Next project: 3-way with open baffle

[rpb]

Re: Next project: 3-way with open baffle

It's just another way to help shape the tweeter response/level. A series resistor before the filter is easy to simulate in PCD, and I've found that sometimes it helps eliminate the need for an Lpad.

The L-pad may make it easier to shape the lower end of the midrange response. I don't like a sharp knee in a response.

[50 watt head]

Re: Next project: 3-way with open baffle

One suggestion . . . offset both mid and tweet on the baffle, and keep them aligned vertically. The 2" mid will benefit from the baffle offset, just like the tweet.

Will do -- thanks!

[Pete Schumacher]

Re: Next project: 3-way with open baffle

Yep, it's a 3-way design, so it'll be a challenge!

On the other hand, I can't help but think that other aspects of this project will be less complicated, due to the fact that the woofer can be dealt with separately from the mid/tweeter. The woofer will just be in a simple box, with a simple 2nd-order LP filter. Once that's taken care of, the prototyping could begin by grabbing a random piece of pine 1x8 out of the scrap pile and mounting the mid and tweeter on it. Adjusting driver offsets and alignments and acoustic centers suddenly became really easy And, when one baffle turns out to be a dud, I can grab another scrap and try another alignment. (All of this would be informed and guided by the simulations I've already done in PCD.)

It just occurred to me just now that this isn't *that* much different from a typical subwoofer and satellite design. What my idea has more or less turned out to be is much like what you would have if you had a subwoofer on each channel, crossed really high (~600 Hz), to a small box-less TM satellite.

Aesthetically, I'm thinking of finishing the bass bins in black, and using a really nice light-colored hardwood (e.g., quilted maple) for the TM baffles. That would look sharp! I won't have access to my tools for awhile, though, so actually making some sawdust on these will have to wait until later this summer :(

One suggestion . . . offset both mid and tweet on the baffle, and keep them aligned vertically. The 2" mid will benefit from the baffle offset, just like the tweet.

[50 watt head]

Re: Next project: 3-way with open baffle

It looks like this one could be even more challenging..

Yep, it's a 3-way design, so it'll be a challenge!

On the other hand, I can't help but think that other aspects of this project will be less complicated, due to the fact that the woofer can be dealt with separately from the mid/tweeter. The woofer will just be in a simple box, with a simple 2nd-order LP filter. Once that's taken care of, the prototyping could begin by grabbing a random piece of pine 1x8 out of the scrap pile and mounting the mid and tweeter on it. Adjusting driver offsets and alignments and acoustic centers suddenly became really easy And, when one baffle turns out to be a dud, I can grab another scrap and try another alignment. (All of this would be informed and guided by the simulations I've already done in PCD.)

It just occurred to me just now that this isn't *that* much different from a typical subwoofer and satellite design. What my idea has more or less turned out to be is much like what you would have if you had a subwoofer on each channel, crossed really high (~600 Hz), to a small box-less TM satellite.

Aesthetically, I'm thinking of finishing the bass bins in black, and using a really nice light-colored hardwood (e.g., quilted maple) for the TM baffles. That would look sharp! I won't have access to my tools for awhile, though, so actually making some sawdust on these will have to wait until later this summer :(

[Soundslike]

Re: Next project: 3-way with open baffle

Wow Phil, barely enough time to catch your breath from the Gila Monsters and you're tackling another design. It looks like this one could be even more challenging. Can't wait to see how it turns out.

[50 watt head]

Re: Next project: 3-way with open baffle

Why do you place the resistor in front of the x-over? It will change other values needed, but I'd put a resistor in series, and one across the terminals.

It's just another way to help shape the tweeter response/level. A series resistor before the filter is easy to simulate in PCD, and I've found that sometimes it helps eliminate the need for an Lpad.

[rpb]

Re: Next project: 3-way with open baffle

OK, here is a preliminary stab at a crossover for

Peerless 831735 + HiVi BMNa + Vifa BC25SG15

I've mocked it up for now as a conventional box/baffle, with convenient/ballpark driver offsets, just to get the ball rolling.

Pete, I modeled around with the ND20, and I after awhile I just found the Vifa easier to work with. Even though it's a large-faceplate tweeter, that hasn't caused any trouble for me yet.

Wolf, thanks for the tip on the HiVi mid, so far that's been pretty easy to work with, and it came out with less components in the Xover than the tweeter

Why do you place the resistor in front of the x-over? It will change other values needed, but I'd put a resistor in series, and one across the terminals.

[50 watt head]

Re: Next project: 3-way with open baffle

Here's another simulation, using the RS180-8 instead of the 831735.

Crossover is very similar to the circuit I posted above. Looks like an increase of a few dB in sensitivity. The RS180 mounting hole is 5.75" which is identical to the 831735, so the cabinet could be built such that they are physically interchangeable.

[greywarden]

Re: Next project: 3-way with open baffle

Oh well yeah that makes sense

[50 watt head]

Re: Next project: 3-way with open baffle

So... what's the benefit of an "open baffle" with sealed-back drivers on the baffle?

I'm not sure there are any benefits. My considerations behind this idea were partly aesthetic ("it's cool and unique") and partly functional ("why build a box for drivers that are already sealed?").

Basically, I was planning to build a ported bass bin for the woofer; that's straightforward, nothing special there. Beyond that, the design process would involve nothing more than a simple baffle with the M and T drivers mounted to it. Play around with offsets and alignment from there. Sounds like fun!

[greywarden]

Re: Next project: 3-way with open baffle

So... what's the benefit of an "open baffle" with sealed-back drivers on the baffle?

Are the woofers going to be open, too?

I was going to suggest using a cone did, like a small fullrange, and a tiny tweeter like the NDs

Then situate the peerless woofers in an H-, U-, or W-frame (for lack of a better term, I just woke up).

[50 watt head]

Re: Next project: 3-way with open baffle

OK, here is a preliminary stab at a crossover for

Peerless 831735 + HiVi DMNa + Vifa BC25SG15

I've mocked it up for now as a conventional box/baffle, with convenient/ballpark driver offsets, just to get the ball rolling.

Pete, I modeled around with the ND20, and I after awhile I just found the Vifa easier to work with. Even though it's a large-faceplate tweeter, that hasn't caused any trouble for me yet.

Wolf, thanks for the tip on the HiVi mid, so far that's been pretty easy to work with, and it came out with less components in the Xover than the tweeter

[Wolf]

Re: Next project: 3-way with open baffle

That's right- I don't like it, and never have, no matter who's used it.

In the way OP stated 'open-back', yes. Dipole- no.

Later,
Wolf

[rpb]

Re: Next project: 3-way with open baffle

Keep in mind that a smaller format mid will exacerbate baffle diffraction, especially above the step, where the RS52 will be playing. Pay special attention to that upper baffle, and get some large roundovers up there to smooth things out.

+1 .... I would attempt this only if you plan to measure the responses.

[50 watt head]

Re: Next project: 3-way with open baffle

And you mentioned inspiration in seeing another like that, was it these?

Yep, I recall seeing that pic of yours before, so I'm sure they formed a part of my inspiration.