Do ML-1Cs eat tweeters for breakfast?

[Bijan]

so I fired up my newly serviced gear up last night, nothing insanely loud but loud. It sounded great! This morning the right speaker sounded lifeless and dull compared to the left. I am going to switch speakers today and see if it follows the speaker or the amp. I fully rebuilt the crossovers, too.

It sure sounds like one of the tweeters bit the dust last night. Seems like this is super common for the ML-1Cs if my memory serves me correctly. Any help is appreciated. Thank you!

 

[c_dk]

Amplifier clipping eats any speaker for breakfast and in 70s vintage Mac speakers the mid domes are the most susceptible to that damage.

The black plastic cap (12mfd?) in the crossover has also been a known issue in the ML series.

 

[Bijan]

I replaced the caps and resistors. I didn't hear any clipping. I've read of a Roger Russell update for these, I'm going to look into that, as well. They sound GREAT when all is working so I'd prefer to keep them. Thanks!

 

[c_dk]

I installed a few of RRs update for locals. New crossovers and minimum cabinet mod to use Morel drivers if I remember correctly and no longer available I believe.

Is the dome open, shorted? The DC resistance should be around 10 ohms.

Check with NY (speaker works, speaker repair?) in Syracuse, they obtained all the McIntosh spares, jigs, and such when Mac parts stopped rebuilding the domes. I do know they rebuild the later 036-035 mid dome, do not know if they do the United Audio sourced original mid dome.

 

[Bijan]

Thank you for the info! If it turns out to be the speaker I'll find and contact the shop you mentioned. Could it be the 117 or 2205?

 

[twiiii]

If you read the White papers or owners manual of the Ml-1c the super tweeter is rated around 7 watts rms. and the dome tweeter around 15. 2105's and 2505's were famous for wiping out ML1 and 2 tweeters. Later amps like the MC 502 with Power Guard corrected most of the failures. I never had a ML-2 issue with 2125 and 2205's. MC2300's were notorious for smoking ML-4's, and yet 2255's worked great with the ML-4's. That said early ML series with black capacitors in the crossover failed more often than not. The XR series with improved crossovers components, fuses and glass epoxy circuit board were a great improvement. I read of Rogers updates to the ML-1 and it will out perform with lower distortion than a ML-2 and handle a MC 2205 acording to the gents at Audio Classics. Some customers drove pairs or triplets of later new ML-1s with the Dynamic MC 7200 with no issues. And a 7200 can put out a ton of power at 4 and 2.6 ohms.

 

[Bijan]

Hmmm, if it's a blown driver I will replace, leave the treble EQ knob set on flat, not crank it out, and explore my options. I love the ML-1Cs so I'm hoping there's a mod to enable me to listen louder when desired ideally.

I really appreciate everyone's advice and experience!

 

[c_dk]

It is difficult to damage a mid dome with a MC2205 amp. GG told me years ago that the introduction of PG cut warranty dome replacement by a huge amount.

Did you have the loudness and high frequency controls turned up while you were listening? How much?

 

[motorstereo]

Knock on wood I've never had a problem with either of my 2 pair of recapped ML1C's. I've played them on many different combinations of gear and even had them live in my unheated garage for over a year. But I've never pushed them to their limits either. Post recap I've also found that the MQ101 is not essential anymore. I've also learned the hard way in the past to take it easy on 40 year old speakers. Boosting the treble is something I'm very careful with. Good luck to you in finding and fixing the problem. I think they're fine sounding vintage speakers.

 

[c_dk]

In my opinion RR took it as a engineering chalenge to design speakers with low distortion with a major, major emphasis at lowering distortion in the low frequency octaves. The woofer design and attention to the voice coil magnetic gap interface, the bass eq to compensate for the dampening, Zobel network etc etc were all implemented to reduce the bass distortion. I believe he failed to address other issues, important to many of us, until forced to, starting with the XR6s, 14s and later designs.

I found the updated kits still did not address the back row seat voicing of the original ML design. I am still a row 14 or so type of guy not row 25 or 30.

 

[for_p1]

so I fired up my newly serviced gear up last night, nothing insanely loud but loud. It sounded great! This morning the right speaker sounded lifeless and dull compared to the left. I am going to switch speakers today and see if it follows the speaker or the amp. I fully rebuilt the crossovers, too.

It sure sounds like one of the tweeters bit the dust last night. Seems like this is super common for the ML-1Cs if my memory serves me correctly. Any help is appreciated. Thank you!

Either not enough power in amplifier for sound you expect. Or amplifier oscillates at high frequencies. In noth cases solution is- new amplifier.

 

[Bijan]

It's definitely the speaker. I reversed them on the power amp- same speaker sounds less lively than the other. I'm going to troubleshoot this weekend. For all I know something worked loose in the XO, but I doubt it- I replaced everything except the inductors. I'm pretty sure it's one of the drivers under the metal grill.

My speaker guy has 1/2 a dozen JBL 4311/12s in a pile in the back of his shop in various states. I think I may approach him about a pair to redo. I've heard great things about those particular JBLs. There may be a Klipsch that'll sound good to me, but I've never been a horn guy, so I don't know. I'm sure I'll eventually find a winner.

I'm definitely going to keep the ML-1Cs, as I love the way they sound. I guess I really need more efficient speakers, too.

motorstereo- I haven't hooked the MQ101 up, and I don't feel it's necessary- they sound great! Also, the 117 has a usable EQ.

c_dk- I was messing with the EQ controls and the loudness at various points last night. I must've taken it too far at some point. Ah, it's a minor inconvenience and not an expensive one. I just will chalk it up too lesson learned!

I'm going to contact RR and get his take on things. Maybe he's got a suggestion that'll help- if anyone would, he would.

Thanks again everyone!

 

[c_dk]

Well JBLs and ML1s are certainly on opposite sides of the west coast vs east coast speaker sound debate of the 70s........

 

[Bijan]

Yeah, and that concerns me, as I've always enjoyed the east coast sound. I'm hoping to borrow some JBLs to help me decide.

 

[twiiii]

I don't think RR was forced into anything. The ML series were point source speakers designed to produce Concert levels of Classical music in different sizes of rooms with a broad sweet spot to allow everyone to hear Stereo imaging and not in just the one typical narrow sweet spot. When you read his narrative on his web site he speaks highly of the advantages of line arrays as used in Bozak Symphonies, and how he adapted the principal when developing the XRT 20, 22 and 18 culminating in the XR 290, my overall favorite all time Mac speaker. Line arrays maintain the large horizontal sweet spot but prevent anomalies from reflections off floors and ceilings while extending the direct sound of the speaker into the room reducing room effects while apparently increasing the efficiency of the speaker at a given distance compared to the point source speaker systems. If you like up front sound line arrays are the answer. Line arrays have the definition of a horn, but with lower distortion, and with out the honky sound of JBL Altec and Klipsch speakers produced in the 70 and 80;s, He also speaks of the break throughs in driver design that lowered distortions, that are now used by JBL and Magico with their current coned drivers. Critically damped woofers aren't used by Mac today, but as with some other manufacurers a modified form is being used. I'm not fond of tuned labyrinths or ports for speakers, but having heard the Ik I will admit its one way to be able to increase efficiency while reducing the size of the woofers. I prefer the XRT 28 or 30 my self. But folks won't allow those designs in their homes today.

 

[Bijan]

Looking back, I think that this tweeter has been dead the whole time. I never got the 2205 even close to clipping. I also recall, when I got the first one back together with its newly rebuilt crossover that it sounded VERY dark. At the time, I assumed I needed to get used to the sound of these speakers. I would put money down that the previous owner fried the tweeter, as this setup has been together since the MX117 was new. I am glad that I most likely did not blow this tweeter. I love the sound of these speakers, and am happily keeping them until I can find a pair of AR-9s!

Also, the crossovers showed evidence of the speakers being pushed, see the attached pic- both crossovers had the same heat mark under the 6 ohm resistors. Good news- the non-functioning driver is not the dark yellow mid dome, but the rectangular tweeter. Snagged a pair for $45 plus freight!

 

[c_dk]

In almost 40 years now I have only seen one of those peerless cone type tweeters fail compared to dozens of middomes.

 

[Bijan]

Hmmmmm, I wonder if there is something awry in the crossover. Worst case scenario I have an extra pair of tweeters. I will figure it out once I get the speaker apart.

 

[62caddy]

Unless the Power Guard was defeated, an MC2205 should not have clipped in the first place.

The Mc book discusses blowing tweeters in the early Mc speakers in days before the PG was introduced. With the MC2205, they were able to play the speakers louder without damaging the speakers than the MC2105 would play - while frying tweeters in the process.

People were overdriving their amplifiers far more often than they realized.