 3 kHz?) for a perfect match. Martin |
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freddyi
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Posted: 30 October 2004 at 11:50pm |
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is 2.26v Ok with most soundcards?
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tb_mike
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Joined: 01 October 2004 Location: New Zealand Status: Offline Points: 2744 |
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Posted: 31 October 2004 at 4:45am |
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Wow Amazingly flat! Speakerworkshop works too(free) once u have a jig
http://www.geocities.com/adrian_mack/homepage.html Cheap version of RTA or 1/3 octave smoothing?
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tb_mike
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Posted: 31 October 2004 at 4:46am |
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roborg
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Posted: 31 October 2004 at 5:39pm |
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Ahh yeah i should have really point out the sound card is prolly clipping the tops off the 250-3K or so.
I'll get it set up in a less noisy place so i dont have to turn the volume up so high to get an OK measurement. Akabak reckons i should get a pretty good hump at around 1-1.5k. I think the dip at 900hz was prolly a reflection off the top & bottom shelves of the speaker (the mic was placed very near-field 
I'll get down & do alot more tests now its sunday (and quieter!) Get some off-axis plots too (it's not much extra effort to move the mic 2 feet when you've had to lug the speaker & amps around! cheers Rob |
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What I cannot create, I do not understand
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freddyi
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Posted: 31 October 2004 at 7:16pm |
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I run stuff 'kinda' hard at times but with EM800 mic and MX602A
mixer can get pretty good S/N ratios with like 600mv imput to
soundcard - you can gleefully burn speakers up and not feed too
much signal to computer soundcard - only place whre ahv about
fried was trying ot use TrueRTA for Z - don't do this.
too much input will flatten out response and add much distortion - good to look at external (or pc generator sine) sine through the mixer so overtones <<1% and look at input level - theres a point where can tell where overload is doin' its thang and harmonics rise out of proportion. love those horns Rob! |
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roborg
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Posted: 31 October 2004 at 7:37pm |
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I took the volume down a bit & moved the mic further away too (background noise was fairly constant today, not too much traffic)
anyway heres some better results... To be absolutely honest i'm a bit suprised the on-axis response is as flat as it is. I've done a little experimentation but not as much as i've had to with other cabs in the past to get much less bandwidth & much cr**er results than this! It does sound OK with no EQ when crossed at 200 & 3K though, sothe response has to be pretty flat. Maybe Rog's basic cab designs are like 'golden' prototypes & no matter what you do to them, they are always good
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What I cannot create, I do not understand
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freddyi
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Posted: 01 November 2004 at 1:47am |
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ah - thats "HiFi" - NICE JOB
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freddyi
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Posted: 01 November 2004 at 2:06am |
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hey Rob - are those phase plugs effectively "obelisk" back to driver? -
do they meet/attach a flat-square throat plate? - is there any "cup
now involved vs dustcap? - - one slick dancestack! |
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tb_mike
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Posted: 01 November 2004 at 4:16am |
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Id keep the spl lower in order to ensure the mic is operating linearly,+ nothings clipping electrically Bear in mind that dips etc,if their less than 1/3octave wide wont really be noticed
The mid cab looks quite professional! |
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roborg
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Posted: 01 November 2004 at 2:58pm |
The throat horn profile is now really similar to the throat of the porn horn, the 15x15cm square section horn smoothly progresses to an annulus at the speaker cone, i drew some x-sections & have updated that page see bottom of page The thing i'm worried about is whether the cone will survive such high compression, only time will reveal that! Thanks dude! I hope it survives the anticipated onslaught of beer, with such high compression any beer going into those mids is gonna be spat back out supersonicaly heh! Unless it's stella of course 
cheers, Rob |
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What I cannot create, I do not understand
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freddyi wrote: