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Thread: ALtec Model 19-XO upgrade discussion

  1. #1
    Gary L
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    ALtec Model 19-XO upgrade discussion

    This discussion was moved from another thread and might be a good one for here in the DIY section.
    Many have tried numerous upgrades on the 19 XO with varying results.
    Lets discuss what you have done and what the results have been.
    I will start it from my very basic knowledge with a photo of the XOs built for me by member PaulC. I am sure he will join this discussion and hope to see Zilch, Dwojo, Dylan, Tom Brennan, RonSS and all you others who have interests in this area.
    Here is what PaulC built for me.
    Jeff Markwalts schematic was most helpful here and his input could be most valuable for this discussion.



    Gary

  2. #2
    Senior Member Dylanl's Avatar
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    All that I upgraded was the caps becuase I didn't want to change the flavor of the speaker. Lots of VooDoo about these X overs. Since the change, the mids and highs are cleaner but I have no way of measuring. Sorry if I keep boring you with this picture but it was what we were discussing
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  3. #3
    Senior Member Dylanl's Avatar
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    I have also listen to this passive pair on a friends set of 19's. My perception was better bass and similar mids and highs. If I remember this set bypassed the tone controls on the front of the speaker.
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  4. #4
    Senior Member Dylanl's Avatar
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    Here is what mine looked like to start
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    Senior Member Tom Brennan's Avatar
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    Some fella built these outboard 19 crossovers, I forget who, but that's what I'm inclined to do. That way I won't bugger up the stock ones; note that just because something sounds different doesn't always mean it's better. Berenek's Law and all that.

    Anyway it would be good to have the stock crossovers and seperate modded crossovers, then one could compare.

    To tell you the truth I'm enjoying my "new" 19s so much as they are I'm not too worked up about crossover mods anyway. Not yet anyway. ;-)
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  6. #6
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    I'm Paul C. that built GaryL's Model 19 crossovers.

    Gary sent some Model 15 stripped chassis that are identical but for marking on the faceplate, as well as some new 8 ohm L-pads and knobs.

    I have the Model 19 schematic so, it was time to order parts.

    Inductors... I got a Jantzen .33 mH 15 ga aircore to use for the .3 mH, and a .8 mH 18 ga aircore to use for the .77 mH specified in the schematic. These differences in values are so small as to be inaudible.

    Since the .33 mH was to be in series with the woofer, the 15 ga was chosen so as to have minimal resistance. The .8 mH (or .77 mH) inductor is a shunt to ground in the HF section, and the resistance is not a real factor in performce.

    For large inductors, anything from 1.0 mH on up, I use iron core inductors. They are smaller, use less wire, and have less resistance than the same value in an air core. Plus they are cheaper, only 1/2 or 1/3 as much. The problem of "saturation" of iron core inductors only happens at power levels of hundreds of watts, and even then, only momentarily. At those volume levels "high fidelity" is not a priority, and even then, unlikely to be noticed. Besides, the originals are iron core, or "transformer" type inductors. Iron core is the practical choice here.

    Caps used are Dayton polys. For very larger values I usually use electrolytics, but none were needed here. Again, I made a few value substitutions. 8.2 uf was used where the 8.0 uf was specified, and 6.2 uf was used where the 6.0 uf was specified. These are certainly close enough. Also, 4 ohm resistors were used for the specified 3.9 ohm resistors, and "close enough for jazz".

    The large iron core 2.7 mH inductor was screwed to the chassis. The two aircore inductors were strapped to the chassis with Ty-Wraps, as well as being stabilized with blobs of glue so they would not vibrate. They were oriented to minimize crosstalk.

    The caps and resistors were glued to the chassis and to each other. Hot melt glue is not used, it may damage capacitors and does not stick well to metal. I use a glue I have found to be perfect for this use, E6000 by Eclectic Products. There is a similar glue, a little more solvent so it is thinner, called Aleene's Platinum Bond 7800 that works well, too. These glues can be found in hardware, hobby, and craft stores. I get them at Walmart in crafts. These glues are "SBR adhesives", that is, Styrene Butadyene Rubber adhesive. They dry clear, and are very slightly rubbery. They do not give off acetic acid like some silicones. They are flexible when dry but much firmer than silicone. I keep both E6000 and 7800 in my shop and go through at least a tube a week. Great for gluing dissimilar materials, and sticks well to metal, too.

  7. #7
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    Very nice!

  8. #8
    Gary L
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    Thanks Paul, very informative.
    I have read many threads regarding guys who tried different Caps and coils with terrible results.
    Not understanding the electronics behind these results or the reasons why one brand of cap or type of coil produces poor sound is one of the reasons I started this thread.
    To those of us who are not up to speed on this tech stuff it is very difficult to understand why a Poly cap may or may not work or why an iron core sounds different from an air coil. Even harder to understand why one brand of Poly cap with an X value would sound different from another brand of Poly cap with the same X value.

    Then there is always plenty of discussion on the best Hz to run 19s on.
    Some swear by the 800Hz while others claim the stock 1200Hz is best.

    Others here have completely done away with the adjustment L pads and like that better.

    I know Dave Wojo rolls his own XOs and is very happy with the changes he makes and others have discussed in many threads other types of crossovers, maybe ACTIVE, if I remember correctly. Still others claim that bi amping is the way to go with 19s.

    Talk about confusing!

    It sure would be nice to get a grocery list of upgrades and what results have been found.

    I am a sort of purist in that I prefer 19s to sound just like 19s the way they came from the factory. Replacing caps with ones that work right is easy and relatively inexpensive if we know what ones to use.

    I have no problem with anyone who wants to completely rework or change any of their XOs to anything they want but I have to say the 19s gained a place in our hearts by simply being 19s and sounding the way they do.
    I don't doubt they could sound better with some tweeks but many of us don't have the knowledge, ability or desire to do it.

    Gary

  9. #9
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Dylanl View Post
    I have also listen to this passive pair on a friends set of 19's.
    You might suggest that your friend remove that bolt from the core of that inductor... I doubt that is an aluminum bolt and wing nut... if you must run a bolt through the core of an inductor, use brass.

    Placing a steel bolt changes the value (increases) and will easily saturate at higher power levels.


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    It is confusing Gary. I learned some time ago that different caps can and do alter the sound in electronics. I tried a lot of different caps in an amp rebuild before I found a brand and type that came very close to the sound of the original Sprague "Bumble Bee's" that were in the amp. Preserving the sonics was the only way for me because I choose that particular amp for it's known sonic quality. (Mac 225) Yet some people buy vintage equipment and use "audiophile" parts and "upgrades" that greatly alter the original sonic signature. I should add that I had used the amp for a long time. The original caps were not shot and I had become very familiar with the amps sonic signature. I figured it was a matter of time before the caps were trash so I recapped before a problem like red glowing output tubes showed up. Hard to say if either approach is right or wrong because that argument seems to go on and on in other places. Matter of sonic taste I guess. Then I discovered that different caps do alter the way speakers sound but I'm way more critical of a cap in series with a tweeter as that's where I hear the biggest difference. I got my 19's and they sounded good but somewhat distorted so I replaced the caps with ones I had on hand. I didn't like the results because they sounded very harsh but the distortion was gone. I then ordered a brand and type of cap I happened to use in my Flamencos with good sonic results and they were lots better sounding. Not having had the 19's for years is a draw back because I never heard them with "fresh" factory caps so all I had was the that two week sonic memory of what they sounded like with the aged caps but I seem to be satisfied with the new caps. For ha ha's I replaced the large inductor in series with the woofer with a steel core of low resistance and the bass increased more than I expected plus it seemed to be tighter and more extended downward. After enjoying the increased bass for a few days something started to bother me. The human voice was too chesty and some snap was missing in percussion. I put the original Altec inductors back in the circuits and the bass really diminished but voice sounded more natural and that snap came back. Now I miss the better bass but I don't want that heavy chesty voice and muddy lower mid either. One might say that the woofer was more efficient with the "better" lower resistance inductor but raising the level of HF horn doesn't seem to be the solution because that creates another problem. My experience makes me wonder what other peoples experiences are when changing to "better" inductors. I did a quick reading of the original inductors (supposed 2.7) and as I recall they were both below the 2.7mh shown on the xover schematic so that makes me wonder too. The new ones I used were exactly 2.7mh. Then there's the other two inductors! I have yet to totally remove the original inductors and repeat the readings being sure that my LCR meter is properly zeroed but the fact that the new steel cores made such a huge difference points me in the direction of building proto xovers on the floor in front of each speaker. A full new xover to start then if I don't like the results tryng different inductors and even different values to see what the heck is going on. Has anyone else measured value and resistance of the original inductors?
    When I got my Flamencos I had more or less the same experience. I built new xovers with "better" parts but I hated the results. I went back to the original inductors, original wirewound resistor and HF level pot and just used new caps. The sound was so much better so there is something going on that needs further explaination. At least to me.
    I guess we all have our own sonic preferrence but it's sure helpful to understand why certain things that seem so straight forward make such big changes and not always for the better.

    Dave

  11. #11
    RIP 2011 Zilch's Avatar
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    Is this the subject schematic?

    For reference, here's the link to my voltage drive analysis:

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

    And the CBS Tech Center results are here:

    http://www.perfectmarketaudio.com/al...20page%201.pdf
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    Yes that's the xover. I had previously printed that info out and I read it. Now here's a new twist on my experience that makes me feel pretty stupid. At least I admit it. LOL After my last post I played some music and something pretty simple occurred to me. Here's the long story: When using the Flamencos I couldn't live with them without an added tweeter. I figured that would be the case with the Model 19's and it was. Even though the 802-G's have a more extended response and they were just redone at Great Plains,they still fall short of what I like in the way of extended solid highs. Based on the CBS Labs report of the Model 19 I can see why. The HF response drops off too early then like a rock and raising the HF pot to compensate doesn't sound good to me or satisfy me. Running the 8 ohm EV T350's with a simple 2uf cap and 1 ohm resistor is series with them straight from the amp does satisfy me if I turn the HF pot on the xover to the 12 o'clock position, or below optimum. Even though the EV's drop like a rock after 14 or 15KHZ the overlap with the 802's really does open everything up and that was well within the ballpark for me even though it was somewhat bright at times. With all my previous speakers I always had the preamp bass and treble set at + 4db to get what I liked so I assumed that was where it needed to stay. I turned the bass and treble controls to the flat position and played bands on many LP's I have had for years and have heard thru several different speakers I've owned. All I can say is WOW. Everything fell into place so well that I have never heard such extended response, smoothness, clarity, balance and impact from any speaker with flat tone control settings! Seems that replacing the woofer inductor brought the bass up plus it hit the 4db bass boost that wasn't just a boost below 100HZ. Live and learn. Now my 19's sound so darn good they really don't need anything but I know I'll be in there replacing those inductors again. This time I expect that the bass will be "better." I imagine tone control curves play a part in this too and in my case the increased woofer output plus the 4db boost was way too much on the upper woofer response. Guess I never thought I'd have a system that came together so well as to be flat enough without preamp frequency compensation to please me yet not so flat to be boring like some "flat" systems are. Now I wonder if that was my problem with the Flamenco bass and the better inductors? I do know that after that I tried "flat" tone control settings with the Flamenco/EV combo and it didn't sound as good as with the +4 bass and treble boost.

    Dave

  13. #13
    RIP 2011 Zilch's Avatar
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    There's other ways to get extended VHF if the horn will support it.

    I'll try to borrow an 811B and 802-8G here locally and give it a try.

    Others here may have already worked with this....

  14. #14
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    Quote Originally Posted by Zilch
    There's other ways to get extended VHF if the horn will support it.

    I'll try to borrow an 811B and 802-8G here locally and give it a try.

    Others here may have already worked with this...
    - Well then,,,,good luck with this .

    - A couple of significant hurdles that you'll need to overcome are ;

    (i) The 2 relative sensitivities of the drivers ( 802-8G vs the 416-8B or 416-8C ) are closer to each other than any of the typical JBL 2-way systems . ( You'll likely need to limit your design to a 95 db / 1 watt system ). Load resistors can help out here by lowering the woofers efficiency .

    (ii) Altecs "8 ohm" compression drivers should actually be considered as 8 ohm loads ( unlike JBLs "8 ohm" types which ought to be considered @ 6 ohms . This 2.5 db difference literally comes off the UHF top ( of what "balance" is ultimately possible from any HF compensation scheme ) .


    - ( biamping being my favourite approach to both of these dilemmas ) .


  15. #15
    RIP 2011 Zilch's Avatar
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    Thanks, Earl.

    I'm thinking see if the stock horn/driver will "push" to, say, 16+ kHz like 4430, with usable vertical beamwidth, or,

    Use an alternative driver requiring less compensation to get there and above.

    HERESY! Tangerine RULEZ!

    [WAIT! That's Klipsch.... ]

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