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Harbeth Monitor 40.1 specific

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  • Re: Rate your own room ...

    So, Jeff, ignoring the test gear and using your own judgement, I'm still looking for a numerical score from you! Just curious.
    Alan A. Shaw
    Designer, owner
    Harbeth Audio UK

    Comment


    • Re: Rate your own room ...

      Originally posted by A.S. View Post
      So, Jeff, ignoring the test gear and using your own judgement, I'm still looking for a numerical score from you! Just curious.
      Hmmm ... subjectively I would put it at about a 5 I suppose using your analogy, Alan.

      Best,

      Jeff

      Comment


      • Re: Harbeth Monitor 40.1 specific

        Jeff,
        I apologize in advance if I've missed this, but have you taken frequency response measurements of your system? That would show you where, frequency-wise, where the bass problems are.

        Another thing to consider is some sort of room correction. I have the M40.1's in a room much smaller than yours (11' x 17' with 8' ceilings) and use a Behringer DEQ2496 betweeen my transport and DAC, so it's only used in the digital domain. I find it very useful in minimizing midbass boom in my room. I use the Behringer ECM8000 mike with it, which isn't perfect, but is good enough for bass measurements.

        You may be wondering, "didn't Alan design the 40.1's to work in rooms without having to use EQ?" Just to put things in perspective, the EQ is needed for my M30's in this room as well, so some rooms are just problematic.

        Regarding the Acoustic Revive panels, are they desinged to ameliorate bass problems? From reading their description, I did not see much talk about the bass region. You may want to consider trying dedicated bass traps. I have two pairs of the Cathedral Sound panels in each upper corner. I can't honestly say they made a huge difference. My before/after measurements did not yield much difference, but it did sound to me that the lower midbass was cleaner and had more "punch."

        Keep us posted... It would be a shame if you felt you had to part with the M40.1's - they are fantastic speakers!

        In my room, I had to do more experimenting with placement of the M40.1's than I was expecting, but am now at a stage where I'm really enjoying them. I think with a bit more experimenting, you can arrive at that happy place, too,

        Eric

        Comment


        • Re: Rate your own room ...

          Umm. I'm not so sure about that. I think that half way between a cave and an anechoic chamber with a score of about 5 would be a well designed, sweet sounding concert hall. Such a room would have an excellently well controlled decay across the entire band, no 'hot' frequencies which seem to hang-on after the note and would never draw attention to itself.
          So, I think we have to be realistic and say that the beautiful room you listen-in must be somewhat less damped than a '5' rating would honestly justify. Almost all domestic rooms have far, far less absorption than ideal for listening to hi-fi minus the room's overarching contribution. And that really is the nub of the problem. There are three ways forward ....

          1. Increase the damping and hence absorption in the room, perhaps significantly and accept that the acoustic treatment is going to impact on the cosmetics - which just may not be acceptable and/or

          2. Change or somehow modify the speakers themselves to pump less bass into the room and/or

          3. Introduce some electronic adjustment in the signal path (of the amp) to reduce the amount of drive to the speakers in regions where the room's absorption is lower than ideal.
          Alan A. Shaw
          Designer, owner
          Harbeth Audio UK

          Comment


          • Re: Rate your own room ...

            Originally posted by A.S. View Post
            Umm. I'm not so sure about that. I think that half way between a cave and an anechoic chamber with a score of about 5 would be a well designed, sweet sounding concert hall. Such a room would have an excellently well controlled decay across the entire band, no 'hot' frequencies which seem to hang-on after the note and would never draw attention to itself.
            So, I think we have to be realistic and say that the beautiful room you listen-in must be somewhat less damped than a '5' rating would honestly justify. Almost all domestic rooms have far, far less absorption than ideal for listening to hi-fi minus the room's overarching contribution. And that really is the nub of the problem. There are three ways forward ....

            1. Increase the damping and hence absorption in the room, perhaps significantly and accept that the acoustic treatment is going to impact on the cosmetics - which just may not be acceptable and/or

            2. Change or somehow modify the speakers themselves to pump less bass into the room and/or

            3. Introduce some electronic adjustment in the signal path (of the amp) to reduce the amount of drive to the speakers in regions where the room's absorption is lower than ideal.
            That's why I don't like talking in subjective terms when talking about rooms, Alan, as it really doesn't tell you anything meaningful - it's better to use measurements. For example, as I'm sure you know due to your BBC experience, the optimum reverb time for music is considered by most people to range from 0.2 seconds to 2.6 seconds depending on the venue. 0.2 to 1.2 seconds is considered by most to be a 'dead space' and 1.2 to 2.6 seconds is considered to be a 'live space'.

            A typical studio measures from 0.2 to 0.6 seconds, a good venue for classical music measures 1.2 to 1.6 seconds, a good venue for chamber measures from 1.4 to 1.8 seconds, and so forth. My room measures with a reverb time of about 0.35 seconds from 32Hz to 16K Hz, which means it is a 'dead space' by measurement, and falls in the range typical of studios. So even though you are assuming that it is a live space by looking at the photos, the measurements don't really support that conclusion.

            What is unusual is that the M40.1 is the only speaker out of the many I've had through here that exhibits exaggerated bass response in the room, so it leaves me a bit puzzled. I'm not saying I don't like the M40.1, Alan, I like it very much, except for the somewhat elevated bass response I'm getting.

            I think you are correct though, Alan, the M40.1 may very well need equalization to achieve the best performance in domestic environments. As far as suggestion 1 goes, I think the room measurements show that is not the issue. However, I am interested to hear your thoughts on suggestion 2, and while it is easy to do 3 for digital, to do analog EQ for the whole system doesn't seem practical, and really it shouldn't be necessary to have to resort to that.

            Kind regards,

            Jeff

            Comment


            • Room reverb

              In my room, getting the M40s on taller (24") stands helps the bass response significantly (and I think others have found this with the M40s). I know Alan made adjustments to the M40.1s that allow for lower stands, but it might be worth a try to get them about 24" off the floor just to see if the difference in bass response is more to your liking.

              Comment


              • Room reverb

                Hi Jeff,

                Did you use the reverb calculator as featured in the link below to calculate the reverb time of your room?

                http://www.csgnetwork.com/acousticreverbdelaycalc.html

                It is interesting to note that your room measures as a "dead" space with a reverb time of 0.35s. From the pictures of your room it doesn't really look too dead. The reverb time you've got in your listening space is even lower than that of a typical studio if the figures are averaged out. I suspect the carpet floor has got a lot to do with the excessive absorption, more so if you've got thick padding underneath. Also, the material of your walls, presumably drywall constructed from sheetrock is slightly (maybe considerably) more absorbent than concrete or masonry walls. I agree that it is more useful to carry out measurements to give a more meaningful interpretation of the acoustical conditions of the room.

                May I know the source that has been referred to in the description of room acoustical conditions(dead/live/studio/chamber etc.) based on reverb time?

                Since you have gone to the extent of measuring the reverb time of your room, I suspect you must have done some measurement on the frequency response of your speakers using an RS meter and some test tones? After plotting out the graphs you would have a better idea how the variations in tones would look like. Subsequently you can fine-tune the position of the speakers to achieve the smoothest bass response. Anyway since you mentioned you already followed the setup guidelines of Jim Smith and spent a lot of time moving the speakers around, guess that wouldn't help much.

                Eric may have a point in the Acoustic Revive panels of not being effective in addressing bass problems. They may not be designed for the purpose as the thickness of the panels will have insignificant impact in trapping bass frequencies. Proper bass traps will reduce bass energy by decreasing the null and bringing down peaks at the same time. It may be worth a try apart from recommendations of a taller speaker stand since various speaker positioning have not worked out for you.

                Comment


                • Room reverb

                  Hi Ryder,

                  I didn't use a web based calculator, but rather an RT60 anyalyzer and measured reverb decay time for each octave band, 31Hz - 16kHz, by pulsing pink noise on and off through the M40.1s, filtering the incoming signal by octave band, and measuring the timing of the decay of each octave band. My room doesn't look very dead, but it measures quite dead. I actually wouldn't mind if it were a little more live, say in the 1.4 second range.

                  There's quite a lot of information about optimum reverberation times out on the web for different sorts of venues, just try searching on 'optimum reverberation times' on Google and lots of useful links will come up.

                  There's some nice examples at http://www.acousticalsolutions.com/sounds.asp . I've attached a handy reference chart from the same site that shows ranges for optimum reverb times for various music venues.

                  Best,

                  Jeff
                  Attached Files

                  Comment


                  • Room reverb

                    Thanks for the response Jeff. Is the reverb time of 0.35s an average or a consistent figure across the entire frequency band? If you wouldn't mind, can you try out the web-based calculator in the link to determine whether the results you have obtained with your RT60 analyzer are consistent with the one provided on the web? I am curious to know as I find the values of the reverberation time to differ greatly across the frequency spectrum. Thanks in advance.

                    Comment


                    • Re: Harbeth Monitor 40.1 specific

                      On a separate note, I have noticed that the speaker stands are not spiked to the floor. Have you tried spiking the Skylan stands to the floor? Or the stands are designed to be placed flat on the floor without spikes?

                      Comment


                      • Re: Rate your own room ...

                        Originally posted by A.S. View Post
                        Umm. I'm not so sure about that. I think that half way between a cave and an anechoic chamber with a score of about 5 would be a well designed, sweet sounding concert hall. Such a room would have an excellently well controlled decay across the entire band, no 'hot' frequencies which seem to hang-on after the note and would never draw attention to itself.
                        So, I think we have to be realistic and say that the beautiful room you listen-in must be somewhat less damped than a '5' rating would honestly justify. Almost all domestic rooms have far, far less absorption than ideal for listening to hi-fi minus the room's overarching contribution. And that really is the nub of the problem. There are three ways forward ....

                        1. Increase the damping and hence absorption in the room, perhaps significantly and accept that the acoustic treatment is going to impact on the cosmetics - which just may not be acceptable and/or

                        2. Change or somehow modify the speakers themselves to pump less bass into the room and/or

                        3. Introduce some electronic adjustment in the signal path (of the amp) to reduce the amount of drive to the speakers in regions where the room's absorption is lower than ideal.
                        Alan, you've inspired me to play around a bit more.

                        I used my real time analyzer with pink noise to evaluate what was happening from 22Hz to 21.6KHz and found a peak around 51Hz with things somewhat elevated starting about 200Hz and down to 36Hz

                        Using a Mac with Amarra software (replaces the sonic software engine of iTunes, made by the studio folks Sonic Solutions) I was able to EQ it out with the Amarra equalizer (the same thing can be done with the iTunes equalizer, but it's not as sophisticated, but priced right). That makes it nice when playing Redbook files stored in my iTunes music library on my Mac through iTunes to a USB DAC.

                        Now if it only worked in the analog domain that easily. It's almost enough to make me go all digital. Almost. ;-)

                        Thanks for your suggestions.

                        Best,

                        Jeff

                        Comment


                        • Room tuning

                          Originally posted by Jeff Day View Post
                          ...but rather an RT60 anyalyzer and measured reverb decay time for each octave band, 31Hz - 16kHz, by pulsing pink noise on and off through the M40.1s, filtering the incoming signal by octave band...
                          I'm glad to see some useful feedback on this overnight. I too have done some research, which is in general agreement with others contributions. My knowledge of acoustics is negligible, but using a little common sense and practical experience maybe I can contribute something.

                          First, about your measurement method. I'm not sure who advised you, but the standard way for measuring room acoustics is to use one-third octave analysis across the audio band, not full octave. Obviously, 1/3 octave would give you three times the resolution and give you a much more interesting understanding of 'hot frequencies' in the room which could be buried in the crude full-octave averaged measurement. So, I strongly recommend that in future, at least 1/3 octave, or better is used for analysis if your equipment is capable of resolving that detail. When I am designing speakers, and I've got to the point where the basic 'anechoic' response is as I want it, I then switch between 1/12th, 1/6th and 1/3 octave displays measuring in my listening room to see how the room screws up my nice flat response. Full-octave display just wouldn't tell me anything useful.

                          Second - and this has been touched on by others - having read late last night the BBC's internal papers about studio construction and measurement, I concur with other comments that even with the walls loaded-up with thick, properly designed absorber panels protruding a foot into the studio control room, the BBC could not achieve the 0.3s revereb specification you claim in your normal, untreated domestic room down to those low frequencies. Something is wrong: either your measurement system is deceiving you, and somewhat underestimating the LF reverb (full ocatve resolution?) or your listening room by some good luck is miraculously absorptive at low frequencies. That just might be so, but is it likely?

                          Once again, we can find much useful information in the BBC archives if you know where to look and have a vaguely photographic memory! Back at the BBC in the 70s, they were becoming aware that the acoustic specification they'd set for the whole corporation was not really achievable for tight-budget divisions, such as the then new BBC local radio. So, the question was asked, by how much can the reverberation spec be relaxed especially in the low frequencies without (too much) or even noticeable degradation of perceived quality in the low frequencies. The middle and upper frequencies had to still meet the approved specification, and could be made to do so with relatively inexpensive (i.e. thin, stick-on) surface treatment. The problem was that bass treatment costs money, is heavy and shrinks rooms.

                          Attached is data from the BBC report which describes an experimental studio, fully lined with 1 foot thick, floor to ceiling bass absorbers (see radio studio picture) covering much of the surface, and the same studio with the absorbers removed. As you can see, the bass reverberation time increased from an astonishingly good 0.4-0.5s (approx.) to about 1.2 secs. without the absorbers - just what I'd expect. The BBC went about the evaluation by using real voices in the room, recorded them and played them back outside to see how changes in the room's treatment influenced perceived quality. Note - I suspect that one voice (highlighted comment) was Derek Hughes' father.

                          The conclusion of all this was Fig. 3 a 'recommended maximum permissible bass rise for a talks studio'. Above all, please note that (on a third-octave basis) the reverb-frequency curve is smooth, no 'hot' lingering frequencies, and that a doubling or so is acceptable at the very lowest frequencies. How this translates to music listening I cannot say but this is a good working rule. Personally, I don't believe that bass can be usefully absorbed unless a) the walls are significantly covered to a depth of about 3 feet (1m) in something absorbent or b) are covered in bass-traps (see picture) to a depth of a foot or so. Speaker cones, spikes, cables etc. etc. cannot absorb bass or they would be defeating known physics and they would have been used by the BBC in lieu of millions of pounds of old-fashioned, physical, room treatment.

                          Full BBC report here

                          >
                          Attached Files
                          Alan A. Shaw
                          Designer, owner
                          Harbeth Audio UK

                          Comment


                          • Re: Harbeth Monitor 40.1 specific

                            I'm still waiting for my 40.1's to arrive but from experience with the 7's and 5's I would suggest you take a look at some lightweight open frame type stands.

                            I use the Something Solid stands which are tailor made for the speaker and your requirements, so I have ordered different heights for each of my demo Harbeths.. The ideal (for me) being with the main tweeter at my ear level when seated.

                            The open frames in comparison to the heavier, solid constructions are much cleaner, airier and more nimble. The heavier stands invariably sounding the way they look - fat and heavy.

                            It's worth trying.

                            Comment


                            • Re: Room tuning

                              Alan,

                              I did the RTA analysis using 1/3 octaves and it does show rising frequencies in the room below about 200 Hz - I believe I said that in one of my messages, but maybe I left it out. It's just the RT60 measurement that uses octaves and then averages to get room's reverb. You'll see the reason for this below in a moment, but in general RT60 is useful from 200Hz up to get average room reverb measurements (the majority of musical information falls within this region), and RTA analysis is most helpful for characterizing the region below 300 Hz to analyze what?s going on in the bass (and where most issues for loudspeaker setup occur).

                              Now let's talk about the BBC article you attached for a moment: the purpose of the article is to describe how rising low frequencies in rooms degrade speech intelligibility, it?s not about music, and it?s not about how low frequency performance of a loudspeaker is affected by room acoustics - an important point, and one which could mislead you if you weren?t reading carefully and thinking about the implications. In fact, you might note that the article states in the first paragraph of section 6.2 that their studies with voice intelligibility ?cannot have practical significance? for ?bassy? loudspeakers, which is of course what the M40.1s are.

                              The article does make a few points that are relevant to our discussion however: The article says reverb time (RT60) in rooms works ok 200Hz and above (first paragraph), but isn't useful below that (which means it works fine for most musical content except the bass region below 200Hz). So while my room may measure in the 350 ms range as an average, that doesn?t have a lot to do what?s going on in the bass, which is the point I?m trying to get across. So I think you may be confusing what kind of useful information RT60 provides and what it means, compared to what information RTA provides and what it means, which is getting us off track with addressing my immediate problem of sorting out the bass issues of the M40.1 in my room.

                              I am astonished by your comment: ?Personally, I don't believe that bass can be usefully absorbed unless a) the walls are significantly covered to a depth of about 3 feet (1m) in something absorbent or b) are covered in bass-traps (see picture) to a depth of a foot or so.? Surely you don?t expect your customers (I?m one of those, not the enemy, in case you forgot) to cover their walls with 3 feet of sound absorbing material in order to make your speakers work in the bass? No offense intended, but surely that?s ridiculous.

                              Here?s the deal: I have had lots of speakers in this room, as well as my own SHL5s and M40.1s. Some of my speakers, like the Avantgarde Duos, go deeper in the bass than the M40.1, and none of them have had issues with the bass in the room that require heroic measures like the M40.1 apparently does to resolve. If you?ll notice a fair number of the other posts talked about how they have difficulties with the bass on their Harbeth M40.1s too, and the Stereophile review of the M40.1 also pointed that both Dudley and Atkinson had trouble with bass performance in their rooms as well.

                              So what you?re not picking up on is that for most people the M40.1s have trouble with the bass in most rooms, and many of those people are experienced in audio, as I am, and while you seem to always want to blame people?s rooms or their measurement techniques for the issues, you are sidestepping the actual issue of bass problems with the M40.1. Many of these people, like me, are your customers, and you do us a disservice by cavalierly dismissing the issues we are having with our M40.1s in most rooms. You need to ask yourself what it is about the M40.1 that is causing so many of your customers to have problems that they don?t have with other speakers.

                              Frankly, as a customer, that attitude, and the apparent need to have to go to heroic measures to solve bass problems in the M40.1, pisses me off. As a responsible manufacturer you need to offer your customers a fix for the M40.1 that resolves the overblown bass issue, and get out of the denial stage that it exists ? that would be a responsible way to treat customers who have put enough faith in you to buy your products.

                              Best,

                              Jeff

                              Comment


                              • Re: Room tuning

                                It seems obvious to me that there really is no substitute for taming low frequencies in a room* than to use some mechanical method - such as bass traps of one design or another - or driving the speaker electrically with less bass to counterbalance the room's lift at those low frequencies. The essence of the BBC article was to indicate that, as you say, a broad and relatively dry room in the middle frequencies does not necessarily imply much absorption at low frequencies. The (skimpy) acoustic treatment that works well in the middle frequencies is actually useless at treating significantly lower frequencies. Furthermore, they showed that a room can be more lively (undamped) in the bass and yet still sound acceptable. As all listening rooms destroy the bass quality to one degree or another, humans are very forgiving of that and tend to hear through the lumps and bumps in the bass. Just as well or the hi-fi experience would be impossible!.

                                I have no intention to 'blame you' (your words) and I have been considering constructive ways of helping you. The facts are these: I have no issues with the bass in my listening room so I cannot synthesise your issue. But as I showed here I have large rockwool batts behind my speakers because I want the room to be as neutral as possible.**

                                There are no issues with the bass in properly designed BBC control rooms where the low frequency absorption is controlled and adequate. The M40.1 is a large box, with lots of bass potential and works at its best in an environment sympathetic to the low-end characteristics. That means, inevitably, that to get the very best sound at home, the room needs to be as absorptive as possible in the bass or as some have found, external signal EQ can be applied very effectively if needed. That's how it's always been with these big BBC boxes.

                                *You misunderstood my intention. I was making a general point about bass absorption - I did not direct that comment to any particular make or model of speaker - I was commenting on bass in rooms, not speakers in rooms.

                                ** It took me ages to track-down a bass issue. I noticed one day when accidentally slamming shutting a kitchen cupboard door in the adjacent kitchen, the characteristic 'boom' of a bass note. It transpired that the volume of air in every cupboard and the compliance of their doors created a row of efficient resonators at one particular bass note. For super-critical listening, you have to remember to open the cupboards a little. You certainly can't blame loudspeakers for that coincidence.
                                Alan A. Shaw
                                Designer, owner
                                Harbeth Audio UK

                                Comment

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