I theorize: "Convergence".....

[Wolf]

Dynamo- yes- this is what I was going for!

As to a test report, I had to reduce the level on the Crowns because this is RCA level input. I have it in the middle of the room, so it's in free-space. Nothing really major there in terms of capable output. I have it maxed out just to meet up, so 200W is about right. I suspect less would be applicable in an all RCA signal driven system. I've been playing some various music, and even some Bass Mechanik. Moonstone is mostly 27 cycles, and in free-space, it does not hit the fundamental. I imagine against a room boundary it just might succeed. Everything above that seems to be really nice and tight. I have the xover set about 1:00 on the dial adjusted by ear, and nothing untoward seems to be coming from it. 30Hz up in free space is pretty decent, and it's shaking the couch and everything else in the room.

I'm pretty happy with how this turned out!
Wolf

[dynamo]

I like the silver sheet metal screws, gives a tough industrial look

[philthien]

Looking forward to a report on how this sounds.

[marvin]

Come on , Ben, plain black drywall screws will look better than those silver hex heads to mount the plate amp!

[Wolf]

Oh, forgot-

The Euro block was only used as a test-point for the impedance measurement. One side is the amplifier, and the other the sub. I'll likely remove it later....

Later,
Wolf

[Wolf]

Okay...

It only required 2(!) 1.5" steel fender washers to tune the PR down from 51 Hz to 49Hz. I did not expect the PR to be that close to tuning inherently. I'll test it out tomorrow before work so I don't wake up the family.
Here's the measured impedance up to 300Hz:



I used the hex-head screws so I could use the 0.25" nut driver from most magnetic bit sets. Being a bandpass, the sealing of the chambers is paramount for performance. Normally, I use the poly-glue to seal the gaps as it expands, and nothing else is required. I used caulking of the center partition, as well as weather stripping on both the TB and the Eminence PR. The Plate amp has a seal tape on it already, so that sufficed. I lightly stuffed the sealed chamber with polyfil, and lined the perimeter of the reflex chamber with 0.5" thick open-cell foam.

The suspension on this thing is TIGHT! I can't wait to try it out tomorrow before work!

More photos...








Later,
Wolf

[Wolf]

Now that the Entertainment Center is constructed and in place currently, awaiting a few more things to make it all as I want it finale, it's time to progress on some other builds...

Got the boards cut out for the Convergence today. I ended up not using 2 full boards for the center partition. The driver mounting board is solid except for the hole, but the second layer I pieced together with scraps so I don't have to waist so much material. The method of active driver mounting should allow for removal, so the framed layer will be closer to a square cutout. This way I can grab an edge of the driver frame from the opening. The recessed amp mounting on the rear and possibly an added handle on the top will allow easy movement of the completed structure.

Driver mounting double-board, recently glued up:


Later,
Wolf

[Wolf]

Eric- I already have about 4 subs I can pair them with. In my room though, I really don't need the sub with them with the F3 as low as it already is.

Wolf

[6thplanet]

This will be cool Wolf. Logitech did a very nice job on the sub for their Z4 system which is a crappy 4" driver loaded as you're doing with a cheap 8" PR. They also ported in between the 2 chambers. I'm not sure exactly what alignment that even turned out to be but it sounded great for a 4". Looking forward to your listening impressions.

Dan

The el'cheepo computer set I bought at Big Lots also uses that very same "sub" and works alright for what it's worth, I use it with my Acorn build. I bet that will be a nice addition for your Cecropia's.

[Wolf]

I built a couple bandpass subs a while back for use with music, and home theater. I think that they can sound very good. Mine was optimized to go deeper than a more traditional ported box design with the same driver. I believe that mine used a -5dB alignment, which requires a bigger box, but allows the f3 to be lower.

I thought about going with a broader response, but that would mean a loss in output sensitivity, and I was already low enough in that category. Therefore, I strived to make it minimal loss. And of course you bumped into another criteria set- size. If I were to have to add port volume or make the enclosure larger to make the port length shorter, I would be reducing the effectiveness of the air-spring and allowing more probability for nonlinearity. I did build a large sub box with ultra-low extension and a large and long port in that large volume, and it could be overdriven if I wasn't careful. So that is another reason I chose the PR-bandpass style box this time.

Chucky- Those might roll away on you.... ; ) Of course, you could always incorporate that into a 3-way....

Later,
Wolf

[isaeagle4031]

Hmm I've still got a couple sections of 12"id pvc pipe and a pair of w8-740ps. Just need a pr or 2.

[rpb]

Aaah ...

All good reasons (I guessed a couple, see I'm learning). I did mean and model HP filter. All I know about bandpass is the sound of the "one-note-wonders" next to my car at stop lights. So I had to ask.

I built a couple bandpass subs a while back for use with music, and home theater. I think that they can sound very good. Mine was optimized to go deeper than a more traditional ported box design with the same driver. I believe that mine used a -5dB alignment, which requires a bigger box, but allows the f3 to be lower.

[Wolf]

Better image of box layout than my chicken scratches:


Hope that helps the visual,
Wolf

[Wolf]

This looks cool! Subscribed.

A few dumb questions, indulge me. You mount the subwoofer thru the PR hole, right? How do you get a screw gun in there? Or do you just use a really long extension?

Yes, Kevin. It's only about 5" from the surface of the box, BUT- the PR is larger than the active driver, and it shouldn't be hard to get it mounted. FWIW, I rarely mount drivers using a screw-gun due to fear of piercing a surround, and will likely install the wood/machine screws by hand. I see no reason you couldn't make the box in 2 sections, and then bolt the entirety of the PR sector atop the active driver either. That's just another way to do it. I even considered the butterfly-clasps from pro-sound to lock them together into a seal strip. Since I'm using a 12" PR, it should be rather easy with just staged installation of driver and then PR.

Later, and thanks guys for the interest and positive thoughts,
Wolf

[isaeagle4031]

This will be cool Wolf. Logitech did a very nice job on the sub for their Z4 system which is a crappy 4" driver loaded as you're doing with a cheap 8" PR. They also ported in between the 2 chambers. I'm not sure exactly what alignment that even turned out to be but it sounded great for a 4". Looking forward to your listening impressions.

Dan

if the ports run from the rear volume to the front, then it is a 6th order series tuned BP. if both volumes are ported to the outside, it's a 6th order parallel tuned.