Dan - driver distortion from nonlinear suspension stiffness?

[tz]

I read the whole thread on the development of the Tumult, and came across a link where a Brahma was compared to an IDMAX (I think).

No matter, what dawned on me is that suspension nonlinearity may be a much bigger contributor to distortion than from BL.

It turns out that while x(mag) is specified as the point where BL has fallen to 70% of its rest value, x(sus) is defined as the point where suspension stiffness has increased 400% (!).

Thus it seems that the inhibiting effect of the spring force on driver displacement may be much worse than BL dropping off.

This would be at its worst w/IB, where there is no enclosure air stiffness added to the suspension's, and giving a more linear overall stiffness.

Thanks

[nismo]

I'll take a stab at this. I'm not a speaker engineer, but we'll see how close (or far my reasoning) is from the truth.

Just because the Xsus is determined by the suspension stiffness reaching 4x the rest stiffness, does not mean that it is more of a factor in distortion. Just as the shape of the Bl curve can be different, so can the curve for suspension stiffness. A standard 'linear' spider has a parabolic Cms curve. With a progressive spider, you can manage to keep the stiffness roughly the same as travel increases. This leads to a Cms curve very similar to the Bl curve of the xbl^2 motor. I believe that the Cms curve for the Apocalypse is darn near ruler flat for 95% of its travel, due to the arachnid spider setup (being a flat ribbon of metal).

My reasoning is that just because it's determined by 400% stiffness, that does not mean that it plays a part during the normal throw of a driver. The Xmax may be motor limited, and the suspension stiffness could possibly never hit 400%.

I hope Dan responds soon.

Eric

[Feandil]

Originally Posted by nismo

I'll take a stab at this. I'm not a speaker engineer, but we'll see how close (or far my reasoning) is from the truth.

Just because the Xsus is determined by the suspension stiffness reaching 4x the rest stiffness, does not mean that it is more of a factor in distortion. Just as the shape of the Bl curve can be different, so can the curve for suspension stiffness. A standard 'linear' spider has a parabolic Cms curve. With a progressive spider, you can manage to keep the stiffness roughly the same as travel increases. This leads to a Cms curve very similar to the Bl curve of the xbl^2 motor. I believe that the Cms curve for the Apocalypse is darn near ruler flat for 95% of its travel, due to the arachnid spider setup (being a flat ribbon of metal).


Eric

You're 100% correct here....

the 95% of rest in fact is not inherent to the 4 flat spring method for suspension used in the arachnid suspension... however generally springs can be designed to in fact be nearly 100% progressive (with MANY different materials used from copper alloy to normal spring steel)

I have never heard of the apocalypse subwoofer, however if it uses the Adire arachnid suspension you're correct....

this does not discount that you will still run into what is called the "Cms wall" all that means is that suspension was designed to be inherently flat over the range of movement (which is easy for 20-30mm one way but difficult for 200-300mm one way)

as far as distortion... those two things are absolutely KEY for subs... or for any speaker in fact, but most important in subs

flat BL <<< easy to achieve and there is about 10 different ways to achieve this cheaply
flat compliance <<<< inherently harder with normal cloth spiders but far easier with just about any springs

these two things IMO are the simplest and most drastic reducers for distortion... both are realitively simple to achieve with some thought, even with regular overhung drivers

all the rest of the distortion products can be realitively easily engineered around if you have a great basis like flat CMS and flat BL (though both will inevitably fall off at some point)

stiffness of cone = easy
removing resonances = easy

I would consider CMS and BL to be the backbone of low distortion and any drive claiming great SQ better use a very nice progressive spider

[Hobbes26]

Originally Posted by Matthew_Rich

flat BL <<< easy to achieve and there is about 10 different ways to achieve this cheaply

I can't think of that many... can you elaborate?

[nismo]

I don't know of 10, but:

underhung
split coil
faraday's

Eric

[Feandil]

Originally Posted by Hobbes26

I can't think of that many... can you elaborate?

overhung with extended pole
T- overhung motors
underhung
X-underhung (our technology)
Split coil
XBL2
LMT
full length faradays with extended pole

few others that slip my mind

still the best to this DAY is the old underhung... cheap, extremely light coils, extremly high BL and low driver mounting depth

our X-underhung only improves on that slightly giving you that much more mounting depth (it's in fact less motor depth that any type of motor in existance per given excursion)

not really any info on that cause we're still filing patents

the flattest BL is achieved through underhung and classic overhung faradays with extended poles... they're the flattest of any method I can really think of

LMT is close to that flat... but not exactly

and XBL2/Split coil will undoubtably have issues keeping ridiging out of the BL

[tz]

"I believe that the Cms curve for the Apocalypse is darn near ruler flat for 95% of its travel, due to the arachnid spider setup (being a flat ribbon of metal)."

That's obviously exceptional, and evades the question about a x(sus) = 4X increase in stiffness.

But I thought about it some more since I posted, and what I didn't account for is the importance of the actual numerical values of BL force vs. spring force.

So the answer could be anything.

" still the best to this DAY is the old underhung... cheap, extremely light coils,"

Cheaper coils, but aren't they pretty cheap to begin with?

I thought underhong was quite expensive because instead of a longer coill you need a longer magnetic field = more expense for magnets.

[Feandil]

Originally Posted by tz

"I believe that the Cms curve for the Apocalypse is darn near ruler flat for 95% of its travel, due to the arachnid spider setup (being a flat ribbon of metal)."

That's obviously exceptional, and evades the question about a x(sus) = 4X increase in stiffness.

But I thought about it some more since I posted, and what I didn't account for is the importance of the actual numerical values of BL force vs. spring force.

So the answer could be anything.

" still the best to this DAY is the old underhung... cheap, extremely light coils,"

Cheaper coils, but aren't they pretty cheap to begin with?

I thought underhong was quite expensive because instead of a longer coill you need a longer magnetic field = more expense for magnets.

I was speaking about the topography as a whole as no grooves etc need to be machined nor royalties paid, nor extra careful windings for Split coil, nor huge complicated coils for LMT

split coil is very very heavy... high mms etc

underhung is extraordinarily simple to manufacture (it's like manufacturing the most common overhung) and the coil can theoretically be the lightest possible as excursion is only based upon the gap height and not any relationship between grooving and coil height (you'll find that XBL needs almost a 80% longer coil than underhung, just in general)...



in fact you could theoretically have a 20-30 layer VC and have the smallest mounting depth of any speaker per given excursion

in fact no magnet costs generally don't rise... at least not enough to matter versus machining costs generally speaking

generally XBL has about the same magnetic gap height as underhung and therefore you have magnetic loses there as well

magnetic force is simple to compensate for and you need no huge magnets to do it (tall I mean) as the depth is all top plate...

this allows for the MOST effective, cost savings, and environmentally friendly method to speaker design

a very very wide thin magnet (in fact 5mm tall is enough in MANY cases) and this will generally be cheaper and give MORE flux vs. a solid tall less wide piece.... thin ferrite is very very very cheap... thick ferrite is NOT ... N35 is the same... but times that by several orders of magnitude in prices

I think the whole thing is the "love factor"

"ooooo new technology PRETTY"... when the classic ones work fantasticly in fact better than any new fangled ones overall IMO

[Steven Kephart]

Originally Posted by Matthew_Rich

overhung with extended pole
T- overhung motors
underhung
X-underhung (our technology)
Split coil
XBL2
LMT
full length faradays with extended pole

few others that slip my mind

still the best to this DAY is the old underhung... cheap, extremely light coils, extremly high BL and low driver mounting depth

our X-underhung only improves on that slightly giving you that much more mounting depth (it's in fact less motor depth that any type of motor in existance per given excursion)

not really any info on that cause we're still filing patents

the flattest BL is achieved through underhung and classic overhung faradays with extended poles... they're the flattest of any method I can really think of

LMT is close to that flat... but not exactly

and XBL2/Split coil will undoubtably have issues keeping ridiging out of the BL

Says you.

I don't understand why people think that just because Adire can produce a flat BL motor topology, anyone can because it's easy to do. What people forget is that Adire is founded by two engineers; Dan Wiggins, a brilliant engineer with a great deal of experience and respect in the audio industry, and Dr. David Hyre, who holds a Doctorate in Nuclear Magneto Resonance Spectroscopy and probably understands magnetics as well if not better than anyone else in the industry. When people come along and make such brash claims, you really need to find out what kind of integrity they have before believing their claims. Do they really know what they are talking about, or are they just some forum know-it-all that has an opinion about everything?

Of course underhungs are the best, which is why EVERYONE uses them, right?

[Feandil]

Originally Posted by Steven Kephart

Says you.

I don't understand why people think that just because Adire can produce a flat BL motor topology, anyone can because it's easy to do. What people forget is that Adire is founded by two engineers; Dan Wiggins, a brilliant engineer with a great deal of experience and respect in the audio industry, and Dr. David Hyre, who holds a Doctorate in Nuclear Magneto Resonance Spectroscopy and probably understands magnetics as well if not better than anyone else in the industry. When people come along and make such brash claims, you really need to find out what kind of integrity they have before believing their claims. Do they really know what they are talking about, or are they just some forum know-it-all that has an opinion about everything?

Of course underhungs are the best, which is why EVERYONE uses them, right?

steven... if that's your only proof... that since "everyone" doesn't use them they aren't the best???

huh... so I guess classic short pole overhung is the best correct because it's the most widely used???

please steven I don't want to get into a debate on creditials ok... there are PLENTY of people far far older than dan who agree with me (the name DB ring a bell?)

David Hyre graduated from my university.... Duke University....

if you wish to actually discuss why underhung is better I will oblige... it's MY OPINION though what benefits outweigh what costs my friend... dan's opinion is obviously different... depending on how you weigh in salesmanship

it is realitively easy to do my friend.... especially if you choose underhung... however a extended pole overhung is nearly as easy to do with a simply finite magnetic simulation program and a nice FEA (though we use our own custom programs to run these)

modeling up the classice 1:1:1 XBL2 motor and you'll see why there's those ridges... yes you can eliminate them... but then it becomes underhung!!!

but I'm not here to preach to you why people believe they should use other technologies... nobody in their right mind would assume LMT is better than XBL2... but people still use it... ever heard of the term marketing my friend???

BRILLANT (irish accent)