The "REPAS" Subwoofer (REference Passive Alignment Subwoofer)

[tomzarbo]

Name: "REPAS" Subwoofer... REference Series Passive Alignment Subwoofer

This project is a dual enclosure subwoofer system that pairs an 8" High Fidelity Reference Series subwoofer with a 10" Reference Series passive radiator in each enclosure.

Design Goals:
My wife and I are good friends with a couple from church with a good, but slightly older home theater setup. I've offered to upgrade their subwoofer system several times over the past few years, and last year they mentioned that they might like to upgrade their subwoofer from an older 12", low-wattage system to something more modern -- rightly surmising that they could find some gains in performance in light of how far subwoofer technology has come in the past 15 years or so.

After some discussion, two things became apparent: First, 20 Hz bass was not necessary; and secondly, whatever I design needed to be on the small side. I suggested two smaller enclosures that could be tucked away... they liked the idea of something small enough to hide, but nice enough to show off a little.

Driver Selection:
Since size was a major factor, the driver I ended up using was the Dayton Audio HF 8" subwoofer along with Dayton Audio's impressive new RS-based 10" passive radiator, which is a perfect aesthetic match for the Reference Series line of subwoofers. I added one washer to the PR which yielded an F3 of around 32 Hz... This combo doesn't need a very large cabinet to perform well.

Enclosure Design:
The enclosure is fairly straight forward. I used 3/4" MDF for the enclosure, adding an additional layer of 1/2" MDF to the front and rear baffles to allow the drivers to be recessed and still have enough material for the mounting screws to 'bite' into. The enclosure volume is around 28 liters.

[tomzarbo]

Enclosure Assembly:
The enclosure was glued together with Gorilla Glue and is fairly easy to put together with clamps. I rounded over the front horizontal corners of the cabinet and the added bottom base-plate with a 1 1/4" round-over to add a little extra flair to the design. I also added a single cross brace of 3" wide 3/4" MDF to the middle of the enclosure to provide resistance to any flexing.
Since my friend wanted a black finish and knowing how difficult it is to achieve a high gloss black paint finish, I decided to cover the cabinets with birch veneer, stain them ebony black, and apply clear polyurethane as a gloss finish for protection.

How it's Powered:
I intended from the start to use one of the new Crown Drivecore series pro-audio amplifiers to power this pair of subwoofers, as opposed to a more common plate-amp scenario. The crossover duties are handled by that device.

Parts used:
* Dayton Audio RSS210HF-4 8" Reference HF Subwoofer Part # 295-456 (2)
* Dayton Audio Model: RSS265-PR 10" Passive Radiator Part # 295-500 (2)
* Crown XLS 1002 DriveCore 2 Power Amplifier Part # 245-507 (1)
* Dayton Audio BPA-38G HD Binding Post Pair Gold Part # 091-1245 (2)
* 1 bag of Polyfill (approx. 12" round blob in each cabinet)

Conclusion:
I was surprised at the 'punchiness' of the bass this project produced... it reminded me of a live performance... possibly due to the way the Crown amp produces power? Not sure there, but you can feel it in your chest. It will dig down low enough for home theater use, but it really excels at reproducing music, and will do so at fairly loud volumes. Having two separate subwoofer enclosures of course allows you to find the best locations for 'even' bass in your listening room, as well as giving you about 6 db more volume overall. The cabinets are small enough to tuck behind a piece of furniture if you want to hide them... or attractive enough to place them front-and-center in your listening room and show them off.

Like I said earlier, my friends didn't want the 20 Hz low bass from these... but add a few washers in the same size box and you would be able to feel more of the LFE on those bass-heavy movies. Just watch it, we're still only dealing with an 8" driver here!

Tips & Tricks:
There are a few things I did that may not be obvious from the pictures.

I used a rotary rasp in a drill to make some clearance in the cabinet for the active drivers to breathe. This was not necessary for the passive radiators as they are more 'open' since there is no magnet on the back to block airflow.

Also, after drilling the driver mounting holes and driving in the intended mounting screws fully in each hole and removing, I saturated each mounting hole with super glue to help 'harden' it up to add strength. I also then applied some bees wax to each mounting screw to aid in insertion and prevent possible snapping of the fastener.

Once the ebony stain was applied to the cabinets I applied a spray-on polyurethane for the first few coats to avoid removing any stain during finishing. I use wipe-on poly most of the time, so wiping a finish on a stained cabinet may have taken some of the color off. This was a great suggestion by Jeff F on the forum that I wouldn't have thought of.

My goal is always to construct each project to the level that it almost becomes a "kit" that just needs to be reassembled after the finish has been applied. You don't want to be engineering things after you've applied your finish to your gorgeous cabinets! Do the engineering work before finishing, test fit each part, and you will keep your enclosure looking great after assembly.

[tomzarbo]

Here's a few more pics, sorry for the lack of flow, I'm trying to ween myself off of Photobucket.

[tomzarbo]

Trying to get more pics on here...

Forgot to mention that I made up some pieces to aid in adhering the veneer to the curved portion of the base. I've tried to get veneer to stick to a roundover like that without doing that and it's difficult, especially using the iron-on method I usually use.

If you look, you can see a slight recess or gap between the two to make cutting the veneer easier when it comes time to remove the sacrificial piece of wood.

[bullittstang]

Great project Tom. As always, very thorough and precise explanation of your build, with plenty of good quality pics. Your friends will be very happy for another 15 years with these. Did you do any in-room measurements? Just wondering how they did once you got them in the room and add in room gain.

[tomzarbo]

Great project Tom. As always, very thorough and precise explanation of your build, with plenty of good quality pics. Your friends will be very happy for another 15 years with these. Did you do any in-room measurements? Just wondering how they did once you got them in the room and add in room gain.

Thanks sir!
No, I didn't do any measurements at this point. I'm actually having a minor issue... it's probably with my HT receiver. It's an 18 yr. old Sony 5.1 and it was on the lower end quality-wise even back then when I bought it. I think it's not putting out enough voltage to the Crown amp to get the subs really pumping. According to WinISD I should be able to breach Xmax with under 150 watts with the new DriveCore2 1002 amp, but it's not getting close. I use a previous generation Crown 1500 with a ART cleanbox to get the level up on my own dual 12" Titanic MK2 subs with no issues... and that same setup powered these fine as well; I could have launched them easily. I'm hoping that my friends HT receiver has more output on the LFE channel or else I may have to send this amp back and spring for the 1502. Not the end of the world, but on paper, it should work fine, but doesn't.

Looks great Tom! I really appreciate your presentation style. The project is quite clear and well detailed without going overboard in the speaker-nerd minutae. I know we all love it, but there's only so much time in the day sometimes!

Keep up the great work!

Thanks man.
Yeah, it's nothing like the MONSTER setup you've got going, but they should like it I hope. I'm trying to not be such a blabberfingers anymore... and the project submission form only wants 800 words anyway, so that helps to keep things concise, since much of this is from that write-up.

TomZ

[Kevin K.]

Very nice! I love your solution for the binding post, never would have thought of that. Maybe it just me but your pictures are coming in huge, I have to open them in another screen to see the whole photo. Are you doing something different?

[tomzarbo]

Very nice! I love your solution for the binding post, never would have thought of that. Maybe it just me but your pictures are coming in huge, I have to open them in another screen to see the whole photo. Are you doing something different?

Thanks man,

Well, I usually use photobucket but this time I just used PE's photo hosting. They're showing up at normal screen size in Firefox and Edge, but I really don't know what I did when I uploaded them so who knows. Thanks for the heads-up. I never would have known.

If others are having issues with the pics too, I can see if I can re-upload them or something. I had issues uploading them at all really, it just stopped taking them. They're not big either, 200-400k each is all. I used to click on a size, but then I'd get two pictures when I only wanted one.

TomZ

[Mandroid]

Thanks sir!
No, I didn't do any measurements at this point. I'm actually having a minor issue... it's probably with my HT receiver. It's an 18 yr. old Sony 5.1 and it was on the lower end quality-wise even back then when I bought it. I think it's not putting out enough voltage to the Crown amp to get the subs really pumping. According to WinISD I should be able to breach Xmax with under 150 watts with the new DriveCore2 1002 amp, but it's not getting close. I use a previous generation Crown 1500 with a ART cleanbox to get the level up on my own dual 12" Titanic MK2 subs with no issues... and that same setup powered these fine as well; I could have launched them easily. I'm hoping that my friends HT receiver has more output on the LFE channel or else I may have to send this amp back and spring for the 1502. Not the end of the world, but on paper, it should work fine, but doesn't.

TomZ

If you haven't already tried, input sensitivity on the xls2 amps can be changed in the on-screen menu. Selectable between 1.4v and .775v.

Pictures are normal on my pc with firefox.

[howard]

Tom, Beautiful sub and very good write up.

[Jeff F.]

Nice Tom, the finish and project look great! I bet they sound great too.

[tomzarbo]

Thanks Howard and Jeff, I appreciate the kind words.

I love the compactness of this setup. The older and more fiddly my back gets, the more I like smaller cabinets. I can lift these with no issues. They do sound like I was hoping they would, at least on my bigger amp.

I wondered if the extra work of applying veneer to the entire cabinet, then staining/applying poly would be worth the extra work to get a black finish on these. It added a lot of time, but I probably would have spent more time overall sanding and buffing the cabinets if I had just painted the raw MDF and tried to get a mirror finish. I guess as long as the new owners are happy, then I will be too.

Mandroid, thanks for the tip. I did go through the menus and I think I have things set up for maximum gain... it would be the .775 volt setting I believe.... the lower input level. I'm REALLY hoping that my friends receiver will put out enough signal to get the amp up close to full power. It should according to the specs. They've got a $1,200 dollar HT receiver that is a few years old, but it's an excellent model. Hopefully it works.

TomZ

[dynamo]

As always Tom, very nice work! I like the use of the crown amp vs plate amp, lots of power for the buck especially with the built in xo.

[tomzarbo]

As always Tom, very nice work! I like the use of the crown amp vs plate amp, lots of power for the buck especially with the built in xo.

Thanks dynamo.

Yeah, these newer Crown amps seem to make pretty good sub amps as long as you don't need the sub 20 Hz. stuff, which I really don't.
The new Drivecore 2 series even look a little nicer being stealthy black and a bit sleeker looking overall. I just need to stick 4 rubber pads on the bottom of the amp case as it doesn't have any from the factory, since they were intended to be rack-mounted.

TomZ

[anunnaki]

Great job on the build Tom! It looks fantastic. Good finish choices.