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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
herman
2,252 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).
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!
theaudiotweak
2,797 posts
 
I have had cancellation problems with my Dunlavy SC4's. I cured this problem with a crazy looking angled baffle that extends from the top of my speaker to the ceiling. This baffle has about 8 degrees of tilt and hinged angles on the sides. Seems to allow better low frequency loading of the upper and lower woofers, and now, has quite a hit. Everything seems to be more immediate and with better focus. I have tried this device with several speakers including a few Thiel models . I and others felt it was a beneficial improvement. This maybe something as well, you could try. Tom
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.
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