Altec 12/15 'alternative'...

So I've been wanting to wire up the auto-formers to a switch to make adjustments easier. I've also been meaning to add in some PIO caps, and a few other details. I just wired up the big mast_mutter autoformers to a nice, NOS RFT switch, though clearly 4 decks isn't needed, I had them on hand, and finding those in single deck isn't nearly as easy as I had hoped.

I've also wanted to try some Atlas Sound 100w autoformers as I've heard/read from a few sources that they're pretty decent, especially if just used for MF/HF. So I mounted those on the crossover breadboard as well, made some leads, and plan to compare them sometime this weekend.





I'm also taking down the big horns behind these. For a few reasons.

1 - I love these two ways that much. Though not the main reason.
2 - I'm about to start building some multi-cell mid horns. This will be a long, slow project I suspect.

At some point I want to try a few different crossover slopes, I think I need to roll the woofer off a bit more steeply, possibly. I'm hearing some 'congestion' around the crossover point (~2k), especially at a bit higher volumes. This could of course be the compression driver/horn, but I want to rule things out and a steeper slope on woofer, or CD/horn, or both, should help me do that.

I'm also still on the hunt for another EA 175, I have a very nice single, but haven't had luck as yet finding another.

The Soviet military KBG PIO capacitors sure do sound nice. I think I'll buy some larger values.

Cheers,
Gable

I wired the switch backwards, so clockwise turns the compression driver volume down.... haha.

What would life be without little mistakes?

Looks mighty good.

Clip leads are the secret, magic ingredient to bring loudspeakers to life.
All the cool kids know that.

mhardy6647 said:

Clip leads are the secret, magic ingredient to bring loudspeakers to life.
All the cool kids know that.

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Especially custom clip leads, specially made with copper clips, and silver plated copper, teflon insulated, mil spec, super farking fancy mil-spec wire.

after re-wiring the crossover and thus removing a lot of clip leads, I realized I don't need to order more like I thought I needed to earlier in the week. They were just mostly deployed and not hanging on the wall in the lab.

gable said:

Especially custom clip leads, specially made with copper clips, and silver plated copper, teflon insulated, mil spec, super farking fancy mil-spec wire.

Click to expand...

I had zoomed in and pixel peeped your photo, couldn't help but notice those obviously not bog standard clip leads. Very nice indeed.

gable said:

Especially custom clip leads, specially made with copper clips, and silver plated copper, teflon insulated, mil spec, super farking fancy mil-spec wire.

after re-wiring the crossover and thus removing a lot of clip leads, I realized I don't need to order more like I thought I needed to earlier in the week. They were just mostly deployed and not hanging on the wall in the lab.

Click to expand...

Your making me feel quite barbaric.

gable said:

Especially custom clip leads, specially made with copper clips, and silver plated copper, teflon insulated, mil spec, super farking fancy mil-spec wire.

after re-wiring the crossover and thus removing a lot of clip leads, I realized I don't need to order more like I thought I needed to earlier in the week. They were just mostly deployed and not hanging on the wall in the lab.

Click to expand...

BTDT

So, I didn't get a chance to compare the auto-formers this weekend as I had intended. Our chihuahua has been having some heart issues, and was sick all weekend, he kept us up all night, and I was just wiped after that. Good news is, he's much better now, got the right meds in order and he is his usual asshole self, that I love so much.

So this evening after work I decided to swap in the Bozak B-199a's that I got from @rusomon and give them a listen. They're 8ohm as opposed to the 16ohm of the SP12B's. They're not quite as efficient, though not much so. I happened to have a much closer matched inductor value for their low pass, a nice copper foil jantzen (iirc).

After a little bit of tweaking the horn level I've got them pretty well balanced. Still using my 45 se to drive them, they can't play quite as loudly, but the difference isn't very large. The bass is much more articulate, and more importantly, the crossover range is much much more clear. This is just from an hour or so of listening, so more time is needed to confirm my initial impressions.

I must admit I like the look of the B199-A's more as well, fwiw.

For the record, these never looked this good at my house.

gable said:

Our chihuahua has been having some heart issues, and was sick all weekend, he kept us up all night, and I was just wiped after that. Good news is, he's much better now, got the right meds in order and he is his usual asshole self, that I love so much.

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Good to hear the dog-friend is better. I have an asshole named Otis the wife and I dolt on.

Good to hear the dog is better, pets pass through our lives too quickly.
Glad you got some listening time in. Looks good too.

gable said:

So, I didn't get a chance to compare the auto-formers this weekend as I had intended. Our chihuahua has been having some heart issues, and was sick all weekend, he kept us up all night, and I was just wiped after that. Good news is, he's much better now, got the right meds in order and he is his usual asshole self, that I love so much.

So this evening after work I decided to swap in the Bozak B-199a's that I got from @rusomon and give them a listen. They're 8ohm as opposed to the 16ohm of the SP12B's. They're not quite as efficient, though not much so. I happened to have a much closer matched inductor value for their low pass, a nice copper foil jantzen (iirc).

After a little bit of tweaking the horn level I've got them pretty well balanced. Still using my 45 se to drive them, they can't play quite as loudly, but the difference isn't very large. The bass is much more articulate, and more importantly, the crossover range is much much more clear. This is just from an hour or so of listening, so more time is needed to confirm my initial impressions.

I must admit I like the look of the B199-A's more as well, fwiw.

View attachment 15829View attachment 15830

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You should NEVER place two coils in a crossover side by side in close proximity, like in the picture. This changes the inductance of the coils (slightly) and worse, gives rise to crosstalk. There are many websites that will show you the proper placement of coils in a crossover. Check out ”fEARful crossovers by greenboy” for example.

Boli46 said:

You should NEVER place two coils in a crossover side by side in close proximity, like in the picture. This changes the inductance of the coils (slightly) and worse, gives rise to crosstalk. There are many websites that will show you the proper placement of coils in a crossover. Check out ”fEARful crossovers by greenboy” for example.

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Thank you for the reminder, I am quite aware of coil interaction. Troels Gravesen has a nice page about it as well.

Placement of coils in crossover networks

The two coils in my crossover are not in use together. Only one has signal through it. I'm also removing the unused coil, that picture was just from me placing the new coil into service when I changed the woofer. I believe the interaction is when two coils are both in the circuit.

gable said:

Thank you for the reminder, I am quite aware of coil interaction. Troels Gravesen has a nice page about it as well.

Placement of coils in crossover networks

The two coils in my crossover are not in use together. Only one has signal through it. I'm also removing the unused coil, that picture was just from me placing the new coil into service when I changed the woofer. I believe the interaction is when two coils are both in the circuit.

Click to expand...

Sorry, I didn't realize that only one coil is in use. No problem then. Yes, lots of interesting stuff on Troels Gravesen’s website.

No worries!

He has published quite a wealth of knowledge and experience.

So, I've been listening to the Bozak's in the two-way system for awhile now and I am loving them. They're more efficient than I thought, which has made matching them to the horn much easier.

This evening I switched the mast_mutter autoformer for an Atlas Sound AT100-rm, I've been wanting to compare performance in this position, ie: bandwidth limited to mid and hf. I _think_ they might roll off the upper hf slightly, but I'm not sure just yet. They sound pretty damn good so far, I've only listened to a few types of music thus far. More listening needed certainly. For the price, ~$15-30 on eBay, they are damn good. I would be hesitant to push much lf through them, but in this role they seem to work quite well. I think I'll stock up on a few more, as they are very handy for crossover testing/tuning.

One other wrinkle is the Atlas sound steps are 3dB compared to 1.5 or 2dB (can't remember exactly) of the mast_mutter units.

To be clear, I still think the mast_mutter autoformers are better, and in a more finished system, I would pretty much just use those, or Slagle's speaker level autoformers. When I get back to building the big horn system I'll test with the Atlas autoformers, but will buy some from Slagle ( Intact Audio ) once the crossover is closer to 'final'.

I'm glad my 45 amp is 'enough', but I do think I need more in this big room, and I'm planning on living with this system, in this room for awhile. Maybe a 2A3 amp should be next on the list.

Nice pics and description.
I might try the Atlas autoformers and see if they sound better than l pads.
Cries autoformers pretty reasonble too, but have not tried them.

Definitely better than L-pads imo.

So after some more time on the Atlas autoformers, I still prefer the mast_mutter ones, mainly for the more granular attentuation control.

tl, dr; The Atlas Sound at100* are a damn good deal, and a good tool to have in your kit, IMO.