TD6M, must read

Posted In: Lambda Drivers


  • Participant
    cousinbillyl on #21721

    This is only a preliminary look.
    My TD6M is finally in it’s box.
    My first measurement did show the 700Hz dip. I was not upset. I’m old, and I’ve learnt a few things.

    I cut a piece of Sorbothane. This piece had a round opening ‘smaller’ than the magnet assembly. The stretchy nature of Sorbothane allowed me to slide it over the magnet. The Sorbothane now slightly covered the ‘top’ of the magnets.

    My thought; this will stop the first reflection from the ‘top’ of the magnet.

    Success. The 700Hz dip is gone. Unfortunately there is now a slight rise.

    If you give me a few weeks, I will figure it out.

    First listen, better than my Accuton C158’s.


    Participant
    eparson on #22362

    Can you post a picture of your modification and the results?


    Participant
    cousinbillyl on #22366

    Hey Parson
    The TD6M is part of a monster undertaking.

    TD15H+, TD6M, Accuton C50 midrange, Accuton BD20 Diamond Tweeter.
    I envisioned, and am developing, are you ready for this?, the Dual Cascade Fully Balanced Paralleled Series crossover.

    The post for the TD6M fix http://www.diyaudio.com/forums/multi-way/279278-4-way-series-crossover-accuton-acoustic-elegance-drivers-3.html#post4455358

    ??? not sure how to post a picture.

    At the above link I posted a few pictures,

    The basket has huge thick support posts. I stuck some closed cell foam to the inside edge. These are temporary, since they will eventually fall off. I will likely take some caulking, and carefully apply small mounds to the inside edge’s.

    I also ran a long thin strip along the edge where the spider meets the housing.

    The 700Hz anomaly was introduced because the basket needed to be really strong.


    Participant
    cousinbillyl on #22552

    A quick recap and update.

    The reflection at 700Hz is from the basket posts. It comes from the large flat portion facing the underside of the cone (6 posts). Closed cell foam works best (black in colour (here in Canada we spell color (colour))), open cell foam (white (this we spell the same)) doesn’t work.

    My crossover is a series crossover, so don’t look at my inductor value’s. Parallel crossover’s are different.

    I’ve been using copper foil air core inductors for testing. Now that I’ve narrowed down my value, 2.7mH, I’ve been listening to a lot of music. I remembered I have a couple cored inductors. I decided to listen to a Mundorf Vacuum Impregnated Zero Ohm Cored Inductor.

    Let me first recap what I’ve found over the years. For woofers, the only type of inductor I will use is cored. So no air core inductors. The cored gives me tighter and more impactful base. For tweeters, and mid ranges, air cored is best.

    What about for a mid woofer. My design is a 4-way. So my TD6M is responsible for 150Hz – 1200Hz (even though is cross’ at 1800 (still working on that). Yesterday I installed the cored. There is a fullness in the mid base with the cored. Unfortunately there might also be a slight drop in articulation higher up.

    I will listen for a few days, swap the air cored back in, listen, and report what I think I hear.


    Keymaster
    john@aespeakers.com on #22620

    There are clearly some changes as seen in the measured frequency response seen. I still have not been able to recreate this on a test baffle here. It is seen only in cabinets with approximately the same depth. The position of the dip does move with respect to depth of the cabinet though. Most all of these absorption techniques will help lessen any reflection off the inside of the cabinet. There could be a reflection from the lip around the spider, however adding a small amount of foam should not have that significant of an effect then with a resonance at that frequency.

    At this point though, we have a new frame we are going to be using as the old one is no longer available. I will get some good measurements of the new driver on a test baffle soon.

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