"Crossover Design for New Project"

[GM]

So rather than clean it up with passives....clean up the dcx and retain the high tweakibility factor.

Agreed except with my previous horn loading caveat. BTW, is there anyone in the lower 48 that's got a little side business doing this?

GM

[GM]

I had been looking at how to get the same bass reinforcement as AB is trying to do, possibly using a different Altec woofer, ala 421 or similar.

If you mean mid-bass only, then OK, but even in typical HE HIFI/HT apps, MI drivers should be avoided like the plague for bass since they audibly distort due to no real linear excursion to speak of.

GM

[GM]

As regards to the LF cab I was kinda waiting for GM to give me some advice on cabinet.

Well, my vote is for horizontally opposed woofers, but this means a really wide baffle for corner loading which in turn opens up the tuning options to include sealed. Otherwise, a three compartment MTM, preferably a floor to ceiling affair. In either case the goal is to minimize the acoustic center distance(s).

GM

[GM]

Yeah, 9848s used 411s, but the directivity of two vertical 15s should be a reliable constant, and you also have the directivity data from 700Hz-8K for the 288/511E.

All well and good, but it does raise the question, 'why didn't they do it with two 416s'...?

GM demo'd some 9848s I believe, I'm sure he'll have some positive input.

(Feel better soon GM).

True as long as the woofer construction type is the same, i.e. cloth surround.

Thanks, I'd totally forgotten about these plots.

Well, by then, relatively inexpensive high power combined with electronic EQ dictated different driver specs which in turn was allowing the superior sound and lower manufacturing cost of sealed to be used.

Positively bad as a studio monitor. A good high end DJ/party/garage band speaker was my verdict. I wonder if any were ever installed in any of the better recording studios. About all I remember about the horn is how dull it sounded, though if its published response is accurate, I'd never notice it now.

Thanks for the thought, but it's another sleepless night for me.............

GM

[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.

[bfish]

...Bummer, guess if I ever need one of my 515Bs re-coned I'll have to sell them...GM

(OT response, but probably worthy anyway.)

(There may be 2 options for 515s, so you may not be out of luck).

This should be self-evident if one peruses the various driver/kit lists from the 70s thru GPA, but the concept doesn't seem to have widely sunk in, and IMO is at least in part the reason for some of the expressed dissatisfaction with GPA recones. Look at the wide array of kit numbers used in various versions of any given long-lived model on the '75 reference. Any change in software created a new part number. Some may have been from different vendors (Altec didn't make their own cone kits), others used newer materials and methods. The consolidation of all those historical versions into a single "what's available/best choice now" version was a decision that Altec made way back when (see the parts lists from the 80s & 90s). This seems to have been translated somehow as GPA's "fault", which it isn't. It's a practical decision that Altec made, and GPA is stuck with.

Would I like to have kits available (in made-yesterday condition) for all my various drivers? Of course I would, but I have to accept that it ain't any more likely to happen than me getting my 18yo body back. People move on and die, companys get bought and sold, and we make the best of what's dealt us. "Progess" may be subjective, but change is inevitable.

[Panomaniac]

Welcome back GM.

Why? I mean a 288 on a shortened 511 is from an acoustical loading POV about the same as an 802 on a stock 511, so a 500 Hz XO is appropriate.

Is it? Maybe it will do 500Hz, but is it best? Don't have a 511E to measure, but when I measured all the horns and drivers I have, I see the 2nd harmonic shoot up fast under a certain frequency - a frequency directly related to width of the horn mouth. For the 511B that is about 575Hz. (with an 802 or 806)

Still, from a practical standpoint, it would be nice to hear/measure how much lower the 1.4" 511 will play than the 1" version. Or if it's better toward the low end of the range. What was the 511E made for? Better power handling? Or something else?

[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

[GM]

This should be self-evident if one peruses the various driver/kit lists from the 70s thru GPA.........

Which I haven't done, but got this impression from various folk's experience with them. Regardless, this is a subject that I believe needs to be discussed in much more depth than I'm prepared/up for anytime soon, but plan to on Mike's '416 dilemma' thread where it started being discussed if some new, dedicated thread isn't begun in the meantime.

GM