RST28F and DC130A Foamcore Homage to LS3/5A

This started as a curiosity for me in this thread on suitable replacement drivers for a small speaker similar to the LS5/3A. I decided to make a small sealed speaker of the same dimensions as the LS3/5A (12in tall x 7.5in wide x 6.5in deep) with a goal to reproduce the typical response that it so famous for - but using modest (inexpensive) and readily availble drivers.

I think the secret (of the typical nonlinear response) lies in the crossover.
 
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The second set has been finished a few days and finally had a chance to take some images. I highly recommend this speaker for its balanced sound and compact size. The sealed design allows for great flexibility in placement. Kudos to X for this little gem.
 

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Very nice work, SignalLost! Beautiful job with the mitered corners and flush pincusion rebate. I know how hard those are to do. I wish manufacturers would stick with round bezels, but I think the shape gives it a unqiue appearance that is less boring than a round.

I finally had some time to do a dry-fit of the drivers and baffle into the box with all screws. So far so goos. I need to solder up some crossovers now.
 
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The Rockville’s are singing! I am using my 10F/RS225 FAST speaker XO PCBs because I was looking for a nicer looking solution than P2P on a plank. I should get a smaller PCB made as this one is overkill. Lots of space. Although that XO PCB fits perfectly on the floor of the speaker.

They sound great and the voicing is exactly what I expected. Balanced and natural.
 

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They can get pretty satisfyingly loud. I place them above my 10F/RS225 TLs which sound big, and these sound surprisingly similar in scale and voicing. They lack the bass of course.

At 84dB 1m and 2.83v that’s 1w, if we go to 64w that’s 6 doublings at 3dB each or 18dB more. 84dB + 18dB = 102dB max.

They really are meant for small rooms or near field monitors - similar to the intent of the LS3/5A. For desktop computer or mixing monitors, they sound great. Very neutral and balanced voice and tone.
 
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Hi xrk,

Great looking enclosures! I would agree with you that they are best for small rooms/nearfield use, in my case they also want big power amp with big reserve of power...

I end up buying Crown XLi800 for them, just great transparent sound form this entry-level crown... I would never imagine that PA Amp can compete with audio grade gear but you never know until you try it for yourself!
 
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do you plan for a 3-way, the "Foamage" with the 8" Dayton TL ?
You mean add a tweeter to the 10F/RS225 TL? No, not a proper 3-way. I have played with adding a dome super tweeter aimed straight up at the ceiling with a 0.47uF cap for ambiance. It was interesting but in the end I went back to a 2-way FAST.

In the meantime, I have been listening to the Rockvilles as near field monitors and they sound fantastic. There is really a lot more bass when they are 2.5ft away from your head. Sometimes they sound clear like good headphones. I have them sitting on EVA foam blocks (yoga stretching blocks) that make excellent monitor stand isolators.

I have powered them with 100w Class AB, 39w Class A, and an IcePower 1200AS2 (new toy I am testing out for a client) and it all sounds great. Of course never taking up to the full power of these amps - typically play around 8w to 15w and that is plenty loud.
 

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Still listening to the Rockville’s and having built 3 sets now, have verified that the choice of drivers and crossovers is solid. The voicing and balance comes out spot on each time. They really do sound exceptional as near field monitors. I compare the sound balance to my open back headphones and putting headphones on or taking them off - sounds about the same. Very nice.
 

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They are very different speakers. The Rockville's are neutral and accurate nearfield "monitors" and have the top end afforded by a dome tweeter. They play all genre's well and accuratey, however lack bass below 90Hz or so. In nearfield (3-4ft) the bass is quite satisfying though - I can listen to them all day and don't really miss the bass normally afforded by my big 8in TL speakers. The 0.53x Karlsonator with PA130-8 has a similar voice, but is not a "monitor" and lacks the higher end reach above 12kHz. I would say the midrange on the PA130-8 sounds a bit more foreward. The bass on both is a toss-up, maybe with mid bass slam going to the Rockville, but ultimate deeper reach going to the Karlsonator with PA130. But that could be the difference in a stiffer wooden cabinet vs a foam core cabinet on the PA130 in a Karlsonator. I actually have them both connected, one on left and one on right for a comparison as I write this. The sensitivity of the PA130 is about 89dB so about 5dB louder.

They both sound great - but different. If you want to use them for casual listening, either works but for mixing or when accurate reproduction of all genre's is important, maybe the Rockville should be considered more suitable. Vocals on the Karlsonator can sound very mesmerizing.

However, Bonjonno really likes the 0.40x TC9FD Karlsonators for studio monitor work.
 
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Another set of Rockville’s is now singing in Long Island, NY! These belong to Vunce who did a super job with the crossover and final cabinet assembly. He reports that they sound great and are now playing with the FH9HVX driven by the Yarra/ACP+ preamp.

Cabinet construction internal detail showing oak battens which are glued to the cabinet with PL Premium at the corners but latex caulking along the lengths for vibration damping. All walls lined with Noico butyl and then covered with eggcrate foam. Weatherstripping foam is used in between the front baffle and the battens to provide an airtight seal and additional vibration damping. The construction with 9mm BB plywood makes for a light but rigid and well damped cabinet.
 

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My 3D model of the woofer pincushion bezel worked out well. Here is a test print to check the fit. This will make CNC of the baffle possible.
I have been using the TDA7293 Xmas Amp by Jhofland to play the Rockville’s over the past couple of days (free open source design). They work very well together.
 

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