Tube Friendly Speakers - Down to 30Hz - $3000?

Hi Tvad,

Well you like to push the envelope, don't you! Given that I'm sure you've done quite a bit of investigation on your own, you've probably found that what you're looking for is a fairly tall order.

Chances are I don't have anything that would meet all of your requirements, but let me toss out some ideas of what sort of characteristics you might look for.

First, in order to get deep bass in a small-footprint box yet retain high enough efficiency to work with a 15 watt tube amp, you'll have to cheat.

Two ways to cheat here: Corner loading, and using a powered woofer section. Either one will enable you to get a lot of bass from a fairly small-footprint enclosure, and might meet your 30 Hz target.

If my feeble memory serves me, you heard a speaker of mine with a built-in powered woofer section at the VTV show in Pasadena last November. The upper range drivers on that speaker present a roughly 16 ohm load at 93 dB efficiency. I had to redesign the woofer section when my woofer supplier discontinued the model I was using, and I'm pretty much abandoning that project as the parts cost have gone up to too much for me to be confident that the speaker is competitive in its new higher price range.

If you opt for placing the speaker in or near the corner, a reflex enclosure would be my choice over a sealed one. At first glance that seems counter-intuitive, but if you tune the reflex enclosure lower by increasing the vent length, it will probably work well in the corner. If you can't change the tuning, then any speaker not designed for corner placement will sound way too boomy when placed in the corner.

Another consideration is midrange coloration from corner placement. Basically, the walls of the room will act like a big 90 degree horn, and redirect side lobe energy forward toward the listening position, altering the tonal balance. A speaker with a uniform radiation pattern largely confined to a 90 degree forward arc would have a much better chance of not being colored in the midrange by corner placement.

Could you live with a roughly 15" by 15" footprint? If so, I might have something under development that could be tuned to work well in a corner and thereby meet your requirements.

Best of luck to you in your quest!

Duke

"If you're not cheating, you're not trying hard enough" - Gene LeBelle

Tvad,

Thanks for the clarifications, including what size footprint is feasible.

An honest 30 Hz extension is still not easy to come by at three grand a pair, but if you can live with 35 Hz instead of 30 Hz extension you might consider looking for a pair of Altec Model 14's in good condition. Push 'em back flush against the wall and I bet they'd get pretty close to 30 Hz. Even up against today's speakers, the Model 14 is very competitive. If they were still in production I'd sell 'em.

Duke

Tvad,

One thing my wife and I have found with squatty flat-top speakers (like the Altecs I mentioned) is that they in effect raise the floor up thirty inches or so. They're not so tall that you can't put things on them, and when so decorated they blend into a room better than their width would lead you to expect.

I've been scratching my head about reasonably narrow, deep speakers with decent bass and smooth impedance curves, and Fried and Buggtussel come to mind. I was a dealer for the latter company, which is now sadly out of business. Both use transmission-line enclosures. While both have models rated at 4 ohms, with the Buggtussels at least it's an honest, resistive 4 ohms - still a relatively easy load to drive.

Another possibility is SP Technologies. The Timepiece 2.1 meets all of your requirements except efficiency. I like the two-way with waveguide approach.

Soliloquy makes tube-friendly speakers. I'm not real familiar with their lineup, but recall liking what I heard from one of their larger models at CES a few years ago.

How close to the nearby walls do you anticipate placing the speakers? Can they be toed in? Given that the Tyler PD speakers failed the WAF test, can you give us an example of a speaker that would pass, even if it doesn't meet your other requirements? If it turns out that you can't "have it all" at that price, in what area would you be least reluctant to relax your requirements a bit?

Duke

Tvad, I did some modelling and what you are looking for (89 dB efficient, -3 dB at 30 Hz without significant reinforcement from nearby walls, fairly small footprint) is definitely possible. An 89 dB efficient woofer in a 3 cubic foot enclosure will give you honest extension to 30 Hz.

Note that marketing department claims can and often do wax a bit optimistic, but the basic tradeoffs of box size vs efficiency vs bass extension that the engineers work with are pretty consistent, at least in this quadrant of the galaxy. An overly optimistic claim doesn't mean that the engineering is suspect; only that the marketing department's claims aren't reliable. I can think of a manufacturer who exaggerates bass exension claims by almost a whole octave, yet in my opinion builds some very competitive speakers despite their (imho) questionable marketing approach.

Duke

Hi Tvad,

I like the Tetras very much. They are warm and forgiving without losing touch with the excitement and liveliness in the music. Very easy to listen to long-term. Based on what I gather about your preferences, I think you'll like them too. In a more perfect world where I had a bit more space and money to take on a few more loudspeaker lines, I'd be a Tetra dealer.

Duke

Hi Tvad,

I have a friend who owned Silverline Reference 17's, and they were very nice little speakers. In his set-up, I'd estimate they got down to maybe the upper to mid 40's.

I'm skeptical of the 17.5's implied claim of extension to 32 Hz (although to be precise no plus-or-minus-dB tolerance is specified). Assuming an 88 to 90 db efficient woofer in a .65 cubic foot vented enclosure, the response will be down at least 10 dB at 32 Hz without significant boundary reinforcement. While it's true that I don't know the specific parameters of the Dynaudio woofer used, enclosure volume and efficiency and bass extension are interrelated enough that knowing any two will allow a reasonably reliable extrapolation of the third.

You might find it useful to make calculations of your own to check out manufacturer's claims. Speaker designers are pretty much constrained by the same sets of rules, unlike writers of ad copy.

You can download a pretty good little speaker simulation program here. Try the free demo version - that's probably all you really need. I can help you run a few practice simulations if you'd like.

Best regards,

Duke

Tvad wrote:

"An amplifier manufacturer told me yesterday that the use of Zeros will reduce the maximum power available to the loudspeakers. So, they do not appear to be an ideal solution if using low powered amplifiers."

I think the amp manufacturer was over-generalizing a little bit.

What he told you is almost always true for solid state amps, and almost always untrue for OTL tube amps. With transformer coupled tube amps (the vast majority of tube amps fall into this category), the Zeros would improve the power output insofar as they bring the speaker's impedance up into the output transformer's optimum range, and will degrade the power output insofar as they push the impedance up beyond that optimum range. Since most speakers have an up-and-down impedance curve, focus on the region where there's lots of music energy - say 80 Hz to 600 Hz or so (just pulling these numbers out of the air).

Power transfer isn't everything; I have found cases of 16 ohm speakers sounding best on a tube amp's 4-ohm taps (which greatly reduces the available power). I just wanted to register my dissenting opinion about what the amplifier manufacturer told you.

With a product like the Zero, the question is whether or not it's a net improvement. Evidently in many but not all cases it is.

Duke

Minor correction: Actually Duke's $2500/pair speaker is the "Rhythm Prism", with the "Cloud Chaser" being a $3900/pair bipolar model. I think it's the Rhythm Prisms that Ralph is thinking of, as they can be tuned to take advantage of boundary reinforcement. Credit to Audio Note for their innovative and inspirational work in corner loading of low-tuned rear-ported reflex boxes driven by low-damping-factor tube amps. Credit to Atma-Sphere for making Duke's speakers look good at audio shows.