RL-P18 Ported Subwoofer Build - Jan 2009

**Ricci** · **01-21-09, 04:16 PM**

Quote:

ISLAND1000 wrote:

OOps, I forgot. But your port has that thinga magig in it so you can't see all the way to the end of the port . . . . can you? An open 10" port has that "I can hide it in here" quality that impresses me.
But who can forget that beautiful 25 Cu, Ft. Vented cab that Funky Waves constructed for you. That is one of my all time favorite projects. I didn't talk about it much on here cause I was jealous. Still am.

Lol! No need to be jealous with your LMS5400 Phil... I can't see up in my port at all and actually looks like some weird slot port unless you know better.

The design is looking good UKwarrior! The bracing scheme looks fine to me.

**Ukwarrior** · **01-28-09, 01:32 PM**

The enclosure & grill designs have all been finished and exported into .DXF cnc router files. The 18mm and 25mm MDF is arriving tomorrow afternoon; I won't be able to begin cutting until Monday. However, I've come against a problem which is infuriating and frustrating beyond all belief. The front baffle is 635mm wide by 1107mm tall - 25 inches by 45 inches. The router is only capable of cutting to 625mm width. So in short, the complex radius between the front 18mm baffle and the front interior 25mm baffle can't be done. I'm sure there's a way to do it, but it will require a lot of messing about which I really can't afford to do at the moment.
Ed.

**ISLAND1000** · **01-28-09, 03:20 PM**

Ed,
When machines can't do it, men can. Why I'll bet my old uncle Willard could "whittle" those two router cuts to near circle dimension perfection with nothing more than his two hands and a jack knife! Of course it might take him a year or so to complete.

**Ukwarrior** · **02-04-09, 01:56 PM**

Sorry about the lack of updates; I've been waiting for materials; in the meantime I made up the cables and they look quite nice!
The 18mm and 25mm MDF arrived today; I got straight to business on the table saw and cut out all the faces. I've already routed one of the internal braces on the CNC router as a test run and the results are excellent. I'll post pictures once I've got them off of the camera. I'll be working on the enclosure tomorrow from 2:30 until 7:00, which should let me get plenty done!
Ed.

**Ukwarrior** · **02-13-09, 01:47 PM**

Once again, I apologise for the lack of updates; I've been very busy at the moment and have had little time to devote to the project and project log. However, I've made significant headway :

1. All internal bracing has been cnc machined, all edges smoothed with a roundover bit:

2. 8 Inch port flare machined (15 hours of machine time!) to give a flare with an outer diameter of 12 inches!, smoothly cut out of two stacked 25mm mdf sheets:

3. Internal cables soldered to binding posts:

4. Binding post plate recess & bore cnc machined & all parts fitted:

5. Port flare bracket (which holds the port flush against the flare) turned on manual lathe from 15mm plywood:

6. Front Baffles currently being machined (as I type) to correct size (I went with a double 25mm front baffle, giving me a total of an inch of MDF to support the driver):

7. Front Grill CAD files finished, exported as mill files ready to be cut out.

Now, I'd love to show the fruits of my labour so far, but I can't at present because I've mislaid my mini-usb connector. All will be resolved tomorrow, and I'll upload as many pictures as possible then.

The power amplifier has arrived; I chose the TAPCO J2500 Juice series, and to accompany it a Reckhorn B1 Bass management system (A glorified name for a crossover/cutoff filter). I'll be breaking in the driver over the weekend before installing it.

Custom Cables :

Amplifier & Crossover :

Ed.

**atledreier** · **02-13-09, 03:31 PM**

Pics or it didn't happen!

**Ukwarrior** · **02-14-09, 07:12 PM**

Oh it happened!

**ISLAND1000** · **02-14-09, 11:58 PM**

Ed,
That CNC machining stuff really looks nice. The port flare is eye catching. This is one sub I'd like to see and hear.

**Ukwarrior** · **02-26-09, 09:48 AM**

Update 26th February :

1. Flare has been sanded & matched to port dimensions

2. Front baffle (outer) and Front baffle (inner) have been glued together & Port flare mounted appropriately

3. Mounting holes drilled out for driver, hurricane nuts fitted (only had one which stripped - has since been replaced with a working counterpart), driver test mounted.

4. Grill guides fitted & tested

5. Waiting to be assembled!

I will probably do a dry-fit test run on saturday afternoon; if this goes to plan the whole box will be glued up on saturday evening and left to cure for the weekend. I need to recalculate the port length as the dimensions have changed since my first attemtps on winISD.

However, I'm a bit confused about a really basic part of the design :
In order to calculate the port length, you need to know the volume of the enclosure. But the volume of the enclosure is reduced by the addition of the port; although you can account for this and modify calculations accordingly, they won't be exact unless you already know the port length & volume.... so how do you know how long the port should be?

Pics to follow on weekend.

Ed.

**SturmMD** · **02-26-09, 10:59 AM**

Quote:

Ukwarrior wrote:

Update 26th February :
However, I'm a bit confused about a really basic part of the design :
In order to calculate the port length, you need to know the volume of the enclosure. But the volume of the enclosure is reduced by the addition of the port; although you can account for this and modify calculations accordingly, they won't be exact unless you already know the port length & volume.... so how do you know how long the port should be?
Ed.

Just do a few iterations. Calculate volume, find port length, and repeat. After 3 or 4 iterations you should already be under your port construction and volume calculation accuracy.

**ISLAND1000** · **02-26-09, 12:28 PM**

Hah! Leave it to a Londoner to come up with an audiological, "Which came first, the chicken or the egg"? IE: "which comes first the port or the box?".

There IS a formula . . . . Sturm/Gilder that gives the answer but I'm gonna keep it secret.

**Ukwarrior** · **02-27-09, 01:51 PM**

Hah! Leave it to a Texan to withhold a secret formula

Other thoughts I'm having at present :

I did a dry fit today - This thing is HUGE! I knew it would hardly be a unimposing affair, but it looks like a walk in safe. All the dimensions are perfect and I'm hoping assembly will take place tomorrow.

1. I'm using Biscuit Joints and Cascamite (very strong wood glue) for the box structure. I hope this should be sufficient but I'm very open to comments. However, for the internal bracing, I'm tempted to screw through the 18mm external faces to hold it in place. Is this a good idea or will it potentially split/ cause problems/ be a bad idea? Should I use dowel joints instead or perhaps just glue?

2. Is there any need for me to use any acoustic foam or stuffing inside? Will it *really* affect the sound quality, or is this something people dote on but don't understand the physics of?

3. What should I use to seal around the port to avoid potential air leakage? I was thinking of Silicone sealant but it releases acetic acid which may potentially damage the driver - perhaps I can get some neutral cure silicone sealant?

Please feel free to contribute, any input at this crucial stage is greatly appreciated.

Ed.

**ISLAND1000** · **02-27-09, 06:17 PM**

I used glue AND screws BUT the screws were mainly for maintaining alignment during construction and only minimally for added strength. I calculated the screws would help hold up against sudden box dropping or collisions during transportation.
I would think "bisciuts and cascamite glue" would make a . . . . wonderful breakfast. Whaddya drink with that . . . TEA?
Seriously, I'm not familiar with that glue but If it's a white glue it'll do. The biscuits will supplant the screws but if you want to add a couple screws for insurance remember to counter sink them a little. Use the right size screws to avoid splits and always pre-drill the holes.
Stuffing the box to some degree is the norm. It is supposed to reduce internal reflections. With a sealed box it's less important. In a sealed box you can add stuffing to increase the apparent box size. In a ported box that has little effect.
In my opinion with a large ported enclosure I thought adding acoustic damping material made the driver sound tighter, possibly less hangover, or ringing. The audible difference was not very large and I added fiber glass to make myself feel good. I never measured the difference.
The port tube and box panels that intersect the port tube should be a close fit. There should be just enough clearance to add a layer of glue.
Gluing the port tube: lightly rough up the surface of the tube with sandpaper where it will mate with the box panel and use the cascamite glue. Don't seal up the enclosure until you're sure the glue won't let go after drying. I've used four small screws through the wall of the port tube also along with glue. It's not quite as neat but that worked well.

**Owen Bartley** · **03-09-09, 12:35 PM**

Ed... I just whipped through this thread, and I'm very impressed. First of all, I'm yet again jealous of someone who can CNC their subwoofer panels. And that gigantic roundover... wow! 15 hours on the machine!? And finally those cables are beautiful. Very, very nice work. Keep it up.

**Ukwarrior** · **03-09-09, 03:04 PM**

Owen,
Thanks for the kind words - they are greatly appreciated.
I've Assembled the box, using glue, screws and biscuit joints. I've recessed all the screw holes, and have plugged them with maple dowel rods purely for aesthetic reasons. The PVC pipe was re-cut and installed, sealed with silicone and left to cure. I'm waiting for the glue to dry, and once it is, I'll spray it and get some pictures up. It looks brilliant, once the paintjob has been done It will be ready to rock. Acoustic foam was installed on the back wall, and it all looks good! The cables have been tested and are as expected.
I'm sorry about the lack of pictures at the moment - the firewall is preventing me from uploading so I'm not sure when I'll be able to show the fruits of my labour. That's right, it does have a U

Ed.

**Owen Bartley** · **03-10-09, 09:14 AM**

Quote:

Ukwarrior wrote:

That's right, it does have a U
Ed.

Hey, I know how it feels to have "colour" " litre" and "theatre" come up as a spelling mistake all the time on the boards. I do it my way anyway.

**Mike P.** · **03-10-09, 07:18 PM**

Have you found a way around the firewall issue?

**Ukwarrior** · **03-20-09, 05:32 PM**

Gentlemen,
On this historic day, two things have been accomplished :
1) I have the firewall unblocked so that pictures can be posted
2) The SUB IS FINISHED!

There are far too many pictures of the build to post up; I'll show you a select few in roughly chronological order:

Dry Run

Ah, yes, the 'biscuits' which cause so much confusion - I warn that they are not the edible type!

Smoothing the port flare from 240 to 1200 grit

Gluing up the cabinet

Cutting the port perfectly square with an ingenious jig and table saw

A little understated....

Front View - I'm quite happy with the grill!

What it's all hooked up to - the top pair of bookshelves are awaiting some speakers stands and the bottom pair some wall brackets

Port & Driver View

I almost forgot the important bit - It sounds AWESOME!

Thanks a million to everyone who has helped me - the end result is something to be reckoned with.

**Pinhead-227** · **03-20-09, 08:18 PM**

Oh... My... Wow! Now THAT is a subwoofer!!

**Owen Bartley** · **03-23-09, 09:03 AM**

LOL... it's bigger than your couch!!

The grille and the port look great, very nice job. It must be a great addition to the HT.

**ISLAND1000** · **03-23-09, 10:30 AM**

. . . . . it took a while but look at that sucker!!! I'll bet it has NO problem energizing the listening positions on the couch. Excellent work.

**filtor1** · **03-23-09, 11:53 PM**

Great job!

**SteveCallas** · **03-26-09, 11:16 PM**

Niiiiice

**Kleppa** · **05-05-09, 09:01 AM**

I'm very impressed by the build, what are the measures of the box?
I'm actually planning to build a sub using Rl-p 18" and 500 liter box myself, therefore I found this link on a norwegian forum

And how long did the bass port end up?

**tcarcio** · **05-05-09, 09:32 AM**

Great job, It looks fantastic.

Advertisement