AV15 Spider


  • Member
    Travis Gibby on #65

    Does the AV15 have linear spider or a progressive spider?


    Member
    R. Buszka on #1381

    I believe they are linear spiders. And there are two of them. Every aspect of the AV series design was chosen to be so for a reason.


    Member
    Travis Gibby on #1382

    Thank you Buszka. That’s what I thought from looking at it. Does that mean that it is not well suited for a vented enclosure?

    Travis


    Member
    simon5 on #1383

    It’s well suited for vented enclosures or sealed enclosures, you choose.


    Member
    Travis Gibby on #1384

    Thank you Simon,

    I was hoping to hear that. The reason I asked is because Dickason cautions against using drivers which employ linear suspension systems for vented enclosures. He reccomends only using drivers with progressive suspensions for vented enclosures to counteract the oil-can effect. Do you guys have an opinion on this?

    Travis


    Member
    Admin on #1385

    Travis, up until a few years ago nearly all spiders were linear. Vented enclosures have been used for 50+ years with those linear kind of spiders. Many progressive spiders do wierd things that make them less desireable. They often do not work the same in the inward and outward stroke, causing other non-linearities. The intention is to have the Kms curve of the suspension to be as flat as possible. The linear spiders used in the AV woofers have a pretty flat curve out to over the 20mm range, making them quite linear within the specified Xmax range.

    There is no problem using them in vented enclosures at all.

    John


    Member
    Travis Gibby on #1386

    Thank you John,

    That confirms some of what Wiggins has written about non-linear Cms curves. I wonder why Dickason didn’t mention any of this in the LDC. I guess different experts have different opinions.

    If you have any refrences on this subject I would be interested. I read a doc about it on Kippel but it’s been awhile. Maybe I will start there.

    Thank you,

    Travis


    Member
    paulspencer on #1387

    Travis, sometimes a little bit of knowledge can be a bad thing. I suggest you might be better to focus more on distortion, as this gives you a picture of performance after the complex interaction of such factors have their effects. Everything works as a system, and if you think driver A is better than driver B because of the suspension system, you aren’t really comparing properly.


    Member
    Travis Gibby on #1388

    Travis, sometimes a little bit of knowledge can be a bad thing. I suggest you might be better to focus more on distortion, as this gives you a picture of performance after the complex interaction of such factors have their effects. Everything works as a system, and if you think driver A is better than driver B because of the suspension system, you aren’t really comparing properly.

    No disrespect Paul, but I find your post a little condesending.

    First of all I never made any claim about any driver being better or worse than another. If I had felt that the driver was inferior than I would not have purchased it. My question was about the suitability of this driver for a vented application.

    The reason that I asked is because in Dickason’s LDC, he talks about linear and progressive suspensions:

    It seems intuitively evedident that the best type of suspension would be one which would provide uniform restoring force throughout its range of travel. While this can be true for closed box type speakers wher the compliance of the air within the box acts as a restoring force on ht cone, the exact opposite is true of drivers in vented cabinets.

    he goes on to say:

    The offset probem, a nonlinear phenomenon, occurs as the driver is being driven towards its Xmax limitation. As the coil moves to a position where more turns are out of the gap, Bl decreases, back EMF decreases, and the coil draws more current, pushing the coil even further out of the gap and thus creating distortion.

    A progressive suspension system can counteract this nonlinear offet problem.

    Unfortunately, many amateur audio designers seem to be unaware of this fact, since it is not uncommon to find a woofer with an extreemly linear suspension system being used in a vented application.

    If you have some information to the contrary Paul, please post it as I do make room for the possibility that Vance Dickason was wrong here.

    Travis


    Member
    paulspencer on #1389

    No disrespect Paul, but I find your post a little condesending.

    I didn’t intend to come across that way, but looking back at your question and my post, I can see how you could feel that way. My apologies.

    First of all I never made any claim about any driver being better or worse than another.

    Point taken.

    I’ll try to make my point in a better way …

    I see a lot of new diy enthusiasts, especially with subwoofers, focusing on just one factor and over-emphasizing it. It might be they think low Qts drivers are inherently more accurate or that subs with big magnets are better, or that driver XYZ with a lighter cone will be more “fast.” The problem is when you know something (or think that you do) but don’t have enough knowledge to assess correctly how that fits into all the other interrelated factors within the system that will create the performance.

    So my intended point was this: be wary of making decisions on the basis of just one factor unless you have enough knowledge to understand all the factors involved. This is probably beyond all but the most advanced of diy enthusiasts.

    It’s a fair question you have asked. I’ve been reconsidering my views on what is ideal regarding BL curve and Kms curve. Recently I saw some measurements of the Peerless XLS and noticed that the Kms curve (suspension vs excursion) and BL curve (motor strength vs excursion) were close to the inverse of each other, ie. as the motor strength decreases with excursion, the suspension becomes stiffer to keep distortion down with larger excursions. I had though that a completely flat BL curve is ideal, but this would only be the case if the suspension were flat as well. Adire have managed (TC sounds as well) to get a very flat BL curve, but have they managed to get the suspension equally as flat?


    Member
    Travis Gibby on #1390

    Thank you Paul,

    I accept your appology. I know you weren’t trying to come across that way.

    I agree that you cannot choose a driver based on one parameter as many people do. I have been building subs for ~ 6 years and suspension type has never been a factor in my decision of what speaker to use and for which application. Recently I was going over the LDCand in the first chapter, the one I never read, I found that Dickason believed that linear suspensions were not as well suited for vented applications. Other engineers seem to disagree so I’m hoping that Dickason is wrong in this case because I really want to use it in a vented enclosure.

    Travis


    Member
    simon5 on #1391

    I think Adire, TCsounds, Acoustic Elegance and many others can easily get a fairly flat suspension curve. I remember seeing many Kms curves mirroring the BL curve.


    Member
    Travis Gibby on #1392

    Yeah, I think that this may be Dickason’s opinion rather than a matter of fact.

    I found that article by Dr. Wolfgang Klippel, and he said that progressive suspensions may be used in high power applications to prevent mechanical faliure, but that they also increase distortion.

    Like John said, vented enclosures have been around for a lot longer than progressive suspensions.

    Travis

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