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Thread: 291-16K COMPRESSION DRIVER?

  1. #1
    Senior Member doucanoe's Avatar
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    291-16K COMPRESSION DRIVER?

    I am looking at a pair of 291-16k Altec drivers. A couple of questions if i may. Have people sucessfully used these in home setups? These have #34656 thoat adaptors on them. What horn will work with these if one were to lose the adaptors?

    Man these are Big!


    RC

  2. #2
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    Hi, RC,

    Any Altec Large Format (1.4" throat), 3-bolt horn will mate to a 291. Can't remember for sure, but I think the "K" version (the latest) also had the 4-bolt-pattern tappings as well. The LF horns include most of the multicells, the 311 sectorals and the rare 511E sectoral, and many of the MantaRays, too many to list. Any Altec horn with a 3-bolt or 4-bolt pattern is a Large Format. There aren't many commercial non-Altec horns with 1.4" throats.

    For home apps, I'd consider a horn with a 90x40 pattern as optimal, but that all depends on the room size and listening distance. All Altec LF horns were intended for large areas (theaters, auditoriums, stadiums, etc.), so the larger the room, the better. New 8 or 16 ohm diaphragms of Altec quality are available from GPA.

    Yes, 291s ARE Big, Tiny Elvis would have said, "Man, Colonel, look at those things....they're HUGE"

  3. #3
    Senior Member doucanoe's Avatar
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    Hey friend!

    When I first went to look at these, I was expecting the 291-16a or b and not the "K". They are about 30lbs and the size of a small bowling ball. My buddy let me take them home to play around with. He also got a 808a driver with a 511b horn. Looking at the the 511 (2-bolt) I could quickly see that they would need an adaptor to fit the 3-bolt mounting of the 291-16k. The current adaptors are... well, I would of loved to see the horns the were originally coupled to.

    I will post up some pics this weekend.

    RC

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    RC,
    The critical part of mating a driver to a horn is not in getting it to bolt up, but in providing a smooth transition from the driver exit to a horn throat of identical diameter. Altec large format driver exits measure 1.4" ID, which is the same diameter as the throat of large format Altec horns. The 511B horn you mentioned is a small format horn with a 1" throat ID. Although there is an "adapter" that would allow a 291 to bolt to a 511B, the sonic results would be terrible, as the decreasing diameter from the driver to the horn will cause major reflections back into the driver. Those adapters are made to be used the other way, to couple a 1" driver to a 1.4" horn, where the diameter continually increases from the driver to the horn. That configuration is acceptable in most cases, but is still not as good as mating same-size drivers and horns. Altec used different bolt patterns for large vs small formats partly so they couldn't be inadvertantly combined. The horn throats on those 291s are actually a part of a horn (probably a multicell), and not an adapter.

    Whether you'd want to use a large or small format driver/horn is best determined by the sensitivity and bandwidth of what you intend to use for the low frequency component. Even small format drivers usually have to be attenuated in most apps to balance with the woofer/mid. Consider that an 808/511 combination has to be attenuated to match a horn-loaded, high efficiency woofer in an A7, and will still provide high-dB levels in a small theater......

    If you already knew all this, just ignore me, the doc told me today I've got pneumonia, so I'll be spending a few bored days on the couch with my laptop. What's worse, I had to buy 5 horsepills at $30 each, money I'd rather spend on Altec stuff......

  5. #5
    Senior Member doucanoe's Avatar
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    I hope your feeling better soon. At $30 (yikes) each, the cure sounds just as painfull as the illness .


    Actually I am learning as I go with the big Altec drivers/horns. I had a pair of Altec Iconics a while back and the had a 808A driver and a 811A horn and a 416-16Z woofer If I remember correctly. I had them attenuated back quite a bit so they wouldn't rip my head off but I really liked their tone. I appreciate all the info. you have provided to be sure. Like I said, when it comes to these large format Altecs Im still learning every day.

    Get better soon!

    RC

  6. #6
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    291 drivers

    There is a horn which I use in a home sytem with my 291-16b drivers which is called a altec 511e. Pretty well the same looking horn as the 511b but very different. The throat is 1-1/4" and it also has a rubber like coating on the outside which is used to dampin the horns vibration at high db levels. Best altec horn ever made but very rare. They come up 4 sale on ebay once and a while but dont sell cheap. Worth every penny! Good luck.

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