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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

Showing 6 responses by twl

twl OP
3,251 posts
 
Albert, believe it or not, I thought about renting a van and driving down to your place to see how you like these. I know they would sound terrific on your system. But, you would have to only just barely crack open the volume control on your system to get these babies singing. I can't really bring them down there, but I'd love to. I'm sure we'd have a fun time. BTW, these speakers are BIG. With the wings out, they stand 6 feet tall and 3 feet wide. They're solid 3/4" oak. But, with the wings on the piano hinges, they can fold back against the center section when not playing, so they can be just over a foot wide when folded. Then they just look like 6' towers. Pretty cool. Baffle compensation can be adjusted to needs of the room, if someone has a peaky room. Just by different angles of the wings. If you decide to ever try the low-power/high efficiency game, I'll work with you on some designs, if you'd like. Who knows? Maybe next year, I'll come up with some ideas to improve back-horns and have to build a pair of them.
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.
twl OP
3,251 posts
 
Ultrakaz, I used Mar-Hyde rubberized auto undercoat that remains flexible, on the outsides of the MDF sections of the pipes. The lower part of the insides were partially lined with self-stick felt from the crafts section in Wal Mart. As far as resonances in the wings are concerned, I am not noticing any problems there, but I will make a simple bracket arrangement to allow full adjustability as well as locking them in the fully folded position. I don't think any damping on them will be necessary. But when you only have a 1 watt amp, it sure is nice to have to think about getting loud enough to have resonance problems! They do get quite loud. And I'm not really pushing them too hard during the break-in process. After about 30 hours or so, I'll really start to open the throttle on that 1 watt amp. :-) If I played this system for someone, they would never believe that it's only 1 watt. Of course, it is a Berning pure class A triode ZOTL with NOS tubes. And fed by a hotrodded MFA preamp, which is in turn fed by a Teres turntable with OL Silver 250/DenonDL103 thru a Cotter MC transformer. So we're giving these speakers something pretty good to work with. And they do show it. I have to say that this Berning MicroZOTL is a very special little amp that really delivers the goods. Those OTL triodes are hooked directly to the Lowthers and exhibit excellent control and crystal transparency, liquid midrange and full frequency extension from top to bottom with no "tubby triode" sound or transformer saturation rolloff. It kicks butt!
twl OP
3,251 posts
 
Thanks, Tom, it sounds like you have a D'Appolito driver arrangement and you are loading the top woofer off of the ceiling. This can balance the top and bottom woofers because the bottom one has floor loading. In my situation, I have a vaulted ceiling that is 12' high above my speakers and soars to 16' high at the middle of the room. I couldn't put such an extension on my speakers. Thanks for the tip, though, and others reading this may benfit from your experience.
twl OP
3,251 posts
 
Just for an update, the pipes are breaking-in very nicely. Getting even smoother, and more dynamic. The ability to play louder and cleaner than my last speakers has led me to want to push my little amp past its limits, because I just want more and more! So I am getting a new Berning(See my new thread on the Amplifier Page). VERY special amplifier! I guess that, even with DIY, I am no longer in the low-cost system category anymore. Now rapidly approaching $10k. Is there any end to this madness?
twl OP
3,251 posts
 
The latest update is that I have removed the 24 ohm parallel resistor from the system. It seemed to be making the highs a little too hot. The bass didn't change any, so I think it wasn't needed with the Lowthers. The wings are great though. I love the adjustable nature of them. You can tune them to the record if you want. Just move the wings a little back if you want to reduce the bass reinforcement, or a little forward if you want to kick it up a little. Most times I leave them angled back about 20 to 30 degrees. It is sort of like VTA adjustment. You can adjust if the situation dictates. I like that. Drivers are getting even better with mor break-in. They even play a little louder now, too.
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