What speakers for 300B S.E.T ??

Twl,

This looks like a very rewarding project. How do your speakers sound in comparison with other horns that you have heard?

Beautiful system, by the way.

Boa2, the Voigt Pipes are kind of a combination of rear-horn, transmission line, and bass reflex. They are not the same as the more typical horn speakers, in that they are direct radiator dynamic for most of the frequency range, and use rear-loaded backwave for augmentation of the frequencies below 400Hz, to counter the natural slow rolloff of the driver that begins around that point. The cabinet is actually tuned for 41Hz, and that is about the bottom end of the system.

I tend to prefer a rear-horn over a front-horn system, but I have heard some very nice front horns too. The Voigt Pipes can manage somewhat deeper bass than most true horns because they are not limited by the mouth/taper/length considerations that limit the bass response. Most true horn Lowther systems cannot reach as deep as 41Hz, due to the nature of the horn designs, and the size limitations for home use.

I made my Voigt Pipes because they were something that would perform well, and were easy to make, and were in my budget range. They allowed me to spend the bulk of the budget on the drivers, and saved money by DIY cabinets.

With a couple of mods, they perform quite admirably, and I like them very much. They are about the easiest cabinets in the world to make, and they make entering the "Lowther world" much less expensive, and very enjoyable.

Thanks for your nice comment about my system. It is modest, but I like it.

Twl,

Thank you for the great feedback. Sounds like this could be a fun project in my future, and one that potentially could work perfectly for Dilly.
All the best,
Howard

Friend of mine has a very nice pair of Lowther drivers in a bass reflex cabinet. The sound is wonderful. I think he is looking for 900 for the pair.

If you want cheap try a pair of Klipsch RB5 used; nice, accurate sound and very efficient

Howard, I found that this project was very rewarding and enjoyable to do. If is alot of fun to play with single-driver systems, because alot of the complexity of making speakers(crossover design and building/tweaking) is eliminated. Basically if you can do a good job of putting the cabinet together, you'll have good results. This is already a proven cabinet, and has been around for about 70 years now, originally designed by P. Voigt who was the original designer of the Lowther driver. Also, as can be seen by the Cain & Cain Abbey, and some other Voigt Pipe designs commercially available, this cabinet has the characteristics of working as intended, even when a variety of drivers are used. Fostex 8" Sigma drivers work fine, all the 8" Lowther drivers, AER 8" drivers, REPS-1 drivers, even little FE-103(4") have been used successfully in these Voigt Pipe cabinets. That's one of the things that makes Voigt Pipes so popular with DIY people.

One of the key issues with Voigts is to make sure the cabinet stuffing is done right, or the tonal balance will be off because of the lack of "blending" the port output with the direct radiator output. This has to be done properly. The cabinet stuffing determines how strong the midrange output will be, and has an big effect on the flatness of the frequency response. If you have too much midrange coming from the port, then there is a hump in the midrange response(and also an imaging shift) and below, and if you don't have enough, then there is a dip in the midrange response and below. Adding more stuffing makes less midrange output of the port, and taking away stuffing makes more midrange output at the port. You strive for an even balance, so that the port does not call attention to itself.

Many articles on Voigt Pipes make a big issue out of the possible "comb filtering" effects of the interactions of the direct radiator and the port mouth. They say it results is some harmonic cancellation of certain frequencies that are multiples of the cabinet resonance tuning. In practice, I have observed none of this, and either I got very lucky, or they are making a mountain out of a mole-hill. I wouldn't worry too much about comb-filtering on these.

Lowthers and most single-drivers take a very long time to properly break in. The mids and highs come in quite early, but the bass response is weak until at least 100 hours of play time. It continues to improve up to around 500 hours of play.

Even after break in, there can be a desire for a little more bass impact, and the "swinging door" mods that I designed and implemented on my speakers address this issue. It is related to the boundary effect, and wave-launch off the front baffle, and it is called "baffle-step loss". The narrow cabinet fails to reinforce the lower frequencies and results in a 5db loss in response below about 128Hz. The wider baffle face that is provided by the "swinging door" mod handles this by acoustically providing the added surface that is needed.