Power required for Harbeth M40

[Redwine]

I am planning to aquire an older used set of Harbeth M40 but do read in several places that they require plenty of power to control the “lively” bass.

The reviewer Bob Neill in Enjoy the Music.com says in a 2001 review of the speakers among other “Again, you must have at least 100-150 solid watts of power AND a very good preamp - one with a serious power supply, or the M40's can be too bassy”.

I wonder if a classD amp nowadays would be able to handle this job without problems?

 

[voodooless]

I wonder if a classD amp nowadays would be able to handle this job without problems?

Yes. It’s rated at 6R impedance, so it probably doesn’t dig too far down. So the load is most likely not too hard. The efficiency isn’t very good though: 84 dB. So yes, you need a bit of power. 100W+ should be fine for many rooms. Use of of these calculators to find out how much you really need, like this one:

SPL Calculator

 

[Purité Audio]

It’s almost certainly the room you will have to deal with in terms of bass.
Keith

 

[Redwine]

It’s almost certainly the room you will have to deal with in terms of bass.
Keith

Could you elaborate on this, please?

 

[voodooless]

Could you elaborate on this, please?

It means that the room has the most influence on bass performance. An amp just amplifies a voltage. It doesn’t really “do” anything to the bass. And all halfway decent amps will sound the same, regardless of class or brand. So really you select an amp based on features and the maximum power needed, unless the speaker has some very special impedance needs.

As for the room: room modes dominate the bass response, meaning that some frequencies are amplified while others can be decreased. This can be partially fixed with room treatment and/or room correction.

If you need an amp, make sure it includes room correction. It’s the singe most powerful feature for influencing sound quality.

 

[Jim Taylor]

The reviewer Bob Neill in Enjoy the Music.com says in a 2001 review of the speakers among other “Again, you must have at least 100-150 solid watts of power AND a very good preamp - one with a serious power supply, or the M40's can be too bassy”.

The older M40s can be bassy, but it has nothing inherently to do with the electronics. The 40 was designed for use in British studios of the day, which were rather dead to allow for greater clarity. BBC studio monitors were also used on-axis, which aligned the listening axis with people using the control consoles. In order to get this (larger) M40 box aligned correctly, the 40 was designed to be situated on stands.
All this effectively reduces the bass. Put the 40 either on the floor or close to the floor, and the bass is more prominent. Not only that, but with residential rooms being by and large more reflective than studios, any speaker with relatively narrow directivity will sound slightly bassy due to imbalance between wide-directivity bass and lower-directivity upper midrange and treble. The 40 falls under that description.

Two points I'd like to add:
1) Some people think the BBC were primitive. They were definitely not primitive ... they simply didn't have the benefit of all the computerized tools we have today.
2) Don't trust anything you read in Enjoy the Music. My opinion is that if they do get something right, it's by sheer accident.

And what @voodooless suggested about room correction is point on ... especially regards the bass.

Good luck!

 

[Redwine]

It means that the room has the most influence on bass performance. An amp just amplifies a voltage. It doesn’t really “do” anything to the bass. And all halfway decent amps will sound the same, regardless of class or brand. So really you select an amp based on features and the maximum power needed, unless the speaker has some very special impedance needs.

As for the room: room modes dominate the bass response, meaning that some frequencies are amplified while others can be decreased. This can be partially fixed with room treatment and/or room correction.

If you need an amp, make sure it includes room correction. It’s the singe most powerful feature for influencing sound quality.

If possible, could I have some suggestions to relevant amps since room correction is a must?

 

[voodooless]

If possible, could I have some suggestions to relevant amps since room correction is a must?

What is your budget? Did you use the SPL calculator? How much power did it give you?

 

[Redwine]

What is your budget? Did you use the SPL calculator? How much power did it give you?

Yes, approx 150watt. Budget, I think is “what it takes”

 

[Purité Audio]

Room correction/EQ is ‘usually’ found in playback software, Roon for example and in Dacs/Streamers rarer in power/integrated amplifiers.
But yes a must.
Keith

 

[voodooless]

Yes, approx 150watt. Budget, I think is no more than 2.500 eur.

In that case, there are lots of options that easily for your budget.

Two main options:

- One piece solution like WiiM Amp Ultra, NAD has some stereo amps with Dirac, and there are a few other options as well. You could also go for an AVR and use it in stereo mode. You’ll need a higher end model for more power.
- Two piece solutions with a streamer, like WiiM pro/ultra, and a separate amp, one with Hypex, Purify or the new ICE Conductor modules. They will offer the most power.

 

[Frank Dernie]

I was going to buy used active Harbeth 40s but couldn't find anywhere in my listening room where they did not excessively excite the main room mode. I have usually been able to find a location that minimises the mode excitation (which also minimises the cut needed in any compensation).

Not many active models were made and I am not sure how powerful the amps they use are. I ended up not buying them but just storing them for their owner.

When Devialet made their bass compensation measurements years ago the M40 had amongst the highest bass exaggeration of all the speakers they measured so correction for this will be important.