Ohh, that reminds me, speaking of the HR-1, Bob said the Buffalo Board was essential to getting the HR-1 to sound right as well. So everything you see going on here is a culmination of his experience over the years.
Quote:Awsome Job, guys!
Just one question: What determines the sensitivity ratings in the design? Is it the specs on the drivers, the air flow resistance inside the cabinets, the crossovers? all of these?
Would it be a mattter of replacing the main drivers with full-range ones (lighter/easier to be moved) but keeping essentially the same design framework?
I'm curious to know if an already successful internal air flow pattern design like this would also work with faster moving drivers, so as to increase sensitivity at the expense of low frequency response?
This is a very interesting topic (the physics of it, not the woodwork, which I admire but is completely straneous for me, I must admit.)
I'm hoping Bob can tune in and offer his thoughts, but I know he's really busy lately. I think he might be moving his shop even.
Ok, please keep in mind, I'm not a speaker designer, and my info is outdated. When I was in my early 20's I did do some designs, but technology and especially speakers has changed a lot since then...but the basic physics is still pretty much the same. Plus most of my experience is with subs, most of the airspace talk below doesn't affect tweeters.
Efficiency starts with the driver. You can't make an 88db efficient driver a 95db driver with a good cabinet design. Horns I think might be an exception to this, but there are a lot of tricks and requirements to what the driver can do, and limitations as to sound. I've heard speakers get really loud when setup in a horn, but then they sound "honky" or have "the horn sound" (in a bad way).
The airspace behind the driver is specifically tuned to the drivers. The airspace behind the driver is basically part of the suspension. If you put a driver that needs .5 cubic feet of airspace into a box that's only .25 cubes of airspace, then the suspension behind the driver is too tight causing efficiency issues and frequency issues, and probably running it hot. If you have too much airspace behind the driver, then the suspension is loose and the driver can be floppy and less accurate.
So you can't just take one driver out of a cabinet design and drop another driver in. That driver is expecting a certain airspace behind it. Will it work? Sure. But will it work *right*? Probably not, unless the specs happen to be close.
Add to all that, the ports are tuned to the airspace in the driver chamber to work with those specific drivers, and the ports and horn need to work in harmony, in the correct frequency range and pressure as well. So you have to pick drivers, design a chamber, port the chamber, and design a horn to work with the driver, airspace, and ports and all in a frequency range that's "flat".
Crap it's amazing that speakers work at all, let alone work this well. If it's done right, a lot of math is used to get you a good start, but an experienced speaker builder takes the guidance from the math, adds his experience, then builds, listens, measures, and tweaks till it's right. Hell, I think Bob said it took a decade to get the HR-1 right!
All of what I've said above doesn't even account for crossover, phase, and timing - which is all it's own complex thing.
So efficiency starts with the drivers and proper speaker design. The cabinet can eat up or enhance some of that, the crossover eats up some, and your room can enhance or eat up some. But it all revolves around what your speaker starts at. If you need 100db end product, then your drivers better be around 100db to start with.
For example, Palo and I were talking about this tweeter on the El Camino, and how different it is from the one in the 944. I do miss some of the high end extension and "air" the 944 has over the El Camino - but I'm glad to give up the slightly edgy, almost sibilant high end for the silkiness of the tweeter in the camino. But out of curiosity I started researching to see if maybe there was a better tweeter for the El Camino that would get me both that high end extension (40Khz), but still be silky, still go down to the FS of 650Hz that the new tweeters have (they are crossed over as well by the way), and still be 94db efficient or better. Six friggen hours of searching on the web, and I couldn't find anything under $350 per tweeter that was close to the specs I wanted! And even at $350 there were some trade offs. So it's pretty amazing to find all these parts and make them work together in a configuration that sounds good. The Math is only part of the trick.
As with everything, there are trade offs - so everything mentioned above, and lots I didn't, and lots I don't even know - all culminate in speaker building. This is why I didn't really get into speaker building as a career. LOL