My new speakers - Orcus (mark 1) - diyAudio
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Old 28th February 2012, 02:49 AM   #1
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Talking My new speakers - Orcus (mark 1)

This weekend I built myself a new pair of speakers, inspired by Linkwitz's Pluto speakers.

The enclosure is a 4 inch diameter vertical tube made of schedule 40 pvc. It is ported with a 1 inch schedule 40 port. This is mounted to a finished piece of hardwood plywood, with speaker spikes on the bottom.

The drivers are Tang Band W4-1052SDF full range drivers. I carefully got the proper measurements for the chamber after much number crunching: the main chamber is 30 inches long, and the port is 1.7 inches long. Of course, I used speakon connectors.

Now, I was expecting poor bass response, due to the little 4-inch drivers. Also, I expected some high-end dropoff, due to the fact that with the vertical enclosure, these speakers will only be listened to significantly off-axis. I was not mistaken. However, after turning up the bass and treble on my amp just right, the response is surprisingly flat! I would say that I'm good to about 70 hz, just as the Tang Band suggested. Add a sub and I'm good. Even without the sub, they sound great.

As for clarity... wow, these babies are crisp sounding. Much more detailed than I could have imagined for the $130 they cost to make. Plus, due to the vertical nature of the tubes, the sweet spot is HUGE. The whole room has a soundstage.

I'm powering all of it with a little 20 WPC Lepai T-amp. Perfect power rating for these speakers. So amp, cables, and all cost me a little over $150.

My spraypaint ran a bit on the PVC, so I think rather than repainting, I will use some spray adhesive and thin bamboo to make a nice exterior later...

Next project: a similar, but much smaller bookshelf design, using Dayton ND91-4 drivers.
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Old 28th February 2012, 02:59 AM   #2
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intriguing, the smaller speakers you are planning to build -- is there a design description/web site -- or this is yours to experiment ?

thx
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Old 28th February 2012, 03:13 AM   #3
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There is no website, it's all in my head right now.

The Vanth bookshelf speakers will be horizontal pvc tubes (point source, as opposed to the ambience design of their big papa Orcus).

It will also be schedule 40 PVC, but 3 inch diameter and only about 10 inches long. The port will be 1 inch diameter, and will stick out of the back endcap by a couple inches. I will have more exact measurements once I've made a prototype.

I'm figuring that the drivers I want to use for the Vanth speakers have about 4-1/2 dB less sensitivity, but since they're point source they should gain about 3db apparent loudness over the ambience design. So, in all, they should be comparable to the Orcus, but without the advantage of the huge sweet spot the vertical design offers.
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Old 28th February 2012, 04:13 AM   #4
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Quote:
Originally Posted by neebster View Post
The drivers are Tang Band W4-1052SDF full range drivers. I carefully got the proper measurements for the chamber after much number crunching: the main chamber is 30 inches long, and the port is 1.7 inches long.
Calculated as an ML-TL?

dave
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Old 28th February 2012, 04:27 AM   #5
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I think they came out great! How did you connect the speaker to the base?
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Old 28th February 2012, 04:59 AM   #6
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planet10: I calculated the volume as if it were a regular bass reflex box. I have a known diameter, so all I had to do was cut to length. Perhaps I should have used a ML-TL paradigm, but I don't really know much about it. I really should read up on that.

I did adjust for the space taken up by the port and the driver, for what it's worth.

Godzilla: There is a PVC endcap that the tube sits in. This endcap is simply screwed to the wood using 4 wood screws. Bolts would've been better, but I used what was on hand.

I will post pics again when I get the bamboo glued onto the exterior. It may be a few weeks before I get around to it.
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Old 28th February 2012, 05:10 AM   #7
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Quote:
Originally Posted by neebster View Post
planet10: I calculated the volume as if it were a regular bass reflex box. I have a known diameter, so all I had to do was cut to length. Perhaps I should have used a ML-TL paradigm, but I don't really know much about it. I really should read up on that.
Due to the height being significantly larger than the diameter, your box will not be a BR and the tuning will be off (which could explain why it isn't producing bass that you wouldn't expect from a 4" driver)

That should not subtract from your enjoying them, just that you can still get a bit moreout of them.

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Old 28th February 2012, 05:24 AM   #8
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Why does the height/diameter ratio prevent it from being bass-reflex? I suppose I am rather ignorant about this, being that this is my first speaker build. I figured that the chamber tuning would just be based on volume and port size.

Also, I'm finding little on MLTLs, or really TLs in general, specifically non-tapered ones. How would I go about adapting this design to a transmission line?
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Old 28th February 2012, 05:34 AM   #9
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A BR is a lumped model and to work the aspect ratio of the box cannot deviate a lot from a cube.

With one dimension significantly larger than the others, a 1/4 wavelength standing wave develops. this changes the box tuning. (as 1 dimension increases a BR transitions smoothly to an ML-TL,

Your box is an ML-TL but not optimally tuned (the small cross-section also likely means it is not an optimum TL).

There is a lot of stuff on ML-TLs on the forum, but a good place to start it Martin King's quarter-wave site.

dave
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Old 28th February 2012, 05:44 AM   #10
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Hmm. I wonder if I can retune my existing chambers, without using expensive measuring equipment. I've got, uh, a multimeter, and a microphone. This is supposed to be a budget project, so if I can't retune the chamber without expensive equipment, I will have to call it good enough (and it does sound lovely with EQ).

However, if I think I have a shot at getting the chamber tuned correctly by simply coupling another piece of pvc, or shortening the existing one, or stuffing with damping material, then I'm all for it.

I'll read up as much as I can on this, but any pointers from anyone would be much appreciated.
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