Altec 802-8G fs

[Old Guy]

Interesting I didn't know that.

If that horn / driver combo will do 500hz that would be great. I don't like running those large woofers to high. I'll have to experiment but assume I'll compromise as best I can between the woofers / drivers - I'd planed to go active and I have a Pass Labs XVR-1 which is very flexible.

It will do 500. Whether you like the sound or not is a personal decision. I don't.

The 511 unloads at 485 Hz if I recall. Pretty skinny margin since parts in the crossover can be off by 20%. Of course DSP removes that possibility.

[GM]

Hmm, please define 'unloads' since F6 is more like ~400 Hz and its cutoff is right at 212 Hz since it's designed to do 300 Hz for the 730C driver.

There's an awful lot of mis-understanding/information re compression driver power handling in general and the 802-8G in particular, but GPA's Fs for it proves it can handle anything the earlier 802s can.

WRT how it sounds, that has as much, if not more, to do with the horn it's attached to than the driver, i.e. it's 'voiced' [entire BW is shifted a little higher] for the small Mantaray and 811, so more CD horn EQ is required for the 511 plus more mouth damping to ~delete its 'honk', reflections back to the throat and 'let through' the 8G's superior HF response. Apparently the plastic phase plug doesn't handle the 511's relatively strong mouth reflections hammering away at it too well.

Factor in there's no need in a typical HIFI/HT app for high power, the driver's 8 w rating is all that's needed, so plenty of Xmax left. Worst case is someone may need to add loading caps to fill a 10 car garage with a pipe organ symphony.

GM

[Old Guy]

Hmm, please define 'unloads' since F6 is more like ~400 Hz and its cutoff is right at 212 Hz since it's designed to do 300 Hz for the 730C driver.

There's an awful lot of mis-understanding/information re compression driver power handling in general and the 802-8G in particular, but GPA's Fs for it proves it can handle anything the earlier 802s can.

WRT how it sounds, that has as much, if not more, to do with the horn it's attached to than the driver, i.e. it's 'voiced' [entire BW is shifted a little higher] for the small Mantaray and 811, so more CD horn EQ is required for the 511 plus more mouth damping to ~delete its 'honk', reflections back to the throat and 'let through' the 8G's superior HF response. Apparently the plastic phase plug doesn't handle the 511's relatively strong mouth reflections hammering away at it too well.

Factor in there's no need in a typical HIFI/HT app for high power, the driver's 8 w rating is all that's needed, so plenty of Xmax left. Worst case is someone may need to add loading caps to fill a 10 car garage with a pipe organ symphony.

GM

Hi Greg-
In all honesty I'm not as well equipped for this discussion. I'm operating on info gleaned from the engineering guys when I worked at Altec. Their attitude was that operating the 511 down to 500 wasn't a good idea. That's where I got the 485 Hz figure.

I have used the Community RH-90. It's a 400 Hz flare rate horn. In A/B situations it sounds much better than the 511 at 500 IMHO. On the 511 it sounds like the driver is struggling compared to the RH-90. There are other possibilities for this- I don't care for the throat design of the 511. But I've operated on the above info.

[Mercury3]

Thanks guys. I have not obtained the 511's yet so if anyone has a better choice I'm wiling to look into it. I'd looked into a wooden horn but to damn expensive.

Long story but when I had my Model 19's many years ago I'd experimented by adding a high efficiency midrange in a separate box on top of the cabinet with 350hz crossover. It made a huge huge improvement. As good as the 416's are performance drops over 500hz and no way do they sound good up to the 1200 hz stock frequency.

I had a friend who purchased some Model 19's based upon hearing mine and she was quite disappointed with hers in comparing to mine. She kept them for a few years and then traded them for some Kef's with better midrange.

I'll have to experiment and probably reach a compromise crossover as to which sounds worse/better at what frequency. Maybe it'd be okay a bit above 500hz but I'd like a horn that goes that low just to see and in case I can at least get closer to 500hz.

Mark

Oh edit to add - Does anyone have any ideas to the dilemma I mentioned in my other thread (MLTL Thread)? If I go with MLTL design (which I'd like to) where can I put the horns with such tall cabinets?

[GM]

Absolutely no reason the 802G can't be used like any other 802. Tangerine phase plugs do not need a higher crossover.


Bear in mind the mass of air in the horn. That mass will load the driver, and yes, fs will drop. GM likely would be better at explaining.


That air load is why drivers blow when operated below horn cutoff. The diaphragm isn't adequately loaded.


Small format Altecs IMHO sound better at 800 or 1200. If I wanted to go to 500 I would use a 288.

Not really, in short, you 'nailed' it; acoustically a horn is a severely over damped 'pipe' with a large air mass 'slug' hanging out both ends and when an under-damped ['weak' motor: high Qes/Qts] air pump [BP4 driver] is attached we get a balanced system over widest practical BW when designed right.


Now this 'pipe' has a 1/4 WL fundamental [~190 Hz IIRC for a 511], which means 3/4 of this ~ 22.7" dia. sound 'bubble' is attached to its terminus [mouth] outside the horn and since it's tapered to an acoustically tiny throat, this puts lots of pressure [acoustic enertance IIRC] on its 'weak' motor, lowering Fs.


But what about smaller horns/cutoffs > Fs with the attendant smaller 'bubble' air masses? Again, it's the throat pressure, i.e. the driver is designed for largest horn, but all the throats are designed to combine with the driver's low pass filter chamber connecting the two together to get the desired preloading as shown in this set of comparisons: Altec 511B horn compared to the GPA MR931


Yeah, prosound drivers are rated for PROSOUND apps, so unless you need > ~8 W peak, 500 Hz/2nd order is fine. The horn [especially if sectoral] and/or the amp is normally the reason for it not sounding as good as a higher XO point. Of course no manufacturer will ever admit to this for obvious reasons, so propagate this fallacy.


As for personal preference, for sure, a larger driver/throat will sound more 'full', same as comparing two different size point source drivers over the same BW/amplitude, though I fooled more than a few folks with some DIY ~1803 size WGs, each loaded with an 802 & 802G with the 802 low passed to create a 1.5 way horn, which netted a slightly larger effective diameter diaphragm/motor than a 288 for performance in the ~300 - 3 kHz BW.


The RCA style WG with foam damping was so 'transparent' performing relative to any prosound horn that I could disconnect the 802 and boost the 'G' to compensate and only the few prosound guys could tell the difference.


GM

- - - Updated - - -

Hi Greg-
In all honesty I'm not as well equipped for this discussion. I'm operating on info gleaned from the engineering guys when I worked at Altec. Their attitude was that operating the 511 down to 500 wasn't a good idea. That's where I got the 485 Hz figure.

I have used the Community RH-90. It's a 400 Hz flare rate horn. In A/B situations it sounds much better than the 511 at 500 IMHO. On the 511 it sounds like the driver is struggling compared to the RH-90. There are other possibilities for this- I don't care for the throat design of the 511. But I've operated on the above info.

Greets!


Wasn't sure, hence my Q. If your 'time' began after high DF PP tube amps became the norm, then being prosound centric they were quite right, but note they continued using 500 Hz in consumer gear up till parts consolidation dictated only prosound XOs.


No doubt about it, 'BIB' [bigger is better] rules! 'No replacement for displacement', etc..


Unfortunately, like most systems, speaker systems are a bunch of compromises, so one has to choose what's most important performance wise and still meet the size/budget constraints with the latter two, especially the last one, being the dominant ones.


In this respect and considering the times when these horns were designed, they are marvelous, well thought out designs that still please many after going on 70 yrs now and precious few understand how it does, so as time permits I'm going to 'walk' through it using this exaggerated scaled measurement Tom Danley did for me and yet to get around to it: 511 - TD measurement | A 16 ohm (~matching impedance), 1 mfd… | Flickr


Actually, using Klipsch's 'rubber throat' [conical horn section] is what makes it as good as it is WRT meeting the high speech intelligibility requirement.


GM

[Mercury3]

This is all so interesting. Thanks!