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.
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.
Attachments
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.
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.
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.
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.
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.
dave
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?
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?
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
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
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.
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.
Alright. Well thanks for the guidance, planet10!
I don't have windows either. I'm a linux guy. If anyone's with mathcad is interested in this, that'd be cool. Otherwise, these are still good-sounding speakers.
I think that I will alter my designs for the bookshelf model I want to build. It will still be a bass-reflex design, and still use PVC. But the driver I was looking at would require much less enclosure volume, which translates to a shorter pipe. Also, I may use pvc adapters to bump up the diameter even further, thus shortening the length further.
How deep can the chamber be, with a 3.5 inch driver, before getting a standing quarter wave?
I don't have windows either. I'm a linux guy. If anyone's with mathcad is interested in this, that'd be cool. Otherwise, these are still good-sounding speakers.
I think that I will alter my designs for the bookshelf model I want to build. It will still be a bass-reflex design, and still use PVC. But the driver I was looking at would require much less enclosure volume, which translates to a shorter pipe. Also, I may use pvc adapters to bump up the diameter even further, thus shortening the length further.
How deep can the chamber be, with a 3.5 inch driver, before getting a standing quarter wave?
OK, I've been reading hours worth of stuff on transmission lines. I think without buying the mathcad worksheets and using them on a friend's windows machine, I won't be able to perfectly model the speakers.
In addition, from the alignment tables, it looks like the minimum diameter for a ml-tl should be 6 inches for these drivers, so I don't think I will ever be able to get them to be optimum.
However, what about half-wave resonators? I've been googling them, and can't seem to find too much. I think if I add a T adapter to the base of the tubes, they will be just the right length if I stuff them with long-haired wool, to make a half-wave resonator tuned to the Fs of the speakers.
In addition, from the alignment tables, it looks like the minimum diameter for a ml-tl should be 6 inches for these drivers, so I don't think I will ever be able to get them to be optimum.
However, what about half-wave resonators? I've been googling them, and can't seem to find too much. I think if I add a T adapter to the base of the tubes, they will be just the right length if I stuff them with long-haired wool, to make a half-wave resonator tuned to the Fs of the speakers.
There aren't any alignment tables for the MLTLs (at least, Martin hasn't done any TTBOMK). Rick Schultz did some simple ones, and a few of us have our own alignments / design routines we work to, but that's about it AFAIK.
I took a quick gander at your pipes the other day; FWIW, the basic alignment didn't look too bad all things considered; that said, there are things that software doesn't account for. If you like what they do, I'd be inclined to leave alone & if you want a new project, go for a new one rather than trying to change what you have, or pull it apart. We (as in everyone here) can help with that.
I took a quick gander at your pipes the other day; FWIW, the basic alignment didn't look too bad all things considered; that said, there are things that software doesn't account for. If you like what they do, I'd be inclined to leave alone & if you want a new project, go for a new one rather than trying to change what you have, or pull it apart. We (as in everyone here) can help with that.
Last edited:
Dust in the coil? I've thought about that. I think a weekly spritz of compressed air will do the trick, as long as I am careful.
And scottmoose, you're probably right -- I should just leave them alone. EQd theyre great. I don't think there are any clipping issues, or phase issues, so I should just count my blessings that it worked decently.
I've got my design for the Vanth bass-reflex speakers down, and I think it should eliminate the standing wave problem, while still using PVC fittings. I will post a new thread when I build them, in a month or two.
But I am still interested in half-wave resonators. If anyone's published an article outlining the theory I'd be interested.
And scottmoose, you're probably right -- I should just leave them alone. EQd theyre great. I don't think there are any clipping issues, or phase issues, so I should just count my blessings that it worked decently.
I've got my design for the Vanth bass-reflex speakers down, and I think it should eliminate the standing wave problem, while still using PVC fittings. I will post a new thread when I build them, in a month or two.
But I am still interested in half-wave resonators. If anyone's published an article outlining the theory I'd be interested.
Last edited:
go directly to MJK's QuarterWave site, do not pass go, do not spend $200 on any more projects still you've read everything there
twice
Quarter Wavelength Loudspeaker Design
Although I appreciate your concerns, chrisb, I still fully intend to build a second set of bass-reflex bookshelf speakers, which will not have the disproportionate length that is causing it to behave as a transmission line. They will then be closer to "true" bass reflex. In that case, the QW point will be moot.
And for that matter, I have read the whole MJK website. I just need to read it a few more times before I grasp all of it. And maybe buy the worksheets.
And for that matter, I have read the whole MJK website. I just need to read it a few more times before I grasp all of it. And maybe buy the worksheets.
Last edited:
Fair enough - my point was if you're planning on further exploration of this particular category of enclosures (i.e. the continuum of QW action bases designs from VP to TLs to "BLH") as mentioned, you could do far worse that to study Martin's work and build one of his projects, or one of many enclosures designed by others using his worksheets. It's always faster to follow a proven plan, but then I'm just too lazy to want to learn how to do the math - I'd just rather build stuff.
Just as with the aforementioned QW continuum, there is a wide range of vented enclosure designs, some of which straddle borders of simple categorization.
anyway - enjoy your next projects
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.