My build of Chris Roemer's "Little White Sub"

[ericJ]

I had the Dayton SD215-88 in a 11" cube, sealed and stuffed. It was being powered by the Dayton 70 watt amp. This was my first crack at a home sub. While it was OK, the T/S parameters for this driver are better in a larger vented enclosure.

After perusing the forum for a while, I decided that the enclosure wasn't optimal for this driver. I liked the looks and specs of Chris Roemer's little white sub using this same driver. Thanks to Chris for the design specs.

1. Port install from rear
2. All glued up except front baffle
3. Flush trim bit in port hole
4. 3/8" roundover on port hole

[ericJ]

A few more pics..

Driver hole cut and driver in. Notice the crushed dust cap courtesy of my daughter...

Last is a comparison of the old box with the new box.

[ericJ]

Front baffle on, glued and "clamped" using a full bucket of drywall mud. Not pictured, but I added a few 10 lb dumbells as well for extra oomph. Hopefully this evening will bring a amp cutout, flush trim the panels and add a roundover to (at least) the front baffle.

Finish will be to gluesize the raw MDF, sand, and a few coats of flat black paint. This thing is going in the corner and won't be seen.

[beemain]

" Notice the crushed dust cap courtesy of my daughter..."

Don't you love how once you have kids you can't have anything nice, well you can until they wakeup from their nap. I like your port installation.

[johnnyrichards]

For the money it isn't a bad driver. I have four sitting in the garage waiting for something to do with them.

[Chris Roemer]

A few more pics..

Driver hole cut and driver in. Notice the crushed dust cap courtesy of my daughter...

Last is a comparison of the old box with the new box.

Sometimes (if you're careful) you can suck a cap out with a vacuum. It helps to have a "wand" with a hole in the side so you can adjust the suction, and just the right diameter.

[ericJ]

Sometimes (if you're careful) you can suck a cap out with a vacuum. It helps to have a "wand" with a hole in the side so you can adjust the suction, and just the right diameter.

Good tip, but it's beyond saving. Not only is it crushed in, but the poly layer has been peeled off as well. I'm planning on grabbing a poly dust cap and some glue next time I place an order through PE.......a grille might be a good idea as well.

[bambino]

" Notice the crushed dust cap courtesy of my daughter..."

Don't you love how once you have kids you can't have anything nice, well you can until they wakeup from their nap. I like your port installation.

Ironic, my 2 year old just tonight decided to pull the grill off my speakers and push in the dust caps, thank goodness for vacume cleaners as these are being sold this month. Guess i should have boxed them up last week like planned, OOPS!

[lostboy77]

Ironic, my 2 year old just tonight decided to pull the grill off my speakers and push in the dust caps, thank goodness for vacume cleaners as these are being sold this month. Guess i should have boxed them up last week like planned, OOPS!

:eek: Remind me not to buy anything from you. ;)

[ericJ]

Update....

Got the amp cutout done. Installing amp in rear panel.....found out that it was going to hit the port. I had to "grind" the port down about 1/8" to get the amp to sit in the box. Still learning............

I went ahead and installed the driver and the amp and brought it inside for a test run. Kids were watching "Despicable me" so I got some explosions and LFE stuff from this movie. I'm running only one 8ohm coil so the amp is giving it about 45 watts. I can notice that it goes lower than it did in the sealed box.

I have heard a few "rattles" coming from the driver, usually during something like an explosion or ultra low effect. I noticed this in the old box too and thought maybe it was due to too small of an enclosure. Could this damaged dust cover affect performance? Could it be that the speaker is reaching a resonant frequency? Anyone else have this issue? My only other guess is that the driver is just reaching it's peak and actually being overdriven?

For reference, the gain is set 50%; amp is running at 8ohms (driver is not currently bridged), LFE and sub levels on receiver are at 0db.

Is this hobby addicting or what? My wife thinks I'm nuts and all I want to do with my spare time is build some proven designs.

[Chris Roemer]

Update....

Got the amp cutout done. Installing amp in rear panel.....found out that it was going to hit the port. I had to "grind" the port down about 1/8" to get the amp to sit in the box. Still learning............

I went ahead and installed the driver and the amp and brought it inside for a test run. Kids were watching "Despicable me" so I got some explosions and LFE stuff from this movie. I'm running only one 8ohm coil so the amp is giving it about 45 watts. I can notice that it goes lower than it did in the sealed box.

I have heard a few "rattles" coming from the driver, usually during something like an explosion or ultra low effect. I noticed this in the old box too and thought maybe it was due to too small of an enclosure. Could this damaged dust cover affect performance? Could it be that the speaker is reaching a resonant frequency? Anyone else have this issue? My only other guess is that the driver is just reaching it's peak and actually being overdriven?

For reference, the gain is set 50%; amp is running at 8ohms (driver is not currently bridged), LFE and sub levels on receiver are at 0db.

Is this hobby addicting or what? My wife thinks I'm nuts and all I want to do with my spare time is build some proven designs.

Yeah, if you look, on my box, the port's on the (upper) right, and my SA25's on the left, so no clearance problems.

You can't really run that driver in that box with only one coil connected, the T/S parms change. Off the top of my head, I THINK the Qts goes high. That would mess with the required box volume, and the F3. The box tuning doesn't change, but it's probably not good for the single coil T/S parms . . .

I looked at some WT3 results that I got on another SD driver. Having the coils in series or parallel gives roughly the same results, but connecting only ONE coil almost doubles the Qes (mine went up about 90%), consequently raising Qts by about 70%, which makes for an ugly +4dB hump near 50Hz, with a very quick drop below that point, rather than a nice controlled rolloff with a 28Hz F3. The Fs and Vas parms don't change whether 1 or 2 coils are powered, but the huge gain in Qts is a killer (in this instance). Also, you lose 3dB in sensitivity. Not thinkin' that's good either.

Not sure I'd really recommend trying to rattle the dishes with HT LFE stuff with this little guy either. If your stroke is reaching 1/2" (1/4" in, 1/4" out, or 6mm Xmax), you're probably bottoming out the driver. It IS really good for filling out the bottom octave with smaller, limited mains, for music, in a small to medium sized room, if you don't get nuts. It's only a $60 sub.

Chris

[ericJ]

Thanks for the info. I'm new enough that I didn't know the T/S parameters change when just running one coil. I will change the wiring over to parallel. I just connected one b/c I was in a rush and didn't have any more crimp on terminals. That should help performance quite a bit.

My guess is that the driver is bottoming out. I turned the gain way down and it seems to prevent the "rattle". I guess I will have to save some money and work on a bigger sub for HT use. My front speakers are all in walls (5.25" Goldwood concert series). Got them on eBay for like $30 a pair and they do fine for what we use them for. I run them in small mode on the receiver.

I do like this driver though. I paid $24 in 2008 and it's been really good for the money.

[Chris Roemer]

Thanks for the info. I'm new enough that I didn't know the T/S parameters change when just running one coil. I will change the wiring over to parallel. I just connected one b/c I was in a rush and didn't have any more crimp on terminals. That should help performance quite a bit.

My guess is that the driver is bottoming out. I turned the gain way down and it seems to prevent the "rattle". I guess I will have to save some money and work on a bigger sub for HT use. My front speakers are all in walls (5.25" Goldwood concert series). Got them on eBay for like $30 a pair and they do fine for what we use them for. I run them in small mode on the receiver.

I do like this driver though. I paid $24 in 2008 and it's been really good for the money.

I've got my "FREQ" knob set at 1:00, and the "GAIN" at 9:00. I AM using the SA25 though. It's in the basement, used with a pair of BR-1 clones in the exercise area. It really fills out the bottom end.

Chris

[ericJ]

I rewired the driver in parallel and reinstalled.

The performance has been noticebly better. I have not experienced the rattle anymore ( I adjusted the gain for movies so it isn't as high).

When you say the gain is at 9:00, does this mean it is only 1/4 of the way up? Mine is set at 12:00 or 1/2 way up.

I keep the freq. knob at the highest setting since the receiver has an LP filter for the LFE. For music, I find that I need to adjust it.

Placement is in the rear corner of the room. The room is really an "area" as it very open. The area measures 12x21 and adjoins the kitchen and dining areas. I did the crawl method and found where the output is best (to me). Luckily, the recliner area provides acceptable sound.

[Chris Roemer]

I rewired the driver in parallel and reinstalled.

The performance has been noticebly better. I have not experienced the rattle anymore ( I adjusted the gain for movies so it isn't as high).

When you say the gain is at 9:00, does this mean it is only 1/4 of the way up? Mine is set at 12:00 or 1/2 way up.

I keep the freq. knob at the highest setting since the receiver has an LP filter for the LFE. For music, I find that I need to adjust it.

Placement is in the rear corner of the room. The room is really an "area" as it very open. The area measures 12x21 and adjoins the kitchen and dining areas. I did the crawl method and found where the output is best (to me). Luckily, the recliner area provides acceptable sound.

In the LR, I'm running 2.1 with 8" "full range" mains. I've got a 12" Quatro/3cf vented SA240, gain is at about 1/2, Fc is as low as the knob goes. I've got an old preamp with 2 pairs of outputs (post volume control), one set to the amp, the other to the SA240 line ins. My double hung windows rattle at 40 Hz (room mode/node), and the sub only goes down to 30. For music, I'll back the gain off.

Downstairs, in front of the treadmill, I've got the LWS wired off the low level speaker wires, with a pair of BR-1 clones (they'll reach 40 strongly) daisy chained off the amp's speaker terms. AFAIK, the SA25 has no in-line caps to roll any lows off going to the speakers. I'm using an old ADVENT Receiver down there. The SA25 isn't being driven by a line input, so it's volume goes up and down wtih the ADVENT's volume. I've got the sub on a table with the CD player (a bad idea I know) and had to turn down the SA's volume to keep the CDs from "skipping", as it makes the table jiggle. Yup, 1/4 is at 9:00.

Chris