Speakers for low power amps?

Hi, I am looking for suggestions for a high efficiency speaker. I am considering going to a low power SET setup. I really know nothing about it but I have always wanted to try out the low power amps. I figured I should start with speakers. What should I look for in speakers, just high DB rating? My room is about 14' x 22'. Where I live I have no stores that carry high end audio, so I will have to travel to hear anything. Any opinions?
Just being nosy, but why do you want to give up the system you have? It looks like a really good system.

Have you considered keeping the amp and speakers, and going with a good tube pre-amp like a Herron VTSP-1A/166 or VTSP-2, Conrad-Johnson Premier 17LS2, or CAT?

Reference 3A Di Capo's are really nice for an SET set-up if that's what you want to do
There are many options--any of the single driver speakers--along with many others---Just stay away from speakers that drop below 6--at any point (many speakers say "8" but may drop to 4 in the bass).
Krell man, I like my system but I like to listen at lower volumes. The Aerials don't really open up unless you turn them up. I found my friends 10t speakers to be the same way. I feel it is time for a change. I will look into the REF 3As. Anyone else that have specific models for me to check out?
I'd recommend speakers with a nominal impedance of 8 ohms or above, and without any wild swings into the low impedances.

For amps of 8 watts or more(like 300B), I recommend you select speakers with 93db/watt or higher sensitivity.
For amps of 3.5w - 5w(like 2A3) I recommend speakers of at least 96db/watt.
For amps of 2w(like a 45) I recommend speakers of at least 99db/watt.

Drivers like Lowther, Fostex, AER, REPS, Diatone, Coral, and similar single-driver speakers work well with SET amps, and are often used. Front horn, back horn, or TQWP setups are common.

Some commercial speakers that a commonly mated with SET amps are Cain & Cain Abbey, Beauhorn, Lammhorn 1.8, Lowther(various models), Oris horns, Avant Garde horns, Klipsch horns, etc.
The sensitivity of appropriate speakers depends in part on how powerful your chosen SET amplifier is and how loud you like it. I'd say ballpark guidelines would be 93+ dB speakers for 10 watt SET's; 96+ dB speakers for 5 watt SET's; and 99+ dB speakers for 2.5 watt SET's. These combinations will probably give you undistorted peaks in the 100 dB ballpark at the listening position in your room. If you don't need that kind of output, scale back accordingly.

Speakers that work well with low-powered SET's include models from Classic Audio Reproductions, Avantgarde, Omega, Cain & Cain, Klipsch (Heritage series), Coincident, Vivaldi, Edgarhorn, Rethm, and Tannoy (Prestige line). This list is by no means comprehensive, but includes speakers I've spent time with and have been particularly impressed with.

If by chance you have corners available, you might want to consider the Klipschorns, or perhaps the Hartsfields by Classic Audio Reproductions. If you don't mind building your own cabinets, or have access to a good woodworker, add Pi Speakers and Supravox fullrange drivers (especially the 215-2000 EXC) to your list.

If you're looking more for a fairly inexpensive first pair of high-efficiency speakers, consider the Omegas (the little Super 3R is very nice) or the Cain & Cain Abbey. Disclaimer - I peddle the Omegas.

Best of luck with your quest!

Twl...What is TQWP?
I second the Omega loudspeakers. I had a pair of TS1s and they were really really cool. Super efficient and sound excellent but do realize they have bass limitations.
Here is A link from wellborn labs with a list of recommended speakers for SE Amps. I have owned every Klipsch, and still have highly modifided lascalas, (Heritage series) speakers. they work well with se amps.I like them because you could listen at low listening levels and with just a few watts, they have slam.I have a highly modifided Edgarhorn system 80 that I use mainly. It is not as efficient as Klipsh but has a more neutral midrange, and a better midbass, with a good sub woofer. I get good sound for the type music I like (jazz, rock, r&b, and easy listning). That is an important factor. Certain speakers do better with certain types of music.Take that into consideration.

Good luck


I use the Reference 3A MM DeCapo with a 3.5 watt/ch. 2A3 SET amp. My room is somewhat smaller than yours, but it can get very loud, so the DeCapo may work well for you.


See: http://www.welbornelabs.com/recomendspeaks.htm
Great thread and great answers!
Thanks for all the answers. The Welborn site is great and definatly answers some questions.
El, TQWP is "Tapered Quarter Wave Pipe", such as a Voigt Pipe cabinet, like the Cain & Cain Abbey.
Try silverline Sonata MK3 and Wavelength audio site they have a list of speaker that work will with SET.
Twl: I've never really looked at a Voight pipe, etc... but wouldn't a tapered quarter wave pipe be a transmission line design? Sean
Sean, actually from all the reading that I've done on the subject of the Voigt Pipe(TQWP), the general consensus is that it is a "mix" of transmission line, rear loaded horn, and bass-reflex designs, that "more or less" blend together.

The taper of the Voigt pipe gets wider at the port end, where traditional tapered transmission lines get narrower at the port end.

So this widening toward the port end contributes to the "rear loaded horn" part of the concept.

Also, the driver is located at the approximate middle of the cabinet, and is not located at one end, like either a horn or transmission line would normally be.

So this driver location contributes to the bass reflex part of the concept.

The waves develop in the full tuned length of the cabinet like a transmission line(tuned to quarter-wave), they are somewhat amplified by the moderate widening toward the port (like a horn), and the port does behave to some degree as a bass-reflex port at the frequencies below the horn lower cutoff point.

The top half of the cabinet is well-stuffed, to reduce the midrange and treble frequencies that otherwise would try to come out the port, but allows the bass frequencies to fully develop. The bottom half of the cabinet is hollow, to allow the horn part to work on the lower midrange, and bass frequencies(which is needed to augment the inherent Lowther low-end slow rolloff starting around 500Hz and going down). In the lowest bass frequencies that it can produce, the Lowther excursion is very short(compared with most drivers), and the bass-reflex(and transmission line) parts of the design helps the driver with this.

The cabinet design, with the shape that it has, works like a rear horn for the lower midrange and down, to the point where the length and mouth would normally cause a lower cutoff point. Bass-reflex conditions present then help the ranges below the horn lower cutoff, and the transmission line characteristics keep the driver "loaded" down to the area of the port tuning, so that the driver stays tight and well-controlled with tight bass response, and doesn't "flop around" unless alot of very low frequency energy is "pumped into it" and the "unloaded" driver then flops around(happens on record warps and such). The mids and treble are restricted from the port output in large part by the stuffing in the upper portion of the cabinet, but some small amount makes it out the port(basically inaudible even at short range). The bass-reflex behavior causes a rapid rolloff below the tuning point, and this combined with a very high impedance spike at the F3 of the Lowther driver in the mid 30Hz range, combine to limit the usefulness of the system to about 40Hz on the low end with most typical amplifiers that would be used with these. Since the cabinet is quite shallow behind the driver, and the driver has a very thin paper cone, damping of the back wall of the cabinet behind the driver is needed to prevent "smear" caused by the reflections of the back wave coming back thru the cone face.

So, as you can see, this is a "hodgepodge" of various designs that have aspects of each design playing a role. It is far from a "perfect cabinet design", and nobody really views it as such, even the designer P. Voigt(designer of the Lowther driver), who considered it to be not one of his best efforts(from the 1930's).

However, it remains to be a very workable package, which actually can produce good results(with a bit of tuning work), and has advantages of deeper bass than most of the "true rear horn" designs for Lowthers(or single drivers). The normal lower-cutoff frequency that plagues horn designs because of the shortening of length and reduction of mouth area(in order to fit into the room), and thereby limiting the bass response to around 60Hz or higher, is not nearly as limited by the TQWP design, because it relies on the bass-reflex and transmission line aspects of its design to effectively produce the frequencies lower than the predicted lower horn cutoff point. So the TQWP will play deeper into the bass than a similarly-sized rear horn cabinet would play. And it will do so in a controlled manner which is not bloated, like many pure bass-reflex systems do. You actually get almost an additional 1/2 octave into the bass regions(down to about 40Hz, and maybe a couple Hz lower if you're lucky).

Yes, of course, as with any speaker cabinet with a front radiator and a front port, comb-filtering can(and probably will) take place, to a degree. And, as with any speaker with a narrow baffle-face, the baffle-step losses will occur predictably at the frequencies which can be supported by the baffle-face.

As you know, I have taken steps to correct these things in my cabinets, and the results have been good.

Nobody ever claims these cabinets/speakers as "perfect". But, we do claim them to be very good, and at a very reasonable cost, compared to other speakers which cost significantly more and don't perform as well overall(due to a number of factors involved - taste included).

They do what they do quite well, given the inherent restrictions and drawbacks of the drivers and cabinet design employed. It is a minimalist design, and is very simple, yet complex, at the same time.

The best way to describe it(IMO) is that the corrections needed to bring the system into good fullrange performance are done in the acoustical realm, and not in the electronic realm. Acoustic "filters" and acoustic "boosters" are used, instead of electrical ones. This allows a much simpler signal path, with better efficiency, and fits with very low amplifier power better than using electrical counterparts. We use the basic laws of acoustics to do the work, instead of "forcing" the thing to do what we want through electronic manipulation(that soaks up power, and does other things we don't want).

With a view toward keeping that basic design philosophy alive in my system, I took steps to improve the baffle-step problem by using acoustical boundary reinforcement principles to overcome the previously existing baffle-step losses that were present in the basic design of this cabinet, instead of using an electrical compensating filter network. This enlarged the frontal area(and visual impact) of my speaker system considerably, but worked very well. These are commonly called the "wings mod" or the "swinging-doors mod" for the Voigt Pipe. While I didn't invent this idea, as far as I know I'm the first one to use it on Voigt Pipes. This mod really does the job well, and keeps all my(very limited) amplifier power for making music.

As a result, the sound produced is very "effortless" and "natural" and "unforced" sounding, since there is nothing in the way, and the natural acoustic forces of nature are doing my work for me. Additionally, I keep the "direct drive" feature of my SET amp going directly to each driver with no intervening electrical parts(which definitely is a plus, as you know).

I'm very pleased with this, although I certainly realize that the lowest octave of bass is not reproduced, there are still some minor anomalies in the driver at the upper midrange area(but significantly mitigated by another mod), and also some(relatively minor) anomalies that occur as a consequence of the interactions of the direct radiators and the ports, and a smallish "sweet spot" which results from collapsing dispersion field in the upper frequencies due to driver diameter and beaming characteristics.

As a package, its strengths are good enough to make me feel that the drawbacks are worth it. I think it was a very good project, that was very easy to make, costs a fraction of what a "sonically competing" speaker would cost, and makes a very pleasing musical result,and is efficient enough to work with my 2 watt SET amplifier, which is what I wanted.

Whether others would want to take this route, I can't say.
But it gives me what I want, and so it's good for me.

PS - I should note that when I first constructed these cabinets, there was a hollow, chesty, "boxy" resonance in the lower mids/upper bass(low male voice area), which was due to the cabinet vibrational resonances(unacceptable). When I placed Sistrum Platforms(SP-004) under the cabinets, the cabinet resonance problem totally disappeared, and made the speakers a viable project. Without these platforms, I cannot recommend this project, because there will be that unacceptable resonance there. I know that I sell these platforms, but without having them under there, I would not be listening to these speakers today. I would have moved on to another cabinet design. Take it for what it's worth, but I know this cabinet design inside and out from actual experience. The platforms are "a must" for these. I first tried a set of regular Audiopoints, and that helped, but they weren't enough to do it. The SP-004 platforms did the job admirably, and it was like a miracle cure.
Twl...In the Madisound webpage catalog for Fostex, at the bottom are some enclosure designs, and one in particular looks interesting. "Fostex FE164 Mass Loaded Tapered Quarter Wave Tube" by Martin King. The LF extension suggested by the plot is quite impressive from a wimpy (sorry) FR driver.

These enclosures look very easy to build, but rather ugly IMHO. I have been interested in a flat enclosure configuration that one could hang on the wall like a picture. It seems to me that the Tapered Tube could be coiled for a more compact shape, rather as brass instruments are coiled.

By the way, in a transmission line enclosure, the driver is usually located a short distance down the line, but not near the halfway point as in this example. Where a TL design uses a MTM set of drivers, the two woofers (why don't we say (WTW) are necessarily located at different points. I understand that this makes for smoother response.

Where can I get plans for making a speaker like this?
Here are the plans from the Lowther America website, which were donated by KK Yeo. KK made the cabinets to my specifications, and with numerous conversations with my by telephone and email. He shows the "TWL mod", and how to make it on that PDF file.

Go to this link

Scroll down about halfway to where it says "Voigt Pipe" plans, and click on the link. Its a PDF file so it will take a while to load.

Here is a link to a photo of one of the finished speakers.
El, yes Martin King has done alot of work on this kind of design. His computer aided work, and other testing has yielded some interesting stuff.

The truncated top is touted to reduce certain "problematic" effects because he seems to have determined that the "point" at the top is a problem.

Also, by making a small round port, instead of the traditional "mouth" at the bottom, he's made them more like a bass-reflex design than the original design was.

I haven't tried his design, but it seems to look good on paper.

It is somewhat surprising to hear that deeper bass coming out of a single-driver system. Kind of nice. Not really getting into the really deepest range, but not bad.

He definitely has found out about the baffle-step problem, and designed an electronic baffle-step compensation network that would work for those with extra amplifier power(who can stand to chop 5db off their efficiency rating).

Regarding the "hanging on the wall" type of quarter-wave pipe, you could do that if you are handy at making the "coiled" design out of wood. No reason why it shouldn't work out well that way.

I just made mine from the original idea, and it worked out for me, with a few mods needed. Maybe these others are even better, I don't know.

These speakers can be pretty darn good, if you pay attention to the details about their designs.
Wow. Looks like i found a subject that Twl really likes to talk about : ) Thanks for sharing so much info and background about this design, as it is both interesting and different. I'll have to take a look at the info that El mentioned as being at Madisound to see actual results of something like this. Sean
Thanks, I will take a look at the site.
I took a look at the Lowther site. It doesn't look too hard to build. I have a friend that is in to woodworking so I may try to build them with his help. Twl, I don't have much knowledge about these speakers, how do I chose a driver?
bastani prometheus
Any of the 8" Lowther models or 8" Fostex models will work in that enclosure.

You can also use smaller diameter drivers, by making a smaller hole for the driver.

I used Lowther EX3 drivers in mine.
Twl...Any thoughts about use of these FR drivers in an "open" design. Since LF is such a big problem, why not just use a separate LF driver in a box that would be smaller than the horn that the FR driver would demand. You could still run the FR driver without any X/O.
El, yes that has been done by people on occasion.

The big issue becomes integration of the drivers, because the Lowthers are so fast that most subs or LF drivers don't keep up, and sound sluggish. Sort of the same problem that occurs when trying to match panels or ribbons with many bass drivers. Hard to integrate.

But, it is one way to get deeper into the bass.

Good thinking.
I don't know if they're available south of the border, but FAB speakers, especially the 97db efficient Model 1, are a lead-pipe cinch for low-power tubes. I'm toying with the idea of getting a pair to replace my Coincident Total Victories - looking to get a close to a "SET-driven electrostatic" as possible.

I have a pair of C&C Abbys, but for all that they do well they lack too much in the dynamics, extension and neutrality departments for me to consider them a serious speaker.
Gliderguider, I went to the website and those Fab 1 speakers look pretty cool.

Good extension specs on the low end too.

The Abbeys are nice, but they're not like Lowthers. The Fostex drivers just don't have the speed and detail or efficiency like the neodymium or alnico Lowthers do. Don't "cross off" the single drivers yet, until you hear a set of well broken-in new-series Lowthers in a good pair of cabinets.
I've heard the FAB Model 1 at my hi-fi pusher's store, driven by my Wavelengths. They sounded fantastic - open, clean and very dynamic with great bass slam and faster than Anna Nicole Smith. The amps matched those speakers much better than my big Coincidents - even at a claimed 97db and a realistic 93, those 9 drivers per side need more current than the Tritons put out. The FAB 1's could be driven off a headphone amp...
Don't know if you've made a decision yet, but about this time last year, I stumbled upon a site that offered DIY kits for P/A's, Pre-A's, and an open baffle speaker design that was approx 100 db efficient. I now own the Lady Day's (300B silver version) and the Bastani Prometheus AirForce MK II.

What a leap of faith....and for ONCE in my 35 years of searching for audio nervosa....I'm getting musical satisfaction....

Take a look at www.diyhifisupply.com... and in the U.S. for our distributor www.baulsaudio.com

Brian Cherry (DIY) and Bill Allen (Bauls Audio) are great folks to work with...although Bill gets a little excited at times...neither will try to "sell you"...they just get "jazzed" about the products they offer....and how they sound...I'm a believer !!!