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Re: [regsaudioforum] To eq or not to eq? More tests (M30s)

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  • george day
    Tom, We measure differently. You use a certainly volume level to establish a reference at a certain point. Like most professional measurement programs, or
    Message 1 of 106 , Oct 1, 2006
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      Re: [regsaudioforum] To eq or not to eq?  More tests (M30s) Tom,

      We measure differently.  You use a certainly volume level to establish a reference at a certain point.  Like most professional measurement programs, or what you refer to as “fancy,” this is using a sine wave. Volume doesn’t matter much.

      Anyway, I think you got it backwards.  First of all, I had the same behavior with my M40s.  Second, one speaker is against a full wall and the other near a half-wall and then open space — they will behave differently.  Third, the point is that the area about 1khz or so represents the linearity of the speaker. The shelf ABOVE it has to do with the fact that the highs are well absorbed whilst the lows continue bouncing around, room modes, etc.  Not surprising, and I’m not the only one who has had results like this.

      PS, it took seconds to get both measurements.  Personally, I’d rather do that and then listen to music rather than spend an evening with a CD and SPL meter.  No offense, but give me a break.


      On 10/1/06 6:15 PM, "Tom Mallin" <tmallin@...> wrote:

      I don't think room furnishing is the reason for the shelf-down in the highs, George.  Assuming you are measuring on-axis response from not too far away, room absorption shouldn't create a sudden shelf like that.  You might get that kind of shelf if you were averaging a number of positions on and off axis, but I still doubt it.  Such curves usually show a gradual roll off, not a shelf like yours.
       
      The M40s certainly don't show a huge dip in my room between 1 and 2 kHz, even with all my foam, and even when measured from 80" or more back from them.
       
      I'm sure it's a measurement anomaly of some sort.  Since both speakers show this, it's probably not a speaker crossover problem.  Just goes to show you that fancy measuring equipment is not foolproof.
       
      Incidentally, your measurements obviously were not using 1 kHz as a reference frequency, as they should.  If they were, your left and right channel would have measured the same at that frequency.  You should also measure at an output of at least 80 dB at 1 kHz.  Any lower will tend not to give you an accurate picture of room mode activation of the bass, assuming you listen to music at 80 dB or above on peaks.


      >>> george@... 10/01/06 07:09PM >>>
      Sure.

      A friend of mine pointed out, with great insight, that the bump I measure at 1khz is probably due to the fact that I have a larger, carpeted room and that is is filled with large, cushy furniture.  In short, the high frequencies — which appear linear — are quickly absorbed while the low frequencies continue to bounce around.

      This leads to the question of room treatments or EQ.  My wife will shoot me if I try any room treatments.  Anything. So, I guess the answer is EQ, and that means pulling down the 5db “shelf.”  What do you think?

      This will be more interesting in Europe. Our house there is not carpeted, the walls are plaster and stone, etc.


      On 10/1/06 4:48 PM, "Rod Hill" <rodhill3@...> wrote:


       
       

      Noted, with thanks,  George.

      ROD
      Sydney Australia

      --- george day  <george@... <mailto:george%40highdudgeon.net>  > wrote:

      > Rob,
      >
      > The Firebox sells for $299, US.   That seems like a
      > lot.  Itâ•˙s got all sorts
      > of  software...but I donâ•˙t use it. The Mac
      > recognizes it, via Firewire,  and
      > thatâ•˙s all I need.
      >
      >
      > On 10/1/06 12:27  AM, "Rod Hill"
      > <rodhill3@... <mailto:rodhill3%40yahoo.com.au>  > wrote:
      >
      > >  
      > >  
      > >   
      > >
      > > George: Is the following (please see extract  from
      > web
      > > page below)the same unit you recommended in  your
      > email
      > > to Charlie?
      > > If so, do you know  anything about the software
      > they
      > > mention in the last  paragraph of the extract?
      > >
      > > EXTRACT:
      > >  Presonus FireBox
      > > 6x10 24-bit/96K FireWire Recording  System
      > > $ 699 RRP  
      > >  
      > > Jump to  Computer Equipment
      > >  
      > > Extend your warranty to 5  years on this product
      > for
      > > just $69.90!  
      >  >  
      > >  
      > > The FIREBOX is the most powerful  24-bit/96k
      > FireWire
      > > recording interface that fits in the  palm of your
      > > hand. The FIREBOX is a complete 24-Bit/96k
      >  personal
      > > recording studio combining two high quality
      >  PreSonus
      > > microphone/instrument preamplifiers, 24-Bit/96k
      >  sample
      > > rate and Steinberg's Cubase LE 48-track recording
      >  > software. The FIREBOX is the perfect hardware and
      > > software  combination for a powerful
      > > professional-quality and compact  computer-based
      > > studio.  
      > >  
      > >  Hardware  
      > >  
      > > The FIREBOX has the highest  record/playback track
      > > count of its size with the ability to  record six
      > > inputs and playback through ten outputs
      >  simultaneously
      > > all at pro-quality 24-bit/96kHz. Two  ultra-low
      > noise
      > > high-headroom microphone/instrument  preamplifiers
      > with
      > > 48V phantom power are on the front  panel for
      > quickly
      > > and easily connecting your favorite  microphones
      > and
      > > instruments. The FIREBOX also includes a  high
      > quality
      > > stereo headphone output with volume  adjustment on
      > the
      > > front panel. The headphone output has  its own
      > > two-channel driver stream which can be used as a
      >  > separate stereo bus or two-channel output giving
      > you
      > >  the ability to send a ╲cue╡ mix to the
      > headphone
      > >  output and a main mix to the main output. Two
      > > additional balanced  TRS line inputs are located on
      > the
      > > rear of the FIREBOX  along with six balanced TRS
      > line
      > > outputs. Two channels of  S/PDIF input/output and
      > MIDI
      > > input/output are also  included via DB9 breakout
      > cable.
      > > A software router/mixer  is also included for
      > further
      > > flexibility and power. The  1/3U-wide metal chassis
      > of
      > > the FIREBOX is designed to fit  the MAXRACK
      > > rack-mounting system from PreSonus and can be
      >  racked
      > > with the TubePRE, COMP16, EQ3B and HP4 for a neat
      >  and
      > > compact computer recording system.
      > >   
      > > The FIREBOX works with both four and six-pin
      >  FireWire
      > > (IEEE 1394) connectors and can be powered by
      >  either
      > > 6-pin FireWire bus power, or powered by an
      >  external
      > > power transformer.
      > >  
      > > The  Windows XP and Macintosh compatible FIREBOX
      > comes
      > >  ready-to-record with Steinberg's Cubase LE
      > 48-track
      > >  24-bit/96K recording software, and is also
      > compatible
      > >  with many popular ASIO/WDM and Core Audio based
      > > applications  including Logic, Sonar, Audition,
      > Digital
      > > Performer and  others.
      > >
      > > ROD
      > > Sydney Australia
      >  >  
      > >  
      > >
      > > --- george day  <george@... <mailto:george%40highdudgeon.net>  
      > <mailto:george%40highdudgeon.net>  >
      > > wrote:
      > >
      > >> > I realized the  error of my ways.  I replaced
      > the
      > >> > gear.   Actually, and
      > >> > conveniently, Guitar Center had a  returned
      > Firebox,
      > >> > so I bought it for  just
      > >> > about the price of the old one.  I bought  a
      > less
      > >> > expensive mic, but it
      > >>  > performs almost the same, so IÂ’d really lose
      > out
      >  >> > there.  Invest was $250.  I
      > >> >  already have cables, etc., so  what the heck?
      > And,
      >  >> > they even have  a 30
      > >> > day, no  questions asked policy!
      > >> >
      > >> > HereÂ’s  what I use:
      > >> >
      > >> > 1. Presonus Firebox  audio device.  The  thing
      > is
      > >> > idiot  proof. You connect it
      > >> > to your computer via Firewire.   You punch in
      > the
      > >> > phantom power button.   You
      > >> > click in the mic cable, run it to the mic  at
      > the
      > >> > listening position, and
      > >>  > have at it.
      > >> > 2. Mic: I picked up a Behringer  ECM-8000.
      > IÂ’ve had
      > >> > one before and IÂ’ve  had
      > >> > a DBX RTA, which was supposed to be superior
      >  (and
      > >> > which costs twice as
      > >> > much).   In my experience, they are the same,
      > and
      > >> >  people I know recommend the
      > >> > Behringer.  It  undulates by half a db or so
      > here or
      > >> > there â•’  not an issue for
      > >> > our purposes.
      > >> > 3.  Software: Fuzzmeasure, for the mac.  For the
      > PC,
      > >>  > you can use something
      > >> > like TrueRTA (IÂ’m not  entirely sure how it
      > works,
      > >> > but I imagine the  basic
      > >> > setup is the same).  If youÂ’re feeling  game,
      > get
      > >> > Liberty Audio Suites.
      > >>  > $1,200 or so, and it comes with a calibrated
      > mic.
      >  >> > Might be more than
      > >> > $1,200, actually.   Anyway, it does RTA and FFT,
      > >> > Robert uses it,  etc.
      > >> >
      > >> > IÂ’d be glad to field more  questions!
      > >> >
      > >> >
      > >> >  On 9/30/06 6:16 PM, "Charlie Daniell"
      > >> >  <danvetc@... <mailto:danvetc%40bellsouth.net>  
      > <mailto:danvetc%40bellsouth.net>  > wrote:
      > >> >
      > >>> > >   
      > >>> > >  
      > >>> > >   
      > >>> > >
      > >>> > >  George,
      > >>> > >  
      > >>> > > I  thought you sold your measuring gear. What
      > will
      > >> >  you use this time? (I need
      > >>> > > to get something  myself.)
      > >>> > >  
      > >>> > >  Charlie Daniell
      > >>> > >  
      >
      === message  truncated ===


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    • thomas_pfenning
      I guess I am in the category of highly reverberant then. I used eq to dramatically reduce my bass output but the result sounded very slow and mushy. I still
      Message 106 of 106 , Oct 3, 2006
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        I guess I am in the category of highly reverberant then. I used eq to
        dramatically reduce my bass output but the result sounded very slow
        and mushy. I still had quite a slope from the lower to the higher
        frequencies.

        Now with the absorbers the bass sounds much more on time and precise
        and I am still reducing the bass. I take the better sound over the
        additional heat any day ...

        When I find the time I will do a complete recalibration and let you
        know the before and after.

        Cheers

        Thomas

        --- In regsaudioforum@yahoogroups.com, "regtas43" <regonaudio@...>
        wrote:
        >
        > This is absolutely correct and is one of the advantages of close to
        > corner(or in corner) woofer placement,etc.
        > However, a hugely reverberant space cannot really be tamed by EQ in
        > practice. (In principle the room/speaker combo as a filter can
        > always be "inverted" at one point, but in practice this is not
        going
        > to work well in a highly reverberant room.)
        >
        > REG
        >
        > --- In regsaudioforum@yahoogroups.com, "Tom Mallin" <tmallin@>
        > wrote:
        > >
        > > One thing to keep in mind in choosing bass absorber v. bass EQ:
        > > Absorbed bass is turned into ambient room heat and has no benefit
        > for
        > > your system. Equalized bass has benefits for your system, at
        > least if
        > > all you are doing is pulling down peaks.
        > >
        > > In contrast, any electronic equalization minimizes the amp power
        > and
        > > driver excursion necessary to reach any defined flat-frequency-
        > response
        > > SPL. Your amp and drivers will "loaf," relatively speaking,
        > reducing
        > > distortion and increasing dynamic headroom for both speaker and
        > amp.
        > > The more bass you "subtract" with electronic equalization, the
        > greater
        > > these positive effects. M40s will play quite loudly and cleanly
        > indeed
        > > in my room after I pull out the excess midbass I get in my room
        > pre-EQ.
        > >
        > > >>> thomas_pfenning@ 10/02/06 08:59PM >>>
        > > Thanks for the response. That is more than you shared last time:-)
        > >
        > > I did measurements similar to this in my last iteration but I did
        > not
        > > like the sound to much. My M40s are 30" from the back wall and
        the
        > > result of the eq was lowering of the low frequencies.
        > >
        > > The reverberation time in my room is much longer towards the
        lower
        > > frequencies and I guess the sum of the direct arrival and the
        > > reverberant field does result in a significant higher amount of
        > bass
        > > in the frequency response.
        > >
        > > I recently added some 6" panels between the wall and the M40s as
        > well
        > > as one in front of an open fireplace which was creating one weird
        > > resonance. This is in additon to 14" Supertraps in the corners.
        > >
        > > The sound is dramatically changed to the better with much less
        > > equalization. The bass sounds much faster and clean vs. boomy
        > before
        > > and the room response flattened out.
        > >
        > > After this experience I am not so sure anymore that steady state
        > bass
        > > measurements are very useful. Somehow it would be good to find
        out
        > > how much of the response comes from direct arrival vs.
        reverberant
        > > field especially in the bass and get a feel for when to put in
        > > absobers vs. equalizing.
        > >
        > > What do you think?
        > >
        > > Cheers
        > >
        > > Thomas
        > >
        > > --- In regsaudioforum@yahoogroups.com, "regtas43" <regonaudio@>
        > > wrote:
        > > >
        > > > This is a somewhat tricky issue. If one knew a definitive
        > answer,
        > > > then one could design one's own room correction system and it
        > would
        > > > be perfect, or as nearly perfect as such a system can be.
        > > >
        > > > However, roughly speaking I think that one can get a good idea
        > by
        > > > starting from the viewpoint that as the windowed response
        > > > stabilizes, it should stabilize to flat. This amounts to
        > > > having a time window on the order of the period( one over the
        > > > frequency) for various frequencies.
        > > >
        > > > There is a trade-off here in resolution of frequencies versus
        > > > windows. This is why it is probably a good idea to correct the
        > > > speaker in the high frequencies anechoically (direct arrival
        > with a
        > > > long window) ,which is what the Essex unit did. You can get
        > pretty
        > > > close to this by making the speaker flat in the igher
        > freuqnencies
        > > > for a measurement quite close to it.
        > > >
        > > > Then in the bass you just do steady state and in the
        > midrange ,in
        > > > between--ummm, that is trickier, but some sort of cross between
        > > > direct (anechoic) response and steady state, involving say the
        > > > direct plus the floor bounce(and ceiling if it si early).
        > > >
        > > > This works pertty well in my experience.
        > > >
        > > > I think UB does an almost complete inversion of the room plus
        > > > speaker as a filter, but this is not really doable by hand. (He
        > > also
        > > > does some phase correction, ie not pure minimum phase EQ).
        > > > He can explain more.
        > > >
        > > > But for hand done EQ the above seems to work out nicely.
        > > >
        > > > Do not hesitate to use your ears!!!
        > > >
        > > > REG
        > > >
        > > >
        > > > --- In regsaudioforum@yahoogroups.com, "thomas_pfenning"
        > > > <thomas_pfenning@> wrote:
        > > > >
        > > > >
        > > > > > A next point is the important direct arrival. The best
        > method
        > > is
        > > > to
        > > > > apply
        > > > > > frequency dependant windowing to the pulse response
        > resulting
        > > > from the
        > > > > > logsweep measurement. As the windows concentrate around the
        > > > direct
        > > > > arrival
        > > > > > peak in the pulse response. Fix time windows as e.g. used
        in
        > > ETF
        > > > or
        > > > > > smoothing methods like 1/n octave averaging do not give the
        > > true
        > > > > results.
        > > > > >
        > > > > > acourate applies both logsweeps and FDW. Thus the final
        > > > correction
        > > > > result is
        > > > > > a very good interchannel balance.
        > > > > >
        > > > > > Uli
        > > > > >
        > > > >
        > > > > I have asked this before a while ago with no repsonse. How do
        > you
        > > > set
        > > > > the window time dependent on the frequency?
        > > > >
        > > > >
        > > > >
        > > > > Cheers
        > > > >
        > > > > Thomas
        > > > >
        > > >
        > >
        > >
        > >
        > >
        > >
        > >
        > >
        > >
        > > Yahoo! Groups Links
        > >
        >
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