Quite a few people here at RecordingReview have expressed an interest in buiding QRD Diffusors. I’m not exactly sure of the draw of the QRD serpeant, but I’ve been bitten by that snake, too. Here’s a few guesses:
- Diffusors can be just technical enough to challenge a guy who wished he designed stealth bombers.
- The actual construction chops required aren’t prohibitive.
It’s no wonder why DIY Diffusor projects are so popular.
Dumb Diffusor Thought Experiment
It won’t be long from now that we’ll be planning a new house and a new home studio along with it. Just for my own amusement, I pondered what it would take to get a 2D QRD diffusor effective down to 50Hz. I fired up QRDude and selected, again just for fun, a 43-well QRD diffusor with a design frequency of 50Hz. Go big or go home.
I expected the thing to be 12′ deep. That didn’t surprise me. The number that truly elated me was the Minimum Distance To Seating Position figure: 812.59 inches
Yes, that’s 67.71583333333333 feet.
For this diffusor to do much of ANYTHING, you need to be 67′ from the damn thing.
Granted, the definition of “anything” is always up in the air. The guys drawing the line between an effective and ineffective diffusor have the same problem as the guys trying to figure out when upgrading from an $100 mic to a Neumann U87 becomes “effective”.
Regardless, that 67′ number is enlightening. I’d be more than thrilled if I had the studio space to that was 40% that dimension. Of course, this was just a thought exercise like swimming to the moon.
Even when adjusting QRDude for a much less-impractical 300Hz design frequency, we still get a minimum distance from seating position at 135..43″. (11′). When I built my diffusors, I knew I was going to be on the low side of that, but went for it anyway. I regret it.
After recording in 100% dead spaces, highly diffused spaces, very live spaces with no diffusion, and just about everything in between, I can’t help but think that the major reason most unseasoned home recorders build diffusors has almost nothing to do with a sound. I can’t see why it’s worth fretting about whether we bust a bullet into a hundred ineffective bb’s (diffuse it) or just catch it (absorb it).
I know they use words like “oppressive” to describe a room heavily covered in Roxul. I think that’s an irresponsible use of the language and an example of extreme sensationalism when used to describe a near-100% dead room. (Actually get 100% dead requires enormous efforts.) I think “surprising” may be a better term.
I know people like to say that a diffusor will “liven” up a room. I’m still trying to figure out what they hell they are talking about. That’s not what diffusors do. Even if you really did want to “liven” up a room, according to Philipp Newel, author of Recording Studio Design, you need to cover 25% of that room in a “livening” material.
I think people believe that adding a ton of diffusors to a crappy space will suddenly make that space sound outstanding. In most cases, I’d bet people want their little bedroom to “open up” like the live rooms at Ocean Way. That’s definitely NOT what diffusors do, either.
Diffusors won’t “liven up” a room, either, unless the thing is REALLY freakin’ dead and you’ve got a few truckloads of diffusors (for a small-ish room). If you are used to hard reflections, you are going to wonder what happened when you bust those up.
- If you are using QRDude to put together some DIY diffusors, take that “minimum distance to seatig position” seriously. Its there for a reason. While the definition of “effective” may be debated, remember you are playing with a fire.
- Keep in mind this is idea of diffusion sits well, philosophically, to us humans, but the real-world, tangible benefits of the extreme investment in time to make these things is limited to a small percentage of people actually partaking.
- Don’t make DIY diffusors just because they look pretty.