Meeting Topic: Designing a Flat-Panel Speaker
Moderator Name: Bob Schulein
Speaker Name: Richard Stroud
Meeting Location: Niles, IL, USA
The November 14, 2012, meeting of the Chicago AES Section was held at Shure Incorporated, located in Niles, Illinois. About forty audio enthusiasts (members and non-members) attended the presentation in the S.N. Shure Theater and then rotated in groups of eight into a small conference room to listen to Richard's demo of his home-made flat-panel speakers.
Bob Schulein introduced Richard by referencing their first meeting and prior collaborations, provided Richard's background and work history in audio, and concluded with a great 'matter of fact' statement: "You can't stop a guy like Dick Stroud."
Right off the bat I knew that I was going to be hooked as he started to provide an overview of the common goals in creating a music listening system. No matter what specific areas we find ourselves in — work or hobby, we are all audio enthusiasts. We may have not realized it at the time but Richard was slowly pulling us in, appealing to our curiosity as to what are the factors that contribute to either making or listening to good music.
He described several aspects of a good music 'listening system' including: it provides an 'emotional experience', 20Hz to 20kHz bandwidth, produces spatial qualities, produces an image height that is appropriate, presents a high level of realism and believe-ability, and produces a listening experience where the speakers should 'totally disappear'.
Richard then reviewed why he had chosen a dipole arrangement for his listening experience. True dipoles create a figure 8 pattern that ideally provide equal energy (or sound) dispersion off of the front of the face of the speaker as to that produced off the rear face of the speaker. By implementing an MTM (mid-tweeter-mid) arrangement of the drivers, one has greater control of the vertical directivity. He then described his specific flat-panel speaker design by noting which drivers he chose, how he placed their MTM location within the face of each speaker panel — using software, his experimenting with passive and active crossover designs, and even using a software program called 'Edge' (http://www.tolvan.com/) to optimize his panel sizes (4 feet tall x 0.7meters wide). Appealing to the true audiophile's thinking that if you want it done right, you'll have to learn how to 'do it yourself' approach, he proudly offered that he was able to create an enjoyable listening system for under $150 (for the pair excluding the laptop, USB cable, and some software).
The second half of the meeting allowed groups to rotate into the conference room and listen to the flat-panel speakers while Richard played various tracks. He encouraged people to sit or stand at various positions within the large 'sweet spot'. Even if you walked up to the speakers' center stage, you could walk past their front face and still hear incredible imaging — a listening experience that seemed to allow the flat-panel speakers to 'disappear'.
The Chicago AES Section would like to extend a special thanks to Richard Stroud for his presentation, for providing a demo of his flat-panel speakers, and for letting us in on some of his secrets of designing a great listening system.
Written By: Ken Platz