The Brohaus Center Channel - RS125, Vifa TC6FD, and Vifa OT19 3-way center

[Navy Guy]

My brother asked me to build him some speakers for his birthday/early Christmas present this year. After some going back and forth, he decided he wanted a center channel first. I wanted to stick with a W(TM)W combination to try and avoid off-axis problems and also because I had been wanting to try the new small, full-range Vifa TC drivers. The only thing he really said he wanted were that it stay reasonably thin and that it be painted black. I chose the RS125 as the bass drivers for cost and because I could fit them in a 5.5" tall box using 1/2" MDF. I decided to go with the Vifa OT19 because could cross a lower than the Dayton ND series.

The box is 1/2" MDF all around. The woofer portion comes out to around 13.8L after driver and port displacement, and the mid portion around 1.2L. The mid cavity is fully lined with denim insulation, while the woofer cavity is partially lined. The TC6 and the OT19 are both rear mounted with a 1/2" round over on the front side. Rear mounting the TC6 put it almost in acoustic alignment with the OT19. The offset was only 5-6 mm.



The box is tuned to around 55 Hz with two 2" D x 9" L PE Precision Ports. I started out with 8" long but had some peaky response so I lengthened both ports to 9 inches.

This is my second attempt at doing a high gloss finish and it turned out much better than the last one. I've learned quite a few things sine the first try that help out a lot with this one. This was all done with Rustoleum spray cans, BTW.



My brother is VERY happy with the finish. He just kept commenting that he couldn't believe that it looked nothing like wood and it was so glossy.

Overall, construction went pretty well, although if I did it again, there are a few things I would change. First, the TC6 has a very small frame. I cut my hole at 2 inches but probably should have used 1 15/16 inches. It would have fit a little better this way. Second, I would have probably have tried to go back after the initial measurements and routed back side out of the hole for the TC6 so that it would sit 6mm further forward and the two voice coils would have been aligned.

Measurements, crossover, and listening impressions will be in the next post

[Navy Guy]

Re: The Brohaus Center Channel - RS125, Vifa TC6FD, and Vifa OT19 3-way center

The crossover on this turned out to be approximately second order slopes all around. The woofer is crossed at around 600 Hz, the mid is around 800/3900 Hz, and the tweeter is around 5800 Hz. If you decide to build this, you can adjust the mid level to personal preference by adjusting the resistor in the mid circuit. The mid has a lot of diffraction evident in the response. Some of this is due to the rear mounting on 1/2" mdf, but I think a lot of this is due to the fact that I didn't get the mid perfectly centered in the opening.

Crossover:


The 2uF cap on the tweeter is optional. Measured response is shown without the 2uF cap in place. If you use the cap, the treble will be a flatten out about 2-3 dB in over the last octave. I liked the little bit of tip up in the high end when I tested it on movies though, so if you build these, you can experiment and see which one you like. Impedance dips to just over 5 Ohms minimum at ~175hz, but is much higher over most of the spectrum. I would say this is probably a nominal 7 Ohm design. I used two RS125-4s in series to make sure his HT receiver could handle the load. The phase angle on the impedance is also pretty benign, so it should be fine on any 8 Ohm amplifier.

Response:


Overall, I REALLY like the sound of this speaker. The lumpy response in the midrange just doesn't seem to cause any issues. I listened to it on mono for about a week. The vocals are pinpoint precise with no hint of glare on any tracks that I tested. The sound was just very smooth and effortless sounding. I can only crank it so loud, being in an apartment complex, but hit levels that I would probably personally never go above and I never felt like the speakers were starting to strain. Speakers that I compared to were my Overnight Sensations and the Bowers and Wilkins CM7, which I bought before I got into the DIY stuff. I would happily replace my B&W speakers with a pair of these made into large bookshelfs or small towers. I listened to some music a few days after I sent him his speaker and now I am really disappointed. I need to make myself something to replace my towers now.

One more shot of the gloss (I'm pretty proud of it :D). Unfortunately I forgot to take more pictures before I boxed it up.

[randyohoh]

Re: The Brohaus Center Channel - RS125, Vifa TC6FD, and Vifa OT19 3-way center

The finish looks terrific, looks metallic. Could you post the steps that you took to arrive at that level of gloss?

[spasticteapot]

Re: The Brohaus Center Channel - RS125, Vifa TC6FD, and Vifa OT19 3-way center

I'm curious - why the TC6 and not the TC9?

[Navy Guy]

Re: The Brohaus Center Channel - RS125, Vifa TC6FD, and Vifa OT19 3-way center

I'm curious - why the TC6 and not the TC9?

Strictly space constraints. I would have needed to add another 1" or so in height to the cabinet to fit the TC9. I am going to build one very similar for myself but will be using the larger RS150 and TC9.

[Navy Guy]

Re: The Brohaus Center Channel - RS125, Vifa TC6FD, and Vifa OT19 3-way center

The finish looks terrific, looks metallic. Could you post the steps that you took to arrive at that level of gloss?

I think part of what you are seeing is dust on the surface and/or grain from the cellphone pictures. The paint is standard gloss black Rustoleum out of the spray can.

To get the finish, it was mostly a lot of patience. Basically this is how it went:

Step 1: PrepI first used 3M Bondo to cover all of the corners and fill in any rough spots. Sand you have to sand this down smooth. Once it is sanded, you will probably notice some pinholes in the bondo. This gets filled in with 3M Spot Putty, which is a little softer than bondo but fills in small imperfections better. This gets sanded down and then the box gets checked for imperfections again. If you find any, put more spot putty on and then sand again.

Step 2: Prime
I used the automotive filler primer from Rustoleum. It is a high build primer, and will fill in some small holes. I personally sprayed these in our parking garage at my apartment complex, but the more dust free you can keep everything the better. The way I did this was spray a coat, then wait about 60 seconds to start my second coat, wait 60 seconds, then spray a third coat. Because the rattle cans don't have a very large spray pattern, it takes a bit of time to cover the whole box. You want the paint to be tacky when you start the second (from what I have read) so by the time I was done with the first, I usually only had to wait a minute or so. The high build primer looks a little wierd when it hits MDF. I sprayed too much on my first coats, thinking that it wasn't covering. Just stick to the 3 light coats and you should be fine. After this dried (about 24 hours) I sanded with 200 grit to remove all of the roughness. This first coat left a very rough texture that needed to be knocked down. Once the box is smooth, wipe with a tack cloth and repeat the spray process. When you sand on this coat, the paint should already be smoother to start out. I used a little bit of 200 grit followed by 400 grit wet sanding. You want no texture to be left on the primer when you finish. This is the hard part, because sometimes you sand through and have to redo.

Sorry, I have to stop here for now. I'll finish this tonight or tomorrow morning though.

[Navy Guy]

Re: The Brohaus Center Channel - RS125, Vifa TC6FD, and Vifa OT19 3-way center

Step 3: Paint
I used Rustoleum Black Gloss for the paint application. After leveling the primer, I applied the paint in the same way. Three to four light coats about 60 seconds apart. The paint will definitely take a full 24 hours to harden. After letting it sit for a day, I start with 400 grit wet sanding. The thing you really need to pay attention to (and the thing I messed up the first time I tried this) is that you have to sand until you have a completely flat and uniform surface. There should be no speckling in the paint. Speckling is a low point that has not been hit with the sand paper. If you sand through to the primer on the first coat it is no big deal. It will get covered again on the next coat. Once the surface is uniform, spray again using the same technique. This coat gets sanded the same way as the last. Apply another coat of paint. On the third coat, I started lightly with 400 grit just to knock the paint down a little bit. Then I switched to 800 grit wet sanding. I finished leveling with the 800 grit. Again, you need everything to be flat and all of the speckling to be gone. You can apply more coats if you want to build the surface of the paint thicker. I would just wait to do the 800 until the last coat. If the surface becomes too smooth, the paint will run when you spray it. Beware though, as the paint will build up in your driver cutouts, so if they were tight to begin with, it might be difficult to get your drivers in the recess. Also, while it should be self explanitory, make sure you wipe the surface clean between coats.

Step 4: Clear Coat
The clear coat goes on after the final 800 grit wet sand of the paint. The clear goes on in exactly the same way as the primer and paint coats. Spray, wait 60 seconds, spray, wait 60 seconds, spray. I only did one full coat because I was pressed for time, but I would have liked to have done two full coats to give me a little more surface to work with. The clear needs to dry for 24 hours before sanding as well. I started with 800 grit wet, then moved to 1500 wet, then 2000 grit wet. Again, you are looking for all of the speckling to be gone. If you do more than one coat, only sand with 800 between coats, then spray again.

I'll finish the last bit up tonight.

[Navy Guy]

Re: The Brohaus Center Channel - RS125, Vifa TC6FD, and Vifa OT19 3-way center

Step 5: Polish
Another important point I messed up the first time I tried this is that you have to wait at least one week before attempting to polish. The paint takes a full week to cure, and if you try to polish before that, you might get a hazy look due to the paint sucking up the polish. I used Meguiars Ultimate Finish Compound. This saves a two step rubbing compound/polish that you might have to do with other products. I bought a small, low speed buffer from the automotive section at Walmart when I tried this last time. It was around $20, IIRC. Start by covering the foam pad with the Ultimate Finish Compound completely. Any dry spots might cause issues with the finish. Apply directly to the paint in a back and forth motion, going at a fairly slow pace, until you've covered the entire surface. I went over mine with 4 or 5 passes. Next you need to wipe off the excess polish with a clean microfiber cloth. After this, you should have a pretty high gloss shine.

Step 6: Wax
I waxed my speakers to increase the shine and protect the paint. I have some of the Turtle Wax Black wax for my car, so this is what I used. Any regular white wax should work just fine. I started with a cleaner wax. The polish is a little hard to get all of the residue off and left some streaking. The cleaner wax removed all of this streaking and left a really clean finish. I then used the black wax for two coats. I applied the wax, let it stand for a couple minutes, and then wiped it off. The wax seemed to take away that last little bit of swirl marks. I applied both waxes by hand using microfiber pads and wiped clean using a microfiber cloth. Make sure you don't use the same cloth that you wiped all of the polish off with.


So that is pretty much it. It is fairly straight forward, but again, takes a lot of effort and patience to do all of the hand sanding and get a nice finish. I'm currently in the process of finishing another pair of Choti HT speakers, so I will try and grab some pictures along the way to illustrate what some of this stuff looks like.

[randyohoh]

Re: The Brohaus Center Channel - RS125, Vifa TC6FD, and Vifa OT19 3-way center

Thanks very much for taking the time to write up the finishing process. The Choti looks a lot like my old Energy Take 5 front and rears one of which makes a scratchy sound. The shape of the Bohaus is very distinctive and the finish is wow!

[Navy Guy]

Re: The Brohaus Center Channel - RS125, Vifa TC6FD, and Vifa OT19 3-way center

Thanks very much for taking the time to write up the finishing process. The Choti looks a lot like my old Energy Take 5 front and rears one of which makes a scratchy sound. The shape of the Bohaus is very distinctive and the finish is wow!

Thanks again for the positive comments. I'm just happy that it turned out this well. From all of the reading I did before hand about this type of finishing process, everyone has slightly different steps. It made it difficult to decide on what to do. This process was a little different than the last attempt, but I'm very happy with the overall results and I will stick to it for my next project.