Model 15 Cross Over Schematic

[vo1dza]

Does anyone have a schematic for a Model 15 crossover? I replaced the capacitors in mine last night, now one speaker sounds amazing, and the other is much improved. I need help sorting out the much improved speaker, as it isn't perfect yet.

Thanks

[gamalot]

I don't have the schematic but I do have 15s and a spare set of XOs. I am not electronically technical.

Have you checked and/or cleaned the adjustment L pads?

You might also try switching the offending parts to see if they sound better on the XO that seems to be working.

I assume you are not getting the clean sound from one of your HF drivers. Many things could cause this such as a tangerine phase plug comming unglued, an almost burnt out diaphragm that has a bad lead or crispy coil windings. Other possibilities could be discharged alnico magnets, bad resistors in the XO or even a bad XO coil.

I think I have seen it all at one time or another and even spiders or bees that built a nest inside the driver port.

Since you have one complete speaker that is apparently working correct, switch the parts that don't sound right into that speaker and see if they sound right in it. At least you will be able to find out what is not up to par.

Gary

[vo1dza]

Hi Gary,

Thank you for your comments. The problem with my speaker was a bad, brand new, t-pad. I ended up putting one of the old ones back in and things worked much better. I was amazed at the improvement in the HF by just replacing the capacitors. Night and day.

The other issue I have with the speakers is that they can be somewhat boomy, with odd resonances. I think it is partly the room, partly the fact that the woofers were replaced about 12 years ago by non Altec woofers (an insurance settlement). I've got a Behringer 8024 equalizer coming in the mail, so I'm hoping to be able to sort out some of the room acoustics. I don't think it will do much for the non Altec woofers, but it might help a bit. I've also sent a query to Steve at Great Plains to see what he thinks, but I haven't heard back from that query yet. Perhaps new Altec woofers are available? I don't know.
Graham

[gamalot]

I doubt the non altec woofers have the correct specs for the 15 cabinets. Model 15s should not be boomy at all.

I have seen many model 15s being parted out on Ebay and elsewhere simply because the horns and 802-8G drivers are worth considerably more then the complete speakers so it would seem.

You should be able to locate a pair of the correct woofers. I think that GPA can recone the 15 woofer and I know the foam can be replaced fairly simple, even DIY if you have the patience for such work.

I don't experience any cabinet resonance issues with my 15s so you might investigate to see what changes may have been done to install non altec woofers. There is no way of knowing what another might have done inside without seeing it for yourself. Check for anything that might be loose when you find the right woofs.

Gary

[vo1dza]

Hi Gary,

I know exactly what is in those cabinets, because I just had them all apart for refinishing. They look great! The only thing that was changed out by the insurance company was the woofers because they got beat up in a move across the country.

I had the old woofers around for a long time, and then finally got rid of them just before my last move. Now I find out they could've been fixed. My pack rat nature let me down on that one.

Graham

[Richard C.]

Graham,

Which aftermarket woofers did they give you? I have model 14's and my LF drivers measure about 13 1/4" dia. I was told the model 15's are different (larger voice coil) than mine, but that the diameter is the same.

I have seen some reducing rings made to adapt a 12" in, but they didn't look very nice.

Richard C.

[gamalot]

Much more important then the physical fit is the performance specifications of the woofer and if it matches the cabinet and the crossover design.

Model 14 and 15 woofers are identicle in size and appearance yet they do have different specs.

The voice coils are a different size but I am not sure which woofer has the larger VC.

Others here might be able to guide you to the exact correct woofer as I am sure a few other Altec speakers used the model 15 woofer, possibly the model nine and the Santana.

It is certainly possible to find a suitable aftermarket woofer that will work but my appreciation of vintage will always go toward making a nice speaker correct as it was intended to be. A model 15 simply can't be a model 15 unless it has the correct motor and drivetrain.

Insurance companies don't know squat about audio gear but we do and with the availability made possible by on line auctions it is highly possible to make the speakers whole again.

The model 15 is a very fine speaker and very much worth making it right. To put it another way, a model 15 with the wrong drivers is nothing more then just a speaker and probably not worth half of it's real value no matter how well it works or might sound.

Gary

[vo1dza]

Hi All,

The replacement woofers in my Model 15's are labeled "Addison Super 12". I don't have any information on them. They look nice, but I'm sure they don't have the same characteristics as the proper speaker. Can anyone shed light on what they are? Does anyone have a spec sheet on the actual proper woofer?

The rest of the system is in fairly nice shape. I love the colour and texture of Walnut, and I've maintained the 'furniture' over the years. The cat 'took care' of the original foam grill, so that is a project for the future.

I'm not a purist in the sense that everything has to be original. I do want to make them sound right at reasonable cost, and if that involves aftermarket woofers, so be it.

If the solution involves modification to the crossover, I can go there as well. (Don't burn me as a heretic please!!) I'm open to all suggestions.
Graham

[gamalot]

No flames from me Graham, they are your speakers and the only one they have to please is you.

My comments go more to you saying your Model 15s are boomy when the fact remains they really are not 15s as we know and love them.

I also am very aware that shipping to you could be a might heafty price so you may have to make due with what you can find locally.

My technical knowledge is seriously lacking but I will bet you could go to Parts Express and search the info there to find woofer specs that will work in the 15 cabinets. Then you have to figure the XO design and find the best possible alternative to match as closely as possible.

If I were you I would also keep an eye on Ebay as I have seen numerous 15 woofers go rather inexpensively but they usually will require at least new foam surrounds.

If your HF drivers are correct then they are 802-8Gs and probably have 033952 stamped on the rear caps. The diaphragms should be the 23744 light frams that many love.

Grills can be an issue if you use them and want them to look good. New foam can be had from a member here at a price or you can do like I did and substitute standard grill cloth with some work and effort.

I think you could search the GPA site and figure out the woofer number and also what other Altec speakers shared that woofer which will give you some idea of what speakers being parted out on ebay will make your original.

I am sure we have members here who know what other altecs used the 15 woofers but this thread may not have peeked their interest so they are not jumping in. I am almost certain either the Santana or the Stonehenge used it but they each had variations in models like the Stonehenge II.
I also think the model 9 may have used it but again I can't be sure.

As for waiting on a reply from GPA, I have always had excellent telephone response but often not very good email response. Bill at GPA will certainly know which altecs used the 15 woofers and he may very well have a new model in production that will replace it.

Don't give up or get discouraged about the lack of response here. Many members are busy at the moment gathering nuts for the approaching winter and/or getting children settled in the new school year. Once things settle down we usually become more active here.

I will let you know what I can learn so watch for a PM from me in the near future.

Gary

[Richard C.]

I looked up the "Addison Super 12" and it is not a good match for a model 15 at all.

The FS is probably close at 27 Hz.

89dB SPL/1W is about 6 or 7dB less than it should be.

The freq response of "20 to 1500" Hz may be 10dB down at 1500 Hz, which means it won't meet the Xover point with enough output. The xover point is probably 1500 to 2000Hz, so it requires a very special woofer.

Richard C.