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Old 8th August 2011, 11:04 PM   #21
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This video is really stupid. Simply use a high pass filter and the the waste energy that does not produce an audible sound goes away, Itīs a party trick really.
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Old 8th August 2011, 11:21 PM   #22
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Quote:
Originally Posted by Joachim Gerhard View Post
This video is really stupid. Simply use a high pass filter and the the waste energy that does not produce an audible sound goes away, Itīs a party trick really.
Hi Joachim,
Yes, a high pass filter can help. Certainly could be useful on some simple BR and vented box designs, offering a quick fix solution.

Anyone who's done a high pass filter design, please feel free to post its details.

Thx
Mark.

Last edited by markaudio; 8th August 2011 at 11:23 PM.
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Old 9th August 2011, 12:09 AM   #23
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Thanks for your reply Mark. It is a 1st gen CHR70. I have put at least 50 or 60 hours of listening on them some at shall we say energetic levels but mostly at moderate levels after about 36 hours of low volume break in. What you saw is probably the most exercise that they have ever gotten and there was no audible evidence of distress (I don't like to abuse my equipment).

These will be used in a system that I am giving as a gift (teenager) so I want to be sure that I know the limits and make every effort to see that they are not easily exceeded. My sense was that as you say I was getting close to the limits on this driver. The video you saw did not have the HP filter in place but when I used it I did not see a gigantic reduction in cone motion so the filter may be tuned a little bit too low.

I was hoping to get usable output down to 40 Hz so that the system would be usable without a sub (though I am providing a sub output for it). It may be that I need to settle for 50Hz or use a larger driver. I had thought of putting in an integral sub but I don't think I will have room for it. It is intended to be portable and with all of those speakers and a SE KT88 amp and a plate amp... you see the dilemma.

One possibility is a 6" or so FR with a helper tweeter over 10k.

If I do end up using something else for this project these sweet little drivers will definitely find a home in another project. They are just too good not to use.

I plan on building another test box (TL this time) and see how that works out. Hornresp simulations seem to indicate that the driver would be much happier tuned to 50Hz so I will fiddle with that tuning as well.

BTW what is Xmech for the gen1 CHR70?
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Old 9th August 2011, 12:14 AM   #24
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Quote:
Originally Posted by markaudio View Post
Hi Joachim,
Yes, a high pass filter can help. Certainly could be useful on some simple BR and vented box designs, offering a quick fix solution.

Anyone who's done a high pass filter design, please feel free to post its details.

Thx
Mark.
I am just using a simple passive line level between the preamp and power amp. Right now I have 0.1uf-47k-.01uf-470k but it seems to be tuned a little low. BTW the 470K is the grid leak resistor of the power amp. In spice I simulated changing the first cap to 0.068uf and that looks like it should work much better.
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Old 9th August 2011, 01:35 AM   #25
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I think where the problem might lie with Mark drivers is their deceptive xmax figures.

Other drivers of the same size typically have around +-5mm xmax these days and then can go to anything like +-8mm before any kind of damage would occur. I've noticed that none of the Mark Audio drivers data-sheets contain a maximum safe excursion beyond the typical xmax figure.

No one is expecting a fostex with their <1mm of xmax to do any excursion party tricks, but because the Mark Audio drivers have a typical xmax figure and in some cases a rather impressive xmax, it could lead people into thinking that they will share a common maximum safe excursion of something considerably above the xmax figure.

From this thread it would appear that to prevent actual damage to the cone you'd probably recommend a maximum excursion as the xmax figure and no more. Maybe it would be a good idea to include a maximum excursion figure in the data sheet to prevent people from getting any crazy ideas. Usually one assumes that they can push their 5mm xmax driver to 8mm for peaks, this assumption would break a mark audio driver though.
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Old 9th August 2011, 01:43 AM   #26
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Think of Xmax as the "redline" then consider how often you do that to your car.
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Old 9th August 2011, 02:00 AM   #27
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Originally Posted by Cal Weldon View Post
Think of Xmax as the "redline" then consider how often you do that to your car.
Yes, except that in normal driver the xmax isn't the red line. The xmech is, and it tends to be 50%+ more then the rated xmax. This is why I suggested Mark defines what the maximum safe excursion of his drivers are as to prevent confusion and then possible damage.
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Old 9th August 2011, 02:05 AM   #28
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Not only with F-Ranger, but reaching Xmax is equally dangerous on Mids and Mids woofer too.

Me think the guy in the video is probably not a DIYer but bought a set from a DIY friend and trying to show off what his little speakers can do and crazy excursion. I think I kind of see his worried face near the end of the video though.
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Old 9th August 2011, 03:36 AM   #29
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Originally Posted by mashaffer View Post
Thanks for your reply Mark. It is a 1st gen CHR70. I have put at least 50 or 60 hours of listening on them some at shall we say energetic levels but mostly at moderate levels after about 36 hours of low volume break in. What you saw is probably the most exercise that they have ever gotten and there was no audible evidence of distress (I don't like to abuse my equipment).

These will be used in a system that I am giving as a gift (teenager) so I want to be sure that I know the limits and make every effort to see that they are not easily exceeded. My sense was that as you say I was getting close to the limits on this driver. The video you saw did not have the HP filter in place but when I used it I did not see a gigantic reduction in cone motion so the filter may be tuned a little bit too low.

I was hoping to get usable output down to 40 Hz so that the system would be usable without a sub (though I am providing a sub output for it). It may be that I need to settle for 50Hz or use a larger driver. I had thought of putting in an integral sub but I don't think I will have room for it. It is intended to be portable and with all of those speakers and a SE KT88 amp and a plate amp... you see the dilemma.

One possibility is a 6" or so FR with a helper tweeter over 10k.

If I do end up using something else for this project these sweet little drivers will definitely find a home in another project. They are just too good not to use.
I plan on building another test box (TL this time) and see how that works out. Hornresp simulations seem to indicate that the driver would be much happier tuned to 50Hz so I will fiddle with that tuning as well.

BTW what is Xmech for the gen1 CHR70?
Hi M,
Apologies, I miss-understood thinking the driver in your video was an Alpair. The Gen.1 CHR-70's also used the softer part hand-made cones so they need more care when being driven. I recommend you follow my previous advice and limit the LF output.

The Gen.2 and Gen.3 models use the Multiform cones which on these particular drivers are more robust. I purposely beefed up their cones and power-trains as they are becoming popular with younger Diyers. There are allot of posts from guys who've given CHR's more power and they've survived. But like most things mechanical, service life will decrease the more they're stressed.

I'd suggest work with the filter and try to work the box tuning at around the 52Hz level. Power handling should be better and the bass should have a bit of "punch" to it. A filter remains a very good option.

One other point I'd like to make, human hearing damage in younger people is on the increase. I'd urge some system design caution when building a system for a teenager. Persistent exposure to levels in the higher 80's dB and above will lead to hearing losses in middle and later age.

Cheers

Mark.
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Old 9th August 2011, 03:54 AM   #30
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Quote:
Originally Posted by 5th element View Post
I think where the problem might lie with Mark drivers is their deceptive xmax figures.

Other drivers of the same size typically have around +-5mm xmax these days and then can go to anything like +-8mm before any kind of damage would occur. I've noticed that none of the Mark Audio drivers data-sheets contain a maximum safe excursion beyond the typical xmax figure.

No one is expecting a fostex with their <1mm of xmax to do any excursion party tricks, but because the Mark Audio drivers have a typical xmax figure and in some cases a rather impressive xmax, it could lead people into thinking that they will share a common maximum safe excursion of something considerably above the xmax figure.

From this thread it would appear that to prevent actual damage to the cone you'd probably recommend a maximum excursion as the xmax figure and no more. Maybe it would be a good idea to include a maximum excursion figure in the data sheet to prevent people from getting any crazy ideas. Usually one assumes that they can push their 5mm xmax driver to 8mm for peaks, this assumption would break a mark audio driver though.
Hi 5th,
I'm not sure what you imply when using the "deceptive" word.

As an engineer, I've consistently quoted the driver's Mech. X which is in line with most published practice. I've also followed up with many posts on this issue over the last year or more.

I've mentioned many times about the need to not simply focus on X max. The power rating of the driver is a good indicator, also its moving mass and the fact that it is Full-Range, all indicators of an emitter for use on lower applications.

Mentioning a lower excursion has already been done. It created confusion for allot of Diyers.

Cal's post is most appropriate. For those who own cars, how many constantly drive them to the red-line limit? Only those who race cars, the others risk time in hospital and jail.

Mark.

Last edited by markaudio; 9th August 2011 at 04:08 AM.
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