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... I think you must be among the first customers to hear the new M40.1. ... I've gotten used to the sound using DSP room-correction... But I certainly have no reason to doubt that they'll be at least the wonderful speaker that the M40 already is.
That pair is the only pair in existence other than my reference pair and I made them as a special favour to Harbeth USA in recognition of the following that the M40 has in the USA; and to just double check that I haven't overlooked something.
I've been 'on the case' of the M40.1 for well over a year. It has been a hugely complex project even with Derek's help on the bass unit because two of the three drive units are new. The 300mm bass unit is of course completely new and the midrange driver is substantially different: the voice coil is much higher impedance and the metalwork in the magnetic circuit is increased by 30% to increase the flux. The cone surround is from the C7ES3. All of that means that I've had to redesign the crossover from the ground up and have had over thirty iterations of the crossover all of which simulated, wound the coils by hand, assembeld the circuits, measured the speakers (inside/outside) and then listened alone for hour after hour.
Now the existing M40 is, as you say, a great speaker. I would remind you that had it not been for VIFA discontinuing the M40 bass unit without any notice at all, we would have continued with production of the M40 for years. But we were forced to design our own 12" which, in fact, puts us in a far more secure supply position for the long term. It also meant that we could precisely specify the characteristics of the new woofer down to the last detail. Not one of our broadcast customers has commented on the M40s bass but it has been noted that in some domestic rooms where there is an unfortunate combination of thin flexible (plaster) walls on bearers and/or a garage or basement below and/or short stands that the bass could be quite generous. That is no problem if the speakers are played at a low level as it adds an attractive warmth. You are in the lucky position of solving room issues not by adjusting the damping in the room (to be more absorptive like a BBC control room for example) but by electronic means which is perfectly legitimate - if expensive.
Feedback from the market over the past ten years told me that the mid-top of the M40 was as good as it gets but if I could revisit the bottom end that would avoid the need for room treatment (expensive) or DSP room correction (complex, also expensive) and that would make the M40 a more attractive proposition in normal rooms. So that's what I've done. I could have cloned the VIFA unit but I though it a better value proposition to the consumer if we saved him the cost and inconvenience of adjusting his room - by whatever means.
As in the transition for the Compact 7ES2 (another good speaker) to the Compact 7ES3 last year, my knowledge has improved incrementally, and I've learned and developed new techniques in drive unit and crossover design. So, when we'd finished with the M40.1 bass unit, I became curious about the midrange unit and the idea took root ... 'if I could increase the system sensitivity and increase system impedance and revist the bass we'd have a universally appealing speaker'. Needless to say, the entire design process is carefully written-up and preserved in my daily Log Books. I can assure you that you made a great investment in your M40s and with your low-end-correction DSP system you have a perfect domestic-friendly system that will give you satisfaction for many years as it does to BBC (and other) engineers every day around the UK.
The development of the M40.1 has been a long complex path with some memorable steps especially some six months ago outside on a warm British spring day, measuring the new bass unit's performance, here.
Thank you, Alan, for your response and further observations concerning development of the M40.1. It really does sound like all your work and attention to the smallest details has resulted in a speaker that will keep - and even extend -all the qualities of the M40 but that will be easier to integrate into the typical user's listening room. I have no reservations concerning my M40s; the sounds they produce never fail to satisfy me.
I've been catching up all the generous reports from Mr Shaw on his new masterpiece, M40.1. Considering the well-documented details in the form of text, diagram, photo, audio and video, the wonderful speaker design attitudes and principles inherited from BBC, and the ups and downs related to production, I hope there will be a making-of documentary video of M40.1 with a brief history of Harbeth. The video would be very interesting to both the general audiophile public and especially the Harbeth lovers.
I am curious if u would be loading the 40.1 with the latest and best components :
-high end capacitors from Jantzen or Mundorf or whatever
-Silver wiring or "branded" wire suppliers or Silver Gold wires as sourced in Holland - namely used by Siltech, Kharma and Gryphon
- Cryogenic treatment for the wires and crossover?
- Bybee Quantum filters
Or would u be saving modifications/components for perhaps the next anniversary version of 40.1
Didn't really want to put you on the spot...but I had to ask.
At the RMAF show, Walter did mention the fact that the 40.1s I heard were on the non-optimal SKYLAN standards, which I believe is 22" high. He added the new 40.1s were designed to work on lower stands and should be on SHL5 stands instead.
Just as an added note, the Lyndorf room was next to the Harbeth room and they had the room correction system active for A/B comparison. The equalized sound was very smooth with a notice-able lack of boominess from almost all other rooms. As I walk back and forth between the Harbeth and Lyndorf rooms, the M40.1 sounded so smooth that, at least to my ears they do not need to be corrected.
I will post pictures from the Harbeth room later...
Thanks again for your feedback about the first public appearance of the M40.1 - its especially valuable as you have lived with the M40 for years and can make a comparison from experience.
I'm particularly interested in your comments that a) the bass better integrates with the typically flimsy wall construction of the hotel demo-room and that b) the overall presentation was very smooth. After the 12" bass unit design was completed and Derek handed it over to me as 'job done' back in April (hence the bluebell woods measuring session) I had a Mk1 crossover up and running in a week or two because the drive units integrated so nicely. But - to move from the Mk1 to the final crossover with a smooth response both in the BBC's anechoic chamber and in my (typical) listening room has absorbed me for months. I had to re-educate myself by careful listening exactly what it is about the Monitor 40 concept that makes for that magical sound; its a combination of box size and volume, box width and crossover. As with all quality speakers, there is a very special balance between the technical anechoic characteristics, making it 'sound just right' and, most importantly, making it measure well in-room as you have found. All three have to be in harmony for the illusion to work perfectly.
About stands: no, this really is not as critical as you say. Remember, the professional users are placing the M40 on stands about 36 high, so 22" not an issue. I'll let you know how tall my stands are - of late I've been using the wooden Ikea stands but the top plate is really far too small for safety in your homes. Stand height is directly related to your body height, and should ideally place your ears level with the tweeter whatever that calculates as. The reference axis on the M40.1 is level with (on axis with) the tweeter but +/- 6cms at your listening position will have only a small effect.
Looking forward to the pictures very much. Please email them to the office.
I'll let you know how tall my stands are - of late I've been using the wooden Ikea stands but the top plate is really far too small for safety in your homes.
OK, I checked my stands. Much of the M40.1 development and in-room response measurement/optimisation - and almost all of the listening - was done on 18" stands. I am not saying that they are the best stands or that 18" is a mandatory height but it sounded good to me.
This tread concerns the development of the M40.1 specifically ...
- My listening room during its development
- Test equipment used
- Setting up for the best sound (although this is easy; no special care needed)
- Equipment and cables (all very simple)
- Log book
- Music selection
The key point is that although the M40.1 is a large box it is very user and room friendly.
The entire M40.1 project was undertaken here at 'The Cottage' in the woods from the testing of the new Harbeth-designed bass unit right through the entire crossover development and all the in-room measurements and critical listening tests. The bluebell woods where the outside testing was undertaken (to augment tests in the BBC's anechoic chamber) is to the far right of the picture.
This picture was taken October 2007, just after the pre-production pair was completed and sent to the Rocky Mountain Audio Show in the USA. (You can read reports from the show in this section of the HUG).
In the Harbeth Listening Room. Notice B&K reference microphone. M40.1 on tallish stand at this time not for listening but for measurement to be as far from the floor as possible, and approx. half way between the floor and ceiling.
The M40.1 development Log Book is on the table behind Mr. Harris.
Re: M40.1 - first test run of new Harbeth midrange & woofer
Mounted on the baffle this was the first time that a complete Monitor 40.1 system was brought together. The tests that followed confirmed that the sensitivities and frequency response of both of these two units was exactly as planned and with a worthwhile increase in sensitivity, and an increase in impedance; together that means an easier electrical load on the amplifier. Also note that the ports are longer than the M40 and the system tuned to 35Hz. The rear-cover has been removed from the midrange box so that you can see the RADIAL midrange driver.