LOWTHER SPEAKERS USA

Over the years, Lowther speakers have traditionally been mounted in a type of enclosure known as a 'bass horn.' Many different bass horn enclosures have been designed for them, but only a few modern 'bass reflex' designs. We decided to test as many of the designs as we could. We did so in side-by-side comparisons in the same listening room, using identical equipment. Surprisingly--and contrary to the enduring myth that Lowthers require bass horn-loaded cabinets--we found that modern 'bass reflex' enclosures were better than any bass horn design. However, bass horn enclosures do work well with classical music or in extremely 'live' rooms.

For those of you unfamiliar with the term 'bass horn', it is a cabinet design with a small wooden 'box', or chamber, behind the driver. This 'box' feeds into a labyrinth (pathway) that grows exponentially larger as it moves through the cabinet. The sound from the back of the driver follows this passageway as it winds back and forth and grows larger as it moves towards the exit. Eventually, it ends in a very large 'mouth'. This is actually called a 'folded' horn. If it were not folded, it would extend 6 feet or more into the room.

The theory is, that--like a cheerleader's megaphone--the sound will be amplified. This was essential when the only amplifiers available were one or two watts. However, there are many problems with this design.

1. Distortion is created by reflections from the 'box' behind the driver.

In a normal bass reflex design, there is acoustic damping material behind the driver. This absorbs the sound coming from the back of the cone. But, because of the necessity of having the sound waves move through the 'horn', it is impossible to fit damping material here in a bass horn enclosure. Consequently, the sound from the back of the cone hits the back of the box and reflects back to the driver. This causes reinforcement of some frequencies and cancellation of others. In other words, distortion.

2. Horn-loaded designs will 'fatten' the midrange and upper bass regions of the music.

This is because the sound emanating from the back of the cone goes through the bass horn and reaches the listener AFTER the music from the front of the cone. This time delay is especially pronounced with bass horns that exit at the front of the cabinet. This makes vocals and instruments 'thicker.' Each note is of longer duration than it was on the recording. The single best feature of Lowthers is the detail they are capable of reproducing. Much of this is can be lost by cancellation or unnatural enhancement of the sound coming from the bass horn. However, some people hear this as 'warmth' and 'smoothness.' It can certainly help to tame an acoustically 'hard' or 'live' room.

3. Imaging and soundstage are very poor or non-existent with many bass horn designs.

This is because there are at least three separate sound sources coming from both the left and right speakers--sound directly from the driver, delayed sound from the bass horn, and sound from cabinet resonances caused by vibration (because of the labyrinth, it is not possible to properly brace bass horn cabinets). None of this information is time coherent. Each note on the recording arrives at three different times at the listener's ears (six, if you count both left and right speakers). Most of these designs date from the mono era when there was no such thing as 'stereo.' But, again, this can mimic what goes on in a concert hall and can be desireable for classical music where 'imaging' is not especially relevant.

4. Horn-loaded enclosures can exhibit a ragged bass response.

It's not the smooth response most people are used to--and prefer--from bass reflex enclosures. With each change in a third of an octave, the response may be up 8dB, then down 6dB, then up another 7dB. The worst bass horn designs end up making bass 'noise' rather than clearly articulated bass notes. This is where the term 'one note bass' comes from. The Lowther factory has spent 60 years improving bass horn designs. The most significant advance is probably the discovery of the 'Bicor' principle, where an additional small passageway, throughout the horn, gets rid of standing waves and improves bass response significantly. This is the most important reason for building a factory bass horn enclosure.

5. Horn-loaded designs are very difficult--and expensive--to build, and hard to place in most rooms.

Because of the nature of their design, they also have to be quite large. But some of the factory designs are surprisingly small and attractive.

6. Horn-loaded designs do not play very low bass.

A bass reflex design will actually go significantly 'lower' in the bass region than almost all of the bass horn designs. The best bass reflex enclosures are capable of flat response to 40 Hz (-3 dB), while almost all of the bass horn designs rolloff below 63 Hz. A bass horn design large enough to produce the lowest frequencies would fill the entire end of a normal room. But, again, some of the factory bass horn enclosures--using the 'Bicor' principle--are also capable of smooth response to 40 hz.

7. There is no significant efficiency advantage with bass horn designs.

The most efficient bass horn designs are only 2 or 3dB more efficient than a properly designed bass reflex enclosure. And with Lowthers in bass reflex already producing at least 102 dB for one one watt, this is pretty academic.

8. Classical music and bass horn designs.

Classical music is unique in that the concert hall is an integral part of the enjoyment of the performance. It is virtually impossible to make a recording which can accurately capture a classical music performance in a large hall. This is because--in a concert hall--you hear many different sources of sound--the music coming directly from the orchestra--the reflections off side walls, the ceiling, the back of the hall--resonances coming from the floor under the orchestra and the hall itself. And stereo imaging is not an important element in classical music.

In this case, the colorations of a bass horn can mimic what goes on at a classical concert. It's not accurate, of course, but if it can simulate the actual event, then isn't this what's important? So, some of the liabilities of the bass horn design can become assets if many factors are carefully considered (like room placement, etc.)

9. Bridging the gap between bass reflex and bass horn designs.

We would also like to suggest that many of the Lowther factory designed bass horns are some sort of middle ground between bass reflex designs and more traditional bass horns. They address a lot of the flaws in other bass horn enclosures.

For one, they are made of MDF (medium density fiberboard) rather than the plywood traditionally used in bass horn enclosures. This gives a much more inert cabinet which produces far less cabinet resonances. For another, the bass horn mouths exit to the rear or bottom of the cabinet, where high frequency sounds will be absorbed before reaching the listener and clouding the music that came directly from the front of the driver. And, lastly, many of them use the 'Bicor' principle. This is a tiny, secondary passageway from the 'box' behind the driver that helps eliminate standing waves. This helps eliminate much of the ragged bass response that most bass horns exhibit. Many of these factory 'bicor' bass horns are flat to 40 hz--with a smooth response-- which is exceptional for a bass horn design.

The Fidelio and Academy, in particular, offer a compromise between the very soft, warmer sound of other bass horns and the accuracy and detail of the bass reflex designs. They are forgiving of poor material, sound wonderful with classical music, and still have a great deal of detail.

For those of you who wish the 'traditional' bass horn sound, the factory offers many designs. The Acousta series, for example, offers this traditional sound. Other than the ubiquitous 'Klipschorn', the Lowther Acousta 115 is probably the most popular bass horn design of all time. And the stunning Audiovector and TP1 are probably the best bass horn designs, for fullrange drivers, of all time.

10. A bass reflex design that sounds like a bass horn.......but better.

We have designed an enclosure that mounts a second fullrange driver on the top (the inexpensive Audio Nirvana 'Standard 8' at only $118/pr). This speaker points up at the ceiling. We call it the 2.8 'Ambience'. It produces a wonderful ambient presentation--much as the bass horns do--but without many of the problems associated with bass horn designs. Everyone who has heard this new design has found it superior to any bass horn design--even for classical music.

It has better imaging, lower distortion, and all the accurate, realistic bass that can best be achieved with a bass reflex design. Of course, it doesn't image quite as well as a 'normal' bass reflex cabinent when both drivers are operating. But this tradeoff may be worth it for the increased ambience and sense of space that it offers, especially for classical music.

In addition, the 'Ambience' can be built with a switch for the top driver (so it can be turned on or off). With this switch, it is possible to have two distinctly different speakers for the price of one. When you want the best in imaging and soundstage, you can listen with just the front driver operating. The top driver then becomes a 'passive radiator.' You can turn on the top driver when you listen to classical music or want a more ambient sound. Using two drivers works especially well for home theater. The increased bass also makes the two driver setup preferable for more dynamic recordings or extremely large rooms.

Probably 99.9% of all speakers ever built use bass reflex cabinets. Why? Because this design produces the most realistic sound. A properly designed bass reflex cabinet is inert. It does only two things. It locates the driver(s) in the proper position(s) and it produces bass. Nothing else. It neither contributes, nor takes away from the recording.

The first bass reflex design from Lowther was called the 'Acousta 90'. This dates from the 1970's. It was a large 'bookshelf' design of approximately 25x14x10 inches. A few years ago we modified this enclosure to a more modern looking design which we call the '1.3.' While maintaining the same internal volume, the external dimensions became 32x10x11 (with the grill mounted). Performance was similar. The main improvement was getting the driver up higher so it would provide better dispersion.

Further development resulted in an entirely new enclosure called the '2.8.' This is our largest and best sounding design to date. Overall dimensions are approximately 38 1/2 x 14 1/2 x 12. There are two variations. The original 'Series I' has a wide front baffle. The 'MkII' has a thin front baffle. The 'Series I' sounds somewhat warmer and smoother and is preferable in 'live' listening rooms. The 'MkII' is somewhat more detailed and efficient (1 db) and would be preferable in 'soft' listening rooms. However, driver selection will also affect the sound. Bass performance is similar.

The greater internal volume of the '2.8' (twice as many cubic feet, when compared with the '1.3') has resulted in stronger bass performance and a slightly more balanced overall presentation. Of course, using a subwoofer with the '1.3' will help bridge the gap but--even with a subwoofer--the '2.8' still has a bit better bass response than the '1.3'. In speakers, size does matter.

Using room (or boundary) reinforcement, the '2.8' can test relatively flat (minus 3 or 4 dB) to 40 cycles and gives at least 102 dB from one watt (at one meter) with any Lowther driver. And we offer two different cabinet tunings (or 'porting') for the '2.8'. The 'Twin Port' models have slightly lower bass extension. The Big Port' models have more mid bass.

In response to demand for a smaller 'monitor' speaker, we produced a small enclosure of only 19 by 10 1/2 by 12 inches. We had our reservations about putting the Lowther driver in such a small enclosure but we were knocked out by the results. The bass rivals any other minimonitor in output and far surpasses them in clarity, detail, accuracy, and realism. And, of course, all of the unapproachable midrange and treble is unchanged by the smaller cabinet. The 'Minimonitor' can be used in recording studios, for home audio, or home theater. It can also be used successfully as a surround speaker or center channel.

While the '2.8', '1.3', and 'Minimonitor' are satisfying full-range systems in their own right, those who value extreme dynamics in their listening, might want to supplement them with a quality subwoofer. We have done extensive testing of this combination and can tell you, quite honestly, that this will provide all the bass and dynamics you could possibly want. We enthusiastically endorse HSU Subwoofers (800-554-0150). These are as good as any on the market and cost much less. They have an excellent powered subwoofer for as low as $500. You can buy factory direct with a return policy if you are not satisfied. Of course, there are other good brands on the market but be careful. You want a TRUE subwoofer, not just a bass module.

The Lowther factory offers at least 7 different bass reflex designs. In addition to the original 'Acousta 90', there are several single and multi-driver systems.  Some even use the 'Bicor' principle developed for the bass horns to supplement the bass.

We have designed some dual driver systems that are useful for people with special listening needs. Of course, a dual driver system will not image quite as well as a single driver enclosure. However, the reduction in imaging is less than you might imagine. And because these are Lowthers, even the dual driver systems image better than any other speaker. For some people, they might be a worthwhile tradeoff in exchange for what these dual driver systems can do. We have two different versions:

Lowther 2.8 'Dynamic'

We took a standard '2.8' enclosure and added a second driver, below the first one, on the front baffle. Both drivers are wired in parallel for an effective impedance of 4 ohms. This combination gives effortless dynamics without changing the overall tonal balance. It's a good choice for very large rooms or for people who prefer their music LOUD!

Lowther 2.8 'Ambience'

For the 'Ambience', we took a standard '2.8' enclosure and mounted an Audio Nirvana 'Standard 8' driver on the top, pointing up at the ceiling (only $118/pr). Why not another Lowther speaker here? Because the differences with a Lowther driver are 'lost' when this driver points up at the ceiling, so why spend more? The main purpose of this second driver is to double the bass and dynamics.

Both drivers are wired in parallel for an effective impedance of 4 ohms. This design gives a bit more 'spacious' sound. But, most importantly, bass is doubled. While, in reality, it doesn't produce any more bass than the 'Dynamic', it gives the impression of making a lot more bass. The reason is that a lot of midrange and treble output from the top driver is 'lost' in the room before it reaches the listener. But the increased bass is not. So, the overall tonal balance is different.

One interesting advantage of the 'Ambience' is that you can put a switch on the top driver to turn it on or off. For the best imaging and most intimate presentation, you can turn the top driver off and enjoy all the advantages of the original '2.8'. For more ambience (especially good for classical music), more bass, or more dynamics, you can turn the top driver on.

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