Subject: Center Speaker Recommendations for Main Horn Speakers

[Duke LeJeune]

I saw your reply here https://www.audiosciencereview.com/...s/horn-speakers-is-it-me-or.9633/post-2471637

Unfortunately, one of the two round horns of Marcel’s which I’m selecting-the A460D or A520G2-would be either 18.1” or 20.5” diameter, so even with the bottom of the mouth resting on the cabinet of my 15” midwoofers the drivers would be at least 18” apart. How would crossover frequency and other aspects of passive crossover design compensate for this unavoidable C-C driver distance?

Yeah, imo the placement of your midwoofers on their enclosures wasn't ideal... they LOOK great centered on the baffle, but imo it would have made more sense, from a system-design standpoint, to locate the midwoofers as close to the top of the baffle as reasonably feasible.

With an 800 Hz crossover, the center-to-center vertical distance would be about 1.07 wavelengths. So that's a little bit more than ideal, but on the other hand the ear's vertical resolution is not very good in that frequency region. I don't think it's a big deal. I would not push the crossover frequency lower than your driver/waveguide combination is comfortable with for the sake of reducing the wavelength of the vertical spacing.

If you are going to use an active crossover, which will allow you to dial in delay for each driver as needed, you could allow the front of the waveguide to stick out beyond the midbass enclosure enough for you to lower the waveguide a bit, so that it overlaps the upper two or three inches of the midbass enclosure. This might even be feasible with a passive crossover.

The steeper the crossover slopes, the smaller the frequency region shared by both drivers, so the smaller the frequency region where there is a "pinch" in the vertical polar response. That would be up to your crossover designer, and there are multiple factors to consider, so I suggest letting him juggle the tradeoffs as he sees fit.

And how would this determine optimal listening distance?

I don't have a formula for this. Extrapolating from designs that I do have first-hand experience with, and without the waveguide overlapping the midbass enclosure or using a very steep crossover, I guesstimate that your minimum recommended listening distance would be about five feet, and anything beyond that be fine as well. This is assuming your ears are at or near the height the crossover is designed for.

If you also want to have optimal sound when standing, you can probably decrease the minimum standing distance by aiming the speaker upwards several degrees, or perhaps by elevating it so that your minimum sitting distance is at the bottom of the vertical window wherein everything sounds good.