Ultimate Advice MC2300/MC2500/MC2600

Now the Question brought up by autoformers. Yes, they provide a great function. The serve to center the speakers impedance curve to the output transistors best performance. It allows Mac to use fewer output transistors, smaller heat sinks, and a smaller power supply to drive loads less than ideal. Remember a 7200 could drive 2 ohm loads with very low distortion and high current at levels close to 500 watts and 1 ohm loads, too with out autoformers. But as Davie O. asked, "AT what cost!" It wasn't until the generation of the MC 501 that could drive 4 ohm and two loads from the 8 ohm tap that autoformers came into their rightful place still meeting specs, The 2205 2105 2255 etc if asked to drive complex ported or speakers with high ordered crossovers where rated at 8 ohms were actually closer to 3 ohms, were in big trouble. Some folks will tell you even today because of the complex impedances of a XRT 1k they should be driven from the 4 ohm tap rather than 8. Fully balancing the amps has helped,too and the new thermal tracking devices keeps distortion down with these mismatched loads, science goes forward and the sound gets better, We hope!
 
Finally, your JBL's are rated at 80 db at 15', which would be about 92 db 1meter 1 watt. A respectable level in the scheme of things at home. If your a listener who listens a degree above the average as expected of an recording engineer or sound professional at 85 to 90 db with a crest factor of 10 that would mean 10+ watts at 1 meter. And lets say you have a moderately dead room and listen at 12' that means you need 60 watts of peak power. So you have a safety factor of 7.5 db with your 2255 and your speakers. If the room is lively have more of a factor, but will want more bass to balance so turn dow the midrange and highs down't turn up the bass. JBL woofers from that time can take a lot of power but they become mechanically non-linear at a point. Usually around 150 watts, with the remaining power going to the padded down mid horn and tweeter. So yes you can drive them with bigger amps, but the power is for naught, if your trying to maintain linearity and realism. So your maximum level in the listening space is 116 db peaks and 106 db true RMS. Now if you allow the power guard lamps to just flash that allows another 4 to 5 db or 110db of average level, Which is enough to produce full orchestra, jazz, organ, levels, but not quite enough for R&R or CW concerts. You need another 6 db . I suggest you start looking for more appropriate speakers to full fill your needs. In this case professional JBL, EV, Mac XR290's, XRT2, Magico Q5, Q7. Get's ridiculous doesn't it. How about some Klipsch corner horns where you would only need 40 watts. They produce 105 db 1 meter 1 watt. That's 12 db more output with the same power. Big JBL are just as or more efficient than Klipsch and the sound will be more to your liking. Go look for JBL studio monitor, maybe you can find a good pair at a reasonable cost.
 
When listening to certain pieces of classical music the peaks can be quite amazing. I have seen 60+ db between the quiet passage and the full crescendo of the orchestra.

As far as duplicating the insane levels for R&R/Heavy Metal concerts while in the front row, I will never do it. I have the capabilities but I really hate the excessive SPLs. That is another reason that I will not go to a movie theatre. The last movie I saw in a movie theatre was Star Wars...the first one with Hamill and Fisher.
 
Rich, you really should get out more often.

If something causes me pain (My Ear doc says I have unusually sensitive hearing.) then I avoid it. Movie theaters are just too loud.

I do love to sit in the front rows at a classical concert. If any sound reinforcement is done, it ruins the experience for me. I can stay home and hear music played through better amplifiers and speakers.

The reason I mention the MC2500 is due to the fact that they are a little cheaper than the MC2600 and they can perform as well as a MC2600 with a little effort. I believe that if someone fully populated the heat sinks with output transistors, 600 watts could be obtained. I never seriously considered changing the amp so that it can produce 600 WPC.
 
Hi,

I would like to add to this thread as I finally managed to get a good condition MC2300, and I have MC2600 and MC500 and I did a shoutout playing passive jbl 4345.

I don't understand why the MC2300 sounded like the most powerful of the three. There's a post that say that the MC2300 is like the Dirty Harry and I know what he meant now. It's not as warm or smooth as the MC500 or 2600, but it has balls. If I can only keep one it would have to be the 2300.

Cheers.
 
Its a mazing to me how people love distortion, and that's what you are listening to when you push your 2100, 2105, 2300, 275s, 2301's. People love distortion, its gives a particular characteristic to the sound. The distortion can be in many forms, poor signal to noise, intermodulation, harmonic, frequency response, TIM distortion, etc. Amps with power guard have distortion, too. Compression. But we have learned to live with that and you don't blow up speakers while the distortion takes place. Everything you listen to off air is compressed, most popular music is compressed. So unless your speakers produce over 100 db 4 ft 1 watt and can handle 100 watts continuously, you will eventually need power guard. That being said with my speakers approaching 96 db sensitivity with MC207 amps I have never seen the Power Guard lights flash, but that doesn't mean they haven't.
 
twiiii - you certainly do make a good argument. I have a disc with a Thelma Houston (from a Sheffield recording) song that is recorded with varying levels of distortion. It's next to impossible to distinguish the clean recording from the one with 5% distortion, even at low levels when you're really listening.

When it comes to loud, I'll agree with you that there is a certain amount of distortion that most will find acceptable, even though we'd say otherwise. In subwoofer systems, it's pretty widely accepted that 10% clipped is found to be acceptable by those with an ear towards high quality sound reproduction.
 
I am going to make a stretch now. I have always preferred Altec drivers over JBL in most applications. JBL made drivers with phenolic diaphragms as did Altec. They also made almost identical drivers using Aluminum diaphragms. In sports arenas where they were trying to get every last db designers would choose the phenolic driver over the driver with Aluminum. Well if you listen to the two you hear an edge with the phenolic that sum of us at Syn-aud-con think is a combination of resonance, phase distortion and cone break up. This is the sound I hear when pushing a 2300 to far. When using 2300's with discos I used UREI's famous LA-4 limiter to keep a lid on things. I didn't pay attention to the needles but set the levels with a dual trace scope comparing the input to output in the differential mode and when I could see any distortion I backed off the gain a touch. The quality of the sound improved for me and yes like power guard the level seem to drop, in fact did drop. But the bass was firmer and the edge was gone. And the customer wasn't having to pay for expensive diaphragms or tweeters.

Now a lot of guys suffer from HF hearing loss and there fore aren't as sensitive as the rest of us and women to HF distortion. So we'll let you slide preferring 2300's. That' doesn't mean we like Krell, Ayre, Threshold or other amps with their screechy distortion in the highs either. In fact they are worse than a 2300 ever thought of being. So even though I carry on about those dirty old distorted 2100 and 2300's I owned and installed. If push came to shove I would own them again if I had to choose between X brand and a pristine 2300. But I would need 7 of them.
 
twiiii - how much power did you guys install in the average disco back in the day? Are we talking like 3,000 watts or 30,000 watts?
 
4 2300's were average in the beginning. The last big Mac disco had 4 2500's and 4 2600's. From then on it was either Crown or QSC and the power just got crazy. But the fun and artistry were gone by then. The last disco with Mac had 4 Klipsch double W boxes with 8 Altec 3156 drivers that were cut down from 16 inches to 15 inches. That required two of the 2600's. For the mid woofers we used 8 La Scala bottoms, with Altec 515 Hp woofers another 2600. The horns were 4 MR 94 with 8 291's. a 2500. The tweeters were 16 MR 902's another 2500. The DJ monitor speakers were JBL 4330 as I remember with another 2500. The last 2500 was used for JBL monitors in the Bars. The remaining 2600 was used for the for fill speakers that were fed with a mono signal via a Lexicon time delay. We used the commercial Heresy in the tapered corner cabinet laying on its side . I don't remember how many. but each curved booth had one. So how loud was it well a Klipsch w cabinet with 2 3156 is a bout 106 db 1 watt so 600 watts would be 133 db calculated, but do to compression I figured 128 db. Any way it was easy to see peaks over 124 db at 32hz 1/3 octave and 115 db continuous in the middle of the floor which could hold about 250 dancers. The most important frequency as I remember for disco is around 43 hz. Thats the frequency that gets your thigh muscles and legs moving. I always voiced the system to be flat from 70 to 7,000 hz with a 6 to 8 db roll off at 16.3 khz depending on the acoustics of the club. Below 70 hz down to 32 hz was elevated 6 to 8db. It gave the bass that tight taught quality discos are famous for and yet with a punch or kick that could almost buckle your knees.. I could always tell when the DJ had been tampering with a system just by walking on the dance floor at 1 watt levels, Fortunatly, power guard only let me down once. The mid horn amp wiped all mid range diaphragms on the Altec 291 drivers. $1200.00 The DJ's had changed the lower crossover frequency. He and his partner didn't have a job the next day and all their personal CD's and LP's were confiscated until they paid the over $3000.00 bill. Being in Mexico there were no sound level regulations, ever. I remember going to the different Charlie clubs throughout Mexico and their systems could be pretty raunchy with big JBL Lenses for highs and mids with JBL or CerwinVega folded horn or W boxes for bass.

I did 4 Discos in Condo hotels using all Mac amps and speakers. That's when we found out the crossovers in ML series had underrated caps and resistors in the crossovers and that 2300's definitely needed limiters. We used 4 ML-1's on each channel of a 2300 with 16 being over the floor at 12 ft elevation . Then we put 4 or 6 ML-2 on the floor using only the woofers to boost the bass. The floors were pretty small with may be 60 to 80 people being able to dance at a time. If they were doing Hustle line dancing demos then may be 24 people could fit. It was a great time for me. I learned to dance again. I Stayed in very nice upscale hotels and got spoiled eating gourmet dishes especially prepared for me. I met a lot of great people professionally and personally. It was a great 10 years of full time hard work in the 70's and 80's. My last service call was to a Disco club in Juarez Mexico in 2004. It had Klipsch system with Cerwin Vega woofer boxes with Altec 18 inch woofers. It used 7300's for the highs and mid woofers and a 2500 for Heresy fill speakers and 2 2600's for the woofers. Bozak mixer, Pioneer CD players and SL 1200 turn tables. I didn't mention but Bozak was my favorite DJ Mixer. It had a sweet sound that was firm on the bottom. And no mater how loud you cranked up the volume it was very quiet and never clipped or distorted. It sounded great with Stanton or Ortofon cartridges. even the Shure Sc35 was passible. My favorite monitor speaker for Dicos, believe it or not was Klipsch Belles, but they didn't have the bass necessary for DJ's who liked to have guests and party in the booth. So I switched to JBL's 4330 and 4335's among others, but I was never happy. Let's face it I didn't have room for Rudy's big Berthas. Sorry I'm so long winded. My apologies.

And to those of you who own 2100's and 2300's. There's an on going thread at the Bozak site where we discuss how well the amps work with Bozak speakers being bi-amped. I prefer direct couple amps to get tighter bass and the newer amps for cleaner highs. So we started labeling andf referring to 2100's and 2300's as being dirty and gritty old amps, though we know they aren't. Its not meant offend anyone. Its like the Catepillar engine owners saying " if it isn't a Cat, it's a DAWG." Its all in jest! As a Cummins Dawg owner 4 times over, that's the way I take it.
 
Hi,

I would like to add to this thread as I finally managed to get a good condition MC2300, and I have MC2600 and MC500 and I did a shoutout playing passive jbl 4345.

I don't understand why the MC2300 sounded like the most powerful of the three. There's a post that say that the MC2300 is like the Dirty Harry and I know what he meant now. It's not as warm or smooth as the MC500 or 2600, but it has balls. If I can only keep one it would have to be the 2300.

Cheers.

depending on where you are I could take that 2600 off you since you dont like it. :)
 
Hi,

I have the good fortune of acquiring a mint condition MC2500 recently, it even came with the original Mcintosh box and wooden platform which the amp was bolted to when it arrived.

Now I have in front of me MC2300, MC2500 and MC500, three successive generations of high power solid state amps. Now I know why the 2300 sounded louder than the other two, it's because of the input sensitivity is set at 0.5 V for the 2300 which is much lower than the 2 V for the MC500 and 2500(you can switch between 0.75 and 2 V for 2500).

Now for the sound, it does show the improvements for successive generations of Mcintosh power amps. Between the 2300 and 2500, the 2300 does appear to have more slam, but the higher damping factor of the 2500 offers better control of the woofer and as a result you can hear more details in the lower frequencies , bass is more articulate and control. Bass lines are easier to follow on the 2500. As for the high frequencies, the 2300 can sound harsh when pushed, whereas the 2500 performed better and remained composed. Not sure if it's due to the power guard.

Finally, I must say the MC500 offers that best set of compromises, it does not have the bass slam of the 2300, nor as articulate as 2500, but highs are open and clear and never sound hard even when pushed to extreme levels.

One last word on the 2600 which I used to own, even though some say its the 2500 with more output devices, it sounded very different to the 2500. It does not have the speed and clarity of the 2500. And surprisingly even though it has higher power ratings, bass sounded a tad slow and less articulate compared with 2500.

Last but not least, I must say that I love all of them for the cool looks, excellent performance and reliability.
 
Here we go again . . . lol. And the debate continues! Why on earth would you have sold your MC2600?
 
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For those that are wondering about PowerGuard, I have a pair of MC2500 amps and one is equipped with a switch for the PowerGuard. McIntosh made one of my amplifiers for driving underwater transducers for the purposes of charting the floor of the Gulf of Mexico. Anyway, I can turn the PG off and on at will. There is no difference in the sound quality measured or perceived no matter if it is on or off.



I like the Autoformer. It makes the amp more stable and consistent no matter what the speaker load is. It also prevents output destruction if the speaker suddenly gets disconnected or shorted. Amps without output protection will usually pop their outputs if something happens to the load mid-session.

pg-switch-small.JPG
 
For those that are wondering about PowerGuard, I have a pair of MC2500 amps and one is equipped with a switch for the PowerGuard. McIntosh made one of my amplifiers for driving underwater transducers for the purposes of charting the floor of the Gulf of Mexico. Anyway, I can turn the PG off and on at will. There is no difference in the sound quality measured or perceived no matter if it is on or off.



I like the Autoformer. It makes the amp more stable and consistent no matter what the speaker load is. It also prevents output destruction if the speaker suddenly gets disconnected or shorted. Amps without output protection will usually pop their outputs if something happens to the load mid-session.

pg-switch-small.JPG

ok so maybe you can answer this, I did have a 2205 once that allowed the powerguard to be switched off, always meant to try it to see if powerguard affects the sound like you read here from time to time. have you ever tested that theory on this amp? if not can you? I always meant to do it when I had the 2205 but never did, I have read about these modded 2500's but have never seen one, thanks for posting the pic.
 
I have heard only a 2255 vs a Mc2300. I prefer personally the 2300 but I thinks the condition of the amp is essential. The 2255 I listened to was in good original condition (I know it was a steal for for 1100 bucks on Craigs but I passed) but was maybe not 100% up to spec whereas my 2300 just had a complete overhaul.
 
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