RS-150mt rs28a build

[Scareurpasenger]

Well, I am nearing the last portion of this build that has been on and off for a while. I neglected to post here when I started, but better late than never. Hopefully my slow but steady progress will either inspire or help others feel good about their slow progress!

This is intended to be a matching rear speaker set to a pair of rs180 mtm towers and the recently completed DOS subwoofer. Some of those plans may change a bit as I have a desire for a better 2 channel pair.

The primary goal was to keep these small for surround duty but also have some versatility if I wanted to move the, to another location as primary speakers. Plans change and I fully expect to keep building new speakers. With that in mind, I have designed these to be either sealed or ported via a replaceable back.

This my first set of speakers so there has been some learning along the way. A bit more enclosure modeling, port design and my first crossover assembly.

[Scareurpasenger]

This is the start of the project at roughly 3 years ago! I know this because my youngest daughter was born before this and this was a project that I kicked off with some of that time off.

[technodanvan]

Only three years ago? Pssh, that's nothing. You're basically speedrunning this!

[Scareurpasenger]

Like most projects, this had a detour along the way. I had originally thought these would be my main system's final rear surrounds. The reality set in and I figured
I should design these to be moved elsewhere if I desire. So, the volume size was mainly dictated by the location that they would be used. Sealed represented the smallest size option and it was modeled a bit large after reviewing them in person. I trimmed of a bit of the front edge to the current size. The back is removable and I may experiment to see what I like best. Attached are the unibox results of the modeling for the current size.

Since they started at a specific size, I had to tinker with the port dimensions. Luckily, I have a 3d printer and the design file from Auger for the Harman port.

[Scareurpasenger]

A couple more pictures of the progress. I finished up the crossover boards over the last few weeks. Front baffles have been veneered prior to the holes being cut. The depth isn’t quite enough for the shallow flush trim bit. This also shows where the port will go on the back.

[JonMarsh]

Alright, some great progress there! very nice looking built work, and crossovers, too! Great dado work on the rounded cabinet corners!

[technodanvan]

Those cabinet corners do look really nice!

[Scareurpasenger]

I can't say that the corners were all that difficult. Using the Sommerfeld tools router bits really makes it simple.

[Scareurpasenger]

I finally got more time to work on these today. The intent was to stop working early on Friday to get some project time but there was too much to be done.

I made a couple practice cuts on scrap to make sure the divers fit and were flush. Painters tape was used to protect the walnut veneer I added to the front baffles over the imbedded magnets. I prefer to veneer after but the diver flanges where under 1/8” which is the shallow end of the flush cutting bits.

Tomorrow I will add threaded inserts that I just got in from Rampa and cover the walls with auto jute padding. It has all the characteristics of the shredded jeans but should be easier to work with.

i don’t think it will be in a playable state tomorrow but it is getting pretty close!

[technodanvan]

Looking very professional sir, I believe you may have done this once or twice before!

[JonMarsh]

I finally got more time to work on these today. The intent was to stop working early on Friday to get some project time but there was too much to be done.

I made a couple practice cuts on scrap to make sure the divers fit and were flush. Painters tape was used to protect the walnut veneer I added to the front baffles over the imbedded magnets. I prefer to veneer after but the diver flanges where under 1/8” which is the shallow end of the flush cutting bits.

Tomorrow I will add threaded inserts that I just got in from Rampa and cover the walls with auto jute padding. It has all the characteristics of the shredded jeans but should be easier to work with.

i don’t think it will be in a playable state tomorrow but it is getting pretty close!

This is an exciting stage, and frustrating when external events force delays in working on it...

[Scareurpasenger]

I started focusing on the smaller things I can do during the week. Sounded deadening has been cut for one speaker minus the back. Fiskars powercut scissors are a huge win for this and cutting veneer.

[technodanvan]

Those are quite the shears!

[JonMarsh]

Those Fiskars look like they could be a match for my Milwaukee's, our house standard in the garage and the kitchen!

[Scareurpasenger]

I installed the threaded inserts for the back and drivers last week. 8-32 was a bit large for the drivers which meant m4 was used. It was a good thing I bought a variety of sizes of the Rampa inserts.

[technodanvan]

This looks sooo good man!

[Scareurpasenger]

Making some more progress today. The crossovers are mounted using stainless screws, padding is glued in place via super 77 and I applied the Rubio to the back panels. I wanted to finish them before dropping in the ports, speaker terminals and countersunk washers.

The countersunk washers are something I discovered during the guitar speaker box build. They typically have these washers that self align and give it a professional finish. Similarly, they make some in a shape that looks to be perfect for making them flush with a face. See the picture to give you an idea. M4 of this brand works for 8-32 screws as well.

[Scareurpasenger]

This shows the rough finished result of the countersunk screws. Once tightened they should be very flush with the surface.

[JonMarsh]

I remember those washers from the speaker cabinets I used to build for the band equipment, mostly PA, but also a set of faux Marshall style 4 x 12"!

Nice looking work as usual!

[Heli-Tim]

I'm gonna have to go look at my cab now to see if it uses those washers. lol. I have a JCM900 half stack from my band days. Paired with a Les Paul of course.

[Scareurpasenger]

The hard part is over! The fronts are glued and dominoed in place and the cabinets are veneered. Paper backed walnut veneer glued in place using titebond 2 with the iron on method. This will match the sub once complete. Grills are magnetic and I have a template ready to go for perfect alignment.

How do I make the best out of grills impacting the sound? Do I need to put felt around the inside edges?

[JonMarsh]

Well, if you have the capability, I'd say measure, don't guess. But felt around the inside edges is likely to be a good idea...

[Scareurpasenger]

Sounds good, I will try before and after and take a stab at a proper measurement.

[Scareurpasenger]

Finished them with Rubio monocoat pure 2c today and these are about ready to assemble. Last bit before firing them up is to drill for the binding posts and wire them up. Measurement and grills will be next. I am hoping these will be a temporary improvement over some older Paradigm Titans.

I am very much looking forward to kicking off the next project.

[theSven]

Looking forward to seeing the completed photos with the drivers in. Great looking build thus far along the journey.

[Scareurpasenger]

I completed the assembly late Wednesday and still need to hook them up to play and measure them. Speaker grills are still pending but so far the WAF is high without them.

[theSven]

They turned out really nice. I hope you get lots of time to enjoy listening to them during the fall and winter this year.

[Scareurpasenger]

Hooked them up today and have been working through the receiver to get them dialed in. They need better placement and I need to measure them as well to make sure nothing was missed along the way.

The rs28a tweeters seem great for the price. It is a shame that they no longer make them.

[JonMarsh]

That is so, so true- but then, they were actually made by Usher for PE, not by the normal Dayton operations in Taiwan or China. And it's not the "made by", it's the "designed by", IMO.

For example, in the category of "things that could have been", Steve and I developed a stacked MDF waveguide for the RS28a which he milled to my spec, which gave very promising results.

Here's the 0-15-30 plot...



But in some senses, for actual use, the 15-30-45 plot was even more interesting...




The replacements, either the soft dome or the RST28a, just don't work as well, and seem to have issues with the throat interface as well- for the same test waveguide. Of course, they don't work as well for just a direct tweeter, either.

This is the results in the exact same waveguide used for the RS28a tests, for the RS28F. The RST28a was worse.








The aluminum dome version has bigger issues with its relatively low intrinsic breakup mode and interface to the waveguide throat.

Too bad... a promising possibility cut off.

[Scareurpasenger]

While I made bookshelf speakers the long term intend was not to suffocate them in an actual bookcase! Working on some basic speaker stands out of carbonized bamboo plywood. A sneak peak attached.

The other issue is with most stands they don’t have the ability to adjust in height. I looked long for something suitable from poles used in RV tables but ended up on an ikea special in my storage. A manually adjustable height desk using a set screw. The legs are very solid steel and the range in height is perfect.

[JonMarsh]

Looks like an idea with potential...

[technodanvan]

Where did you source the carbonized ply? I keep thinking I'd like to use some for a project.

[Scareurpasenger]

I lucked out and found some on facebook marketplace. The brand is plyboo.

[technodanvan]

Plyboo is great, I forgot I had a sample of this stuff lying about. I always wanted to try their dimensional lumber too but have been afraid to ask about the cost.

[Scareurpasenger]

Well, I took the last couple days to wrap up the shaping and drilling for the posts and feet. The last step is finish but this is how they turned out.

[theSven]

I'm really digging that color of the bamboo. That's pretty handy to have an adjustable height option too!

[Scareurpasenger]

This is after applying the hardwax finish.

[JonMarsh]

Nice job there! Slow work takes time, but it's usually well worth it!