825 Build Questions

I recently picked up 3 empty 825 cabinets and have started working on them. I could not afford Altec woofers but I did find 2 AE TD15M woofers for a very reasonable price. I installed one with a 511B and 808A driver on top playing mono. I am using active crossovers with 18db slopes run through Ashly FET amps.

At low volumes they sound pretty good. As they get louder they get mushy which I attribute to all of the cabinet and horn ringing coupled with my concrete vault basement. I'm pretty sure that this can be made to go away and have read many posts about this. Also once they get moved out of the basement into the barn/theater and once deadened they will hopefully sound better.

My question concerns crossover points. After much experimenting by ear, but no measurements, I have settled on about 2000 as a good crossover point. The driver plays flat up to 4K but above 2.5K I start hearing changes in the sound as I move from side to side and around the room. Clearly at this point the off axis response from the 15" falls off and becomes audible. What surprises me is that the driver can play up to 2K without hearing off axis issues. Is this a side effect of the short horn on the woofer? Is it better to use the higher crossover or a lower crossover? Once dialed in I can listen to the same vocals over and over and even change the crossover mid note and not hear much, if any, difference from 800-2K. Below 800 the vocals seem a bit grainy, less smooth. The reason I ask is that I am looking at trying a compression driver (Radian 475) that wants to be crossed 1200+, preferably, 1600+ from what I read. Before trying that I wanted to see if there is any issue with using such a high crossover.

Thanks,
Greg

sheesh nobody had any advice to give greg here?
all i could say in my VERY limited altec experiance is: greg break down and get a pair of altec 3156 16s. they run for about 100 bucks each. i'm not even going to look up the specs on the lf drivers your using but theres a 99% that they're not designed for a loaded horn enclosers. the night and day difference will amaze you. as far as the 808 drivers they usually cross over at WAY less than 2000. try something like 800.
now if some real altec guys would chime in greg would probly appreciate it. :)

Hmm, I wrote a response days ago and thought I posted it, but apparently I did it either during one of the times the board disappeared or 'customer no service' AT&T dropped my DSL due to the high traffic demand during the 'final four' basketball series being held here. Now all I have to do is remember where I saved it. :(

GM

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Originally Posted by Phil-G

all i could say in my VERY limited altec experiance is: greg break down and get a pair of altec 3156 16s.

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When did the 3156 become suitable for the 825/828 cab? With its high inductance and relatively low Vas it's a prosound vented cab or scoop bin woofer.

GM

No expert here either....but I would stay between 800-1000 crossover frequency. I've used Altec 421's with this type cab with approximately 54 sq in ports with good results. Diffinitely pad down the 808's with an L-pad and series resistor. And use a bypass cap of 1-2 uf to eq the horns. I would also listen to each of the drivers independently of one another. This may help to reveal any anomalies within the system and the drivers themselves.

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Originally Posted by GM

When did the 3156 become suitable for the 825/828 cab? With its high inductance and relatively low Vas it's a prosound vented cab or scoop bin woofer.

GM

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well notice i did lead that off with "VERY limted experience" someone else suggested that to me as an alternative, seeing as how i'm on a budget. :)

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Originally Posted by Phil-G

well notice i did lead that off with "VERY limted experience" someone else suggested that to me as an alternative, seeing as how i'm on a budget. :)

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A readily available, brand loyal, value retaining, "compromise" that gets sound coming out of your boxes. Probably wasn't suggested as the "ideal" driver. :D

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i'm not even going to look up the specs on the lf drivers your using but theres a 99% that they're not designed for a loaded horn enclosers.

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FWIW, the Acoustic Elegance TD-15M is a highly regarded woofer in the DIY and HE(high efficiency) interest groups. As with many niche market products, they're only produced to order which can cause some frustratingly long delays(you can read about this on other forums).

http://www.aespeakers.com/

Personally, i'd love to have a pair of non-used ones complete with proper phase plugs. However, the snail's pace at which buyers of new product are serviced is likely to ensure that i'll never own any.

Just another kudo's to Bill and GPA for maintaining the Altec level of quality with very reasonable turnaround times.

Since you're using active crossovers, you have to be careful to get the horn and woofer into phase alignment, which usually requires woofer delay. The job is done for you if you use an Altec passive crossover and mount the drivers with the factory specified offset; otherwise you're on your own. As an example, I need 0.97msec of woofer delay for the midbasses I use with 511 horns, with a voice coil offset of about 17 inches. I determined that delay by inverting the horn polarity and tuning for a good null at the 800Hz crossover.

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Originally Posted by bowtie427ss

FWIW, the Acoustic Elegance TD-15M is a highly regarded woofer in the DIY and HE(high efficiency) interest groups. As with many niche market products, they're only produced to order which can cause some frustratingly long delays(you can read about this on other forums).

AE Speakers --- Superb Quality, Unforgettable Performance, Definitely.

Personally, i'd love to have a pair of non-used ones complete with proper phase plugs. However, the snail's pace at which buyers of new product are serviced is likely to ensure that i'll never own any.

Just another kudo's to Bill and GPA for maintaining the Altec level of quality with very reasonable turnaround times.

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yeah i probly should have at least looked them up before opened my mouth. :rolleyes: so how does phase plug apply to a LF driver? thats definately a new one for me.

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Originally Posted by bowtie427ss

FWIW, the Acoustic Elegance TD-15M is a highly regarded woofer in the DIY and HE(high efficiency) interest groups. As with many niche market products, they're only produced to order which can cause some frustratingly long delays(you can read about this on other forums).

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+1
I've not yet heard these, but some expert builders whose opinions I trust have spoken very highly of these woofers. I was just looking at these a couple of weeks ago for a project I'm doing for a friend to replace some old woofers in Altec 816 cabinets. You can find a measurement a DIYer made in this thread:

Ugly LP Filter

And some pro measurements of the "beefier" TDM15H can be found here:

Best woofer for a 2-way using Altec Mantaray

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Originally Posted by Phil-G

well notice i did lead that off with "VERY limted experience" someone else suggested that to me as an alternative, seeing as how i'm on a budget. :)

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Yes, I noticed, but my 'involvement'/interest WRT Altec products had for a variety of reasons dropped to near zero by mid ?75, so even though I couldn't find anything to support it in a quick search, I still wondered if more current versions of this driver had been 'upgraded' to horn driver status.

Just because someone has "VERY limted experience" doesn't mean that they haven't learned some useful tidbit that other, more knowledgeable overall, folks didn?t know.

GM

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Originally Posted by GM

Yes, I noticed, but my 'involvement'/interest WRT Altec products had for a variety of reasons dropped to near zero by mid ?75, so even though I couldn't find anything to support it in a quick search, I still wondered if more current versions of this driver had been 'upgraded' to horn driver status.

Just because someone has "VERY limted experience" doesn't mean that they haven't learned some useful tidbit that other, more knowledgeable overall, folks didn?t know.

GM

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I think it was probably me that made the suggestion to Phil based on the factors mentioned in my post above, with no implication that they were by any means ideal for the 825/828. At ~100 bucks a pop it's a cheap way to temporarily fill 15 inch holes with "our" brand, and they usually flip for the same price you paid which essentially makes them free sans shipping, and who doesn't like free in this economic climate?:D

i like free :)
i certainly didn't mean to cause a fuss GM. over the last few months i've become somewhat biased for altec products. i'm sure there maybe audio products out there that can reproduce sound as good as the older altec stuff but i'd have to hear it to believe it. maybe i should stick to asking questians. :Nodding:

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Originally Posted by Phil-G

i like free :)
i certainly didn't mean to cause a fuss GM. over the last few months i've become somewhat biased for altec products. i'm sure there maybe audio products out there that can reproduce sound as good as the older altec stuff but i'd have to hear it to believe it. maybe i should stick to asking questians. :Nodding:

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I don't think he or anyone else thinks you're causing a fuss. He questioned, and rightfully so, the suggestion of putting a 3156 in an 825/828. Certainly not an "ideal" combination, but so far as i know the speaker police won't arrest you for it, and if your ears are working it's pretty doubtful you'd break anything, and they'd make music until you can fund proper 416's or similar. ;)

Altec didn't always play by the rules either. The 411 is a great woofer, but you wouldn't normally expect to see one like this: ALTEC LANSING Model 9861

Ok, good to know, thanks!

Digital EQ can reshape the reflex BW, though if later OEM, GPA units sound as ‘muddy’ up high as the few I tinkered with way back when, then using XOs >500 Hz may prove very disappointing to some.

GM

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No fuss, it?s these types of scenarios that the most useful info sometimes surfaces.

Probably the most eye opening one for me was when I posted something about plywood 828 cabs based on my ~1975 knowledge and it tweaked enough folks that even lurkers challenged it.

Anyway, the upshot was that enough visible evidence was posted to show just how desperate Altec became later on to provide product. A7s made from a mix of cheap ply, MDF, particleboard [some cheaply covered with paper ?veneer?_ as seen from the inside], un-braced horn flares made from Masonite or similar that was obviously ?formed? in a series of bends on a metal forming brake plus other ?shortchanging? measures to use up as much scrap as practical.

Really sad and a pity those pics were lost unless someone made copies.

If you get a chance, audition TAD, GOTO, with the former maybe a ?tad? ;) better and the latter at least a notch up from all but the earliest 515s and some say on a par with the best W.E., Klanghorn, RCA point source [cone mid] bass woofers.

GM

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Originally Posted by bowtie427ss

The 411 is a great woofer...........

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'Woofer' is right, I had a tough time listening to the Barcelonas at 500 Hz and forget the Santanas at 800 Hz. What a waste of beautiful cabinetry! Can't even imagine what they sound like XO'd up high in a small A7.

Made great 'subs' XO'd at 120 Hz in the partitioned A7-500s though.

GM

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Originally Posted by gil393

As they get louder they get mushy which I attribute to all of the cabinet and horn ringing coupled with my concrete vault basement.

My question concerns crossover points. After much experimenting by ear, but no measurements, I have settled on about 2000 as a good crossover point. The driver plays flat up to 4K but above 2.5K I start hearing changes in the sound as I move from side to side and around the room. Clearly at this point the off axis response from the 15" falls off and becomes audible. What surprises me is that the driver can play up to 2K without hearing off axis issues. Is this a side effect of the short horn on the woofer? Is it better to use the higher crossover or a lower crossover?

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Hmm, ?mushy? typically indicates an under-damped alignment down low, which isn?t uncommon with old VOTT cabs due to air leaks basically defeating much of its port tuning.

At 2 kHz, a 511 is just a wave-guide, so other than mouth reflections back to the throat causing peaks/dips in the response, there?s no ?ringing? going on.

The mid-bass horn begins ?pinching? the driver?s output above ~1695 Hz, so it seems reasonable that a ? octave above it would be obviously audible off axis.

Short answer: the small single driver VOTT mid-bass horn?s close enough ?ideal? horizontal blend to 511/811 through the XO BW = ~1200 Hz/800 Hz respectively based on Altec?s DI Vs Q measured plots and use some form of CD horn EQ to flatten it out to ?taste? [minimize horn ?honk?/mids ?grain?].

GM

Thanks for all of the help. Sorry for not responding as I was out of town for a bit. These drivers were NOS from Lambda not AE. Long story short the original manufacturer and not the current. Also about half the price of the current drivers. Some say the cone mold is based on an Altec design, I don't know and it doesn't really matter. Basically, they were the best new 15" driver I could afford. The correct Altec LF drivers were too expensive and too risky given their age and the fact that I couldn't even get the horns shipped correctly.

I have quite a few air leaks to tackle, some bracing, and some port tuning. I will lower the crossover and try and figure out how to do some measurements. It may well be that the high crossover simply eliminates the 1-2K bump in response coming from the HF and thus sounds better. I can eq it flat digital or analog once I can measure. I'll also check phase but I don't have any time alignment capabilities other than phase and moving the horn back and forth.

Thanks,
Greg

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Originally Posted by gil393

Thanks for all of the help. Sorry for not responding as I was out of town for a bit. These drivers were NOS from Lambda not AE. Long story short the original manufacturer and not the current. Also about half the price of the current drivers. Some say the cone mold is based on an Altec design, I don't know and it doesn't really matter. Basically, they were the best new 15" driver I could afford. The correct Altec LF drivers were too expensive and too risky given their age and the fact that I couldn't even get the horns shipped correctly.

I have quite a few air leaks to tackle, some bracing, and some port tuning. I will lower the crossover and try and figure out how to do some measurements. It may well be that the high crossover simply eliminates the 1-2K bump in response coming from the HF and thus sounds better. I can eq it flat digital or analog once I can measure. I'll also check phase but I don't have any time alignment capabilities other than phase and moving the horn back and forth.

Thanks,
Greg

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My cones will be 60 years old next May and your eardrums will distort before these speakers will. Deafening would be an understatement.