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Discussion Starter · #1 ·
Yo, what up y'all.


SO I've fought for a very long time with my centre channel. In my previous 3 setups, I had:


Athena AS-C1 matched to AS-B2 fronts. Sounded like crap, generally the reputation of the AS-C1.


So, then when I'm in my Sound Dynamics RTS-P100s, I couldn't get my hands on a centre. Which apparently doesn't matter, because the RTS centres were both MTM configuration. Instead, I used an older MTM Paradigm CC-200, which had a very similar timbre to the SDs. Not perfect, and a bit choked sounding, but better than the Athena one. Again, MTM.


Anyways, I picked up a throwaway Mirage MCC-R centre channel this weekend when buying a set of bipolars, and decided to try it out with my Wharfedale SP-89s. On one movie (Iron Man 3) I thought the voices were more natural and not as choked, though a bit strained at times. However, watching Inception last night, the centre again sounds "choked" and muffled. Tweeter on the MCC-R looks like a crappy 1/2" mylar dome...typically one of the crappiest sounding tweeters.....Mind you, the CC-200 appears to have a "polyamide" dome - guessing this is less than stellar as well.


Anyways, this got me thinking......should I be trying something different for a centre? FYI, the matched centre for my Wharfedale Sapphire SP-89's is a Sapphire-CR, which looks about the same as the Mirage, excepting a tweeter that doesn't appear to match the towers! It looks like an afterthought "guess we need a centre for this system" kind of centre.


Gah!


CC-200 is -3db at 60Hz, and is +/-2db from 100Hz-15Khz off axis. The Mirage says 60Hz-20Khz +/-3db. Ratings look quite similar.....

Idea #1: 2 Bookshelves for Centre


Now in my LR, we have changed our setup to where there is now 2 sweet spots. So, to set up the centre facing forward, both main seating areas are off axis. The centre sits at slightly above tweeter level on the mains, roughly 44" off the floor, or a bit above ear height.


So looking at the "split" sweet spot, I was thinking that possibly a pair of bookshelf speakers (I have some Mission 760s) might make a good centre, with each speaker toed out to project directly at each sweet spot. Plus, I picture them sounding better than the Paradigm or the Mirage. I know there can be sound cancellation when using two mids, but I wondered if toeing them out might help with this, especially if the two tweeters are together. the angle that I picture the cones of sound overlapping in should be the dead spot between the sweet spots.


Not worried about impedance either, as in series, the Missions should come in around 12 ohms, fine for my unit to drive.


I've read this is not a great way to approach the issue of a centre, but I wonder if this is sort of a magic bullet for me to use?

Idea #2: Replace a tweeter


Is it better for me to look at replacing some drivers? The Mirage is an interesting box, with an angled front baffle, dual front ports, and dual 4.5" drivers. The Paradigm is a rear sealed box.


However, both sound kind of chokey, likely due to the poly/polyamide tweeter. Wondering if swapping in a 1" silk dome might be a good idea?

Idea #3: Crossover change?


Centre xover is set at 100Hz - wondering if this is too high for natural male voice reproduction.....

Idea #4: Custom build own 3-way centre


It sounds like a lot of MTM/Centre issues are solved by going to a 3-way config, but nothing exists for my speakers.....would it be of value to track down another old Sapphire SP-87 or SP-89, and cobble its parts into a custom cabinet?


Gah!
 

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Discussion Starter · #3 ·

Quote:
Originally Posted by ex-labdriver  /t/1522970/crummy-centre-channels-d...eeter-crossover-burn-house-down#post_24494185


If you already have a couple of spare bookshelves, it would seem easy enough to try Idea #1 & see how it sounds.


Experimenting is half the fun of this pastime, ha!


TAM

Yeah, but then some person will come over and say "Scooter, didn't you know about wave interference, and its effect on timing and wave response?" then laugh at me.....
 

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Quote:
Originally Posted by ScooterMcTavish  /t/1522970/crummy-centre-channels-d...eeter-crossover-burn-house-down#post_24494678


Yeah, but then some person will come over and say "Scooter, didn't you know about wave interference, and its effect on timing and wave response?" then laugh at me.....

Scooter, didn't you know about wave interference, and its effect on timing and wave response?



Craig
 

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Discussion Starter · #6 ·
Well, came up with a solution, anyways.


I pulled out the backup Onkyo amp, and hooked it up to different A-B speaker comparisons to see what sounded better. The competitors were:

- The Mirage MCC-R, 1/2" mylar dome tweeter, 2x4.5" mids, dual front ported

- The Paradigm CC-200, 3/4" polyamide dome tweeter, 2x5.5" mids, single front ported

- The Mission 760, 3/4" fabric dome tweeter, 5.25" woofer, front ported

- A Mission 760i, 3/4" fabric dome tweeter, 5.25" woofer, reportedly better xover and woofer, front ported

- An old slightly odd Acoustic Research Holographic (MC.1) centre channel, 1/2" fabric dome tweeter, 4" woofer, 2x4" passive radiators, acoustic suspension


I tested all 5 using the A/B switches on the receiver, and listened to three different genres of music; rap to test bass extension, pop to test overall balance (and with the bass dialed down, test top end), and thrash, because I like thrash. Test subjects were myself, and my 15 year old daughter who has been edumacated about the importance of a good stereo system.


Bass extension was not a big concern, as all were able to go below the 100Hz that my AVR's crossover was set at. Knowing I did have options to 80 and 60Hz did have some value if I was unhappy with a particular soundtrack/deep voice actor combo.


Net results were:


Mirage - Best balance between bass and treble, with solid excellent midrange. Second best of the bunch, but would benefit from a tweeter upgrade, as the 1/2" polymer done hit good highs, but was strident and sloppy in their presentation.


Paradigm - Best bass extension, and didn't sound strained or incapable when running the rap. However, was a bit laid back at the top, and what was there was less them precise. Again, a bit sloppy. Mid was very scooped, causing me to believe that vocal reproductions could be variable based on the frequency of the speaker's voice.


Mission(s) - Could not hear a discernible difference between the 760 or the 760i. Found both tended to break up under power, and got a bit bloated and pushy in the mids at volume. The tweeters were smooth, but also a bit laid back, and missing the sharper top end I'd expected. Additional bass really compromised the speakers' ability to present midrange well.


AR - It was sure fun pumping the bass into this guy, and watching the passisve woofers rock. An interesting choice as well, as it does only have two drivers (TM) in the cabinet, helping remove the effects of wave interference. Overall the best presentation of all speakers tested, with a very tight mid, and clear, focused, non-strident highs. The lest likely to go deep, but also up to the 100Hz crossover I have on my AVR.


Net result, the A/R is currently in my system.


Not a bad way to test the speakers against each other, and actually a lot of fun.


And from this experiment, I have concluded that the Mirage may come back into play at some point. However, it certainly needs a tweeter upgrade to help it reach its potential. The Paradigm is going on Kijiji, as are the 760s.
 
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