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Should I replace my KEF 105.1's?

YSC

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OK - interesting discussion, thanks everyone for their input. There seems to be a majority opinion that I should a) measure to make sure they are working correctly b) if not, possibly service the crossovers c) look at getting better amplification.

- I will definitely look into the suggestions about getting a calibrated mic and appropriate software and measuring the 105's response in my room. Is this the mic you'd all recommend? https://www.minidsp.com/products/acoustic-measurement/umik-1?lang=en
- I just found the REW software home page so will look at that. looks like it will run on my Mac laptop so that's good.
- I can't see or feel any damage to the drivers - just removed the grills on one speaker, there is no friction when I very gently move the cones on the woofer and mid-range. and no mysterious fluids dripping out :). I'm scared to mess with the tweeters but they look fine through the grills.
- Assuming I find a problem that could be attributed to the crossovers.... I'm not sure what is involved in opening up the KEFs to get to them, without damaging the cabinets. If anyone has done this or knows someone who has done this, and could provide guidance, please let me know. Or if anyone knows a shop in Los Angeles that would re-cap the crossovers for a reasonable cost, let me know...
- I will look into replacing my amp with something with more power. I actually have a Nakamich 620 power amp that's been sitting idle for many years. It is 100wpc but perhaps better quality than my Sony STR-DN1040? I have no idea. I also have the matching 630 tuner/preamp but it needs servicing (noisy potentiometers). maybe just some tuner spray but that's a whole project to figure out how to take it apart (and put it back together). Though I think I have the service manual somewhere.
- If there are major problems with the room acoustics then it seems there is a whole new adventure required to look into the world of equalizers and associated equipment...

Don
I think so, for checking I think you will want a professional restorer shop to do the inspection and checking of crossover, maybe driver surround (the ring of foam/rubber along the edge of the cone) to make sure you don't mess up anything, for amps I personally think that any current Hypex based class D amps should be way more than enough for your need
 

Doodski

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@Don105 here is a link for pics of the crossover. There are speaker repair/rebuilding shops all over North America and one of those should be able to manage whatever you need done if you want somebody to do that for you.
105 - 1.jpg

105 - 2.jpg
 
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Don105

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Thanks for this! I've just ordered a Umik-1 mic. This ships from Hong Kong so not sure when it will arrive. Will report results once its arrived and I've figured out how to set everything up and run some tests...
 
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Don105

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OK - with the caveat that I have almost no idea what I'm doing with REW and much of the output and acronyms are mysterious for me...
I received the Umik-1 mic today (that was fast!) and followed a blog post to set up REW on a MacBook.
I proceeded to configure the settings (I think) for 2 channels, 48khz, and ran a couple of tests from 20-20khz with the left and then the right speaker in my listening room. I averaged the two runs for each speaker and saved the .mdat files. I did download and use the calibration file for my Umik-1.
The mic was positioned 4 or 5 feet in front of each speaker for the tests.

I added a ".txt" extension to the REW .mdat filenames so i could post them here. Perhaps some knowledgeable person(s) can review these and provide input as to what they might indicate, tell me what i'm doing wrong, suggest additional tests or setup changes, etc.

thanks
Don
 
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YSC

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OK - with the caveat that I have almost no idea what I'm doing with REW and much of the output and acronyms are mysterious for me...
I received the Umik-1 mic today (that was fast!) and followed a blog post to set up REW on a MacBook.
I proceeded to configure the settings (I think) for 2 channels, 48khz, and ran a couple of tests from 20-20khz with the left and then the right speaker in my listening room. I averaged the two runs for each speaker and saved the .mdat files. I did download and use the calibration file for my Umik-1.
The mic was positioned 4 or 5 feet in front of each speaker for the tests.

I added a ".txt" extension to the REW .mdat filenames so i could post them here. Perhaps some knowledgeable person(s) can review these and provide input as to what they might indicate, tell me what i'm doing wrong, suggest additional tests or setup changes, etc.

thanks
Don
I think this approach have less of a meaning, I would say use a tripod and fix the mic at your listening position, pointing to the direction your head usually point to, then run 3 measurements, L, R and L+R to see their response in room
 

Chromatischism

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If this is for a speaker restoration, I would do nearfield measurements of the drivers before and after.
 
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Don105

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Thanks, will check out MMM.
But if someone familiar with REW charts could take a look at the ones I posted above I’d be grateful. My main question is about the really “noisy” response in the mid and high frequencies. Is this normal? Or did I do something wrong configuring REW? Or do I have a problem with my amp, speakers or room?

thanks
 

NTK

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Not seeing any attachments in your previous posts. You can also upload zipped archives.
 
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Don105

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@NTK Odd, I could swear I attached them, sorry about that. Let me try again with a zip archive. As noted earlier, I did 2 measurements 20-20khz for each speaker and averaged them, with the mic about 4-5 feet in front of each speaker, around ear level when seated.
 

Attachments

  • KEF105-L_R.zip
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NTK

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Your measurements don't look too different from the one shown in this post.
https://www.audiosciencereview.com/...-your-in-room-measurements.13540/#post-408430

The jaggedness of the response is due to comb filtering (constructive and destructive interferences) from the various reflections from all the objects in the room, and they vary a lot and quickly from location to location at the higher frequencies. After applying 1/12 octave smoothing, your measurements become:
REW.PNG


MMM will even out a lot of the combing filtering effects. And with more averages from longer scans, it should also provide more repeatable and smoother response.
 
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Don105

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Thanks for the explanation, @NTK! I will check out the MMM tutorial, and take additional measurements. REW newbie question: how do I do a longer scan? These seem to default to 5.5 seconds.
 

NTK

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I myself is a REW novice, and am going to quickly display my lack of knowledge :). I am usually pretty good at getting stuff to do something. But not so good at get stuff to do something useful :rolleyes:

I think the total sweep time is determined by the combination of length and number of sweeps.

REW.PNG
 
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Don105

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OK - ran some additional tests.

I used the moving mic technique for both a pair of multi-sweep tests and a pair of RTA pink noise tests. i've attached a zip with the 4 result files, and screenshots of my setup. for the generator, i used "Pink Noise" and selected Full Range. for the sweeps i ran 8 cycles at 512k, 20-20khz. for the RTA's i ran over 100 iterations. i applied 1/24 smoothing.

I had the Midi setup for 2 channel stereo, and i set my receiver to "pure direct", though it seems that there was still output to the sub. i just turned it off for 2 of the tests.

I don't understand the results tbh. Must be doing something wrong as a I see a major discrepancy in the bass response between the two tests. There is also a pretty steep falloff in the treble above around 12khz. I just double-checked that the tweeters are working :). could my crossovers be shot?

If anyone familiar with this tool can review these files and help interpret these results, please don't be shy :).

thanks
Don
 

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  • KEF 105 take 2.zip
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Chromatischism

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Well the measurement is a little on the quiet side. Shoot for 75-85 dB in-room.

The tweeter response is a little chaotic. Above 1-2 kHz the MM technique should really smooth that out, but for some reason it isn't.

Can you do a nearfield of the tweeter? We need to see that. Do you have a mic stand? Point the mic directly at the center of the tweeter at 0 degrees. Put it within .25" of the tweeter (don't put it that close to a woofer as it could smack it). Use the 0° calibration file and a lower measurement level since it will appear much louder. Do a normal measurement sweep from 10-20,000 so we can keep the same scale.

And what is going on below 500 Hz? Assuming the woofer connected (is it?), maybe this wasn't a full-range measurement. Use Pink Periodic, and make sure Full Range is selected.

EDIT: Your files are mislabled. The ones that say "moving mic" appear to not be averages, but standard sweeps. The ones labeled "RTA" are your moving mic averages. It still doesn't explain why your sweeps don't have anything below 400 Hz.

Here are the RTA settings I use:

1627161675356.png


After stopping the RTA capture, click the "Current" button to send that measurement to the main window.
 
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Don105

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maybe i'm running a different version of REW? I'm on 5.19. See screenshot below with the RTA settings I used. I'll change the mode, FFT length and window as you suggested and try again. I will also do a sweep of the tweeter as suggested. For the noise generator, do you mean "Pink PN"? I used "Pink Noise" in the RTA runs.

your help is very much appreciated!

RTA settings.png
 

Chromatischism

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I would update to the latest. John has made a ton of changes since 5.19. We're now comically on 5.20 release candidate 12. I don't know why he didn't release 5.20 without all the new features. IMO new features would have taken him past 5.30 by now.

https://www.avnirvana.com/resources/
 

YSC

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Actually the measurements looked to my eyes very well behaved! I don't think upgrading would bring you any real benefit beside the "I got my new toy" joy
 
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