Sunday, July 23, 2006
Crank Me Up Before You Go Go
Long story short, Palila now has her dad's old Bang & Olufsen Beomaster 1900.
This was/is a stellar piece of audio equipment from the late 1970's. We've had it to the repair shop having it gone over (the output stages refused to work for me), and we should get it back here in the next couple of weeks.
In the mean time, I've been building speakers for the beast. I wish I would have taken pictures of the construction process, but have just been too busy trying to get it done. Maybe Palila will post some pictures of them on her blog someday.
So why did I make speakers rather than buy them? Well, the B&O system is designed to provide an output to 4Ω speakers and most speaker today for the home are of an 8Ω design. Yeah, you can hook up a set of 8Ω speakers without an issue (not true in the reverse direction - aka hooking 4Ω speakers to an amp designed to drive 8Ω speakers - due to the potential of overheating the amp), but you get more performance out of the amp by actually matching the driver and the load.
I purchased a set of Polk component speakers for a car (because car speakers are typically 4Ω) and built boxes. I bought the Polk speakers because they were around the price I wanted to pay and had the electrical characteristics I wanted. I had to call Polk to get some of the specific mechanical characteristics of the speaker and then use an online program to crunch the numbers for the box size and port length. I just followed some simple design guidelines (like thickness and type of material, and dimensional ratios) and let the program figure out the rest.
It took quite some time to build the boxes. But, I followed the years of experience I have from building stuff for cars, and the speakers turned out great. I had to get stuff to build them from all over. The MDF, screws, screw back things, and sheet rock screws came from Lowes. The terminals came from Radio Shack. The filler material and ports came from Cruthfield. The Bondo and fine grit sand paper came from AutoZone. The stoppers I used for feet, rough sand paper, electric sander, and spray paint came from Home Depot. I also made quite a mess in the basement utility room doing all of the sanding and painting (it was too hot to work outside).
Once I had them built I tested them using my old Sony Dolby Pro Logic home receiver. Yeah, this is one of those amps I mentioned earlier that isn't supposed to connected to 4Ω speakers, but I was careful to watch the temperature of the amp (and it got freaking hot because I was cranking it like crazy). These little speakers sound pretty damn good! I was really surprised. The boxes seem way too big for the speaker, but then again I bought a high quality speaker with really good mechanical characteristics (aka. they have the ability to move quite a bit of air in a very controlled manner). They really kick and even with low bass they don't over travel and distort. I am still surprised. But, like I said, I followed all of the rules (there is no dimension that is 2X greater than any other dimension, the MDF is thick and everything is wood glued and screwed together, the port isn't oversized, and I used filler material). This just goes to show that those one-size-fits-all speaker boxes that you can buy for your car, or simply installing speakers in a door with no concept of what the air mass in the door is doing, is really less than optimal.
This was/is a stellar piece of audio equipment from the late 1970's. We've had it to the repair shop having it gone over (the output stages refused to work for me), and we should get it back here in the next couple of weeks.
In the mean time, I've been building speakers for the beast. I wish I would have taken pictures of the construction process, but have just been too busy trying to get it done. Maybe Palila will post some pictures of them on her blog someday.
So why did I make speakers rather than buy them? Well, the B&O system is designed to provide an output to 4Ω speakers and most speaker today for the home are of an 8Ω design. Yeah, you can hook up a set of 8Ω speakers without an issue (not true in the reverse direction - aka hooking 4Ω speakers to an amp designed to drive 8Ω speakers - due to the potential of overheating the amp), but you get more performance out of the amp by actually matching the driver and the load.
I purchased a set of Polk component speakers for a car (because car speakers are typically 4Ω) and built boxes. I bought the Polk speakers because they were around the price I wanted to pay and had the electrical characteristics I wanted. I had to call Polk to get some of the specific mechanical characteristics of the speaker and then use an online program to crunch the numbers for the box size and port length. I just followed some simple design guidelines (like thickness and type of material, and dimensional ratios) and let the program figure out the rest.
It took quite some time to build the boxes. But, I followed the years of experience I have from building stuff for cars, and the speakers turned out great. I had to get stuff to build them from all over. The MDF, screws, screw back things, and sheet rock screws came from Lowes. The terminals came from Radio Shack. The filler material and ports came from Cruthfield. The Bondo and fine grit sand paper came from AutoZone. The stoppers I used for feet, rough sand paper, electric sander, and spray paint came from Home Depot. I also made quite a mess in the basement utility room doing all of the sanding and painting (it was too hot to work outside).
Once I had them built I tested them using my old Sony Dolby Pro Logic home receiver. Yeah, this is one of those amps I mentioned earlier that isn't supposed to connected to 4Ω speakers, but I was careful to watch the temperature of the amp (and it got freaking hot because I was cranking it like crazy). These little speakers sound pretty damn good! I was really surprised. The boxes seem way too big for the speaker, but then again I bought a high quality speaker with really good mechanical characteristics (aka. they have the ability to move quite a bit of air in a very controlled manner). They really kick and even with low bass they don't over travel and distort. I am still surprised. But, like I said, I followed all of the rules (there is no dimension that is 2X greater than any other dimension, the MDF is thick and everything is wood glued and screwed together, the port isn't oversized, and I used filler material). This just goes to show that those one-size-fits-all speaker boxes that you can buy for your car, or simply installing speakers in a door with no concept of what the air mass in the door is doing, is really less than optimal.
# posted by chilort @ 6:09 PM 
