Overnight Sensation build

[Paul Carmody]

In my humble opinion the tuning is too high. Not to criticize Paul's design, as I have a great deal of respect for him and his designs, but the 50 Hz tuning creates a substantial peak at 50-55 Hz. IMO a tuning of 38-39 Hz would work better in most rooms (yes, I am aware that measurements were taken outside). Try extending the port to 5" and see if that helps.

I do agree with you. I often intentionally tune my designs "up" just a bit to get a 1-3 dB boost in the low bass. It's just the way I like to listen to music; a lot of DIYers do the opposite, though, and tune low, therefore making the low bass taper off more.

Lengthening the port as you suggest will take out the boost, although I'm not exactly sure it will have that big of an impact on the bass boost he's seeing.

[Paul Carmody]

Measurements taken outside same setup as before. Had to turn the amp off while connecting/disconnecting each woofer so the levels don't match exactly. Crossover was bypassed.
Top b4n, bottom b4n, both b4n's in phase, and with vs without crossover.

That's what has me so concerned. The measurements with and without crossover look way too much alike. Here's what it SHOULD look like, the raw driver in dark blue, the filtered on in lighter blue. (keep in mind that I use gated MLS measurements, so everything below 300 Hz or so is meaningless.)

[Kornbread]

Right side measurements, done in same manner as other measurements. 1) Bottom woofer, 2) Top woofer in red, 3) Both right side woofers in green, 4) Left vs right channel (difference in level is my fault,) nonetheless, both sides measure the same.

What ever I've done ... I'm consistent.

[jhollander]

The wiring looks right. I had a weird problem once where I got a 40 ohm resistor when I should have gotten a 4. I never noticed until I couldn't get anything from a tweeter. Of course the Dayton resistors are known to break the leads as well.

A good way to trouble shoot is to layout and play each circuit (tweeter, woofer) before putting in a box.

[Kornbread]

before putting in a box.

Too late.

[Kornbread]

Somethings bothering me.

There is a decent picture of the internal braces on post #3. Could they be too restrictive? I may be able to get my arm in there with a keyhole saw and open them up.

... and in post #19 you can see the 1/2" carpet padding lining almost all walls, (it's made of all types of foam glued together,) and the open cell foam pads behind the woofers. What affect did this have on volume?

Pulled a woofer, sticker said b4n, 50w, 8ohm. Since measurements were close, I'd assume all are the correct part.

[thekorvers]

I do agree with you. I often intentionally tune my designs "up" just a bit to get a 1-3 dB boost in the low bass. It's just the way I like to listen to music; a lot of DIYers do the opposite, though, and tune low, therefore making the low bass taper off more.

Lengthening the port as you suggest will take out the boost, although I'm not exactly sure it will have that big of an impact on the bass boost he's seeing.

I sometimes dial in a little boost as well and I do agree with you that the amount of boost in the design does not account for what he is seeing here. Something else must be going on. It certainly warrants additional troubleshooting.

[Millstonemike]

A single driver model of the B4N variations designated by PE part number. The 297-429 has 3.2m xmax while the 297-434 has 3.0mm xmax (Xmax graph at 10w)

Also, since the volume is slightly smaller than Paul's original design, you should add 0.7" to the port to get back to 50hz tuning. The 3" length port in the smaller cabinet is increasing the hump more than Paul intended - easy to do with a cut down PVC coupler and some of the original 2" PVC filling the larger coupler cavity.

[thekorvers]

A single driver model of the B4N variations designated by PE part number. The 297-429 has 3.2m xmax while the 297-434 has 3.0mm xmax (Xmax graph at 10w)

There are no B4N variations. The 297-429 is a HiVi B4N and the 297-434 is a HiVi M4N. Two different beasts!

[Paul Carmody]

Somethings bothering me.

There is a decent picture of the internal braces on post #3. Could they be too restrictive?

The result of passages being too restrictive is often seen by the drivers as "aperiodic" box (aka: a leaky box). If that were true, the response would look and sound more like a sealed enclosure than vented.

With that said, at this point, I'd recommend stuffing up the ports with a sock (emulating a sealed box) and seeing how that fares.

... and in post #19 you can see the 1/2" carpet padding lining almost all walls, (it's made of all types of foam glued together,) and the open cell foam pads behind the woofers. What affect did this have on volume?

In my experience, that carpet padding stuff doesn't do much until you layer it to get about 1" thick, or more.

[Millstonemike]

There are no B4N variations. The 297-429 is a HiVi B4N and the 297-434 is a HiVi M4N. Two different beasts!

Your right. Whenever I search PE for B4N, the M4N shows up as well. Did''t notice the "m".

[thekorvers]

Your right. Whenever I search PE for B4N, the M4N shows up as well. Did''t notice the "m".

I figured as much and thought you would not mind if I straightened you out.

[Kornbread]

Wanted to be sure the woofer had a good seal so I used 3/8" high density foam tape where it meets the speaker cabinet. The traces were so close to previous traces it was hard to tell them apart. Guess there were no significant leaks.

Then wadded up a sock and plugged the port; red is with port stuffed.

We've narrowed the possibilities and I'm leaning toward trying to squeeze my hand in there and eliminate some of the brace materiel. Guys ...

[Kornbread]

Was able to open up the bracing to the point there should be no problem with restriction. No crossover. The problem wasn't in the bracing.






This is what happens when adding the crossover to the above.




The port is inaccessible from the inside so I had to improvise. Cut a cereal box and rolled it into a tube, taped, then inserted into the port. Made for a variable port up to an additional 5.5". I'm sure it wasn't completely air tight but it was snug enough to serve the purpose. Red trace is with crossover, purple trace is with crossover and additional 5.5" to port, light blue is no crossover.




For comparison Red is the Overnight, Green is the Linaeum/Faitalpro project. Using the minidsp on the Linaeum/Pro project made it easy to tailor the sound. In doing so I deliberately placed a ~10db hump in the low end response. It simply sounded better, but we're talking about a ~20db hump with the Overnights in the same region. It's just too much.

How do I fix this?

At this time I throw my hands into the air and utter words you don't want your mother to hear.

[bullittstang]

Do you DATS, so you can measure the woofers T/S parameters? Sounds like you might have some not-to-spec woofers. It has happened to me, but they replaced no problem. Sorry if this has been asked/answered before.