Elevating My Listening Chair
My listening chair is an inexpensive Ikea Poang chair. It's comfortable enough, but the seat is low to the floor for the best sound. In addition, I am only 5' 7" tall. When I built the LX521 loudspeakers, I temporarily placed them on wheeled dollies to experiment with their lateral position and toe-in. The dollies elevated the speakers about 2" further from the floor. In this temporary elevated state, I noticed that the sound deteriorated compared to my initial listening arrangement. I assumed that the extra speaker height was influencing what I heard. It sounded as if the performer was a little too close the microphone, and that reduced the illusion of someone actually in the room singing. During the spaker positioning experiments, I temporarily placed some lumber under the chair to lift it about the same amount as the speakers on the dollies. This was in place only while I adjusted toe-in and position for a good soundstage.
The speaker dollies were temporary and are now gone. The sound did improve with the speakers back on the floor. However I was now aware of the influence of listening height and noticed that my ear level was still below the design axis. My ears were level with the center of the lower midrange driver, not the upper mid or tweeter as specified by the designer. I experimented with seating height by raising and lowering myself in the chair while listening to female vocals. This simple experiment showed that an elevation of a few inches was sufficient to improve the sound noticeably.
Because I sit fairly close to the speaker (7' 6"), the listening axis problem is apparently aggravated. Listening from further away reduces the problem. I assume that is because all the drivers are integrating nicely at further distances, and that the subtended angle between top and bottom drivers is reduced. Because of my room arrangement, a more distant seating position is undesirable.
I'm not going to get any taller, so I did two things to elevate the chair's seating position to improve sound. First, I purchased an inexpensive foam cushion from a Jo-Ann Fabrics store. Second, I made some "feet" for the bottom of the chair for an extra 1-1/2" of height. This picture shows both in place.
The foam pad from Jo-Ann Fabrics was placed beneath the chair's existing seat pad. It measures 17" x 15" x 3" uncompressed, so the actual lift will be less with someone seated.
Next, I made some feet that raised the entire chair frame another 1-1/2". They were fabricated from some leftover 2x4 pine, and some 1/8" Masonite. Nominal 2x4 material is actually 1-1/2" thick, so that limited the extra height I'd get by using it.
The 2x4 lumber was ripped on the tablesaw to match the width of the chair's leg (~2.45"), and then crosscut to make 4" long pieces. Strips of Masonite were ripped to 2.65". The short Masonite side pieces for accommodating the chair's crossbar were crosscut to be 1" and 1/2" wide. The clearance hole for the connector bolt was 3/4" diameter.
The rear of the chair leg included a cross-beam and a connector bolt. Fortunately, that arrangement made attaching the rear pads a snap-on affair. They stay in place by themselves when the chair is lifted or moved. The front pads were affixed using adhesive-backed Velcro between the chair and the pad.
While the improved seating position is still somewhat lower than ideal, any further raising of the chair will not allow me to place my feet flat on the floor. This is about as high as I can go without modifying the angle of the seat and back.
It does provide a noticeable improvement in sound though. Sitting too low with my LX521 speakers was the cause of a very slight "chestiness" in vocals, especially female vocals. This modification cleans up that problem, and moves me closer to the loudspeaker designer's listening axis specification.
This experiment also makes me wonder if the previous Plutos would have sounded any different with this taller chair. I recall sitting a little below the midwoofer level when they were the loudspeakers that I used in this room.
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