Considering Used Super V but NX-Otica is also on the table considering...

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Danny Richie

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Did that dip that you were seeing at 1,8kHz go away?

danvprod

It's still there...



This is with using the PEQs on the plate amps to try and flatten out the ~ 70Hz peak at the listening position.



danvprod

This is left vs. right; only the coax playing, measurement about 1/4" off the dustcap and off-center.


Green is left, orange is right.

Danny Richie

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This is left vs. right; only the coax playing, measurement about 1/4" off the dustcap and off-center.


Green is left, orange is right.

I'll help you figure out what is making that dipped area on the right side and get you balanced out.

danvprod

Thanks, Danny! Will continue this convo over PM...

mlundy57

The thought process behind diagnosing and fixing an issue like this would be very informative. I've recently learned how to use REW to see what is going on but knowing what to do about it is another issue entirely.

Mike

danvprod

Mike -- just in the interest of troubleshooting this in this thread, at Danny's suggestion, I tried the following.

1) Swapping the left and right tweeters, to see if the dip followed the tweeter or if it stayed with the speaker. Measurements would indicate that the dip indeed followed the tweeter.



2) With original configuration of tweeters (L on L speaker and R on R speaker), I disconnected the mid-bass drivers and measured to see if the dip was still with the R tweeter or if there was a tweeter/mid-bass interaction. Measurements would indicate that the dip is apparent in both configurations.


Green and red traces are right speaker (with original CD installed on right V). Blue and orange are left speaker.
 
Other than the dip, the two channels look pretty closely matched. I'd assume that the peaks and dips > 4kHz or so are highly dependent on microphone position; the delta I see between L and R speakers is that 1.8 kHz dip alone.

I'll report back anything else we figure out.

Danny Richie

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I didn't see that you posted the same thing here too. I responded to your PM.

mlundy57

Mike -- just in the interest of troubleshooting this in this thread, at Danny's suggestion, I tried the following.

1) Swapping the left and right tweeters, to see if the dip followed the tweeter or if it stayed with the speaker. Measurements would indicate that the dip indeed followed the tweeter.



2) With original configuration of tweeters (L on L speaker and R on R speaker), I disconnected the mid-bass drivers and measured to see if the dip was still with the R tweeter or if there was a tweeter/mid-bass interaction. Measurements would indicate that the dip is apparent in both configurations.


Green and red traces are right speaker (with original CD installed on right V). Blue and orange are left speaker.
 
Other than the dip, the two channels look pretty closely matched. I'd assume that the peaks and dips > 4kHz or so are highly dependent on microphone position; the delta I see between L and R speakers is that 1.8 kHz dip alone.

I'll report back anything else we figure out.

If I'm understanding this correctly your troubleshooting would indicate the dip is in the mid-bass driver of the right speaker and not a room interaction, correct?

Mike

danvprod

The measurements would indicate to me that there is something up with the right side tweeter. It is not a room issue as these IRs were measured 1/4" from the dustcap.

mlundy57

I see. The more I thought about it I realized I read your post incorrectly. You tested it tweeter only and tweeter/mid base combined but not mid bass only.

So if it is there tweeter only and does not change when the midbass is added then the issue is in the tweeter.

Or so it would seem.

Mike

danvprod

Right the dip is there with tweeter only and tweeter and misbass playing together.

mlundy57

Would that indicate a bad tweeter or just a mismatch between the two tweeters?

ebag4

Perhaps the tweeter's polarity is reversed??

Best,
Ed

danvprod

@Ed -- that is what Danny thought as well, but it's not the case. Both tweeters are measuring negative polarity (correct given 12 dB/octave XO) and both mid-basses are measuring positive polarity.

@Mike -- not sure about a mismatch, being that the rest of the frequency range tracks so closely L/R tweeter it is suspect that there is a 13 dB difference at 1865 Hz...

mlundy57

It also looks like it drops over a couple hundred Hz and climbs back up over the same span.

It seems really odd that it would be so specific and symmetrical. So does the next step of the investigation look at network components or would the network not have any bearing on something like this?

Mike

ebag4

@Ed -- that is what Danny thought as well, but it's not the case. Both tweeters are measuring negative polarity (correct given 12 dB/octave XO) and both mid-basses are measuring positive polarity.

Just clarifying, I am referring to the tweeter voice coil polarity and not the crossover circuit polarity.  With the V1 tweeter it would be easy to have the wrong color terminal on the tweeter, I believe the Super V will be built in a similar fashion.

Best of luck,
Ed

danvprod

Thanks Ed. I used an acoustical polarity signal (speaker pop) and played it through the co-ax (tweeter alone and mid bass alone). And then I put a microphone on to measure the polarity. In both cases (L and R), acoustically they measured negative. Both mid-basses measured positive. I think if the VC was reversed the polarity would be positive, correct?

Dan