Altec drivers for 511B horns?

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Hi,

Is there a generally accepted pecking order for the Altec drivers for the 511B horns ?

Searches suggest the 802 series are better than the 808, but there are loads of different versions and its getting confusing.

My application would be running 500Hz up over 15" midbass horns. I also have some beyma 380 cd's on a 90 x 40 horn that could do tweeter duties if need be. XO is behringer digital, slopes from 6dB to 48dB available, as is PEQ.

Thanks,
Rob.
 
Evenharmonics said:
I use 802D.
I'd love to hear from someone who's done side by side comparison with 902-8B.


I think my brother might have one in the trunk of his car! It's the hammertone green as well as the 511B that it's attached to.

I'll have to measure the VC with a multimeter and see if it's any good still, then try it out on my system.


BTW, he has this horn/driver in his trunk because one of his friends wants him to sell it on eBay for him, but still hasn't brought my brother the second horn/driver yet. It's a shame really, because he also has the two A7 cabinets as well, but they were sitting in 2 feet of water and are beyond repair. Hmm... I'll have to check and see if the woofers and xover s are still in them. :confused:
 

GM

Member
Joined 2003
Evenharmonics said:
I use 802D.
I'd love to hear from someone who's done side by side comparison with 902-8B.

Greets!

I've A/B'd them on much modded 511s way back when, but the 802D has more bottom end and rolled off top end compared to the 902, which among other things was redesigned for a flatter response and more top end 'air' when driven with a vanishingly low output impedance (SS) amp. The trade-off is a higher XO point is required with the 511 for best performance.

Tom Danley measured 802D/stock 511:

GM
 

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RobWells said:
Hi,

Is there a generally accepted pecking order for the Altec drivers for the 511B horns ?

Searches suggest the 802 series are better than the 808, but there are loads of different versions and its getting confusing.

My application would be running 500Hz up over 15" midbass horns. I also have some beyma 380 cd's on a 90 x 40 horn that could do tweeter duties if need be. XO is behringer digital, slopes from 6dB to 48dB available, as is PEQ.

Thanks,
Rob.


Greets!

Got a little more time today to respond........ 807, 808 (~2.2 dB more eff.) prosound drivers are 806/802 HIFI units with high power Symbiotik diaphragms, so should only be used when XOing to a super tweeter in a HIFI/HT app due to its harsh, excessively rolled off top end. Indeed, some Altec 'faithful' contend that this one is preferred since it sounds a bit more the 1.4" large format driver down low, but I never tried it, so can't offer an opinion. Makes sense though and its usually available for much less than the various HIFI units.

FWIW, mine are '808' with Altec's original ultra-light diaphragms and the only way I'd consider upgrading is with these in Tangerine phase plugged 802-8Gs, though even when I still had good HF hearing the difference was subtle at best, so would be a complete waste of time/$$ for most adult males and I learned the hard way that a typical female's superior HF hearing prefers a rolled off response if not ultra clean with a sharp HF cut-off above ~18 kHz.

GM
 
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Joined 2004
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Aloha GM.

Thanks for the graphs. That 511 graph by Danley caught my eye because of the kink in the plot that is noted as 20" Baffle. With my 811s rear mounted flush on a 24" baffle there is a mighty kink at 900Hz. Peak-Dip-Peak. Fairly narrow.

That's one of the things that wrapping towels around the mouth edge helped, eliminated, actually. And it took towels top and bottom to cure it. So my guess is there is something going on between the concave outside horn shape and the baffle.

The graph is posted below. No, the response is not that flat, it was normalized to the FR with 2 towels. You will see the results with 1 and none, also. (ignore the low end, that's room noise)
 

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panomaniac said:
Aloha GM.

Thanks for the graphs.

So my guess is there is something going on between the concave outside horn shape and the baffle.

Greets!

You're welcome!

Yes, there's standing waves between these huge protrusions and any acoustic or hard boundary. I like Lee T. Neidow's trail pad foam horn extension variant to control both horn and direct radiator off-axis response. Zero SAF, but he's like me and doesn't give a toot. ;) NHT uses (used?) a foam strip variant on one side of their tweeters, mids of some models: http://nhthifi.com/2006/images/about/33lg.jpg

GM
 
Downloading now GM.

While I've got peoples attention here, my 511's have had the centre brace removed but I've read thats a good thing. I've just got to grind out the remnants of the welds and fill / sand. The previous owner also removed the 'rubber gunk someone had put between the vanes' Is there a special type of hard setting rubber etc or can I use bathroom sealant to put it back in.?

Cheers,
Rob
 
511B center brace

That brace placed stress on the top and bottom of the horn to prevent the metal from "ringing like a bell". Whoever removed them did you no favor. Whoever said it is an improvement is tone deaf.

Assuming you are not an artist with a MIG welder, and you want to restore the beneficial effect of that brace, cut a piece of 1/4" steel rod that is about 3/32" longer than the distance between the top and bottom at the center of the location of the original brace. Grind each end to a SLIGHTLY rounded point. Drill a 1/8" hole (with a long bit) all the way straight through the horn at that point. Wedge the piece of rod into those holes. It should not be easy to do and should be tight when seated. You should be able to hear a huge difference in the resonant tone of the horn ( tapping it lightly with a small hammer) after replacing the brace. When done, seal around the holes with some JB Weld, or equivalent epoxy.

We used to add braces like that to the big aluminum radial horns from Altec and JBL, as a matter of course.
 
Best small Altec drivers

My plane wave tube doesn't lie. The 802 was the finest small driver that Altec ever produced and maybe the best 1" driver ever built by anyone. (all aluminum (not symbiotic) diaghram)

Yes it 's power curve is not as "flat" as the later 900 series, which used the "tangerine" diaghram. But, the 802s smoothness of power response and phase response is almost textbook. A simple R/C equalizer is all that is required to make an 802s top end sing sweet and strong with less shrillness than a 902 on a modern horn. Since a 511B horn is designed to beam the high end and spread the midrange, you definitely do not want to load a 902 on one, if you value a balanced sound. It will be BRITE!

The "tangerine" by the way, is a travesty. It achieves its flatness by using progressive phase cancellation to reduce midrange efficiency. The driver isn't brighter, it just has wimpier mids than an 800 type with the tradition annular ring sectoral horn phase plug design.

I'm sure the boys who developed all that stuff at Bell and Westinghouse rolled over in their graves when Altec introduced the "tangerine".
 
... a higher XO point is required with the 511 for best performance.

That's probably a good idea for the tangerine 802g - 511 combo, too. Or perhaps just forgo using the 511 altogether, and find a suitable Hi-Fi horn to mate with a 15".

Here's a few measurements I made:

* Waterfalls of an 802g - 511 combo--
ALTEC 802g - 511b


* Waterfalls of the same combo + Zilch 19 network (designed to boost the upper end)--
ALTEC 802g - 511b - Z19 net


I no longer have the drivers, but if I were to get another pair of Altecs, I'd seek out a horn that both sounds good and measures better. Instead of a radial horn I’d look into a modern design, something along these lines--

AutoTech Iwata-600 - AutoTech Horns - Horns DIY Sound Group

AutoTech JMLC-400 - AutoTech Horns - Horns DIY Sound Group



[ GPA had re-magnetized the 802s and installed new # 34647 frams.]
 
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