Originally Posted by MarkDA
Well as far as I know all the 804s and most 806s were 16 ohms. However as you have 8 ohm 806s (which are later models, black rather than green, right?) you'll probably need to compensate for that in the crossover, depending on the crossover you're using.
Yes, the 806s are black. The crossovers are the N-800-F version. So will it just require some adjustment with the attenuator, or will I need to modify the crossover? -Thanks.
PM a fella here named Zilch, he's investigated Altec crossovers and can help you much more than I can.
A) The Altec N-800-F crossover was used both for 8-Ohm and 16-Ohm driver combinations in different products. The sims and performance measurements are in this thread, which should be of interest to dual-414 applications. Sorry, it's 19 pages, 285 posts, but includes all what you need to know:
http://audioheritage.org/vbulletin/s...ad.php?t=18913
B) There's nobody home above 10 kHz with either 804 or 806, and their excessively forward midrange is only partially mitigated by later versions of N-800-F. There are several options to correct both issues, and you can read about them here:
http://audioheritage.org/vbulletin/s...ad.php?t=14690
Sorry, that one's 59 pages, 881 posts, but, again, it's all there.
Bottom line for 804/806 + N-800-F performance:
Actively biamped with CD compensation, you can get them to play reasonably flat out to ~14 kHz:
Note the different driver model in Tom's second pic. He can tell you more regarding what that's about....
Wow- thanks. And I thought this was going to be a relatively straightforward little project!!
Mark---I think your crossovers are meant to work with 16 ohm compression drivers rather than your 8 ohm ones. If so that will change the crossover point, the system won't work as intended.
This is one reason lots of DIY guys and experimenters use active crossovers. If you have an extra amp and $100 for an active crossover consider going that route.
Minor point:
Rotate your woofers 180 degrees. The Altec elastomer goo used on the surrounds can creep and make its way on to the cones. This thread reminded me to do mine yesterday. All is well
(Man, those Altec woofers are beautiful.)
FYI, my 9844s run 8 Ohm compression drivers, and 16 Ohm 414Zs (in parallel.)
It CAN be straightforward, and as easy as finding out what the stock components were and putting that together. Plenty of Altec enthusiasts are pleased with those results. It's when we look at that and decide to improve upon the original designs that it becomes complex.
We looked at that in my first citation above, which is Skywave's 9844-8Bs. The sims show what's up with running those 8-Ohm drivers (the two woofers are in parallel) on the supposedly 16-Ohm N-800-F crossovers, as Altec did in this instance and others. A shift in perspective as to what stuff "is" is necessary to appreciate that the change in crossover point and driver response shaping is, in fact, intentional....
Okay, so if I have four 414z 16 ohm woofers, two N-800-F crossovers, two 806-8A/811B 8 ohm horns, and Carmel cabinets in pretty nice condition... what's the best thing for me to do? Try and source the original 804 16 ohm horns, or maybe modify the crossover? Goal is just to restore the speakers and see what potential magic lurks in the design, however having never heard them or similar outfitted properly before I can't put a dollar value on how worthwhile this project really is. Thanks in advance for any suggestions and direction.
804 is the driver, not the horn, 806 is the same, and it doesn't matter if the diaphragms are 8 or 16 ohms.
Hook it up, and you're done; the "magic" will appear. If it's worth ~$200 to you to hear it with 16-Ohm diaphragms, have a pair of those installed in your drivers by GPA; he'll recharge the magnets at the same time.
Next step, biamp and push the "CD Comp" button; that'll get you the best these are gonna deliver.
[You CAN get better bass using the "0.5" trick with that, if desired....
Here are some pictures of my Altec Avalon's!Needing outside restoration, the insides look unmolested. Is there a place for user photos? How about a Yahoo group?
I guess I ought to plug these Avalon's in and fire them up. I've been busy working and trying to finish up various hifi projects. Since we downsized our home, these speakers don't exactly fit in the living room. My wife is very patient though...
I have more pictures, closeups of the drivers: 804A and 414Z. The 414 has these numbers on the backside of the cone: 21060.
Tom, I have it on good authority that the Altec 804A and 806A drivers are not identical. Although they look the same externally, the 804A has a considerably smaller alnico magnet than the 806A which was its successor. The 804A was introduced during a period when management was cheapening the Altec line into oblivion; the 605A replacing the 604D was another example of their insanity. Apparently the 804A's magnet was weak enough to move the mass corner downward and begin losing the top end, prompting the introduction of the 806A after many complaints to get the h.f. response back.
Steve I'm forced to wonder about your source and his credibility. Jim Dickinson states the 804 was made from 1961 to 1964 and then rebranded as the 806 in 1964. Dickinson seems to know his Altecs.
Comparing 804 specs and 807 specs (1968 807 specs, and all seem to agree the 807 is an 806 with symbiotic) show the 804 and 807 having the same magnet weight, magnet strength and overall unit weight. This tends to confirm that the 804 and 806 are the same driver.
Perhaps your pal is confusing the 804-806 thing with the 802-806 thing.
Tom, I checked with my friend Robert. He says that despite the published specs there are indeed several differences between the 804A and 806A examples he has had apart. He says the 804A magnet has a smaller outer diameter and the phasing plug has smaller slits, giving the driver a higher compression ratio than the 806A. He also said that the diaphragm in the 804A may have a shorter voice coil than the 806A, though he is not certain about this.
I remember taking apart a junky pair of 605A Duplex drivers years ago, and was surprised to find that the h.f. driver phasing plugs had smaller slits than the 806As and 802Ds I had at the time. Robert says that the 804A and 605A share this higher compression ratio phasing plug.
Robert is in the middle of moving, but if he can find these parts he will bring them to me to photograph. Stay tuned.
Robert brought me the magnets from Altec 802D, 806A and 804A drivers. As I hope can be seen in my crummy pictures, the 802D and 806A magnets have the same inner and outer diameters but are different heights as the 802D has a longer body. The 806A magnet has the same height and inner diameter as the 804A magnet, but the larger outer diameter that it shares in common with the 802D magnet. I don't know why these relationships aren't reflected in the Altec literature of the time, but suspect that the corporate cost cutting and subsequent eating crow may have played a part.
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