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Advice for Beginners - consider this test from an audio club

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1 minute ago, muel said:

The premise wasn’t worthy of a response 

 

=== well then, unworthiness has blessed us with nearly 80 pages of —???

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If I remember correctly, there was no comment made by the OP with regard to preamps specifically.  I’m guessing that “all modern preamps engineered to be linear sound the same”, would be the response of the OP.  I’m sure he will chip in...

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On 1/15/2019 at 7:05 AM, dwilawyer said:

Post some of those great curves you are famous for so they can really u understand.

 

Include the distortion ones as well.

 

Famous for?

 

The Klipschorn used to have a double hump, affectionately known to San Francisco Klipsch fans as "Twin Peaks," between 100 and 250 Hz, approximately.   These two peaks were reduced by the AK4 (c. 2002?) and later balancing networks.  It may have happened a bit earlier.  I haven't run any curves since 2011, when everything went to hell in a basket (my mic preamp stopped working right, then there was a computer crash).   I'm sure others have some they can contribute.  

 

Reducing the Belle resonance was strictly by ear. 

 

Below we have a Klipschorn curve, taken from just one mic position (a "no-no" when measuring in a real room, I'm told).   There is a minor

peak just above 100 Hz, maybe 2.75 dB or so.  Given that I cross the Khorns over to the subwoofer at 80 Hz, I decided to not try to fix the truly big peak at 43 Hz.   Guess what, the sub had a peak in just the same place and of about the same magnitude.  The only peak I hear from the Klipschorns above the 80 Hz Xover is the one at about 375 to 575 Hz.  I rarely notice it.  When I do, it doesn't sound like resonating wood at all, it merely sounds like a bit of overemphasis, and is as clean as can be.

 

 

748710246_2011curve.jpg.0c0780799ce026ffeaca2b0a58c02391.jpg

 

 

 

I wish I had distortion graphs.  Maybe someone else has.  I understand they might be possible with REW, but I never got into it.

I have some distortion figures, filched from others.   Some of the below came from Don B. Keele, Jr.  and some from reading Heyser's graphs.       


Speakers                          IM distortion at 105dB (reference level peaks)    Harmonic distortion at 105dB (reference level peaks)
Klipschorn                              1.75%                                                                            0.25%
AR 4-way AR 98RS                 2.7% (1.54XKH)  Audible                                       ~3% (~12XKH) Audible
Fried Studio 4                      10% (5.71XKH) Audible & Annoying                          4% (16XKH) Audible
Platinum Studio 2                  7% (4XKH) Audible and Annoying                           1.9% (7.6XKH) Audible

 

Since the mic preamp failure, I haven't been able to brew up enough enthusiasm to start measuring again.  My ears are happy now, so I think I can resist the temptation.

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5 hours ago, Tizman said:

I can try it with EQ, just to see if it makes any difference in my setup, but my preference would be to do it passively, and do it with some of the quality parts I have at hand. My last Behringer crossover made its presence know in a negative way.  It’s was noisy and you could hear it in the chain, so I’m leery  about buying another Behringer component.

 

Where do you live?

 

I have an extra EV Dx 38 laying around (actually two of them!!) 

 

If you wanted to cover shipping, you could borrow it for a while & play til you're hearts content.

 

 

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5 hours ago, richieb said:

=== well then, unworthiness has blessed us with nearly 80 pages of —???

 

One would think my threads would exceed 300 ...

 

:huh2:

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17 hours ago, Tizman said:

If I remember correctly, there was no comment made by the OP with regard to preamps specifically.  I’m guessing that “all modern preamps engineered to be linear sound the same”, would be the response of the OP.  I’m sure he will chip in...

 

Doing a DBT w/ pre-amps would be a pretty complicated affair.  But considering every modern pre-amp (ie., those being sold today) that I could find on web-retailers has THD <.01% and S/N ratios that exceed our hearing, I'm totally fine with extrapolating the results of the Amplifier challenge to mean that differences b/w pre-amps, if audible at all, are also apt to be so small as to be meaningless.  ..But you can draw your own conclusions

 

Personally, I think pre-amps in a 2-channel system are an anachronism.  In other words,  "why??"  When present day integrateds are so quiet, and  have such incredible S/N ratios what is achieved by separating power and pre sections?  That is, other than potentiating  buzz/ hum issues by adding more interconnects, another power cord and possibly another outlet.  Yes, i think separate 2-channel pre-amps these days are more or less pointless.

 

And yes, my MDF-edition Cornwall III's are STILL upright and undamaged by rogue moisture.  phew! 

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1 hour ago, Tizman said:

Thanks for your kind offer Coytee. I’ll send you a PM.

To get low enough for a contour, you will need to use some huge components along with having some impact on the Q of the woofer.

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Quote

that I could find on web-retailers has THD <.01% and S/N ratios that exceed our hearing,

 

Ya gotta love a guy that hangs his hat on that kind of crap. Julian Hirsch would have loved to have you as a reviewer.

 

"....of all the amplifiers I have heard, this is one of them...."

 

I might go out on a limb and say that there are a few amplifiers that would be indistinguishable in a blind test. But preamps? You'd have to be a fool to make that claim.

 

Shakey

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1 minute ago, Shakeydeal said:

 

Ya gotta love a guy that hangs his hat on that kind of crap. Julian Hirsch would have loved to have you as a reviewer.

 

 

yeah, and PWK as well probably.

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22 hours ago, muel said:

... What a nice difference there is dropping 148hz 7db (q=8)!    

Regarding this with La Scala's... If there is still too much "boom" in the room broaden the bandwidth by lowering the Q. 

Salt to taste    :) 

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7 hours ago, pzannucci said:

To get low enough for a contour, you will need to use some huge components along with having some impact on the Q of the woofer.

I was playing around with this online calculator....

http://www.mh-audio.nl/parallelnotchfilter.asp

and the components are in the 6 mH and 20 uF range more or less.  I bought a bunch of crossovers from a theatre redo, so I have a lot of components that could be used.  I’m not sure if I am using the calculator correctly though, as I have very little experience with crossover design.  I used 6 Ohms for the speaker impedance and 148 HZ and 7 DB for the filter, and 13 HZ up and down -3 DB points.  I don’t know if that is right though. (Am I supposed to use the actual impedance of the woofer in the cab at that frequency?  Are my -3 DB points appropriate?  Etc.)  I have these components (and many others) on hand, so it would be a cheap fix if it is doable.  I haven’t noticed any issues with the hump, but now I’m curious as to whether it will improve the sound.

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<sarcasm> If you've never tried to use a high-Q notch filter to correct a resonance and missed the center frequency by a small amount, then you're in for a treat.</sarcasm>

 

You'll get some of the weirdest phasey sounds that you'll ever hear.

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1 hour ago, Tizman said:

Hmmm.  Doesn’t sound like a plan then.

 

No need to abandon the idea. The important thing is to keep both the Q and the amount of cut low. Don't try to exactly compensate for the peak. Just try to soften it.

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5 hours ago, Tizman said:

I was playing around with this online calculator....

http://www.mh-audio.nl/parallelnotchfilter.asp

and the components are in the 6 mH and 20 uF range more or less.  I bought a bunch of crossovers from a theatre redo, so I have a lot of components that could be used.  I’m not sure if I am using the calculator correctly though, as I have very little experience with crossover design.  I used 6 Ohms for the speaker impedance and 148 HZ and 7 DB for the filter, and 13 HZ up and down -3 DB points.  I don’t know if that is right though. (Am I supposed to use the actual impedance of the woofer in the cab at that frequency?  Are my -3 DB points appropriate?  Etc.)  I have these components (and many others) on hand, so it would be a cheap fix if it is doable.  I haven’t noticed any issues with the hump, but now I’m curious as to whether it will improve the sound.

Closer to 4 ohm woofer is 200+ uf cap.  6+MH choke.  Uae the amplitude filter.  It will show the interaction of the filter with the driver.

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29 minutes ago, pzannucci said:

Closer to 4 ohm woofer is 200+ uf cap.  6+MH choke.  Uae the amplitude filter.  It will show the interaction of the filter with the driver.

The woofer is 4 Ohm, so I should use this instead of the woofer's impedance in the horn, which is closer to 6 Ohms?

 

2 hours ago, Edgar said:

No need to abandon the idea. The important thing is to keep both the Q and the amount of cut low. Don't try to exactly compensate for the peak. Just try to soften it.

What would be an appropriate reduction to shoot for?  Is 3-4 DB a better target?

Thanks for the input by the way!

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The red trace is my La Scala bass bin. The blue trace is a high quality direct radiator speaker box. The measurement mic was in front of a listening position across the room from the two side by side speakers.

 

This was just to see if the "150Hz hump" was something to be seriously concerned with. The hump was there at one meter measuring distance, but it levels out across the room, so I am not worried about it.

 

The dip at 320Hz changes when I move the mic around. Everything measures a little differently when the mic is re-positioned. 

 

1024439779_LaScalared.jpg.debf512a631af34fe9a200b1c5c4f9a0.jpg

      EQ switched off

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10 minutes ago, Tizman said:

What would be an appropriate reduction to shoot for?  Is 3-4 DB a better target?

Thanks for the input by the way!

 

I went back and read your earlier post more completely. A bandwidth of 26 Hz (±13 Hz) at 148 Hz center frequency is a Q of 5.7. That's a little higher than I'd recommend; I prefer to keep it below 3 or 4. A cut of up to maybe 6-7 dB should be OK at the lower Q, but you'll probably find that you don't need that much.

 

If you have active EQ available, I'd recommend experimenting before committing to capacitors and inductors.

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2 minutes ago, Khornukopia said:

The hump was there at one meter measuring distance, but it levels out across the room, so I am not worried about it.

Thanks for that.  It would appear that (as mentioned in several posts in this thread) the impact of the room, and the relative speaker and listening positions, can swamp the frequency response anomalies of speakers sufficiently to make attempted adjustments to the measured response at 1 meter unsuccessful.  I guess if you are able to adjust on the fly with a room correction program, it would be worth doing and much easier.  Maybe it's best to leave it be in my case, especially since I don't perceive any issues.

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