Over the last four years I experimented with full range
drivers from different manufacturers. They all sounded flawed from muddy
midrange to rolled off the high ends & brittle whizzer-cone treble. I had
all but given up when I came across Mark Fenlon’s new Alpair 12p’s. Here was a
full range unit that had state-of-the-art technology behind it & was
competitively priced.
I read all I could about it on the forums & eventually pulled the trigger.
Once they arrived, eager as I was to try these out, I had to refrain & comply to the run-in protocol for 100 hours. So I set them up on the study desk plugged into a small amp. With a CD on repeat I let them run 24/7 for a week, gradually increasing the volume & bass. I could tell even then that these units were something special......
The day finally came when I mounted the Alpairs to an adapted Bastani baffle & plugged them into my system.
My fears from the past would be the roll-off or brittle sounding treble....but no, treble was fine even at this early stage of run-in (they take 800 hours to come fully on song). The mids were clear, dynamic & detailed. I cant comment on the bass as this was being handled by the active 18” woofer now driven by a PA amp form the Behringer stable, an iNuke NU3000DSP. This unit has built in crossover & PEQ.
The imaging on these babies was also in a different league.
I was expecting maybe my amp to struggle driving them as they are quoted as less efficient than the Bastanis, but in practice another click on the volume control & I was at my regular listening level. There were no problems crossing over with the woofer....minimal adjustment was needed here.
Over the coming months the Alpairs become more & more organic the small run-in characteristics gradually disappearing. They became smoother & more extended in the treble. I really did not miss the Bastanis, & when I switchedfrom the Alpairs to compare I really noticed how obvious having a separate tweeter was.
When I was certain to incorporate these speakers permanently into my main system I set about designing a baffle. This was my first design.
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These were manufactured by CNC in a woodwork shop from 38mm MDF to a detailed drawing I submitted. This particular woodwork shop has manufactured many of my designs and my goal with each design is to simplify. OB Baffles dont get any simpler than this.
The 18" woofer is surrounded by a simple U-frame which has the effect of increased low frequence response by a few db's. I have not gone over the top with the depth of this frame because I find after a certain point it will add resonances to the room.
I was stunned by the sound they produced, but after living with them for a few weeks in the flesh I began to ponder the cosmetics on a design that would further simplify & compact even further.
This was my second design, less than 3’ tall & 19” wide! They pack alot of punch with the 18” woofer!
Recent experimentation has been to roll off the bass signal to the full range amp. This has resulted in a much freer sound as the amp no longer has to deal with difficult bass frequencies, especially sub sonic rumble from a record.
I have to say this journey has come full circle now as the client who originally turned me onto my first experience of Open Baffle is now enjoying the latest Alpair baffle.
Now that I am happy with this design I am hoping to start converting other enthusiasts to these remarkable speakers and provide advice & a build service to those not able to do the work themselves.