Build thread! Unknown 12" Sony driver... - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 41 Old 03-28-10, 11:18 PM Thread Starter
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Re: Build thread! Unknown 12" Sony driver...

Pic of the bottom endcap sitting in place. Just wanted to see how it fit. You can see the driver flush-mounted inside. Fits like a glove. Which is good. Air leaks will NOT be tolerated!!!

In this pic, the sub is upside down. I am searching for the dowling for the legs.

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post #12 of 41 Old 03-29-10, 11:21 PM Thread Starter
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Re: Build thread! Unknown 12" Sony driver...

Some more work today:

First up is the pilot hole for the port tube hole. Needed to go all the way through because its going to be 3 layers of 3/4" MDF so I'll have to do two passes with the hole saw. One pass from each side:



Port tube (4" PVC) fits like a glove!!



Only problem, port is too long! I wanted at least 1.5 times the diameter of the port clearance from the driver magnet. Well its closer than that. Like 3.75 inches away. So I had to cut 4 inches off and now I'll get either a 45 degree elbow or a long-sweep 90 degree. Precisely why I offset the port from the center. Just in case.



Lastly, I counter-sunk the screws that will go into the 1" dowling that will act as the cab's legs. Should work out great!

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post #13 of 41 Old 03-31-10, 01:41 AM Thread Starter
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Re: Build thread! Unknown 12" Sony driver...

Port tube length HELP!! Ok, so I got a "long sweep" elbow so I could fit my 21" 4" PVC port. Only problem is, the elbow is LONG. How do I calculate my port length now? Surely the elbow is adding length so its not going to just be 21" of straight tube + the elbow?

Any opinions?

21" port tube cut into 17" and 4" pieces:




With the elbow in place. Look how much longer it makes it!

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post #14 of 41 Old 03-31-10, 04:11 PM Thread Starter
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Re: Build thread! Unknown 12" Sony driver...

Any help? Need to know how much length this elbow adds. Or at least how to calculate it.

Thanks.
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post #15 of 41 Old 03-31-10, 04:27 PM
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Re: Build thread! Unknown 12" Sony driver...

Use a tape measure and measure the length along the inside of the bend, then the length along the outside of the bend. Subtract the two numbers, then add half that difference to the length along the inside of the bend. This gives you the length along the middle, which is what you need.
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post #16 of 41 Old 03-31-10, 07:07 PM Thread Starter
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Re: Build thread! Unknown 12" Sony driver...

Quote:
dyohn wrote: View Post
Use a tape measure and measure the length along the inside of the bend, then the length along the outside of the bend. Subtract the two numbers, then add half that difference to the length along the inside of the bend. This gives you the length along the middle, which is what you need.
Great! Thanks man!
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post #17 of 41 Old 04-01-10, 05:08 AM Thread Starter
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Re: Build thread! Unknown 12" Sony driver...

Well, everything is cut and ready to go. Here's the cab with the port endcap in place and the driver endcap with driver beside it!






And here it is all together. This is just a dry-fit. Going to tape all the seams and then fire it up for a few test tones and demos. I don't want to do all the finishing work only to have it sound like poo. So fingers crossed. Got the SPL meter all charged up and my demo material lined up, ready to go. Sometime tomorrow, I'll be givin' it the trial run!

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post #18 of 41 Old 04-01-10, 05:17 PM
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Re: Build thread! Unknown 12" Sony driver...

I remeber the Sony SA-WM500 they were very popular for a cheap subwoofer. I know a few people who extended the port to get a lower tune.

I can't remember if the amp has a high pass filter on it, as long as it is not too resctrictive I think this subwoofer will very much surprise you with its output.
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post #19 of 41 Old 04-01-10, 07:50 PM Thread Starter
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Re: Build thread! Unknown 12" Sony driver...

Quote:
micb wrote: View Post
I remeber the Sony SA-WM500 they were very popular for a cheap subwoofer. I know a few people who extended the port to get a lower tune.

I can't remember if the amp has a high pass filter on it, as long as it is not too resctrictive I think this subwoofer will very much surprise you with its output.
Right you are brother!

Ran it through some tests today and I was hella surprised!! I couldn't believe it was the same sub. This was just a dry fit with air leaks everywhere, no damping material inside and the port was just sitting in the hole, not quite fitted properly. So it wasn't very scientific....more just a gauge of whether or not I was wasting mine (and yours!) time. Well, I'm confident that I can now "finish" the sub properly.

I first ran the test tones at -8dB below reference. I normally run my subs at -4dB but I wanted to be careful with this one. I don't mind frying it, but I wanted it to last longer than 30 seconds, LOL! This is what I got:

60hz = 94.0dB
50hz = 84.1dB
45hz = 94.3dB
43hz = 97.9dB
40 hz = 94.6dB
36hz = 92.6dB
35hz = 93.0dB
33hz = 91.4dB
32hz = 91.9dB
30hz = 88.3dB
20hz = 72.9dB

I couldn't find all my 20's test tones so there's a bunch of missing data. Clearly the amp has a HP filter on it. So, when everything is all sanded and finished, I am going to run a test through my 500w plate amp with NO HP filter. Should give me a better indication. But aside from all that, this little bit of work has produced a sub that literally crushes the earlier, commerical store-bought configuration. Its night and day. I am also going to raise the tuning a little bit. I think 21hz is pushing the limit of the driver. I am going to try 24hz and see if that hits the sweet spot. Either way, should make an excellent "little" 12" sub for someone for movies, games, or music!

Last edited by favelle; 04-05-10 at 01:57 AM. Reason: typo
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post #20 of 41 Old 04-01-10, 09:25 PM
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Re: Build thread! Unknown 12" Sony driver...

Glad to hear th results look promising, I never would have guessed! It goes to show you never know unless you try.
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