This has been quite a ride over the past half dozen years or so. It all started when I decided to take on a simple 2A3 amp as a review just after the turn of the century (how weird does that sound?). At that time, my Adventures in High Efficiency started with a simple pair of vintage Lafayette Goodman 15-inch coaxial drivers and that SET amp. After enjoying that system for a number of months I knew that there was more to be gained, not only in clarity but that single ended magic we all so often read about. Not long after, I made a serious investment in a pair of premium high efficiency drivers, the Lowther PM2As. This was where the hook got set.
When I first received my PM2As, I was warned that there was going to be an extended break in time. Since I hadn't built my Medallion cabinets yet, I tossed together a pair of Martin King's MLTLs (mass loaded transmission lines). These cabinets were an extremely easy build. I think I had all of about eight hours into them and they were up and playing. When I first got them going (early on during the break in process), I used a notch filter to help tame the break-in peakiness of the PM2As. As time wore on and the pale yellow paper cones began to loosen, I found the need for the notch filter was lessened. Martin's design was actually quite good and it allows a person to use the Lowthers in true single driver configuration. Overall the sound was fairly even top to bottom. Granted they we limited to about 40Hz if you corner loaded them but for many, that is just fine.
Speaking of corner loading, most of the way through the PM2As break in process, I finished my Medallion cabinets. These added a whole new dimension to the Lowther sound. Though many people love the sound of the Medallions as a stand alone full range speaker, I couldn't live without the last couple (or three) of octaves of bass. Corner loaded they sounded fairly decent but for my music of choice, I really wanted deep solid bass, and lots of it. I give all the kudos in the world to Lowther and Jennifer Crock as the Medallions did midrange and midbass dynamics like no other speaker.
The next major step I took in my journey was when I had the brainy idea to bi-amp and actively crossover the PM2As using my 15-inch Goodmans to fill in the bass duties. This time I knew I was really onto something. At the time I was using my Audio Research AC-3 (tubed) active crossover. Driving the PM2As was still my Handmade Audio 2A3 Deluxe Classic and driving the Goodmans was a pair of Antique Sound Labs Wave 8s. After playing with numerous crossover points, I finally settled on crossing the two drivers at 100 Hz. That was where I got the most seamless transition between the two. I lived with this basic setup for a number of years but the rear loaded horn design of the Medallion just wasn't as seamless as I wanted it to be when mated to the Goodmans.
Then, on a trip to Chicago to see a rare USA concert by the Esbjorn Svensson Trio, I stopped by Jon Ver Halen's house. Jon is the distributor for Lowther in North America. He had been experimenting with Dick Olsher's Basszilla open baffle design. Jon had mounted a pair of PM6As in an open baffle and rolled a 15-inch Eminence in a ported enclosure below it. Jon was passively crossing the Basszilla's. As we sat and listened to some vinyl, I was in absolute awe of what I was hearing. The Basszilla's provided a completely different sound compared to the Medallions. The sound was big, open and spacious and had tremendous focus. They reminded me of the soundstage that Maggies and Innersound's throw. See, before I got into SETs and Lowthers, I was tri-amping and actively crossing over a pair of pair of speakers that used Carver ribbons on the top end. I'd been listening to that system for a number of years so the huge soundstage was like welcoming home an old friend. Again, I saw the next path I needed to travel.
When I returned from that trip, I immediately constructed a make-shift baffle and attached it to my Goodman cabinets (which were corner loaded at the time). Though I could hear similarities to Jon's Basszillas, I found mine were too close to the head wall. Trouble was that when I pulled them out far enough to take advantage of the open baffle design properties, the bass rolled off too hard. Big vintage woofers tend to like large cabinets and either head wall or corner loading to produce deep solid bass. So to get decent bass my next step was to build a temporary stand just for the Lowther baffle. Doing this let me move the Lowther OB's out into the room where they could breathe and at the same time let the Goodmans stay against the head wall where they were their happiest. This turned out to be the ticket. The soundstage opened up and the image improved, depth increased dramatically and the deep bass came back and paid off in spades.
Of late I've been listening to my 15-inch Altec 416-16Zs with Alnico magnets as the woofers for this system. I've got these mounted in a pair of vintage Richardo Lynn furniture grade cabinets that were originally built as Karlson cabinets. They originally had a pair of Pioneer PAX-30 coax drivers in them. As much as I tried to like the sound of this particular pair of Karlsons, I couldn't wrap my head around their sound. Since the cabinetry was beautifully done, I decided to yank the drivers and gut the cabinets of the Karlson couplers. After measuring the Thiele/Small parameters on the Altec 416s I found the cabinets were almost perfectly sized for my Altecs so I installed a fair amount of bracing and then began playing with the port tuning and stuffing. They turned into a fine looking pair of vented bass reflex cabinets. In fact, for a year or so I used these bass bins as the lower halves of my (almost) Altec A7s. I sat my Altec 511 horns (with the 802D drivers) on top with the modified Altec N500 dividing network performing crossover duties. Very cool vintage sound that I can still partake in when the mood strikes me.
So what is the bottom line on the Altec 416s as woofers compared to the Goodmans? In a word, unbelievable. The Altec's are hands down so far superior of sound to the Goodmans there is no comparison. I can't believe it took me so long to make the switch since I've had these for almost four years. As tight and defined as the Goodmans bass was, they simply didn't have the Xmax that some of my music demanded. I could hear cone breakup and distortion when I pushed them into heavy SPLs. The Altecs, on the other hand, don't even break a sweat when you push them hard. They just play louder. Another added benefit was they brought a bit of mid-bass warmth to the game that the Goodmans didn't have. Now when I lean on the volume knob on a bass heavy song, the whole house shakes like crazy. I haven't had this kind of bass in the house for a long, long time. This isn't loose and sloppy bass either. It is clean with zero overhang, extremely well defined with proper harmonics and yet has that dry slam that is almost indicative to a horn loaded bass. This is the kind of bass that you could perform CPR with. The Altecs aren't just about shear SPLs either. As I mentioned the 416s provide an extremely tuneful and harmonic rich bass range in my enclosures which are 5.5 cubic feet and tuned to 20 Hz. Something else that is really cool is that unlike some woofers I've heard that don't come alive and actually start producing decent bass until you turn them up to moderate levels, the 416s load the cabinets and produce rock solid, deep bass even at very low SPLs (read=late night quiet listening).
Now some of you might be thinking, hey with the woofers corner loaded and the baffles are well out in the listening space, doesn't that mean there is some sort of time alignment issues? Well, you'd be correct in that assumption…to a point. If you dig a little deeper into time alignment and audibility you'll find that the human ear is less sensitive to misalignments at lower frequencies. In fact I've seen studies that say that at low frequency misalignment is inaudible out to around 25ms. In my case the corner loaded woofers sit about four feet behind the plane of the OBs. According to my calculations, that works out to be a 3.5ms delay using 1127.92 ft/sec as the speed of sound at 70 degrees Fahrenheit. Basically that 3.5ms delay is pretty much inaudible. Then you need to take into consideration that since the Lowthers are on an open baffle and radiating backward and the sound wave for the mids and highs are bouncing off the same wall that the woofers are sitting against, the likelihood of hearing timing issues is even less of a factor since we've got reflected and delayed sound coming from all over the place. It's just the nature of an open baffle speaker. No doubt someone who is reading this will dispute these findings to their death and claim I'm deaf (or close to it). That's fine but until that same person has parked their butt in my listening seat in my room and actually listened rather than conducting the typical thought experiments I read so often on forums, I (personally) would discount everything they type regardless of how logical it may sound.
Sorry for getting sidetracked.
When I first moved the Lowthers from the Medallion cabinets to the OBs, their character changed pretty significantly. Much of the huge mid-bass and midrange dynamics I experienced with the back loaded horns were all but gone. But the more I listened, the more it became clear, though the big dynamics were cool, they weren't real. The PM2As residing in an open baffle gave a more natural sound and flow to the music. Far more like what I hear when I go see acoustic music performed live (which is quite often BTW).
Pulling my make-shift baffles out into the room and leaving the woofers corner loaded showed some serious promise. With the temporary baffles in place, I began experimenting with “wings" and “beards". Essentially what I was doing was expanding the baffle area to give a lift (or boost) to the lower midrange and upper mid-bass frequencies. I did everything from installing wings on the side of the baffle to extending the baffle to the floor creating a beard. These wings were nothing more than cardboard or rigid plastic. I wasn't overly concerned with these things being pretty or overly rigid during this part of the experimentation phase. I just wanted to hear the lift I'd get by extending the baffle surface. This proved to work pretty well.
By the time I actually started to finalize my design plans for my OBs, my Lowthers probably had the best part of 5000 to 6000 hours on them. Needless to say they were completely broken in. All of the shrill highs and break in nasties were completely gone. That said, anyone who has listened to and knows Lowther PM2As knows they are still just a tad forward sounding (read=a slight rise in the frequency response at about 2.5 kHz).
I wanted to tame this somehow without using a notch filter. Anyone that has read my drivel over the years knows I absolutely abhor caps, resistors or coils in my signal path regardless of what their purpose is. Though I've played with a number of passive notch filter designs over the years, each and every one has sucked the life right out of the music. In turn, I've done everything I can to avoid using them. The same holds true with this baffle design, I wanted no part of the vampiric baffle step compensation networks so I needed to figure a way around using them.
If you notice in the pictures, my drivers are offset from the centerline of the baffle. In this position on the baffle, the offset helped to minimize the baffle gain in that 2k range. I didn't cut dozens of baffles in an attempt to find the best position for the driver, what I did was download a little program called Edge which estimates the baffle gains at a given frequency based upon the size of your driver, width and height of your baffle and finally (and most importantly) the position of your driver. The Edge simulation program is quite easy to use and from what I can hear, fairly accurate in its modeling.
I chose acrylic as my baffle material of choice. One of the reasons I chose acrylic for the baffle besides its very low resonant frequency was that with a baffle this size, it was going to look pretty obtrusive in my listening room. Granted, my listening room is larger than most at 38'x15' but with a room this size, a solid wood baffle would be too visually intrusive but that's just me. Besides, the acrylic is just plain cool looking.
The base of this open baffle design is nothing more than 0.75-inch MDF with a 1 x 2 inch red oak wrapper around the outside. I sized it to make sure the baffle wouldn't tip over if somebody knocked into it. Around the edge of the baffle, I wrapped it in more 1 x 2 oak. In both the base and the baffle wrapper I routed a slot to keep a grip on the 0.75-inch thick acrylic baffle. In order to rigidly support the acrylic baffle I cut some more 1 x 4 red oak and installed a couple of knee braces off the back side of the baffle. The finished product ended up more rigid than I was hoping, which is a very good thing. To give it a nice finished look, I used a round over bit to soften all the exposed edges. After that it was a simple matter of some stain to darken the wood and numerous coats of a spray on urethane semi-gloss finish to match the rest of my DIY equipment racks and Welborne DRD amps.
As you may or may not be able to see in the sketch below, the physical dimensions of the baffle are:
Width = 15"
Height = 53"
Vertical Centerline = 37"
Horizontal Centerline = 5"
Circumference for the PM2A = 7.48"
Granted, I modeled (more like approximated) this for the frequency response of the PM2A. If you are looking to do something similar for a different model of Lowther driver, this offset design should work fairly well as the frequency rise of a number of Lowthers are either at or near 2500Hz. Then again, if you play with the computer program Edge, you may find that a different baffle and offset dimension look (or sound) better to you. If so, go for it. There are dozens of ways to skin this cat. Oh, and don't get hung up on using acrylic, plywood or some other material will work just fine. Remember, we are only asking for 150Hz out of this panel which means little if any sympathetic panel ringing from the panel material. I only chose acrylic because of its transparency, that and I had grand ideas about lighting the edges up with LEDs buried in the base (you can see how far I got with that one).
Anyway, in my room I've got my listening seat positioned about 2/3rd of the way back into the room. It's a pretty common seating placement since you have a minimum of nodes and nulls at this position. My baffles are pulled out from the headwall about six feet which gives them plenty of room to breathe. If you've ever heard or played with an open baffle or dipole speaker like Magnepan, Martin Logan, Innersounds, Quads or other electrostatic panels, you know these speakers need lots of room behind them to sound their best. Once you find the correct position, you are in for quite a treat.
All in all the build of my acrylic and oak wrapped open baffles I'd rate an 8 out of 10 on the difficulty scale mainly due to the complexity of routing all of the oak (which is a trick all unto itself), precision cutting and fitting mitered corners coupled with the fact you need some serious woodworking tools to complete this project. You definitely can't do this one with just a tape measure, power saw and a drill. I'm lucky as over the years I've been able to amass a pretty nicely outfitted wood shop (one of my other hobbies). On the other hand, if you want to build yours out of plywood and use iron on edge tape (veneer), you can easily do this with a tape, circular saw, a jig saw and a drill. In fact, it would only take about four hours if you know what you are doing. I'd suggest this as a first run at it, and then if you like what you hear go for a cooler build like maybe black acrylic.
How Do They Sound?
As precious few have experienced first hand, when you hear the Lowther A series drivers implemented properly as I have done, they give that breath of life to music that we writers often refer to as presence. The absolute clarity of these speakers when mated to a quality single ended triode amplifier is truly breath taking. They are as timbrally accurate a speaker as I've ever heard. Granted, a new pair of A series drivers will set you back two grand (or better in some cases), I personally don't think there is a better speaker available on the market today that can cover the frequency range that the Lowther A series drivers are capable of doing. I'll take that a step further, the way I have implemented the PM2As in an OB then augmented the bass with the Altec 416s, I personally don't think there is a better, more realistic and truly natural sounding system on the planet, regardless of cost.
Read into this what you want but after finishing my latest tweaks to this setup, a couple of local audiophile buds invested in the Lowther A series of drivers and a third just scored a pair of PM6Ts (Ticonals) from Jon Ver Halen. Two of the guys are building a near identical system to what I have right down to the Altec 416s because they like the sound so much. Of the thirty or so local audio guys that have heard either this or a previous incarnation of my Open Baffle system, this brings the total to six who are either in the process of building the Lowther Open Baffles. Think about that for a second, that's 20% of a local audiophile group. As you all know, Audiophiles are a finicky lot that doesn't like to own what the next guy has. Everybody wants to have unique system…which is absolutely cool. I get it because I'm that way too. But when you look at this similar system population density, those numbers alone should tell you there is something to this. I honestly can't take credit for any of this. Between Jon Ver Halen and the Dick Olsher design, they were the ones that showed me this basic path. I only tweaked the concept a bit by detaching the baffle from the bass bin and decided to use an active crossover and biamp the system. Then again maybe just because of persistence and dumb luck I actually stumbled onto something with the detached baffle design.
Now to veer completely off course...
The first and most notorious is the infamous Lowther “shout". Back in the late 1990s, Lowther addressed this issue when they updated their design to incorporate a rolled edge on the whizzer. The old whizzer design was a raw straight edge. In turn, the old whizzer would ring like a bell at certain frequencies, namely about 2500 Hz. This is where the word “shout" entered everyone's vocabulary. With the ‘new' driver design which incorporates the rolled edge on the whizzer, the shout is absent. Now, I have to admit that there are a few drivers in the Lowther line that have a bit more zing than others but once you work your way up the line (read=spending money for a quality driver), that zing is completely absent. I have to qualify that statement…once you break in the driver that forwardness is gone. Now, during the break in process, they don't sound too nifty at all. Once the cones have had time to become a bit more pliable, they settle down dramatically. My favorites of the entire Lowther lineup are the PM2A, the PM2T (Ticonal) and the more affordable PM6A. I'm told the PM5As are pretty special sounding too but I've yet to play with a pair…one day. I said previously, these drivers, when properly implemented; breathe life to music like no other speakers I've ever experienced, bar none. They have that magical ‘presence' that so many people talk about. This is especially true when mated to a quality single-ended triode amplifier. Unfortunately, you won't fully understand until you actually experience someone who has this set up. Inexpensive Lowthers in vented boxes are just a bad idea on a whole host of levels though there are some who absolutely love them. Been there, heard that. All I have to say is, that sound doesn't represent what the best of the Lowther line offers…not even close. MLTL's are a different story because there is actual engineering that went into those designs.
The next thing is all this absolute nonsense about having to constantly (or even periodically) realign a Lowther's magnet. In the six plus years I've owned (and heavily used) my pair I've aligned them exactly…well never. I take that back, I did it once. When Jon Ver Halen sent me a pair of PM2Ts to play with, I wanted to use my cones because they were well broken in. I pulled the Alnico magnets off my baskets and installed the Ticonal magnets. In turn, when I reinstalled the Alnico's, I realigned the magnets. That was the best part of two years ago. When I did that the PM2As were not in need of realigning nor are they in need of alignment as I type (two years and at least a couple thousand music hours later). I don't rotate them either as so many talk about doing, there's no need. I've never (and I do mean never) had any issues with coils scraping in the motor assembly. I take that back, I once had an issue with coils scraping. Know why? It was because this buffoon dropped a DX55 onto a concrete floor and it knocked it out of alignment (sorry ‘bout that one Jon). In turn, I set it on my workbench, connected a little T-Amp and a 20 Hz test tone and within three minutes had it realigned. No major issue for somebody with a little mechanical ability, a boxed end metric wrench. Now, all of that said, once upon a time the Lowther cone suspension was a natural Latex surround. Over time this surround material would begin to sag forcing their owners to either rotate or re-align the drivers. In the late 1990s, Lowther updated their surrounds to the more current inverted foam completely eliminating the need to constantly perform maintenance on the drivers.
Last but not least are these people who claim that a Lowther is only good with simple music. If ever somebody needs to be ignored, it's those guys that perpetuate this absolute nonsense. These are guys who have either:
1. Listened to a crappy Lowther design and have now stereotyped all wide range drivers into one large dung heap or...
2. Are continuing their unending thought experiments and assert their completely uninformed opinions as fact. I'm here to tell you with first hand experience that Lowthers (at least my favorites of the line) sound fantastic on every kind of music. Even though I listen to lots of jazz and classical, I am a hardcore rocker at heart with heavy leanings to alternative, electronica and industrial. The PM2As excel at all of these kinds of music. The biggest reason is their coherency. You no longer have a crossover screwing with the signal. Gods' honest truth here, every speaker I've ever heard (right on up to $100,000 Dynaudio speakers), either the crossover smears the sound or there is a timbral mismatch between the mid and tweeter in some form or fashion. It's that or you have some nasty tweeter screaming and spitting at you no matter how ‘smooth' the tweeter may be considered. I've not even mentioned the vampiric artifacts of crossovers literally sucking the life and dynamics out of your music. The only other multi-way speakers I've ever heard come close to getting things right have been wide range ribbons or big panels that cross things over below 250 Hz leaving the panel to run all the way up to 20 kHz. Even then you have issues of woofer integration in some designs.
Oh, and the last thing is the thought that Lowthers are fragile. This is a misnomer also. Most people associate Lowthers with fleapowered SETs mainly because that is how most of us use them. I've had the occasion to hook my 100 wpc KT88 monoblocks to a pair of PM2Ts mounted in the Teresonic Ingenium cabinets where they were used in a true full range configuration (read: ~40 Hz to 14 kHz). Playing some extremely bass heavy music, I force fed the best part of twenty or thirty watts down their throat and found out that the Xmax listed on the Lowther spec sheet is dead wrong. The PM2Ts (and As) have closer to 5 or 6mm of Xmax rather than the 1mm listed. In that cabinet, driven by those amps, the Lowthers put out shit loads of quality bass. The trick was to corner load them and sit back towards the room boundary to get even sound top to bottom rather than trying a traditional, ‘pull them out into the room' setup. This was something others who wrote about these speakers didn't bother to try. Subsequently I was written off as "delusional"... so much for all their so called experience and wisdom in this industry.
I realize a couple of the last few paragraphs may have sounded bitter but I get tired of reading the crap that gets published about these speakers. I don't know, call me an old curmudgeon if you want but at least I've finally gotten this off my chest. What I typed isn't really bitterness, its six years of experimentation and tweaking trying to push these drivers to the limit. Unlike so many who suffer from upgraditus and the ‘flavor of the month' syndrome, I heard the potential of the Lowther PM2As and was just hard headed enough not to give up until I achieved what I feel is near audio perfection.
It is truly unfortunate that so few have invested the time and money into quality wide range drivers. The average cheap-o-phile wouldn't dream of spending the best part of a couple grand on a single pair of unhoused drivers. In turn, they try to spend a moderate amount on a less than optimal sounding wide range driver, shove it into a vented box and immediately get turned off to what is actually possible, hence all of the stereotypes regarding Lowthers. Granted, as I said earlier, Lowthers are not a full range speaker; they are a wide range speaker that covers the best part of eight octaves. Supplement the bass below100-150Hz and you now have something the likes you've never heard.
If a person were to invest $3k to $4K in a speaker pairing like a few of us are creating, they would find that it betters comparable multi-way monkey coffins costing ten times that amount. The most immediate difference is the clarity without being harsh plus there is no discontinuity between the mids and tweeters. Proper choice of crossover points and slopes between the open baffle and bass bins becomes absolutely seamless and inaudible. Everything is more open, clean, coherent and simply put... real. You no longer are listening to a recording, you are sitting in the venue with the musicians. Once you experience these simple truths, you then understand the adage, Lowthers for Life.
Though not quite perfected yet, I am so close I won't abandon this latest path I've traveled these past few years. I've still got a couple of tweaks I want to do to my Altec filled bass bins. Once I get those completed, I'll have pushed this system about as far as a person is capable. After that I may start playing with some different amps and topologies, maybe some of the newer active crossover designs like the Nelson Pass First Watt B4. Who knows, maybe I'll dive right into the deep end and try a true open baffle (with open baffle woofers).
Backpedal A Bit Shall We?
I'm sure a few are wondering why I've spend all this time typing about a pair of speakers that aren't a commercial offering. Well, they actually are…of sorts. As many know Dick Olsher offers his formula and plans for the Basszilla. That particular design will get you somewhat close to what I'm listening to right now. I would suggest investing in the A series of Lowther drivers rather than the DX or C series, your ears will be much happier in the end. Those of you who have no tools or woodworking skills can still partake in all the Lowther open baffle fun. Find yourself a local cabinet shop and have them build a pair of baffles based on the dimensions I gave you above. The bass bins aren't as difficult to design as you might imagine. Just download a copy of WinISD (a speaker box design program), plug in your favorite pair of woofers Thiele-Small parameters and it will spit out the proper box size including dimensions and the port size. Take that to your cabinet maker and he should be able to whip out a pair of woofer enclosures for not much money. If you run into problems or unsure about the calculations, tons of people on the Forums know and use that program so help is right at your fingertips.
Last Word... Honest