Mark Audio CHR-70 gen1 self destruction.

[Bill poster]

I'd never heard of Xmech, so the thread is an interesting read. It would be at the least 'honest' for all manufacturers to supply some kind of guideline.

[natural sound]

Originally Posted by markaudio

Hi 5th, Guys,

5th, appreciate you first comment in you last post; And your contributions. They are interesting but you've made many assertions that are incorrect. You need more knowledge on driver design and construction to avoid some of traps. Your thinking is far too geared towards constant inputs when drivers load are primarily non-linear for bulk of musical reproduction.

You've made allot of inferences, some of which are below the belt, without foundation. This one in particular, quoted from you last post: "I bet that almost all of them can be used at their rated xmax without damage occurring." Its potentially mis-leading to other members. I hope other members will note my item 2 reply below.

But I like it when guys try. I'm on record for actively encouraging Diyers to do what I've done; Become driver designers and makers. We collectively shouldn't leave it all to the big maker boys.

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Guys,
I'll have to make this my last post, cos this thread's eaten so much time that I need for all the other jobs currently on my "to do" list. So all I can do summarise the current situation as best I can:

1 - I appreciate that my designs don't direct fit into a typical Full-Range configurations i.e they have a linear long throw coupled with low mass, requiring more operational care than some other Full-Rangers. I've never made any secret of this, I've done allot to highlight this situation.

2 - This bit's important:
For most makes of Full-Range drivers, they won't sustain operational integrity when run at X-max for long peroids. For the 2 years, I've been working guys (Matsubara san, Father designer of the FE series), Taniguchi san, past lead designer for JBL, Sony et.al and Kitagowa San, chief quality control Manager Foster Corp. Together they've got a 100+ years of driver design/build experience between them. We collectively know that that the bulk of light load wide-band-Full-Range drivers won't operate safely if driven very close to, or at their quoted X-max on constant/heavier regular loads. You can decide if me and my colleagues have the greater driver knowledge and operational experience, or member 5th, on this particular issue.

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Trying to use X-mech as some sort of standard is a long way off. The bulk of the industry doesn't apply this type of measure for the purposes of safe limit operation. There are too many operational variables influencing the driver to make reliable data.

For the bulk of applications (despite 5th's continuous assertions), Markaudio drivers work fine. I don't have ten's or hundred's of guys beating on my door with broken drivers in their hands. Please see my previous recent posts. From BR's, vented, MLTL's, Damped Air Coupled to Horns, Sealed etc, etc., there's lots of Markaudio drivers in these box types doing their work.

I do accept that better illustrating the operational description of X is proving challenging. I've stuck with this thread in the hope that some progress and agreement would be made, or a bright new idea will emerge. This issue has been knocking around in the forum for the past year.

Cheers
Mark.

Hello Mark .

I first off would like to say after being a diyer between 10 to 13 years I can't remeber how long now? Also being in home hi-fi for 27 years now. Mark your drivers are one of the best I have come across. I had a pair of the Alpsir 6 p's and I broke them in from 0 hours to 130 hours. They were one of the easiest most enjoyable drivers I have ever worked with following the break in guide lines. I sold them to a friend who wanted to try a pair of your drivers. The alpair 6-p's don't have the peakness that the fostex Fe line of drivers have. I will say I am a paper man. I have yet to listen to a pair of any kinda metal type drivers to win me over. (Sorry Mark trying not to punch below the belt on your metal drivers?) Now about the xmax I agree with what 5th element is saying and I also agree with Mark about you can only do so much with a fullrange driver and its not a woofer. If the x-max is a problem then cross them over at 500 hz and use a 8 inch woofer from 600 hz on down to solve the problem. Like a Visaton Stella light kida deal. I wish there was a fullranger to do it all but, there is not. It would be called the holy grail speaker. I just buy and enjoy and if it doesn't work out I sell it and move on. Again I am on both partys sides. Also I let mark do what he does best design and building speakers. As for 5th element your a very smart man as I see and read in your post. Again sorry about your drivers. Its a bummer when these things happen. JD

[weltersys]

Originally Posted by Bill poster

I'd never heard of Xmech, so the thread is an interesting read. It would be at the least 'honest' for all manufacturers to supply some kind of guideline.

And I had never heard of a driver with an Xmech only half of Xmax, or a manufacturer that would refuse to even mention that in the specifications before this thread .

[Bill poster]

Personally think the MA drivers are v good, the sign of good design is when you push the envelope. possibly the issue here is whether a volume product can co exist with being an artisan product

[Bob Brines]

I'm not so sure that Mark "refused" to state that Xmax is smaller than Xmech. I think it is probably more likely that it didn't occur to him that customers would try to get so much SPL out of so small a driver.

The problem stems for the fact that the MA driver do not have progressive suspensions. They can be driven to destruction without complaining. Most drivers have progressive suspensions and are difficult in varying degrees to drive to Xmech without burning out the voice coils.

I guess my question is what do you expect out of a 3" driver?

Bob

[planet10]

Originally Posted by Bob Brines

The problem stems for the fact that the MA driver do not have progressive suspensions.

At least some of the the XBL drivers are similar.... they are quite linear right up till you smack the voice coil against the backplate -- with a very disturbing sound.

You will start to see MA drivers with the suffix A. These drivers have an arrestor built in. Instead of compromising the suspension, Mark has added a function specific design element.

dave

[weltersys]

Originally Posted by Bob Brines

I'm not so sure that Mark "refused" to state that Xmax is smaller than Xmech. I think it is probably more likely that it didn't occur to him that customers would try to get so much SPL out of so small a driver.

I guess my question is what do you expect out of a 3" driver?

Bob,

I would expect a 3" driver to operate reasonably well up to Xmax, with commensurate SPL.

Mark has stated in this thread, but refused to mention in his specifications, that operation of this driver at just half of Xmax can lead to stress cracks.

Knowing this, I'd have to expect 6 dB less from the driver than drivers with similar Xmax ratings.

If I didn't know this, I would not expect stress cracks at what I would have thought was within normal operation range, and would be quite distressed when they occurred, just as those participating in this thread were.

Art

[Scottmoose]

Ye gods, I wouldn't.

You would need to have the mechanical sympathy of Captain Caveman to continually hammer a 4in wideband driver (any) at ~1/2in deflections. A little common sense is in order. Whatever the stated Xmax might be, a widebander is not going to sound particularly good at such deflections for a myriad of both mechanical & acoustical reasons. The argument is akin to stating that your car should be able to run at its stated maximum speed all the time / for extended periods.

On the subject of Xmax, I've made this point elsewhere, but it's worth making a reminder here: it's a nebulous figure since there are multiple different ways of giving a figure for it. Most of these give different values for the same drive unit, manufacturers almost never state which method they used so there's no consistency there either, and while it might appear heresy, the fact is that none of them are particularly informative, or account for everything that is going on. At best, Xmax is a very general 1st order guideline, no more. It is not some hard & fast quantity, or a statement that a driver can be run continually to large excursions (assuming the Xmax figure is high). That is not what it's for, and it's certainly not what it does.

Here are three of the more common methods for producing an Xmax figure:
-Magnetic gap height minus height of VC winding
-As above, take absolute value & /2
-Set it at whatever point the driver reaches 10% THD.

The first and second do not provide give any distortion values whatsoever, while the latter simply states a point at which the driver reaches 10% THD, telling you nothing about distortion types, nor any information about the behaviour to either side of that point. The driver could be at 9.99999% THD for most of the supposedly linear region for all we know on that basis, nor do we know how rapidly distortion rises beyond it, or as previously mentioned, the character of said distortion. The plain fact is, you need to measure the drivers for yourself if a full set of distortion figures are not provided (as is usually the case) if you want to actually know what the driver is doing. And then you need to think for yourself about how much mechanical stress you are placing on the unit, which even these, let alone Xmax, do not tell you.