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I built a sub - the Overdrive10

ABall

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I used 3/4" MDF. My PR is surface mounted, and I have used the same box. I believe he made the front panel thicker to accommodate the flush mounting and retain original spacings.
so we have 18mm in the UK which is close to 3/4, Im going for 2x25 so 50mm for a very solid box. That will pull the PR forward even though Im going to flush mount it as is here and the amp will be further back slightly, all in all im guessing less of the PR and amp inside the enclosures equals slightly more volume, I just dont know if its that crucial to the operating parameters.

Heres my confusion on the front baffle. regardless of the difference between surface or flush mount, these 2 holes dont look like they are the same distance from the internal walls, yours looks like the the 4 extremes are cut right back to the walls and this one looks like its stepped in more.
 

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Wolf

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It's an optical illusion then as it looks the same to me.
 

Wolf

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Nicely done. Though you say passive radiator. If its internal is it not Isobaric?
No, isobaric would involve 2 equal woofers with constant space between the cones. In the case of this alignment, the woofer and PR are not tuned to the same frequencies, and the PR has no motor drive.
 

Wolf

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so we have 18mm in the UK which is close to 3/4, Im going for 2x25 so 50mm for a very solid box. That will pull the PR forward even though Im going to flush mount it as is here and the amp will be further back slightly, all in all im guessing less of the PR and amp inside the enclosures equals slightly more volume, I just dont know if its that crucial to the operating parameters.

Heres my confusion on the front baffle. regardless of the difference between surface or flush mount, these 2 holes dont look like they are the same distance from the internal walls, yours looks like the the 4 extremes are cut right back to the walls and this one looks like its stepped in more.
You could just add more bracing to make up the difference. However, if the volume is the same in the chambers (and it should be), and the through hole is the only thing changed, then the PR and Amp should be offset to make up the difference. Or, you can reduce the front chamber to compensate- as long as mechanical operation clearances are met.

However, I would not sweat a minimal increase in the sealed volume. The increase in volume could reduce the air spring and allow more Xmax than needed or wanted. The PR volume is a lot more critical to get the proper tuning.

To ensure performance, I would build the box as I did, and layer another perimeter atop the first; top bottom and sides. The amp mounting can have more wood in it, just recess the amp to keep terminals safe from casualty. You will need the back to sit on the floor when you install the PR.
 

ABall

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You could just add more bracing to make up the difference. However, if the volume is the same in the chambers (and it should be), and the through hole is the only thing changed, then the PR and Amp should be offset to make up the difference. Or, you can reduce the front chamber to compensate- as long as mechanical operation clearances are met.

However, I would not sweat a minimal increase in the sealed volume. The increase in volume could reduce the air spring and allow more Xmax than needed or wanted. The PR volume is a lot more critical to get the proper tuning.

To ensure performance, I would build the box as I did, and layer another perimeter atop the first; top bottom and sides. The amp mounting can have more wood in it, just recess the amp to keep terminals safe from casualty. You will need the back to sit on the floor when you install the PR.
Cheers Wolf, I must be crazy building this with so little knowledge of how it actually works but I feel it will be worth it and appreciate the help.
 
OP
MrPotatoHead

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so we have 18mm in the UK which is close to 3/4, Im going for 2x25 so 50mm for a very solid box. That will pull the PR forward even though Im going to flush mount it as is here and the amp will be further back slightly, all in all im guessing less of the PR and amp inside the enclosures equals slightly more volume, I just dont know if its that crucial to the operating parameters.

Heres my confusion on the front baffle. regardless of the difference between surface or flush mount, these 2 holes dont look like they are the same distance from the internal walls, yours looks like the the 4 extremes are cut right back to the walls and this one looks like its stepped in more.
OP here. I think it's because you can see the edges of Wolf's side panels whereas you're looking at just the baffle on mine. I kept his internal dimensions but changed the outside dims to accommodate my front bars and to recess the amp in the back, etc. Let me know if you have any other questions.
 

Holmz

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The volume of the Overdrive10 (soon to be rebadged Kilauea in kit form) is only 26 ltrs. 18/8ltrs respectively. The boost yields an F3 close to 22Hz, and the natural bandwidth is 30-65Hz with a 50Hz PR tuning.

Nice looking sub.

How did you arrive at 30Hz?
And would the OP be better off with a 20-50 or something a bit lower for HT use?
(Maybe even 16-40Hz ?)

I am asking because I have a couple of subs and PRs, and want to put them onto the LFE outputs.
Should I be shooting for 20, 25, or16 Hz??? @Wolf
 

Wolf

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The system with the boost the amp provides results in a bandwidth of 22-65Hz. Without the boost, the natural corner frequencies are 30Hz and 65Hz, anechoically.

Placing this sub in a room, will allow for different lower extensions because of the room itself. I use mine for HT, and don't want for much more. It is quite capable.

The bandwidth is mainly a function of the driver in its box, as bandpasses are optimal over a specific range for the drivers and boxes used. If I wanted lower anechoic response, the output may suffer. The 65Hz spot is about where some rooms peak, and being under this steeply can be an advantage. Additionally, it is more than an octave below 150Hz, where bass becomes extremely localizable. I don't normally use a subwoofer above about 80Hz for these reasons, and prefer 70 and below. The active xover helps if needed to keep the rolloff about there, and combined in the bandpass makes about an 8th order rolloff. That is quite the benefit.

As tar as range goes, 22-65 anechoic is pretty darn good as subwoofers typically go. The other thing is that these are -3dB points, and MANY commercial subwoofers spec the -10dB points for performance and don't meet this spec.
 

ABall

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OP here. I think it's because you can see the edges of Wolf's side panels whereas you're looking at just the baffle on mine. I kept his internal dimensions but changed the outside dims to accommodate my front bars and to recess the amp in the back, etc. Let me know if you have any other questions.
Thanks, yes it looks like the circle is squared off at 4 edges in Wolfs where yours isn't indicating the internal dims are different to me. Regardless of having a larger outer the cut out for the PR looks as if its about the same dimension as the inner volume so the hole should look the same on both no?
 

Wolf

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The PR face has an additional 1.5" in H and W over that of the active driver inner baffle.
 

ABall

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As you say it must be an optical illusion. Or I just drink too much.....
 

jamescarter1982

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Over a year ago I posted here that was searching for a design for a DIY sub. There were several great suggestions, but I ended up going with the Overdrive10 designed by @Wolf. It's a bandpass design with a 10-inch Dayton driver and a passive radiator. I bought the hardware a year ago and finally got around to putting it together.

I already have a Hsu black cube so I decided to mix it up a little. Rather than making a black body with a speaker grille, I went with a plywood top and bottom with 1/4-inch aluminum rods that cage in the PR. I don't like designing things that people have seen before so this is where my brain went. My friends just say, "Huh. Okay..." so I know it's not for everyone.

I think it sounds great but, honestly, I don't really know how to evaluate a sub. It seems to do what it's supposed to do. With two subs, the presentation is just so much bigger and for HT the change is impressive. The first film I watched was Dune and I was blown away in the first ten seconds.

I'm hoping @Wolf will hop on to answer any technical questions.

Brett

PS Here's a photo of the stereo rack I built last year.

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really impressive love the stand and the novel grille on the subwoofer
 
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