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Discussion Starter #1
First, this is a great forum and a great tool.

I've just completed my first measurements as shown below and could really use some of the expert advice out there on interpreting these results - and as importantly - what to do next.
I've also attached a room drawing with enough detail to give you the picture. No existing - or potential for - wall treatments, bass traps, etc. as this is our living room and the WAF is very low as is.... Den (System room) floor is carpeted w/ 8' ceiling. The rest is wood floor w/ 12' vaulted ceiling.
FWIW, system is BDP83-se, VPI Classis w/Shelter 7000, BAT vk-55se amp, BAT vk52-se pre, Aqvox phono pre, Ref 3a Grand Veenas
I really appreciate your advice. thanks!!

condo 111910.jpg
spl phase.jpg
filtered ir.jpg
waterfall.jpg
gd.jpg
rt60.jpg
decay.jpg
spect.jpg
 

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First, welcome to the Forum!

That’s a really severe roll-out of the high end you have. Hopefully it's a result of your measurement technique and not your speakers. What mic orientation (e.g. 0-degree, 90-degree, etc.) and calibration file (ditto) are you using ? Is that a measurement of one speaker, or both?

Not sure what to recommend next if the wife has ruled out treatments and bass traps. :) But it looks like you could benefit from some full-range equalization.

Regards,
Wayne
 

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Discussion Starter #4
Yeah, not sure what to think about that rolloff myself...
I used 0 degreees mic orientation and the 0 deg calibration file.
pointed the mic straight ahead. both speakers on.
did it twice to make sure ...both the same.

experimentating a little now with vandersteen speaker placement method to see if it helps.....

any other thoughts about what the rolloff might be caused by?
 

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Discussion Starter #6
The BAT preamp has no tone controls....balance and phase only. The system is all fairly high end stuff, and it doesn't sound dull, so I'm thinking I must have done something technique wise...but don't know what it would have been...
 

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jstrouth said:
I've just completed my first measurements as shown below and could really use some of the expert advice out there on interpreting these results - and as importantly - what to do next.
Hi,

To get a better idea of the speakers' true response , I suggest that you take a few more measurements of the individual speakers ( ie ; singularly ) .

(i) Take a measurement of each at a distance of 1 meter / on axis, with the mic located equal-distance between the tweeter & midrange . ( & then )

(ii) One of each at 1/2 meter / same mic location as above .

(iii) One of each at 2 meters / same as above .

(iv) Then one of each at the preferred listening position ( test mic located at ear level )

(v) Then ( at the listening position ) both speakers ( tested at ear level ) .

- Doing all this will give you a good idea of what the HF response of the speaker actually is ( the closer the mic is to the actual source / the less, you're measuring the effects of the room acoustics on the speaker ) .

- FYI, there is a preferred listening curve ( for some listeners , the X-Curve "works" well ) that one should see at the listening position ( the "X-Curve" is somewhat less severe in it's HF roll-off than what you show ) .




- Personally, I prefer more top & bottom than what the X-Curve gives .


<> cheers EarlK
 

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Discussion Starter #8
Thanks!, That was actually what I'd thought about doing next as well. These speakers are supposed to be 36 - 20K +-3db.... and they have a murata supertweeter as well, so I can't believe they're rolling off that much. I can also test the response straight out of the preamp easily enough. Not sure how to test from the amp out, though.
 

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Thanks!, That was actually what I'd thought about doing next as well. These speakers are supposed to be 36 - 20K +-3db.... and they have a murata supertweeter as well, so I can't believe they're rolling off that much. I can also test the response straight out of the preamp easily enough. Not sure how to test from the amp out, though.
Agree with Earl. Do a close-mic measurement. It will give you a general idea of your speakers FR. My mains do roll off at listening position but not that much... Have you try to listen to your tweeters? I have a tweeter failed on me before... I didn't realized it until I feel something is missing...

Al,
 

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Discussion Starter #10
Thanks for the good advice. I don't know exactly what I was doing, but here are results that seem more like it. So back to my original question..... Can you help me interpret these graphs? And what advice for improvement? Thanks!!!

Right Speaker at 3'
right spkr 3ft.jpg

left speaker at 3'
left spkr 3ft.jpg

Both speakers at listening position
spl phase.jpg

and the rest of the graphs - both speakers at listening position.
waterfall.jpg
filtered ir.jpg
rt60.jpg
decay.jpg
gd.jpg
spect.jpg

I appreciate your help!!!
 

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Discussion Starter #12
Many apologies.... neglected to see the '-' part of 45....

In addition to your general advice, what explanation is there for the roll off at the listening position, relative to the much more flat response nearfield? if that's a room issue, i presume there's something i can do about it? although it pretty well matches the x curve provided above (or does it?), a little more high end energy would be ok by me. thanks for your patience with my newbie fumbling!

both speakers at listening position
spl phase.jpg

left only at 3'
left spkr 3ft.jpg

right only at 3'
right spkr 3ft.jpg
 

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Discussion Starter #13
Also, I'm presuming that much of the difference in left and right speaker nearfield response is due to the non-symetric room?
 

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In addition to your general advice, what explanation is there for the roll off at the listening position, relative to the much more flat response nearfield? if that's a room issue, i presume there's something i can do about it?
Hard to pinpoint an exact cause not knowing anything about your room, distance from the speakers, etc., but the fact that they’re measuring flat up close tells me it might be just the way they are. I would expect speakers with the highs measuring fairly flat at the listening position to show a rise in the high end up close. You might try Googling for some reviews to get some more insight.


although it pretty well matches the x curve provided above (or does it?),
You don’t want an X curve for home theater. You can find a piece about that in my signature. Google “x curve” and you can find another good article from HomeTheaterHiFi.com.


Also, I'm presuming that much of the difference in left and right speaker nearfield response is due to the non-symetric room?
Most likely but notice that they track pretty close down to ~500 Hz. Below 500 Hz the room is more of an influence.

Regards,
Wayne
 

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In response to your general question, what can you see in the graphs, here are a couple of other observations.

1) Looking at your earlier graph that included the impulse response, you can see the elevated response about 3ms and 6ms after the initial impulse. This matches distances of about 3.5 and 7 feet, perhaps reflections off the front wall and the side walls. (You did not give the dimensions in your first picture to confirm this.)

2) In the RT60 and the spectrogram, you can see the longer decay times in the middle frequencies, 700Hz-4kHz. That's a little unusual, one would expect furnishings and walls to be more absorptive as the frequency rises. I'm not sure exactly what that indicates, whether that says something about the materials in your walls.

3) In the waterfall, obviously the longest decay is ~16Hz. Not much you can do about that, but as your speakers' frequency response already falls off above that point, I don't expect this to be an audible issue.

Have fun,
Bill
 

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Discussion Starter #16
Wayne, thanks. I'm at an equilateral triangle with speakers, which are ~91/2 feet apart.
This is a 2-channel setup. Does that mean that x curve IS what I should strive for?
If I understand, you're saying it is a room response issue that causes the rolloff of the highs? What might cause that? Any way I can get a little more high end at the listening position?

Laser, Thanks. Although I didn't include distances, you're correct I believe, about the front and side wall reflections. Traps are out of the question in this room, however. I have no treatments at all.
Could it be that perhaps the high vaulted ceiling in the main part of the room (not the L where the system is located) is causing the longer delays you mention? What is the audible result of the RT60? And decay in general....
Thanks so much. I'm learning .... hopefully!
 

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This is a 2-channel setup. Does that mean that x curve IS what I should strive for?
No, I would not recommend an X curve for any home audio system.

If I understand, you're saying it is a room response issue that causes the rolloff of the highs?
No - as noted above, I think this is just the way they are. That they measure flat up close means they will naturally show reduced high end several feet away at a normal listening position. You don’t have the treble control of your pre-amp dialed down do you?

In addition, you could see some inaccuracies in the top frequencies if you’re using our generic calibration file for your ECM8000 mic. Perhaps it’s not a good match for your particular example. Also if you're measuring with the mic positioned vertically that would show a roll-out of the high frequencies, as our calibration file was generated for a horizontal orientation.

Regards,
Wayne
 

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Discussion Starter #18
I'm at a bit of a loss. Where does the high end go if its going out of the speakers but not making it to the listening position? The preamp has no tone controls.
Mic is calibrated from cross-spectrum.

Is off axis possibly part of the problem? I can't go straight on axis with the speakers (per mfgr recommendations) or I'll loose their phase alignment. But some toe in is possible - I have about 5 degrees now. Would that help? Anything else?
 

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... Is off axis possibly part of the problem? ...
That's a likely hypothesis. As you are already doing near field measurements of the speakers, you could move the microphone off axis, still pointed at the speaker, and take measurements at various angles to see how the response curve changes.

Or you could just try pointing the speakers at your listening position, and measure whether and how much the curve changes.

Bill
 

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I'm at a bit of a loss. Where does the high end go if its going out of the speakers but not making it to the listening position? The preamp has no tone controls.
It’s a known acoustical fact that as sound travels through air, high frequencies are attenuated more than low frequencies. This is why speakers exhibit greater high frequency energy when measured up close. And you can easily hear that speakers will sound brighter if you sit closer to them.

You can easily observe this using REW’s RTA feature. You will see the highs increase or decrease as you move the mic closer or farther from the speaker.

Is off axis possibly part of the problem?
Partially, but I’d be surprised if that’s a significant factor. That would mean your speakers have a really tight “laser beam” dispersion pattern from the tweeters. That’s generally not the way hi-fi speakers are designed.

Regards,
Wayne
 
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