Thanks for the positive vibes!
Prolly omit the midranges given what I am learning.
If hardwood, it would be oak-ply with solid end-pieces.
Thanks for the positive vibes!
Odd, I thought the directivity mismatch between the large woofer and the D2 at 800 Hz was one of the big compromises JBL made in this speaker. My thought was a 6-8" would be a better match, I got the 5" mids for so cheap I couldn't resist trying (especially since it took a while to get the woofers).
I am realizing all that now. The mid isn’t working well. Which is just fine.Hello
The 15" to waveguide DI works out very well. Look at the classic 4430/35 designs from the 80's. One of the biggest strengths is the waveguides DI and dropping in a mid would cause you to have a crossover point in the waveguides range say 1.5 - 2K so you would be trying to match there. I doubt you could get a match be as good as the waveguide itself. I would get the "stock" system up and running first.
As far as issues with the 2216Nd I certainly have not had any issues audibly from them. If you want to try to get a mid in there have at it but I don't think the basic design is that flawed that it "needs" one.
The speaker was about 3 feet off the floor... I was trying to make sure it was reasonably decoupled.Where was the speaker positioned while you tested the impedance? With large pro sound drivers like this I've noticed even reflections from the room/floor can cause a visible ripple in the measured impedance.
Otherwise what's the internal depth of your cabinet? Is it around 12.5"?
I've been enjoying the DIY M2's. I've abandoned the 3-way version!!! (for now...) I'm using the exact JBL PEQ from the JBL M2 active crossover settings doc. I add a simple PEQ for the bass since I have a sealed cabinet (I'm about to start on the finished version of the cabinets). I use a MiniDSP Flex balanced and implement the M2 input and output-channel PEQ with the built-in filters. The FIR filter block is used for the active crossovers.
View attachment 299560
I've played around with a few other PEQ, and have been experimenting getting closer to ideal crossover acoustic response slopes, but the JBL PEQ sound fantastic and I haven't invented a better sounding speaker yet! I've been meaning to post measurements... In the meantime...
I had been wondering about the odd resonance Erin measured at 270Hz. He commented on the resonance, and measured the woofer in the ported M2 cabinet and saw that it went away when measured free-air. I did a frequency sweep of the 2216Nd in the sealed enclosure I made and I see a small resonance at 270Hz, but it's only 10-20% of the magnitude that Erin measured in the JBL M2 ported cabinet. Here is my measurement vs. what Erin published (stretched to match x- and y-scales):
View attachment 299559
I'm not clear why my sealed boxes have similar but smaller resonance as the much taller ported M2 cabinets. Is it the port?
Like Erin, I think the speaker sounds fantastic and I can't hear issues in music or sweeps. But I can't figure out the resonance and it seems it's not the height of the speaker like was suggested. And why it shows up but much lower magnitude in a small sealed enclosure.
Thanks Fredrik.Hi @MAB,
Good job, I bet they sound spectacular!
I have been thinking about building myself a pair of M2's.
Did you DIY the physical passive crossover network? If so, did you buy off the shelf components for this?
I live in Sweden so it will be quite the investment to import the parts from the US, every bit helps.
Did you make your own plans for the cabinet or did you source them from somewhere?
Again, good job with the project!
Yeah, the resonance shows up on JBL's measurement of the raw driver too. But is dramatically elevated on their M2 speaker.Nice project! I wonder about the Imp spikes as well?? Look at the JBL raw data?? I also did a passive version and I don't see them in my curves at all?? I am in a reflex enclosure but I have 3 1/2 of fill right behind the woofer.
Yeah, the resonance shows up on JBL's measurement of the raw driver too. But is dramatically elevated on their M2 speaker.
The second impedance plot is your woofer with the passive crossover, right? And it's a simulation or measurement? In any case, I think this is different than a measurement of the raw driver's impedance...
It's the passive crossover! Your measurements are different in many ways due to the crossover.That's my speaker pairs actual measurements. I don't get the reason why it's more prominent in the M2 measurements compared to my own or the OP??
It's the passive crossover! Your measurements are different in many ways due to the crossover.
You can even see differences in Erin's and other's measurements with and without JBL's ported enclosure.
Bare driver (3 different ones from from beatelund):
Driver in cabinet with no crossover (with double peak in the impedance due to the additional port-resonance!!! also from beatelund):
You can see the double-peaks in the ported alignement, and the increase in the impedance blip.
Erin's comparison of the speaker in free-air and in JBL's ported enclosure with my measurement in a sealed cabinet:
Your measurement is of the sealed alignment, but with a passive crossover. The tiny resonance in the impedance measurements is obscured by network impedance of the driver plus passive crossover! In any case, this is not the most important thing about this speaker.
Great question. I don't know.Hello MAB
Being dense why do the 3 driver free air look better than the ported M2 if it is indeed a driver issue. Is the enclosure making it worse?? I am in a ported not sealed enclosure. You can also see it with the curves overlaid. I agree we are picking nits as the drivers sound great! Just curious!
Could it be measurement resolution???
I'm a bit confused about these crossovers. They appear to be used to protect the compression driver when used with Crown power amps. I wonder if there are any passive crossovers so that the clone M2s could be used with a single amp.Thanks Fredrik.
They do sound great, beyond my expectations.
No need to buy the crossovers, I built my own with an 8uF capacitor and a some non-inductive resistors
View attachment 299812
The crossover document by @pos is incredibly valuable:
View attachment 299792
Note: JBL's own literature has the wrong cap value!
I use a MiniDSP flex balanced. I apply the crossovers with the FIR blocks, and the PEQ using MiniDSP's filter blocks. The Flex doesn't have enough FIR taps to do the entire crossover and PEQ exactly as spec'ed in the RePhase document.
The cabinet plans are my own and are just a sealed (instead of ported) cabinet with Q~0.75 and the same baffle width and lens-to-woofer spacing. Ported you need to source the special JBL ports (3D printed), or go with an off-the shelf port, and potentially listen to port noises. In any case I tend to prefer sealed with PEQ. I EQ the bass to reconstruct the ported response of the M2. As a result, I have less peak output... for me, I don't need more output! I will eventually integrate subs, which will make the loss of output with sealed alignment even less of an issue for me. They play loud, effortlessly, tirelessly, etc. as-is.
Many pages of instructions, discussions, and diversions are all here:
Since the JBL Master Reference Monitor thread is so massive I'm staring a thread that I and others can document our M2 DIY process if the. Here are some links that I was able to reference. Thank you for all of your contributions that made my and others project happen. Schematic of the M2 -...www.audioheritage.org
I'm a bit confused about these crossovers. They appear to be used to protect the compression driver when used with Crown power amps. I wonder if there are any passive crossovers so that the clone M2s could be used with a single amp.