Citation 7.2 = Morel goldmine

[so_ein_pech]

Yesterday I was the somewhat underwhelmed owner of a pair Citation 7.2 THX speakers that sounded way worse than they had any right to given their outlandish MSRP.

While I'm sure the whole THX system was impressive, the speakers had some quirks that made them pretty useless as stand-alone stereo speakers. Each box has two tweeters placed too close together to intentionally limit the horizontal dispersion. And, worse of all, they were crossover limited to 80(!)Hz because they were designed to be operated with some big ol' JBL 15" subwoofers. These are not small speakers, mind you.



The cabinets are a bit damaged and were ugly to begin with, so I decided to open them up and see what they are made of and if they were worth parting out.

I am now the proud owner of 4 each of British Made Double Magnet HexaTech Aluminium Voice Coil Morel MW-166 Woofers and HexaTech Aluminium Voice Coil Liquid Cooled Soft Dome MDT-30 (an EC Product) Tweeters! Ok so the tweeters have one edge sliced off of the faceplate so that they can be installed closer together and one tweeter is impacted, but they still make and sell replacement domes for a reasonable price.



Now I'm trying to figure out what to do with them. I was thinking maybe some kind of Morel Duet clone? This is a speaker that I had never heard of before today but is apparently very well respected. From my preliminary research tonight, it used a more efficient/expensive but similar tweeter, and used the same MW-166 drivers. I am hoping that @baco99 will chime in since he seems to be the Morel evangelist around here and had a thread about a similar project he worked on a few years back.

I also found a crossover someone designed on madisound for a MW-166/MDT-32S speaker system. Based on the datasheets on the MW-30, it's the same as the MW-32 but with a smaller faceplate. Apart from a different Fs, I can't spot a difference between the S and non-S variants. I don't see any info on cabinet specs that would go well with the crossover as designed. I assume it's a sealed box?

According to the Renaissance Audio website the Duet is partially transmission line loaded. I like the idea of transmission lines, having recently acquired a pair of Timeframe 600's. But this guy over here says that the Morel drivers are best in sealed enclosures. Maybe I should stick to that since I've never built a speaker cab before.

So... any thoughts or recommendations?

 

[baco99]

nice investigative work. when I have a sec later today, I will opine.

 

[audiomagnate]

I used to make and sell (on a very limited scale, maybe 20 pairs) a floorstander using those drivers in MTM (single tweeter, first order crossover) configuration. I loved them. I also made a smaller version using a single woofer that also sounded great. Those are superb drivers.

 

[so_ein_pech]

I was thinking about MTM, maybe with a rear ambiance tweeter. Wouldn't you want the 4 ohm version of the drivers for an MTM though?

 

[baco99]

I was thinking about MTM, maybe with a rear ambiance tweeter. Wouldn't you want the 4 ohm version of the drivers for an MTM though?

the impedance of the drivers shouldn't matter as much depending on how you design the crossover.

My recommendation would be to make yourself a set of slender towers in a TWW arrangement, and consider a 2.5 way design where you have one woofer doing a mid-high bass bandpass, and another woofer just handling the bottom. I have been toying with a design idea like this. The professional ones I have heard, I like a lot. This gets you the SPL you need to match the tweeter's output in the low frequencies, but frees up one of the woofers to just focus on midrange and upper bass, reducing unwanted modulation. You can control the lower cutoff of the upper woofer by the design of the cabinet (small sealed, for example) to limit the bass without complicating the crossover.

I would put the bottom woofer in a transmission line box similar to the one Morel themselves designed or design your own quarter wave.

OR, you can put the bottom woofer in an aperiodic enclosure using two Scanspeak Variovents. https://www.madisoundspeakerstore.com/flares/ports/vents/scanspeak-290001-aperiodic-vent-ssv/


Examples:

http://www2.audiokit.it/ITAENG/KitDiffusori/trasmiss/MOREL/Line162.htm

Prelude by Renaissance Audio.

 

[baco99]

Also, those woofers will work in all types of enclosures. My modified Duets are in a sealed enclosure, where the Renaissance Duets use a small folded port. They are extremely versatile.

 

[so_ein_pech]

Thanks @baco99 you did not disappoint. I really like the idea of some small transmission line towers after I listened to a pair of PMC tewenty5.23 speakers in at a little hi-fi shop in seattle that I wouldn't be able to find--much less afford--around here.

I could do a TWW, but then I would have leftover tweeters. Or I could design a simple 2-way tower (like the pictures you posted) and use the other two sets of drivers to bribe my friend who knows how to build cabinets.

 

[baco99]

Thanks @baco99 you did not disappoint. I really like the idea of some small transmission line towers after I listened to a pair of PMC tewenty5.23 speakers in at a little hi-fi shop in seattle that I wouldn't be able to find--much less afford--around here.

I could do a TWW, but then I would have leftover tweeters. Or I could design a simple 2-way tower (like the pictures you posted) and use the other two sets of drivers to bribe my friend who knows how to build cabinets.

Just go for the standard TW 2-way arrangement. Makes the crossover design much simpler too. A basic 2nd order Linkwitz Riley at about 2500 Hz. The drivers stay in phase. should be able to design something very easy and put a 2-8 ohm resistor in front of the tweeter to balance it out to your taste.