Mark Audio CHR-70 gen1 self destruction. - Page 3 - diyAudio
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Old 8th November 2011, 02:53 AM   #21
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And I gotta say, it's sure great when a manufacturer jumps on a forum and talks about such things. Mark has sweat blood over these drivers and still comes on here and deals with this. Reminds me of when Kevin Haskins maelstrom drivers were popping. Always happens to the good guys.

Buying an MA driver is like buying a finely honed raced bike (see avatar picture), they're built to the limit. I like that. My bike revs to 17000rpm safely and makes 112 horsepower at the wheel from 600cc. With that comes a great responsibility that it's driven properly. If I rev it to 18000rpm, I'm going to receive 4 pistons into my anus as they blow out the top of the engine. Possibly like my bike, these drivers have little room for error. But within their limits the performance is hard to beat.
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Old 8th November 2011, 05:37 AM   #22
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Hi Tux,
Many thanks for your vote. its much welcomed. For me, being here on the forum is great, but I can also understand why other makers avoid forums as there's so many demands of all sorts.

I do have sympathy for those like member 5th who want absolute X max answers. But there aren't any absolutes, so pushing this notion has the potential to mislead many members who aren't completely sure about the specifics of driver operation. It increases my already bulging email in-box, where 80% of the info-help requests coming in are on other driver makes!!

I could possibly devise a specific isolation load test that takes drivers to their braking point. But what criteria do we use? Signal generation or music? If signal generation, what signal type and amplitude? If music, what music? Do we test in free air, or in box? If free air, what baffle size? If box, which box design? What loads do we apply? For how long? One continuous run or allow the driver to rest? If so, how long? What temp and humidity conditions should be applied? etc. etc etc................ Such a test might be applicable if all end-users universally agree to operate drivers to fixed load parameters, in one box type, using one type of amp at one fixed output in one size of room with a specific level of damping. A fixed test outcome will only be of practical use if the application is also fixed. So trying to calculate the safe fixed application of X isn't realistic, nor is it practically achievable. There are too many variables to make a test reliable for use in the field.

Few (if any) driver designers and makers publish a version of X Mech that specifically determines the breakdown of a driver under extreme load. Where a maker refers to X-Mech (or similar) its commonly a reference to the actual physical limit of travel of the driver's power train. Depending on the design of the power-train, typically X-Mech is around twice the length of X-max. But these physical dimensional differences can vary significantly.

I really like your bike comment. Its a good metaphor for many small(ish) and Full-Range driver makes, including mine. There are guys who push my drivers allot, more so than most other Full-Range makes so I'm confident CHR's and alike can do a decent job.

All the latest drivers main features have come about from members feedback on this forum. There's lots of posts on driver development, wish lists etc. The new Alpair 12 is gradually taking shape, so let me know by posting your desires: More SPL, dispersion and bandwidth V more power?:

next gen Alpair 12.3 diy community development

Cheers
Mark.
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Old 8th November 2011, 03:16 PM   #23
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Scanspeak and Seas consistently describe the Xmech parameter. You are correct in saying that lots of manufacturers don't, but one could argue that perhaps it isn't needed. I think most people assume that a driver can go a bit further then its rated Xmax without damage occurring. Say a +-5mm driver can easily hit +-7mm.

In the case of your drivers however it would seem like it could be somewhat necessary because the rated Xmax of the drivers don't accurately describe the physical limitations of the driver.

I think it would be rather simple to test your drivers to find out what a reasonable Xmech figure would be.

Take say a few Gen 2 Alpair 10.2s. Have them in free air or a box if you prefer, free air would be quieter though! Calculate the required RMS voltage drop required across the voice coil to provide +-1mm, +-2mm ....+-10mm etc of excursion.

Run one driver at +-1mm for 24 hours @ 40hz and see if there are any signs of damage. None? Get another driver and do the same but this time at 2mm. Keep going. If after a few days the 24 hour test @ 40hz shows signs of cone deformation at say +-5mm, then back off. Take a new driver and run it at +-4mm for 48 hours then check for damage, none? Run the same driver for another 24 hours and check again. Still no damage? Keep running the driver for say a week and if you like even go for two weeks, no damage? Then I'd say +-4mm would sound like a reasonable Xmech parameter.
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Old 8th November 2011, 04:03 PM   #24
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Quote:
Originally Posted by markaudio View Post
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.

Cheers
Mark.
Mark,

Full range drivers by B&C, Eminence, JBL and many others all can withstand continuous use at Xmax as long as power limits (Pmax) are not exceeded.
Very few professionals would accept a driver that could not withstand Xmax in regular use.

Your driver not being able to withstand regular peaks reaching Xmax without damage is the exception to the rule.

Cheers,
Art Welter
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Old 8th November 2011, 04:14 PM   #25
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Quote:
Originally Posted by tuxedocivic View Post
Buying an MA driver is like buying a finely honed raced bike (see avatar picture), they're built to the limit. I like that. My bike revs to 17000rpm safely and makes 112 horsepower at the wheel from 600cc. With that comes a great responsibility that it's driven properly. If I rev it to 18000rpm, I'm going to receive 4 pistons into my anus as they blow out the top of the engine. Possibly like my bike, these drivers have little room for error. But within their limits the performance is hard to beat.
Tux,

Like an engine, a speaker has displacement, the more displacement, the more output capability. Xmax, like redline, is a performance limit.
Xmax times cone area =displacement.
Engines can cheat a bit on displacement vs output, as they can be made to spin faster to extract more power cycles, while a speaker must only go at the speed of the frequency it reproduces.
Therefore, the axiom “there is no replacement for displacement” holds true for all loudspeakers.


“Redline” in a speaker is usually the equivalent of Xmech (or Xlim) which is normally quite a bit more than Xmax. Exceed Xmech and the speaker in most instances will be damaged, either instantly or over time.
Xmax, however, is by definition supposed to be within the linear range of operation for a loudspeaker. I am not familiar with all speakers of course, but speakers made by B&C, Eminence, and JBL all can withstand continuous use at Xmax as long as power limits (Pmax) are not exceeded.

Mark has recommended less than half the excursion of Xmax for safe operation on peaks, yet does not put that recommendation on the specification sheet.

Halving excursion is a reduction of approximately 6 dB, reducing power to 1/4.
Using your 112 HP, 17,000 RPM redline as an example, this is the equivalent of the bike manufacturer saying that though the engine is capable of 112 HP, only expect 28 Hp at 4250 RPM if you want the four pistons to remain in their cylinders for a full race.

I doubt you would find that acceptable.

Art Welter

Last edited by weltersys; 8th November 2011 at 04:17 PM.
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Old 8th November 2011, 04:30 PM   #26
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by weltersys View Post
Mark,

Full range drivers by B&C, Eminence, JBL and many others all can withstand continuous use at Xmax as long as power limits (Pmax) are not exceeded.
Very few professionals would accept a driver that could not withstand Xmax in regular use.

Your driver not being able to withstand regular peaks reaching Xmax without damage is the exception to the rule.

Cheers,
Art Welter
Art, et al - the debate about Xmax / Xmech or whatever new spec / testing regime is envisioned aside, might we be talking about different class of applications with your cited examples?

I doubt anyone would confuse Mark's 7, 10 or 12 cm thin metal cone drivers with the like of professional sound reinforcement / musical instrument devices, which are certainly built for the abuse to which they're guaranteed to be subjected.

5th:
the example of Adire XBL motors is well timed - I have experience with a couple of drivers ( CSS FR/WR125 and SDX7) with this tech. The motors can certainly exceed the suspension's control, with very distinctive results, and if not for the much more rugged cone materials - thicker paper on the FR/WR than Marks' EL & CHP70, and fibre mesh on the SDX7- I wouldn't be surprised if they suffered a similar fate when seriously over-driven - as it is they just fart and blat.
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Old 8th November 2011, 04:45 PM   #27
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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
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Old 8th November 2011, 04:53 PM   #28
ra7 is offline ra7  United States
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Quote:
Originally Posted by chrisb View Post
Art, et al - the debate about Xmax / Xmech or whatever new spec / testing regime is envisioned aside, might we be talking about different class of applications with your cited examples?

I doubt anyone would confuse Mark's 7, 10 or 12 cm thin metal cone drivers with the like of professional sound reinforcement / musical instrument devices, which are certainly built for the abuse to which they're guaranteed to be subjected.
The question is not whether they should be confused with the professional series of drivers or not. The question is why someone would state an Xmax of 8.5 mm when really the driver will self destruct at 4 mm.

Take the case of Fostex for example, a competing full range manufacturer. They clearly state their driver has an Xmax of 1 mm or 0.5 mm in some cases. Does this make their drivers look less attractive compared to the MA line? Yes, in some cases! But at least they do not market their drivers as being capable of an Xmax of 5 mm, coz the cone will be on the floor when that happens. Besides, these drivers will let you know that they are at their limits before self destructing. Thus it is easier to judge where the limit is. With the MA drivers it is the opposite. They operate linearly over a large portion of the Xmax and so, if they are going to fail or get damaged before reaching the stated Xmax, customers need to be warned. Not through forums, but through the legitimate method of clearly defining the T-S parameters. Something every other manufacturer, full range or otherwise, seems to know how to do.

By stating the Xmax as 8.5 mm is really misleading customers, the majority of whom will never ever visit this forum.

I'm glad some of the more knowledgeable members are stepping up to clear all this nonsense, and also that Mark is not going to get away with either deleting posts that differ from his own opinion or use deflectionary tactics such as asking members to contribute towards 'improving' his drivers.

Last edited by ra7; 8th November 2011 at 04:55 PM.
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Old 8th November 2011, 04:59 PM   #29
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Mixed feelings here. I only have experience with EL70 and I am consistently impressed with how well they handle what I push through them (everything from Nini Rosso to Rage Against the Machine), but I have no "real" frame of reference. Am I pushing them beyond xmax? I have no idea, but they always sound fantastic.

On the other hand, I just sort of intuitively know when to stop turning the volume dial. I have blown speakers in the past, and each time it was because I did something really stupid, something I instictively knew I shouldn't do.

So, it seems to me that if common sense prevails, then drivers just work. For a long time. If instead we look at a series of specs and then think "hmmm, let's see about that..." then we are on a slippery slope which ultimately leads to sad faces.

However, I do believe that a speaker should start sounding bad before permanent damage sets in. Those with weaker intuition would benefit from a truly audible indication that their lack of common sense may have negative consequences; a chance to turn the volume down, before the snap, crackle, pop. Does the EL70 provide this warning? Do other MA drivers? I don't know the answer...
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Old 8th November 2011, 05:05 PM   #30
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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
Is it really about the specs, though? Is someone going to get out a ruler or caliper and start turning the volume knob until they start hitting xmax or xmech, or whatever?

Surely the target audience of a refined full-range driver can be expected to have some common sense and restraint. No?
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