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Time Alignment: Altec Model 846B & Model 19

Zonker92

Zonker92

All shiny and chrome
If you look at my signature, you can see that my 846B Valencias have almost the same components as Model 19s. The cabinets are kind of cool, in a way, since the baffles unscrew. So I'm thinking of making new screw-in baffles that are flush with the leading edges of the sides, and front-mounting the woofers in those baffles. That would look cool, reduce baffle diffraction and increase slightly the cabinet volume. All of which would doubtless yield zero audible improvement but hey, I like tinkering.

If I did that, for proper time alignment, I think I'd want to use a spacer to bring the horn forward, too. So ... would I want to keep the horn flange at the same relative depth as it has now, with respect to the face of the woofer? And for that matter, is the rear-mounted 846B woofer set to the same relative depth as the front-mounted woofer of the Model 19, vis-a-vis the horn? (I note that the Model 19 horn baffle is recessed but its woofer baffle is flush.)

I guess a simpler question is, does the Model 19 have correct time alignment such that, if I ever do this, I should simply copy the relative depths of the Model 19?
 
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Yeah, that's my gut feeling, too, subject to correction; thanks. Now I just need to scrounge for those Model 19 cabinet dimensions I've seen around here.

Ah, here they are. Damn; it's hard to see what the horn baffle depth is.
 
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The voice coils need to be "in-plane" to be in phase, that said, the horn has to be pretty forward to align coils, I think the 846 and 19 were what they called "stepped" alignment, to compensate, they ran the horn drivers in reverse polarity. I use my BBE DS26 to time align my Altec 604's with a 24db curve, a half millisecond delay on the woofer seems to work good to my ear. Dave.

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Fascinating; thanks! So .... do you think a few inches would make much difference, if I brought the woofer forward a bit? Seems like the binary, 180-degree phase difference might have some slop in the exact timing.

Also, I'm assuming Zilch designed the Z19 (which I'm using) to include this phasing approach?
 
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dgwojo said:
The voice coils need to be "in-plane" to be in phase, that said, the horn has to be pretty forward to align coils, I think the 846 and 19 were what they called "stepped" alignment, to compensate, they ran the horn drivers in reverse polarity. I use my BBE DS26 to time align my Altec 604's with a 24db curve, a half millisecond delay on the woofer seems to work good to my ear. Dave.

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With my M19's and the Z19 xo's I built for them does this apply?
I have wired + to + and - to -.
Sounds fantastic but maybe there's more!:D
So the red is terminal one on a 416? And terminal 2 on the 811 horn?
 
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Zonker92 said:
Fascinating; thanks! So .... do you think a few inches would make much difference, if I brought the woofer forward a bit? Seems like the 180-degree phase difference might accommodate some "slop" in the exact timing. Also, I'm assuming Zilch designed the Z19 (which I'm using) to include this phasing approach?
Click to expand...

I hear a half inch is enough to make or break the sound quality, Soundpractices did a study on that years ago, a few inches might aggrevate the situation. Not sure what Zilch did on the Z19 design since he probably didn't have any model 19's to check with his design, Dave.

PS - The link is dead but maybe someone else captured the story that was contained here about phasing and horn placement? soundpractices.com/images/phase.pdf
 
Thanks! If I even do this project, I'll probably try to keep the same relative depth as the Model 19s, which seem to set the horn baffle about two inches deeper than the woofer baffle.

Ricoh, I have my Z19s mounted externally, as you know, so I can readily switch the polarity where the four leads connect to the speaker terminals on the cabinets. I might try switching one driver's polarity back and forth, but it may be hard to tell when I have to keep shutting things off to make the switch ...
 
Zonker92 said:
Thanks! If I even do this project, I'll probably try to keep the same relative depth as the Model 19s, which seem to set the horn baffle about two inches deeper than the woofer baffle.

Ricoh, I have my Z19s mounted externally, as you know, so I can readily switch the polarity where the four leads connect to the speaker terminals on the cabinets. I might try switching one driver's polarity back and forth, but it may be hard to tell when I have to keep shutting things off to make the switch ...
Click to expand...

Careful, do both horn switches at once, otherwise the left and right channels will cancel each other out, you'll notice in the midrange!!
 
ricohman said:
With my M19's and the Z19 xo's I built for them does this apply?
I have wired + to + and - to -.
Sounds fantastic but maybe there's more!:D
So the red is terminal one on a 416? And terminal 2 on the 811 horn?
Click to expand...

The 2 on a horn driver is positive, on a woofer it's negative, Altec always claims a positive signal on terminal 1 will drive the voice coil away from the magnet, well, on a horn driver the magnet is on the front and the woofer on the back, confused yet?? :sigh: Remember, we're only talking about polarity on the horn, leave the woofer out of this!! :D
 
My Altec 416-8B woofers and GPA 902-8A horn drivers both have red and black terminal buttons. Those are both plus and minus, right?
 
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Zonker92 said:
My Altec 416-8B woofers and GPA 902-8A horn drivers both have red and black terminal buttons. Those plus and minus, right?
Click to expand...

Yes!!

From the horn diaphragm replacement instructions;
C. Install new lead wires on your
Altec 800-series driver by
connecting the red wire to the L2
external binding post, and the black
wire to the L1 external binding
post. Tighten securely by using the
method given above in Section B.
 
Thanks! I guess what I'm really asking is, assuming Zilch's Z19 design has already inverted the phase for the HF, I don't need to swap the HF leads ... again ... or anything? But at this point I guess we're speculating whether he did in fact invert them, so maybe I should just try switching them and see if I can hear a difference or improvement.
 
dgwojo said:
The 2 on a horn driver is positive, on a woofer it's negative, Altec always claims a positive signal on terminal 1 will drive the voice coil away from the magnet, well, on a horn driver the magnet is on the front and the woofer on the back, confused yet?? :sigh: Remember, we're only talking about polarity on the horn, leave the woofer out of this!! :D
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My M19's are diagram B so I should be ok. I have them wired like that.
Which is + to + and - to -.
But what I don't get is the polarity thing with the voice coil in back of the magnet.
Wouldn't inverting that as in diagram C harm the voice coil? And why is this done for what I measured to be 2 inches? Even in diagram B the front of my horns are not exactly even with the front of the woofer gaskets, which are at least 1/4 thick.
 
Right now, my 846Bs are between figures 2 and 3: The front edge of the horn is about an inch ahead of the front of the woofer and the horn flange is roughly two inches behind it. And my Z19s are wired as in 2.

I guess I'll experiment and find out if swapping the HF leads improves the sound, but it sounds as though ideally, to be like the Model 19, I should try for the alignment and wiring shown in figure 2.

Very helpful; thanks!
 
Zonker92 said:
Right now, my 846Bs are between figures 2 and 3: The front edge of the horn is about an inch ahead of the front of the woofer and the horn flange is roughly two inches behind it. And my Z19s are wired as in 2.

I guess I'll experiment and find out if swapping the HF leads improves the sound, but it sounds as though ideally, to be like the Model 19, I should try for the alignment and wiring shown in figure 2.

Very helpful; thanks!
Click to expand...

Sounds just like the Model 19. The front edge of the horn does stick out a bit farther than the woofer gasket. The horn is mounted 2 inches behind the front baffle.
My 19's sound great. And because of this I'm not going to screw with them.:D
 
When aliging voice coils I don't pay any attention to where the horn flares and flenges end up, the voice coils are the key. Regarding magnet front and backs, the horn driver has a throat so you want the magnet to pull the diaphragm towards it for forward excursion towards the listener so they reverse polarity, remember, a positve signal applied to L1 causes the diaphragm to move away from the magnet. The woofer voice coil sits on top of the magenet, so, + on L1 causes it to move forward towards the listener, confused yet?? :scratch2:
 
I guess I sort of get it, DG. :) Ricoh, I'd do the same thing if I were you. I'm in a slightly different situation. I guess not in terms of time alignment, but because my woofers are currently mounted on the backs of the baffles and I'd like to move them to the fronts. That would reduce diffraction and make them look better. It would also bring them closer to Figure 2, so I guess I should leave the wiring alone.

If I do this project, in keeping with my goal of leaving the original parts intact, I would make new baffles and simply screw them into place where the current ones attach. If I set the woofer flanges flush into the baffles, they would be aligned exactly as in figure 2. (I would use new ports (I may have to start a thread on that issue) and I'd have to make new grilles, too, or put spacers in behind the current ones, since they have woofer openings that are too small.)

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One thing that helped my B's is building a sturdy 8" riser for them to sit on. This puts the horns at ear level when seated. I use a electronic crossover which allows me to play with time delay if I want to. I also switched from 806 drivers to 902's. That helped a lot on the top end.
 
I'd love to see pictures of your risers, Mike. How did you finish them? I want to raise mine up too; my wife slid a big sofa in front of them. But I'm thinking of putting legs on mine, sort of in the style of my stereo cabinet (see picture below, from back when I had my 802-S80s), but taller.

As you probably noticed from my signature, I have the 902s, also. And the Darsts made me lovely foam horn surrounds (prototypes) and I built the Z19 crossovers. I also swapped out my 416 woofers from their Z models to Bs, just because I think they look a lot better (not that the relevant parts are even visible), and I found a NOS pair of Bs and sold my Zs.

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