SEOS-12 + DNA 360 + Deltalite-II 2512 Build - Page 2

Thanks! I'll definitely let you know if I could use some help.

A couple of little updates.

I finished the bracing and installed the binding posts today for the first box. Normally I would wait until after finishing to install the binding posts, but I need them in there so I can make measurements. To make sure I didn't have any light areas showing up, I just used a sharpie to black out the area under the binding posts before knocking them in.

The binding posts are in a little recess made by cutting out a hole, rounding over the edge, and gluing in some more MDF on the inside. I used Gorilla Glue to make sure I got a good seal, and I'll clean up the edges with Bondo before painting.

Whew, it's been a while! I finally have an update, though. I got the chance this weekend to measure the drivers in the box so that I could get started working on the crossover. After acquiring the measurement equipment I needed, I got some guidance from bwaslo, and tuxedocivic on what measurements to take, and how to do it. They were a huge help, and I'm in their debt!

For my setup, I'm using my laptop along with a Tascam-US 122 mkII and a Dayton EMM-6 microphone. I took everything outside to a pool area that overlooks a field and a small lake, which should have been plenty of room to properly measure. I set the speaker atop a ladder and got to work.





First I got everything set up with the correct levels in REW, and made sure not to change any of the input or output settings on the Tascam, or the volume on the amp until I was done testing everything.

For the measurements, first I took a measurement of just the SEOS/DNA360, then just the 2512, then both in parallel. This is a set of measurements was taken without moving the speaker, the microphone, or changing any settings, and is used to set up the acoustic offset of the drivers as described here: https://www.box.com/shared/ouxjjsx0m8bs00cil5iq

Next, I took measurements of the waveguide and the woofer individually, and directly on axis for each one. I also measured each driver about 22 degrees off axis horizontally to simulate toe in, as per bwaslo's recommendation.

Here are the measurements for the acoustic offset:



These are the measurements from tweeter level:



and these are the measurements from woofer level:

It's to get the speaker as far away from any potential reflecting surfaces as possible. If the speaker was on its back, the reflection from the ground would come to the microphone very close in time to the direct signal.

Since measuring I've gotten to work on the crossover with a ton of help from tuxedocivic, who kindly offered to gate the frequency response files and determine the acoustic offset to get me started. When determining the acoustic offset, we found that it was possible to match the shape of the curve from the parallel driver measurement, but that it was a couple dBs down from the summed response in PCD due to the individual driver measurements. Tuxedocivic suggested that it might be because the amp wasn't able to output enough current into the low impedance from the drivers in parallel.

Here's what the offset test looks like (the grey is the actual measured summed response, and the black is PCD's summed response based on the individual measurements):


To test that theory tuxedocivic and I put in Bwaslo's crossover design as a reference point to see what was going on. With the z offset entered in PCD, there was a huge dip right around the crossover frequency that we knew wasn't from the crossover design, so tuxedocivic removed the offset, and the response was flat like it should be. (Just as a note, my measurements aren't the greatest, so I don't think it properly represents Bwaslo's crossover design. This was just used as a test to see if the offset was usable.)

Bwaslo's crossover with .06 z offset:


Bwaslo's crossover without z offset:


So that leaves the question of whether or not that dip actually exists in the system, or if it might be a result of not having enough amplifier for the measurements. Without knowing the answer, however, I just went ahead and played around in PCD to make a couple crossovers-- one taking the z offset into account, and one not.

Here are the results of my first crack at it:

Accounting for .06m z offset:


No z offset:


After showing these to tuxedocivic he pointed out that the one accounting for the acoustic offset definitely isn't a good option. Since the summed response is lower than the tweeter level near the crossover, just going slightly off axis can remove the phase cancellation in that area, and will result in a big ugly peak where it used to be flat. The one without the z offset, however, looks like it could work out, and it's actually a much simpler (and cheaper) crossover.

I've still got a lot of learning to do when it comes to crossover design, but I'll be putting together a mockup of the "no z offset" crossover to test. If everything goes right, and the z offset isn't actually that pronounced, it should look pretty good, and I'll probably go ahead with that design.

(Also, ignore anything below about 250Hz in these graphs)
Edited by Scott C. - 12/10/12 at 11:34am

Thanks! I used a 2 1/2" hole saw bit. A router might be the easier way to go, though. It took about 5-10 minutes on the drill press having to clean out the MDF dust every couple seconds.

Oh, and another tip. On the first one I used screws to clamp down the piece on the inside of the cabinet for the recess, but I think it warped it, so I didn't get a good seal with regular wood glue (I used gorilla glue which leaked out when it expanded and was a pain to clean up). I would suggest just using something heavy to weigh down the piece or a clamp if you can fit it-- that's what I did for the next two and it worked great.

Actually scratch that. The first one was about 2 3/4" and no problems wiring it up. The others were 2 1/2" because I moved to a different workspace and didn't have access to a larger hole saw bit. They'll be perfectly fine once I put a roundover on them, though.

If you're worried about it, I'd go with 2 3/4", though. The roundover makes a big difference with whichever size you use.

Haha, most likely, but I saw this done on another build a while ago and liked how it looked, so I thought I'd try it.

Today I started the second round of my least favorite process: paint prep. Here's one of the cabs on its second round of Bondo. Hopefully this should do it, but I guess I'll find out for sure when I hit it with some primer.

Got to work doing some more filling and sanding. I managed to finish all of the bondo work on one of the cabinets before the weather stopped cooperating and I had to move inside.

I started working on the bracing in the meantime, and finished that up for all the cabinets. Now all that's left is finishing up the filling/painting and then lining the cabinets until I start back up on the electronics.

Cutting the bracing


Finished braces


Sanding down some bondo


Bracing installed

Definitely not the best method, but I just loaded up the ends of the bracing with glue, situated one end where I wanted, and tapped the other end level with a mallet, then I spread a little glue around the edges just for some extra security. The woofer cutout was large enough for me to fit the pieces through it. I cut all the braces slightly large so they could hold themselves in place.

The car is my dad's. It's a Morgan +8. I forget what year.

More updates! Finished all the filling today. It was a pain, but well worth the effort. Bondo is truly a great material. It covered up even some of my pretty bad router mishaps no problem with just a few applications, and sanded flush with little trouble.

Got started priming today. I decided to try my luck without sealing the edges with mixed results. They definitely soak up paint like crazy, but I think once the first coat of primer dries that'll be seal it up well enough to make an easy second coat.

Well I just started the painting, and all that prep work really paid off. The paint went on nice and easy, and covered with minimal effort.

I've been using the same method that Java did for his painting, and I had a question for everyone about using a roller. What's the best way to minimize the roller texture when you're painting? No matter what I do I seem to still get that kind of orange peel look from the foam roller. Since it's kinda cold over here (but not too bad) I'm hoping the extra drying time will help the paint settle out.

Also, should I go ahead and sand between the topcoats too? What grit should I use? I went with 220 for the primer.

(Forgot my camera, so no pics for a little while)