Discovering Open Baffle speakers to me was a turning point in my hifi journey. Open Baffle speakers are, by the way, speakers that run in the open with no enclosure. Previous to that it was common for me to change the speakers every year once the boredom set in as it eventually would. It was one of my early Terminator clients that turned me onto the concept when he sent me a photo of his setup. I jokingly remarked when was he going to “finish his speakers”............?
This started me on a learning curve & I read all I could
on the subject eventually buying my clients old speaker baffles & fitting
them with Bastani drive units. The Bastanis consisted of a wide band driver/tweeter with an actively driven woofer
requiring its own sub amp..
I had the speakers up & running in no time, & doing an A/B comparison with my existing Yamaha NS1000’s I noted the OB’s contained all the detail of the NS1000’s, but presented the music as music rather than hifi, where the whole room became a soundstage.
I felt immediately at home with these speakers, & rapidly upgraded to the top of the range Bastanis, forming a rapport with Robert Bastani & eventually becoming a UK agent.
I lived with & promoted Bastanis for many years. I did many happy demos but discovered the limiting factor in their appeal was the physical size. They were big, & many of my clients felt they could not accommodate them in their listening rooms.
So my quest began to see if I could make a room friendly OB design. At the same time, I started to investigate full range drivers thinking if I could encorporate the Wideband & tweeter into one unit, that would greatly simplify design & also reduce the cost.
Please feel free to browse my clicking the Alpair & Bastani titles above the pictures for more info.
More experimentation with OB sees the introduction of my 'no-baffle' design.
Using a ladder frame wood design simplifies & reduces the cost significantly.....but more surprising is how clear & open the sound now is compared to a baffed design.
I started with my new FR discovery (PRV 5MR450) and partnered it with a pair of Selenium Neo woofers (opposite) in a conventional U-frame design.
Already this driver configuration was more dynamic than my previous Alpair/18 combo, but what would this sound like in a ladder frame?
Wow........hard to believe these were the same drivers! After re-equ'ing the woofers, the bass was so much cleaner than the baffled version. And the other surprise was a total elimination of room modes. Bass was even throughout the room. Imaging was also greatly improved, perhaps because the FR unit was positioned further forward away from the frame.
The woofers are facing 'the wrong way' and this was simply to facilitate mounting. I did later actually switch them to face the listener but dynamics and slam were reduced.
I also noticed with the ladder frame more vibration found its way to the floor. Now I happen to like 'feeling' the bass up though the sofa and maximised this effect with 4 delrin adjustable feet to make better contact with the floor. In my case this happens to be wooden laminate on wooden joists, so not sure what the effect would be on concrete.
Of course, my ladder frames were pretty tall. To try to improve the WAF I came up with a design which stacked the woofers, and cleared space behind the FR to allow free reflections from the rear.
This worked really well, but I wasnt too happy with the aesthetics around the FR.
I chopped the top of the frame off & devised a new bracket to hold FR in place. Imaging was now very 3D and stunning.
A few of you may have noticed the woofers have changed from the Neos....another experiment of mine and very successful.
For the final iteration of this design, I reversed the positioning if the rear woofer to face forwards and reversed polarity. This made mounting alot easier, but also extended the bass. These compacts really rock down to 20hz and need very little eq in OB configuration due to the specification of the woofer.
Updates to ladder frame:
Also, a huge amount of bulk and low WAF
Evolution continues of this speaker concept, now ditching the ladder T frame completely. The woofers are bolted together as one unit and supported by their magnets on a simple cradle frame. Nothing is stressed in this construction, and all the vibrations have a direct path down to ground via the supporting end pieces.
The FR units are still supported by poles, but these are now carbon and bolted to the frame through a space between the woofers. Very few vibration now reach the FR's and I was able to dispense with the rubber isolation bobbins.
Construction could not be simpler. All the parts supporting the FR's are available off-the-shelf. Only the cradle needs to be fabricated. I used 40mm Iroko worktop. The end piece matches magnet diameter, bit a simpler V could be used. This is the best sounding iteration yet!
Evolution of this journey........
Scaffold Frame, No Baffle OB Loudspeakers! May 2017, currently undergoing testing........