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Elite Shackster
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Discussion Starter #1
I have a thread on here with what I'm going to build. I cant however seem to find anything anywhere with others building this kind of design. Surely I cant be the first? :huh:

Has anyone else done a DIY push pull sub, or know where there are examples of this I can take a look at.

Cheers guys
 

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Elite Shackster
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7,142 Posts
Discussion Starter #3
Yeah I know. My main forum for home AV isnt that big on DIY sub building and so far (other than speaking to Ken Kreisel) I cant find anyone that has given this a go. Maybe I am the first, I'd be surprised but I am wandering why no one has tried this, is there a reason why I wouldnt/shouldnt?
 

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Here's one, but the description is in finnish. Since the push-pull configuration "only" halves the VAS-value and cancels out some distortion, it isn't worth the extra cost of the second driver for many. In the old days, drivers had lower BL and larger VAS - this made the push-pull a good alternative to having a huge box. Nowadays, new drivers with ultra-strong motors optimized for small boxes have rendered the push-pull configuration almost obsolete. The major drawbacks for these drivers over the push-pull are low sensitivity and increased distortion. Also the increased demand for large displacement has reduced the demand for push-pull subs since the second driver is "wasted" (not contributing towards more output). But if you have access to cheap drivers and you are looking for a small box with good extension, good sensitivity and reduced distortion, the push-pull might be suitable for your needs. Anyways, keep us (or me at least :)) posted.
 

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Elite Shackster
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Discussion Starter #5
I have seen that said before about how push pull is mainly about making rubbish drivers good. There is one other thing though, you can push the sub harder as the cone movement is reduced, with plenty of power as I will have you can gain some extra output, and distortion isnt introduced as a result of this harder pushing due to the design type.

I can see why people wouldnt want to spend extra on the extra driver, but even with this extra expense my DIY will still come in at less than my PBU, so that isnt an issue for me, especially if the end result outperforms an Ultra, the pay off will be considerable. For me its less about the cost and more about the end result. As I build this, a couple friends are also using the same drivers in 2 other types of enclosure (one a sealed box design, one a ported design) so a comparison will be done to see if the push pull design is still of benefit with modern drivers.

I will keep things upto date here :yes:
 

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Elite Shackster
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7,142 Posts
Discussion Starter #7 (Edited)
I'm going for compound ( think its called) not isobaric, so double the vas. 150 litre enclosure is what I'm aiming for. I'm going for a larger cabinet so the tune is lower, I really dont want to lose the SVS PBU depth/power. The vas of my drivers is 197, but in a sealed enclosure that halves IIRC. A single driver modelled in an sealed enclosure performs very well in 75 litres, so I'm aiming for double that.
 

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I see you already have plans regarding what you want to build. Have you by any chance looked over at http://www.deepsurplus.com. They have been building M&K subs out of the parts they got at the bankruptcy auction, another thing to consider. I myself chose to go a different route with hopefully some better quality drivers. I ended up designing my own using two Peerless 830952s and an Oaudio 500w plate amp. Build thread: http://www.hometheatershack.com/forums/diy-subwoofers-sealed-ported/20944-peerless-push-pull-sub-build.html It is great for music and does well enough for movies in my little bedroom. I originally used a Sony SA-WX700 and loved the sound it put out. So the idea was to go bigger and better. It was an experiment and is probably as close as I'll ever get to an M&K sub, especially now that I've started down the DIY path. I wanted a "high end" push-pull just to see what it's like, next time I'm gonna go for something different like an AE AV series sub or a Mal-X. It'll be nice to compare and see what has the "tighter" sound. You can check out Vance Dickason's Loudspeaker Design Cookbook as he talks about push-pull a little bit.

I myself found this page helpful for understanding the different designs:
http://www.danmarx.org/audioinnovation/theories.html

Along with this:


As far as my build goes I was aiming for a volume right around 88.5 liters and I think it ended up bieng closer to 90 liters over all and I'm afraid it was a little big. I modeled it out with BassBox 6 Pro but I can easily bottom out the subs on movies with the gain on the Oaudio 500w Plate Amp (which I can recommend) at half. With music I can turn it up a little higher as it doesn't have the big "sudden" amounts of deep bass. So if I could go back I think I might make it a little smaller. Currently I'm thinking about my options with some closed cell foam or something else. The total cost for the project came in right around $600 and I'm very content with the results. Hope this is of some use to you. :T
 

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Elite Shackster
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Discussion Starter #10
Thanks thats an excellent response and just what I was looking for. I was thinking of using 1" mdf and bracing it, but I'm loving the twin 3/4 inch panel design, should be much better.

Cheers.
 

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It's actually 1/2" on top of 3/4". I wanted to flush mount the drivers and I had decided to make the interior braces out of 1/2". I decided to make the two speaker baffles 3/4" with 1/2" to flush mount the drivers, the 1/2" was perfect for flush mounting with the speaker gaskets under the drivers. Then I just decided to make all the sides 1/2" on top of 3/4" for density and strength. The whole sub weighs in around 90lbs I'm guessing.
 

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Elite Shackster
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Discussion Starter #12
One thing that I'm not sure about is the bracing. I noticed you have a brace behind the driver and most manufacturers seem to try keep this area clear by just cutting a tunnel out of the brace(s) behind the driver. MK themselves dont seem to bother with much bracing it all so I'm still unsure how best to go about it. I definitely want the flush mount thing though.
 
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