This caught my attention, as now that I have the M74Ts in hand I am thinking about the next step. I have been planning along the lines of using them as direct radiators but have been intrigued by the idea of using them and the T34Bs both in WGs (sort of like a K+H 420 as an example). I have mostly let it go as I think they would do well as direct radiators, I don't have the skills to design the WG, and I think removing the grill of the M74 drivers has potential downsides/maybe they have to be ordered from the factory to enable this(?).
But it sure is an appealing idea...
Bill
This looks like a Volt VM752 without the horn.
Ouch, that is a lot more than I paired and mine came matched with the waveguide.
From what I heard though....... they are worth every penny of even that inflated price. I am talking about out of EVERY ultra high end system I heard, these domes blow them all away. I think just about every commercially available driver was being utilized somewhere in that convention. Plus a lot of bespoke drivers. This would stood out head and shoulders above the rest.
I would suggest not buying until I have measurements. Not that the measurments really matter to me at this point. I know what they sound like. That said, it will be interesting to see the distortion. It might have super high H2 and maybe that is what I like. Time to link distortion plots to my preferences.
I will have CNC available in a couple of months and what you speak of sounds very interesting!
I am based in Sweden however so integrated into baffle might lead to prohibitive shipping costs.. the cnc will be capable of aluminium though so a compromise would be a "mini baffle" in aluminium housing the 3 bliesma drivers that can be later incorporated into the larger baffle.
If you were to produce such a design i would be able to machine it for both of us and send you a pair for the cost of shipping and raw materials only.
I could of course be able to machine a complete baffle aswell if shipping would work out reasonably.
Cnc will have a work area of 1275x1275mm
@Bmsluite High H2 will show itself in looking at the difference of close range FR to further back. There will be a rising response from further back. Besides, its not a deal breaker my any means, only if you're using the driver for critical monitoring applications, not to embellish the mids. For consumer use, it only helps (to a point).
@Bill Brown You can remove the M74 grilles without causing issues. The screws behind the front outer ring release it, but the only critical thing is maintaining the VC plate location so it doesn't shift. If it does separate a little, you can easily align it with a 1V 500 hz sine wave. I've found that even from the manufacturer the alignment can be off considerably.
Mid domes respond well to basic conical profiles if the mouth termination is smooth. The Bliesma drivers are all wide directivity in their design and trying to reduce that directivity significantly with a waveguide seems counterproductive. I don't think there is any need to remove the protective screen to have a waveguide function as the inbuilt waveguide lip mates to a conical profile without any apparent issue in simulation. Unless the reason to do so is to keep the CTC low which is the opposite of what most waveguides will do.
😳 Do you see this in THD measurements? With the ones I used these where very consistent. I have one T74S sample, maybe I give it a try with this one.
Crazy. And when it's the Volt version you won't get the 380Hz cross over frequency.
You can use 2 nice M74x in a .5 configuration and be superior in every way.
Yup the price is...
But they are still crossed at 380hz in the PMC monitors.
Just look up the specsheets.
I don't think that is of question.
@IamJF On one of the four M74A I had to fuss with (loose front ring from insufficiently clamping, bottomed out screws), 3rd order HD was elevated than the rest. I had to center the VC with a 400 hz sine. The HD dropped considerably (0.4 - 0.25%), but the other three were only trivially improved. Using the speced Fs guaranteed exciting a slight wobble mode in the dome at about 4V drive. Almost every big dome suffers from a similar issue, which is why I always measure a new mid with 4V sweeps.
And don't let anyone tell you that dome drivers with single suspensions don't suffer from wobble modes or aren't even negatively effected by these non-linear resonance modes. Every single surround dome I've come across can be pushed into a wobble mode of some kind. It can show itself as a tipping motion or a combination of tilt and radial wobble (like a plate being set down unevenly on a table top, gradually wobbling itself to a standstill). This is why an LCR notch at Fs is important for any single suspension dome driver being crossed very low around that range.
@LewinskiH01 I'm not aware of any refined WG designs for the M74A. Here's a link to someone who's trying something similar, but more like the Neumann setup.
The profile exists but I have not made it into an STL that can be printed. There is a fair bit of time and effort involved in turning a simulated idea into a printable model that fits properly on the actual driver and can be mounted in a sensible way. I haven't and don't intend to do that, but if someone else wants to I will provide the profile as a base to use, like I did for the T25A waveguide. The full surface is elliptical but in that configuration the vertical directivity narrows quite early, the horizontal as shown above could be used all the way round, the vertical and horizontal would then be equal but the CTC distances would increase.
I've got a bit of a silly idea, but i''m wondering how hard would it be to modify a compression driver into a direct radiating midrange dome?
The idea comes up every now and then. There have been people who listened via the opening where the horn would attach, i.e. through the 1', 1.4", or 2" opening. One guy loved it. That never seemed to make as much sense to me as removing the back cover such that you are looking at and listening to the convex side. The problem that is always pointed out is the minuscule Xmax of compression drivers. Regardless, it would be interesting to see a good set of measurements.
Bill
Bill
Yeah, remove the back cover and attach it to the horn opening instead. And 3D print or smtg a faceplate. Sounds doable....