mrogowski

Here are more shots of Joel's progress: Another shot of truck He decided to paint his Audison amps - nice A shot of his Eclipse deck going in The MLI's in their pods A shot of his Memphis amp - not sure why the cap is there tho.. Here he is doing some work on the doors (I think)

Ok, so this guy from Calgary ordered up some subs a little over a year ago for his home theatre setup. A little over a month ago, he phones me again telling me they aren't enough. We start sharing info and I find out he was the Canadian car audio champion back in the early 90's. So after a 17+ year hiatus, it just so happens that Big Dave is planning to get back into the car audio scene once again. He calls himself 'Big Dave' for just reason - he's bigger than me and has that deep, husky voice you can only associate with men of larger stature. Eight IXL-12's, four MLI-65's and a 2000 Ford F250 bought primarily for car audio, this should be a very interesting build. He's also into a lot of customizing (read fiberglassing, totally modding of stock environment, etc. etc.) Here's a shot of his trophy "army" with the car that made it all happen - circa early 90's.

Nice score!

Here is the crossover design with a response curve. I listened to it for a good hour using a variety of music (rock, pop, jazz - no rap though). It sounds quite balanced. A person can add a resistance circuit if they feel the need to drop the highs a bit. Keep in mind that this is a nominal 2 Ohm load setup so make sure to use a suitable amp to drive it.

Indeed, some plywood is more flexible but that is not because of the way it is made, but rather how dense the wood fibers are. MDF bends under its own weight because the wood fibers are very weak to begin with, are surrounded by glue and do not support each other. If MDF was structurally as strong as it is dense, it would be like concrete. Of course, there is good and bad ply. Many folks here talk about 13 ply Baltic. That stuff is super expensive but superior in all respects. I like to use Fir as it is a hardwood and much denser than your standard Birch. m

Indeed.

Strength comes from fiber length. MDF has fibers that measure at best, a fraction of 1mm in length and are surrounded in glue. Since the structural strength is in the fiber itself and not the glue and the fibers are aligned randomly there is little strength. Plywood however has very long parallel fibers, each supporting the other. On top of that, each layer of ply is positioned at 90* from the other, so you end up with strength in all four directions. Try breaking a ply board - you will notice how much it splinters verses a clean break with MDF.

Agreed. If you plan to rebuild, use plywood for the box and MDF for the bracing. I was chatting with a Civil Engineer friend about it, and he suggested the bracing material be MDF. Reason being is MDF is already compressed to extremes at its edges, which makes it excellent for stopping the box from compressing/expanding. There simply is *no* give there whatsoever. Where MDF fails miserably is in it's structural support (along the flat surface), which is the reason to use plywood instead. All of my finished boxen will use this method from now on...

What is the problem with your original build?

Yeah, I guess you're right. I'll do that.

Sounds like the new model will be a winner. I might as well close up shop now...

Excellent point on the car movement Todd. That never crossed my mind. A person would have to ensure the cabinet is sealed real tight to minimize such things. The weight thing is largely dependent on how strong/stiff your suspension is.

Glad to hear it Aaron. The SEAS tweeter we selected it pretty decent. If folks at DIYMA/here are interested, I'd be happy to post the crossover schematic we will be using.

** Update ** Joel responded with his equipment list: Vehicle: 1999 GMC Sierra Extended Cab Head Unit: Eclipse AVN 5500 Front Amp: Eclipse LPX 4001 (2) Sub Amp: Memphis Audio 4000d Tweeters: SEAS 27TFFNC/G NEO Fabric Dome (2) Mid-Bass: Mach 5 Audio MLI-65 (4) Subs: Mach 5 Audio SPL-15 (2) Mid/High Crossover: Custom designed passive 2-way He will be taking more pics this weekend.

I think its a Chevy... Anyway, Joel has done a fair bit of customizing on this unit and will continue to do so through this winter. As the first pic shows he has removed the door handles, replacing them with an electronic system that ties into his Viper car alarm. He also did some front and back end frame work. This picture does the truck paint job no justice whatsoever - you would have to see it live to appreciate it The next shot shows the interior with the back seat ripped out. He will also be ripping out his single 12" Diamond Audio sub, replacing it with two SPL-15's. The cap will also go, but the nice Audison 1kw amp stays to power the front stage The next shot shows what he was running before. He does fiberglassing for a living so new pods will replace these And here begins the pod build. He decided to go with two MLI-65's per side The next shot is either a breast implant gone bad or Joel's pods ready for sanding This next shot basically speaks for itself Thanks to Bud, we acquired a Memphis 4000d amp to drive the SPL-15's Joel is getting a second Audison amp for the other front channel. He will have 2kw on tap for the front end alone. More pics coming - sub box, Joel's head unit, accessories, etc...

Looks pretty good. The only thing I might suggest you look out for is excessive flexing of the port top and bottom. If you see this occurring glue a brace attaching the two, running from front to back.

Depending on the excursion capabilities of your active drivers, passives and planned input power, this will determine how many you will require. For example. you could squeeze two IXL-10's per one MJ-PR provided you don't drive the subs too much below the tuning of the box. But Jim is right, the general rule for passives is about 2x the cone area/throw to each active driver. Best, Mark

Well, I'm glad you like it. Post up some pictures here, and if you want, throw them up in the Builder's Corner as well for prosperity... m

Yup.

Freezing (this is what I call it) occurs when a driver is placed in a bass reflex with a very long port and is pushed to levels above and beyond normal port compression. At these high levels the enclosure no longer acts as a bass reflex enclosure and for split instants at certain frequencies (if memory serves its at resonance) the driver will actually freeze up. It was a problem years ago as we had to deal with it when designing, but technological advances have minimized this issue. Using port flares is one way. Ensuring that you have adequate port area for the size of driver is another, but this of course, can work against you.

Yeah, I agree. A box that small would definitely be affected by driver volume.

I have soft parts for MAW-15's if you want 15 inch sizes. Send me an email through my website.

0.11 cubes.

Sealed, just big enough to enclose the driver is about right. Ported, not much bigger than that. Hahaha! We should call you "Mr. 0.707" Well, I couldn't go to .85 even because the sub wouldn't fit in a box that small. The fun part is going to be building the .5 @ 25hz that I'm planning. That's an awfully long pipe. Aren't you worried about port resonances or driver freezing? Glad to hear it (pun intended)...

Nice looking. Too bad I/we are in Canuck land...