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This started off more as a "What if?", and then progressed to a "Why not?" sort of deal... it's too bad the original RS28a tweeter went away, but we do have some alternatives these days that are interesting...
So why not combine most elements of the classic design from ET with the relatively new Peerless DA25TX008? or at least investigate the possibility, so that their are more fun budget builds to choose from...
I mean, we all know the old saying about the world doesn't need anther 6-1/2" two way, but they still keep popping up now and then... but an MTM is different, right? Yes?
Well, maybe not, but then for those of that mind, just consider this a short trip down memory lane, with a little twist... (it's ironic that the updated version of the RS180-8 is not in stock, but the original shielded version is.
So, this is going to be a little like a wedding dress- something old, (2009 RS180-8 data) and something new (recent DA25TX008 data), and for fun, let's just see how well this all works out, with a few tricks thrown in that weren't in use back in the time of the original Natalie P.
But, as I'm as much a nostalgia fan as you might expect for someone of my "maturity", we're going to keep the "interesting" series crossover concept of the original, just tweak it for a few more optimizations.
And so, let's take a look at what a fairly brief amount of time on one of the older Mac Pro's resulted in:
First, the somewhat updated schematic- biggest addition is an ultra sonic notch filter for the DA25 tweeter (the RS28a could have used that, too, but we weren't looking closely that high in the frequency range back in 2009 or so...)
So, with a very small number of component tweaks, we can wind up with a pretty nice curve- and remember, the bump at 3kHz in the measured DA25 reposes is basically a cabinet diffraction issue, which can be fixed acoustically. The driver measurements were made in the PE cabinets for the woofers, and with a similar size baffle for the DA25.
The impedance plot is pretty much what you'd expect- one might even say, "boring", which is a good thing...
The reverse null behavior is excellent, like the original, so I'll skip over to the filter behavior plot:
Part of the success of the original implementation for the NatalieP was having a bit more LF BSC boost than you might theoretically expect would be needed, but when one examines the raw reposes of the RS180's in the PE cab, you can see why that's of benefit. Here, the notch filter behavior is displayed clearly- precision for the component values is mandatory to get this well controlled response.
So, what next?
I do have one or two of the original size PE cabs in storage, though with the baffles cut out for other drivers, so new baffles would need to be fabricated. A pair of these might be a nice intermediate monitor for my music learning/playing studio, though I plan to do a line array for that before too long.
Obviously, these calculated and simulated component values need to be checked out in hardware, but I though it might be interesting to share the concept with the forum in case anyone else is curious about this approach or needs an MTM system like this- and has measuring gear.
Because of the size of the DA25, it's not likely to drop into an existing NatP build, though I don't know for certain that's not possible. Unfortunately PE doesn't have a knock down enclosure available now, or I'd built up a rough prototype to try out. I'll have to swing by the storage units sometime and see just how hard to access the cabinets I have are at this point...
So why not combine most elements of the classic design from ET with the relatively new Peerless DA25TX008? or at least investigate the possibility, so that their are more fun budget builds to choose from...
I mean, we all know the old saying about the world doesn't need anther 6-1/2" two way, but they still keep popping up now and then... but an MTM is different, right? Yes?
Well, maybe not, but then for those of that mind, just consider this a short trip down memory lane, with a little twist... (it's ironic that the updated version of the RS180-8 is not in stock, but the original shielded version is.
So, this is going to be a little like a wedding dress- something old, (2009 RS180-8 data) and something new (recent DA25TX008 data), and for fun, let's just see how well this all works out, with a few tricks thrown in that weren't in use back in the time of the original Natalie P.
But, as I'm as much a nostalgia fan as you might expect for someone of my "maturity", we're going to keep the "interesting" series crossover concept of the original, just tweak it for a few more optimizations.
And so, let's take a look at what a fairly brief amount of time on one of the older Mac Pro's resulted in:
First, the somewhat updated schematic- biggest addition is an ultra sonic notch filter for the DA25 tweeter (the RS28a could have used that, too, but we weren't looking closely that high in the frequency range back in 2009 or so...)
So, with a very small number of component tweaks, we can wind up with a pretty nice curve- and remember, the bump at 3kHz in the measured DA25 reposes is basically a cabinet diffraction issue, which can be fixed acoustically. The driver measurements were made in the PE cabinets for the woofers, and with a similar size baffle for the DA25.
The impedance plot is pretty much what you'd expect- one might even say, "boring", which is a good thing...
The reverse null behavior is excellent, like the original, so I'll skip over to the filter behavior plot:
Part of the success of the original implementation for the NatalieP was having a bit more LF BSC boost than you might theoretically expect would be needed, but when one examines the raw reposes of the RS180's in the PE cab, you can see why that's of benefit. Here, the notch filter behavior is displayed clearly- precision for the component values is mandatory to get this well controlled response.
So, what next?
I do have one or two of the original size PE cabs in storage, though with the baffles cut out for other drivers, so new baffles would need to be fabricated. A pair of these might be a nice intermediate monitor for my music learning/playing studio, though I plan to do a line array for that before too long.
Obviously, these calculated and simulated component values need to be checked out in hardware, but I though it might be interesting to share the concept with the forum in case anyone else is curious about this approach or needs an MTM system like this- and has measuring gear.
Because of the size of the DA25, it's not likely to drop into an existing NatP build, though I don't know for certain that's not possible. Unfortunately PE doesn't have a knock down enclosure available now, or I'd built up a rough prototype to try out. I'll have to swing by the storage units sometime and see just how hard to access the cabinets I have are at this point...
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