• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Speaker recommendations for MC7270

C

Chevy Kevy

New Member
Hey Guys,

First off, I just wanted to say that I know this is a very vague question. I'm not new to this hobby by any means. I'm just new to the world of McIntosh.

I recently aquired a very nice pair...MC7270 and a C34V. Both units are in perfect working order and are sure a treat. I thought I had the right speaker picked out (had the speaker before I bought the Mac) but it appears it's not ideal for my setup. The speakers that are not working out are the Alon IV. They dip down to a 3ohm minimum and the 7270 just can't quite keep up at higher volumes. The power guard kicks in pretty early and the meter lights dim when I crank on it. I have the amp plugged into a dedicated AC wall outlet and I've done all my triple checks (wires, cables etc). I am now running a nice pair of B&W Matrix 803 which sounds wonderful. The 7270 definitely handles the 8ohm nominal / 4ohm minimum load better. Even when I get a song with a strong bass passage the meters want to slightly dim at high volumes.

I guess I would like to know what kind of speakers everyone is running with their gear. I'm under the impression that it would be ideal to find a speaker with an 8ohm nominal impedance with a 90+db efficiency rating?

Thanks for the input!
 
Register to hide this ad
Your amp is quite powerful and not sure that you really need more than 90db speakers.
I love KEFs and running 105-2 with MC2205... and 103/4 with tube MC60; both with good results.
I would imagine your Matrix sound great.
 
Have you tried the 4 Ohm taps with either pair? Just because the Power Guard lamps flash on occasion and the meter lamps dim doesn't mean you're overloading the amp - it means you're jammin!

The MC7270 should be able to drive those Alons with ease. You just need to choose the output taps that provide the best match. Don't be afraid to experiment a little - not like you're gonna' hurt the amp. If you still can't get the output you desire you may search for a higher current Mc amp - like an MC7200, MC7300, or MC2600.

I've run dozens of various speakers over the years off my Mc amps with zero issues. I've also owned four MC7270s.
 
Damacman - I've tried all the taps with the Alon hooked up and they really didn't make a difference. They sound great but it just seems like the amp runs out of power very early. I'm talking when it gets up to 27+ watts the power guard lights start coming on and the meter lights dim. Just never experienced anything like that. The B&W definitely lets the 7270 act in a more comfortable way being an easier load.

I'm going to stick with the 7270 and experiment again this weekend with both speakers. The amp isn't going anywhere and I'll try a different speaker before I sell/buy another amp! I just wasn't expecting the amp to act like it was being robbed of power or juice at those volumes. That's why I'm trying to see what others are running or if they've experienced what I am?

I have a set of beautiful JBL L166 as well but I feel like the Mac would be outclassing those speakers. Kind of like buying a Lamborghini and putting a small block Chevy in it.

Thoughts?
 
West coast Amerucan rock and roll sound..........there are a lot of JBL fans that would say the JBLs would run circles around your other choices.

While the JBLs were never my favorite the 803s certainly were. The 803s also have a impedence drop below 4 ohms and definitely need to be run off the 4 or even a 2 ohm tap.

The meter lamps are wired off the power transformer direct. When a client would have a similar complaint as yours I would go out to their home with the variac off my bench. With a volt meter would show them their sagging AC voltage then crank up the AC voltage to 122 volts. The meter lamps might still dim a little bit but the PG, showing distortion of .5% I believe in the MC7270 design, would have to be pushed real hard to come on.

You might need a vist from a electrician or at least restructure what's plugged onto the same AC leg as the amp.
 
If you follow the recommended practices of keeping the speaker lines short or the internal resistance of the speaker wire less than 5% of the speaker load, I would say a 7270 with the ability to put out over 300 watts will drive any speaker with 90 db sensitivity or higher adequately for 99 and 44/100s % of the time. That is unless you are trying to fill a monster of a room. I can remember using less power for Peter Paul and Mary concert with 7000 people in a Basketball arena. Even ML-4's and XRT 20 and 22's work fantastically with that kind of power in the average room. I have seen XRT 28's and XRT 1k suck all the power out of a 402 and 452 in larger rooms, but for most folks if your listening distance is around 10 ft those speakers would be happy with a 7270.
 
Hmmm . . . well, the MC7270 isn't a spring chicken anymore and yours could be 30 years old or so. It may not be performing to spec and need some attention. OTOH, like c_dk explains, there may be some electrical maladies in your home that are responsible for excessive voltage drop at the outlet as the amp is working hard to make the power required of the load it's driving. A quality DMM with the ability to record MINimum voltage over time could shed some light. Who knows, that could be as simple as the outlet the amp is plugged into being a cheap builder's outlet with the wires stabbed into the rear of it. I can't tell you how many times I've been to that show.

I've pretty much used 10 AWG speaker wire for any of the big Mc amps for the last 25 years to minimize loss between the amp and speakers.

Keep us posted.
 
I used to run my 7270 with a C34V and it's a terrific combo! I have B&W 804S speakers and used to run them off the 4ohm tap. I only very, very rarely had the amps at 27 watts. At that level the house would start shaking.

Perhaps get the 7270 checked out by a tech? I have two of them, and they are currently being serviced. They are getting a little old, but my tech says they are truly wonderful, and easy to work on.
 
I have had to have the power pole transformer replaced for 3 customers over the years...in all three cases all three whole house voltages would sag down to less than 100 volts. Helps to document measurements and have as a customer the master from our local power company that attaches the monitoring equipment to the meter.

'Another one? was his usual response. What is your hint there is a problem"....."3 matched mid/tweeter sets for KEF105s.....with 90 volts off the pole we figure his Carver Sunfire amp was putting out maybe 40 watts", I replied the last time.

With no PG or any amp indication, the mids and or tweeters the voice coils were melting........at over $300.00 a set if I remember correctly.
 
Hello Kevin:
Do you have a "Kill-A-Watt?" You could at least read the line voltage while the amp is working.
 
Chevy Kevy said:
Hey Guys,

First off, I just wanted to say that I know this is a very vague question. I'm not new to this hobby by any means. I'm just new to the world of McIntosh.

I recently aquired a very nice pair...MC7270 and a C34V. Both units are in perfect working order and are sure a treat. I thought I had the right speaker picked out (had the speaker before I bought the Mac) but it appears it's not ideal for my setup. The speakers that are not working out are the Alon IV. They dip down to a 3ohm minimum and the 7270 just can't quite keep up at higher volumes. The power guard kicks in pretty early and the meter lights dim when I crank on it. I have the amp plugged into a dedicated AC wall outlet and I've done all my triple checks (wires, cables etc). I am now running a nice pair of B&W Matrix 803 which sounds wonderful. The 7270 definitely handles the 8ohm nominal / 4ohm minimum load better. Emven when I get a song with a strong bass passage the meters want to slightly dim at high volumes.

I guess I would like to know what kind of speakers everyone is running with their gear. I'm under the impression that it would be ideal to find a speaker with an 8ohm nominal impedance with a 90+db efficiency rating?

Thanks for the input!
Click to expand...

B&W is a very good match to these MCs. You can look at 802N for them - should be a good match.
 
Alright, getting back to you guys. I know the amp is in perfectly good working order as I purchased it from Audio Classics. Great company to deal with by the way!

I did indeed check the line voltage out of that AC wall outlet and it's reading 120v. When the amp is playing it actually doesn't dip/move much at all. I need to take a reading directly from the outlet on the amp since when I did the test I had an extension cord plugged into the back of it so it would be easier to control the meter leads.

I had quite a bit of time last night and this morning to get some critical listening in. The B&W sure sound magical. Even with the Alon IV having a 3ohm minimum, I find the 7270 struggling to keep up at loud volumes. If I had to guess, the AC voltage is sagging to an extent. Running the easier load B&W helps not notice it. I'm perfectly OK running the B&W as they sound every bit as good as the Alon IV. It's a personal preference if I would have to guess.

I can crank up the 7270 with the B&W and it hits power guard right at 270w or so like it should. With the Alon IV, it would hit wayyyy sooner. Not a problem with the amp, just something I have to deal with from my electrical service. I'd be curious to find another tower type speaker that is even more efficient than the B&W to see how that compares?
 
for home operation I never liked to see a customer run his amps sustained above the -3 or 4 level. There are those instances where the complex impedance of modern speakers can dip below the rated impedance sucking all the current the amp can produce. Fortunately for MAC owners you just drop down a tap on the auto former, look for a MC 7200, or two MC1201 or 1.2 k. That ability to handle peaks and impedance mis matches is what the new amps have over the old! Assuming the old amps are working like new. Also Mono amps handle compromising issues better than stereo amps. Your less likely to notice a problem if one channel sags for a brief moment, than if the entire presentation collapses. That's another advantage to true bi-amping using an electronic crossover. I mean the ear isn't going to pick up a small change in the bass if the HF channels are OK as is the remaining bass channel. It would be neat to have 14 MC 301's for that reason, but I'll stick with my two 207's.

And remember guys your ears aren't linear either, when you get above the 95 db level area the internal workings of the ear sort of clamp down to protect the inner ear. Of course if you have been imbibing in adult stimulants or depressants your ear will be susceptible to damage, so be careful. I know its fun to feel your thighs being modulated and your breath taken away, but that has nothing to do with your ears.
 
I have an opportunity to grab a very nice set of ADS L1590. I've been wanting these for a long time and they never pop up for sale around here. They are 90db efficient like my B&W but they don't drop down to 4ohm like the B&W do from what I've read. Anyone have any experience with them? I know they sound great as I've heard them on a Mac system before the gentleman sold his amp.

Thoughts?
 
Sounds to me like you could cross those off your bucket list while at the same time buying a speaker that may work better for you ....
 
Did you ever hook your amp up in mono (550 w) and see what it sounds like running one speaker? Can you turn off the Power Guard on that model? You never really stated how loud the listening level really is when the amp begins to "run out of gas."
 
jlovda said:
Did you ever hook your amp up in mono (550 w) and see what it sounds like running one speaker? Can you turn off the Power Guard on that model? You never really stated how loud the listening level really is when the amp begins to "run out of gas."
Click to expand...

I never did that. Audio Classics honored me sending the unit back to them to triple check everything. The amp is fine. It's just me realizing a serious speaker load on this amp isn't the best combination. Even though it can 'handle' it, it still doesn't like it at higher volumes. This is a combination of that, and the service running to my house. Like others mentioned, I'm sure I'm getting a voltage sag when the amp is drawing more juice up top. No biggie, it was a good learning experience. I'll stick with a more efficient speaker and call it a day.

The B&W are doing the trick but I'm always open to try other speakers. That's half the fun of this hobby if you ask me! Also, you can not turn off power guard on this model from my understanding.
 
Forget about more efficient speakers. Anyone who needs to have their McIntosh amp's power guard lamps flash during what they believe to be comfortable listening levels, needs more efficient hearing aids. :beerchug:
 
I running a 7270 and I can't imagine turning it loud enough to get the power guard lights to come on, it would make your ears bleed.
 
You must log in or register to reply here.
Back
Top Bottom