Dual 8", In-Wall Ported Box

**Mike P.** · **05-01-09, 08:24 AM**

With a 29 hz tuning a 8.5 x 1.5 slot port is 32.5 inches long. With a HPF at 24.3 hz and the boost that goes with it and 500 watts input power the port air speed is 32 m/s at 29 hz, definitely at the limits. I'm not sure how you're coming up with 13m/s.

**hddummy** · **05-01-09, 09:30 AM**

I'm using Unibox right now, but I'll download WinISD and double check. I'm modeling with two drivers at 250W total input power. This is what I get. Of course this doesn't account for frequency response of the amp itself.

**Mike P.** · **05-01-09, 09:36 AM**

I modeled peak air speed with 500 watts input power.

**hddummy** · **05-01-09, 09:38 AM**

yeah...the amp is 500....until you wire two 4ohm drivers in series, which of course drops it to 250, giving 125 to each driver.

**Mike P.** · **05-01-09, 09:40 AM**

Forgot about that ohm thing.

**hddummy** · **05-01-09, 10:23 AM**

so, what do you show for port air speed at 250w? I guess that means the excursions you were showing was based on 500W as well...i can probably boost the low end a little more.

**Mike P.** · **05-01-09, 10:49 AM**

Green is with 250 watts input, HPF at 21.6 hz and 2 db of boost from 25 - 30 hz. Maximum air speed is 25 m/s at 28 hz. Pink is the wrong modeling of 500 watts.

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**hddummy** · **05-01-09, 11:48 PM**

I've been messing around with WinISD and several different combinations of Port Tune and Amp Boost/HPF settings. I think I have settled on a good solution. Thanks for your help and encouragement.

**hddummy** · **05-05-09, 04:32 PM**

I guess nothing is settled until it's built....right? In an effort to reduce port air speed, I've tweaked it more. Box volume 31l, tune to 28Hz, port dims: 1.375 x 8.5. Response changes marginally, port is a few inches longer, air speed drops to 20.5m/s.

**Mike P.** · **05-05-09, 04:57 PM**

Sounds good. Don't forget your camera when you start building.

**hddummy** · **05-05-09, 07:11 PM**

You bet! I hope to start making dust next week.

**hddummy** · **05-19-09, 10:58 PM**

OK..... I've made some progress, so here are some pics.

All the parts cut out:

The eventual home:

Dry fit check:

Port up close:

**Mark Holmes** · **05-21-09, 01:01 PM**

Really nice round over cuts on the corners. You must have a really nice bit.

**DragonArt** · **05-28-09, 12:33 PM**

Very professional-looking work so far!

I also like the design although I would have built a bad@ss rear loaded horn with those drivers (

), but I guess that would be kind of a overkill.

**hddummy** · **05-28-09, 12:45 PM**

Thanks! Yeah, it is a 1 1/4 round over bit, but I only cut it to 1 1/8 depth. I wanted to keep that slight edge on the face instead of driving the radius down flush with the front face. I was out of town this past weekend, so I hadn't made much progress. Also, I only glue and clamp one piece on at a time. A lot of guys will just throw it all together and tack it with nails or screws to hold it while it dries. I should get finished pictures up this weekend.

**hddummy** · **06-01-09, 10:25 PM**

I've made some good progress. At this point, the box is done and installed. It is has yet to be painted, wired and drivers installed. Those should be next week. I also have to build a cloth grill for it.

Last side almost ready to go on:

Box almost complete:

Next week will be the finished shots.

**Jon F** · **06-02-09, 03:26 AM**

Absolutely amazing workmanship. Great job.

**Mark Holmes** · **06-02-09, 08:17 AM**

What are you planning for grille cloth? Something black or will you match the color of the wall?

**hddummy** · **06-02-09, 09:02 AM**

I bought some white grill cloth from parts express.

**evilskillit** · **06-02-09, 07:13 PM**

Lookin pretty good. Kudos.

**hddummy** · **06-03-09, 06:33 AM**

Thanks! A little tip I figured out that I haven't seen before....I used double sided carpet tape to install the sound absorbing foam on the inside of the box. This stuff is super sticky and intended for permanent installation. I found it to me MUCH easier to use than spray on adhesive.

**robbo266317** · **06-03-09, 07:27 AM**

Matt, can you provide more info on the tape please.

**evilskillit** · **06-03-09, 09:29 AM**

Good idea. I bet it is a lot less painful than hot glue too. Especially when trying to work in small enclosures

The carpet tape can be purchased in the flooring department of home depot, just ask anybody there for carpet tape, they'll show you where it is.

**hddummy** · **06-03-09, 11:14 AM**

http://www.homedepot.com/webapp/wcs/...ctId=100645279

This is what I used. Just cut one or several pieces off the roll. Peel back paper on one side and stick it inside the enclosure. Peel the other paper and put your sound absorber in place.

Just make sure you get one that does not require pressure or heat to adhere and you're good to go.

Definately easier than hot glue.

**Ricci** · **06-03-09, 11:46 AM**

Quote:

hddummy wrote:

Thanks! A little tip I figured out that I haven't seen before....I used double sided carpet tape to install the sound absorbing foam on the inside of the box. This stuff is super sticky and intended for permanent installation. I found it to me MUCH easier to use than spray on adhesive.

Good tip. I remember the Tesa tape I used to need at an old job when I was a teen. That stuff could hold a ship together.

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