4 Way sanity check please

Here's an impedance measurement of both domes in an enclosure that Profiguy designed, I think it's around .35L? it's a perfect fit onto the magnet!
D7608 impedence.png
The above is fully stuffed(not tight) with rockwool and that's how I'm currently using them. The one below is one dome either full stuffed or half stuffed. Not sure what option would be better really. I could test more options.
Blue is half stuffed.
D7608 impedence stuffing.png
 
Here's something you could try. Add padding resistors to the tweeter. Off the top of my head, I'd suggest 10 ohms in parallel with the tweeter, and 2 ohms in series before the 10 ohm. This will smooth out the impedance. It helps with some tweeters and passive x-overs. I'm speculating that it might work in an active as well.
 
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I agree 2 Ne149w's seems a little odd. My reasoning is i already have 4 of them and also they will help keep the tweeter height down vs one larger midbass. Also 2 of them should beat one ne180w.
I'll do it as a test first.
I'm currently still liking this as a 3 way with the sb34nrxl75-8 crossed at 400-500hz. It does very well.
 
many wisdom says best 3 way is 4 way, for me 4 way + stereo subwoofer is the best choice.

my current setup almost look like yours, 3 way Dyn MW152 as midrange with 160Hz xo. but on going to change that into 4 way with 3.5" midrange & 6.5" midbass.
 
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I agree 2 Ne149w's seems a little odd. My reasoning is i already have 4 of them and also they will help keep the tweeter height down vs one larger midbass. Also 2 of them should beat one ne180w.
I'll do it as a test first.
I'm currently still liking this as a 3 way with the sb34nrxl75-8 crossed at 400-500hz. It does very well.

It is trade off. Only one if you don't need PA spll permits to have a good soundstage. According the filter slope you can with one driver handles 200 to 300 hz high pass and a low pass up to 2000 to 3000 Hz w/o too much problems according the complexity of the filter (some notch migth be mandatory (see Kurt Campbell work with this driver)

a 5" cone allows a good soundstage in an average livingroom and a wider passband than a 3' dome.

Now if more spl or less THD or if a different radiating patern is wanted -, you can use MTM or MMT in // or in 0.5 way filtering.

I personally would choose more MMT with simply the two 8 ohms // : less distorsion and lowered high pass. There is something good sounding with loudsppeakers having 150 hz circa high pass and >= 2000 hz low pass for the mids.

I personnaly have a good resolving loudspeaker with aluminium mid and tweeter covering acousticaly >100 hz bandwifth up to 20 Khz.

But agging, I 'd like to make today the opposit and comes back to papeer likes material for the mid (staying hard dome in the trebles though) : a little less details but more forgiving as most of the reccordings are mixed with such paper material at the end and many 16/44 materials are not always good.

So a 3 ways with 4 drivers, while the 4 ways could allow you subwoofer distributions.

My 2 cents, MMMV with time as high resolution speaker with hard cones/domes can be smooth to the ears too, but you need some EQ for the break ups and/or has a smooth good resolving DAC. I had to design a part of my ownn DAC analog stage to allow a complete vynil sound with the added dynamic and clearness of digital... Hifi is full of trade offs !

The little WMTM Barefoot (with 2 NE19W) is said no slouch with DSP and 3.5 waysfiltering (the MTM arrengment is physical, not the filter) or WMMT Joachim Gerhard last designs and we all know how good he can design loudspeakers :
https://suesskindaudio.de/en/ara

He is also making a loudspeaker with mid domes in a MMT arrengment :
https://suesskindaudio.de/en/kronos-2
 
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I know a lot of people will claim a cone mid will be of sufficient resolution in its linear passband, but a dome has far better (isually more predictable) off axis radiation uniformity than a cone mid. The sensitivity is usually better as well. THD may look good on paper, but that doesn't always translate into better "sound" than a larger dome.

I have all the drivers mentioned in the build here (aside from the T25B, but own the T34B) and am familiar with them. The NE149W is an excellent driver overall but it doesn't match the D7608 in midrange resolution, clarity and soundstage.

Once you listen to a good mid dome, you won't want to go back to a cone mid. That's how it was for me when I tried multiple cone drivers as substitutes for 3 way designs, allowing for a lower xover using a larger LF driver. The SB34NRXL is no slouch in many ways and performs far above its price point compared to other paper cone LF drivers.

While you can approach the overall resolution, clarity and depth of a metal cone/diaphragm system, it will be harder to remove the influence of the breakup peaks in the upper mids. There are multiple ways metal cone breakup resonances can spoil the sound of a speaker system. Unless using a fully DSP based system, you'll have a hard time getting full (sufficient) control over the drivers in terms of resonance breakup areas.

I generally try to aim for 2:1 driver emissive diameter ratios in multi way systems. That means ie. 12" LF, 6" lower MF, 3" upper MF and 1.5" HF. Thats a theoretically optimum situation on paper, so you can use a smaller tweeter anf mid overall. It doesn't however allow for a near perfect harmonic breakup sidtribution using other drivers. I find that a 1" tweeter and 2" dome mid can open up alot more choices. The 2" Morel mid domes are excellent as well with tweeter choices. The MDM55, CAM558 and EM1308 are all excellent mids will very similar sound characteristics. I recommend using surface dampening treatment on the outer chamber surfaces of the mids.

With the D7608 (and help of the custom 3D printed rear chamber), this combo knocks out much of the competition in its price range. Only some of the very high end cone drivers can approach the overall performance, but not exceed it.
 
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From a sensitivity side my dsp is 5dB less with the D7608 vs the ne149 to get exactly the same mid level.

I've fully covered the dome enclosures with car sound dampening.

I think one has to hear a dome in direct comparison to know what it does.
I like the ne149w alot. Befor them i had some scanspeak 15m/4624g mids but the ne149w was a good step up from those.
I also tried some 12mu's and those are very good but not a big step up or any step up from the ne149w imo well not for the money anyway.
The 15m's had what I would call a ring to them where as the ne149w is easy and relaxing with a way better more a realiistic lower midrange. The dome is more clean sounding, less colored, more detailed and has tighter imaging.
The only thing I fell I'm lacking is the lower mid detail/realism I had with the ne149w doing the lower midrange and that was with them crossed at 250 so maybe two of them crossed even a bit lower may be good.
 
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