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Old 8th November 2011, 12:47 AM   #11
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Quote:
Originally Posted by markaudio View Post
Alpair 10 Gen 2. Its a driver that I've built right up to the limit. Its cone is less than 1000 micron thick. With its trick coil, its strictly a low load driver. Take a look at the Makraudio forum for advice on how to use this driver and other Markaudio driver, there's plenty of comment on various threads.

Cheers
Mark.
1000 micron is like, one millimeter?

For the rest I have to agree with Mark that it is horses for courses.

vac
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Old 8th November 2011, 01:44 AM   #12
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Hi Art, (Guys),
Your making assertions that aren't correct.

I'll be 100% clear about this: No Full-Range maker designs their drivers to operate at X-Max for sustained periods. Very few commercial domestic makers (if any) will guarantee their drivers to operate at X-max for sustained periods. If you take ANY Full-ranger or typical smaller driver close to its X-Max regularly, you'll either break the cones, or stretch the suspensions. Either way, the drivers will soon out of operational spec.

Most commercial testing operates drivers for up to 100 hours at X-max. If the driver holds up, it passes. For Full-range drivers, the test loads are much lower. Typically, testing is done over longer periods (250 to 500 hours) at up to 25% of X-max.

Markaudio drivers are capable of operating to their quoted X provided its for Non-Linear loads. On most music, there will some output that Full-Range driver designers call "snap load", or "shock load". For Full-Designers, there's 2 choices; We can choose to ignore the shock load (coil moves out its gap), or we can design the power-train with an extended coil design to dynamically balance it and thus record the shock load. But we only do this for non-linear (not regular) loads due to the need for wide band emittance which demands a low mass design. All Full-range designers have make a judgment on what mass penalty must be paid for getting the cone to emit a wide band.

Cheers
Mark.
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Old 8th November 2011, 01:47 AM   #13
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Originally Posted by weltersys View Post
You donít list the Xmech (AKA Xlim) figure on the specification sheet.

If you are recommending the cone should not move more than 4-mm (1 way) safely on transients, which is only 8 mm peak to peak, you should revise the PDF showing Xmech as 4 mm and perhaps not bother listing an Xmax of more than double that which you seem to think may cause cone damage.

Art Welter
You are of course absolutely correct. If the motor is linear out to 8.5mm one way, yet the moving parts of the driver cannot accomplish this without damage, then an Xmech parameter needs to be defined, as, like you said, something like 4mm one way.

I tried bringing this objectively and with examples to Marks attention in the "alpairs-arent-woofers" thread but ended up having a bunch of my posts deleted...

Once again Mark, people are damaging your drivers from over excursion. If they cannot operate at the specified Xmax without damage then you need to define the Xmech. It's exactly why the Xmech parameter exists.
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Old 8th November 2011, 01:51 AM   #14
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Art, iirc, 5thElement posted some comments in that alpairs aren't woofers thread back when it was started. Mark wasn't thrilled with his comment and deleted them. Here Mark can't do that. Mark is right. They're not woofers. And they're full range drivers bound to the same laws of physics as every other full range driver. But I also agree with you that xmech is 4mm and xmax is 2mm based on what Mark has said. Possibly xmech is 8.5 and xmax is 4mm based on what was said.

With that, my EL70s still pump like crazy. They're paper though, so perhaps more tolerant.
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Old 8th November 2011, 01:52 AM   #15
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Quote:
Originally Posted by vacuphile View Post
1000 micron is like, one millimeter?

For the rest I have to agree with Mark that it is horses for courses.

vac
Hi Vac,
Apologies, I keep using my engineering brain. We start with a stock material and use Multifrom which consists on several press processes, we get the final cone mean profile thickness to around 100 to 200 micron (0.1 to 0.2-mm) depending on the calculated power-train mass requirement for a particular model.

Thanks
Mark.
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Old 8th November 2011, 01:57 AM   #16
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Quote:
Originally Posted by dainrobert View Post
What would be a safe threshold power level to feed the speaker? What would be the upper limit of output SPL for extended periods? I intend to run these off a small tube amp to play soft music and vocals, but I do expect to get at least six years of service form such an investment!
Hi Dain,
If you design your box and driver combo so its near optimal and suitably sized for your room, you'l likely only use about 25% of a driver's quoted X-Max for the majority of music. From what you've written, you'll easily get 10+ years from Full-Rangers.

Cheers
Mark.
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Old 8th November 2011, 02:18 AM   #17
rjb is offline rjb  New Zealand
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I support Mark in one way, having had paper drivers, (not his), damaged by others who ran them continuously overdriving on rock music, even though the amp power was within ratings. The same drivers on classical used at similar levels were not damaged.

I have always understood the manufacturer's ratings were maximum allowable peak, ie intermittent. Traditionally HIFi manufacturers have in the past spec'ed accordingly. and try to maintain sound quality of the peaks. Occasional peaking does not result in fatigue.

But hard rock is not "intermittent", and I think pro drivers recognise this, and design for mechanical robustness, and don't worry too much about what it does to the sound at near maximum levels. (I've put that badly, but you know what I mean). Running close to peak limits all the time will result in fatigue.

KEF in fact in the B110 ensured the cone hit the frame and produced a rattle well before it reached its linear limits. I've reached this on Rock, but never heard it on classical. The B110 is a robust and heavy cone with limited frequency range. I would never expect a very light small driver of 3 or 4 inches to handle rock very well at all.

So I think there is a case for different ratings according to the type of music, or the intended use.

Maybe Mark can devise an additional specification that recognises this. I don't think the suggestion of Xmech does this.
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Old 8th November 2011, 03:02 AM   #18
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Hi RJB,
Your comments are objective, thanks for them.

The essential problem for Full-Range (and most commercial limited range) driver designers, is we don't have any control over the use and operation of the drivers. Such is the variety of musical load output placed upon drivers, it has to come down to end-users to recognise the general limitations of driver types.

For example, I' seen Alpair 10's being pushed here by local end users to in excess of 6-mm (1 way) on several dramatic classical music tracks. Very effective at creating the "drama" in the music. I design a driver's power-train with a "long throw" to cater for this aspect of musical performance. But we're talking about a few seconds on drum roll and similar. That's a long way from then being able to play heavy duty beat music with much regularity. There's no way ANY Full-Range driver designer can cater for a near constant heavy LF load.

Hense, no maker of domestic (home hi fi) driver is going to state that their drivers will constantly operate at X-Max without sustaining damage.

All I can do is offer practical advise and hope it helps as many members as possible. I'm caught in a catch 22 trap. My drivers are x'max capable so like all other makers I state the run load. This is within the context of typical "Full Range" applications. Unlike most other driver makers, I do my best to engage with end-users with help and advice on the operation of drivers. A few members keep making assertions that are technically wrong. They assume they know more about driver design and specification than I do. I have err on the side of restraint as I've no wish to create conflict while at the same time, try to help the majority of members with their hobby, not an easy balance at times. On my section, where a member keep making an assertion that is incorrect to point where it potentially mis-leads others, I have no option but to delete.

Cheers
Mark.

Last edited by markaudio; 8th November 2011 at 03:08 AM.
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Old 8th November 2011, 03:04 AM   #19
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Quote:
Originally Posted by tuxedocivic View Post
Art, iirc, 5thElement posted some comments in that alpairs aren't woofers thread back when it was started. Mark wasn't thrilled with his comment and deleted them. Here Mark can't do that. Mark is right. They're not woofers. And they're full range drivers bound to the same laws of physics as every other full range driver. But I also agree with you that xmech is 4mm and xmax is 2mm based on what Mark has said. Possibly xmech is 8.5 and xmax is 4mm based on what was said.

With that, my EL70s still pump like crazy. They're paper though, so perhaps more tolerant.
This needs to be cleared up a little because the definitions are getting slightly blurred.

On an overhung motor the Xmax parameter typically defines the excursion that the motor is capable of whilst leaving the gap completely filled with the voice coil.

There is one other definition that I am aware of that states Xmax is when the drivers distortion has increased to 10%THD. Under this definition, the motor could still have the gap completely filled with coil but if the mechanical parts of the driver impede the linear motion of the cone then distortion will rise. This happens with the B&W FST drive unit to an extent as the surround is as good as non existent and the distortion of the driver goes up way before the motor should start to lose linearity.

Marks drivers of course don't really fall into the second category and I'd expect they will keep their distortion low, beyond what would be the safe operating Xmech, as the motor should still be pretty linear. Of course keep that 10% THD drive level up at low frequencies and the cone will deform and then things will turn nasty.


Quote:
Originally Posted by tuxedocivic View Post
Mark is right. They're not woofers. And they're full range drivers bound to the same laws of physics as every other full range driver.
Mark is right in saying that they are full range drivers and you are right in saying that they are bound to the same laws of physics as everything else. But along come the T/S parameters as a way of usefully using the laws of physics to quantify how a driver behaves and what its limitations are.

Quote:
Originally Posted by tuxedocivic View Post
But I also agree with you that xmech is 4mm and xmax is 2mm based on what Mark has said.
This is where the problem lies. Marks drivers do have large Xmax figures. The motors are linear out to large excursions. If the Xmech happens to be 4mm, this doesn't reduce the Xmax parameter, it's still the same.

It is perfectly possible, using certain motor construction techniques, such as Adires XBL^2 technology, to make motors that have a linear excursion that is downright ridiculous, yet the rest of the driver would be destroyed if driven to these extremes. Here Xmech would be less then Xmax. Doesn't mean much except that your driver will remain linear right up until the point where it explodes, which is actually a good thing, unless of course you're the type of person who decides it's too loud when it starts to sound bad.

I don't think it's too much to ask for really, that Mark defines what the safe repeatable operating excursion capabilities of his drivers are. With that defined there would be no room for confusion on anyones part and it would greatly aid in helping people to design their boxes and it would also help significantly in deciding where and how to cross them to a sub or cross them to a bass driver in a low xover point/shallow slope three way.

I do not understand why this is in anyway unreasonable.

Quote:
I don't think the suggestion of Xmech does this.
It does do this. It quite simply states that you can drive the driver at the rated Xmech for extended periods of time without causing any damage to the driver. You can use it directly for calculating how loud you can actually play rock music.

Usually people design around the Xmax parameter and design knowing that 99% of the time they will never exceed it. However for the occasional peaks, or perhaps repeated peaks in rock music, Xmax is exceeded, but Xmech is not. There is a degradation of the sound quality when these peaks occur, but because Xmech isn't exceeded the drivers don't become damaged.

In the case of Marks drivers you could easily calculate the max level you can drive rock music too based off of an Xmech parameter. The grey area is actually when listening to something like classical music because of the larger dynamic range you do typically get much louder peaks even if they are few and far between. The peak will drive the loudspeaker beyond its Xmech, and how well it will survive this depends from driver to driver.

Damage in this case would be described by the materials, such as the cone or the surround, going, due to stress, into its plastic region such that it doesn't return to its original shape once the stress is removed. To this end even if you only listen to classical music and only very occasionally push the driver beyond its Xmech you will still damage the cone when doing so. It's just that it might take several hundred of them to cause any noticeable damage and with classical this might take a few years. Either way the Xmech parameter still describes the point where the driver will start to suffer permanent damage once you go beyond it, even if this damage only happens to be extremely minor as to be inconsequential with the right type of music.
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Old 8th November 2011, 03:45 AM   #20
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^ Sounds good to me :shrug:

I don't know much about this sort of thing. I just meant if Mark says we shouldn't use it past 4mm, then it's limited or maxed out its excursion at 4mm.

PS I see I was typing as you posted your last comment
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