July 5, 2012

Reverb time

One useful feature of REW is the ability to measure reverb time. Here are 3 rooms compared:

Red: Pixelplay's room with Linkwitz Orions - a large room open to other spaces with glass and bricks, minimal treatment on the rear wall. See room >

Blue: Earle Weston's room at the Melbourne hifi show. A small hotel room with no treatment, concrete floor, carpet and some solid party walls. See room >

Orange: My room with 3 large bass traps and prototype point source horns.

You can see that with my room, the reverb time is lower due to the much larger amount of absorption used and the size of the room. It is consistent with high frequency energy only slightly diminished and the lower midrange starts to drop down, which explains partly why this region sounds very clean and dry, the bass traps are doing a great deal in that region. For the sake of a more consistent reverb time, and in the interests of perfectionism, I might add membranes to the traps. In fact I have done just that since taking this measurement. Some may prefer a little more reverb for a music system, but in a small room it's generally better to have it slightly dead than have a more coloured room. The constant directivity of the horns is also a factor in getting a consistent reverb time - there is less reliance on room reflections and the response is more "speaker dominated."

Earle's show room is more like many will be familiar with, where the midrange is getting more boost from room reflections. Carpet and furnishings are reducing the top end reverb, but aren't thick enough to work lower down, so you see the uneven reverb. Selective treatment in this room could pull down the midrange but preserve the top end. As it stands, it was a bit coloured and for critical longer term listening would need some attention.

Pixelplay's' room shows a similar reverb but at a higher level. The use of a dipole speaker with a reflective front wall is part of what is seen here. The space is open with a mezzanine above and openings to a space behind the room and there is a high ceiling.

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