Just to fore warn ya'll that this isn't a post about asking how much is my new stuff so that I can go flip it.. Might be a little long as well

here's the link to the pics, not sure if I am allowed to do that here or not.

The AA's High Efficiency forum

As you can see I came across some Altec MI stuff, I did not open up the 817's and see what driver they had, but I have seen through some searching that this might be the best choice for hi-fi reproduction. Is this true or is it a matter of preference?

I am going to be using these in a large (20'30') dedicated listening/HT area and would like to know if these could be used in that manner....

I mainly listen to music and have mainly tube amplification ,sets,and various other pp and an old pioneer SS receiver.

Also I need to check the diaphragms and make sure they are ok, how do I go about doing this? Will I need a torque wrench to tighten them down? I am diy-er and like to learn new things,,so I will be up too the challenge...

One of the 291-16k's is missing both positive and negative leads on it, is there a re fix for this? or am I'm screwed?

I plan on taking my time with this , since I haven't even cleared the ground for the new addition yet, so these will be set up in my garage , which is about 25'x25' in size,, I plan on only using 2 of the 817's cabs..

I look forward to any advice, experience and ideas you may like to share,, and If I am allowed I will post pics on my continued progress

Dave

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"When words fail, music speaks" - HC Anderson

Good find, you made out like a bandit.

Did you bring them horn in your little white car?

I rented a 6x12 box trailer, they did not have a flat one, and it WAS suppose to rain,, but you never can tell.....

Got to go back and look at the pictures, but those appear to be pretty long throw horns. Ideally, you might want shorter ones in a garage or large room in your house. They will work, but are designed to project much larger distances.

Either way, ............

I would use that one as the test subject. You can carefully take out the screws that hold on the back cover and slip it off. Do this in an area free of any metal debris and keep all ferrous tools clear.

Neither of my 291's had terminals when I bought them, but one of them was also missing a diaphragm when I opened it up. If you have the $$$$ available, then best thing to do is bite the bullet and send them back to GPA for a tune up, and new 'phragms if necessary, especially if conversion to a 288 series is possible. Even just 2 at a time would be worthwhile...IIRC, the 288's are better suited to audio while the 291's are more for sound reinforcement....

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Cheers!

Analog Addict

Jack of all Trades, Master of None
Searching for Sonic Nirvana...

My alter ego...

Time is an abstract concept created by carbon-based life-forms to monitor their ongoing decay. -Thunderclese

I was thinking the same thing about the driver with the missing terminals.....wondering who might have been picking around,,,,

The only story I got on them was that I bought them from the second owner , who was also gonna use them in a project. He had them just sitting around a corner in his hanger/garage/house, and said he did not have anything to push them with. He told me he and his brother got them from a theater somewhere in middle NC.

I believe from what literature I have seen these are from around '83, and the big horns are MR 42a's? and the small ones are MR something else...
If it is possible to convert 2 of the 291-16's to home audio use, I will get a separate pair of smaller horns,, any suggestions?

With the diaphragms in question, you are saying to get the replacement diaphragms for the 288's then? I would like to use these in a home audio/theater set-up, at least 2 of them. How challenging is the replacement process? I noticed that the 288's spec's are almost identical to the 291's, only the 288's seem to go a bit higher..

Also will be looking into a pair of tweets for them, the 288's go up too 15k right?

Will have to save some $$$ but I think I will get at least a pair going by this time next month or at least try. I will have to keep them out in the garage, I doubt I have a room big enough in the house to place the 817 cabs in.

Just still wondering if the 921-8a woofer is cut out for at least decent audio reproduction.... or will I need to start looking elsewhere?

Ahh, a lot of what ifs to and looking forward to getting answers or finding out myself.

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Nothing like a great big pair of speakers to make your day.

I would make it a 3 way TRI AMP the bottom part
from 20 to 250 second half 250 to 500 and horn
500 to 20kHz.

Can be used for rock group and you will get a lot of SPL Dynamic range out of it.

This sort of set up for small night club is the Ideal thing.

http://www.greatplainsaudio.com/PartsList.html

and the 23834 diaphragm for the 288-16G will fit on the 291-16K, so you're in business.

Consider the horns and four loaded 817 boxes as a substantial free bonus.

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Born with a fork
in a world of soup

I think I might have used maybe a 1/4 tank of gas,,,,so every thing came out under with trailer,gas,lunch and time included, $500,, not to bad I am guessing....

might have to get a hold of bill , I have seen that it is best to call him, and when that time comes I will...

Is there a walk through on replacing the diaphragms if needed?

291- high power attenuated highs...stock unit, no longer made but available on ebay. Aluminum dome/mylar edge. Technolgy of the 70's

288- AFAIK GPA is only making one 288 fram in different impedances. The 288 is moderate power, good highs. An extra octave extension over the 291.

299...derivative of the 288, different aluminum alloy, high temp carbon fiber former. High power good highs, If you wanna play loud in a big room, consider these. newer technology than 291.

I have heard a zillion times the 288 and 299 frams test exactly the same...to my ears, which have made me a lot of money, the 288 has SLIGHTLY better highs. I don't want to open an argument on this, just point out where fact and opinion diverge.

If you are handy, replacing the frams you self isn't hard. You don't have alnicos right? So they won't need remagged.

GPA has a download with instructions on replacing frams.

Frams wire and terminals maybe 30 minutes a driver.

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"There are four boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order."

I like to consider myself handy and capable, so it looks like I will convert them into 288's then.....right now these 291's are 16ohm,, does it matter if I get 8 or 16 ohm fram versions then? they not alnico, so no re-magging for me

I will look on the GOA site for instructions... Thanks bowtie for the link....

gonna go do some reading now

So NP if you want 8 ohm drivers...

Mainly be careful with the screwdriver when replacing frams- in the beginning I would recommend holding the tip of the screwdriver and guiding it onto the screw then transferring grip to handle- that's the chief hazard is the mag yanking the driver in a direction you didn't plan on...

Went to the lansing heritage site and downloaded all the tech specs that apply to all the drivers, cabs and the horns, also copied the info on the T/S spec and xfered them to my own excel spreadsheet for future reference ....

I read about being careful with screwdrivers.... i guess i could use a non- magnetic one I guess, or tweaker? I am going to be looking at them all here in a bit.

A quesiton on measuring DCR, they say 16 ohms, I really doubt if they will read that high after all this time? what is the margin -/+ they should be reading,,,, I have seen 8 ohm speakers read around 6-8 ohms and still be fine..

I have still hooked these up for fear of damaging them..... I need to make a xover in the short term,, any suggestions?

gotta go ..

http://monsite.wanadoo.fr/acoustiqueraffaitin/index.jhtml

I have used 416B loaded 817s under EV9040/288Hs and loved the combo. Please let us know what woofers came in the 817s.

For crossover duty, btw, you cannot beat the Behringer digital gear for value.

Lots of people confuse DC resistance and inpeadance- they ain't the same.

The resistance of the speaker really does not change much throughout its life- those 8 ohm speakers were 6 ohms when they were new.

Impedance is always higher than DCR. 16 ohm units often read 12 ohms.

Impedance takes in a number of factors.

For instance, I play with bass horns. It is not uncommon for an 8 ohm speaker to go up to 10-12 ohms impedance in the horn..this is due to the loading the horn places on the unit.

Impedance is quoted as a "nominal" figure and varies with frequency. It helps to have the "curve" showing these changes when designing a passive crossover.

For instance- a diver that is 8 ohms at 800 Hz may be 9.2 ohms at 1200- if you wanna cross at 1200 take into account the 9.2 figure if you want to be exact...

The beauty of active xovers is all these calculations go out the window...The Behringer DCX 2496 is the best bargain in cheap crossovers IMHO.

There are European guys modding the outs of the Behringers to make them friendlier to home use..I wouldn't bother.

If you just want crossovers short term, basic SR units will at least get them up to listen to..

A "textbook" unit just assumes 8 ohm impedance and goes from there...not fine tuned to the speaker or box.

Thanks for the insight, I should know better , but were never really measured speakers in the navy,, I just looked at o-scopes and analyzed equipment and tweak stuff away....,,

I would run all the bottoms down to their lower limit...and start rolling the mids out of the lower set an octave or so below where I crossed to the horn...

The reason for rolling the mids out of the bottom cabs is to create a smoother transition in sonic image at xover.