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Old 13th December 2011, 12:25 PM   #1
JohnR is offline JohnR  Australia
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Default Purpose of plastic cover rings?

Hi, what is the purpose of the plastic cover rings, and is there any specific reason for when they should or should not be used? Thanks
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Old 13th December 2011, 06:15 PM   #2
Swifty is offline Swifty  Netherlands
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Use them if you can get away with it regarding baffle thickness/width. They add stiffness to the chassis. If your baffle is too thin or too narrow to accomodate them, leave them off.
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Old 13th December 2011, 06:35 PM   #3
chrisb is offline chrisb  Canada
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Frankly I think you can get away without them on the 7s - these are not massive drivers - but if optional on the new Alpair 12s, I probably would use them.


I just finished a pair of Ripole boxes for JBL 2225H woofers and big BLH for SEAS L26ROY - neither the most humongous drivers extant, but considering their over 25lbs each and operating bandwidth and motor power, thicker baffles and magnet support bracing doesn't hurt.

John - did you decide on an enclosure yet?
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Old 13th December 2011, 07:03 PM   #4
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If possible, we use them without.

dave
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Old 13th December 2011, 08:33 PM   #5
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I'm with Dave. I wish that Mark would dust bin the cover rings. Not needed and makes an oversize frame even larger than it needs to be.

Jim
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Old 13th December 2011, 09:02 PM   #6
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Hi John,
Please use the front cover where practical. It adds rigidity and damping. The power-train alignment on the Alpair's is critical (especially Alp7), maximising frame rigidity is 100% desirable. The rear magnet cover is less critical, the SPL gain with the cover is a lick under 1dB across the range. For those making small boxes, the option to remove this cover is available. However, the Alp7 is a high-performer, so I recommend retaining this cover where pratical.

At the request of several members on the forum, the covers are supplied loose to support their particular box design concepts.

Thanks
Mark

Last edited by markaudio; 13th December 2011 at 09:22 PM.
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Old 13th December 2011, 09:11 PM   #7
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Quote:
Originally Posted by Jim Griffin View Post
I'm with Dave. I wish that Mark would dust bin the cover rings. Not needed and makes an oversize frame even larger than it needs to be.

Jim
Hi Jim,
You've surprised me. I thought you would appreciate the engineering effort thats been applied to optimise the driver design/performance. I don't design Any feature of a driver without purpose.

Mark.
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Old 14th December 2011, 03:07 AM   #8
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Mark,

I appreciate the engineering effort that you placed in the design of the MA drivers. But in my opinion if you properly mount a driver on the baffle, then you should not have an issue with MA drivers used either with or without the mounting ring.

I love the performance of your drivers and highly recommend them to other DIY'ers. I also am grateful for your efforts to work with fellow DIY'er around the world to perfect full range drivers. I also appreciate the close match of the performance parameters of MA drivers within each manufacturing lot which are the result of your close involvement within the production shop so that product quality control is enhanced.

Compared to other drivers, MA units are appreciably over engineered which is a good feature. For example, some users report breakage of cast metal flanges in right angle corners of some other manufacturers' drivers--think of the one that starts with a J....--which are completely eliminated with the massive composite flange material used by MA.

The Alpair 10 and 12 models have 6 mounting screws vs. the usual 4 for comparable units from other manufacturers. Thus for the larger MA drivers the mounting load is better distributed around the flange vs. other drivers.

Some issues I have with the mounting rings are:

1. In some parts of the world MA suppliers carry units with the mounting rings attached. While in other parts of the world drivers and mounting rings come separate so the user can choose to use the ring or not. Thus some users have the choice to use or not use the rings while other users have to deal with units with the rings attached.

2. The earlier MA drivers did not have mounting rings. If you want to use a current generation driver with a mounting ring in an older enclosure, you would have to reroute the rebate cutout of the box.

3. Drivers with the mounting ring are more difficult to flush mount on the baffle which raises the possibility of additional edge diffraction around the cutout.

4. Also the baffle rebate is deeper with a mounting ring driver so the stiffness and damping integrity of the driver/baffle is diminished vs. a ringless driver/baffle combination.

5. The MA drivers with or without the mounting ring are significantly larger in diameter than comparable drivers from other manufacturers. The mounting ring just makes the discrepancy more acute which especially impacts the enclosure size for some designs.

That summarizes my issues with mounting rings. I would rather work with drivers that don't have an attached mounting ring.

I suspect that I'm not the only user out there who isn't in love with the mounting rings.

Just keep making great drivers and those of us who use them will continue to be happy.

Jim

Last edited by Jim Griffin; 14th December 2011 at 03:09 AM. Reason: correction
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Old 14th December 2011, 06:00 AM   #9
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Quote:
Originally Posted by Jim Griffin View Post
Mark,

I appreciate the engineering effort that you placed in the design of the MA drivers. But in my opinion if you properly mount a driver on the baffle, then you should not have an issue with MA drivers used either with or without the mounting ring.

I love the performance of your drivers and highly recommend them to other DIY'ers. I also am grateful for your efforts to work with fellow DIY'er around the world to perfect full range drivers. I also appreciate the close match of the performance parameters of MA drivers within each manufacturing lot which are the result of your close involvement within the production shop so that product quality control is enhanced.

Compared to other drivers, MA units are appreciably over engineered which is a good feature. For example, some users report breakage of cast metal flanges in right angle corners of some other manufacturers' drivers--think of the one that starts with a J....--which are completely eliminated with the massive composite flange material used by MA.

The Alpair 10 and 12 models have 6 mounting screws vs. the usual 4 for comparable units from other manufacturers. Thus for the larger MA drivers the mounting load is better distributed around the flange vs. other drivers.

Some issues I have with the mounting rings are:

1. In some parts of the world MA suppliers carry units with the mounting rings attached. While in other parts of the world drivers and mounting rings come separate so the user can choose to use the ring or not. Thus some users have the choice to use or not use the rings while other users have to deal with units with the rings attached.

2. The earlier MA drivers did not have mounting rings. If you want to use a current generation driver with a mounting ring in an older enclosure, you would have to reroute the rebate cutout of the box.

3. Drivers with the mounting ring are more difficult to flush mount on the baffle which raises the possibility of additional edge diffraction around the cutout.

4. Also the baffle rebate is deeper with a mounting ring driver so the stiffness and damping integrity of the driver/baffle is diminished vs. a ringless driver/baffle combination.

5. The MA drivers with or without the mounting ring are significantly larger in diameter than comparable drivers from other manufacturers. The mounting ring just makes the discrepancy more acute which especially impacts the enclosure size for some designs.

That summarizes my issues with mounting rings. I would rather work with drivers that don't have an attached mounting ring.

I suspect that I'm not the only user out there who isn't in love with the mounting rings.

Just keep making great drivers and those of us who use them will continue to be happy.

Jim
Hello Jim,
Many thanks for your support and comments. They raise some very interesting engineering and installation design issues. Before I go through them (I'll follow your numbering), your observations regarding the "engineered" philosophy of Markaudio drivers are timely. Being a Mech. Eng., I try to "engineer" the design/solution. Applied engineering was implanted into my DNA from 2 years old upwards. I'm a third generation engineer (father was x Jaguar - BMC - British Motor Corp.), grand farther was in boiler and steel making.

Like all things, engineered components and products can go along way to providing good performance and service but they will never achieve 100% perfection. There will always be some degree of compromise between a driver and the associated box design and installation. The Alpair model range is more aimed at the experienced system maker and full-range connoisseur, while to CHR/P/BW's are aimed for the wider market, beginners and those who like simpler box design work.

Alpairs, by their design, push box designing and making up a gear. The most significant example was the development of the Pensil box series, Scott's effort, originally to match the Gen. 1 Alpair 12 gave birth of a whole new set of box types. They are quite popular, giving pleasure the many home builders.

Working through your points in their order:

1. In some parts of the world MA suppliers carry units with the mounting rings attached. While in other parts of the world drivers and mounting rings come separate so the user can choose to use the ring or not. Thus some users have the choice to use or not use the rings while other users have to deal with units with the rings attached.

2. The earlier MA drivers did not have mounting rings. If you want to use a current generation driver with a mounting ring in an older enclosure, you would have to reroute the rebate cutout of the box.

I'm with you on these 2 points. I don't always get the choice to supply loose covers as some dealers don't want to handle component(s) product. I'm working hard to encourage dealers to accept all Markaudio production rather than "cherry pick". Some dealers aren't comfortable with end-users (Diyaudio members) having direct connection with me. Its a debate about the freedom of end-user choice while for the dealers, they worry about warranty issues to do with possible in-correct application of covers and similar support items. Its part of the reason for the change in the European distribution arrangements.

3. Drivers with the mounting ring are more difficult to flush mount on the baffle which raises the possibility of additional edge diffraction around the cutout.

I haven't (as yet) seen any evidence on diffraction, but accept that where a very narrow baffle design is deployed, care and skill will be needed to attain a flush mount to minimise any effect.

4. Also the baffle rebate is deeper with a mounting ring driver so the stiffness and damping integrity of the driver/baffle is diminished vs. a ringless driver/baffle combination.

5. The MA drivers with or without the mounting ring are significantly larger in diameter than comparable drivers from other manufacturers. The mounting ring just makes the discrepancy more acute which especially impacts the enclosure size for some designs.

I appreciate these points, hence my recommendations remain consistent; Use the cover where: A - Where woodworking skills are sufficient to make adequate support for the driver within the recess, B - keep side wall elevation behind the frame mount to a minimum to mitigate wave reflection onto the rear of the cone. The judgment call is with the end-user on the use of the covers. We've been using covers on Apair 7 and Alpair 10 on 18-mm and 20-mm thick baffles, cutting recesses on Ply, MDF and solid woods with no structural problems on a variety of box designs.

Markaudio driver profiles, particularly the frame O/D's are significantly larger for the given cone diameter when compared to other makers. I make no apology for this design effort. The frame is a fundamental part of driver. Its size and mass forms a critical part of the damping of the power-train, absorbing the oscillations and resonance generated from the power-train. The covers form a part of these processes.

Apart from the current Alpair 12, I haven't seen any significant limitation on box design and implementation. For those Diyer's who have concerns, the forum is quite supportive on build design and bracing.

In summary, the covers should be used where practical. They do make a difference to the rigidity of the frame and operational stability of the driver. While not critical, given the design and performance philosophy behind the Alpair series, I will always design and advocate for the prime optimal, rather than the reverse.

As you've gathered, I'm busy working on new Alpair 12. Also MAOP cone design and a new self assembly driver. This unit will likely have to be built from CNC's alloys so I'll be really busy on its component frame design in the new year.

Cheers
Mark.

Last edited by markaudio; 20th December 2011 at 09:40 AM.
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Old 14th December 2011, 04:37 PM   #10
chrisb is offline chrisb  Canada
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My 2cents worth:



Quote:
Originally Posted by markaudio View Post

Working through your points in their order:

1. In some parts of the world MA suppliers carry units with the mounting rings attached. While in other parts of the world drivers and mounting rings come separate so the user can choose to use the ring or not. Thus some users have the choice to use or not use the rings while other users have to deal with units with the rings attached.

2. The earlier MA drivers did not have mounting rings. If you want to use a current generation driver with a mounting ring in an older enclosure, you would have to reroute the rebate cutout of the box.

I'm with you on these 2 points. I don't always get the choice to supply loose covers as some dealers don't want to handle component(s) product. I'm working hard to encourage dealers to accept all Markaudio production rather than "cherry pick". Some dealers aren't comfortable with end-users (Diyaudio members) having direct connection with me. Its an debate about the freedom of end-user choice while for the dealers, they worry about warranty issues to do with possible in-correct application of covers and similar support items. Its part of the reason for the change in the European distribution arrangements.
those of us DIYers not directly involved as resellers or direct marketers of our own product or designs can easily overlook or underestimate these issues, which could well be far more frustrating than the engineering / designing itself.

Quote:


3. Drivers with the mounting ring are more difficult to flush mount on the baffle which raises the possibility of additional edge diffraction around the cutout.

I haven't (as yet) seen any evidence on diffraction, but accept that where a very narrow baffle design is deployed, care and skill will be needed to attain a flush mount to minimise any effect.

I've built more than a few enclosures for virtually every model of Mark's drivers to date, and have the great advantage of access to a CNC router for machining of baffles and occasionally, holey braces. To be honest the only real issue with fabrication in regards to the rings' extra dimensions is the effect on some of the very narrow enclosure designs, such as the popular FH3, and of course ensuring that accurate measures are sent to the CNC programmer. As with any manufacturer seeking to continually improve design performance and/or simply production, from time to time Mark may change basket/frame casting dimensions - the onus is on the end user to verify those have been factored into build design. I've goofed more than once myself by referring to published dimensioned drawing of the wrong model or generation of driver. The increase in diameter of the extra ring is 5mm – hardly a significant factor – but as noted below, the depth may be.

Quote:

4. Also the baffle rebate is deeper with a mounting ring driver so the stiffness and damping integrity of the driver/baffle is diminished vs. a ringless driver/baffle combination.
This is of course the more pertinent issue - the magnitude of which will vary depending on individual builder's chose materials. Without igniting yet another wearisome flame war on "which is better material / construction technique", it's probably safe to say that for drivers of the mass and intended operating conditions of any of Mark's to date most builders would normally select sheet goods of between 18-19mm (nominal ” ) for baffles, and perhaps something different for the rest of the enclosure. So in the case of the Alpair7.3, flush mounting entails a rebate of 9.9mm, which obviously leaves less than half the sheet’s core – further complicated by the requirement for relief of the rear side of driver cut-out by chamfer or round-over. Here’s where I think a high quality multi-ply unquestionably trumps MDF, HDF or particle board. MDF has heat tempered surfaces, which when removed along with more than 50% of the core thickness will significantly reduce its structural integrity / screw holding ability.

The approach that I’ve described and posted pictures of before is to scallop the relief chamfer or round-over around the areas of the basket’s support legs to leave pads the full thickness of the remaining core at the locations of mounting screws. The addition of a brace nested around the driver and coupling the driver baffle to either back or both side panels will substantially stiffen the front panel. I have added laminated a small plate of 6mm ply in the immediate area of the driver on a couple of builds, but with the degree of enclosure bracing I usually employ, honesty can’t claim it makes a sonic difference.

Quote:



5. The MA drivers with or without the mounting ring are significantly larger in diameter than comparable drivers from other manufacturers. The mounting ring just makes the discrepancy more acute which especially impacts the enclosure size for some designs.

I appreciate these points, hence my recommendations remain consistent; Use the cover where: A - Where woodworking skills are sufficient to make adequate support for the driver within the recess, B - keep side wall elevation behind the frame mount to a minimum to mitigate wave reflection onto the rear of the cone. The judgment call is with the end-user on the use of the covers. We've been using covers on Apair 7 and Alpair 10 on 18-mm and 20-mm thick baffles, cutting recesses on Ply, MDF and solid woods with no structural problems on a variety of box designs.

Markaudio driver profiles, particularly the frame O/D's are significantly larger for the given cone diameter when compared to other makers. I make no apology for this design effort. The frame is a fundamental part of driver. Its size and mass forms a critical part of the damping of the power-train, absorbing the oscillations and resonance generated from the power-train. The covers form a part of these processes.

Apart from the current Alpair 12, I haven't seen any significant limitation on box design and implementation. For those Diyer's who have concerns, the forum is quite supportive on build design and bracing.

In summary, the covers should be used where practical. They do make a difference to the rigidity of the frame and operational stability of the driver. While not critical, given the design and performance philosophy behind the Alpair series, I will always design and advocate for the prime optimal, rather than the reverse.

As you've gathered, I'm busy working on new Alpair 12. Also MAOP cone design and a new self assembly driver. This unit will likely have to be built from CNC's alloys so I'll be really busy on its component frame design in the new year.

Cheers
Mark.
the name on these products is Mark Audio, so regardless of the witty repartee, ultimately he’s the boss – try to engage in this type of conversation with Fostex engineers.
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Last edited by chrisb; 14th December 2011 at 05:01 PM. Reason: softening of concluding sentence
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