The SBM3's

[Kevin K.]

SB Micro 3-ways in the works. Too early to say how this will turn out, I'm hopeful it will all come together. The design will be "Active/Passive", passive circuit between the mid and tweet. First attempt will utilize one Ice 50ASX2SE amp per cabinet, one channel feeding the woofer, the other channel feeding the mid/tweet. If I end up needing more power, will explore other options then.

Drivers: SB21 Tweeter, SB12CAC-4 Mid, SB15SFCR39 5x8 woofer
Cabinets: 6.75" Wide, 12.75" Tall, 10.75" Deep

Have been playing around with another small 3-way that utilizes all Peerless drivers, 5.25" SLS woofer, 3.5" SLS mid, 3/4" DX20 tweet. It's still in process and I'll post that in the near future. Unfortunately, during that project, the idea for this arrangement came to mind, and I've sat on this idea for as long as I can, lol. By the numbers, this should be a better speaker then my previous attempt across the board. More bass output, this woofer has an effective piston area equivalent to or exceeding most 7" woofers. The new Ceramic mids have been well received by the DIY community, excellent value for the dollar. Haven't played with the SB21 yet, but again, have heard great things about them.

By the numbers, this woofer almost passes the "Can it be Down-fired" test. I've run the qualification formula found in the PE Technical Resources, it comes in at 5.2% Sag. They suggest staying under 5%, I'll roll the dice and see how it works out over time. Okay, time for some pics.

[Kevin K.]

Cabinet is miter cut. 2" wide tape applied prior to glue up.




Assembly started by installing the braces, followed by gluing and folding a couple of the other panels at a time.




The midrange chamber is made from a 5" PVC coupler split in half. One $6.75 fitting takes care of both cabinets.



Once the PVC was cut to size, it was glued in with JB weld.

[Kevin K.]

A look at the inside of the cabinet with drivers installed. Mid chamber is 1 liter, rest of the cabinet is 6 liters.

[Kevin K.]

For standoffs, I purchased these on Amazon. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

They're typically used to mount signage to a wall. Available in many different sizes and finishes. Only needed part of the assembly, threw away the parts on the right and replaced those with the bolts on the left.



A picture of the stands being installed.



Followed by the installation of the woofer.

[Kevin K.]

The base being attached to the stands by bolts.



I expect these may have a tendency to walk/vibrate from the bass so I incorporated some pads.




Last of the pics for now. Installed a piece of Dacron in the mid chamber.

[stephenmarklay]

Wow. There are some really neat design features and creativity going on there. The ceramic woofers sure are gathering a following… Overall pretty high on the wow factor and I am going to say that looks like it has a lot going for it. I bet it sounds as good as it looks.

[Kevin K.]

Thanks Stephen! On paper, they should turn out nice. We'll see soon enough.

[DaveFred]

Will there be some "slot loading" of the woofer that will lower FS?

[Kevin K.]

Sorry Dave, I'm not following your question?? What do you mean by "slot loading" the woofer??

[Navy Guy]

SB Micro 3-ways in the works. Too early to say how this will turn out, I'm hopeful it will all come together. The design will be "Active/Passive", passive circuit between the mid and tweet. First attempt will utilize one Ice 50ASX2SE amp per cabinet, one channel feeding the woofer, the other channel feeding the mid/tweet. If I end up needing more power, will explore other options then.

Drivers: SB21 Tweeter, SB12CAC-4 Mid, SB15SFCR39 5x8 woofer
Cabinets: 6.75" Wide, 12.75" Tall, 10.75" Deep

Have been playing around with another small 3-way that utilizes all Peerless drivers, 5.25" SLS woofer, 3.5" SLS mid, 3/4" DX20 tweet. It's still in process and I'll post that in the near future. Unfortunately, during that project, the idea for this arrangement came to mind, and I've sat on this idea for as long as I can, lol. By the numbers, this should be a better speaker then my previous attempt across the board. More bass output, this woofer has an effective piston area equivalent to or exceeding most 7" woofers. The new Ceramic mids have been well received by the DIY community, excellent value for the dollar. Haven't played with the SB21 yet, but again, have heard great things about them.

By the numbers, this woofer almost passes the "Can it be Down-fired" test. I've run the qualification formula found in the PE Technical Resources, it comes in at 5.2% Sag. They suggest staying under 5%, I'll roll the dice and see how it works out over time. Okay, time for some pics.

Interesting idea using the PVC pipe like that for the midrange enclosure. I'd never thought about turning it the other way before.

[Kevin K.]

Thanks Kerry! Finding PVC pipe or fittings in the 5" size wasn't easy. Luckily, Home Depot offered the fitting online, just not stocked in stores. They had to have lost money on the deal, it was shipped from California to my store here in Texas, free shipping. I ordered two of them, so perhaps they broke even.

[Wolf]

I've seen a mid-chamber like that before, and it was plagued with reflection issues on the inside. You might want to place a heavy rubber lining on it to prevent internal reflections.

Later,
Wolf

[Kevin K.]

Thanks for the insight Ben. How would I know if the internal reflections are an issue? Would the mid sound muddy?

[Wolf]

Muddy isn't the word. It would almost have a hollow-'ring' to it. It had to do with the drivers being mounted at the Focus of the arc making the chamber, which meant all emitted rearward waves were reflected back through the cone.

Later,
Wolf

[Kevin K.]

Ok, thanks. I'll watch/listen for it and attempt to address it if it's there.

[Kevin K.]

I've seen a mid-chamber like that before, and it was plagued with reflection issues on the inside. You might want to place a heavy rubber lining on it to prevent internal reflections.

Later,
Wolf

Based on Ben's observation of a similar mid-chamber, I'm going to remove the mid and line the PVC with 3/4" 3-layer Sonic Barrier. From there, I'll play around with some other loose materials like Eco-Core or Fiberglass. Thanks for the suggestion Ben.

[ontariomaximus]

Looks like a great project! I am intrigued.

[Kevin K.]

Thanks man!

[Wolf]

You are welcome! I'd hate to hear a ceramic mid sound wrong.
Later,
Wolf

[tomzarbo]

I think what Dave is referring to is the way the woofer is mounted, and the resulting interaction with the base.

If you were to do a DATS sweep of the woofer in the enclosure without the bottom plate attached facing forward as a normal speaker... then do the sweep again of the woofer installed with the base attached on the table, you'd probably find that the Fs would lower at least a few Hz or so due to the mass of the additional 'slug' of air associated with the cone that is 'trapped' between the cabinet, base and nearby table surface.

I've seen this effect with a few of the speakers/subs I've designed. The Tenacious Bass 8, for example has a down-firing TB subwoofer arranged just like this speaker and it's Fs lowered a bit with the base attached.

I doubt it would be enough of a change to alter things much; I don't think I'd notice it if I didn't see the measurement though. In fact, I'm sure I wouldn't. A little more bass never hurt anything, right?

That's a really cool looking speaker sir! Lots of performance packed in a smallish space. Those standoffs are sharp looking. I tried to cheap out making my own once, but those look really sharp.

I bet a half-thickness of 'Ultra-Touch Denim insulation (2" split in half to 1" thick) placed in the mid chamber would do a lot to calm down internal reflections, that stuff has really good sound-absorbing properties in my observation.

This looks like a high-end version of a 'desktop 3-way' but I really like the look of your other, Peerless desktop 3-way too.

TomZ

[Kevin K.]

I think what Dave is referring to is the way the woofer is mounted, and the resulting interaction with the base.

If you were to do a DATS sweep of the woofer in the enclosure without the bottom plate attached facing forward as a normal speaker... then do the sweep again of the woofer installed with the base attached on the table, you'd probably find that the Fs would lower at least a few Hz or so due to the mass of the additional 'slug' of air associated with the cone that is 'trapped' between the cabinet, base and nearby table surface.

I've seen this effect with a few of the speakers/subs I've designed. The Tenacious Bass 8, for example has a down-firing TB subwoofer arranged just like this speaker and it's Fs lowered a bit with the base attached.

I doubt it would be enough of a change to alter things much; I don't think I'd notice it if I didn't see the measurement though. In fact, I'm sure I wouldn't. A little more bass never hurt anything, right?

TomZ

I gotcha now, interesting. Out of curiosity, did you see any changes when comparing "forward" firing to "down" firing when both measurements were taken without the base? Kind of curious if the sag might impact drivers parameters also.