B&C 8NDL51 in a 3 way

[mayhem13]

So here goes my first Speaker build. So many rave reviews of this driver i think it's the way to go. I plan to use it with 2 Dayton RS 8" woofers(4 ohm) crossed at 500hz and a Morel MD30 dome mounted to a waveguide (as in ZaphAudio setup) crossed at 1.3khz. The woofers will be in a ported chamber tuned to 45hz and the B&C will be in a sealed chamber acrylic sphere mounted above the tweeter in the waveguide. Any pro's or con's on this design? P.S. I'll need LOTTS of help designing a Xover. LOL

[Geoff St. Germain]

I'm not too sure on using this mid with the Dayton RS225s. That 8" B&C looks to me to be more of a woofer than a mid. Crossing it at 500 Hz seems to be a waste of that drivers capabilities.

[JCD]

Even more, I think the tweeter will be way overburdened at the 500hz mark. By that point, the published FR chart for the tweeter is already off by ~12db's with whatever THD it's pushing. I think that tweeter would do a lot better being crossed over at ~2250hz.

JCD

[Geoff St. Germain]

The tweeter is to be crossed at 1.3 kHz, not 500 Hz, but like you mention, I think that's still too low.

[JCD]

I did miss that.. my bad, but agree, it's too low.

JCD

[mayhem13]

Would you suggest maybe nixing the RS225's and add another B&C in a 2.5 way? I included the RS drivers becuase i couldn't get any usefull output below 80hz from the B&C woofers. I was hoping the waveguide would allow me cross the tweeter lower. Could you suggest another tweeter with high SPL that i could cross low? Thanx

[mayhem13]

2 12" acrylic hemispheres from a local plastics manufacturer. Laying each one flat and cutting across the diameter of the driver. line each half with poly-resin and make a mounting flange. Then simply weld the two halves together with acrylic acid. I'm using clear acrylic painted black inside. I may opt for a hemisphere shape instead of a complete sphere allowing the mid to better couple with the waveguide. I was hoping on some positives on the RS225's-two of these in parallel will have about 93db to keep up with the mid. My only concern is the tweeter. Didn't realize Morel was so inconsistent. I was under the impression that the waveguide would allow me to cross the tweeter lower than if on it's own ?

[JCD]

mayhem13 wrote:

I was under the impression that the waveguide would allow me to cross the tweeter lower than if on it's own ?

Will not claim to be an expert, but my understanding was that wave guides simply help with the directionality (is that a word?) of the sound wave -- it wasn't going to help increase the bottom end.

JCD

[mayhem13]

Not quoting anyone but i did read a blog from a reputable speaker builder who claimed that the FR smoothed out substantially on the lower end using a waveguide and a seas dome using 1 additional component in the network-response plots look great with the waveguide. This will be an experiment of sorts so what the heck-thanks for the feedback . And yes it also improved off axis response.

[looneybomber]

If you're going after a nice mid like that B&C, why not mate it up with a 4ohm Lambda 12" driver, say the TD12X or TD12H? However, using those higher priced, very formidable drivers is a bit of a waste without using a very nice tweeter, say a Fountek neopro5i?

[mayhem13]

I was trying to keep the baffle narrow at 10 inches or so but i know that those lambdas would sound incredible-please don't tempt me. Tweeters,tweeters,tweeters-what a major dilemma-compression or not ?

[looneybomber]

mayhem13 wrote:

I was trying to keep the baffle narrow at 10 inches or so but i know that those lambdas would sound incredible-please don't tempt me. Tweeters,tweeters,tweeters-what a major dilemma-compression or not ?

I have similar idea's as you. I've been eyeballing that B&C mid for a little while, mating it up with a Lambda 15 and I haven't decided on a tweeter. There's either the 300.00 neopro5i or compression drivers, which I have never been too fond of. Although I did see this waveguide on US speaker.com
DDS CFD ENG 1-90 PRO - 1" 90°x 90° WAVEGUIDE HORN. It might be a step in the right direction because I don't know if the unpleasent sonic signature of compression drivers is in the driver or the horn.

You may or may not know about John's MTM he's designing using dual TD10m's and the neopro5i. It's a fine design, but likely a bit too wide for your needs though.

[mayhem13]

I've finally settled on an MTM design using 2 B&Cs each in it's own 13 liter ported chamber. I'm going to use a dome tweeter mounted in a modified 8" waveguide. There is an interesting tweeter from italian speaker maker CIARE whose sensitivity is 105db! Given the 2 B&C's in parallel at 100db might work. If anyone is familiar with the B&C what crossover point do you recommend ? I'm thinking 1.8 khz with the waveguide. Any thoughts? The Vifa XT25 looks like another good choice but the lower sensitivity concerns me abit.

[mayhem13]

I'm sorry-all these letters get mixed up-i meant the DX25. My goal with this design is high headroom and dynamics in as small a package as possible. I may consider the 2.5 way but i willl need help with x-over to pull that one off! I'm so afraid that if i use a compression driver-well you know the story. There is another very interesting offering from Ciare-a compression tweeter that uses a silk diaphram! Very high SPL and power handling but i can't find a US distributor for it. I think the model was a 383 in their Pro-Audio section. Ordered the 4 B&Cs yesterday and some 2" thick black acrylic for the baffle cover/wave guide. Before i cut the threads of my test guide, i'll try an older JBL 2" i have-expensive test though-needs a diaphram.