ALtec Model 19-XO upgrade discussion

[ngccglp]

Hi Gary,

Vertical alignment is absolutely important, but you don't need to invest in those equipment to get it right.

If you are using the M19 XO, then what you need is probably for someone to give you the exact offset dimensions of the 811 and 416 in the M19. You'll probably be 95% there. And if you must, fine tune further with CDs you are very familiar with.

I have successfully adopted the M19 XO to my 288/1005. I don't need no 2405 anymore. I used Hovland for the bypass caps. The depth and details is just amazing once you level the response. The optimal setting for the mid is about 7 for the 288/1005 vs 4 for the 802/511. I must say the M19 XO is a very important piece of network for all who doesn't wish to dabble in active setup.

[Zilch]

Transcend technophobia for free here:

http://www.trueaudio.com/rta_abt1.htm

http://www.trueaudio.com/

[ngccglp]

Here's a pic of my DIY M19 equalization network. The transformer is to match the impedance of the 288-16G to the N501-8A (not in picture) and the equalization network.

[DaveV]

Being an old "tube jockey" I can keep my old tube equipment going by troubleshooting and parts replacements, change caps in xovers and try this and that different part in an existing circuit to see what sonic differences there may be but I don't have the knowledge needed to analyze circuits.
The question I have concerns the way that the Model 19 xover is layed out and I can't figure out if it was done this way as a cost/assembly time savings issue or if this particular configuration is needed to achieve the desired results of an EQ xover like this one.
My specific question relates to the way the 802 is connected to the plus (+) woofer or now common plus connection for both 416 & 802 but after the .3MH inductor.
Altec said there was interaction between the MF & HF controls and I'm wondering if some electrical/sonic improvement could be had by changing the layout.
What would happen if the all the 802 xover parts or elements were all put in parallel with the plus and minus input points of the xover and were no longer part of the woofer plus line?
The 2.77 would then in theory need to be a 3MH?
L1 and R1 would remain but their connections would be in parallel with the xover inputs and the plus input of L2 would go direct to the xover plus input.
The way I see it is that the only changes would be that the .3MH is no longer in series with the 2.77MH and that the two drivers could now have dedicated plus and minus lines from the amp inputs on the xover.
Could this not lead to better driver control and sonic clarity with no interaction plus open up the possibility for bi-wire should someone wanted to try that?
Sounds too simple to me so I suspect there's a reason why it was done the way it was but does anyone have the technical reason why it's done this way?
If I haven't made myself clear by my description, then look at the schematic for the N1201-8A xover, break the connection to L2 after the point where the R1 pot wiper line is connected, then draw a new connection line from the input side of L2, where you just broke the connection, over to the black dot on the left indicating red terminal.

http://home.earthlink.net/~jmarkwart...s/n1201-8a.pdf

[Zilch]

It's a good question: how to split M19 crossover for biamping and retain the HF compensation. I'll explore that a bit with sims, perhaps this evening.

I am presently clueless as to why the designer might have done that.... :dont-know

[DaveV]

Zilch,

Maybe you misunderstood me because you say bi-amp in your reply.

My question referred to a possible bi-wire capability with the change in component topology, not bi-amping.

Bi-wire as in running two conductors from each amp output terminal. One pair being for the woofer xover circuit and one pair being for the HF driver xover circuit so that the physical parallel connection between both ranges is at the output of the amp and not on the xover board.

I know there's controvesy over the validity of doing this because it borders on "high end voodoo" but I'm not looking for comments on bi-wire. My point was that the possibility would be there if someone wanted to try a bi-wire configuration to make up their own mind about it.

The reason I was asking about a topology change was to ask if there might be a sonic/electrical improvement to be had by getting the .3mh out of it's current position in series with the 2.77MH and then having both woofer and HF driver on their own two lines back to the amp input on the xover board. Maybe like better driver control. But would taking the .3MH out of it's current position in series with the 2.77MH upset the whole HF EQ network for some reason?

Yes, you could bi-amp too and keep the HF EQ network but then that doesn't answer my specific question question because the 2.77MH and the 21uf cap (C3) would be gone with areal bi-amp setup would they not?

Could be that either way the answer would be the same but I wanted to make sure you understood what I meant.


Dave

[Zilch]

Yup, gonna look at just splitting them apart first.

Figuring out how to biamp with an external crossover will be tougher.

We may have to call in the big guns for that....

[DaveV]

Update to my December 13th post where I had "upgraded" the 2.7MH inductors, had too much bass and muddyness to voice then finally realized I just wasn't used to having speakers that didn't need bass or treble boost and had forgotten my preamp was at +4db boost for both as it had been for 15 years with 2 other pairs of speakers I previously owned to make them sound good to me.

Well I put the "better" 2.7 MH inductors back into the circuits and there seemed to be a lack of bass with the flat preamp settings.
I called it quits and didn't listen to anything for a day.

When I listened tonight I heard a whole different speaker. With the original 2.7 MH inductors and just new caps there was a hole or thin sound between the woofer and mids that made the mids a bit harsh at times, the human voice a bit to thin, the mids a bit too real or "alive" but the bass was really there.

What I heard tonight was the filling in of the "hole" so the mids don't sound harsh any more, human voice is more full but not chesty and the "alive" mids are there depending on the program material but now I hear for instance, a more natural sounding voice with realistic very clear and sharp sounding instruments behind the voice. A contrast showing that the two do exist on the recording.

The bass is there when it's supposed to be and it's way tighter and more in balance with the mids and highs.
I have never heard my Mac 225 tube amp make lows like this with any speaker. You would swear there's a 100/channel SS amp on the woofers in bi-amp. The woofer control is amazing and really almost too much. No more rolling floppy bass.

Because I finally got my added tweeters crossed over better to just overlap the 802 highs and not add or compete and with the xover HF controls at 12 o'clock, the overall balance is there and these are the flattest sounding speakers I've ever had yet they have that open horn sound.
The added tweeters blend so well they sound like they belong or are part of what's coming from the 802/811's.
I'd have to say that this flat smooth sound won't appeal to everyone but after listening to orchestra, voice, jazz and semi techno or electronic music, I have to say that the speakers simply sound more like live music would sound.

I thought all this might be helpful to people interested in "upgrading" the model 19 xover because I am now convinced that you can make these speakers sound pretty much any way you want them to assuming of course that the mid or HF horn is what you like in the first place.

I haven't changed the design other than add tweeters direct to the amps with a simple 6db/octave xover, changed the xover caps and just the 2.7MH inductors so these are still Model 19's but with removable tweeters.

I still think that voicing with caps is critical if your after a just so sound and obviously the large inductor change was a shocker to me. Some may prefer the less controlled bass with the original inductors? It does sound more impressive but not as well defined and controlled.

Even with all the confusion and frustration I'm glad I did this piece meal rather than just jump into all new xovers and accept the sound I got as "upgraded" and that's it.

Any further improvement will be frosting on the cake.
Hope this helps someone in their adventures with the 19's.

Dave

[Zilch]

What 2.77 mH inductors?

[Bama5000lps]

This is my first post so I hope I am not repeating an earlier post.

I have a pair of 19’s that I have been updating. Two years ago I changed the caps and resistors and I was very pleased with the results. Now I would like to update the inductors but I am confused about the inductor values on the schematic. I have reviewed the schematic versus my crossover and I know that my C1 is 21uF as the schematic states.

The schematic looks official but I am having trouble recreating the design based upon the values of the inductors on the schematic. I know the values of the capacitors so I should be able to back calculate the inductor values.

The literature for the 19’s states that the crossover point is 1200Hz. Using several “on line” crossover calculators I am trying to reverse engineer the crossover knowing that C1 = 21uF, LF = 8Ohms and HF = 8Ohms. Using a Second Order Butterworth calculation I am able to obtain the C1 = 21uF with a 670Hz crossover point; the Inductor TOTAL (L1+L2) value is 2.7 MHz. The 19’s have two inductors in series with a combined value, L1+L2 of 3.0 MHz so if the first inductor is actually 0.3Mh that would make the second inductor 2.4 MHz. Is the L2 value actually 2.4 and not 2.7. This would help to explain why people think the 800 Hz is the correct crossover point; 670Hz is much closer to 800Hz then to 1200Hz.

If the 19’s are crossed over at 1200Hz the C1 value should be 17uF and the L1+L2 should be 1.06Mh.

I hope that this is not too confusing! As you can tell I don’t design crossovers for a living.

[Hillman]

Hey Gary, This is what they should look like when you get done. Thanks to Dave Wojo's, Mojo, When I rebuilt the X-overs, I stayed with the same values as the originals thus the stacking of capacitors. Really guys, I would not have these if Gary had not talked me into buying them. They were a mess and belonged to a band at one time. Thanks for all the help guys.

[stephane RAME]

Hello, 2 photographs of my filters has 600hz/6db and 12db, with potentimetre or autotransformer.
-GPA 515-8G For Low-Frequency Loudspeakers >600Hz/12dB
-GPA 399-8A For High-Frequency Drivers <600Hz/6dB
-GPA MR 60x40 for Horn

[DaveV]

What 2.77 mH inductors?

L2 2.7MH sorry. I had an extra 7 in there. It's been corrected in the original post.

[Zilch]

This would help to explain why people think the 800 Hz is the correct crossover point; 670Hz is much closer to 800Hz then to 1200Hz.

Nobody's friggin' MEASURED it? It's the ACOUSTIC RESPONSE of the crossover in the system that defines it. What would lead you to believe it's electrically Butterworth, even?

If the 19’s are crossed over at 1200Hz the C1 value should be 17uF and the L1+L2 should be 1.06Mh.

MEASURE!

Here's my sim (again):

http://audioheritage.org/vbulletin/s...t=12305&page=4

Here's the sim with the controls set to "Optimum." Move the green curve up ~10 dB (What is difference in sensitivity between the two drivers, HF on the horn?) to approximate the acoustic response. Where does it cross with the LF? (2, 4, 6, 8, 10,...)

http://audioheritage.org/vbulletin/s...3&postcount=49

[Bama5000lps]

Zilch - Then the schematic is correct?

Sorry for my first post.

Thanks