Here's an example, of a 6" midrange (which will remain unidentified to avoid bias)
A nearfield measurement with a long gate (1000ms):
This reveals a slight shelf starting around 700Hz... then a dip at 3KHz followed by what seems to be a mess beyond that.
Remember that we start to lose precision as we go up in frequency in a near field measurement?
Some say the imprecision starts at 4311 / diameter of the cone, which for a ~5" cone which would mean somewhere around 850Hz. But that's drawing a line the sand, because imprecision actually starts a little earlier- you can see the fuzziness starting from around 350Hz or so.
Now, at 3KHz, is there really a dip or not?
For that we have to take a far-field measurement:
Measurements in a test box, square baffle dimensions 8 1/4" x 8 1/4" @1 ft.; SPL shown to 1m.
Gate is 5ms, to avoid the first reflection (floor). But the downside is that there is some smoothing in the midrange frequencies
So that dip is around 2.5KHz or so...
Next: Optimized crossover for band-pass for 94dB/2.83V with acoustic LR4 500Hz; 2500Hz:
This is an example of a VERY GOOD driver.
Whether is works well with an arbitrary HF or LF unit is a completely different matter...
A nearfield measurement with a long gate (1000ms):
This reveals a slight shelf starting around 700Hz... then a dip at 3KHz followed by what seems to be a mess beyond that.
Remember that we start to lose precision as we go up in frequency in a near field measurement?
Some say the imprecision starts at 4311 / diameter of the cone, which for a ~5" cone which would mean somewhere around 850Hz. But that's drawing a line the sand, because imprecision actually starts a little earlier- you can see the fuzziness starting from around 350Hz or so.
Now, at 3KHz, is there really a dip or not?
For that we have to take a far-field measurement:
Measurements in a test box, square baffle dimensions 8 1/4" x 8 1/4" @1 ft.; SPL shown to 1m.
Gate is 5ms, to avoid the first reflection (floor). But the downside is that there is some smoothing in the midrange frequencies
So that dip is around 2.5KHz or so...
Next: Optimized crossover for band-pass for 94dB/2.83V with acoustic LR4 500Hz; 2500Hz:
This is an example of a VERY GOOD driver.
Whether is works well with an arbitrary HF or LF unit is a completely different matter...
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A wide baffle and a waveguide have a lot in common. They both exist to support the wavefront..
They sound good when done well. In addition I'm an advocate of avoiding the baffle step. The concepts are not typically well known. I take advice from people who understand better than I do, and it helps to know the difference.
I can take the nearfield measurements @tktran303 recommends.
However, before doing so...does anyone want me to continue with the Markaudio CHP-90 as an option? While it performs fine, is it likely we are going to end up selecting it over the SB15MFC, SB12MNRX or the 15W/4434? I don't mind continuing with it, but if we are sure we won't select it then I can save some time and omit it.
However, before doing so...does anyone want me to continue with the Markaudio CHP-90 as an option? While it performs fine, is it likely we are going to end up selecting it over the SB15MFC, SB12MNRX or the 15W/4434? I don't mind continuing with it, but if we are sure we won't select it then I can save some time and omit it.
To be fair to the Mark Audio driver please do it too. Based on the other tests, I couldn't see any reason to omit it.
Besides, if it does make it in as a suitable candidate, Some people who really feel that that crossovers are bad, this Classic 3-way could also be a Woofer Assisted Wideband, with the flick of a switch to turn off it's high pass filter/turn off the tweeter!
Besides, if it does make it in as a suitable candidate, Some people who really feel that that crossovers are bad, this Classic 3-way could also be a Woofer Assisted Wideband, with the flick of a switch to turn off it's high pass filter/turn off the tweeter!
are you kidding? This thread is moving at breakneck speed. I think you are thinking of Lynn's homage to self pleasuring.
Some brands like SB Acoustics use frame diameter as nominal size, most (like SEAS and SS) are closer to real Sd.
"nearfiel driver measurement" is ½inch- roughly 1cm from dustcap. It can have anomalies in case of a midrange with really deep cone (like Vifa NE series). I measure also at cone edge, above surround and at 5cm from dustcap, then look at overlayed responses. Nearfield distortion is reliable but sometimes the mic can't take high enouhg spl.
It is safe to use nearfield data below 400Hz with baffle diffraction simulation. Above 400Hz we must know the diffractions induced by cone7dome profile, surrond and baffle, and directivity behaviour - measured at 1m in baffle/box.
"nearfiel driver measurement" is ½inch- roughly 1cm from dustcap. It can have anomalies in case of a midrange with really deep cone (like Vifa NE series). I measure also at cone edge, above surround and at 5cm from dustcap, then look at overlayed responses. Nearfield distortion is reliable but sometimes the mic can't take high enouhg spl.
It is safe to use nearfield data below 400Hz with baffle diffraction simulation. Above 400Hz we must know the diffractions induced by cone7dome profile, surrond and baffle, and directivity behaviour - measured at 1m in baffle/box.
I never looked into this closely (another project for another day) but Juha, what differences did you observe at the cone edge, or at the surround, when compared to the centre of the cone?
I haven't saved all my nearfield measurements, because I don't need them actually. But differencies are surprisingly large in spl at freq above 2kHz typically. Cone geometry and surround deformations are the obvious causes. Near edge also distortion is higher. 5cm from dustcap is best as single measurement.
Here 2 handheld nearfield sweeps, taken by 30s interval. Mic near dustcap, perhaps at 1cm in both.
And same also at 20cm and 1m distance. Installed in the speaker and measured indoors.
Here 2 handheld nearfield sweeps, taken by 30s interval. Mic near dustcap, perhaps at 1cm in both.
And same also at 20cm and 1m distance. Installed in the speaker and measured indoors.
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Personally, I would've have the build going on page 2. I'm not really a "gotta catch em all" driver person, so the endless discussion on drivers feels silly. Just pick the flattest ones you can afford for the budget that will mate well in terms of dispersion and distortion.
Perhaps I've outgrown this forum.
I'm sure you know all the sayings about design by committee. I just wanted to insult my least favorite thread here on diyAudio.
I won't be building this, too many drivers in the stash to be buying new; but I'll stick my oar in the water anyway. While I may actually like the look of Monkey Coffins to ignore the issues caused by hard angles etc doesn't seem right.
At the least I think the design should incorporate either large chamfers or roundovers at the edges and perhaps also a full felt baffle.
While not the cheapest I personally now favour adjustable L-Pads rather than fixed.
I will keep reading and my interest in the project tho.
At the least I think the design should incorporate either large chamfers or roundovers at the edges and perhaps also a full felt baffle.
While not the cheapest I personally now favour adjustable L-Pads rather than fixed.
I will keep reading and my interest in the project tho.
I plan on building two cabinets.
One very much in the traditional Monkey Coffin spirit - flat baffle with sharp edges and no waveguide.
One - with the same drivers - with a chamfered edge and a 3D printed waveguide for the tweeter.
One very much in the traditional Monkey Coffin spirit - flat baffle with sharp edges and no waveguide.
One - with the same drivers - with a chamfered edge and a 3D printed waveguide for the tweeter.
Why though? I can tell you right now the waveguided tweeter will be better.
Same wide baffle, done in room so kind of sloppy. Top is a D27, bottom is an ND25FW, no round overs on this one. I know which one I'm picking.
I figured the benefits of waveguides and roundovers were pretty well understood at this point but hey, it's your time and wood. Good luck.
Thank you for your contribution. Let's not be so dismayed!
It was clear that some people don't want the waveguide, or round-overs. eg. @waxx @hifijim ?others
They want the classical look, for nostalgia, aesthetic, for ?performance reasons. They have been championing that we should stick to the classic formula as much as possible.
You might be surprised at @A4eaudio - I think he's got a plan to please people who want the classic 6 sided box design that they can build on a kitchen table, also people who understand that the shape directs the directivity, but still want to move with the evidence/ data.
The price to pay is ONLY A BIG BOX for the woofer!
Is there any chance you could convert the above line chart to a polar map, so people on either side of the fence can peer over the other side?
Please hang around, you clearly have knowledge to contribute/agitate/advocate for people to pivot, shift and change!
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