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Old 07-14-2012, 01:52 PM
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StevenZ StevenZ is offline
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Mark Audio Alpair 12P Pensil Build

Hey guys,

Just thought I should start a quick little build log here for my newest speakers. As some of you know, I've picked up a pair of Mark Audio Alpair 12P full range drivers. These are Mark Fenlon's newest top of the line (as well as largest)drivers which use a Japanese paper cone, as well as Japanese suspension parts, non-resonant plastic frame, reversed roll rubber surround, etc. They are made in small batches and are hand assembled in China with Mark Fenlon carefully watching over quality control to make sure that each pair comes out perfect.

On to the build.

I drew up the cabinet in AutoCAD and ported it over to our CNC router. Here is a quick video of the CNC router cutting the parts out. *Volume warning, it may be loud*.

http://www.youtube.com/watch?v=KXe8WVix4zA&feature=plcp

This original enclosures were supposed to be out of Domestic hardwood core plywood but it seemed my machine wasn't calibrated properly as well as the material being under 3/4" so I threw away the entire sheet and started over. This time around I got some true 3/4" MDF and triple checked the machine parameters to make sure everything would be perfect before wasting another sheet. The parts came out absolutely perfect, accurate to .0001".

Moving forward, I had a little time this morning to throw the enclosures together. Here are a few photos of the build. As you can see I opted for window bracing instead of the original "holey" bracing called for in the plans. As of right now they are waiting in the finish room and have a couple coats of sealer already thrown on. Monday they will get an off-white paint sprayed onto them and should be fully mounted by Wednesday. I rounded over the front edges to give it a "softer" look and reduce diffraction.

Also, as you guys can see I added more material to the inside of the cutout due to the flush mounting rebate being so deep, only leaving 1/4" material to screw into. I added 1/2" more which gives 3/4" material to screw to. I did a small round-over on the inside edge of the cut-out but I don't think it's adequate as I believe that the driver will need more room to breathe. Soo.. with the enclosures already sealed up I'll just take a small sanding wheel from a dremel and chamfer the inside edge a bit. Shouldn't be a problem, just a little time consuming.

Anyways, I'm excited that I've made progress on the enclosures and can't wait to listen to them next week. Hope you guys enjoy!


Cheers,
Steven
Attached Images
File Type: jpg 2012-07-14_10-27-53_761.jpg (47.1 KB, 118 views)
File Type: jpg 2012-07-14_10-28-06_731.jpg (47.1 KB, 90 views)
File Type: jpg 2012-07-14_10-28-18_593.jpg (47.3 KB, 127 views)
File Type: jpg 2012-07-14_10-28-31_298.jpg (51.7 KB, 111 views)
File Type: jpg 2012-07-14_11-35-52_41.jpg (46.4 KB, 112 views)
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Last edited by StevenZ; 07-14-2012 at 01:56 PM.
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Old 07-14-2012, 01:58 PM
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Here are a few photos of the drivers. The drivers are sold in pairs with matched parameters. This set is matched at 44hz.
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File Type: jpg 2012-06-21_18-36-44_809.jpg (35.4 KB, 60 views)
File Type: jpg 2012-06-21_18-37-18_732.jpg (46.2 KB, 102 views)
File Type: jpg 2012-06-21_18-37-47_602.jpg (38.4 KB, 107 views)
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Old 07-14-2012, 02:19 PM
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Old 07-14-2012, 03:38 PM
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Great build pictures.

Patiently awaiting your thoughts on this build.
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Old 07-14-2012, 04:06 PM
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+1

I'm trying to decide which direction I'm going to go in for these drivers. Seems like there might be several available soon.
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Old 07-14-2012, 05:25 PM
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Thanks guys! I talked to a few people who have already compared the Ken style enclosure and the Pensil and the general consensus is that the Pensil, even standard sized, walks all over the Ken style box. I would have gone with the Super Pensils to gain a bit more bass but the dimensions were killing me. The "Standard" Pensil is more aesthetically pleasing and should be able to blend in well with the room by opening up more placement options.


-Steven
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Old 07-14-2012, 05:33 PM
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Old 07-14-2012, 06:55 PM
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Quote:
Originally Posted by StevenZ View Post
Thanks guys! I talked to a few people who have already compared the Ken style enclosure and the Pensil and the general consensus is that the Pensil, even standard sized, walks all over the Ken style box. I would have gone with the Super Pensils to gain a bit more bass but the dimensions were killing me. The "Standard" Pensil is more aesthetically pleasing and should be able to blend in well with the room by opening up more placement options.


-Steven
So what are we talking about as far as bass in the two Pensil designs?
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Old 07-14-2012, 10:57 PM
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Quote:
Originally Posted by ejfud View Post
So what are we talking about as far as bass in the two Pensil designs?
Honestly I have no idea. The designers of the Pensil cabinets (Scottmoose & Planet10) absolutely refuse to publish any measured response graphs or even give a general estimated frequency response. As to why they don't is anyones guess. Also, I seem to get in trouble with Planet10 every time I don't use his signature 'holey' bracing for his enclosures and am awaiting a solid response from him as to why he thinks my window bracing will hurt the performance of my build. I'll post his response here if/when he replies.


Steven
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Old 07-15-2012, 08:05 AM
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So, Dave says that with my bracing it may disrupt the 1/4 wave TL and adversely affect the bass response, though another fella answered (Bob Brines) and included that he's done the same bracing in many TLs of his own and has had zero adverse affects and no measurable differences in sound. Bob did recommend more bracing, though, but to be honest my bracing is primarily to allow the polyfil to stay in the enclosure without falling and coming thru the port.

If I hear excessive panel resonance I'll add some decoratively cut hardwood panels to the outside to stiffen up the enclosure a bit, though, the reason I used MDF is because of it's natural panel damping properties. In my personal opinion, and experience with many building materials, I favor the acoustic properties and damping of MDF over birch plywood. Though this thread isn't the place to get into such a topic, it's merely a personal preference. I'll keep you guys posted and update the thread with any findings as I move along.


Thanks,
Steven
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Old 07-15-2012, 04:38 PM
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I built my Jordan two ways with window bracing. Bob's design is built this way and they sound great.
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Old 07-15-2012, 09:42 PM
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That was my first time seeing wood cut with cnc... Are there companies out there that you can provide drawings on paper to them and they provide you with a finished cut set? Being a condo dweller I don't have access to large saws...
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Old 07-16-2012, 05:38 AM
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Quote:
Originally Posted by Rick Vestal View Post
That was my first time seeing wood cut with cnc... Are there companies out there that you can provide drawings on paper to them and they provide you with a finished cut set? Being a condo dweller I don't have access to large saws...
Absolutely. Most larger custom cabinet shops should be able to help you out. I can't be sure on how much they will charge, though. It only took me about 10 minutes to draw the program, and another 4 to cut the material. So all in all, 15 minutes from design to finished product.


-Steven
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Old 07-16-2012, 09:38 AM
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Looking awesome Steven! Keep up the good work! "The eyes of the Ranger are upon you"
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Old 07-22-2012, 08:13 PM
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Copied from my other thread "I Love Full Range!"

Well fellas, it's been a while but I finally had some time to get the cabinets sprayed and drivers mounted. Unfortunately my local supply store for polyfill was closed today so the cabinets have zero stuffing in them but my results are pretty damn good so far.

So far, even though I'm in my 1st hour of listening, they're amazing. I have always loved the sound of Mark Audio drivers, and these are no exception. Simply beautiful sound. Well balanced and as good as you can ever want from a full range single driver.

I'm using the "standard" sized pensil cabinet and am hearing some very good low end extension and I'm sure the "super" Pencil enclosure will produce a bit more. For my listening habits and small listening room I feel the standard pencil is perfect. It's aesthetically pleasing and easy to properly place in a small room due to it's small foot print.

All in all i can't wait until they're fully broken in. The manufacturer suggests 100 of soft listening with natural instruments and then gradually increasing the volume. It's sure going to be a long process as I'm already feeling the urge to crank it (and have done so a few times ).


Cheers,
Steven
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