here's a few pix of the process, apologies for the droid's lackluster camera:
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heh...just noticed my hat lying on the driveway in the first pix, my trademark carbon fiber bowler...Made it myself about 5 years ago, and it has literally saved my life when a par64 came to visit me from the trussing above a stage i was on.
looks real good,nice job
btw you might want to delay the outer subs a bit,for better dispersion of the upper bass. 🙂
btw you might want to delay the outer subs a bit,for better dispersion of the upper bass. 🙂
Oops, no safety lanyard 🙄...
Great looking bowler and subs!
Blurred vision = probably over 130 dB...
Looking forward to some measurements, would be interesting to see what the distortion looks like at various drive/excursion levels and frequencies.
Art
How do they perform in the room? Do you have Enough power for all 12 drivers?
Why does one driver look way out of place in the 7th pic?
Why does one driver look way out of place in the 7th pic?
"Why does one driver look way out of place in the 7th pic? "
The drivers look as if they are mounted like the drawing in post #1, push-pull.
The drivers look as if they are mounted like the drawing in post #1, push-pull.
There did end up being a change in power amplifier. Rather than the LabGruppen I originally spec'd the club decided to gamble on savings & bought 2x Peavey IPR2 7500, so one channel of amp per cab yields (officially) a 4ohm load & develops 2044 WRMS/box. As existing amp rack space was just gone I built an ugly little plywood rack which I mounted to the ceiling above the SR sub, nested between the rafters. I left about 1/4" breathing room betwixt the rack & the sub 😉 Impressions so far are that if I allow the xover limiting to lightly tickle the DDT it's just the right amount of juice.
mRgSr- good eye, one of the Epic12s arrived without the rubber mounting gasket, so that driver was wired & placed in the cabinet to protect it from drunken children, but not yet mounted & the rig wasn't online until the next day when Parts Express got the gasket to me.
OllBoll- They are never intended to move again, so the question is 'How did we move them'...4 guys, two sets of 'forearm forklift', 2 moving dollies, and a flatbed trailer with cardboard between them to reduce finish damage in transit 😉
weltersys- I am looking forward to having a chance to do some final tweaking & measurements, looks like it'll be a few weeks til I get caught up enough. Until then they'll have to live with the seat of the pants alignment I did on install, which is workable though not ideal. Same company & different venue is what has me tied up now, so at least the reason for the delay is fully understood by them & the rig is a massive improvement from what it was as it stands. BTW, distortion measurements haven't been part of my normal procedure, and they should be...any suggestions for a process on a tight budget?
epa- Did that some in the rough set-up, not pretending I got it right yet though. The engineer running it this weekend with bands (I was elsewhere) felt more comfy attenuating the wall subs & primarily using the one under the stage. I suspect that to be a combination of some minor errors in alignment coupled with his familiarity with that config. I'll be looking into that when I finally get time for thorough testing & tweaking.
mRgSr- good eye, one of the Epic12s arrived without the rubber mounting gasket, so that driver was wired & placed in the cabinet to protect it from drunken children, but not yet mounted & the rig wasn't online until the next day when Parts Express got the gasket to me.
OllBoll- They are never intended to move again, so the question is 'How did we move them'...4 guys, two sets of 'forearm forklift', 2 moving dollies, and a flatbed trailer with cardboard between them to reduce finish damage in transit 😉
weltersys- I am looking forward to having a chance to do some final tweaking & measurements, looks like it'll be a few weeks til I get caught up enough. Until then they'll have to live with the seat of the pants alignment I did on install, which is workable though not ideal. Same company & different venue is what has me tied up now, so at least the reason for the delay is fully understood by them & the rig is a massive improvement from what it was as it stands. BTW, distortion measurements haven't been part of my normal procedure, and they should be...any suggestions for a process on a tight budget?
epa- Did that some in the rough set-up, not pretending I got it right yet though. The engineer running it this weekend with bands (I was elsewhere) felt more comfy attenuating the wall subs & primarily using the one under the stage. I suspect that to be a combination of some minor errors in alignment coupled with his familiarity with that config. I'll be looking into that when I finally get time for thorough testing & tweaking.
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How do they integrate with tops in the midbass, and do the tops even come close to keeping up with them....?
Distortion testing is easy with some measurement systems, but still can be done the hard way by looking at a sine wave signal and the resultant harmonics on an RTA, subtracting the difference in dB, then calculating the distortion percentage.
For " close enough for rock and roll" purpose I calculated distortion % on the calculator page below, the harmonic with the highest level pretty much determines THD, the contributions added by lower harmonics generally add only a fraction of a percent to the highest harmonic.
In the two examples below a Lab 2x12" push-pull bass reflex enclosure is compared to a Lab 2x12" Keystone tapped horn using a 49 volt sine wave input at 35 Hz and 50 Hz.
At 35 Hz, the push-pull (PP) third harmonic (105 Hz) is 20.9 dB below the 107.9 dB fundamental, around 8.9% distortion, the tapped horn (Key) second harmonic (70 Hz) is 30.5 dB below the 114.5 dB fundamental, around 3.2% distortion.
At 50 Hz, the push-pull (PP) third harmonic (150 Hz) is 22 dB below the 109 dB fundamental, around 8% distortion, the tapped horn (Key) second harmonic (100 Hz) is 16.4 dB below the 119.8 dB fundamental, around 15% distortion.
The difference in distortion at high drive levels gives different sub designs quite a different sound, even when equalized the same.
In post # 12 the distortion and output of Lab 12 and a BC18SW115-4 are compared in the same cabinet:
http://www.diyaudio.com/forums/subwoofers/185588-keystone-sub-using-18-15-12-inch-speakers.html
When doing sine wave testing like this you must keep the individual tests short and allow time for cooling between each test, the higher drive levels I used would burn the voice coils if applied for extended time periods.
Art
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Thanks Art, that's intuitive enough that I should be able to zap off some useful data about distortion when I get a chance to tune & test.
Thank you for those graphs, they look like a good illustration of the distortion differences of Push-Pull setups 🙂
Cool, as a suggestion type up all the frequencies and voltage you plan to test prior so you can copy and paste them in as you go, and keep track of where you are.
The only time I burnt a speaker during distortion testing was when I was manually entering, made a mistake, deleted, re-entered, oops...
Although this way of testing is a PITA, it does show more information than the usual distortion tests which only show second and third harmonics- some times even the fourth or fifth harmonic can be objectionable, since they show up where our hearing is far more sensitive than in the LF range.
Art
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