Wes T

Please review my DIY ultra low budget dual sub setup

After two short years of ownership the one nice piece of equipment that I have, my Yamaha YST SW800 sub, fried while I was watching T3. Although I am sad that the one nice expensive thing I have in my otherwise cheap HT died, I now have an excuse to buy new stuff. Of course, I am really low on funds. Afer much research here and other forums I have decided on the following. I picked up an MCM 250 watt plate amp for 89 dollars. I had the biggest problem finding suitable drivers until I stumbled on the MCM 12 inch high excursion woofer MCM 55-2330. I just got two of these today and I am astounded at how great these look and feel for the low price of 58 dollars each. These seem to be the bang for the buck kings that I have found with the biggest Xmax for dollar I could find. After crunching the numbers for this sub in WinISD I need to build a box at 3.8 cubic feet with a 9 inch deep 4 inch port to yeild a FS of 26 Hz. The response curve is flat all the way down to 30 Hz. I plan on building 2 of these boxes and running them in parrallel off of the MCM amp. My reason for two of them is because I grew up on the old school stuff from the 70s when you had 2 big honkin' speakers, and I don't like the way my system or many others I have heard sound with just a single sub. I want it to sound like the stereos of old where you had bass on both your left and right sides, even though I am going to be running them summed from the one amp. So what do you all think? Am I going to bathing in gobs of clean bass or is my system going to sound like a cheap-ass disaster?

2 questions. Do I pack any polyfill in the box and is there a poor man's way of adjusting the phase besides by ear?

I would appreciate it very much if anyone can point out any glaring errors in my plans or offer me any tips on doing this better without costing any more money.

Wes T

ThomasW

Line the interior walls of ported boxes with damping material. Don't 'stuff' (pack) the box.

The only poor mans phase adjustment is by reversing the driver leads so it's 180 degrees out of phase.

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TimForman

OK ThomasW, help me out here. Many ported sub designs call for polyfil i.e. the Adire Alignment with 64 ounces of polyfil. You're saying this is incorrect?

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GrahamT

He's saying not to completely fill (pack) a ported enclosure whereas this is fine in a sealed sub. Lining the sub walls with layers is fine as long as the fill isn't too close to the port openings.

Wayne Ernst

That's correct. And probably the best way to do this is to go to a fabric store that sells sheets of polyfill by the yard. Pick up a few yards of polyfill and then staple it to the inside of the cabinet walls. This should keep the polyfill away from the ports and amplifier.

\"My reality check ... just bounced\"

TimForman

Oh, I don't know about that. I like the "indoor snow" effect.
I thought that might be what was meant by that statement, just wanted to make sure. BTW, I've heard good things about the MCM drivers you've chosen. Good luck!

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Geoff L

I agree with the sheet poly fill and lining the walls of the cabinets to start for sure..

Later, (if you feel like playing a little), you can always experiment with adding a little extra fill to taste. An SPL meter and Hz-test disc is of a great way of seeing just what effect this has on the tuning, in room extension, and over all freq response...
Hey the snowing effect is fun, well once anyway!

I'm not familar with the MCM drivers you have choosen, but assume their 8-ohm load per driver. Thus when wired up P, the amp will see a safe 4-ohm load.

Best of luck with the project, and your more than likely DIY hooked from here on out!

Tuff break on the Yammi-800, but you'll be Bass'en again soon...

Cheers
Geoff

Wes T

Wow. Thank you all so much for all of your responses! Since it looks like things are going to work OK I am heading out to home depot to get some MDF. Hopefully, they will cut all the pieces for me and all I will have to do is assemble the cabinets. I will get some roll batting and line the inside of the enclosures with that, taking care not to get it too close to the port. I will staple it tight in a 6 square inch area behind the port.

Geoff, yes the MCMs are 8 ohms. Thanks for assuring me on the load for the amp. Back when I started I used an Apexjr amp with two old radio shack mach twos for bass. They worked pretty good. The amp is still used today for bass shakers at a 4 ohm load and it works fine.

ThomasW. The reason I was asking about phase adjustment is because the MCM amp has a variable 0 to 180 degree phase knob on it. I will work with that later as I learn more about properly tuning my system for my room. The more I read about tuning the more complicated things get. Gone are the days when you just plopped down a pair of big butt speakers and called it done eh?

Thanks again all. -Wes

Wes T

Got the first one built today. Wow! Nice and very low bass. It is funny, I first hooked it up to my ApexJr amp that normally drives shakers and I had it sitting a few feet out from the wall. You didn't hear much bass until you walked all the way out of the room. I replaced the amp with my MCM 250 and put the sub in it's new place and I am astounded at the sound this thing makes for under a hundred dollars! I can't wait to add the second one! I have one mis-cut board from the L place that I have to get replaced before I can finish the second enclosure. I don't need to finish the enlosures with anything since my whole system is hidden so the raw MDF finish looks great. I am now a total believer in DIY bang for the buck! Pics coming. -Wes

Wes T

The subs are done and I couldn't be happier! They sound spectacular. I get very smooth and low bass that sounds great with my music and movies. They easily get up to 110db at my listening position and I am very pleased with the even sound I get from two of them. At a total cost of around 300 dollars for everything I am extremely happy. Pics are here http://photos.yahoo.com/westanizer

-Wes

TimForman

So, do you still miss your Yamaha sub?

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