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Why We Call This a “Magic Brace”
Protects, Supports Driver and Allows Air Flow: Magic!
The below text is a transcription of the video.
Hey there, John Hunter with REL here. I always find that if I can learn more about something I’m interested in, a product I’m interested in, for example, it just helps me deepen my appreciation for what they’re doing and how they did it. I wanted to explain to you on these new HTs, we use a thing we call a magic brace. The magic brace is name that, because it does several different things well, bracing is necessary because if you don’t brace a cabinet, if you don’t damp the cabinet walls, the top, the bottom, it will boom. And when it booms, it really interferes with the ability of the subwoofer to do its job. So, just take it from me, bracing is necessary. When you’re dealing with big, expensive cabinets like we do, we can throw all kinds of things at it. Oh my gosh. When we get up to our references, we’re using marine grade 19 ply plywood that’s made out of Baltic Birch. We’re applying it here and there cause we know exactly where the residence point is. That’s hundreds of dollars just to do the bracing properly in a ref. When we get to a piece like this, the new HT 1003, MKII, where things are so delicately balanced, there’s no budget to play with, there’s no extra money we can throw at anything. We have to get more clever, which I always kind of like, I love that challenge of how do you do it with almost nothing. It’s very common in inexpensive subwoofers, just to use what I refer to as a window pane brace. It’s nothing more than a crosshatch. Looks like this, like a window pane with multiple mullions.
And what we do that’s different, and the reason I do it differently is in my very first designs, for REL, back in 2005, in the very first R series, I went along with the crowd. I had experts telling, well, you should do a window pane brace. You know, it’s a really inexpensive way to make everything better. The next time I went through, I was doing much more testing and listening on my own. I’d learned that the experts really often were well off the pace. And the testing I was doing, the window pane brace was a really noisy, obnoxious thing. So here’s what happens. You’ve got a driver, driver’s got a voice coil, it’s got a big magnet around it, all that’s great. We make ours with very large vents in the back because when you have a big, long stroke driver moving back and forth, you need to first of all evacuate that air.
You got to get the air that’s built up underneath that to evacuate. Or now you’ve got this weird little sort of unintentional shock absorber that’s resisting the ability of the cone to back and forth. Second of all, you want that air out of there. One of the primary reasons that you have vented pole pieces to get cold air in where it’s hot, where the voice coil is, and then get it ejected back out again, and then suck in more cooler air. So when you do that, if you have a standard window pane brace, which sits brilliantly, right behind the driver, right exactly. The center of that thing is usually exactly where the driver’s vent is. That jet of air hits, it splatters across that, makes some noising, and that noise, albeit greatly reduced, comes back out as distortion through the front of your cone.
We said, all right, we don’t have a lot to work with on this. How do we do this? So what we’ve got is a variation of the window pane brace that does so many things well. So instead of being a little one inch thick piece, it’s about, oh my God, I’m going to guess it’s two and a half, three inches across. So now you have these big ones. Well, how the hell does that help make anything? Now you got a really big thing, splattering. No. It comes down and it actually flows around the magnet. So there’s this circumferential section of it that’s even bigger and you’re going, good god. Now you’re making it worse and worse at this point, hunter. No, we bore a huge hole in the middle of it that’s exactly sized to the scale of the magnet that’s involved. And then we line it with soft felt. That then gets placed around the magnet, which does several things.
First of all, it’s really precisely tightly fitted to the back of the magnet. So it damps the magnet, which keeps it quieter, and it also supports the magnet during shipping. These are big magnets. We’re shipping things across continents, across countries. And so inevitably at some point, it’s going to get some rough handling. When it does, this keeps it cradled so the magnet isn’t putting sheer tension on the back of the basket. It does so many good things. The most important thing is that huge jet of air that’s coming in and out of the vented pole piece now has the entire cabinet, which is what it’s supposed to see. The entire cabinet in its damping to be able to evacuate in, tends to stay in and it’s much quieter with much lower distortion. So those are some of the tricks that we put into this keeps the cost relatively low. I mean, it’s not a huge amount of, I think we actually use HDF bracing, excuse me. And then some felt, and it just does an amazing job of supporting it, allowing that cold air to go in and out and stiffening, you know, damping all four walls of the cabinet. So that’s how we use the magic brace.