Mark Audio CHR-70 gen1 self destruction. - Page 4 - diyAudio
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Old 8th November 2011, 05:06 PM   #31
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Quote:
Originally Posted by tuxedocivic View Post
Hi Art,

Like my previous posts indicated, I totally agree. These drivers are finely honed, delicate devices. I agree that the manufacturer should clear about their limits. If redline is 4mm, every buyer should know, not just the buyers on this forum.

I don't even care if mark calls is xmax or xlim or what ever. Even just a note next to power handling would clear things up, and probably save him face, and sales
Exactly right, though Xmax and Xlim do have specific definitions.
The extremely thin metal has advantages and disadvantages over other materials that should be explained in the PDF, otherwise fatigue cracks are inevitable under what one would assume to be a safe operating range.

Incredible sonic detail and all that wonderful stuff is great, but so is knowing how loud a driver can go before it will break .
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Old 8th November 2011, 05:20 PM   #32
rjb is offline rjb  New Zealand
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Can we simplify things, and not get confused.

1) All cones bend, and therefore fatigue, metal quicker than paper.

2) Time to fatigue failure depends on both the excursion, (ie degree of bending) and frequency of excursion.

3) Xmax specifies only one of these, the allowable excursion.

4) Xmech does not specify allowable frequency of excursion, so another parameter is required.

5) Perhaps one possible answer is to rate the power for "continuous", ie sinewave) and "burst", but that then requires explanation that heavy metal is closer to "sinewave" than classical is. Still not perfect.
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Old 8th November 2011, 05:21 PM   #33
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Originally Posted by markaudio View Post
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.
Thanks Mark,

That figure seems more in line, and it is also a good illustration of the inherent vulnerability of full range drivers: they need light weight cones to work, whatever the material of choice. Paper will buckle as well if driven too hard.

After having read this thread, I feel a need to repeat my 'horses for courses' remark.

If in need of disco bass, use a subwoofer and a high pass on the FR.

vac
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Old 9th November 2011, 01:03 AM   #34
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Originally Posted by ra7 View Post
The question is why someone would state an Xmax of 8.5 mm when really the driver will self destruct at 4 mm.
Because, by using the standard of rating an underhung motors linear excursion, the drivers do presumably have 8.5mm of one way Xmax.

If they will eventually self destruct when driven to 8.5mm one way is besides the point, the Xmax figure is still accurate. This is where Xmech comes in and defines the maximum safe excursion that the driver can repeatedly withstand without failure.

Usually Xmax<Xmech and problems aren't typically encountered.

With Marks drivers, he has chosen to keep the motor linear beyond the maximum excursion that the driver can repeatedly withstand. This is actually a very good idea. Mark has designed the drivers such that if they are occasionally over driven they will survive, but they will also still sound good when over driven. This means that for the odd classical crescendo you will be able to experience the full effect without losing out on sound quality.

With a fair few drivers Xmech = how far the driver can go before the coil slams into the backplate. And depending on the driver and how hard you slam it, this can be a trick that it will only ever get to do the once. Obey Xmech or kaboom. Slamming the voice coil into the back plate also sounds utterly horrible, it's loud and quite alarming. If you hit the back plate you literally run for volume control.

In Marks case driving beyond what would be a nominal Xmech parameter wont cause a catastrophic failure, more if you keep doing it the cone will end up deforming.

The trouble is that Mark doesn't define what the safe maximum excursion that the drivers can repeatedly withstand (Xmech) is and considering it is less then Xmax it causes confusion and, as is obvious, people end up with damaged drivers. Now it could very well be that the vast majority of those who've damaged his drivers would have ended up damaging any driver. Even so, providing an Xmech figure would give everyone something solid to work with and would presumably only help Mark out because he'd be able to say to anyone in the future who damages a driver - Xmech is clearly defined in the datasheets, if you go beyond it you've only got yourself to blame.
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Old 9th November 2011, 02:16 AM   #35
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Originally Posted by 5th element View Post
Now it could very well be that the vast majority of those who've damaged his drivers would have ended up damaging any driver.
The "Spinal Tap " it goes to 11 types !!!
Quote:
Originally Posted by 5th element View Post
Even so, providing an Xmech figure would give everyone something solid to work with and would presumably only help Mark out because he'd be able to say to anyone in the future who damages a driver - Xmech is clearly defined in the datasheets, if you go beyond it you've only got yourself to blame.
Most aren't that knowledgable..... ; ( I'm not a professional speaker design engineer; But I play one on TV !) I have real doubts wheter a spec like that is going to be appreciated and totally understood bt the novice.

I have a sneaaaaaaking suspicion that the number of MA drivers going to the big tranducer pile in the sky would be Identical even if mark were to make his spec sheets just to your liking !!!!
.

Last edited by flatfinger; 9th November 2011 at 02:20 AM.
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Old 9th November 2011, 05:43 AM   #36
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Hi Guys,

Out of interest, I thought you might like to see a pic of the rupture testing that we do on the Multiform cone press passes (see pic). We use these test pressings to measure the tensile strength and flex ratio at each press pass.

5th's last post (No. 34) is correct re my design work (possibly a fellow driver designer/maker in the making?). The is precisely the point about this aspect of my design work, that you can use the larger excursion with linear results, on non-regualar LF loads. 5th, description of my work is better than mine. Unfortunately my partial dyslexia hinders me. Apologies to members who find my texts full of typos and a bit complex. I have to think in "word pictures", visualising engineering drawings and components, associating them with a memorised word(s) as I type. While not 100% ideal, its a method that was taught to help me manage this disability but it takes allot of time.

A few months back, I did try using X- figures as a guide for running in and general operation of a driver. I got a hail of emails and posts on exactly how do diyers go about actual measuring the physical excursion while the driver's operating. It became a nightmare so that idea sort of got scrapped.

X-Mech is a measurement of the safe regular operation for a driver?. No driver maker that I know specifically quotes an Mech measurement for the "expressed" purpose to quote a safe regular excursion load. Commonly, X-Mech (or similar) is stated as the total mechanical stroke available from the driver's power-train. So until the industry agrees a comprehensive set of standards, all I can do is to advise on regular basis on this forum. Back in June-July, I put an advice note on all Markaudio PDF's that can be downloaded from the Markaudio site. I also started the Markaudio Aren't Woofers, thread so unlike most other makers, I am trying to help.

One thing Matsubara san and me working on is more advanced rear suspensions (spiders). We are now starting to use a spider with spines. We've done allot of work to control the resistivity at the outer excursive limits. Currently, all the latest batches of Alpair 10. Gen's 2's are fitted with this up-grade (see pic). The latest design of this suspension type has additional stroke resistance from 7.2-mm onwards, but that doesn't mean its "open season" to use the Alps with this upgrade as woofs!

I'll have to think some more on how to provide data or advice that is practical to use, meaningful to the majority of end-users. Just coming up with X-Mech, X-Max, X-Zing, X-Ping, X-Thingy........whatever we call it won't hep the typical Diyer trying to figure the next project. This measurement issue has been around the block so many times already.

Cheers
Mark
Attached Images
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Old 9th November 2011, 06:56 AM   #37
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To be honest, I don't know how much more forewarning Mark can give about proper use of these drivers. I feel like every document and official post about his drivers include *lengthy* and *repeated* recommendations for proper use and tolerances. Now I get paranoid at the mere sight of the words 'low volume levels'.

There are people who are going to hook MA drivers up and start cranking them at the get go, or who will shrug at the fine print or think they know enough about their system to do as they see fit. It's not like there's been a record of consistent driver failure (cause if there were boy would we know about it on this forum).

This just feels like typical internet forum weather pattern with low pressure system heading Mark's way. I say ride it out.
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Old 9th November 2011, 10:32 AM   #38
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Originally Posted by wushuliu View Post
To be honest, I don't know how much more forewarning Mark can give about proper use of these drivers. I feel like every document and official post about his drivers include *lengthy* and *repeated* recommendations for proper use and tolerances. Now I get paranoid at the mere sight of the words 'low volume levels'.

There are people who are going to hook MA drivers up and start cranking them at the get go, or who will shrug at the fine print or think they know enough about their system to do as they see fit. It's not like there's been a record of consistent driver failure (cause if there were boy would we know about it on this forum).

This just feels like typical internet forum weather pattern with low pressure system heading Mark's way. I say ride it out.
Agreed. Quote from the documentation freely available to all:
Quote:
Small to medium sized speakers are usually lower power designs. The power rating is given in the technical data
for each audio driver. For a reliable long service life, please operate your new speakers with care. For the first 100
hours, operate them at very low volumes. After this period, gradually increase the volume to a normal listening
level. If you see the cone of the speakers making large movements, immediately turn the volume down. This will
protect the speaker and your human hearing from damage. Factory mechanical defects for a period of 1 year.
Excessive hard use (over-driving) and other damage caused during customer use is excluded from our warranty.
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Old 9th November 2011, 02:34 PM   #39
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Xmech on wikipedia is quoted as being...

Quote:
Xmech - Maximum physical excursion of the driver before physical damage.
I figured that this would have been lifted directly from the original T/S definitions when they were laid out. This could be considered a bit of a grey area too it seems, but regardless of that, you know that if you try going beyond it that you do so at your own risk.

I can easily see that providing details as to what Xmax to hit whilst running in at X frequency could create a whole plethora of problems. Some people wanting to know what this actually means, or wanting to know how to accurately determine it. I can however see one way around it, but then again this assumes the DIYer has access to a multimeter and a signal generator. As a PC/laptop will function as a signal generator everyone should have one of those and if the person building a DIY speaker doesn't have a multimeter then now would be a very good time for them to go and get one!

Basically you could have a run in method listed in the data sheets and it'd be very simple. You'd say something like, leave the drivers out of a box and...

1) Play a 100hz signal through the driver at a drive level of 1 volts rms for 1 day.
2) Play a 40hz signal through the driver at a drive level of 1 volts rms for 1 day.
3) Play a 40hz signal through the driver at a drive level of 2 volts rms for 1 day.

Something like that perhaps. Anyone should be capable of doing that and if they are not then they should learn how to do it. Break-in/Run-in seems like an important part of the proper way to use your drivers as it allows the more delicate of the moving parts to gradually soften up. I would say that if run-in is quite important and necessary for the best performance, that if someone doesn't know how to do something as outlined above, that they should learn out how to do it.

You could maybe also include at the end of the run-in guide.

point x) Now drive the driver at 40hz but increase the drive level up to 3.5vrms. Look at the cone and pay attention to how much it is moving. Make sure that you never exceed this amount of movement on a regular listening basis.

You can't really get much simpler/easier then that as a way of trying to quantify run-in and as giving people a visual guide as to how much they can expect their Mark Audio driver to give.
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Old 9th November 2011, 03:30 PM   #40
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Quote:
Originally Posted by 5th element View Post
Xmech on wikipedia is quoted as being...

"Xmech - Maximum physical excursion of the driver before physical damage."

I figured that this would have been lifted directly from the original T/S definitions when they were laid out. This could be considered a bit of a grey area too it seems, but regardless of that, you know that if you try going beyond it that you do so at your own risk.

I can easily see that providing details as to what Xmax to hit whilst running in at X frequency could create a whole plethora of problems. Some people wanting to know what this actually means, or wanting to know how to accurately determine it. I can however see one way around it, but then again this assumes the DIYer has access to a multimeter and a signal generator. As a PC/laptop will function as a signal generator everyone should have one of those and if the person building a DIY speaker doesn't have a multimeter then now would be a very good time for them to go and get one!

Basically you could have a run in method listed in the data sheets and it'd be very simple. You'd say something like, leave the drivers out of a box and...

1) Play a 100hz signal through the driver at a drive level of 1 volts rms for 1 day.
2) Play a 40hz signal through the driver at a drive level of 1 volts rms for 1 day.
3) Play a 40hz signal through the driver at a drive level of 2 volts rms for 1 day.

Something like that perhaps. Anyone should be capable of doing that and if they are not then they should learn how to do it. Break-in/Run-in seems like an important part of the proper way to use your drivers as it allows the more delicate of the moving parts to gradually soften up. I would say that if run-in is quite important and necessary for the best performance, that if someone doesn't know how to do something as outlined above, that they should learn out how to do it.

You could maybe also include at the end of the run-in guide.

point x) Now drive the driver at 40hz but increase the drive level up to 3.5vrms. Look at the cone and pay attention to how much it is moving. Make sure that you never exceed this amount of movement on a regular listening basis.

You can't really get much simpler/easier then that as a way of trying to quantify run-in and as giving people a visual guide as to how much they can expect their Mark Audio driver to give.
Hi 5th, Guys,
I wondered when someone would quote Wiki. There's no original reference to this particular measurement and as said, the vast majority (if not all) driver makers aren't using this measurement is the way Wiki describes. I like Wiki allot but they aint the folks making drivers.

(Sorry 5th, I know you mean well but......)
Re 5th's running in 1,2,3 method, Please DON'T follow this pattern. Its most important to use a variable load (music) during the running in period. Regular/fixed inputs won't properly load stress the driver's power-train.

For 5th' general idea, its interesting to seek the opinions of the members for this measurement methodology.

Cheers
Mark.

Last edited by markaudio; 9th November 2011 at 03:40 PM.
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