| The Electrovoice 12trxb in a folded Voight pipe. Each driver has its own input, and each tweeter has a "L" pad for level control. There is a total of five drivers in each speaker, two 12trxb's, one SP12B on top. I don't really need the extra tweeter on the bottom 12trxb on the front, it is usually turned all the way down. This is a prototype speaker and thus has no finish, and each drivers wires is accessible from the back of the speaker.This makes a variety of impedence configurations, and by-amping or tri-amping possible. I measured the efficiency at 105 dbs 1w/1m, and will measure this agian once all the tweaking is done to the speakers. Each driver is rated at 96 dbs 1m/1w. |
| You will notice (right) both "L" pads and the vent of the Voight Pipe are on the front. I thought because of the size of each speaker, I would no doubt be keeping them against a wall most of the time, so this would make the positioning of the speaker less critical having the vent in the front, and the "L" pads easier to access. Although having the pipes vent in the back could be further advantageous if you were going to stick them in a corner. |
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| Here (right) you get a view of the simple labrinth inside that makes the tuned quarter wave pipe. The pipe is approximately seven feet long, a little more if you use standard methods. I made blanks for the vent, and took measurement with the vent covered, or a sealed cabinet. The bass response dropped way off, so the pipe is doing its job very well. I can tune how I want the cabinet to sound by covering up part of the vent, this will extend my bass and lower a peak I have at 60 hertz. At this point I see no need to stuff the cabinet as I don't have the slightest bit of boomy effect of bass. It is tight and clean, down to 40 hertz, and slopes somewhat gradually compared to my other straight VP's. If I close half the vent off I have absolutely no peaks in the bass response, surprisingly smooth, not what I expected. |
| The above frequency plot shows the room coupling of the speakers, the two peaks are less noticable when measuered at one meter. Likewise the frequency extention in the high region is better when measured from near field. I have done a few tweaks (foam around whizzer) that have tamed the frequency plot, but still it is very good as far as speakers go in a typical room. |
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| Electrovoice 12trxb's in a Voight Pipe |
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