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RE: Getting EV1823's and ST350's in phase..Ping Paul E.

Posted by Paul Eizik (A) on June 4, 2014 at 16:02:57

In Reply to: RE: Getting EV1823's and ST350's in phase..Ping Paul E. posted by Geary Lyons on June 3, 2014 at 19:09:09:

Geary

A 3500 Hz sound wave is about 3.8 inches long.* The highest pressure (using a sine wave example) would be at the 1/2 wave point, or at about 1.9 in. So with the drivers reverse wired, you would see a null at about 2 inch intervals. You want to pick the null which is closest to the area where the drivers diaphragms are aligned in the vertical plane as seen from the side. This seems unlikely to be at a spot that near to the point where the mid and tweeter horns mouths are that close to each other, though it may be an improvement over just lining up the mid and tweeter mouths as previously.

A word about time alignment^tm, which is a copyrighted term, so I tend to use the phrase "phase alignment". Ideally you would check the alignment by feeding the drivers with an impulse signal and observing that their outputs are arriving at the listening position at the same time, with a test microphone into an oscilloscope. Using the reverse polarity null test is an easier way to approximate this. Either way the goal is to get the tweeter and mid output transients to arrive at the listening position with minimal delay between them. The rules are different between a speaker for home listening and a PA rig, though the equipment is often the same as is this case. In a PA rig you don't want a narrow sweet spot, and it's acceptable to have a rather vague stereo image as long as the coverage is acceptable. In the home you want the speakers to have a good stereo image with discreet image localization, and with broad coverage being secondary to this. In the cases of some current high end recommended components in well treated rooms, the off center coverage is non existent! Most Stereophile/TAS reading audiophiles seem oblivious to this, though they will patiently wait for the sweet spot at a demo, where half the orchestra does'nt disappear anymore.

Anyway the point is, try it both ways with music you like. With the drivers aligned in phase, the imaging will be better, with a stronger center phantom image between the speakers, and better instrument localization. The system will also sound more coherent with the drivers blending better. The whole "soundstage" thing has gotten blown out of proportion in recent years in my opinion, and most audiophiles seem oblivious to the fact that a live symphony orchestra dose'nt image all that well compared to some of the "one seat wonders" championed by the glossy magazines. Don't forget that moving the tweeter back and forth will change it's level, and you need to compensate for this with a L-pad. A nice female vocal is a good test, as the female voice bridges the area between the mid and tweeter. The Wail'n Jennys "One Voice" is my current fave test track, as the 3 part harmonies come in one at a time. Let us know how it goes.

Paul

* 13,500/Freq. in Hz=wavelength in inches.

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