It's been a while since we had a new project on the board, so if you don't mind, I would like to show you the speakers I've been working on for the past two years. I call it simply the B3 project. I took these to DIY Atlanta unfinished in summer 2009 and they were well received, tying for first in the unlimited class. I'll explain the name later, but first, some pictures and a quick description of components.
This is not a small speaker. As you can see, this is a four foot tall, dipole hybrid. As such, they have to be pulled away from the back wall so that the front is about two and a half feet out. It uses some fairly standard DIY drivers: The 8" Dayton RS-225S-8, the 6" Dayton RS-150S-8 and something a little different, the 1" Seas 27TBFC-GTV shielded metal dome. The total cost for drivers and crossover components is around $550 for the pair - not cheap, but not terribly expensive either.
You can see from the first picture that I still have a CRT type TV, so I chose all shielded drivers. I probably didn't need to, given the distance to the TV, but I also wanted to make use of the flatter low end of the shielded tweeter vs. the standard 27TBFC. I also have a center channel in the works and I wanted to use the same driver. More on that later.
Despite its somewhat standard driver lineup, there are some suttle refinements. First, the drivers are mounted so that their acoustic centers are very closely aligned. The wooofer is mounted on an extended front baffle and the tweeter is rear mounted using waveguide loading. These two details match their ACs with the mid on the main baffle.
Something I did that not everyone will agree with is that I used first order electrical crossovers for both the woofer-mid at 250 hz and mid-tweeter crossover at 2000 hz. I also used notch filters as needed for the metal drivers. I'll discuss more about the crossover choices later, but I found that all drivers in phase sounded much better than anything else I tried. Here is the working crossover. I have some more testing and there are two small areas I want to improve, so don't consider that a finished design just yet, but I don't foresee any changes other than modifying values on the existing components. The minimum impedence is over 5 ohms, so any amplifier can drive them.
And finally, here is the raw ungated, in room, 4 meter measured frequency response. I used ARTA and a calibrated microphone for this, and I also showed the response with and without my sub.
That's it for now. In following posts, I'll walk you through my design decisions and construction details. For those of you that are a little gun shy about designing your own crossovers, I'll show you what each part in the crossover does and how I arrived at the values. It's not always textbook, but you will at least see why I did what I did.
Enjoy
-Bob
The normal DIY disclaimer applies: This design is free for non-commercial use. Commercial use requires my permission.
This is not a small speaker. As you can see, this is a four foot tall, dipole hybrid. As such, they have to be pulled away from the back wall so that the front is about two and a half feet out. It uses some fairly standard DIY drivers: The 8" Dayton RS-225S-8, the 6" Dayton RS-150S-8 and something a little different, the 1" Seas 27TBFC-GTV shielded metal dome. The total cost for drivers and crossover components is around $550 for the pair - not cheap, but not terribly expensive either.
You can see from the first picture that I still have a CRT type TV, so I chose all shielded drivers. I probably didn't need to, given the distance to the TV, but I also wanted to make use of the flatter low end of the shielded tweeter vs. the standard 27TBFC. I also have a center channel in the works and I wanted to use the same driver. More on that later.
Despite its somewhat standard driver lineup, there are some suttle refinements. First, the drivers are mounted so that their acoustic centers are very closely aligned. The wooofer is mounted on an extended front baffle and the tweeter is rear mounted using waveguide loading. These two details match their ACs with the mid on the main baffle.
Something I did that not everyone will agree with is that I used first order electrical crossovers for both the woofer-mid at 250 hz and mid-tweeter crossover at 2000 hz. I also used notch filters as needed for the metal drivers. I'll discuss more about the crossover choices later, but I found that all drivers in phase sounded much better than anything else I tried. Here is the working crossover. I have some more testing and there are two small areas I want to improve, so don't consider that a finished design just yet, but I don't foresee any changes other than modifying values on the existing components. The minimum impedence is over 5 ohms, so any amplifier can drive them.
And finally, here is the raw ungated, in room, 4 meter measured frequency response. I used ARTA and a calibrated microphone for this, and I also showed the response with and without my sub.
That's it for now. In following posts, I'll walk you through my design decisions and construction details. For those of you that are a little gun shy about designing your own crossovers, I'll show you what each part in the crossover does and how I arrived at the values. It's not always textbook, but you will at least see why I did what I did.
Enjoy
-Bob
The normal DIY disclaimer applies: This design is free for non-commercial use. Commercial use requires my permission.
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