MC275 Bass issues

[tgyeti]

While listening to Donald Fagan's "Kamakiriad" for the first time through my 275 I found the bass intro to "Snowbound" to be quite bloated and boomy. If the starting point on my volume dial on my preamp is "7" on the face of a clock, I was only at "10" or so. Not nearly out of what I perceive to be the range for "dedicated" quality listening but still medium loud. Speakers are Spendor S9's (90db) and tubes are OEM.
Any ideas on how I can tighten that bass up? For the record I'm a life long solid state guy. Are my ears prejudicing the sound?


Thanks

 

[nsgarch]

insufficient info

What speakers/preamp/cabling do you currently use? Are you driving the amp SE, or XLR? Source(s)? (brand and model)

Without your providing complete system information, you have to regard any advice/remedies as pure speculation and not actionable. Unless, of course, by some actuarial/statistical miracle, a respondant has the exact same system as you do. But how would either of you know that?

 

[tgyeti]

What speakers/preamp/cabling do you currently use? Are you driving the amp SE, or XLR? Source(s)? (brand and model)

Without your providing complete system information, you have to regard any advice/remedies as pure speculation and not actionable. Unless, of course, by some actuarial/statistical miracle, a respondant has the exact same system as you do. But how would either of you know that?

Thanks for your thoughtful response but I respectfully disagree. Generalities can be assumed. For example, certain tubes carry certain characteristics with sound, yes? Even I know that and I'm a SS guy.
But here you go:
Speakers: Spendor S9's (I mentioned that)
Preamp: Gamut C2R
CDP: Accuphase DP-57
All interconnect and speaker wire: Analysis Plus Crystal Oval, RCA SE
Power Chords: Magic Power power chords from Signal Cable
Rack: MapleShade Samson v1
Hardwood floors
Area Rugs
Moderate amount of furniture
Speakers away from wall 4'
No other acoustical treatments
Entire set up is set up the same way it was with the previous SS amp, a Belles 150a Reference (a fine amp I might ad)
Weather: Clear, cold ..... and liberal (Minneapolis)
Wife: Good mood
Cat: upstairs in sun spot



I hope that covers it.

Now, having said all that, generalities can be assumed. As the above mentioned song has a very "meaty" bass line (do you know he song? artist?) Is this bloated feel just a characteristic I need to get used to with the 275 or is there some tweaking I can do to tighten it up.


Cheers, and thanks again.

 

[ibog1]

I'd say that if the system is identical with the exception of the amp, then the amp does indeed sound as you describe. You will have to fiddle with the room or cables or speaker postioning and or seating postion to try to get what you want. I have that amp in version 4 and do not find the bass to be as you described.

 

[Impedance]

Try a better record?

 

[wolfcub]

Which speaker tap are you using ? If it is the 8 ohm tap then experiment with the 4 ohm tap and see which sounds better (the 4 ohm tap will better be able to control bass due to it's lower output impedance but you may lose some headroom if you are driving 8 ohm speakers with it) - see what sounds better ....

 

[ron-c]

You may want to try some different cabling. Designs for solid state sometimes are not so great with tube amps. Usually simple is best with tube amps. Some high quality copper speaker wire may be an improvement in this application.
Your speakers have a fine reputation but with some speakers a single MC275 just doesn't have enough grip on the bass. If anyone has more experience with your speakers maybe they could chime in.

Thanks,
Ron-C

 

[PHC1]

My solution to the bass was an active x/o and 2 subs to take everything below 70Hz off the 275. You may not want to go that far. I gotta say that in that configuration the 275 out-did the mighty 501s in sheer musicality!

FWIW, I did find the Svetlana Winged-C KT88s to be a slight improvement though.

 

[PHC1]

I have Spendor S8e on my main system. My speaker cable is simple 8AWG OFC.
I also use Kubala-Sosna Fascination XLR direct from CDP to 2102 amp. You may want to check your distance from the wall as this will affect the bass tones. I have very good bass response with my set up. So, try and "tune" in your bass sounds by repositioning your speakers. I hope that this helps.

Thanks for the input! I don't have any bass issues what so ever anymore but the original poster may find this helpful. :thmbsp:

 

[nsgarch]

more specifically

Thanks for your thoughtful response but I respectfully disagree. Generalities can be assumed. For example, certain tubes carry certain characteristics with sound, yes? Even I know that and I'm a SS guy. Is this bloated feel just a characteristic I need to get used to with the 275 or is there some tweaking I can do to tighten it up. Cheers, and thanks again.

Sure you can generalize, but the degree of generalizing is inversely proportional to the usefulness of those musings. You have a very nice system, and the old and new amps are of about the same 100W power. But clue(s) to the bloated bass you report are that 1.) it's an intermittent phenomena and source dependent, and 2.) a look at the speaker's enclosure design and (somewhat restricted) low frequency specification. And no, you don't have to live with it!

The bloated bass comes from the fact that the MC275 (like all tube amps, even OTL's) has a low damping factor of around 14. DF is an indication of an amplifier's ability to control the low frequency woofer cone excursions with complete precision. If it can't do that, then sloppy or 'bloated' bass can result. SS amps on the other hand, have damping factors well over 100 -- i.e. damping to spare!

My first recommendation would be to make sure your speaker cable runs are short. Not over 6 feet from the amp to each speaker if you want to take full advantage of the MC275's 14 damping factor. That should do it, but if your cables are already short, and the bass is still poorly defined, then you need to call Spendor and find out if they make a 'damping plug' for that speaker (usually just a chunk of foam you jamb into the enclosure's port) or you can make one yourself.**

This is because your S9's lo-freq response dissappears at 40Hz, and if your source material has frequencies much below 45Hz, the port will not control them and the woofer 'runs away' trying to produce them (which is wasn't designed to do) and the (tube) amp can't damp them out (even though a ss amp could.) Of course, you could buy a ss self-powered subwoofer that has a built in hi-pass filter. That way you could hear the low bass properly, while restricting the Spendors to frequencies above 45-50 Hz. The bottom line is that your speaker shouldn't have to produce frequencies lower than those for which it was designed.

Yes, the MC275 would indeed benefit from better tubes, but that won't solve your bass problem.

** Use medium density "reticulated" foam (that's foam with all the bubbles popped so the sound can go thru.) You could also use a folded up chunk of fiberglas insulation, but it's messy.
.

 

[william.keith]

Of course, you could buy a ss self-powered subwoofer that has a built in hi-pass filter. That way you could hear the low bass properly, while restricting the Spendors to frequencies above 45-50 Hz. The bottom line is that your speaker shouldn't have to produce frequencies lower than those for which it was designed.

Bingo!

 

[PHC1]

Using a high pass filter will not take away the very low bass off the 275, it will still have to produce it while the power gets absorbed by the crossover. The magic is unlocked when the 275 does not have to struggle with those frequencies but is left with all of its reserves to concentrate on everything else. 80% of power is used up by the bass. To hear the 275 with an active x/o is like listening to a whole new amp all together. The results are truly incredible. McIntosh really should build future speakers with outboard active crossovers so they can be bi and tri amped the way it really is supposed to be!

 

[nsgarch]

Basically correct, but a little dramatic ;-)

Using a high pass filter will not take away the very low bass off the 275, it will still have to produce it while the power gets absorbed by the crossover.

True, sort of. Yes the amp is still passing low frequencies (something it was designed to do quite well, thank you very much!) but it isn't driving any kind of electromotive device (i.e. a woofer) which is what 'absorbs' the amp's power. A crossover network will not absorb any power (it doesn't move and it doesn't get hot ), it just blocks-or-passes certain frequencies -- no electrical current is created by the blocked frequencies.

The magic is unlocked when the 275 does not have to struggle with those frequencies but is left with all of its reserves to concentrate on everything else.

How romantic but not true! The 'poor' amp isn't 'struggling' (as mentioned, it was designed to produce those frequencies as per its specs) -- nor is it putting out any more power because the bass is bloated and not clean. The amp simply can't control that particular woofer below 45Hz because 1.) the output transformer of a tube amp limits damping and 2.) a woofer in a ported enclosure loses control below it's operating frequency; if it were an acoustic suspension woofer, that wouldn't happen, but neither would it be 90dB efficient, so you couldn't play it as loud.

80% of [amp] power is used up by the bass.

Mayber not 80%, but a lot -- however, that's ONLY if the amp is producing bass (bloated or clean) by driving a driver. If it can't drive anything at under 45Hz because those lower frequencies are filtered out, then it's not delivering any power (at those frequencies.)

 

[ron-c]

Dampening factor is not the issue but power and current are. My MI 200 amps have a lower dampening factor and will drive any woofer made but they have more current and power than the MC275. Running two MC275s in mono would probably solve the issue. More current is needed for your woofers than one MC275 is delivering. Please try a simple speaker cable as an experiment.
Using a stereo powered sub with a crossover before the inputs of the MC275 will work very well as outlined above. Crossing over at 80 Hz would relieve the MC275 of the bottom three octaves just like a home theater set up.

Thanks,
Ron-C

 

[william.keith]

Good Thread and Posts. Helpful insights for those who prefer stand-mounted speakers but want full-range sound (many floor-stand speakers would also benefit) and are not interested in a monster amp(s). Chuck Hinton advised me accordingly years ago when I acquired my LS320s and subsequently two PS112s. My 200 watt integrated amp, now the MA6600, has more than enough power for the upper frequencies while two 400 watt McIntosh amps handle the lower frequencies with ease. I can assure you that they have the current to handle their respective 12" woofer without breaking a sweat.

I also like the idea of using McIntosh powered subs since the quality of their internal electronics are consistent with the quality of the company's separate amps and pre-amps. Speaker and power components performance are in harmony.

 

[PHC1]

True, sort of. Yes the amp is still passing low frequencies (something it was designed to do quite well, thank you very much!) but it isn't driving any kind of electromotive device (i.e. a woofer) which is what 'absorbs' the amp's power. A crossover network will not absorb any power (it doesn't move and it doesn't get hot ), it just blocks-or-passes certain frequencies -- no electrical current is created by the blocked frequencies.How romantic but not true! The 'poor' amp isn't 'struggling' (as mentioned, it was designed to produce those frequencies as per its specs) -- nor is it putting out any more power because the bass is bloated and not clean. The amp simply can't control that particular woofer below 45Hz because 1.) the output transformer of a tube amp limits damping and 2.) a woofer in a ported enclosure loses control below it's operating frequency; if it were an acoustic suspension woofer, that wouldn't happen, but neither would it be 90dB efficient, so you couldn't play it as loud.Mayber not 80%, but a lot -- however, that's ONLY if the amp is producing bass (bloated or clean) by driving a driver. If it can't drive anything at under 45Hz because those lower frequencies are filtered out, then it's not delivering any power (at those frequencies.)

Power will absolutely be absorbed by the crossover, this is simple ohm's law and the reason why speaker crossovers can and do get hot and sometimes even fail.

Very high performance passive crossovers are likely to be more expensive than active crossovers since individual components capable of good performance at the high currents and voltages at which speaker systems are driven are hard to make and expensive. Polypropylene and Metalized polyester foil, and paper-electrolytic capacitors are common. Inductors may have air cores, powdered metal cores, ferrite cores, or laminated silicon steel cores, and most are wound with enamelled copper wire. Some passive networks include devices such as fuses, PTC devices, bulbs or circuit breakers, to protect the loudspeaker drivers from accidental overpowering.


The high pass filter mentioned will absorb the low frequency which in turn will load the amp down. There is no way around it. An active crossover will simply split the signal before the amp which can be handled by powered subs and the amp will never have to see or reproduce those low frequencies.

 

[PHC1]

If it can't drive anything at under 45Hz because those lower frequencies are filtered out, then it's not delivering any power (at those frequencies.)

So if you play a 20Hz test tone through the amp and speakers and those speakers are not capable of it or are rolled off below 45hz the amp will not produce any power???? The power will simply be absorbed by the crossover or the woofer will "try" to reproduce those frequencies anyway.

 

[PHC1]

The cost and complication disadvantages of active crossovers are offset by the following gains:

A frequency response independent of the dynamic changes in a driver's electrical characteristics.

Typically, the possibility of an easy way to vary or fine tune each frequency band to the specific drivers used. Examples would be crossover slope, filter type (eg, Bessel, Butterworth, etc), relative levels, ...

Isolation of each driver from signals handled by drivers, thus reducing intermodulation distortion and overdriving

The power amplifiers are directly connected to the speaker drivers, thereby maximizing amplifier damping control of the speaker voice coil, reducing consequences of dynamic changes in driver electrical characteristics, all of which are likely to improve the transient response of the system

Reduction in power amplifier output requirement.

With no energy being lost in passive components, amplifier requirements are reduced considerably (up to 1/2 in some cases), reducing costs, and potentially increasing quality.

 

[TONEPUB]

I'm with Ron on the current issue.

I've reviewed more than my share of speakers that the 275 (or any other tube amp for that matter) gets a little froggy in the bass in the same way you are experiencing.

It's always a matter of compatibility. You might ask your Mac dealer, if close by, if you can borrow a 2nd 275 to see how that works, or perhaps if you can switch to mono from your preamp, just run one speaker with the 275 you have in mono mode to see how the bass is affected. If it tightens up to your liking, then you have a pretty good idea that a pair of 275's in mono will work for you.

Otherwise you have some decisions to make...

Harbeth Compact 7ES-3's work great with the 275.

Good luck!

 

[nsgarch]

Power will absolutely be absorbed by the crossover, this is simple ohm's law and the reason why speaker crossovers can and do get hot and sometimes even fail.

Resistors are current carrying devices, and so will get warm if someone cranks the volume enough to overdrive the loudspeaker. In that case however, it's the voicecoils in the drivers that fry before any of the resistors in the crossover network.

A music signal is an alternating current of varying frequency and amplitude, The elements in a (passive) crossover which don't pass low frequencies but do pass high frequencies are the capacitors. The elements in a (passive) crossover which don't pass high frequencies but do pass low frequencies are the inductors. These devices do not PASS frequencies below (capacitors) or above (inductors) a certain frequency point which is determined by their capacitive or inductive properties respectively. The power rating (watts) of these devices is chosen based on the strength (current x voltage) of the signal necessary to operate the assiciated driver. The part (frequencies) of the signal they DON'T PASS cannot create a current, and therefore can do no work (such as producing heat or moving a voicecoil.) ABSORBTION of energy at unwanted frequencies is NOT how crossover networks do their job, and the resistors they contain are not for that purpose.

So if you play a 20Hz test tone through the amp and speakers and those speakers are not capable of it or are rolled off below 45hz the amp will not produce any power???? The power will simply be absorbed by the crossover or the woofer will "try" to reproduce those frequencies anyway.

I already covered "rolled off" (not passed.) "Not capable" is a different thing altogether. If the 20Hz signal has been PASSED to the woofer's voicecoil, then regardless of whether or not the woofer can move/respond to it, the amplifier is still producing a signal (power) at that frequency. However that unused (to move any air) power is not absorbed by the crossover (it's already been PASSED to the woofer) and it will heat up the woofer's voicecoil the same as any other part of the signal that has been PASSED to the woofer. You can even pass DC through a voicecoil (a simple way to test a speaker's polarity) without damaging the voice coil, as long as the voltage of the DC doesn't exceed the voicecoil's current carrying capacity (determined mostly by its wire size.)