@IamJF I agree on the topic of power compression and sensitivity requiring less for a given SPL. I dont share the same opinion or experience with running the Bliesma at pro audio levels and trusting them long term compared to the Volts.
I can get replacement VCs for the Volt which I can swap in quickly but the Bliesma needs to be sent back to Germany for repair - not cheap for us Americans needing to pay insanely high European customs fees, even if its for repairs and not new items. I also dont have pleasant experiences dealing with Bliesma based on the issues I had a while back with my T34Bs. That was a horror show which I don't wish to discuss anymore as it made me want to leave this forum for good after being beat up by the Bliesma loyalists wanting to burn me at the stake for saying anything critical (but thruthful) about their products. That was a nightmare I don't wish to revisit after thankfully resolving it myself. I still love Bliesma products but am using greater caution when weighing all options creating new designs. This is why I consider mid domes like the SS D7608 and SB MD60N despite the availability of other boutique options.
Let's just please respectfully agree to disagree and move on. Sometimes we have to make compromises and deal with them best we can even based on other underlying factors, even if there are other options. The Volt VM753 has its place despite its downsides and still can sound very good when utilizing it in the 500 - 3.5k range. Its a proven driver with a good track record and sound. The Bliesma M74A/S/B does beat it in a few ways, but the Volt is much more forgiving and easier to get ahold of here in the US.
I can get replacement VCs for the Volt which I can swap in quickly but the Bliesma needs to be sent back to Germany for repair - not cheap for us Americans needing to pay insanely high European customs fees, even if its for repairs and not new items. I also dont have pleasant experiences dealing with Bliesma based on the issues I had a while back with my T34Bs. That was a horror show which I don't wish to discuss anymore as it made me want to leave this forum for good after being beat up by the Bliesma loyalists wanting to burn me at the stake for saying anything critical (but thruthful) about their products. That was a nightmare I don't wish to revisit after thankfully resolving it myself. I still love Bliesma products but am using greater caution when weighing all options creating new designs. This is why I consider mid domes like the SS D7608 and SB MD60N despite the availability of other boutique options.
Let's just please respectfully agree to disagree and move on. Sometimes we have to make compromises and deal with them best we can even based on other underlying factors, even if there are other options. The Volt VM753 has its place despite its downsides and still can sound very good when utilizing it in the 500 - 3.5k range. Its a proven driver with a good track record and sound. The Bliesma M74A/S/B does beat it in a few ways, but the Volt is much more forgiving and easier to get ahold of here in the US.
I have used a mdm55 crossed at 750Hz -12dB for a long time now. Imo it works great with a 15” woofer in a closed box. The 15” uses only an inductor in series. I’ve gone through 4 or more types that blew up, not one mdm55, but I do not blast it like I used to. I also use a mdt30 as a tweeter, crossed at 3.8k iirc. For the price, the mdm55 is unbeatable, not very many drivers have been in production that long, has to say something don’t ya think?
The MDM55 (or CAM558) is a great mid in many ways, especially for the price. I've used them crossed at roughly between 800 - 1000 2nd order with dual 6 - 8" woofers. They image very well and easily disappear into the room on the correct baffle. I like to use the CAT378 tweeter with it due to the acoustic center being already perfectly aligned. A 4k xover is perfect with these. The mid has the right sensitivity to work with dual LF drivers, each having 86 to 88 dB/2.8V.
The MDM55 doesn't have the last word in resolution but it has plenty of it to compete with alot more expensive mids which don't have the bandwidth or off axis performance. A way around the relatively high necessary HP is to use 2 of them with staggered LP filters so only one operates up to the tweeter LP. This also improves THD, raises SPL capability and reduces the amount of the BSC needed to work on a narrow baffle. You can drop the HP to about 600 hz 2nd order this way. The 2mm peak to peak xmax is more than enough to keep up with the LF drivers.
The MDM55 / CAT378 combo makes for a capable, transparent mid field monitor. I'm using this recipe in some smaller monitors for my son's studio with dual Morel CAW538s in ported 30 ltr enclosures crossed at 900 and 4k 2nd order. This driver package manages quite a bit of SPL and dynamics in a very small package flat down to 50 hz. While the smaller Morel 5s don't have the lowest THD compared to other smaller LF drivers, they have highly resolving midbass and no detectable power compression thanks to a pair of huge 3" VCs. This package is able to convey complex material precisely with good balance of harmonics and accurate timing. They definitely pass the piano test with flying colors thanks to their clarity and natural character in the mids which IMO only can be provided by a decent dedicated midrange dome.
The MDM55 doesn't have the last word in resolution but it has plenty of it to compete with alot more expensive mids which don't have the bandwidth or off axis performance. A way around the relatively high necessary HP is to use 2 of them with staggered LP filters so only one operates up to the tweeter LP. This also improves THD, raises SPL capability and reduces the amount of the BSC needed to work on a narrow baffle. You can drop the HP to about 600 hz 2nd order this way. The 2mm peak to peak xmax is more than enough to keep up with the LF drivers.
The MDM55 / CAT378 combo makes for a capable, transparent mid field monitor. I'm using this recipe in some smaller monitors for my son's studio with dual Morel CAW538s in ported 30 ltr enclosures crossed at 900 and 4k 2nd order. This driver package manages quite a bit of SPL and dynamics in a very small package flat down to 50 hz. While the smaller Morel 5s don't have the lowest THD compared to other smaller LF drivers, they have highly resolving midbass and no detectable power compression thanks to a pair of huge 3" VCs. This package is able to convey complex material precisely with good balance of harmonics and accurate timing. They definitely pass the piano test with flying colors thanks to their clarity and natural character in the mids which IMO only can be provided by a decent dedicated midrange dome.
So much cool info on the mdm55, something I took a chance on many moons ago. Great idea on using two of them with a custom passive crossover design.
I have a pair of dynaudio geminis that I bought as a kit from Madisound, they are bit more detailed but were a much larger investment. The Gemini’s obviously lack the bass kick of the sealed 15” woofer but pair up well with them too. Best of both worlds. I am content with these speakers. What I should do is some evaluation with some of my new amps, Dh-220c and bc-1, for another day
Cheers Rick
I have a pair of dynaudio geminis that I bought as a kit from Madisound, they are bit more detailed but were a much larger investment. The Gemini’s obviously lack the bass kick of the sealed 15” woofer but pair up well with them too. Best of both worlds. I am content with these speakers. What I should do is some evaluation with some of my new amps, Dh-220c and bc-1, for another day
Cheers Rick
When you search for a 2" midrange for low crossover the Dayton aluminium is the right choice. Couldn't find good measurements but it's very linear at low and high frequencies. But it's very high resolution, I put it 1-2dB lower to get a balanced midrange. And I also used 2 to get more membrane area.
@Paul Ebert I'd rank the MDM55 just shy of the D7608 in terms of overall performance. Its a little more laid back in detail but is easier to use with other soft domes crossed above 3.5k. The D7608 has a bit more detail and air all round. It can seamlessly blend with a metal HF dome or a ribbon which the Morel has issues with being a little more vague up top.
i have listened a pair of Passive ATC 100 this week and i can say that the ATC dome is so spectacular that the Bass and higs of these speaker are not at his level of dynamic . a shame that we coulnt find it for DIYers. 
i will be happy to mix it with a 15inch woofer and a horn tweeter ..
i will be happy to mix it with a 15inch woofer and a horn tweeter ..
we can use this ones
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That ellipticor is way overpriced. I can buy a pair of TADs for the price of one. They also don't thrill me in regards to reliability of that VC shape. The ATC is still the one to get if you want the best 3" silk dome. I'd rate the M74B a close 2nd but better in some ways. M74A is the best value in a 3" dome.
Can you clarify what you mean by the woofer and tweeter not being at the same level of “dynamic”?
Have you had any issues with the inconsistency these usually have? I've found that earlier made in India versions were better than the current run made in China. They also need better dampening to get rid of the H3 peak around 4 - 5k.
The severe 10k peak is also a bit strange as it turns into a dip off axis. This is from the speed of sound being higher in the dome material and emitting 10k out of phase at the tip in relation to the sound coming from dome center simultaneously.
This driver needs a phase shield at the tip of the dome to attenuate the on axis peak, reducing its effects off axis, as an electrical notch will cause more issues than it solves.
i found the Bass limited in deph and omphh factor but i'm used to a 15inch woofer there was also magico S3 in my local shop running too and when you hear their berriliyum tweeters the return is dificult to the silk one of the ATC . but i prefer the ATC medium by a large margin ..