Need some thoughts on a large dual 15", dual ported design.

**erikhtb** · **05-18-07, 10:39 AM**

Where would I find a 10" elbow??

**aceinc** · **05-18-07, 11:21 AM**

Actually I was thinking more along the lines that horn and TL designs don't seem to flare their ends. At first I thought it might be because of the large size of the opening, but some TL designs have openings smaller than SD.

How about multiple 6" pipes, I saw 6" elbows at Lowes the other evening.

If you wanted to flare the ends of a large PVC pipe, could you use an old Bowling ball as a form and a hair dryer? Heat the end of the pipe and force onto the bowling ball. Why not go to a bowling alley with your pipe and go into the restroom with a bowling ball and use their hand dryer

Paul

**SteveCallas** · **05-18-07, 12:18 PM**

The opening of a TL is going to be at least as large as the driver, is it not?

Quote:

Where would I find a 10" elbow??

Have you considered mounting the port at 45 degrees?

**erikhtb** · **05-18-07, 07:32 PM**

Instead of going all the way accross the front, I'm thinking about just going the width of the area under the screen, which is 107". I ran a model with the external dimensions of 107"L x 30H x 24"D. 2-1" layers of MDF all the way around. I came up with 31 cf, then took 25% away for an approx volume of 23.25cf.
I would put the two woofers side by side on the right front side of the box, with the ports exiting on the far left front of the box.

23.25 cf

3- 6" ports, elbowed out to the front.

2- RL-p15

tuned to 15.5hz.

1800w

Looks pretty good to me.

**Blaser** · **05-19-07, 09:39 AM**

Quote:

SteveCallas wrote:

The opening of a TL is going to be at least as large as the driver, is it not?

Have you considered mounting the port at 45 degrees?

How would you install it? what about wood cutting?

**erikhtb** · **05-19-07, 10:40 AM**

When they give the "optimal" specs for enclosure volume, does that mean that each woofer you have in the box needs this amount of volume?

For example, if the RL-p18 needs 18cf of volume for a vented sub @ 14hz, would two RL-p18's need 36cf to be optimal?

**vitod** · **05-20-07, 05:44 PM**

Quote:

erikhtb wrote:

When they give the "optimal" specs for enclosure volume, does that mean that each woofer you have in the box needs this amount of volume?

For example, if the RL-p18 needs 18cf of volume for a vented sub @ 14hz, would two RL-p18's need 36cf to be optimal?

Yes.

**erikhtb** · **05-20-07, 07:07 PM**

Thanks!

What do you think of a high power, large (20cf) enclosure housing an array of 4-15" woofers? It models really well with highpass @10hz and around 3200w. I can add an IB in the rear later if it doesn't get it done down low, although I don't see this as being a problem.

I just can't get the large ported designs to come together for my application, and I'm tired of losing sleep over it.

**brucek** · **05-21-07, 01:36 PM**

Quote:

I just can't get the large ported designs to come together for my application

I thought the original ported design with the single 10" port was pretty good.

What was the trouble with that one?

brucek

**erikhtb** · **05-21-07, 02:07 PM**

Making a large ported work in the space I have available for the enclosure given the performance I am looking for is just too advanced for me on my first try at a DIY sub. The biggest problem lies in the fact that I need to elbow the port (or multiple ports) so it exhausts out of the front of my enclosure for one. If I could run it straight out of the enclosure out of either side it would be a different story.

Besides, with what I have been seeing while modeling high wattage 4 x 15" arrays, I don't think it'll make much difference. If it truely sucks I can always do it over better the next time when I have a little more experience. I'll have all the woofers and power I'll ever need to do just about any alignment.

I guess you just have to be ok with it costing twice as much for nearly the same performance as the ported down low, which I am since I will still be far beyond anything I was looking at buying commercially for half the money.

I plan on making the front baffle a nice finished veneer of some sort, then all my black fabric panels that are covering the rest of my screen wall up to it. I think this will look pretty crazy with 4-15"'s flush mounted in a nice walnut or birds eye maple and everything else black fabric. I was going to cover the whole thing with fabric but then it occured to me that this is my theater, and I want to see those bad boys.

**Allen Turner** · **05-23-07, 07:51 PM**

Erik,
I have made numerous Vented Designs and had excellent results with "Square Vents"

Just make sure you have a large enough vent area so that the Air Velocity is low and it will work fine. Almost any Vent shape can work and pehaps round is optimal but I know from expereince that square vents can work well!

With the design you made it looks to me like a folded Square vent will work.
Where as a 10" tube could be difficult and expensive to integrate.

Good Luck!

**Allen Turner** · **05-23-07, 08:24 PM**

Quote:

erikhtb wrote:

Do you guys think it would be better to do slotted ports instead of tubes? It looks like it would certainly be easier.

I was looking at two seperate sub enclosures laying end to end, each with either 2x 15" or 2x 18" towards the middle of the room, with a slotted port on the very end of each box near the outside walls.

I am unsure of the way the slotted ports would need to be constructed, are they actually rectangular ports flush mounted into the box, or are they just rectangular cutouts in the face of the enclosure?

Here is how Slotted Ports work I hope this helps

Win ISD and most good programs can calulate a Round or Square port.
In the case of a square port the its just Width x Height for the opening and then the
length is just that. Its really easy nothing to be afraid of.

Personally I recomend you use 1 RL-p 18 on each side like the box below and vent it as I have shown. Just make sure your vent area is large enough to have a low vent velocity.

Good Luck!

**erikhtb** · **05-23-07, 08:34 PM**

Wow, that does look pretty easy. Thank you for taking the time to draw that out for me..

How do you think a couple of those would sound? It would certainly be less expensive to construct than a 4 x 15" sealed I would think.

**Allen Turner** · **05-23-07, 08:52 PM**

Quote:

erikhtb wrote:

Wow, that does look pretty easy. Thank you for taking the time to draw that out for me..

How do you think a couple of those would sound? It would certainly be less expensive to construct than a 4 x 15" sealed I would think.

Depending on your room size likely 1, 18" wound sound fine, 2 is crazy

The Sound Splinter Drivers are Awesome Vented designs but so-so IB, IMO.
I am currently building a Sono Sub myself and I REALLY like the new 18" in fact mine arrived just today !!

My modeling for the 18 is much better than the 15 for my personal flavor of sub and for the extra $65 it also compresses the air in the room more. With 18" ers you just feel IT more.

As I said my reccomendation is for Two 18 drivers, one on each side, a single Slot vent in each cabinet. Easy to design, easy to build if you do it right.

Oh also a note of experience, make the subwoofer cabinet seperate from the A/V cabinet so you can vibration isolate it or you will be shaking the whole cabinet.

The sub box should be just that a seperate box with in the cabinet, if you can.

**erikhtb** · **05-23-07, 09:11 PM**

I modeled each in a 18cf enclosure @ 14hz. They really look great.

My A/V rack will be going in the rear of the room, so no worries there I think.

What do you think would be sufficient power for these, I was thinking 800-1000 each.

How would you describe the bass quality with this design? Can I get good, solid, hard hitting stuff as well as the really low frequencies. The graphs only tell me so much.

My only concern with is with the bass being too slow and bloated. I have a sunfire and sometimes it seems like I'm hearing the really low stuff slightly behind where it should be, like it takes a half second longer to reach my ears then it should. You especially notice it with music. I think this is the transient response or something, or group delay. I'm not 100% on the terminology.

**Allen Turner** · **05-23-07, 09:33 PM**

Quote:

erikhtb wrote:

What do you think would be sufficient power for these, I was thinking 800-1000 each.

Yes the Berehnger 2500 or Carvin 1800 HD are both good choices, personally I went with the Carvin.

Quote:

erikhtb wrote:

How would you describe the bass quality with this design? Can I get good, solid, hard hitting stuff as well as the really low frequencies. The graphs only tell me so much.

Dont know yet for sure but based on the Qe, Qm, MMs and BL I predict he Sound Splinter drivers will sound "fast" for thier size.

Quote:

erikhtb wrote:

My only concern with is with the bass being too slow and bloated. I have a sunfire and sometimes it seems like I'm hearing the really low stuff slightly behind where it should be, like it takes a half second longer to reach my ears then it should. You especially notice it with music. I think this is the transient response or something, or group delay. I'm not 100% on the terminology.

Yea I was at CES when Bob debuted the Sunfire sub...

I was not impressed other than the volume vs size. "Slow and Bloated" yea thats the sunfire alright, hey you do own it.

But now you are talking "Flavor" of bass and there are lots of good icecreams out there. From what I have seen the Freq Res and Decay plots (aka lack of bloat) for the Sound Splinters are Excellent.

**erikhtb** · **05-23-07, 10:02 PM**

Thank you so much for your help.

I'm going to be starting soon. I was looking at the 2 ohm SS 18". Is this a good choice for that Carvin Amp?

**Allen Turner** · **05-23-07, 11:08 PM**

Quote:

erikhtb wrote:

Thank you so much for your help.

I'm going to be starting soon. I was looking at the 2 ohm SS 18". Is this a good choice for that Carvin Amp?

You are welcome... Yes I think the Carvin would be a great choice

**erikhtb** · **05-24-07, 05:56 PM**

Just ordered 2 RL-p18" and a Carvin 1800HD.. No turning back now...

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