bill
03-25-2008, 02:12 AM
Well, the DJ speakers I got suckered into building for my son & his friends are coming along nicely. These will be used, at least initially, in a smallish party room (20 x 40, 12-15 foot ceiling).
There are two systems, each composed of a woofer cabinet and a mid-tweet cabinet. The woofers are dual HiVi F12s, the ones that were on closeout until they sold out a week or so ago. The cabinet is sized for the PE 18" x 28" grilles; it's 29.5 H x 19.5" W x 18" D. The baffle is recessed an inch from the front of the cabinet, so the front of the grille will sit flush. There's a socket on the top of the cabinet that accepts a 1-3/8" diameter tube 2 feet long. The mid-tweet cabinet mounts on top of the tube using another socket. This design gets the tweeter up about 5 feet high. I thought about a single-cabinet design like the Magna *** Laude, but it's not tall enough for the highs to punch through and I didn't want to have to put the speakers on stands. The knock-down arrangement also makes the speakers much easier to load into my wife's minivan.
The mid-tweet cabinet is half of a Podzuma (2 Dayton PA130 mids and a Pyle bullet tweeter.) I'm even using Darren's Podzuma crossover. I've made the box relatively shallow so the baffle size is as close as possible to the Podzuma's baffle; that way I don't have to rejigger the crossover for baffle step. The box is approximately 0.2 cubic feet; it's sealed, with a Q close to .7. Precise Q is not a big issue, as I plan to cross over to the woofers at 300-350 Hz using a Behringer CX-2310.
The cabinets are 18 mm Baltic birch. I can't believe what that stuff costs now! Two sheets were not quite enough to build the two cabinets, so I cheated and made the cabinet bottoms from a quarter sheet of 3/4" oak plywood from HD. This stuff has a lot of relatively thin plies, and it doesn't seem to have a lot of voids, unlike regular plywood. Each cabinet has a vertical brace that also serves to support the inside ends of the dual 3" port tubes.
The sides, top and bottom of the woofer cabinet are rabbeted and dadoed to accept the baffle, brace and rear panel. This is the first time I've used this type of construction; in fact, it's the first time I've had my Amana dado set out of the box. It won't be the last; the joinery fits so well that the cabinet holds itself together without glue. Amana thoughtfully provided the recipe for stacking cutters and shims for an 18 mm cut; it's accurate to a thousandth of an inch, based on how well the panels fit together.
The mid-tweet cabinets are also Baltic birch and are also rabbeted. I'm going to fully stuff them with Dacron fiberfill.
I'm using round Speakon connectors on both cabinets, mostly because they're sealed, they lock and I can recess them easily into the rear panels. They can also take an immense amount of abuse.
I'm using amps I already own to drive these. The woofers will be driven by an Adcom GFA-555; the mid-tweets by an old Crown D-60. Yes, this is underpowered by modern standards, but the speakers are pretty efficient, especially the mid-tweets. I may fill in the low end with my son's Quatro 15, which is in a 5 cubic foot vented box and is driven by a 240 watt plate amp.
Having heard Darren's Podzuma, I have no qualms about being able to fill the room with the D-60. With 4 ohm loads, a D-60 will put out close to 70 watts per channel. Given the efficiency of the Podzuma design and that they don't have to handle anything under 300-350 Hz, that ought to be plenty.
The Sweet 16 I'm building these for is on April 12. I'll let you know how it goes. At the moment I'm just praying for a warm weekend so I can get them painted.
Best regards,
Bill
There are two systems, each composed of a woofer cabinet and a mid-tweet cabinet. The woofers are dual HiVi F12s, the ones that were on closeout until they sold out a week or so ago. The cabinet is sized for the PE 18" x 28" grilles; it's 29.5 H x 19.5" W x 18" D. The baffle is recessed an inch from the front of the cabinet, so the front of the grille will sit flush. There's a socket on the top of the cabinet that accepts a 1-3/8" diameter tube 2 feet long. The mid-tweet cabinet mounts on top of the tube using another socket. This design gets the tweeter up about 5 feet high. I thought about a single-cabinet design like the Magna *** Laude, but it's not tall enough for the highs to punch through and I didn't want to have to put the speakers on stands. The knock-down arrangement also makes the speakers much easier to load into my wife's minivan.
The mid-tweet cabinet is half of a Podzuma (2 Dayton PA130 mids and a Pyle bullet tweeter.) I'm even using Darren's Podzuma crossover. I've made the box relatively shallow so the baffle size is as close as possible to the Podzuma's baffle; that way I don't have to rejigger the crossover for baffle step. The box is approximately 0.2 cubic feet; it's sealed, with a Q close to .7. Precise Q is not a big issue, as I plan to cross over to the woofers at 300-350 Hz using a Behringer CX-2310.
The cabinets are 18 mm Baltic birch. I can't believe what that stuff costs now! Two sheets were not quite enough to build the two cabinets, so I cheated and made the cabinet bottoms from a quarter sheet of 3/4" oak plywood from HD. This stuff has a lot of relatively thin plies, and it doesn't seem to have a lot of voids, unlike regular plywood. Each cabinet has a vertical brace that also serves to support the inside ends of the dual 3" port tubes.
The sides, top and bottom of the woofer cabinet are rabbeted and dadoed to accept the baffle, brace and rear panel. This is the first time I've used this type of construction; in fact, it's the first time I've had my Amana dado set out of the box. It won't be the last; the joinery fits so well that the cabinet holds itself together without glue. Amana thoughtfully provided the recipe for stacking cutters and shims for an 18 mm cut; it's accurate to a thousandth of an inch, based on how well the panels fit together.
The mid-tweet cabinets are also Baltic birch and are also rabbeted. I'm going to fully stuff them with Dacron fiberfill.
I'm using round Speakon connectors on both cabinets, mostly because they're sealed, they lock and I can recess them easily into the rear panels. They can also take an immense amount of abuse.
I'm using amps I already own to drive these. The woofers will be driven by an Adcom GFA-555; the mid-tweets by an old Crown D-60. Yes, this is underpowered by modern standards, but the speakers are pretty efficient, especially the mid-tweets. I may fill in the low end with my son's Quatro 15, which is in a 5 cubic foot vented box and is driven by a 240 watt plate amp.
Having heard Darren's Podzuma, I have no qualms about being able to fill the room with the D-60. With 4 ohm loads, a D-60 will put out close to 70 watts per channel. Given the efficiency of the Podzuma design and that they don't have to handle anything under 300-350 Hz, that ought to be plenty.
The Sweet 16 I'm building these for is on April 12. I'll let you know how it goes. At the moment I'm just praying for a warm weekend so I can get them painted.
Best regards,
Bill