Dual spider designs

makes sense to me...multiple spiders are popping up here and there, i think elemental has implemented them on the sp series, they have a damn high vas if i remember right it's 158.5 or something check the site though, and seem to model well in small boxes for a massive sub....

trying to see what you're getting at with the spider stiffness, i think basically what you're saying is that if you decrease the stiffness, but not enough to affect the linearity, so that it didn't "hold back" the motor/excursion...you'd have a higher VAS and longer throw which would be obviously beneficial? and going out on a limb, having multiple more "loose" spiders keeping it linear as opposed to a single stiff one? and finding the "compromise point" between number of spiders and stiffness of each?

if that's what you're saying...ya damn straight, not quite sure how stiff the spiders on today's drivers are compared to what they could be....but quite an interesting idea, and something worth noting to manufacturers if they aren't already working on stuff like this....

 

well I am far from a sub designer

but there are many thing that could be implemented IMO to accomplish your gaol

one of which is to use multiple "progressive" spiders.......


unless i am not understanding what your saying

 

beyond audio in humans and the new shockers have multiple spiders

 

also keep in mind that many of the subs that have multiple spiders do so simply to allow a stiffer suspension... DD uses several spiders, all of them glued together.. so n oreal added linearity there.. but it does allow for a woofer that handles gobs of power and has a fairly high fs, helping for spl...the treo csx uses 4 spiders, 2 groups of 2 about 1/4" apart... and DD claims to use 7 spiders on the 9500, though rumor has it they use from 4-6, all of them glued together in the same spot..

 

The 9515 suspension I saw had one Nomex spider on the bottom, and 6 cheap chinese linen spiders stacked on top of it. Tinsel leads were run out in-between the spiders. All were squished together to make one "thick" spider.

Multiple spiders can be an advantage if rocking is a concern; however, it is NOT an advantage from a linearity or SQ standpoint; with multiple spiders, your resulting Cms curve is the product of all the spiders. Any problem in one spider is carried on to the resulting final value. Thus you don't get the "best" of each spider, but rather the "worst" of each spider, from a Cms standpoint (stiffest spider dominates).

Multiple spiders do offer extremely stiff suspensions, which as Regal points out is a great thing from an SPL standpoint. If that's all you're after, dual or triple (or more) spiders can be a good thing. It doesn't help linearity at all, though. And significantly limits what you can do with the rest of the parameters (Fs, Qes, etc).

Dan Wiggins
Adire Audio

 

The 9515 suspension I saw had one Nomex spider on the bottom, and 6 cheap chinese linen spiders stacked on top of it. Tinsel leads were run out in-between the spiders. All were squished together to make one "thick" spider.

Multiple spiders can be an advantage if rocking is a concern; however, it is NOT an advantage from a linearity or SQ standpoint; with multiple spiders, your resulting Cms curve is the product of all the spiders. Any problem in one spider is carried on to the resulting final value. Thus you don't get the "best" of each spider, but rather the "worst" of each spider, from a Cms standpoint (stiffest spider dominates).

Multiple spiders do offer extremely stiff suspensions, which as Regal points out is a great thing from an SPL standpoint. If that's all you're after, dual or triple (or more) spiders can be a good thing. It doesn't help linearity at all, though. And significantly limits what you can do with the rest of the parameters (Fs, Qes, etc).

Dan Wiggins
Adire Audio[/b][/quote]
Exactly, Dan! I honestly don't see why people get so excited over stiff suspensions. From my perspective, I personally prefer the most compliant suspension possible for a given application. If it yields the results you want, there's no need to go overboard and make it super stiff. I see many designs where the ideal box is small to the point of absurdity. NOTHING is really gained by that, save perhaps maximum mechanical powerhandling (of course you trade efficiency in the first place for it being more stiff), so that singular advantage isn't even that great.


There's also no point in putting in a second spider if it isn't needed. DD's case, which Dan mentioned, is a uniquely bizarre one. Gluing together a bunch of shitty spiders instead of just using a single or perhaps two good spiders is hardly a good way to design a subwoofer. There is also absolutely no advantage to having them all glued together in a big chunk. I think that's rather deceptive marketing to even say that the driver has multiple spiders, since I believe most people assume that means seperate spiders (since this is the case in just about every other subwoofer design ever made).

 

I would also submit that having a high Fs isn't necessarily ideal for SPL. If you have a lower Fs, it's actually much easier to get it to peak when you tune well above it. This pays off far more so with SQ apps, allowing for much better extension and lower group delay.

Model up the 15SP, for instance. Now despite it's "high Vas" and rather low Fs, look what happens when you tune it high. It peaks like holy hell...and without sacrificing efficiency, and more importantly, without having its balls cut off when it comes to low bass.

 

Have you ever seen or heard an Inhuman in person? They are absolutely awful for anything except SPL. That Qts is so high it's basically to the point of being utterly useless for SQ. It would be horrifcly boomy and peaky in any ported enclosure, and the ideal sealed enclosure is nothing short of gigantic.

IMO, the Inhuman is a perfect example of all the negative things that stiff suspensions can get for you. Now they do well in SPL competition, not because the suspension is stiff, but because the driver has a bigger peak than Mount Everest in anything resembling a sanely sized enclosure.

 

At the nSPL comp I went to over the weekend I got to mess with some blown up MTX RFL pieces. The spider and coil were still attached so I got to see how stiff it was. It was absurdly stiff, I could barely push the coil. Is this stiff suspension what gives the RFL the high Fs? Just wondering... it would TAKE alot of power to get that thing to even move, is this somehow advantagous in an SPL comp??

 

The lower the Vas, the more mass is required to achieve the same Fs., so yes, basically, that's what gives it the high Fs.

 

I LOVE THREADS LIKE THIS!

 

I'll try and address them all:

1) Dual spider designs ARE utilized in many SQ oriented drivers, be they sealed or ported. They are not inherently better, however. If the driver doesn't NEED a 2nd spider, then there really is no point in adding one. It's easier to get one spider to behave how you want than 2.

2) Having a low Vas is not necessarily even beneficial. You want it as low as necessary for the application, and that is all. Since Vas is perhaps one of the easiest (and usually the cheapest) aspect to change, it's easy to tailor a design to a specific application with it. Say you slightly overmotor the sub a bit, you can try and accomodate for that by making the suspension slightly more compliant. It wouldn't make up for any lost extension, but you can gain back some efficiency if you ended up with an ideal box that is much smaller than the application requires.

3) As far as Fs, I don't think a higher Fs would be suited to SQ apps at all. A lower Fs translates to a lower F3, so honestly I wouldn't want it to be very high.

You are actually kind of contradicting yourself here. Increasing the Vas would make the ideal sealed enclosure larger, not smaller. Weakening the spiders would, again, make the ideal enclosure larger, so I'm not quite sure that I see what your point is here.

It can. Many companies make excessively stiff suspensions because they seem to think it's somehow beneficial to the design. As said above, dual spiders don't necessarily mean better linearity. There's no point in chucking on an extra spider if a single spider is fully capable of keeping the driver linear. Just makes optimizing the suspension more difficult.

Heavy mechanical resistance is generally not critical in sealed boxes, since the box's airspring helps supply a lot of the restoring force. If heavier resistance was all that was required, then you could just accomplish it with a stiffer spider.

It's really not that difficult to make a high excursion driver that is ideal for sealed box use. One thing that you are forgetting is that Vas is not the ONLY factor in box size. Qts plays a huge rule as well, and unlike Vas, also affects the driver's extension.

Personally, I would actually prefer to use the most compliant suspension possible to achieve the design goals I had, as this would result in higher efficiency without sacrificing low frequency extension.