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post #1 of 38 Old 05-26-2020, 01:31 PM - Thread Starter
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Cnote - HF rise issue?

hello, just put together a pair of c-note speakers


sound ok thus far, however i felt they were really bright


took some measurements and indeed, they are, big rise starting around 6.5k+



thoughts on what could have caused this? i'm pretty sure i followed the directions to a T. and you'll note, identical responses on both. so whatever it is, i messed em up on both


EDIT: better REW measurement at 1ft and out in the middle of the room on stools to try and get rid of the nasty room mode. also good to see my L and R channels out of my Topping are matched . Taken with UMIK1



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post #2 of 38 Old 05-26-2020, 04:23 PM - Thread Starter
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i also did the .22 cap mod, i wonder if i botched something there? see the diagram i modeled after
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post #3 of 38 Old 05-26-2020, 05:56 PM
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Do you have C3 connected from tweeter positive to the common negative(in parallel with the tweeter)? I have a feeling a cap when placed like that would pull the top end down as it's shorting the high frequencies.
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post #4 of 38 Old 05-27-2020, 08:42 AM - Thread Starter
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Quote:
Originally Posted by mtg90 View Post
Do you have C3 connected from tweeter positive to the common negative(in parallel with the tweeter)? I have a feeling a cap when placed like that would pull the top end down as it's shorting the high frequencies.

yeah, sadly i'm not 100% able to check since i've got the crossovers mounted pretty good in there, and it's really a PITA to get them out


i'd say the only thing different to the picture that i did in real life was orient the caps in such a way that i was able to get C3 L1 and C4 all to touch physically without a wire lead from the C3/L1 to C4 (as indicated by the picture). i'm not aware that that would have an effect on it


i did just put my multimeter on the terminal cap, and read 7ohms, i'm not sure if that is indicative of anything. after connecting two wire leads and reading at the banana clip i got 7.6 (16awg wire, about 6ft). thinking i'm just not making great contact at the cup terminal for a good reading
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post #5 of 38 Old 05-27-2020, 08:53 AM - Thread Starter
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just to rule out my laptop, i'm going to grab another speaker to just ensure this isn't something processing or freq limiting on the headphone out. in windows sound settings all enhancements have been turned off, but ya never know
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post #6 of 38 Old 05-27-2020, 09:17 AM - Thread Starter
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ugh, appears not to be anything in my setup, here is just a ****ty polk speaker i have lying around, no noticeable HF rise
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post #7 of 38 Old 05-29-2020, 09:55 AM - Thread Starter
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noted on another forum, found that the topping tp22 has a bit of a rise due to the high resistance, so that certainly brought down some of the issue, but still very noticable


anyone with cnotes able to measure and confirm if this looks normal?


i pulled one of the crossovers, it matches the design spec, i'd really have to start unsoldering items to get measurements


denon avr in green, topping in blue for some reduction



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post #8 of 38 Old 05-29-2020, 12:17 PM
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I'm pretty sensitive to high frequency rise and my Cnotes don't exhibit this. They are slightly brighter than some of the Carmody designs, but not enough to bother me.


Here's what Parts Express says it should be like:

https://www.parts-express.com/pedocs...y-response.pdf
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post #9 of 38 Old 05-29-2020, 07:43 PM - Thread Starter
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Quote:
Originally Posted by _tk View Post
I'm pretty sensitive to high frequency rise and my Cnotes don't exhibit this. They are slightly brighter than some of the Carmody designs, but not enough to bother me.


Here's what Parts Express says it should be like:

https://www.parts-express.com/pedocs...y-response.pdf

agreed


here are the xovers


best i could do to document them
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post #10 of 38 Old 05-29-2020, 08:00 PM
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The crossover certainly looks correct.

Perhaps there was a small change in the latest batches of that tweeter. I'd try and take a measurement of just the tweeter without the crossover and compare it to the published curves for the ND25FW-4.
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post #11 of 38 Old 05-29-2020, 09:49 PM - Thread Starter
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Quote:
Originally Posted by mtg90 View Post
The crossover certainly looks correct.

Perhaps there was a small change in the latest batches of that tweeter. I'd try and take a measurement of just the tweeter without the crossover and compare it to the published curves for the ND25FW-4.

smart man, forgot to completely take out the crossover


- xover measurements -

the below shows a full sweep assembled

sweep with just the mid bass (mb)

sweep with just the tweeter (tw)


- no xover -
just the tweeter


the rise is gone without the xover (some rise can be attributed to the topping tp22, too lazy to drag out the denon which had a reduced rise, but still, keeping it all the same for consistency


now, i'd say perhaps i need to look at the soldering job, but this is producible on 3 individual builds (and i'm sure if i dragged out the 4th, we'd see the same), so maybe they changed the tweet, or maybe i screwed something up, just looking to figure out what that is...


edit, actual measurements
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post #12 of 38 Old 05-30-2020, 11:35 AM
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not just you. i recently built a set of c notes also and thought they were fairly bright considering the fact that everyone else had been saying they were a great set of speakers that were fairly flat. then again i have mine nearfield on my pc setup.
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post #13 of 38 Old 05-30-2020, 12:38 PM - Thread Starter
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Quote:
Originally Posted by jtl090179 View Post
not just you. i recently built a set of c notes also and thought they were fairly bright considering the fact that everyone else had been saying they were a great set of speakers that were fairly flat. then again i have mine nearfield on my pc setup.

any way you can measure? i wonder if perhaps they changed something in the tweeter?
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post #14 of 38 Old 05-30-2020, 01:17 PM
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Might be worth a call or email to Parts Express to see what they have to say. They are a great company, but sometimes the Quality Control isn't the best on the Chinese parts. My set of Cnotes last year came with a woofer (only one) that had a massively bent frame (and this didn't happen in shipment, it was like that when packaged as the box was perfect). They made it correct, but it was still a QC issue.

IIRC there was an issue with the PE Dayton B652's a couple years back as well as they measured completely different than what they had been even though the same components were being used.

Again, contact them and let them know what you're finding. If they were designed as a "bright" speaker, it'd be a well-known fact at this point.
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post #15 of 38 Old 05-30-2020, 04:53 PM
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Originally Posted by datrumole View Post
any way you can measure? i wonder if perhaps they changed something in the tweeter?
i can try to do something tomorrow. ill have to dig up my umik and install the software on this pc and relearn how to use it. i havent messed with it in a while now.
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post #16 of 38 Old 05-30-2020, 10:17 PM - Thread Starter
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Quote:
Originally Posted by _tk View Post
Might be worth a call or email to Parts Express to see what they have to say. They are a great company, but sometimes the Quality Control isn't the best on the Chinese parts. My set of Cnotes last year came with a woofer (only one) that had a massively bent frame (and this didn't happen in shipment, it was like that when packaged as the box was perfect). They made it correct, but it was still a QC issue.

IIRC there was an issue with the PE Dayton B652's a couple years back as well as they measured completely different than what they had been even though the same components were being used.

Again, contact them and let them know what you're finding. If they were designed as a "bright" speaker, it'd be a well-known fact at this point.

really good thought, i'll give them a call for sure. i 100% had the same experience as you. two busted 5" midranges, completely separate packages. one package damaged, ruined the driver, the other package nothing, driver basket bent to hell.



i'd agree that people are thinking now it's a bright speaker, however ever measurement i've found on the internet is not measurably bright....and i get it, it's 100 bucks, and no one is likely giving a ****, or hell, even has the capacity for measuring. but now i'm stuck. i know it's there, i can eq it, but hell, i want to see if something i can do to fix it, correct it, whatever


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Originally Posted by jtl090179 View Post
i can try to do something tomorrow. ill have to dig up my umik and install the software on this pc and relearn how to use it. i havent messed with it in a while now.

awesome, thanks! there should be plenty of forum post for how to use REW, quick and dirty way to get it going


1) install rew
2) it should auto-recognize umik, and ask for the calibration file, supply it
3) mini-jack (headphone) out to RCA in for whatever amp you are using
4) SUPER IMPORTANT: turn off all processing on both the computer, and if you are using an AVR, be in 'direct mode' (denon term). basically NO signal processing. on your computer, go to windows:control panel:sound. Hit config: ensure they are set to 'full range'. Leave that menu, go to properties. Ensure there is no dolby, realtek, or 'enhancements tab' that has any box checked. goal is to get full range un-altered sound to the speakers for measurement. for your AVR, ensure audyssey is turned off and any other EQ modes (bass, treble enhancements...)
5) open 'signal generator', set a -12dbFS, and choose 'pink noise'. also open 'spl meter', set to 'C' in the weighting, hit the record button. 'play' the pink noise and increase volume on avr/computer until you get to 75ish db (pick whatever, so long as it's >65ish)
6) measurement: ensure it measures from 20hz to 20000hz, -12dbFS, hit start, post the pic
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post #17 of 38 Old 05-31-2020, 05:53 PM
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really good thought, i'll give them a call for sure. i 100% had the same experience as you. two busted 5" midranges, completely separate packages. one package damaged, ruined the driver, the other package nothing, driver basket bent to hell.



i'd agree that people are thinking now it's a bright speaker, however ever measurement i've found on the internet is not measurably bright....and i get it, it's 100 bucks, and no one is likely giving a ****, or hell, even has the capacity for measuring. but now i'm stuck. i know it's there, i can eq it, but hell, i want to see if something i can do to fix it, correct it, whatever
Wow very informative write up. was able to just go ahead and plug it in and follow along. Split it into left and right speakers. According to the graph they are pretty flat. Maybe its just because im nearfield or maybe the style tweeter but theres just the slightest harshness to my ears. According to the graphs i dont know what im talking about.


Edit: not sure why but it kept dropping my images. heres the link to the imgur

https://imgur.com/a/Bdh8pYq

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post #18 of 38 Old 05-31-2020, 06:13 PM - Thread Starter
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Quote:
Originally Posted by jtl090179 View Post
Wow very informative write up. was able to just go ahead and plug it in and follow along. Split it into left and right speakers. According to the graph they are pretty flat. Maybe its just because im nearfield or maybe the style tweeter but theres just the slightest harshness to my ears. According to the graphs i dont know what im talking about.



ha yeah, the graphs are the most telling, however i dont see them attached to your post


two other quick things


when measuring, have the speaker hang off the desk a little, your first reflection point (the desk) will alter the measurement of just the speaker. youd want it there when yoi go to correct it, but not to see the pure response of the speaker



second, make sure to measure 1-3ft away from the speaker if possible and ensure to choose the proper mic calibration file. 90deg is for when you have the mic pointed at the ceiling
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post #19 of 38 Old 05-31-2020, 06:19 PM - Thread Starter
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also, some updated graphs of some additional measurements


one with the each of the individual drivers connected to the xover


then another set with just the raw drivers (and one full just to have a baseline comparison)



anyone with any additional thoughts?
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post #20 of 38 Old 05-31-2020, 06:38 PM
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Originally Posted by datrumole View Post
also, some updated graphs of some additional measurements


one with the each of the individual drivers connected to the xover


then another set with just the raw drivers (and one full just to have a baseline comparison)



anyone with any additional thoughts?
i think its the website. your graphs dont show either. i added a link above to the results.

https://imgur.com/a/Bdh8pYq
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post #21 of 38 Old 05-31-2020, 07:46 PM
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The short answer is: EQ can fix it. (Wideband 0.4Q -7db @ 16khz etc)
Or maybe try inverting the tweeter polarity, see if that makes it better/worse.

The longer solution would start by importing your REW sweeps for each raw-driver into XSim and plugging in the T/S parameters for each driver, and modeling the crossover.
See if that sims reality.

If not, then it is probably a complex interaction between the woofer and tweeter and crossover, a resonant feedback loop of induction/capacitance of the driver coils, magnetic field flux backEMF and crossover attributes of the same.
To model this properly you'd need a WT2 and import those charts into XSim, then you'd probably have to play with the crossover component values to get it right.
They probably didn't do that when they designed it. That would be my guess.

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post #22 of 38 Old 06-01-2020, 11:32 AM
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I'm not sure why you're spamming this on 3-4 different forums. Just call them. It could be a known issue already.

As I said, clearly it's not normal because folks would have been talking about it. The only other thing you could do is buy the Cnote crossover PCB's on ebay as those are pretty simple and hard to screw up. Then if you still have an issue it'd clearly be related to something in the chain.
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post #23 of 38 Old 06-01-2020, 11:39 AM - Thread Starter
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Quote:
Originally Posted by BassThatHz View Post
The short answer is: EQ can fix it. (Wideband 0.4Q -7db @ 16khz etc)
Or maybe try inverting the tweeter polarity, see if that makes it better/worse.

The longer solution would start by importing your REW sweeps for each raw-driver into XSim and plugging in the T/S parameters for each driver, and modeling the crossover.
See if that sims reality.

If not, then it is probably a complex interaction between the woofer and tweeter and crossover, a resonant feedback loop of induction/capacitance of the driver coils, magnetic field flux backEMF and crossover attributes of the same.
To model this properly you'd need a WT2 and import those charts into XSim, then you'd probably have to play with the crossover component values to get it right.
They probably didn't do that when they designed it. That would be my guess.

yeah, i can eq it out of existence, however what if someone is wrong? what if they did change something in the tweeter? what if they are shipping the wrong caps/resistors/inductors....this then seems like a problem worth fixing no? what if it's 100% my fault, certainly would like to know that to, but ignoring it across 3 completely independent speakers built wouldn't be giving back if there was an issue


Quote:
Originally Posted by _tk View Post
I'm not sure why you're spamming this on 3-4 different forums. Just call them. It could be a known issue already.

As I said, clearly it's not normal because folks would have been talking about it. The only other thing you could do is buy the Cnote crossover PCB's on ebay as those are pretty simple and hard to screw up. Then if you still have an issue it'd clearly be related to something in the chain.

casting a wide net, what does it matter to you how many forums and folks i look to for an answer? thanks for furthering the discussion



and yes, i called them today to get the process of investigation started on their end as well



Quote:
Originally Posted by jtl090179 View Post
i think its the website. your graphs dont show either. i added a link above to the results.

https://imgur.com/a/Bdh8pYq

thanks i was able to see them on imgur, doesnt look like you have what i have, but can you change your graph limits to adjust the DB scaling to something like 45db low end to 110db top end?
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post #24 of 38 Old 06-01-2020, 01:03 PM
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Here is a measurement of my older ND25FW-4 tweeters in a mock C-note baffle. With and without the C-note crossover on the tweeter. There is some lift to the top end with the crossover but obviously not nearly as much as you see in your measurements.

These tweeters are from I believe around 3-4 years ago, I have 4 of them and they all measure the same with that dip at the top end. So obviously there have been changes made the tweeters over the years. I had purchased those tweeters intending to use them in a design but haven't started that yet, looks like I may need to pick up a newer pair so I am not working with an out of date response.

When I last updated the crossovers on my Nexus designs I did so partially because some of the newer tweeters ND28 I purchased measured different then the older ones I had initially designed the speaker with. Unfortunately this seems to be a common occurrence with drivers from China.
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post #25 of 38 Old 06-01-2020, 01:04 PM
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[/QUOTE]
thanks i was able to see them on imgur, doesnt look like you have what i have, but can you change your graph limits to adjust the DB scaling to something like 45db low end to 110db top end?[/QUOTE]

Can you give me a list of how that is done?
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post #26 of 38 Old 06-01-2020, 01:09 PM
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In REW that is controlled by the Limits option at the top right. Also go into preferences and under the view tab uncheck "Use thick traces" which will result in the smaller more detailed trace lines.
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post #27 of 38 Old 06-01-2020, 04:55 PM
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Quote:
Originally Posted by mtg90 View Post
Here is a measurement of my older ND25FW-4 tweeters in a mock C-note baffle. With and without the C-note crossover on the tweeter. There is some lift to the top end with the crossover but obviously not nearly as much as you see in your measurements.

These tweeters are from I believe around 3-4 years ago, I have 4 of them and they all measure the same with that dip at the top end. So obviously there have been changes made the tweeters over the years. I had purchased those tweeters intending to use them in a design but haven't started that yet, looks like I may need to pick up a newer pair so I am not working with an out of date response.

When I last updated the crossovers on my Nexus designs I did so partially because some of the newer tweeters ND28 I purchased measured different then the older ones I had initially designed the speaker with. Unfortunately this seems to be a common occurrence with drivers from China.



https://imgur.com/a/7NJQ3en

I think this is what you were looking for.
Editops quoted wrong post/person but it wont let me change it now

Last edited by jtl090179; 06-01-2020 at 05:30 PM.
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post #28 of 38 Old 06-01-2020, 07:59 PM
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Quote:
Originally Posted by datrumole View Post





casting a wide net, what does it matter to you how many forums and folks i look to for an answer? thanks for furthering the discussion



and yes, i called them today to get the process of investigation started on their end as well

Just seems like a lot of effort for a pair of $100 speakers that one of two things are wrong: 1) either your crossover or 2) the components themselves. And one of those is out of anyone's control here.

Basically, until you find out what PE says or until they ship you some new components, everything else is just spinning your wheels.

The only one who can "further" anything at this point is PE. Not trying to be rude, but ultimately with their history of shipping components that weren't QC'd very well, that's where I'd hang my hat.
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post #29 of 38 Old 06-02-2020, 11:38 AM - Thread Starter
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Quote:
Originally Posted by jtl090179 View Post



https://imgur.com/a/7NJQ3en

I think this is what you were looking for.
Editops quoted wrong post/person but it wont let me change it now

awesome, thanks, looks like something changed for sure in the tweeter is my only conclusion


Quote:
Originally Posted by _tk View Post
Just seems like a lot of effort for a pair of $100 speakers that one of two things are wrong: 1) either your crossover or 2) the components themselves. And one of those is out of anyone's control here.

Basically, until you find out what PE says or until they ship you some new components, everything else is just spinning your wheels.

The only one who can "further" anything at this point is PE. Not trying to be rude, but ultimately with their history of shipping components that weren't QC'd very well, that's where I'd hang my hat.

thanks, while yes, it's only 100 bucks, i'm actually in for 300+additional equipment as i have a two pairs + a center being built. so it's more than just 100. and honestly, it could be $20, i wouldnt care. you have to remember, i simply came looking to see if i did something wrong in my build. validation would be that, no, they are working as intended. however there isnt a single response curve posted (yet) that shows mine are working 'as expected', so before i give them off to someone to enjoy, i'd like to make sure they are done correctly. so this isnt a big investment of time taking some measurements, and asking some questions. and if maybe something changed in the design, they should post that so people can appropriately temper and set their expectations.


Quote:
Originally Posted by mtg90 View Post
Here is a measurement of my older ND25FW-4 tweeters in a mock C-note baffle. With and without the C-note crossover on the tweeter. There is some lift to the top end with the crossover but obviously not nearly as much as you see in your measurements.

These tweeters are from I believe around 3-4 years ago, I have 4 of them and they all measure the same with that dip at the top end. So obviously there have been changes made the tweeters over the years. I had purchased those tweeters intending to use them in a design but haven't started that yet, looks like I may need to pick up a newer pair so I am not working with an out of date response.

When I last updated the crossovers on my Nexus designs I did so partially because some of the newer tweeters ND28 I purchased measured different then the older ones I had initially designed the speaker with. Unfortunately this seems to be a common occurrence with drivers from China.

based on my latest round of measurements, i'm going to have to conclude the tweeter did in fact change, so yes, i'd ensure to update your design and xover choices to account for it
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post #30 of 38 Old 06-02-2020, 12:35 PM - Thread Starter
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well, so here is my final post before i leave it in the capable hands of PE to determine the outcome

my only drawn conclusion is in fact that the tweeter design has changed

i think the smoking gun for my conclusion is the posted response of the c-note center channel, which upon further inspection, has the exact rise i'm seeing in my MT versions as well, HF rise starting at 7khz

below are the latest measurements, taken at 1m, with my denon 2310ci (not my tp22 which was exaggerating the lift) measured with a umik1

thanks for everyone who lent a helping hand. not sure if my findings may trigger a small update to the design or not to pull the response down, but i think PE should update the posted curves so people can be sure to compare it to the proper ones before they assume something is wrong
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