[srb]

Speaker drivers are electro-mechanical transducers.

So are microphones, and quality among them varies greatly.  The average studio microphone costs between $1000 and $5000 (and more).

So I would be suspect of test results anyway without using the very best a very high quality microphone and A/D converter in the test rig.

Steve

[Art_Chicago]

Now, about the falling top-end response - I do not know how well the mic is set-up on the tweeter axis. If it is off-axis much it will contribute to an even greater drop, so this is something to consider as well.

I always check my speakers in my room using an RTA with pink noise to see how the balance looks in-room. When the balance is very flat at one meter it will still show a significant loss in top octave energy at 8-10 feet, but it doesn't sound that much different, because at that distance we are hearing a greater proportion of the speaker's power response, which the mic does not pic up.

With most speakers, people don't normally listen on-axis, so the on-axis response doesn't mean much. (It's a very small part of the overall output of the speaker.)

What is far more important is the off-axis response and power response. What are these like in the various Salk models? I've seen some of the graphs on the web site, but they were only at one angle and weren't anything special anyway.

turkey;

Here is a cut&paste from Nels Ferre's review on ST dome tweeter speakers which can be found elsewhere.


Even more impressive, in my opinion, is the frequency response plot is still pretty smooth all the way to 15kHz, where it drops off rapidly. The high frequency extension at 60 degrees (!) off axis is phenomenal ? most manufacturers do not disclose this information, and those who do tend to disclose a more forgiving angle. All of the measurements of other loudspeakers that I have seen performed by the National Research Council of Canada, an independent testing facility, "only" go to 30 degrees off axis. Not only does this indicate an excellent design, but also that more people in the listening area will be able to hear most of the music, rather than those seated in the "sweet spot." The off axis response also indicates that the SongTower QWT should image quite well.

[turkey]

turkey;

Here is a cut&paste from Nels Ferre's review on ST dome tweeter speakers which can be found elsewhere.

Yes, the graph shown there at 60 degrees is nice-looking. I wonder what it looks like at other angles?

I wish that more speaker manufacturers and more reviewers would show detailed info on the polar response of speakers.

[turkey]

Speaker drivers are electro-mechanical transducers.

So are microphones, and quality among them varies greatly.  The average studio microphone costs between $1000 and $5000 (and more).

Studio microphones are designed differently than instrumentation microphones, and are for different purposes. I don't know that it's useful to compare prices in this way.

So I would be suspect of test results anyway without using the very best a very high quality microphone and A/D converter in the test rig.

Steve

Good repeatable FR in an instrumentation microphone isn't that difficult to achieve. You can get mass-produced condensor mics that are like peas in a pod and are suitable for this use.

Flat FR in an A/D converter is quite easy to achieve too. We're not dealing with RIAA curve phono preamps here...

We're also not seeking a really high degree of precision in most cases. Differences between mics of say 0.5 dB or even 1 dB aren't going to be that noticeable since the response of most speakers will vary at least that much or more in production due to variances in drivers and other components. In other words, there's no point in designing the FR to 0.00001% tolerances if the drivers are going to vary by 10% or more in production anyway. Horses for courses.

[audiocrazy]

I could graph his data for him if he send me the data file.  I've done that with other forum members in the past to show them things.   

I've send you a PM and if you send me your email address I can email my files to you.

I downloaded the ECM8000 cal file from Hometheatershack rew forum. and here is the link
http://www.hometheatershack.com/forums/downloads-area/19-downloads-page.html

Here is the part of data what i have in my cal file.
1000.0   0.00
1120.0   0.10
1250.0   0.12
1400.0   0.02
1600.0   -0.28
1800.0   0.11
2000.0   0.19
2240.0   -0.15
2500.0   0.21
2800.0   0.14
3150.0   0.08
3550.0   0.44
4000.0   0.67
4500.0   0.78
5000.0   0.89
5600.0   1.28
6300.0   1.78
7100.0   1.85
8000.0   2.55
9000.0   3.93
10000.0   4.46
11200.0   4.29
12500.0   4.73
14000.0   4.99
16000.0   5.35
18000.0   5.70
20000.0   5.37
22400.0   5.09
25000.0   4.48

[TJHUB]

I could graph his data for him if he send me the data file.  I've done that with other forum members in the past to show them things.   

I've send you a PM and if you send me your email address I can email my files to you.

I downloaded the ECM8000 cal file from Hometheatershack rew forum. and here is the link
http://www.hometheatershack.com/forums/downloads-area/19-downloads-page.html

Here is the part of data what i have in my cal file.
1000.0   0.00
1120.0   0.10
1250.0   0.12
1400.0   0.02
1600.0   -0.28
1800.0   0.11
2000.0   0.19
2240.0   -0.15
2500.0   0.21
2800.0   0.14
3150.0   0.08
3550.0   0.44
4000.0   0.67
4500.0   0.78
5000.0   0.89
5600.0   1.28
6300.0   1.78
7100.0   1.85
8000.0   2.55
9000.0   3.93
10000.0   4.46
11200.0   4.29
12500.0   4.73
14000.0   4.99
16000.0   5.35
18000.0   5.70
20000.0   5.37
22400.0   5.09
25000.0   4.48

PM'd you back.

[face]

It actually seems fairly obvious to me also, but unfortunately, I don't think my appraisal is going to agree entirely with TJHUB's conclusion, so you guys can do whatever you like with my comments here.

After reading through everything in the thread and looking all of the plots over I am seeing essentially what I would expect to see based on what I have read (with one exception, which I will get to in a minute).

First, regarding the mic calibration file, the Behringer ECM8000 is a fairly flat mic to begin with. Even to use it without a calibration file will not result in these apparent discrepancies, in fact I doubt you would notice the difference. Rather, I think the explanation is much simpler -

From what I gather, these are in-room response measurements measured at the listening location ( I did not see the actual distance specified, unless I missed it somewhere). If this distance is 8-10 feet then I would expect to see:

....room gain in the lowest octaves
....boundary cancellation and peaks due to the room response
....and a falling top two octaves due to directivity and absorption

And this appears to be exactly what we see. There is a difference between the two speaker, but he commented that he did not move them to the same location, so that can easily explain these differences too (at least partly).

Now, about the falling top-end response - I do not know how well the mic is set-up on the tweeter axis. If it is off-axis much it will contribute to an even greater drop, so this is something to consider as well.

I always check my speakers in my room using an RTA with pink noise to see how the balance looks in-room. When the balance is very flat at one meter it will still show a significant loss in top octave energy at 8-10 feet, but it doesn't sound that much different, because at that distance we are hearing a greater proportion of the speaker's power response, which the mic does not pic up. Again, what I see in these graphs correlates well with what I see in listening position measurements in my own room, with one exception.....

The dip at 2kHz in the one speaker should probably not be present in one and not the other. If his measurments were vertically off-axis (from the tweeter axis) then I could see picking up the beginning of a null in the lobing along this axis, but the top-end should be more rolled off if this were the case. Based on this, I tend to agree with Dennis, I think the tweeter in that speaker may be connected with the wrong polarity compared to the other speaker. Otherwise, I don't have much of any issue with what I am seeing here.

Jeff Bagby

Jeff hit the nail on the head! 

To the OP, dump Room EQ Wizard and download ARTA: http://www.fesb.hr/~mateljan/arta/

[Rocket]

Hi Audiocrazy,

Is there a problem with the sound of the songtowers in your system?  Is this the reason why you have taken measurements of the speakers?  Or were you trying to confirm that the speakers are okay after you replaced the tweeters?

Regards

Rod

[Scott F.]

I didn't realize audiocrazy had two identical threads running at the same time. 

Here's what I posted in the other thread. It may be of help explaining why the speakers measure as they do.

<snip>....I have ....Integra DTC-9.8 with Audyssey.

Bingo. That right there is your problem. I have the 9.8 also. I tried Audyssey calibration with the supplied mic and what I heard coming out of my system sounded exactly like how your graph reads. Go back into the 9.8 settings and defeat the EQing completely. Set everything to flat. When you do that your speakers will come back to life, mine did.


...some additional commentary for this thread;

After hearing how bad the Audyssey "calibration" screwed up the sound of my HT system, I'll never use it again...but that's just my opinion.

[jsalk]

After hearing how bad the Audyssey "calibration" screwed up the sound of my HT system, I'll never use it again...but that's just my opinion.

I have never played with Audyssey and do not know if there is a learning curve involved.  I did not want to mention any particular system by name, but I did allude to this in a post earlier in this thread.  I have run into this a number of times now.  In each case, I asked the owner to please turn this off and check the speakers with Audyssey out of the system.  In every single case, the "problem" of poor sound quality was solved.

Like I said, I have never worked with Audyssey before and it may indeed be a wonderful system.  But when on numerous occasions turning it off solved the problem, I do have my reservations.  It is obviously not a fool-proof solution and is certainly capable of doing more harm than good.

- Jim

[Nuance]

Turn all room EQ off, then re-measure and used the proper setup, calibration, speaker placement and room treatments to get the FR flat from 200Hz to 20KHz. 

[audiocrazy]

Turn all room EQ off, then re-measure and used the proper setup, calibration, speaker placement and room treatments to get the FR flat from 200Hz to 20KHz. 

Sorry for the absence as I was caught up with work
Brandon i did all this but the same result and I suspect my mic rolls off quickly after 10KHz. I checked few threads over HT shack and there are people who has similar problem like mine. I'm not loosing sleep over it.

I've sent my mic for full professional calibration from 5Hz-25Khz. I'll re-measure after i get my mic calibrated.

[Nuance]

Sounds good.  We look forward to seeing if that helps.

[fsimms]

I've sent my mic for full professional calibration from 5Hz-25Khz. I'll re-measure after i get my mic calibrated.

Remember to check on why it is showing a peak at 18HZ.  If you post that again Jim will have to raise the price of the SongTowers to over 10k then! 

Bob

[Nuance]

I honestly don't think calibrating the mic will make a significant difference.  You've got some crazy room node action going on there.  I'd guess your room is a little too dead in the HF's. 

Would it be possible to post pictures of your room?  Also, when time is available, experiment with speaker placement.  Start moving them a little and see what you come up with.  Remember, the MIC position is crucial.  It needs to be at ear level and unmoved during the entire measurement process. 

Also, do NOT use the HTS MIC calibration file.  It won't change much, so I'd try measuring without it (although, you said you sent it off for professional calibration, so I guess you can't do that.). 

Both tweeters roll off sharply at the same place, so it's either the MIC or the room in my opinion.  Just to be sure, though, have you tried swapping out cables (speaker wire), as a loss of resistance could be occurring?

Best wishes to you!

[audiocrazy]

I honestly don't think calibrating the mic will make a significant difference.  You've got some crazy room node action going on there.  I'd guess your room is a little too dead in the HF's. 

Would it be possible to post pictures of your room?  Also, when time is available, experiment with speaker placement.  Start moving them a little and see what you come up with.  Remember, the MIC position is crucial.  It needs to be at ear level and unmoved during the entire measurement process. 

Also, do NOT use the HTS MIC calibration file.  It won't change much, so I'd try measuring without it (although, you said you sent it off for professional calibration, so I guess you can't do that.). 

Both tweeters roll off sharply at the same place, so it's either the MIC or the room in my opinion.  Just to be sure, though, have you tried swapping out cables (speaker wire), as a loss of resistance could be occurring?

Best wishes to you!

My room is heavily treated with GIK acoustic panels. I took measurments without the panels but the same result and yes I also took measurement without the mic cal file. Nothing helped.
That's why i suspect that my mic needs calibration.
I'll remeasure with various combination after i get my mic calibrated.


Brandon here is the link to pics of my HT room. Any suggestions.
Front
http://www.flickr.com/photos/arshadmalik/sets/72157616172223502/
Side walls
http://www.flickr.com/photos/arshadmalik/sets/72157616172168822/
Rear wall
http://www.flickr.com/photos/arshadmalik/sets/72157616172074934/

[Nuance]

Thanks for the info. 

Well, your speaker positioning looks good (not to close to the boundaries).  You're right, you DO have a lot of acoustic panels...maybe too many.  But you said removing them made no difference (which they certain should make a difference).  That right there tells me there is something wrong with the mic or the calibration of the sound card you're using to measure.  Which soundcard did you use, and are you absolutely positive the calibration is solid? 

Looking at Terry's calibration of his Behringer mic, that dropoff makes me wonder...  In fact, it's the same dropoff that your measurements are showing.  Terry's doesn't drop off like that, but it makes me wonder if your .cal file was working properly, thus the measured response followed that sharp downward slope.

Finally, have you experimented with more toe-in?  Since you aren't sitting immediately on-axis of both speakers, there should be some natural roll-off in the HF's (typical in many rooms at that listening distance), but not that sharply.  Just for kicks, try toeing them in so they point directly at your ears.  Of course, don't do that until you've re-measured with your newly calibrated mic, as the mic may have been the problem and everything else will then be moot.   

[Rocket]

Hi Audiocrazy,

Is there a problem with the sound quality of the speakers?

Regards

Rod

[audiocrazy]

Hi Audiocrazy,

Is there a problem with the sound quality of the speakers?

Regards

Rod

Rod my speakers seems to be fine .
I took REW graphs to check how my room FR looks like to get the best out of my Song Speakers. And to figure out if there are any EQ issues that need to be addressed either by changing speaker placement or applying any acoustic treatments.

[avahifi]

Then there is the easy way to do all this.

Just play a track of white noise, set the speakers side by side, have a friend run the balance control back and forth, move head just enough to stay as close as possible to on axis with each while listening. Any differences between the speakers will be obvious.

With a good speaker and drive electronics in a reasonably damped room, you should hear the sound of a rather large waterfall in the near distance  - - - like it it is ahead just around the next corner of the hiking trail.

Regards,

Frank Van Alstine

P.S.  This method will also quickly point out any significant peaks or dips in the response of two different speaker brands or designs,  the best "waterfall" wins.