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Bose 901 EQ distortion



 
 
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  #21  
Old December 8th 07, 10:43 AM posted to rec.audio.tech
Peter Larsen[_2_]
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Posts: 724
Default Bose 901 EQ distortion

Richard Crowley wrote:

> "GregS" wrote...


>> "Richard Crowley" wrote:


>>> Is the curve of the Bose EQ box published anywhere?


>> I think I saw it on the patent.


>> Anyway, its flat from 100 to about 2 kHz. There is up to an 18 dB
>> peak at 30 Hz,
>> and a 12 dB peak at 12 kHz. Essentially, most everything is lost
>> above 12 kHz.


Studio sound mentioned 22 dB of eq, which lead to it being impossible for
Hugh Ford to measure on the eq version they tested because 1 volt input at
20 kHz caused clipping. I can't get into detail, the paper the print was on
has been recycled long time ago.

> That would make a bullhorn or a telephone sound good! :-)


We have to take this in stages, first we teach him what a good EQ is, next
he begins to wonder - like everybody else - about the wisdom of using
midrange units for full range audio. It is no good to just flame the
boseaholics, they need to be taught. It is of course cheaper to just replace
the loudspeakers without getting another eq or getting the broken one fixed,
except that Bose reportedly will take a look on the actual eq box and fix it
if broken.

In the real life, outside the world of the brochures, many loudspeaker-room
combinations will benefit from eq, but as a general guideline something is
broken or ill applied if more than 6 dB boost is relevant, narrow 8 db cuts
may be very relevant in the low range in rooms that have no low range
acoustics regulation, ie. bass traps.


Kind regards

Peter Larsen


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  #22  
Old December 9th 07, 10:12 PM posted to rec.audio.tech
Chris Kidd[_2_]
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Posts: 3
Default Bose 901 EQ distortion

I have 33 Bose 102 ceiling speakers installed as under-balcony delay in the
theater where I work. It had a 102 system processor and analog eq/delay
units when originally installed. When the processing was replaced with a BSS
minidrive, the guy who eventually RTA'ed the room said he took a sample of
the 102's EQ pattern by sending a pink noise signal through it and analyzed
the output signal to see what kind of curve the processor provided and used
this as the basis for the minidrives programming "flatline" and then
correcting for room response with the rta. Could you take a new "DSP box"
and analyzer and make your own "901 EQ"?

Chris


"Peter Larsen" > wrote in message
...
> Richard Crowley wrote:
>
>> Is the curve of the Bose EQ box published anywhere?

>
> It looks like the image of a gletcher valley cross-section ...
>
> Someone over in a.a.p.l-s linked to an image of an analysis of it, i have
> it somewhere on some harddisk, mostly I think it was about the 802's ...
> but in case of the deq one just needs a measuring microphone and to aim
> for the b&k living room reference curve, the simplified version is flat up
> to 200 Hz and then drops smoothly to -6 dB at 20 kHz, aiming for
> perfection at the extremes is folly.
>
> The OP should remember that while there are many frequency analysis
> displays that can be used with a pc most of them display white noise as a
> horisontal line and pink noise as a line that slopes with -3 dB pr.
> octave. It may be unwise to measure loudspeakers with white noise .... I
> haven't got a DEQ, but I think it has measurement analysis built in, other
> folks know a lot more about it.
>
> The extra AD-DA conversion may be unattracive .... but it may also be
> avoidable, depending on actual context.
>
>
> Kind regards
>
> Peter Larsen
>



  #23  
Old December 10th 07, 04:46 AM posted to rec.audio.tech
Richard Crowley
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Posts: 4,172
Default Bose 901 EQ distortion

"Chris Kidd" wrote in ...
>I have 33 Bose 102 ceiling speakers installed as under-balcony delay in
>the theater where I work. It had a 102 system processor and analog
>eq/delay units when originally installed. When the processing was
>replaced with a BSS minidrive, the guy who eventually RTA'ed the room
>said he took a sample of the 102's EQ pattern by sending a pink noise
>signal through it and analyzed the output signal to see what kind of
>curve the processor provided and used this as the basis for the
>minidrives programming "flatline" and then correcting for room response
>with the rta. Could you take a new "DSP box" and analyzer and make your
>own "901 EQ"?


Dunno why not. A speaker is a speaker, whether it says Bose on
it or not. The bottom line is what it sounds like in the audience
area, so RTA'ing the room may be a good solution to dealing with
whatever wierdness of Bose drivers.

  #25  
Old January 3rd 08, 08:23 PM posted to rec.audio.tech
Steven Sullivan
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Posts: 1,268
Default Bose 901 EQ distortion

wrote:
> On Dec 5, 2:22 pm, Chris Morriss > wrote:
> > In message
> > >,
> > writes
> >
> > >Hello all,
> > >First, I like my 901s regardless so no flaming please.
> > >I need help with this condition:
> > >I have two sets of 901's. One pair of series IV and one pair of
> > >series VI, both with the matching Bose EQ.

> >
> > >My problem is that some CD,s and even some passages on soother CD's
> > >cause distortion when using the EQ. This can be at any volume level.
> > >I have only had this problem with recent CDs. (Diana Krall, Chris
> > >Botti) All my older CD's and the radio plays fine and loud. I have
> > >tried different recievers, CD decks and even replaced all the caps in
> > >one of the EQs. Anyone else having issues or know where I can find a
> > >service manual for these EQ's?
> > >Really appreciate the help

> >
> > Perhaps the high output signal is overloading the input on the
> > equaliser. Can you make up a simple 6dB pad (a couple of 10k resistors
> > in an 'L' network for each channel)? This may drop the signal enough.
> > What is the input spec for the equaliser? Modern highly-compressed CDs
> > may be putting out 2V rms or so and that may be the problem.
> > --
> > Chris Morriss


> Thanks for the help folks. Yes the problem seems to be on both
> channels and I have tryed it on two different systems. I was
> thinking to try attenuation as well. I have tried different CD
> players and even drove the eq's input off of a portable cd deck
> headphone jack with varied volume output and could detect the
> distortion at very low levels. Does the RMS voltage value remain
> constant on a headphone channel?


Something's odd here.

Are Diana Krall's CDs noted for being mastered at high levels?

The loudness wars have been raging since before hte mid-90's,
so I'm surprised these are the only two CDs that show this
effect with your Bose EQs.



___
-S
"As human beings, we understand the world through simile, analogy,
metaphor, narrative and, sometimes, claymation." - B. Mason
  #26  
Old November 17th 10, 10:56 AM
mariarayan mariarayan is offline
Junior Member
 
First recorded activity by AudioBanter: Nov 2010
Posts: 8
Default

Quote:
Originally Posted by Serge Auckland View Post
"Mark D. Zacharias" > wrote in message
. net...
>
> > wrote in message
> ...
>> Hello all,
>> First, I like my 901s regardless so no flaming please.
>> I need help with this condition:
>> I have two sets of 901's. One pair of series IV and one pair of
>> series VI, both with the matching Bose EQ.
>>
>> My problem is that some CD,s and even some passages on soother CD's
>> cause distortion when using the EQ. This can be at any volume level.
>> I have only had this problem with recent CDs. (Diana Krawl, Chris
>> Botti) All my older CD's and the radio plays fine and loud. I have
>> tried different recievers, CD decks and even replaced all the caps in
>> one of the EQs. Anyone else having issues or know where I can find a
>> service manual for these EQ's?
>> Really appreciate the help

>
> Many recent vintage CD's are mastered LOUD and compressed. May be a maxxed
> out, clipped signal being fed to the EQ, or the EQ may be running out of
> headroom, again because of the nature of the signal itself. One would need
> to look at the signal with an oscilloscope at the input of the EQ, at
> various points inside (at the output pins of the various op-amps inside
> for example) and at the output of the EQ itself.
>
> If the signal is reaching the box that way, you may need a different
> source unit since the clipping may be occurring there or for that matter
> might be coming out of your CD player that way.
>
>
> Mark Z.

Indeed. I have known some early CD players that would clip by 0dBFS. This
wasn't that much of an issue in the early days of CD when mastering actually
left some headroom, but with recent CDs which hit 0dBFS pretty frequently,
this could be what you're hearing. I have checked one or two of my Diana
Krall CDs and they *are* taken to 0dBFS frequently.

Recent CD players shouldn't do this, but then again, they might.

S.
--
http://audiopages.googlepages.com

I got bad issues because of that, yeah you are right i think new CD players shouldn't do this
 




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