It seems to me like a good time to share some info about a project we have been working on sporadically for the past few months. It started when PB was still working for us more or less full time. He put together a speaker setup based upon some design parameters we agreed upon. The initial requirements were that it be efficient enough to perform extremely well with our more powerful amps and reasonably well with our lower powered amps. It also had to be able to work with a single amp, i.e. it could not be a multi-amp-only design like my reference system.
PB built a roughly 1 cubic foot vented cabinet with two 8" woofers and a fairly inexpensive dome tweeter. The woofers showed a lot of promise, the tweeter not so much. The next iteration replaced the dome tweeter with a horn loaded planar tweeter, and PB and PJ worked out a rough cut crossover for evaluation. At this point the design started to sound like something we could refine into a very listenable setup.
Our new tech Kelvin spent some time getting our clip lead kludged crossover assembled into a more manageable form earlier this week. We've been doing some fairly intensive measurement and testing of different aspects of the design since then, analyzing the advantages and learning to work around the compromises that one finds in every speaker design. PJ, Josh, Kelvin and I were all focused on this project the last couple of days and made a great deal of headway in the process. As it stands now (and subject to change) it looks like we are talking about a tower speaker about 4.5-5 feet tall, about 9" wide and maybe 10-13" deep. There are two woofers that should be able to get down to around 40 Hz when using an amp with a damping factor in the range typical for zero global feedback single ended tube amps. The sensitivity should be in the 93.5-94dB@1W1M range. We've tested this prototype with every amp we make and they all work quite nicely with it. With a Kaiju the speaker ROCKS, loud and clean. I had to run the levels fairly high to listen for any oddball resonances we need to address and at one point I noticed Josh had earplugs in.
The passive crossover will be somewhat complex. This is a necessity to get the speaker to perform at a level similar to my reference system. Currently it features the crossover elements, a zobel for the woofers and a notch filter. We are also looking at ways to improve the HF extension of the horn a bit and to employ some baffle step correction.
Yesterday we nailed down exactly how much padding the very efficient horn tweeter needs to match the woofers. That allowed us to remove an adjustable pad we had in the crossover, and the fixed pad requires us to slightly adjust the crossover component values the keep it at the desired frequency. We will get this reconfigured next week, and then our next step is to move the drivers into the larger cabinet and verify the bass performance of the box and the effect of BSC.
Release date - I don't know, but definitely after we finish the design and not before.
Price - maybe $1500-2K? not sure yet. Depends greatly upon the cabinet design and material and the final crossover configuration and component cost.
To be clear, this design is intended to be a setup for those who want speakers that will be truly optimized to work with our premium amps in a living room sized environment, and who don't mind putting a kit together. It's not intended to be a compact setup, or a nearfield rig, and it's not intended to be a finished product. For those requirements I highly recommend Blumenstein Audio products. Clark has an excellent handle on that aspect.
Unless we come across some heretofore undiscovered, insurmountable obstacle, I will post here when we have any more news about the development of this speaker. Cross your fingers - we've been searching for this grail for 20 years!
« Last Edit: September 05, 2017, 03:50:00 PM by Doc B. »
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.
