Page 3 of 22 FirstFirst 1234513 ... LastLast
Results 31 to 45 of 328

Thread: Altec 9844-8B

  1. #31
    Senior Member Skywave-Rider's Avatar
    Join Date
    Nov 2007
    Location
    New York, NY
    Posts
    313
    Yes, it looks much smoother, the ~3k notch has become a mere depression with the phase reversal between mid & tweeter. But there's that 4K spike, it looks bad, doesn't it? Must be approx 5 dB. And it's a narrow Q. If I moved the tweeter front/back slightly, do you think that spike would move or be cut? If I had the speakers home, I'd try that right now. So I'll play with the tweeter positioning, I should be able to move it a few inches without getting into reflections off the top -- at that wavelength were talking short -- and try to get the best notch and see what happens to the spike.

    Oh wow, I realized ur editing ur post as I type, so I'll hold off a while until the final version...

  2. #32
    Senior Member
    Join Date
    Apr 2003
    Location
    GTA, Ont.
    Posts
    5,109
    Hi Skywave-Rider,

    Zilch has covered a lot of points / here are some more ;

    I don’t know what I can realistically expect from the crossover. But I would like to improve it as much as is possible.
    - From my perspective, you do need to do a bunch of crossover redesign, to make that 3-way setup listenable for long term listening .

    I don’t know how good or bad the curves appear to you guys.
    - Honestly, IMHO ; those FR curves are fairly mediocre looking.

    (i) Overall, the lowpass section is not performing as designed with those "text-book" values. The woofer section has a 3 db down point that is in the 1250 hz area ( rather than the 800 hz area as originally intended ) .
    - You may just want to keep this lowpass section "as is" ( live with it ) & focus on fixing the hipass section on the 902/811 horn circuit .
    - Here's one reason "why" you didn't achieve a 800 hz lowpass on those woofer pairs .


    - The pic above shows the raw impedance curve for a single 414-16z ( & I emphasize, "curve" ). You'll see that the woofers' impedance is only 16 ohms over a very narrow frequency area. The area along this curve where the cap is doing it's filtering , is actually more like 25- 30 ohms ( or 12.5 to 15 ohms when two 414s are paralleled ) . This pic is from This Thread at A.A. . ( I know I've linked into it, half-way through ).
    - I'd suggest that you read the whole thread .

    (ii) The 315 hz midrange spike ( from the twin 414 woofers ), definately needs to be tamed. Perhaps Zilch can suggest a "parallel type" LCR notch filter ( inserted "inline " , to notch it out some.

    (iii) The hipass on the horn circuit ; your pic shows a 3 db down point ( Xover area ) in the 500 hz range.
    - I'd suggest you take it up to 1250 hz, to match the existing lowpass on the woofer .

    (iv) The UHF ; Well, at it's best, the 902a can get to up around 10K in a pretty linear fashion ( when a RC "bypass circuit" is implemented ). I would then roll in the tweeter at around 10K ( at either 18db or 24 db per octave ) .
    - Such a high point will undoubtably loose most of that "hump" that you see below 10K ( in the raw tweeter RTA ) .


    I want to learn and am open to your suggestions.
    Okay, I've just made some suggestions ( of a few remedial actions that I would want to implement if I owned that setup ) .



    ps ; I'll leave the rest to Zilch

  3. #33
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,963
    Quote Originally Posted by Earl K View Post
    I'll leave the rest to Zilch
    I've suggested that Convergence might have some recommendations.

    It's 902s with Symbiotic, Earl, I believe, yet to be confirmed. If they were 806s, with which I am somewhat familiar, I might be able to be more helpful. Clearly the 902s have the same excessive midrange response, which must be tamed. How they behave at the high end, I don't know, but Skywave can easily determine that by bypassing the lowpass portion of the midrange filter.

    Gonna go read the AA link now. I don't know 414 from a hole in the ground....

  4. #34
    Senior Member CONVERGENCE's Avatar
    Join Date
    Dec 2004
    Location
    CANADA
    Posts
    313
    Altec drivers don't like reverse polarity. So that design might not be suitable . Make a polarity check of your woofers with a 2.5 volt battery.
    The speakers should be pushing not pulling just in case.

    Bi amping again with todays prices is considered a real improvement over those passive networks especially with 3 way designs.

    Most Passive 2 way networks from Altec VOTT will use the same values as the computerized models. On the other site we have not encountered such problems cause most owners have replaced the caps in their speakers with outstanding results.
    .

    The reason for reverse polarity in a 3 way butterworth design has to do with phasing of HF driver.

    There are pro calculators around 100$ these will give you the right values according to RTA of the speakers.

    ..........................

  5. #35
    Senior Member
    Join Date
    Apr 2003
    Location
    GTA, Ont.
    Posts
    5,109
    Quote Originally Posted by Zilch
    It's 902s with Symbiotic, Earl, I believe, yet to be confirmed. If it were 806s, with which I am somewhat familiar, I might be able to be more helpful. Clearly the 902s have the same excessive midrange response, which must be tamed. How they behave at the high end, I don't know, but Skywave can easily determine that by bypassing the lowpass portion of the midrange filter.
    Yes thanks, I've noticed my mistake and I'll edit it appropriately .


  6. #36
    Senior Member Skywave-Rider's Avatar
    Join Date
    Nov 2007
    Location
    New York, NY
    Posts
    313
    I have 902 drivers with aluminum diaphragms. My covers (which have felts) say 902-Bs (which I believe are Symbiotiks) but I don't have Symbiotiks. Those were the stickers GPA had available.

    I am reading all your posts.

  7. #37
    Senior Member Skywave-Rider's Avatar
    Join Date
    Nov 2007
    Location
    New York, NY
    Posts
    313
    Quote Originally Posted by CONVERGENCE View Post
    Altec drivers don't like reverse polarity. So that design might not be suitable . Make a polarity check of your woofers with a 2.5 volt battery.
    The speakers should be pushing not pulling just in case.
    Hi Convergence. I did check the woofers in that way when I was sorting out the wiring. Positive voltage gives forward motion of all woofers.

    I wish I could do math. Gonna be reading a while....

  8. #38
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,963
    Quote Originally Posted by CONVERGENCE View Post
    Bring this forum over to http://www.hostboard.com/cgi-bin/ult...b=forum&f=3729 and see what the experts will say.
    Yeah, well, I just posted over there.

    [Rereading THIS thread, now, to figure out how it came to this....]

    Edit: O.K., Skywave, do this: Hook up your factory crossovers and make the same measurements without the tweeter. Let's see the woofers and mids alone, and running together. Do nearfield on the woofers again, as well.

    Also, what is the model of the stock crossover, and do we have the schematic somewhere? Provide what component values you can from your originals, please....

  9. #39
    Senior Member Skywave-Rider's Avatar
    Join Date
    Nov 2007
    Location
    New York, NY
    Posts
    313

    N800F

    I just found this shot of the rear panel (the speakers are an hour commute from home -- thank God for digital cameras provoking indiscriminate photos.)

    BTW, I am truly grateful to everybody who has helped. Can I say that again? Just did. And let's get along..........

    I believe the original N-800Fs are "potted." I'll look for a schematic. When I cut out the wiring I left just enough to reconnect in just such a circumstance. But those orig. caps have got to be crap. I will take NEW measurements using the OLD crossovers in 2 way. Actually it sounds like fun to see what the RTA will look like.

    Zilch, do I need to really remove the N800s and melt out the wax? I guess it depends on finding the schematic. The reason I'm asking is because I understand a lot of the Altec documentation is not what was actually used in manufactured product.

    Regards,
    Vin
    That's my name which u may use if u like.
    Attached Images Attached Images  

  10. #40
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,963
    Quote Originally Posted by Skywave-Rider View Post
    Zilch, do I need to really remove the N800s and melt out the wax? I guess it depends on finding the schematic. The reason I'm asking is because I understand a lot of the Altec documentation is not what was actually used in manufactured product.
    Nope, we know N800-F (N-800F, N-800-F) pretty well. I just posted the link on the Altec Forum. Ironically, it was one of their members who had the original document:

    http://audioheritage.org/vbulletin/s...31&#post160631

    Member Bfish over there indicates that crossover was used in many Altec dual-414 designs despite the lowpass filter being used for 16-Ohm drivers in other products such as Valencia 846A. See also Malibu and Carmel.

    In theory, it's "wrong" for use with 8-Ohm HF drivers, as well, but Altec engineers had more of a way of getting this stuff right than us textbook theorists sometimes give them credit for. Let's see how it behaves in comparison to what you presently have.

    If you feel ambitious, you may want to read that thread in its entirety. Adding a tweeter is not necessarily the best answer to extending the HF. If you want to stick with your Altec HF drivers, the Model 19 (and others) "T-filter" compensation may get you where you want to be more seamlessly. Read the next post there.

    Shine a flashlight into the throat of your 902 drivers. Do they have the orange plastic "Tangerine" phase plugs? If so, the prospects for success are good. We need to resolve the woofer and crossover frequency issues first, tho....

  11. #41
    Senior Member Skywave-Rider's Avatar
    Join Date
    Nov 2007
    Location
    New York, NY
    Posts
    313

    TANGERINE

    Awesome. Yes, I know the 902 has good HF extension with the aluminum diaphragm, which I have. And I do have the tangerine phase plug as well. Several members, the first of which was Tom Brennan, tried to persuade me not to go 3-way. To my ear, the original setup was not open sounding, however. (But admittedly, that's listening to an aged crossover.) So I thought it would be fun and instructive to try 3 way. And it is.

    I think I have photographed every inch of that speaker but inside the wax laden crossover. I will read that post. And I will reconnect one of the N-800Fs as soon as I am able. Cool.
    Attached Images Attached Images   

  12. #42
    Senior Member Skywave-Rider's Avatar
    Join Date
    Nov 2007
    Location
    New York, NY
    Posts
    313
    Quote Originally Posted by Zilch View Post
    Nope, we know N800-F (N-800F, N-800-F) pretty well. I just posted the link on the Altec Forum. Ironically, it was one of their members who had the original document:

    http://audioheritage.org/vbulletin/s...31&#post160631
    Haha, ur a funny guy, Zilch...

  13. #43
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,963

    Thumbs up TANGERINE!

    Quote Originally Posted by Skywave-Rider View Post
    Awesome. Yes, I know the 902 has good HF extension with the aluminum diaphragm, which I have. And I do have the tangerine phase plug as well. Several members, the first of which was Tom Brennan, tried to persuade me not to go 3-way. To my ear, the original setup was not open sounding, however. (But admittedly, that's listening to an aged crossover.) So I thought it would be fun and instructive to try 3 way. And it is.
    That's still a possibility, but let's see what's going on first. Key to taming the Altec compression drivers is to knock down their forward midrange. That brings both the lows and highs up and better balances the system overall. N800-F does a bit of that with 16-Ohm drivers; we won't know what it does with 8-Ohm ones 'til you measure the combination.

    If you read that next post, you know to take along a 6 uF capacitor (yeah, 6.2 uF is fine,) and an 8-Ohm resistor. Put those in parallel, and then the pair in series with the HF driver. That'll give us some indication of just how much HF extension your 902s actually have.

    [More measurements.... ]

  14. #44
    Senior Member Skywave-Rider's Avatar
    Join Date
    Nov 2007
    Location
    New York, NY
    Posts
    313

    REGENTS

    Quote Originally Posted by CONVERGENCE View Post
    There are pro calculators around 100$ these will give you the right values according to RTA of the speakers.
    Do you mean crossover design software? I was thinking about that. There's one Parts Express sells which seems to be popular. Unfortunately (fortunately) I have a Mac, but I can find a place to run that I'm sure. There's no way I'm going to build speakers from scratch given my living arrangements, but for the price it might be good for a guy with no mathematical abilities -- me

    I don't know if you guys know what the Regents exam is, but it is (or was) required in NY high schools. Big end of the year exam in every subject, state sponsored. You don't get a "Regents Diploma" if u don't pass. The year I had to take the Regents in Algebra (or whatever the one above that is) I knew I was doomed. I studied my ass off. My friend tried to tutor me, but he was a numbskull as well. My brain is not wired right for numbers. But I wasn't going down without trying. And tried I did.

    Well what happened was one of the few really lucky things that has ever happened to me. (Besides building this crossover, LOL.) That year, some angelic thieves stole the Regents exams, I don't know why, perhaps they were academic kidnappers holding out for ransom? Who cares. EXAM CANCELED. NO MAKEUP REQUIRED. Haha. I did not have to take that frigging test. And here I am, for better or worse.

  15. #45
    Senior Member Skywave-Rider's Avatar
    Join Date
    Nov 2007
    Location
    New York, NY
    Posts
    313
    Quote Originally Posted by Zilch View Post
    If you read that next post, you know to take along a 6 uF capacitor (yeah, 6.2 uF is fine,) and an 8-Ohm resistor. Put those in parallel, and then the pair in series with the HF driver. That'll give us some indication of just how much HF extension your 902s actually have.

    [More measurements.... ]
    OK, so conduct all the measurements with the N-800-F plus those components? No measurements with N-800-F alone?

    That's 1st order compensation filter, yes?

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Altec vs. JBL vs. TAD
    By RacerXtreme in forum Lansing Product DIY Forum
    Replies: 21
    Last Post: 10-11-2007, 02:52 PM
  2. Plantronics to Acquire Altec Lansing
    By watchman in forum Lansing Product General Information
    Replies: 10
    Last Post: 08-31-2006, 09:04 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •