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

1. You want to stay away from a complex crossover (ie, first order &maybe second order, no third or fouth order). This is probably priority no. 1 as complex crossovers use quite a few watts.

2. Ideally, you want a speaker to be a flat 8 ohms (just like a resistor) but since this is next-to impossible, get a speaker w/o a wildly fluctuating impedance that stays above 4 ohms minimum. (In my experience, tubes do not like to be run using less than 4 ohms.)

3. Keep the volume level reasonable (tubes do have less severe clipping charicteristics, but none-the-less, they do clip). Medium efficientcy speakers driven with tubes DO NOT like to party.

My speakers are Spica TC-60. A good review is in December 1994 edition of Stereophile.

I have no experience with TDL speakers & couldn't find TDL website.

Dilly, try this link
http://kosat.consultit.no/~ketil/lowther/voigtpip.html

The dimensions shown in those plans are metric, and are INSIDE DIMENSIONS.

I have used the Lowther EX3 in this enclosure, and found it to be the best match, in my opinion. I also made some mods which would be important in getting the best bass response. Contact me if you are going to make these, and I'll give you the information you need to do this.

In hooking up my 300B SET amps to my Silverline SR17 monitors (89 db) I've found they can play at very conservative volumes, but the limits of headroom approaches rapidly as you increase the volume to more engaging levels of listening (for me this is around 85-95db, but my wife claims I'm hard of hearing). At those levels that combination renders some very audible distortion when pressed. I would definitely not depend on that combination as my system unless it were a bedroom system for occasional low-level listening, or perhaps a background system. Either of these applications seem to me like a waste of a good amp(s), as well as some outstanding speakers in the case of the SR17's. For an 8watt SET system I'd keep my minimum efficiency worth considering more like 94db to give you a more practical application of those amps. I've had pretty good results with 90db floorstanders, but ultimately I'd want a bit more for my 8 watts.

Marco

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.