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Lowther Voigt Pipes are up and running

First, the Lowther people sent me a pair of EX3's instead of DX3's. The mistake turned out to be a great match for my Voigt Pipes! For some reason, I did not have any severe comb-filtering problems with this cabinet. But, I did have Baffle Step drop-off that was weakening the bass response and lower midrange. The 12" baffle was losing wave reinforcement at about 360Hz. So I experimented with adding some 12" styrofoam "boards" on both sides of the Pipes. Huge difference! Once I verified the baffle reinforcement that I had calculated, I then bought 12" wide oak panels the full 6' height of the speakers and added them to both sides of the pipes with piano hinges, so I could tune the "wings" by moving them back on various angles to keep the bass, and get them out of the diffraction plane as much as possible. It works great! It turns out that a few degrees backward angle on each "wing" does exactly what I wanted. The imaging stays tight and the bass is really powerful. Baffle step is compensated down to about 125Hz and the port picks up well from there down. the "wings" also provide a 3db boost of the port output so I think I am getting below 40Hz. I've heard people say these Lowther Voigt Pipes don't have much bass. With these baffle "wings" they have killer bass that is tight and deep and powerful. No noticeable holes or dips even when listening to "walking bass". I am extremely happy with the results of this project. I think that this is the key to the Voigt Pipe dilemma. I also added the parallel non-inductive resistors of 24 ohms across the terminals to reduce the impedance spike at the resonant frequency. This lowers the effective bottom end, and I think it helped to wipe out the comb-filter effects too. Comb filtering is the result of impedance/phase changes in the drivers and the pipes at odd-order harmonic points in the bass/midbass. They combine at these points to create nulls or dips at these freq's. I think that the parallel resistors reduced these impedance dips in the drivers, and hence the pipes. A smoothing effect. Seems to work, anyway. Of course, the Lowther drivers are super, super great sounding. You just can't believe how much I am shaking this 24 foot room with one watt out of my MicroZotl! I think overall, I increased the in-cabinet efficiency of the system by 3db with this "wing" mod. That would put this system at 103db with one watt input. It seems to be quite flat in response curve by listening, with some expected room modes reinforcing the bass a little bit. No noticeable "shelving" of certain freq. ranges. Great high end extension, extremely natural tone quality, dynamics to die for, and detail very much like e-stats. Solid images and good, deep, wide soundstage. I am grinning from ear to ear! I've been playing records 11 hours today. This is absolutely too much fun! I can finally get full orchestra sound without the compression that I had on my fostex system. Wait until these Lowthers get broken-in! They are already fantastic! The new Lowther mods definitely work to remove the "shout" that the older models had. No irritating "shout" in the midrange at all. I highly recommend this project to anyone. This is one killer speaker set-up! Questions or comments?
twl
clueless
763 posts
 
Actually there is no need to complain as the EX3 are considered better (more expensive). Not a sow's ear at all!The “DX” and “EX” series both use neodymium magnets, and are similar except that the “EX” series provide a module on the back that keeps midrange and high end noise from rebounding in the compression chamber and escaping through the horn or reflecting back through the driver cone. They also have the equalizer phase plug. Specs are slightly dif but very little. (from Lowther)

Cheers,
sean
6,231 posts
 
Thanks for the update Clueless. I was unaware of the differences in makes / models that Lowther offers. Sean
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twl OP
3,251 posts
 
Okay, guys, I'll answer each question one-by-one, in order of posting.
First, Clueless, the wing idea was kind of an adaptation of a dipole radiator design I saw years ago, except I didn't have to block the front wave from the rear. I simply used the 1/8 wavelenth Baffle Step calculation to arrive at 3'(125Hz). Going wider would not have gained me anything, since the vertical baffle was 6'(3'up and 3'down from center), and the 1/8 wave rule acts upon the shortest distance. The piano hinge to adjust them was also in that dipole design I saw.
The parallel non-inductive resistor idea is not mine either, but I used it on my Fostex single driver system to great effect, so I tried it with the Lowthers too. I turns out the the Lowthers have an even higher impedance peak (50 ohms)at the resonant freq than the Fostex. It is sort of like a Zobel without the cap. Without the cap, it acts on all spikes and dips in the entire range. Making the amp having an easier load and smoothing the response. I think this helped with the comb-filtering as well as the bottom end. The trick is to pick a value that will reduce the spike as much as possible, without dropping the nominal impedance more than you have to. I wound up using 24 ohms to give me a 6 ohm nominal.
I used the exact Lowther Club of Norway plan and added the wings later. If you want to duplicate these, email me.
Patrick, I am working on getting some digital pix. They look cool.
Sean, the wings at this time are just friction held by the hinges. I will try to add a bracket and see if that improves things or not. The wings are 6 ft x 1 ft of solid oak, so they are pretty heavy. I'll check it out.
I did all the mods you suggest on my fostex system, but not on the Lowther. The baskets are cast and damped already. The new whizzer cone does away with the "shout" already too. Lowther uses a proprietary cone treatment and advises against doping. Thanks much for your interest. Good luck on your future projects too.
Clueless, yes the EX3 is a more advanced unit. I think the "can" on the back really helped keep the mids out of the port. Also eliminated the chances of "smear" from reflections into the rear of the cone.
I'm so glad that you guys are so interested in my project. It really makes me feel good to share this with people who care about this sort of thing.
One more thing, these speakers look really good. The entire front, including wings, is made from solid red oak which I carefully sanded, stained, sealed, and lacquered in natural color. No tints or colored stains, just natural grain highlights. With the wings spread, they look sort of like wooden SoundLabs, since the wings angled slightly back give them a curved kind of appearance. Large, imposing, low WAF, and very upscale looking. Definitely the coolest system I've ever made, by far. The back parts are MDF, screwed and glued, and sprayed with automotive rubberized undercoating to damp the MDF resonances. It gives a nice textured look which is also functional. Drivers are wired with 26ga single conductor magnet wire. They look fairly professional for a non-cabinetmaker. Total cost was about $1300 for everything. Sound is more like $10000. I'm going back to play more records now. Thanks, guys.
herman
2,217 posts
 
I also have the EX3 (in a Lamhorn cabinet) but ended up taking off the rear can, which turns it into a DX3 except you have the newer phase plug. I then damped the panel directly behind the driver with some sonex jr. to catch the higher frequencies in the rear wave. I will try some other materials to see how they affect the sound but the Sonex works pretty well. The US Lowther site recommends a felt pad. It made the speaker more dynamic and also a little smoother. I think the driver has trouble breathing with the metal can behind it.

It takes some effort to work the cans loose since they are siliconed on but they come off if you get a very thin blade under the edge and pry. If you don't like it, you can take some silicone caulk and put the cans back on.

I assumed the basket was filled with foam but it is not. The only foam is those little round pieces that you can see sticking out of the holes in the can. There is also a stranded wire extension from the terminals on the can to the ones on the speaker. With the can removed, I soldered my speaker wires directly to the leads from the voice coil after securing them (the speaker cables) to the Lowther frame with tie wraps. I am using the Michael Green speaker cables, which are a great bargain even though they raised the price a little recently.

I also agree that the modifications that Sean suggests are uneeded and/or unwise with the new style drivers. The foam idea is not needed with the new whizzer cone, and I am unwilling to experiment with a non-reversible modification like dope on a $900 set of drivers.

TWL, if they sound good now, you will be amazed at how much better they sound after breaking them in.
ultrakaz
187 posts
 
Congratulations and thanks for sharing your project with us! Sounds like you hit a home run at your first at bat with the Voigts. You mentioned that you coated the back of the speakers with acoustic dampening spray, was that on the outside or inside or both. I'm curious to see what you will come up with to control the wings resonance (maybe that acoustic spray on the the back, although it may not be a problem) and stabilize them (hinges may get loose over time).
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