8" sub project: TB W8-1363SB with CSS APR 10

[jbruner]

This is the build thread for a small subwoofer using the new CSS APR 10 adjustable passive radiator with the mighty little Tang Band W8-1363SB neo 8" driver.

[Edit: I originally planned to use a Bash300 plate amp, but the boost level is not appropriate. You could still use the Bash300 with some simple boost mods. Luckily, I have a Klipsch 200 watt BASH amp that is suitable.]



Thanks to Jeff Bagby for graciously supplying the APR 10 and an excellent comprehensive woofer design program. Not only that, he ran a full simulation for the project. Here's Jeff explaining the program.



Notice the tiny 18 liter box volume?! Also of note, this program fully models the plate amp's response curve too.



Not bad for a small box! I can't wait to try it!

I cut the panels tonight. I don't have a table saw, so I used the tedious clamped-guide method with a circular saw. I used 1" particle board because it was on hand. My box is a 12.5" cube. If you use 3/4" MDF, it will be 12" external and can be built from a 2' by 4' handi panel. Stay tuned ...

P.S. Here's the PR close-up.

[rene]

I have been really wanting to do a passive sub, I was going to use AE passives, but since I can get these locally (a short drive away from me) it's even more tempting. let me know how these work out for you.

My ONLY gripe about these passives is the way the mass is added, and that's purely for the 100% cosmetic reason. What can I say, I was a cabinet maker before I started this hobby, Looks are always super high on my list... maybe I'm just a snob *8)

Rene

[jbruner]

Some progress:


Not enough clamps! I ground the stops on some 12" clamps to get them to 12.5".

I think I will surface mount the woofer and recess the PR on the back. The center of the APR 10 actually sticks out past the surround, and at full throw would stick out almost 1-1/2" if surface mounted. I may recess it just enough to make a 1" thick grille cover it.

My ONLY gripe about these passives is the way the mass is added, and that's purely for the 100% cosmetic reason. What can I say, I was a cabinet maker before I started this hobby, Looks are always super high on my list... maybe I'm just a snob *8)

Rene

Yeah, My first thought was that I need to fabricate a better looking post cap. I also don't like the rubber trim ring.

[Jeff B.]

Some progress:


Not enough clamps! I ground the stops on some 12" clamps to get them to 12.5".

I think I will surface mount the woofer and recess the PR on the back. The center of the APR 10 actually sticks out past the surround, and at full throw would stick out almost 1-1/2" if surface mounted. I may recess it just enough to make a 1" thick grille cover it.



Yeah, My first thought was that I need to fabricate a better looking post cap. I also don't like the rubber trim ring.

I actually think the passive looks better with the cap left off and you see the weights and wingnut. Then you get a feel for what it's doing. This is just my opinion though, I am sure others would like it with the cap on.
Jeff

[jbruner]

I have edited my first post to reflect some changes in the design. The original sim was for the BASH300 amp, but we inadvertently simmed the boost from the BASH500. The 300 doesn't have as much subsonic filtering due to the shallower boost profile. This Klipsch amp is made by Bash and has the correct boost (same as BASH500). Now I'm glad I left the amp out of the box!
(on edit: buyer beware- this Klipsch amp failed early and I know someone who has 2 of them that also died in less than 1 month)


I have run the sub a little, but I will save listening impressions for when I have more time. For now I will say that it does handle Saturn rocket launches! Time to back up and do some box finishing.



Next I am going to line the box with carpet padding to see if it reduces the mechanical noise from the Tang Band. I'm not sure what is making the noise, but I think maybe it's the voice coil venting holes in the cone.

I put some duct seal on the APR's center cap to try to visualize possible cap shapes.

[mrAwesome]

Very interested in further impressions. Have something very similar in my final 2 for building this spring.

[Jeff B.]

I have edited my first post to reflect some changes in the design. The original sim was for the BASH300 amp, but we inadvertently simmed the boost from the BASH500. The 300 doesn't have as much subsonic filtering due to the shallower boost profile. This Klipsch amp is made by Bash and has the correct boost (same as BASH500). Now I'm glad I left the amp out of the box!



I have run the sub a little, but I will save listening impressions for when I have more time. For now I will say that it does handle Saturn rocket launches! Time to back up and do some box finishing.



Next I am going to line the box with carpet padding to see if it reduces the mechanical noise from the Tang Band. I'm not sure what is making the noise, but I think maybe it's the voice coil venting holes in the cone.

I put some duct seal on the APR's center cap to try to visualize possible cap shapes.

Josh is being kind with the "we" part. It was me who incorrectly modeled the boost circuit on the Bass300. All in all, it looks like a nice little sub he has going there.

Interesting mods the passive radiator, Josh. I look forward to the final shots.

Jeff B.

[jbruner]

The subwoofer is built, but not finished. I did a simple 4-corner 5/8" roundover to maximize my finish options. This makes vinyl application easy, but the box needs to be prepped almost as good as if you were painting it. The edges need to be perfect, and primer is a good idea. I have never done veneer, but this box would be a good place to start. Since I filled and primed it, paint is also an option. I used diluted white glue to seal the edges of the particle board. I use a large file to ensure that the sides remain flat vs. sanding which can leave dips near the edges. Then I smoothed with drywall compound, sanded and applied some flat house paint as a first primer. I'll fill more later and use spray primer for the final finish if I use vinyl. I'll wait and see what my final application is before finishing. I would have liked to do an even larger roundover if I had a bit available. A 1" roundover would probably make the box look even smaller.



During sine wave testing I saw that the box moved a lot at low frequencies. This calls for spikes. I decided to do them the cheap way. I drilled and tapped the box for 5/16" bolts.



Later I will chuck the bolts into a drill and grind the heads into points by spinning them against my grinder. I can seal the threads in the box with diluted glue. I was kinda surprised how much the box danced, but then I realized that the passive radiator weighs more than a pound! I can see why it would be a good idea to have two PR's on opposite sides for force cancellation.

I lined the inside of the box with 1/2" carpet padding, which does kill some of the internal woofer noise. I'd like to put a plug in here for PE's speaker gasket tape. As cheap as I am, I really think it is a good value. I usually apply it to the driver, and it lasts through multiple installations. I make it go farther by cutting it in thinner strips for most applications.

[jbruner]

The cheapie spikes are done, and they made the box much more stable.



Jamb nuts can be added if they get loose. Some clear varnish will keep the ends from rusting.


I chucked the first one into the drill, but that damaged the threads a little. So I used two nuts and a nut driver to turn the bolt head steadily against the grinder. The paper towel keeps the bolt tight in the socket.

[Jeff B.]

The cheapie spikes are done, and they made the box much more stable.



Jamb nuts can be added if they get loose. Some clear varnish will keep the ends from rusting.


I chucked the first one into the drill, but that damaged the threads a little. So I used two nuts and a nut driver to turn the bolt head steadily against the grinder. The paper towel keeps the bolt tight in the socket.

Cool idea, Josh

[DDF]

Cool idea, Josh

FYI, for cheap speaker spikes, consider threaded studs for ice racing tires, teh type of studs that thread into t-nits. Canada's latest contribution to the world of audio!

[jbruner]

I have never used passive radiators before, but I think I really like them. The implementation and tuning is ridiculously easy, especially if you have Jeff's new woofer program. Nothing to be scared of at all. With the CSS APR, you can adjust it's 45 gram weights from the front and never have to remove the unit. You can check your tuning frequency with a sine wave generator (I use the WinISD program) or test tone CD. I use two easy methods, visual or impedance. Visually, the tuning frequency is where the driver's cone moves the least and the PR moves the most. Or the frequency where the sub shows the lowest impedance. If you are using a multimeter, set it to AC amperage. The tuning frequency is the frequency that has the highest current reading.

With this kind of small box design, a passive radiator is really the only option. A 3" diameter port would need to be 5 FEET long!

When I first got it, I had some concerns about the build quality of the CSS APR10. Now, this thing has a sturdy cone, stiff suspension, and thick surround. What worried me was the slightly crooked cone and tube alignment and the fact that the center ring of the spider inverted before reaching xmax. I knew this was not a practical problem for my application, but I contacted Bob Reimer at CSS and told him all about it. He addressed all of my concerns and even sent me a new unit. He really went out of his way to make sure I was taken care of. When I noticed similar behavior in the new unit, he sent the response below from Dan Wiggins of ADI (Acoustic Development International). Apparently, progressive spiders are supposed to invert! In any case, I'm impressed with his commitment to customer service and to the DIY community.

PR response:

Spiders rolls WILL START UNROLLING at 40-50% of the rated excursion – that’s how they are designed to work. The rolls begin slowly opening, and that can happen with a small “pop”; however, the audibility of the pop is greatly masked by the acoustic output of the cone.


With progressive spiders, the inner rolls begin unrolling first; they have the smallest area of all the rolls by virtue of the their smallest diameter (across the spider) and shortest roll height. They tend to release first, if the cloth and treatment are consistent. The force of a spider or surround roll or axial spring is the stiffness of the material times the area of the roll. Assuming the same material for all rolls (which is a fair assumption for a spider or surround), the weakest/softest part is the part with the least amount of surface area. Meaning the part with the smallest diameter (area is pi times radius squared). That means the inner rolls WILL release and in fact SHOULD RELEASE before any others.


The suspension used for a PR is radically different than that for a driver. You are willing to use an overly-stiff spider, meaning the rolls will pop a bit earlier than a driver, but that is because the moving mass supported is an order of magnitude higher. I haven’t seen a driver with a Mms of even 600 grams, let alone 1400 grams! The spider does a different job with a PR than with a driver, because the job needed is different. Not just restoring force, but also massive weight support.


Given these two, you do not worry about centering of the spider as much with a PR, nor the absolute centering of the suspension; in fact, it’s nearly impossible to guarantee perfect position (vertically and laterally) with a PR as compared to a driver because you have no pole to center the two! But that’s not an issue for a PR; if it rocks a bit, that does not matter – there is nothing to scrape and rub and buzz. It’s first goal should be to handle as much weight and stroke as possible; rocking is a very low concern for a PR.


Dan

[jbruner]

Very interested in further impressions. Have something very similar in my final 2 for building this spring.

The sound quality is not as good as I would want for music listening. The Tang Band always sounds a little muddy. Maybe this sub is best left in the car. I haven't tried in in HT yet.

It's not boomy or peaky, and the low end extension is pretty decent. 20 hz and down is noticeably missing, but that is because of the subsonic filtering. With this boost/filter profile, the sub can take anything you throw at it. Dinosaur footsteps, Telarc's cannons, or Saturn rocket launches can be played at full volume without worry of overexcursion.

I was pretty disappointed by the lack of clarity. I wanted to use it up to 100 Hz, but found it more tolerable below 80 Hz (60 was a little better).

The TB doesn't really compare to the transparent bass I get from some of the other subs in the room (RS225, RSS315, Monitor 10), so I'm having a hard time finding an application where I can enjoy this one.

[HareBrained]

Is the driver broken-in? That will be an issue if not. Also, TB seems to provide "unique" specs (rarely repeatable). You might want to have the driver measured.

[jbruner]

Is the driver broken-in? That will be an issue if not. Also, TB seems to provide "unique" specs (rarely repeatable). You might want to have the driver measured.

The woofer is broken in well. There is nothing wrong with the woofer or the box alignment. In fact, the sound compares favorably to others like the Titanic or Quatro series. But that's just not good enough for me. I put off commenting on the sound for a couple weeks trying to find a way to like this sub. No one wants to say their sub is just so-so, but why not be honest. If I had never heard better subs, I'd probably be happy. Even my wife complains that she used to be able to listen to anything, but now even a bad recording on the radio bothers her. To each his own.

I may not like it for music, but I'll eventually find the right app for this sub. It sims pretty well for car use with a 25Hz subsonic filter, no boost, and 400g on the passive- about 300w power handling. Or maybe HT is the way to go. I'm not giving up on it yet.

I plan on a head-to-head comparison with a Quatro 8 in the near future. It will use the same passive radiator, but the enclosure will be a touch bigger.

[jbruner]

I thought this sub would best the Quatro 8, but I was surprised. In 0.9 ft. with the same APR10 tuned to the same 22hz, the Quatro sounded better!

I wonder if this could be due to the fact that the larger enclosure requires less added PR mass to reach the same tuning. If so, could someone explain why less mass sounds better?

So, to be fair, I removed the Quatro and put my second W8-1363 in the 0.9 ft. box. Head to head against the original 0.64 ft. box, the larger one definitely sounds better.

I don't think the plate amp boost is to blame for the sound quality. I tried this sub on an unboosted SA240 at Depthsounder's house, and since the untimely demise of the Klipsch plate amp I am running it on a SLA470. The smaller box sounds muddy boosted or not.

First the Quatro in 0.9ft. (all sims without boost)


The TB W8-1363 in 0.64ft.


Tang Band in 0.9ft.

[arlis_1957@yahoo.com]

can you show us the excursion graph for both as well?

[jbruner]

can you show us the excursion graph for both as well?

All arbitrarily at 200 watts-too much for the Quatro.
No boost, no subsonic filter.

The Quatro in 0.9ft. 315g


The TB W8-1363 in 0.64ft. 450g


The TB W8-1363 in 0.9ft. 315g

[Jeff B.]

The mass tunes the resonance frequency only. The efficiency is set by the woofer's parameters and the box volume. Changing the mass on the PR will not directly change the efficiency, but it will change it indirectly in the same way shortening a port will: by raising Fb; the system efficiency at Fb increases too. Having said that, for a given woofer a larger enclosure will be more efficient, and it will take less mass to reach the same tuning frequency. The lower mass is not what is increasing the efficiency - it's the larger volume that is doing that. It all goes back to Hoffman's Iron Law. Increase the volume - keep the same tuning - efficiency rises......

[WmAx]

If you are intent on finding an 8" driver that will give you the transparent bass you are looking for, I'm afraid it will be far more costly than the TB. Two that come to mine are the TC Sounds made 8" (that used to be sold by Sound Splinter - has been out of stock for a long time) and the JL W7 8". Both of these have extraordinary linear excursion, by way of the motor and suspension. Both have very robust motors that can handle 500 watts continuous, no problem, and with very little power compression (about 1dB maximum). Best bet is finding a used TC Sounds (Sound Splinter) unit. The JL, even used, is too expensive, really. However, the 10" PR you are using likely does not have anywhere near enough excursion to operate with these 8" drivers suggested above. These 8" units can easily produce the real-world output and extension of typical high quality conventional 12" subwoofers.

-Chris