Thinking similiar to Statement/Khanspires but ...

[Kornbread]

After some research it seems everything from sheetrock mud to shellac has been used to seal, or prep mdf for primer. Made a trip to the local hardware store and returned with a quart of Zinsser BIN, $15. This stuff was pretty easy to work with. Both speakers were up on the saw horses. I'd paint the up side of one speaker, then proceed to the up side of the next speaker, by the time the second speaker was coated, the first speaker was dry enough to rotate to the next side. The stuff dries quick, feels thick, and the fumes weren't too bad. Did a light hand sanding after the first coat, then coated a second time. I would have gotten the orbital after them, but it's raining again, and I have no dust removal system in my small 'shed'. It looks like it'll need a couple more coats to fill the end grain, especially the bases where there are 4 stacked layers of 3/4".

Has anyone had any problems with body filler or auto body paint/primer when using BIN?

davidroberts, I had already left for the hardware store before reading your post, or I'd likely came home with shellac. ... about the glue/water mix, I always worry about water and mdf. I know it's been proven many times here, but I still worry, plus some said it was difficult to sand.

Now, how do I get rid of the seems? body filler?

ani_101, Looks like you're from Minnesota. Hopefully, one of these days, I'll be able to join jhollander, and his crew on a pilgrimage to a meet nearer you.

Guys, I appreciate the replies.

There's another 4 channel chip amp (tk2050), power supply, minidsp, and binding posts on the way.

[ani_101]

No worries, there are plenty of raw MDF speakers with glue runs down the side, mine included... So if you can get them to a meet, it is always good

[davidroberts]

The Zinsser Bin is actually just shellac that is pigmented.You can use body filler to hide the seams. I have had better results with glazing putty.

[jhollander]

The Zinsser Bin is actually just shellac that is pigmented.

+1 in the Bin shellac based, water based not good imo

[Kornbread]

The neighbor helped schlep one tower upstairs.

How should I take measurements?

Normally, I take the speaker to the far side of the patio, and measure from 1 meter on tweeter axis. These are too big to move and I don't know if 1 meter is enough time to allow for all the drivers to integrate. Would it be best to place the mic next to each driver and measure? What about the port that's located on the bottom/center of the cabinet, how would I measure it? Should measurements be taken at the normal listening position?

Using REW and a PE usb mic.

[jhollander]

1 meter is good. You just really need to see the baffle effect. It's best to be as far away from other walls and furniture, so out in the middle of the room is my prefered location. You should not need the port for x-o work. You will need the near field and far field. Far field should be gated before the first reflection. Near field is not gated. Take some time to read up on Jeff B's measurement white paper if you haven't done that recently.

[Kornbread]

After a couple hours with the minidsp. Taken @ 1 meter, minidsp, all crossovers lr24. Didn't take much hammering. I'm guessing the low end is an effect of mic position and room?

jhollander, just now seen the post, guess it's time to do some reading. Is this the paper you were referring to? https://app.box.com/s/fefis558wna1d6pd07r3




What can I do with the impulse?



And this seems high, but my testing levels were fairly low. comments.....

[Kornbread]

Haven't had much time lately, but finally got around to stuffing the mid enclosure with denim, added a layer to the front panel of the bottom woofer, which was bare, and to the top panel of the top woofer. From what I could find, denim and mineral wool have nearly the same absorption properties and prices are also comparable. http://www.soundproofingtips.com/sou...ng-insulation/ Went with denim.

It will take some time before I understand Bagby's paper on how to take accurate measurements, but I 'think' the midrange sounds a bit muffled, but the measurements are nearly identical. Red is w/denim.



The upper midrange/lower treble sounds hot, but my probably inaccurate measurements show it's fine (REW freq. sweep, [email protected], on tweeter). Could this broad area of energy in the upper mid/lower treble be contributing to that?




What's all this hash mean, if anything? It didn't change after adding the denim insulation.

[filmslayer]

i looked real quick and didn't see , what tweet did you go with ?

[Kornbread]

i looked real quick and didn't see , what tweet did you go with ?

xt25tg30-04, had a new pair laying around.

Distortion decreased.

Before,



and after.

[donradick]

I don't know what app you are using to measure, but try to change the vertical scale for the distortion measurements.
You want to focus on -40 to -60 dB down from your main frequency response line.
I think your distortion is OK, but it's a little hard to read.

And if you measure at too low of SPL, you will pick up room noise that messes with things.
Shoot for 80-85 dB on axis at 1 meter level. That's quite loud, but it works better than a low level.

[rpb]

If you are listening to the speakers near a wall, try increasing the mid, and tweeter level about 3 dB.

[Wolf]

I find that measuring HD higher at 90-95dB at a meter is better than lower. This offsets the noise floor substantially, but not all drivers can do that level in applied design.

Later,
Wolf

[filmslayer]

I don't know what app you are using to measure, but try to change the vertical scale for the distortion measurements.
You want to focus on -40 to -60 dB down from your main frequency response line.
I think your distortion is OK, but it's a little hard to read.

And if you measure at too low of SPL, you will pick up room noise that messes with things.
Shoot for 80-85 dB on axis at 1 meter level. That's quite loud, but it works better than a low level.

i agree ... all my work with the RS family shows the paper cones to be in the -50 to -55 db 3rd HD . the aluminum versions just slightly better at -60 .

[---k---]

Your impulse response definitely doesn't look good. I'm guessing this is related to measurement gating. Bad measurements makes everything difficult.

I'd be interested in seeing the individual drivers frequency response before/after crossover.

Did you unibox the Paper drivers box sizes? I never have, so don't know if the paper need bigger boxes. Your boxes look so darn similar to mine, I don't know if you built differently from the original to accommodate the paper versions.

It be interesting to see off axis response and a overall power response to better understand the treble hot issue. Toeing in or out or room may alter your opinion.