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Old 9th August 2011, 02:58 AM   #31
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Quote:
Originally Posted by 5th element View Post
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.
Hi 5th,
Show me the specific industry agreed standard that says Mech X is 1/2 total X. This is news to me.

The problem is that there's no agreed industry standard for the exact operational specification(s) that directly relates to the use of excursion for the applied operation of audio drivers. There's lots of information giving suggestions but sadly nothing that's universally agreed.

The Alpairs use long coil windings as an integral part of the linear operational envelope. Using long coils aids in balancing the power train. Its also a constituent part of heat dissipation. Most experienced driver designers use some or most of these elements within their driver designs. Conversely, short coils have particular design limitations that relate to power-train design and usually will only be found on specific driver types. Such coils are mostly found on those drivers at the more extreme end of Full-range where efficiency is the main design criteria, sacrificing other elements of a drivers operation.

There's no point is pushing most ANY audio driver close to ANY of its limits. Distortion will likely result every-time when ANY driver (even a sub) is pushed close to its excursion limit.

So I recommend Diyers to look holistically when selecting drivers and box designs. I broadly agree with 5th's comment regarding using 1/2 X as a operational guide limit. For those who remember my many previous posts on this issue, I've said operating a driver on "shock loads" to 50% of X is likely about right. Note the words "shock loads". That means Non-Linear LF loads like the roll of drum. It doesn't mean constant LF loads, for example produced by heavy rhythmic beat music. If you're into this style of music and like to play loud, then likely Full-Rangers shouldn't be the first drivers of choice.

Thanks
Mark.

Mark.

Last edited by markaudio; 9th August 2011 at 03:48 AM.
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Old 9th August 2011, 03:13 AM   #32
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The damage in question here is edge deformation at high excursion, yes? In a sealed box would you say the power handling of the system increases significantly? Or is the driver vulnerable to other damage at enthusiastic volumes when the excursion is restrained by the box (not electrical filter)? I would expect so, but I may be incautious, and in a tightly designed system perhaps the vc power dissipation (or something else?) doesn't much exceed cone strength...

Last edited by AdamThorne; 9th August 2011 at 03:23 AM.
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Old 9th August 2011, 03:21 AM   #33
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Quote:
Originally Posted by markaudio View Post
Hi 5th,
snip:
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.
or one way visit to the morgue

testosterone and horsepower - (particularly 2-wheeled variety) - very dangerous mix
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Old 9th August 2011, 03:35 AM   #34
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testosterone and horsepower
One of my favourite combinations next to beer and power tools.
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Old 9th August 2011, 03:57 AM   #35
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Quote:
Originally Posted by AdamThorne View Post
The damage in question here is edge deformation at high excursion, yes? In a sealed box would you say the power handling of the system increases significantly? Or is the driver vulnerable to other damage at enthusiastic volumes when the excursion is restrained by the box (not electrical filter)? I would expect so, but I may be incautious, and in a tightly designed system perhaps the vc power dissipation (or something else?) doesn't much exceed cone strength...
Hi Adam,
Well observed and good point - many thanks for posting. Yes, you're broadly correct. Sealed boxes (depending on internal volumes) have a possible advantage of adding mechanical damping with their positive pressure acting on the rear of the cone. Such damping would help to reduce the stress load on the outer sections of the cone.

By what margin is hard to say as it would be best to experiment, but certainly there's potential for those Diyers who wish to make sealed systems to gain from this aspect of the box design.

Thanks
Mark.
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Old 9th August 2011, 04:02 AM   #36
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And amazingly Cal still has all his fingers...

dave
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Old 9th August 2011, 04:04 AM   #37
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Quote:
Originally Posted by chrisb View Post
or one way visit to the morgue

testosterone and horsepower - (particularly 2-wheeled variety) - very dangerous mix
Hi Chris,
Yummpy, but as I know to my cost; At the tender age of 20 years as a boy racer (Formula saloons - Ford Cossy), came adrift big-time at Knickerbrook corner:

http://en.wikipedia.org/wiki/Oulton_Park

Ooooouuch.....spent some time in hospital. wouldn't mind but was in 3rd place at the time!

Cheers
Mark.
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Old 9th August 2011, 09:03 PM   #38
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Another option I am looking at is sticking with the CHR70s as I really like them and adding a 6 or 6.5" helper woofer something like the Dayton Classic...

http://www.parts-express.com/pdf/295-308s.pdf

A quick sim in BoxPlot indicates that a 0.5 ft^3 ported enclosure (same size I am now using) will get down to the desired 40Hz. Xmax is slightly greater than the CHR70 and the surface area is substantially larger. I could use a passive crossover at around 100 Hz or a bit below which should give the FR enough margin and still allow for youthful indiscretion. Would probably still use line level HP at around 40 and provide subwoofer line level output for those times when full spectrum results are desired.
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Old 10th August 2011, 12:06 AM   #39
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Hi 5th,
I've deleted your last post as it mostly repeats points raised in your previous posts. Please condense your reply posts as my time to support all Diyer's posts is limited.

The primary objective of this thread is to alert and show Diyers examples of high risk operations on Full-range drivers (videos) and similar info.

More worrying, you made some assertions in the post I've deleted, referring to safe operation at X mech that were operationally misleading, especially to those less experienced Diyers. I'm reluctant to delete members posts but in some cases, do so if the information in a post risks creating operational problems for other member should they follow it.

I value your input and ideas on the Markaudio section of Diyaudio but I also want to see some respect for my extensive driver design and build knowledge.

If Diyers wish, we could open up a thread on specifically on the properties of excursion in relation to the operation of Full-range drivers. I'll do my best to support it but please appreciate that I'm only 1 guy so I don't have limitless time.

Thanks

Mark.

Last edited by markaudio; 10th August 2011 at 12:44 AM.
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Old 10th August 2011, 12:13 AM   #40
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Quote:
Originally Posted by mashaffer View Post
Another option I am looking at is sticking with the CHR70s as I really like them and adding a 6 or 6.5" helper woofer something like the Dayton Classic...

http://www.parts-express.com/pdf/295-308s.pdf

A quick sim in BoxPlot indicates that a 0.5 ft^3 ported enclosure (same size I am now using) will get down to the desired 40Hz. Xmax is slightly greater than the CHR70 and the surface area is substantially larger. I could use a passive crossover at around 100 Hz or a bit below which should give the FR enough margin and still allow for youthful indiscretion. Would probably still use line level HP at around 40 and provide subwoofer line level output for those times when full spectrum results are desired.
Hi M,
Given the project is for a Teenager and you've got Gen. 1 CHR's, you're heading in a good direction by adding the Dayton. Possibly experiment will the XO as I'm not sure what the Dayton sounds like, but 100Hz should be a good point to start.

I guess much depends on said Teenager's musical tastes. But chances are the Teen will up the volume at some point.

Cheers
Mark.

Last edited by markaudio; 10th August 2011 at 12:35 AM.
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