As some of you single driver fans may remember, a few years ago I wrote a more than glowing review of the Lowther PM2A drivers in the Medallion II cabinets on TNT. Since the time that I've written that review, my opinion of the Lowthers still hasn't changed. The Lowther PM2A's have single handedly corrupted my entire audio existence. Toss in a great sounding single ended triode amp and I've found my personal Audio Nirvana. No kidding, my affliction with upgraditus has come to a screeching halt because of the Lowthers and single-ended triode (SET) amplifiers.
It's pretty amazing when you start looking at the audio boards and review magazines out there, more and more people (reviewers included) are discovering that low powered amplifiers coupled with high efficiency, full range drivers make some damned fine sounding music. The great part of all this is that your choices in affordable low powered amplifiers is pretty plentiful. From the Sonic-T at less than $30 clams, to it's heavily modified cousin the Clari-T to the guys like Ron Welborne at Welborne Labs, Steve Deckert at Decware to Anthony Cirella at Handmade Audio, and Don Garber at Fi, you can now affordably mate a great sounding low powered amp to some great sounding full range drivers.
Single-ended low powered amps mated to high efficiency speakers are making some serious waves in the high end market, and rightfully so. For years a handful of hardcore audio guys and a select few reviewers have touted highly their pairings. The person that influenced me the most to go this route was the late Harvey "Gizmo" Rosenberg. With his tremendous ear for sound, a few well-placed words of encouragement and the gentle prodding to keep experimenting with the SET and full range driver setup, I finally found that pot of gold at the end of my audio rainbow shortly after Giz left our reality.
With this iteration, Jon enlisted the help of the Grand Wizard of Cabinetry, the late, great Terry Cain. As you would expect, the Alerion's boast absolutely stunning craftsmanship and finish work. Terry was a master craftsman in every sense of the word. The Alerion cabinets have the signature Cain & Cain, look with a slightly updated stylish base and feet. The enclosure is constructed of solid hardwoods. Visible inside the cabinet, is another of Terry's hallmarks, the stair stepped horn mouth. This type of attention to detail is part of what makes the Cain & Cain enclosures so desirable.
The Alerion design is a simple rear loaded, exponential horn. The construction is impeccable. On the back of the cabinet is an ultra cool Cardas binding post. Inside is some nice sounding Jena wire but after that, there isn't much to talk about... except the notch filter. As many know, some full range drivers can be a little peaky in their midrange. My Lowther PM2A's exhibit absolutely zero of these effects but unfortunately the DX55's do. In turn, Jon has decided to relieve some of their ‘forwardness' with a very simple notch filter (some refer to this as baffle step compensation). Jon may be more correct than the rest of us with his favored terminology in calling it a shelving filter. Essentially what the filter consists of is a coil (an inductor) and a resistor wired in parallel and then placed in series with the positive terminal of the speakers binding post.
Just a little on the design parameters of a shelving filter. The coil determines the frequency width of the shelf and the resistor determines the depth of the shelf. The higher the resistor value, the deeper the shelf. Likewise for the coil, the higher the value, the wider the frequency band that is covered. The actual values of the coil and resistor are determined by the impedance of the driver and the drivers frequency peaks you wish to ‘tame.' If you are interested in learning more about them, a quick Google search using the term "notch filter" will garner you many days of reading.
I've had the occasion to build several of the shelving filters a while back when I had my PM2A's in Martin Kings MLTL enclosures during their break in period. I tried a number of different coil and resistor values until I found the combination that sounded the best to me in my room. The concept of a shelving filter works extremely well. As I mentioned in a previous article, I easily could have lived with my PM2A's in the MLTL's using a shelving filter never given it a second thought (until I heard the back loaded horns).
When I first received the Alerion's, Jon had mounted the shelving filter behind the Lowther driver within the compression chamber. Lowther America has designed this filter using a 4mH coil and a15 Ohm resistor. The shelf starts at about 1500Hz and stops near 3500Hz. The 15 Ohm resistor provides about 10dB of attenuation at the heart of the shelf. On the same board, Jon had included a simple Zobel network. I've never been a big fan of Zobel's especially when used with SET amplifiers. As I've mentioned in previous articles, I find them unnecessary when dealing with speakers such as these, but that's just me.
Let me step back for a second after making a statement like that one. That may not be a completely fair assessment of the Zobel and its design intent. The primary issue the Zobel is intended to address is a given speakers rising impedance in the lower frequencies and sometime, as is the case with the DX-55's, the impedance rise in the upper frequencies. Maybe it's just me, or maybe it's my choice of amps, or maybe I've become tin eared and delusional, but I simply prefer not to use them. YMMV. Fortunately, it's easy and cheap enough to try a Zobel for yourself. A Zobel is nothing more than a resistor and a cap (in series) across the positive and negative terminals of your speaker. Twenty bucks and about ten minutes will tell you whether you like the sound of it or not. Another quick Google search using "Zobel network" will get you a plethora of reading material and design computations.
As I began to break the Alerion's in, I convinced Jon to let me pull the Zobel out of the circuit. As we continued to talk and trade emails regarding the shelving filter design and its depth, Jon let me pull the entire filter out of the speaker so I could play with the resistor value. There was a very good reason for doing this (other than my affinity for taking things apart). Depending on the size of the room I choose to place the Alerion's into, I may need a deeper (or shallower) ‘shelf' to adjust the balance of these speakers to the room.
As I mentioned in the title of this article, the Alerion's are specifically designed to be used in a small(er) room. Here we are going to use the acoustic coupling and room buildups of bass in a small room to reinforce the lower end of these small horns.
The room that I'm using is actually a combination game/TV/spare bedroom that I affectionately refer to as the Grape Room (due to the purple paint on the walls). This is the room where my kids, nieces and nephews gather during family gatherings to play XBox or watch movies (I have them trained not to touch stereo gear). As it is outfitted, it is pretty barren of furniture. Just a simple Futon, a coffee table, a small flat screen TV and the stereo (of course).
The electronics I have driving the Alerion's is my Handmade Audio 2A3 custom that sports Black Gate power supply caps, Teflon coupling caps and TJ Meshplate tubes. My preamp is a highly modified Korato pre that (again) has the VH-Audio Teflon coupling caps and the OIMP output caps. My source is alternated between my trusty Bolder Modified Squeezebox and my AH! Njoe Tjoeb. I'm also using a DeZorel line filter to clean the power as best I can.
Lessons in Room Treatments
The very first thing I did was to bring in a pair of 6.5' tall plastic Fichus trees. I placed these in between the speakers to give me some much needed diffusion on the front wall. They helped to break up some (but not all) of the standing waves in the room on the longitudinal axis. Granted they are a bit large for this small room but it makes it look rather cozy and inviting. A nice plant goes a long way to gaining the WAF, honest.
The next thing I did was to place some 2" thick Owens Corning 703 rigid fiberglass boards wrapped in burlap at the first reflection points. This helped immensely but I still was getting some weirdness across the frequency spectrum. When I'd turn my head is sounded as if the singers were coming out of the closet to my left. This was due to out of phase reflections perpendicular to my ears and also the tri-corners behind and above my head. So what I did was to grab another pair of panels and placed them at the ends of the Futon. All of a sudden, everything started to snap into place. A couple of final treatments I performed were simple ones. I took some thick throw pillows and using thumb tacks fastened them to the tri corners above my head. Next, I placed a couple of throw pillows on the back rest of the Futon, right behind my ears. This further knocked down the back wall, first reflection right at my ears. These few, simple room treatments now afforded me a stereo image that had depth, width, height and performers could now be localized. The last item I should mention is the fact that I used a heavy wool blanket on the coffee table to knock down the first reflection I was picking up off the table.
Although my treatments aren't perfect, they took an unlistenable room and made it sound fairly decent. What I did (treatment-wise) could be accomplished a number of different ways that could be more acceptable to wives and family members. I'd suggest plastic or silk plants that have dense populations of leaves. Granted these things to absolutely zip for absorption, they work great for diffusion. You can also hide absorption for first reflections (or even bass traps) under tapestries, your wife's latest large needlework landscape, or nearly any porous cotton based material. I've also suggested to several people using a pair threefold room dividers covered with absorbing materials as first reflection absorbers. Those can be folded up and stashed away in a closet if need be when you aren't listening.
Each of the treatments I installed helped to eliminate reflections or buildups that cause smearing or out of phase cancellations of the sounds within this room. Each and every small room will be different. There is no way to predict what your room will need though a few commonalities will exist. Diffuse the wall behind your speakers. Treat all of the first reflection points. Depending on your room size you may need to treat the area perpendicular to your ears and possibly even some small spots behind your head (throw pillows worked just fine for me). Finally, I'd play with treatments in the tri-corners of your room. Simple, thick throw pillows can be installed with thumb tacks as a demonstration of effectiveness. A properly designed tri-corner trap will perform exponentially better but the throw pillows will give you an idea of what to expect. All of this may sound overboard but it really isn't. I'd like to also suggest reading The Master Handbook of Acoustics and learn first hand how sound interacts with room boundaries (amongst other things).
The Sound (Finally)
Once I got my room under control, the first thing that jumps out at me regarding their sound is the amount of bass that is coming from these mini-horns. Granted, I know that all of the bass I'm hearing is gain from the small room I've placed these in. Couple that with sitting at the back boundary and I'm getting darned solid bass down to the mid-40Hz range (measured and verified with my Sencore SP-295). That's pretty impressive by any single driver standards. Again, I can't say this loud enough, the bass that I'm hearing is due to the acoustic coupling of the small room I've placed these speakers in. Put them in a larger room and they will defiantly begin to roll off the lower frequencies.
The other thing I measured while I had my meter out was the treble response of the smaller DX-55 drivers. A quick run of the frequencies shows me that these little drivers are pretty darned good out to near 20kHz. Sure, they're a bit peaky in spots and have a dip or two (as do all Lowther drivers), but they hang in there fairly well all the way up the frequency scale.
Getting right down to it, the Alerion's did a nice job reproducing everything I tossed at them. The highs stayed relatively crisp, clean and well extended. I must say that the DX-55 drivers didn't have quite as much ‘air' and ‘presence' as my PM2A's, but that is what I had anticipated. When you consider the cost difference between the two coupled with the room and all of the treatments, in my eyes the DX-55's performed very well. Although the treatments are a must in a small room, they can dampen the music too much at times. This is a compromise that you might have to make if you intend on using a small room to set up listening system. This isn't an issue unique to the Lowthers; it's an issue unique to all small rooms, regardless of your speaker choice.
Throughout the midrange no doubt you are curious how the shelving filter effects the sound. When I was playing heavy percussive music I didn't notice a significant loss of clarity or dynamics. The song "Daraijin" from Kodo's Mondo Head CD sounded brilliant. Granted, the clarity and presence of the music wasn't that of their much more expensive brothers, the PM2A's in the Medallion enclosures, the overall reproduction was quite good.
For those making the first step from conventional box speakers to a rear loaded horn, there is another thing that will reach out and grab your attention, the dynamics. The Alerion's with their small 5" DX-55 driver absolutely excel at the dynamic punch that horns are so noted for. The crack of a drum, the slap of a conga or the lower octaves of the vibes or a piano are something to behold on a horn such as the Alerion.
Speaking of other things that the Alerion's do better than your proto-typical loudspeakers is the bass reproduction. Granted, you have some serious setup and treatment issues to contend with in a small room but once you have your room dialed in, these little horns can most definitely rock your world. The bass reproduction that I experienced was tight, fast and relatively accurate. That really is one of the great virtues of full range driver and horn loaded bass. The limited Xmax of the driver and high strength of the magnet start and stop the cone extremely fast. In turn you get very little overhang which (in turn) sounds like slow sloppy bass. That said the bass reproduced by the Alerion's, though deep for a 5" driver, isn't the same room filling bass of a big sub. If you might be thinking about augmenting the bass of the Alerion's, I'd like to suggest a sealed 10" sub. A sealed 10" should sound relatively ‘quick' enough as not to call too much attention to itself.
Moving on to different genres of music, classical sounded extremely nice on the Alerion's also. Violins in particular sounded well balanced and never sounded strident. YoYo Ma's cello sounded particularly sweet as he played Braham's Sonata's for cello and piano with Emanuel Ax. One issue I've grown particularly cognizant of is the timbre of the piano. Although the little Alerion's struggled a bit with the lowest of the bass registers, Ax's piano also sounded quite good. Fortunately, that is one thing Lowthers have never faltered at, midrange reproduction. Speaking of midrange reproduction, when I played a number of my reference Women's vocals, I was equally impressed at how good the Alerion's sounded. Performers like Alison Krauss, Sade and other women's voices were reproduced with good accuracy.
I did check the Alerion's behind a couple other SET amps to make sure there were no issues. The other amps I tried were my Welborne DRD 300B's and also a pair of Audio Space 6M push pull 300B's that I had in for review. As you would expect, the Alerion's performed just fine behind the other amps. In using the Audio Space 6M's, I had significantly better bass response as you would expect from a push-pull amplifer.
In The End
I'm sure that some of you may be a bit hesitant about the 93dB/W/m efficiency rating of the Alerion's but let me try to put your mind at ease a bit. Almost my entire stay with these little beauties was spent with my ultra-sweet Handmade Audio 2A3. My Deluxe Classic puts out all of 2.5 wpc. This was actually just about the perfect wattage. It gave me enough volume and headroom to drive the Alerion's to about 95dB on heavy musical passages. Much more wattage than that and it could have been a waste. During this time, I never had the urge to permanently replace my Handmade 2A3's my Welborne 300B DRD's or the even more powerful Audio Space push pull 300B amps I had here for review.
Overall the Alerion's did a great job on most genres of music I sent their way. The Alerion's did a fine job reproducing bass at all levels. Listening at very low volume levels (<75dB) was completely satisfying. Just as satisfying was music played at much higher SPL's. The Alerion's, like other Lowthers, began to show signs of life when you started pushing them. They became more dynamic, the bass got considerably better and an ‘air' began to form around the performers as they started to breathe. My puny little 2.5 watts was more than enough to perk these little babies right up in this small room.
So, if you live in home or an apartment where your space is extremely limited but you love the sound of Lowther drivers in rear loaded horns, you definitely need to check out the Lowther America Alerion's. Mate these with a fine single ended triode amp and you'll have a match made in heaven. No longer do you need a large room to house big, rear loaded horn cabinets. The Alerion's are designed specifically for a small room. They are right at home backed against a wall. Just be sure to treat your room otherwise you'll never get the correct tonal balance on the Alerion's.
Oh, and don't let the treating of your room scare you off. There are a number of companies that are more than willing to do an analysis of your room and provide you with recommendations and product to properly dampen your room. I'd like to thank Jon VerHalen at Lowther America for letting me play with the Alerion's for so long. I had loads of fun living with them for these past few months and I'll definitely miss them when they are gone. You should check them out if you get a chance.
Driver: Lowther DX-55 (as tested) or CX-45 operating in full range
Frequency Response: 70Hz to 20kHz
Nominal Impedance: 8 ohms
Power Handling: 1.5 to 100 watts
Overall Dimensions: 40 x 8.5 x 15 (HxWxD)