Dual spider designs

yeaaaa ... since most of that was less understandable than japanese to me ill just add one thing ...

while cutting apart one of my brand new RE 18" HC's ( yes i hate UPS ) to get ready for the new basket and recone kit, i found it had dual spiders ... they were not glued together though

 

Luckily RE has a good build company, and they believe that multiple spiders translates to spiders which aren't a bunch of cheap spiders glued together to function as one.

 

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.[/b][/quote]
So basically... to get a small sealed box woofer with a low Fs, the moving mass needs to be high? Or could you also make the suspension more compliant? Or does that increase the VAS (and box size?). Anywhere I can read up on parameters? Thanks

 

So basically... to get a small sealed box woofer with a low Fs, the moving mass needs to be high? Or could you also make the suspension more compliant? Or does that increase the VAS (and box size?). Anywhere I can read up on parameters? Thanks [/b][/quote]
It's kind of a little mingling of them all. If you increase Vas, and ideal box size goes up, and you tend to reduce Qes and consequently Qts, so box size goes down again, and efficiency goes up. Fs also goes down as Vas goes up.

There is more than one way to go about making a small sealed box driver, and all have their advantages and disadvantages.

 

Thanks for the info War and Sand!

 

War,

Well put! Multiple spiders are, IMHO, best to be avoided if at all possible, from an SQ standpoint. The resulting Cms curve is the product of the curves of each spider - you get the worst of each spider, not the best. Flat Cms (progressive suspension) curves are best for low distortion and accuracy, and multiple spiders work against that.

Sundownz/Sandt/anyone else...

Fs is a combination of Cms (which is the fundamental physical parameter of Vas) and Mms. If you want to lower the Fs, you must either raise Cms (make the Vas larger), or raise the Mms. No other way to do it.

Now, if you want to keep a small box, raising Cms isn't a good idea - that just increases the box size for a given alignment. So you have to add mass, to raise Mms. The drawback here is that efficiency drops - Hoffman's Iron Law still reigns supreme!

NOTE: high Mms is NOT a bad thing in terms of transient response! In fact, transient response has nothing to do with Mms - it's all dominated by inductance. If anyone wants to styp by, I can play a Brahma 12 (Mms around 260 grams) - do some sine waves up in the 10-12 kHz range? Now THAT is transient response.

Back to the main thoughts... To lower the Fs, we want to raise either Cms, Mms, or a bit of both. Why do we want a lower Fs? Two reasons:

1. Better SQ. Getting a system F3 - in car - down around 36-40 Hz yields a great bottom end. A higher Fs will raise the F3, and while you get more midbass output, you lose the real deep stuff - accuracy is lost.

2. Higher peak in SPL applications. The further distance in terms of frequency between Fs and Fb (tuning frequency), the higher the peak output. However, there is a bit of a downside, too - your peak is higher, but it is also further away from Fb, so cone motion is increased at the peak output of the system.

Now, obviously, there is a useful limit to how low in Fs you want to go! I shoot to get an F3 in the mid-upper 30s in my target sealed box. Lower than that, and I'm just (IMHO) burning efficiency. No real gain. Engineering is NOT about designing the absolute perfect piece of gear (that is for mathematicians or physicists). Engineering is about the art of compromise - finding the perfect set of compromises to get the best product possible. Give me $10,000 and I will build you the ultimate driver. Not too practical, though! If with a few well-chosen compromises I can get 98% of that performance for $400, though, THAT is engineering at its finest.

Anyway, War makes some great points - multiple spiders are good from a pure SPL standpoint, but little else. Avoid them if you can. Low Fs is, in 99 out of 100 cases, a good thing, but realize you can go overboard with low Fs. And you must consider the entire system - driver AND box - when talking about performance.

Dan Wiggins
Adire Audio

 

Definitely. I honestly don't know why so many companies make "SPL" woofers with an Fs in the mid 30s, it's just as easy to make a woofer peak hard in the same enclosure by using a much lower Fs, and you don't have to sacrifice lots of lowend in the process.

I honestly would never even consider a woofer with an Fs of above 30hz(except for perhaps 8 or 10 inch drivers) I want a subwoofer, not a midbass.

 

WOW... I too love nice technical threads like this. Thanks warbleed and Dan for the info. I found it very interesting. DAN.... you should come down here to detroit and hang out at the AES meetings with David Clark and Tom Nouisane of DLC Design. You would be a great guest speaker or just drop by if your in the neighborhood(usually second saturday of each month)

 

i just skimmed the the thread cuz im really lazy

i dunno if this has any relevence at all to anything, but im going to spew meaningless info just because i have to start college tomorrow

yea........

strokers have dual spiders
strokers have very tiny x-max
strokers need big boxes
strokers eat power
strokers are loud
strokers sound awsome


i dunno if that has anything to do with this thread, but they are pretty

 

Strokers do indeed have dual spiders, and a fairly modest xmax by today's "super woofer" standards, but they actually do not require large enclosures at all. That is a complete myth, actually. SPL competitors use large boxes to make them peak, but for SQ oriented applications, the box requirements are actually fairly modest. If you look at the maximally flat enclosures, you can see the woofer was definitely designed to peak very easily in ported boxes, not from a weak motor like many SPL subs today, but because it has a very STRONG motor. While many subwoofers now such as the XXX and the Inhuman use very high Qts to make the woofer peak in most situations because the box is much too small for flat response, the Stroker actually peaks because the box is much too large. Considerable difference between the two approaches, and the approach the Stroker takes is much more SQ friendly.

 

really
i have never actually gone and modeled up one to see what would achieve a .707

everyone i know who runs strokers(some sealed) are over 5 cubes
so i just assumed they were big box woofers


damnit now i want one again
regal sell me yours for 100 bucks

 

did the lvs have mltiple spiders too? memphisaudio? :bs:

 

Yes. Very heavily spaced spiders as well, so it should definitely have a very linear suspension. Interesting woofer, but absurdly overpriced.

 

yes it was , are the new mojo's more reasonable? :jawdrop:

 

I honestly don't have any idea.

 

damn a woofer you dont know about? I did not know that was possible!lol

 

Only have so much time.

 

yeah I get bored with audio and sell out and then wait for something to bring my intrest back into the game again.lol :dunno: