"Crossover Design for New Project"

[Panomaniac]

Don't worry about the 4 ohm thing, in fact it's good if you're driving it with solid state.
The crossover will be done on the real impedance of the drivers, not just a nominal 4 or 8 ohms. And a 4 ohm load saves you money on inductors.

How much room do you have for the bass bins? You know I'm thinking Onken W. That would be killer, but takes up a lot of room. Where you going to do the side by side thing, or one up above the other?

Thanks to bfish for the link, it's a help. Crossover was 700Hz, that's good news and easy to do.

Sure, I can send a shopping list of measurement gear. You ready to take the plunge?

[bfish]

Horizontal woofs would "flip" the directivity, necesitating a different XO point (among other things), one that would defeat much of the reason for using a 288.

[Panomaniac]

Why, wouldn't the horizontal woofers have a wider, shorter pattern? What was the monitor with 2 12s and the 811 horn?

Bottom line, what's the polar pattern of 2x15 and the 511 in the octave around 700Hz?

[bfish]

I guess I saw that coming, I was typing the following when you posted;

More on that...

A single woof radiates a fairly uniform, round pattern, which narrows with increasing frequency. However, when you put two in close proximity, the pattern becomes an ellipse, or for interpretive purposes, rectangular. The pattern is just the opposite of what your intuition would suggest though, with woofs stacked vertically, the pattern is wider horizontally, and vice versa.

This is borne out in the 9848 directivity plot I linked to. At 500Hz, the pattern is 135 degrees horizontal, and 60 degrees vertical. By the 700Hz XO point, the horizontal has narrowed to 90 degrees, and begins to blend with the 511 horizontal pattern.

So, if you flipped the woofs to side-by-side, the pattern flips too. You can see by the directivity plot how that won't meet the 511 polars at a reasonable frequency, with the woofs doing

xxx
xxx
xxx

and the horn doing

xxxxxxx
xxxxxxx

Yeah, Altec did side-by-sides too, but with a specific application in mind for which it worked. They also incorporated some directivity "steering" (via phase offset) into the design as well.

[GM]

Horizontal woofs would "flip" the directivity, necesitating a different XO point (among other things), one that would defeat much of the reason for using a 288.

Defeat ???

GM

[bfish]

Yeah, the power-hog aspect of parallel woofs is exactly why I suggested impedance matching the pairs.

4 box MTM meant a box for each 416. I figured whether or not you boxed the 511s in the middle was an aesthetic matter.

By "defeating" the reason for a 288, I had in mind the 288 advantage of being able to lower the XO point, which seems to conflict with a directivity match for horizontal woofs. IOW, if you're crossing much higher than 500Hz, why not take advantage of the extra BW a small format offers and fuggetabout the PITA tweets?

However, I hadn't considered corners. When the room placement limits everything to 90 degrees, horizontal/low XO makes sense.

[GM]

4 box MTM meant a box for each 416. I figured whether or not you boxed the 511s in the middle was an aesthetic matter.

By "defeating" the reason for a 288, I had in mind the 288 advantage of being able to lower the XO point, which seems to conflict with a directivity match for horizontal woofs. IOW, if you're crossing much higher than 500Hz, why not take advantage of the extra BW a small format offers and fuggetabout the PITA tweets?

However, I hadn't considered corners. When the room placement limits everything to 90 degrees, horizontal/low XO makes sense.

Ah! I was viewing it as a single speaker system. Well, there's sonic reasons for boxing in the horn if XOing down near/at the horn's lower usable limit.

Hmm, long ago I worked out 'close enough' (for me anyway) polar matching XOs and came to the conclusion that dual horizontally opposed 15" drivers were a better match to a 511/500 Hz than vertically same as the 9844 Vs Malibu for the 811/800 Hz. IOW, all else equal, going 'wide' dictates a lower XO point which brings us back to our point of why 'waste' a 288 on a higher XO point in a non-prosound app unless you have a low enough efficiency LF system that you risk over-driving it below the XO point?

Actually, assuming the speaker is designed to fit the corner, letting it do the pattern control negates the horizontally opposed driver layout's 'virtual corner' advantage, but there's still the acoustic center differences that makes it the 'no brainer' choice for me if space permits.

GM

[bfish]

...long ago I worked out 'close enough' (for me anyway) polar matching XOs and came to the conclusion that dual horizontally opposed 15" drivers were a better match to a 511/500 Hz than vertically...

Based only on the DI plot for vertical 15s below, it appears the opposite to me. At 500Hz, the woofs are at 60 degrees (vertically, which becomes horizontal if you flip them)...

IOW, all else equal, going 'wide' dictates a lower XO point...
GM

I'm not getting it. Not trying to be obstinate, just trying to understand.

[GM]

Understood, when I saw that plot I could see it coming round the bend........... Frankly, I think the plot is another of those many marketing errors we found/joked about some years ago, but will take another look at it when I'm not so preoccupied.

GM