SS Rl-p15" - my first DIY Box Sub

**Egil** · **03-05-07, 02:30 PM**

Hello all!

I recently sold my PB12Ultra, - because I started getting the upgraditus itch, after reading more and more about the new PB13U that'll come. But at the same time, I was lurking around some DIY forums, - and got this "urge" to make one myself instead.

The choice was between a TCsounds 2000 15" and the SS Rlp-15". I wen't with the SS - and I should receive it in a couple of weeks, I hope.

Mike from SS recommended that I built a 200 litres enclosure, tuned to 17hz. Powered by 800-1000watt. If im going to tune the sub to 17hz, the pipe has to be 1meter, and have a diameter of 17cm, which is roughly 35 square inches of port area.

The thing is, I jus't can't find a pipe that has a diameter of 17cm. I can get a 6" PVC pipe (which is rougly 16cm in diameter, - but the INNER diameter will be 15.2cm with that pipe). The next closest thing I can get, is a cardboard pipe, that has an inner diameter of 19cm (im not 100% sure if it's 19cm INNER diameter, it may be 18.2cm inner diameter).

Also! I would prefer having a bit shorter pipe, so the box itself isn't that HUGE. Mike said that if I tuned the subwoofer to 19hz (with that 17cm in diameter pipe), I could shorten the length with 25.5cm.. So I think I will go for a bit higher tuning (19hz), so the pipe doesn't have to be that long.

So my main concern right now, is, should I go with 6" pipe (that has rougly 15.2cm inner diameter), or the cardboard pipe that has 19 (or 18.2cm) inner diameter ? (Mike said that a smaller port area than 35square inches might cause port noise - but he also said that It would most likely not be an issue unless I sit right next to the subwoofer). And - how can I calculate how long the pipe will be (in order to get the right tuning on the sub) ?

I guess I can mention that I plan on using a Behringer EP2500 to drive the subwoofer. .. And that this is my first DIY project, so im a bit green when it comes to TS parameters (and how to calculate length on the pipe etc). But I do have the skill to make the box at least.. I hope

**kano32** · **03-06-07, 02:13 PM**

I was trying to model the port and box but I need to know if you bought the dual 4ohm or dual 2ohm voice coil.

You should download and play around with some box modeling programs like Unibox and WinISD. Here are some links:

http://www.pvconsultants.com/audio/frdgroup.htm - FRD Consortium (unibox is there as well)
http://www.linearteam.dk/default.aspx - WinISD homepage

**kano32** · **03-06-07, 02:27 PM**

For the Dual 2ohm voice coil WinISD shows a 15.2cm (6") port at 62.6cm (24.65") length. Or 18.2cm port with a 94.5cm (32.7") length.

You would probably be fine with the 6" port with both ends flared.

**Egil** · **03-06-07, 03:20 PM**

Hey, - it is the dual 2 ohm I've bought.

Thank you for your calculations - I will go for the 6" flared port, - and tune my sub to 19hz.

If you look at this picture:

Adding a 'flare' on both ends - is the actual size on the pipe stil 62.6cm then- or is it ~65cm as shown on the picture?

And when it comes to the flare itself.. I hope it's not to hard to make one myself, and glue it on the pipe.. I guess it has to be really smooth.. I'll do some research on that

Edit: From what I've read, even when adding a flare, - the actual length is still 62.6cm. I also hope I can buy a 6" flare somewhere in Norway.. so I don't have to make one myself - or order one from the US (not that it's a problem, it's just the waiting that would kill me

)

**Jerm357** · **03-06-07, 04:19 PM**

You could always buy the flares from here. They also have a good Port Length Calculator that will tell you the straight length port required and the flare length port required for a given volume of Box.

http://www.psp-inc.com/

**collo** · **03-06-07, 05:44 PM**

If you're making your own flares, follow this principle:

The generally accepted adjustment is to subtract half the flare radius from the physical length to obtain the effective length. If both ends of the port are flared, the adjustment is done for each flare

**SteveCallas** · **03-06-07, 06:14 PM**

By using a 19hz tune, it will be necessary (not optional) to use a high pass filter in the signal chain to prevent your sub from bottoming with low frequency, loud material. Keep that in mind. If you were to up your design to 260 effective liters with a 6" diameter port that is 30" long, you wouldn't need the highpass anymore.

**Egil** · **03-06-07, 07:16 PM**

Quote:

SteveCallas wrote:

By using a 19hz tune, it will be necessary (not optional) to use a high pass filter in the signal chain to prevent your sub from bottoming with low frequency, loud material. Keep that in mind. If you were to up your design to 260 effective liters with a 6" diameter port that is 30" long, you wouldn't need the highpass anymore.

I was actually going to ask about that..

I plan on crossing my fronts to either 100 or 80hz, let the MBM-12 take of the frequencies from 100 (or 80hz) down to 50hz. The subwoofer im making, will take care of bass from 50hz and down.

In order to cut the subwoofer at the right frequencies, - and to prevent it from bottoming, will this: http://www.behringer.com/CX3400/index.cfm?lang=ENG do the trick ? Or do you have something else/better to recommend?

Btw: Thanks for that picture - it's quite helpful if im going to make one myself

**vitod** · **03-07-07, 01:08 PM**

This is based on the D4 but it's very close to the D2 response. You can go with 9cuft. Port 6"X24" tune to 17hz. I have those very boxes.

**JorgenMan** · **03-07-07, 03:22 PM**

Quote:

collo wrote:

If you're making your own flares, follow this principle:

The generally accepted adjustment is to subtract half the flare radius from the physical length to obtain the effective length. If both ends of the port are flared, the adjustment is done for each flare

If I understand your picture correctly, the "cutoff" point is at half the flare depth, not half the flare radius, right? I'm not trying to be , I just want to make sure I'm understanding correctly.

**collo** · **03-07-07, 05:02 PM**

In this case, it's the same thing....

**kano32** · **03-07-07, 11:41 PM**

Quote:

Egil wrote:

I was actually going to ask about that..

I plan on crossing my fronts to either 100 or 80hz, let the MBM-12 take of the frequencies from 100 (or 80hz) down to 50hz. The subwoofer im making, will take care of bass from 50hz and down.

In order to cut the subwoofer at the right frequencies, - and to prevent it from bottoming, will this: http://www.behringer.com/CX3400/index.cfm?lang=ENG do the trick ? Or do you have something else/better to recommend?

Btw: Thanks for that picture - it's quite helpful if im going to make one myself

I believe he's actually talking about a highpass filter which will taper the lower frequencies which will help the driver not to exceed it's excursion.

**Sonnie** · **03-08-07, 12:32 AM**

Quote:

kano32 wrote:

I believe he's actually talking about a highpass filter which will taper the lower frequencies which will help the driver not to exceed it's excursion.

In effect it would be subsonic filter of sorts.

**Egil** · **03-08-07, 05:32 AM**

Im thinking about going all out now. And make a 260litres box, tuned to 17hz (similar to Vitod's box-design). So I won't have to worry about a highpass filter then, right?

I guess this qualifies as a LLT design . .?

**Egil** · **03-08-07, 08:30 AM**

Assuming I build a cube that is 71x71x71cm, and use 1" MDF, - I will get around ~287 net litres. Then I have to subtract some volume for bracing (X litres), and the tuning pipe (around 11-12 litres)..Which should do it, I hope

I will probably make some 'donuts' for both ends, using 1 or 2x 1" mdf. It's probably not optimal making this myself, but better than using no flare, I hope

Also: Is there any pro/cons building a cube ?

**vitod** · **03-08-07, 08:49 AM**

You don't have to build a cube. You can build it tall with the same volume. With a taller box, you can tune it lower if you want to 14hz. 6"X28" port.

I modeled for a flared port and not. No difference. So I didn't bother the extra work. It'll sound great regardless.

**Egil** · **03-08-07, 09:02 AM**

Aha..

so as long as the net volume is right, it doesn't matter which shape it has.

For my use, I don't think it is necessary to tune it any lower than 17hz, so I'll probably just go with a cube design, similar to yours

WOAH, things are finally starting to look good

Now I just need to get a hold on some 1" mdf to begin the project !

Should give me the net volume of ~287litres... -bracing and tuning pipe, this should be around 260litres. Can't build a cube 71x71x71 because it wouldn't fit through the door to my living room

**Jerm357** · **03-08-07, 10:51 PM**

Just to let you know I built a 8.5cf ( about 241L )box with a RL-P 15 tuned to 17hz and than changed the tune to 15.45hz and did not notice lower output but did hear better sound quality. You might as well tune it to 15.5hz if you have the room for the port. Heres my build thread...

http://www.hometheatershack.com/foru...ject-pics.html

**Egil** · **03-09-07, 06:19 AM**

Just to clarify, how long does the pipe itself has to be, if Im going to tune it to 15.5hz ?

**Jerm357** · **03-09-07, 12:22 PM**

For 260 L it needs to be 30.46 " Straight Length Port required. Use the Port Length Calculator I gave you earlier in the thread to find out how long it needs to be for a given enclosure. Heres it is again ....http://www.psp-inc.com/

**Egil** · **03-14-07, 09:29 AM**

Ty, Jerm.

Im having problems getting some 25mm MDF (1").. I currently have 3 choices:

1) 19mm MDF (~3/4" - cheapest).. The minimal size recommended.. but will this be rigid enough for my 260l box?
2) 30mm MDF (about double the price as the 19mm) - box will be a bit bigger with this, but that is not a problem.
3) 22mm MDF - but then I have to wait 2-6 weeks.. and I don't think I have the patience to wait that long

Any suggestions ?

Also: It doesn't matter if the port/pipe is horizontal or vertical, right ? (Im considering building the box a bit taller so I can tune it lower).

**SteveCallas** · **03-14-07, 10:48 AM**

The SMS has a pretty steep low end rolloff, so that can act as your highpass. You'll want some flaring for the port opening - what most of us do is use a 3/4" roundover bit where the port meets the MDF to create a DIY flare. Collo's "Flare-It" program will show what effect even minimal flaring has.

The orientation of the port doesn't matter, just avoid any bends and make sure the internal port opening has plenty of clearance, at least 6" in all directions.

**Jerm357** · **03-14-07, 09:47 PM**

All I can tell you is that I just used 3/4" MDF for my 8.5cf and have had no problems. If you look in my build thread I just used 2 pieces of 3/4" for the top and three for the bottom with three horizontal braces and vertical braces an all four walls. Heres a picture, the last picture is the piece I used to get three pieces on the bottom of the sub. I just glued the two pieces together. It allowes the driver to be flush and still have 1.5" for the driver to screw into.

**Egil** · **03-19-07, 10:30 AM**

Looking good, Jerm

I just picked up all the parts (precut) for my box.. 3/4" MDF.
Im not that happy with the cutting..(have to cut 2-3mm from some of the pieces myself, - because I want it to be perfect :P ).

Anyways..

At least I can start building this behemoth now

Will still be a couple of weeks before I receive the woofer, so I got plenty of time , still

**vitod** · **03-19-07, 10:51 AM**

Can't wait for your results!

Remember, If you still want a 17hz tune, 6X24 is enough.

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