Subwoofer build

[Garyf52]

My latest project is a subwoofer. I have mixed feelings about subwoofers because I like them to augment the bass, while being audibly inconspicuous at the same time. In other words, I like to fully hear the bass without it being obvious that the subwoofer is supplying the low frequencies. That is what I'm hoping to achieve with this project.
My first diy speaker was a small subwoofer; the 'Triska' from the PE projects website. It works very well in a small room but I was never able to get the performance that I wanted in the larger space where my AVR setup is. Fortunately, my speakers all have adaquate bass output so it was not a big deal.

Using Sketchup, I drew up some plans since I'm not using a published design.


Driver is Dayton Audio SD315A-88 12" and the amp is the Dayton 100 watt plate amp.

Cabinet volume will be about 2.76 ft^3. It's about 30" tall , 18" wide at the bottom and 16" deep. Construction is 3/4" Russian birch plywood with a double thick baffle. I found Sketchup to be a great help in laying out the trapazoid shape and making a cut list. Well worth the time spent learning the program. One 4x8 sheet of plywood is just enough for the whole cabinet.

Here are some construction pics.


Flat pack of major parts.


First of many dry fits.


View of the interior.

[Garyf52]

I didn't take photos of the rest of the construction, but here are pics of the result.


About as plain as can be. That is as planned.




The faux leather top is not yet glued. It will be flat once I make some adjustments and glue it down.

I'm still tweaking the setup but I'm pretty close to meeting my goals. I lined the interior of the cabinet with damping material in the top half of the cabinet. The 2 lower compartments are unlined.
The sound blends very well with my speakers and is pretty consistant no matter where I am in the room. Here's a pic of the room to give you an idea. This area is open to the kitchen so the room as about double what is shown here.


On some recordings there is a slight boomyness, especially to the bass drum. I'll continue tweaking with a trial and error approach.
I also intend to add some acoustic treatments to the room.

Suggestions are welcome.

[BobEllis]

Nice design.

One thing I've found that helps a sub woofer disappear is a higher order, at least fourth order low pass filter. That won't help if the driver has a lot of high order harmonic distortion, but with a clean driver it works wonders. I ran a JBL 2245H with a second order filter at 60 Hz and it was still easy to locate. Using a standard 80 Hz AVR fourth order low pass it disappeared unless overdriven below port tuning (like the 1812 Overture cannons)

[tcpip]

One thing I've found that helps a sub woofer disappear is a higher order, at least fourth order low pass filter. That won't help if the driver has a lot of high order harmonic distortion, but with a clean driver it works wonders.

Agree 100%. I'd try to apply the low pass at an even lower turnover frequency.

By the way, what's the low-pass being used in this build?

[Garyf52]

Thanks for the tips.

I've played around with the settings a little more. I have the AVR setting for the main speakers at 90Hz, and LPF of LFE also at 90Hz. On the plate amp, the Freq is set a little higher at 110 Hz. I believe that the plate amp uses a fourth order filter. Have no idea what the AVR uses. Volume on the plate amp is only at about 25%.

I'm pretty happy with this setup but I'll continue experimenting. Anyway, the sub is a keeper.

[tcpip]

Try a lower crossover on the plate amp. How does it sound with, say, 60Hz?

With higher frequencies, the sub can be localised. Some dislike this, some don't seem to mind.