[hdspeakerman]

Don,
Congrats and good luck with your new enterprise!

[dcbingaman]

The LDW was designed to work with the LRS, but it can be used with any panel speaker including the bigger Maggies, and potentially the Quad electrostatics, although it will play much louder than the Quads can manage.  The DSP in the SPA 250 DSP amp is quite capable and can be adapted to whatever crossover characteristics you desire.  Right now we are using 24 dB/octave slopes in the digital domain and keeping the woofer and panel in positive phase.  The open baffle woofer requires a unique EQ to get flat response in the room.  I started with Siegfried Linkwitz' s EQ curves and went from there - they were pretty close.

The DSP is programmed with a great interface that is accessed via USB port using a PC, but it also has a small alpha-numeric display built in the the plate with a multi-function knob to allow for matching the gain of the high pass amplifier and the efficiency of the panel speaker to the woofer using a simple iPhone based Real Time Analyzer.  The DSP also can time-sync the woofer and the panel so that the wave comes out simultaneously from the port and the panel.  This is a big advantage.

[dcbingaman]

One other point not obvious from the photos - this are true dipole woofers in that the front of the driver faces rearward and radiates out of the back of the cabinet.  The back of the speaker radiates out of the forward-facing port with is about 35% of the area of the 10" driver aluminum cone.  The port impedance provides about a 3 dB gain to the front wave reducing the amount of EQ required, but the system still acts as a dipole and provides the same radiation pattern as a dipole panel speaker, with ZERO cabinet resonance.  The DSP allows a time-sync between the panel and the woofer so that the wave emerges in sync and in-phase with the panel output. 

The result is seamless bass.  After a couple days of listening and tweaking I can say that Wendell Diller is right, a dipole woofer woks MUCH better than a general purpose subwoofer with the LRS speakers, because of the radiation pattern and the lack of any cabinet resonance.  I have never heard standup bass sound better on any speaker, including my Vandersteen Quatros which are integrated with a 5-speaker Audiokinesis SWARM distributed subwoofer array.

[dcbingaman]

The LDW DSP calibration is done.  The results are provided below.  The LDW's extend the LRS low end flat down to 27 Hz (the Dayton Audio free air resonance frequency) with a dynamic DIPOLE woofer.  All it takes is a 250W amp, a 600W dynamic woofer and digital signal processing courtesy of Dayton Audio. 

Have NEVER heard string bass sound as realistic in 40 years as an audiophile, including many of the BIG speakers.  The solution is also DIRT CHEAP.  The speakers are headed out on a listening tour west and then east but will be back this fall.  When this COVID-19 catastrophe is over we'll get back together at Casa de Binger for beers, Cyrus Chestnut and a new product introduction, the VPE Aerospace Little Dipole Woofer (LDW) built especially for the magnificent Magnepan Little Ribbon Speaker (LRS).  Bring your checkbooks. LOL !

[sturgus]

Kool!!! Thinking of buying a pair of LRS myself. How much will a pair of the woofers with DSP cost to build?

[dcbingaman]

Great question, Sturgis.  VPE can build a set for you, but haven't set a price yet.  I'll PM you with cabinet, driver and amp/DSP specifications and costs.  They are relatively affordable compared to high-end subwoofers.

[dcbingaman]

The LDW Model 1's are now in production.  $795.00 for one or $1495.00 for stereo pair.  Here is some pics and a story !!

[emailtim]

I have a couple of observations/questions if you don't mind.

This looks more like a U-Frame with 1 side tapered, longer D and turned around backwards than the Nelson Pass's SLOB project (e.g. no large front L/R baffle, different single driver orientation, no force cancellation).



A U-Frame has a cardioid response on the driver side.  The OB/dipole cancellation happens at the back port. 

Since the U-Frame is turned around backwards, the cardioid response would appear to be firing backwards towards the front wall, not towards the listener.



The cancellation at the Maggie interface may reduce any force on the Maggies.

Can you describe why it is NOT a tapered U-Frame and why it is a SLOB ?

Also, can you please clarify if and specifically what parts Nelson Pass has designed on this project ?  There appears to be some question/confusion on the web if he was directly involved in designing it or not or if it was inspired by one or more of his other projects (e.g. your plexiglass speaker clone).



https://www.stereophile.com/content/gramophone-dreams-26-nelson-pass-harmonic-distortion-page-2




Thanks much.

[dcbingaman]

The port is 1/3rd the size of the driver and has a higher acoustic impedance than the woofer face - hence it has higher velocity and about 3 dB greater output than the woofer front face which faces the wall.  If you look at Pass's SLOB design it is quite similar.  The front face of his horizontally oriented Eminence driver feeds the front-facing slot which is isolated by the baffle and the sidewalls from the driver open backside.  In our case we use the back of the driver to feed the slot and the front of the driver radiates rearward. 

It works and Pass approves the design.  The shape of the cabinet is designed to match the Maggies on stands and we do indeed use the Maggie panel as our baffle board.

We would be happy to sell you a pair for your panel speakers !  You'll love them.