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Re: Harbeth and Stereophile

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  • Robert Greene
    I think the problem Alan Shaw mentions is far from confined to the M40.1. It is surely true that rooms affect bass, and the anechoic response will not be
    Message 1 of 34 , Sep 12 5:44 PM
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      I think the problem Alan Shaw mentions is far from confined to the
      M40.1.

      It is surely true that rooms affect bass, and the anechoic response
      will not be exactly what you hear. It is ,however(for speakers that
      are omni in the bass), the one figure that one can use reliably to
      anticipate what the actual bass response in your room will be. If
      you know your room , you can compute from the anechoic response what
      the response at your listening position will be for that speaker in
      a given placement. Indeed, there are computer programs on line that
      will do this for you. Anechoic response is the starting point of
      such computations.

      The problem is that the measurements that Atkinson publishes are are
      described as "Anechoic response"

      The room response measurements are separate.

      Now Atkinson does remark occasionally that his measurements give a
      low frequency rise compared to true anechoic.
      This is clearly true as, for example , you can see by looking at the
      NRC on the PSB Synchrony 1 here
      http://www.soundstagenetwork.com/measurements/speakers/psb_synchrony_
      one/
      and Stereophile/Atkinson here
      http://www.soundstagenetwork.com/measurements/speakers/psb_synchrony_
      one/
      figure 5
      What is called "Anechoic response" in figure 5 simply is not even
      close to agreement to true anechoic in the bass.
      It is something like 7 dB elevated compared to true anechoic
      at 60-70 Hz. The big bass peak shown in Sphile's "anechoic"
      measurement is in reality NOT THERE. (One can rely well on the NRCs
      measurements).

      Another problem, which goes well beyond and in addition to the fact
      that one should probably not call something "Anechoic response" if
      that is not what one is exhibiting, is that the amount by which the
      bass is boosted in Atkinson's measurements does not seem, as far as
      I can tell, to be constant from speaker to speaker. The boost is
      different with different speakers. It is not as if one could simply
      subtract 7 dB at 60-70 Hz and other amounts at other frequencies and
      recover the true anechoic response.

      So even calling the response graph given something like
      "Anechoic with standard bass boost" or something would
      still not give a result that could be consistently interpreted.

      I am quite sympathetic to the problem of bass measurement in
      situations where one has no anechoic chamber available. I deal with
      this all the time as best I can. But I really do think that Alan
      Shaw has a valid objection. No one should labor under the idea that
      the M40.1 has the kind of bass peak that is shown in Atkinson's
      "Anechoic response". Not just Mr. Shaw's remarks but also past
      experience of comparing to NRC true anechoic response measurements
      for other speakers suggests very much that it does not and that this
      large rise is indeed an artifact of the (not true anechoic) response
      measurement method used.


      REG



      --- In regsaudioforum@yahoogroups.com, "Tom Mallin" <tmallin@...>
      wrote:
      >
      > Okay, now I've read Alan Shaw's comments about the M40.1 frequency
      response measurements shown in the Stereophile review. Just picked
      up the mail which was being held at the post office while I was gone.
      >
      > Basically he's saying that the only bass measurements he and we
      can really trust to be accurate are those made in a good anechoic
      chamber like the BBC has and which Shaw uses. Trying to do it in a
      normal room with a mike in the very near field of the woofer gets
      into trouble when you cannot measure the response of individual
      drivers separately (as in the single-wired 40.1, as opposed to the
      tri-wired 40) and where the output of both ports and woofer must be
      taken into account.
      >
      > Two things strike me from what he says. First, Stereophile's
      method of bass measurement should be more accurate with respect to
      acoustic suspension and infinite baffle speakers since there are no
      port outputs to figure in.
      >
      > Second, the last sentence of his comment, while true in one sense,
      is misleading, I think. He says: "What the [anechoic] chamber mike
      records [from one meter away from the speaker] is just what you
      would hear standing there, or in your listening room at home."
      >
      > Well, yes, if you were standing in the anechoic chamber you would
      hear the response measured by the speaker and it would sound like
      how it measures. And the speaker will put out the same amount of
      bass in your listening room as in an anechoic chamber. The bass
      response in your listening room may even sound the way it measures
      in your listening room. But to say that the bass response of the
      speaker will measure in your listening room like it does in an
      anechoic chamber, much less that it will sound in your listening
      room the way it sounds in an anechoic chamber is just wrong.
      >
      > >>> tmallin@... 9/12/2008 12:42 PM >>>
      > The Stereophile measurements of the M40.1 cabinet resonances look
      like the panels resonate over a broad band and at higher levels than
      most other speakers they have tested. At least, that' the way the
      graph looked to me. I have not yet seen Shaw's comments about it,
      if any.
      >
      > >>> laurie483000@... 9/11/2008 4:34 PM >>>
      > They seem to like the HL5 very much. As regards Alan Shaw's
      interview
      > and his explanation of how thin wall cabinets work, this is rather
      > more 'poetic' and a bit different to the old original BBC paper on
      the
      > topic, the dryness of which I find a little more reassuring.
      Reading
      > the HL5 review afterwards made me think that maybe AS's talk had
      been
      > edited a little, as it was noted there that panel flexure is
      damped
      > down sooner in thin walls.
      >
      > But he has previously likened the action to that of musical
      instruments
      > such as a piano sounding board, which surely is about adding
      colour /
      > richness / tone / warmth - fine in musical instruments but not
      really
      > in speakers. However I do agree with his comment about the
      resulting
      > quality of the spacious / concert hall / non hifi quality of the
      bass.
      > My first medium sized Lowther corner horns years ago of all
      speakers!!
      > shared this non boxy quality and it was nice to be somewhat
      reminded of
      > this when I aquired the M30s.
      >
      >
      > Laurie
      >
      >
      > --- In regsaudioforum@yahoogroups.com, "charles452003" <ncrelich@>
      > wrote:
      > >
      > > The July issue of UHF magazine from Canada has an interview with
      Alan
      > > Shaw and a Review of the Harbeth HL5. Part of the HL5 is on the
      cover
      > > behind a Linn Klimax DS. In case its not part of the free on
      line
      > > version, you can get this magazine at Barnes and Noble.
      > > Probably, also at Borders.
      > >
      > > Norm
      > >
      >
      >
      >
      > ------------------------------------
      >
      > Yahoo! Groups Links
      >
    • Ted Rook
      The alternative is the assembly of an anechoic chamber, something that may be unattractive because it would be a significant real estate and capital
      Message 34 of 34 , Sep 20 7:11 PM
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        The alternative is the assembly of an anechoic chamber, something that may be unattractive
        because it would be a significant real estate and capital investment.
        I believe construction equipment is made to handle those weights and an operator safely and
        reliably, think about hoists and cherry-pickers on construction sites and for servicing lighting
        up in ceilings.
        Ted


        On 20 Sep 2008 at 21:17, Will wrote:

        > Good idea but I think not practicle (not to mention dangerous) for many of
        > the speakers tested because they are huge and can weigh a couple hundred
        > pounds.
        >
        >
        > ----- Original Message -----
        > From: "Ted Rook" <rooknrol@...>
        > To: <regsaudioforum@yahoogroups.com>
        > Sent: Saturday, September 20, 2008 6:11 PM
        > Subject: Re: [regsaudioforum] Re: Harbeth and Stereophile
        >
        >
        > > It seems folly to me that Stereophile hasn't managed to accumulate the
        > > resources to do
        > > anechoic speaker measurement. For a few $1000 I can buy a boom-lift or
        > > scissor hoist with
        > > 32 foot height capacity that can carry a speaker face up high into the
        > > air. A measuring mic
        > > has to be arranged a further few feet up and hey presto anechoic response.
        > > The nice dry
        > > atmosphere in New Mexico (isn't that where these folk hang out) provides
        > > lots of dry days to
        > > do tests. I realise there are lots of details to be considered like where
        > > to put the amp, but this
        > > can work and has been done, Alan Shaw has made a feature of his using this
        > > out door
        > > substitute for anechoic rooms, am I missing something here?
        > >
        > > Ted
        > >
        > > On 20 Sep 2008 at 2:41, Robert Greene wrote:
        > >
        > >> Just as a point of clarification, people who are interested in this
        > >> subject of bass in rooms(and I suppose we all are) might like to
        > >> read Atkinson's explanation of why he measures speakers as he does.
        > >>
        > >> The basic drift as of his 1999 article at least, if I may paraphrase
        > >> as impartially as I can, is that, even though he knows that the
        > >> close miked woofer method is going to produce a considerably larger
        > >> amount of measured bass than the anechoic-measured amount, he
        > >> feels that this larger measured amount is representative of what one
        > >> hears in actual roms of domestic size.
        > >>
        > >> There is of course "room gain" in the extreme bottom, as I am sure
        > >> you all know. (We have often talked about the advantage of slow roll
        > >> out of the extreme bottom and you can find a discussion of room gain
        > >> and subwoofers in my discussion of the Audio Physic Minos in TAS.)
        > >>
        > >> But it is odd to my mind to see the big bulges
        > >> up,usually around 60-70 Hz, in his close miked measurements and then
        > >> look at what are often extremely smooth and flat in room RTA bass
        > >> measurements--which, unless the DSP people are all way off bass,
        > >> will actually give a correct amount of bass(for a flat -in- the -
        > >> bass target curve). Room gain in my sense of the word would bring
        > >> up the RTA at the listening position, typically, not just the
        > >> measrement close to the speaker. And in any case, it is the bass
        > >> quantity at the listening position that would seem to me to matter
        > >> most. In short, the speakers that would measure flat for
        > >> his "anechoic" (close miked woofer curves) would apparently be down
        > >> in level in the bass in his room in the sense of the RTA at his
        > >> listening position. In more detail:
        > >>
        > >> Since dB are additive in the obvious sense, to get his close miked
        > >> measurement flat one would typically need to have depressed anechoic
        > >> response at those frequencies--a dip to counteract the bulge that
        > >> arises in the measurement when the speaker is anechoic flat. And in
        > >> turn , this would lead to a dip in the in-room response (RTA) in his
        > >> room--since typically that is quite flat in his room when the
        > >> speaker is anechoic flat.
        > >>
        > >> As far as I am aware, few people feel that speakers with that
        > >> behavior sound anything but quite bass shy.(Room gain is a much
        > >> bigger issue in the true bottom octave, in my experience, unless one
        > >> has a very very small room.)
        > >>
        > >> Anyway, just for your information
        > >> here is a link to his article(the bass discussion begins on page 6)
        > >>
        > >> www.stereophile.com/features/103
        > >>
        > >> REG
        > >>
        > >> --- In regsaudioforum@yahoogroups.com, "Robert Greene"
        > >> <regonaudio@...> wrote:
        > >> >
        > >> > Thanks. I enjoyed this.
        > >> >
        > >> > Actually, I am not so much worried about myself--I shall
        > >> survive,and
        > >> > no doubt your quote does apply. (I always figure that
        > >> > the "celebrities" that claim to be annoyed by the paparazzi are in
        > >> > actuality pleased by being of interest to them).
        > >> >
        > >> > But I am concerned about the psychological health of the audio
        > >> > industry when personalities have become seemingly of more
        > >> interest
        > >> > than the technical facts. In particular, some consumers seem to be
        > >> > treating the field not as a source of sound but a source of gossip!
        > >> >
        > >> > I think more people may be reading about details of the people
        > >> > involved than going to the Stereophile and Soundstage website
        > >> > say figure 5 of
        > >> > www.stereophile.com/floorloudspeakers/408psb/index4.html
        > >> > versus the first {true anechoic] graph at
        > >> > www.soundstagenetwork.com/measurements/speakers/psb_synchrony_one/
        > >> >
        > >> > actually to see what the comparison between the two types of
        > >> > measurements is, Sphile's versus true anechoic.
        > >> >
        > >> > REG
        > >> >
        > >> >
        > >> >
        > >> > --- In regsaudioforum@yahoogroups.com, "laurie483000"
        > >> > <laurie483000@> wrote:
        > >> > >
        > >> > > If any comfort is needed, here in London, someone a long time
        > >> ago
        > >> > > (Oscar Wilde quite likely) put it another way. "The one thing
        > >> > worse
        > >> > > than being talked about is, NOT being talked about."
        > >> > >
        > >> > >
        > >> > > Laurie
        > >> > >
        > >> > >
        > >> > > --- In regsaudioforum@yahoogroups.com, "Robert Greene"
        > >> > <regonaudio@>
        > >> > > wrote:
        > >> > > >
        > >> > > > Thanks for the support. It is strange perhaps how
        > >> personalities
        > >> > > > are more important to so many people than matters of
        > >> > fact........
        > >> > >
        > >> > > .... In Hollywood, they still say that there is no such thing as
        > >> > bad
        > >> > > > publicity. I am assuming this is true!
        > >> > > >
        > >> > > > REG
        > >> > >
        > >> >
        > >>
        > >>
        > >>
        > >> ------------------------------------
        > >>
        > >> Yahoo! Groups Links
        > >>
        > >>
        > >>
        > >>
        > >>
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        > > ------------------------------------
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