Help with the basics of Frequency Response Testing

[Verig]

Verig you ask why I ended up with the IMM not the UMM. Basically I found a youtube clip that talked through measurements with a smart phone and i thought it looked fun. REW looked 'complicated, scary and like something only professionals would use' so I didn't originally intend to use that. Now that I've got some guidance though I'll give it a try.

Sure. Most people don't see REW and just think "ok, that looks like fun".

From what I read, I thought that 'clarity' came from the mids so I was going to try and tune these to see if I can improve further - but I might simply be getting mixed up with the obviously more prominent bass response.

I find it useful to fool around with EQ. Play some music you know well and just take all the bass off. Then start lifting the levels. Ok, there's 80Hz... 70Hz... With a table setup you can begin from even much higher like 250Hz and see how it sounds.
You should notice quite quickly which areas are bloated. Not saying you should try to tune it by ear like this and leave it but it's a nice way to get acquinted with frequencies and how much clarity bass can rob.

 

[Xmall]

Thanks - will definitely play with the EQ.
I had a play over lunch - moved the speaker forward as suggested by @pma - I also popped some stiff foam underneath and boosted my levels (thanks @DWPress).

The difference! If its legitimate (and I've not moved out of an antinode or something) ... wow!

This was recorded 40cm from the speaker - mic level with the middle - using a boom stand (still using the phone unfortunately). There was a slight change in position with the whole setup being raised 10cm from the orange to the blue (due to the width of the foam)

Processed with 1/12 smoothing as recommended by @Keith_W

Orange Trace: Sony SS-NX1 left side only - sitting on wood - 10cm back from edge.
Blue Trace: Sony SS-NX1, left side only - sitting on foam - moved right up to edge.

SPL scale set 40 to 90.

So the obvious differences to my untrained ears/eyes:

1) Smoother sub-base response - assume this would be related to resonance of the wood at those real lows (though in reality, i have my sub crossover at 80hz so imagine this wont impact in real listening);
2) Elimination of that massive dip around 3-4Khz.

Noting I'm probably still doing plenty wrong (will keep working through it) - any thoughts on those initial results and whether my comments seem reasonable?


Out of interest, I also tested the Sony (same setup) against the little Klipsch and got the following:

Blue Trace: Sony SS-NX1, left side only - sitting on foam - moved right up to edge.
Green Trace: Klipsch Quintet, left side only - sitting on foam - right up to edge.

Any comment on, if paired with a sub - which speaker could be considered to be providing better sound?

They are both pretty messy, but if I were take a stab, the Sony is probably a better response 40hz - 2khz the Klipsch is much more even 2Khz to 16khz (subject to how much reflection is screwing with my results!)?

Thanks again everyone for the great input - I imagine I would have put this in the too-hard basket by now. Appreciative of the support.

 

[Verig]

In this case I'm not strictly pointing at the transition frequency by 250Hz. When speakers are not placed on stands but on table the proximity of a large surface doesn't play nice with upper bass, let's say around 160-200Hz or so. There's a problem within a problem so to say. (But then again if you're not considering stands it doesn't matter, it's just part of the whole then.)

As the article says, 250Hz is just a rule of thumb but for practical purposes in the beginning it doesn't matter that much. Just keep in mind that up to 300Hz it's very much your room playing tricks. The other gents here will provide you with all the exactness in the world. I'm just chiming in that don't worry too much, worrying sometimes leads to making too many high Q adjustments and trying to fix things in the wrong way. Start broadly and from the most obvious problems.

I suggest you don't try to touch your mids before you have the lows sorted out. Most speakers are pretty ok in the mids and variations in FR go easily within matters of taste. Bass may be a huge problem with 6-20dB swings but it's kind of easy to adjust until "good enough" for enjoyable listening. Mids touch the speaker itself so to say and even minor adjustments may have surprising effects. Unless there's a very clear problem area it's very much likely that the adjustments you made are not the right ones.

Have fun!

 

[kemmler3D]

Thanks - will definitely play with the EQ.
I had a play over lunch - moved the speaker forward as suggested by @pma - I also popped some stiff foam underneath and boosted my levels (thanks @DWPress).

The difference! If its legitimate (and I've not moved out of an antinode or something) ... wow!

This was recorded 40cm from the speaker - mic level with the middle - using a boom stand (still using the phone unfortunately). There was a slight change in position with the whole setup being raised 10cm from the orange to the blue (due to the width of the foam)

Processed with 1/12 smoothing as recommended by @Keith_W

Orange Trace: Sony SS-NX1 left side only - sitting on wood - 10cm back from edge.
Blue Trace: Sony SS-NX1, left side only - sitting on foam - moved right up to edge.

SPL scale set 40 to 90.

View attachment 385251

So the obvious differences to my untrained ears/eyes:

1) Smoother sub-base response - assume this would be related to resonance of the wood at those real lows (though in reality, i have my sub crossover at 80hz so imagine this wont impact in real listening);
2) Elimination of that massive dip around 3-4Khz.

Noting I'm probably still doing plenty wrong (will keep working through it) - any thoughts on those initial results and whether my comments seem reasonable?


Out of interest, I also tested the Sony (same setup) against the little Klipsch and got the following:

Blue Trace: Sony SS-NX1, left side only - sitting on foam - moved right up to edge.
Green Trace: Klipsch Quintet, left side only - sitting on foam - right up to edge.

View attachment 385255

Any comment on, if paired with a sub - which speaker could be considered to be providing better sound?

They are both pretty messy, but if I were take a stab, the Sony is probably a better response 40hz - 2khz the Klipsch is much more even 2Khz to 16khz (subject to how much reflection is screwing with my results!)?

Thanks again everyone for the great input - I imagine I would have put this in the too-hard basket by now. Appreciative of the support.

I think your interpretations are pretty reasonable here. The klipsch looks surprisingly good in the upper mids / lower treble, but the sony is clobbering it in terms of bass. Moving the sony closer to the edge of the table was also a surprisingly big improvement.

 

[Verig]

You can take care of that bump over 100Hz, should make some messy boominess go away. That huge dip above 10kHz may be related to mic position? I shouldn't think Sony tweeter is actually doing that.

Very good results to illustrate how much difference even small changes in speaker placement can make.

Klipsch looks surprisingly good apart from it having no bass. That added to the 100Hz+ bump and dip must make the sound pretty awful even when the rest is quite balanced.

I'd like to see measurements with the sub. Some real energy to the lows to wake up the room.

 

[Keith_W]

One thing I noticed going from my Klipsch Quintet, to the Sony SS-NX1 - was much better clarity in instruments. I.e. with the Klipsch (tiny satellite) it felt difficult to follow a tune from a specific instrument - where with the Sony it felt like you could hear each and every one clearly and track them.

Clarity will be due to something else which you are not looking at right now. Broadly speaking, you can think of speaker measurements in terms of time and amplitude. So far you have been looking at the amplitude response - which frequencies are louder relative to another. Clarity is a time related phenomenon, because it is due to smearing. All sorts of things can smear the sound - your room (early reflections), speaker and driver resonances and breakup modes, phase and time alignment issues, ringing caused by DSP, etc. The answer will be found in all the "time" curves - phase, group delay, step response, spectrogram, etc. It is another huge topic of discussion and I advise you to tackle that topic when you are ready. Diagnosing why A sounds clearer than B is not an easy task.

On Schroder - how much does the '250Hz' rule of thumb vary by room size?

The calculation is:

In your case, the room volume is the volume of all the individual spaces which are open to the listening area, all added up. The T30 can be found in REW's "RT60" tab. Note that T20, T30, and RT60 are all meant to be the same thing. RT60 is "reverberation time for sound to decay by 60dB". But this has little application in small rooms (small = not a concert hall) because reverberant fields are not formed below certain wavelengths, and the noise floor is often quite high - typically about 45dB. You would need to measure at 105dB minimum to capture the RT60. So we use T20/T30 instead - this is the time for sound to decay by 20dB or 30dB, then extrapolated to 60dB.

The Schroder frequency is an approximation anyway. Don't get too hung up about calculating the exact number. You only need a "ball park" number. For example, in my room the calculated Schroder frequency is 107Hz, which means the transition zone ends at 4x - or 428Hz. I choose to correct up to 450Hz because I like round numbers.

I will give this a shot as well, and see how it differs. How long a sweep should I be running (30 seconds, 2 minutes etc)? I imagine as I sweep, if I am hitting nodes/antinodes It could give a slightly different result each time?

The purpose of running a long sweep is to improve the signal-noise ratio. For example, a 45 second sweep provides 90dB of noise rejection. You may or may not need a high SNR depending on what the measurement is for.

Keith, curious how you guessed my general location? Was it timing of the posts? I'm well further South of you, in Sunny warm Hobart

Because I am very observant

 

[tmtomh]

+1 - measure how you listen, unless you plan to EQ above Schroder for some reason, in which case reflections could throw things off even worse.

Ah, that's a good additional point: most surfaces and items small enough to consider moving out of a room for measurement purposes are also unlikely to create reflections at frequencies below Schröder.

Interestingly, I've been doing some GLM measurements of my 8351b's recently, as I've experimented with modest changes in toe-in, speaker tilt, and listening distance. I found the measured response from the listening position to be surprisingly consistent through all these changes. Noticeable and certainly audible differences to be sure, but still nothing radical.

As part of this I was a little dismayed to see how choppy the measured response looked through the midrange and treble, from about 2kHz up.

My measurement technique had been to hold the mic in my hand, at ear level, while seated in my usual listening position, and then lean back a bit so that the mic's distance from the speakers would be more or less exactly the distance my ears are when I'm sitting normally.

Just for fun, I changed to a tripod, using a level to position the mic where it would be if I were holding it. The measurements were extremely similar, and identical in the bass region. The one major difference was that the entire mid and treble range looked a good deal smoother - fewer ups and downs, and remaining ups and downs were of less magnitude.

From this I conclude that my face and body have an absorptive and reflective effect; there's nothing I can do about it; and my brain must be accustomed to it since I spend my entire life hearing everything that way.

So I can see how psychoacoustic smoothing might hide important issues in the bass region. But in the upper mids and treble I'm not convinced that measured choppiness from known-linear speakers in an average room actually translates to what we hear.

 

[Verig]

@Xmall Here's a pic from a bit difficult room without looking for sub placement or anything. XO at 80Hz. Welcome to the rollercoaster.

 

[tmtomh]

@Xmall Here's a pic from a bit difficult room without looking for sub placement or anything. XO at 80Hz. Welcome to the rollercoaster.

View attachment 385348

Yep. I use no subs and my uncorrected response is somewhat similar. I have fewer dips and they aren't so deep, but the overall picture of peaks and valleys in the uncorrected response is definitely reminiscent of what I've measured.

 

[Xmall]

...Clarity is a time related phenomenon...

And here I thought I had a shred of hope of actually getting my head around all this stuff

Given what I've seen so far I'll park the room tuning for now - and play with speakers, positions and variables to get a better feel for impacts . I should probably start by making a decent speaker stand based on results a couple of posts back - then i'll get back to attempting some room tuning.

@Xmall Here's a pic from a bit difficult room

That is surprisingly choppy! Is the grey curve a target? Assume it looks too smooth to be an adjusted curve?

I'd like to see measurements with the sub. Some real energy to the lows to wake up the room.

I did manage to get some readings yesterday. This was back to my 'default' setup (speakers badly placed, sitting back on the TV cabinet etc).

Used a boom this time in the primary listening position.

Green Trace: Full Setup, boom mic at listening position, furniture in place - Audyssey EQ Off (I think the sub crossover might be 100hz)
Purple Trace: Full Setup, boom mic at listening position, furniture in pace -Audyssey EQ ON (I think the sub crossover might be 60hz as set by Audyssey)

SPL Scale 40-90 dB

I'll do another one, matching the two sub XS points (or at least confirm where they are currently at!). All in all, I would like to think that doesn't actually look to bad? In the Aydyssey case, other than the big dip around 210hz, it seems to be sitting within 2-3dB if i draw in a best fit curve - upto about 4k (Then it goes wonky!). Let me know what you think

I also did a disassembly of the Sony speaker today - I remember i didn't find much info on them last time (except for another forum post) - will upload photos measurements and the Crossover schematic (I traced it with a multimeter) in case anyone is interested


One thing i noticed re. future tuning, is at current I can only adjust EQ within 9 bins, 62hz, 125, 250, 500, 1Khz, 2, 4, 8, 16. Is this sufficient to actually make any meaningful improvement?

The next things i want to do, is setup speakers facing out the open doors, try and reduce early reflections as much as possible - and probably test the off-axis response of a few as well. Weekend is coming, (Three busy kids in the house) so I might not be able to post any more until early next week but i'll try!

 

[kemmler3D]

One thing i noticed re. future tuning, is at current I can only adjust EQ within 9 bins, 62hz, 125, 250, 500, 1Khz, 2, 4, 8, 16. Is this sufficient to actually make any meaningful improvement?

Generally no, because the dips / peaks you want to fix with EQ are narrow and rarely sit exactly on one of those frequencies. What you need is called "PEQ" or "Parametric Equalization" which simply means you get to pick the frequency, gain, and width of each filter, instead of just the gain.

While this probably sounds a bit more complex (and it is more complex) the good news is it's being built into a lot more devices nowadays, including some very affordable boxes from WiiM and some not-horribly-expensive boxes from MiniDSP. You can also DIY it in various ways.

I can tell you it's well worth the effort of setting it up. You would think fixing the sound from 20-300hz or so would be pretty limited in how it sounds, but it seems to dramatically improve the overall sound when you do it. I think part of it is that when you have big peaks in the bass popping out, they tend to mask details in upper frequencies. IMO the net effect is that the whole experience improves, not just the bass.

Adyssey is actually probably already doing a lot of this for you, but if you want to go further on the EQ / DSP front you're going to want to figure out PEQ.

 

[dualazmak]

I also did a disassembly of the Sony speaker today - I remember i didn't find much info on them last time (except for another forum post) - will upload photos measurements and the Crossover schematic (I traced it with a multimeter) in case anyone is interested

Yes, I am very much interested in!! I am looking forward to seeing the photo of the passive XO network and your measurement data on each of the network components as well as the circuit schematic diagram.

By the way, do you have further interests/plan to make your Sony SP "fully active" by eliminating/bypassing the passive XO network and connect each of the SP drivers to multiple dedicated amplifiers, just like in my setup (ref. here)? You do not need powerful amp for tweeters, as you may easily agree.

Even though you need careful protection mechanisms and practices, the elimination of passive XO network would often lead you to amazingly improved new sound world if everything would be carefully setup properly...

 

[Verig]

That is surprisingly choppy! Is the grey curve a target? Assume it looks too smooth to be an adjusted curve?

Ah, yes, the grey is Dirac automation target curve in default position to fiddle around with. I just didn't have a better pic at hand.

View attachment 385403

I'll do another one, matching the two sub XS points (or at least confirm where they are currently at!). All in all, I would like to think that doesn't actually look to bad? In the Aydyssey case, other than the big dip around 210hz, it seems to be sitting within 2-3dB if i draw in a best fit curve - upto about 4k (Then it goes wonky!). Let me know what you think

That's not bad at all. Considering you don't have stands that's very nice.
I'm not completely sure what Audyssey is doing in the 4-8kHz range though. That's quite a lift in 6-7kHz. But this is something that needs listening and comparing whether you want to take it down a bit.

I also did a disassembly of the Sony speaker today - I remember i didn't find much info on them last time (except for another forum post) - will upload photos measurements and the Crossover schematic (I traced it with a multimeter) in case anyone is interested

People here are mostly interested in disassemblies like cats react opening a tuna can. Let's have it.

One thing i noticed re. future tuning, is at current I can only adjust EQ within 9 bins, 62hz, 125, 250, 500, 1Khz, 2, 4, 8, 16. Is this sufficient to actually make any meaningful improvement?

Take a look at my measurement. 125 and 250Hz would be spot on and while 62 doesn't exactly match what I'd want I'm sure the adjustment is wide enough to help considerably. These classic bins can be pretty useful - especially when Audyssey automation takes care of the worst parts first - but even without that you don't really need much to make a considerable difference.
But as Kemmler3D says, they are not what we really want. We want to be a bit more precise. And we don't have anything that would quite fit your 6-7Khz area.

All in all, looking good where this is going!

 

[dualazmak]

People here are mostly interested in disassemblies like cats react opening a tuna can. Let's have it.

Yes, I am one of the cats; let's smell and taste it very soon!

 

[Verig]

If you wonder why the default curve has +3,5dB applied I think because people tend to enjoy their bass a bit hot. I've seen enough complaints about room correction taking away too much so this was applied at least to NAD integrated version.

Yep. I use no subs and my uncorrected response is somewhat similar. I have fewer dips and they aren't so deep, but the overall picture of peaks and valleys in the uncorrected response is definitely reminiscent of what I've measured.

Yes, very likely. This is a very "normal" living room with stone walls. Not the first place where I measure something quite similar.

 

[Xmall]

Yes, I am one of the cats; let's smell and taste it very soon!

Ha ha. Love it. The tuna can is wide open folks, I started a new thread as its a fair post - keen to hear thoughts, feedback, requests for more info.

Sony SS-NX1 Speaker disassembly - Late 90's audiophile mini system speakers

Hi All, I recently picked up a pair of Sony SS-NX1's from the local tip shop - was not able to find a lot of information online - so after some encouragement on another thread, thought I would post what i know from my tinkering :) Photo of the speakers and my setup below: (Noting there are...

www.audiosciencereview.com

I'll come back on some of the other questions and answers in this thread shortly - I've not had time to read of everything as I've been working on the Sony writeup


More testing to come shortly.

 

[dualazmak]

looks the linked thread is missing...

 

[Xmall]

I think it might have taken a moment to be approved. Looks like its up and running now

Sony SS-NX1 Speaker disassembly - Late 90's audiophile mini system speakers

Hi All, I recently picked up a pair of Sony SS-NX1's from the local tip shop - was not able to find a lot of information online - so after some encouragement on another thread, thought I would post what i know from my tinkering :) Photo of the speakers and my setup below: (Noting there are...

www.audiosciencereview.com

 

[Xmall]

I can tell you it's well worth the effort of setting it up. You would think fixing the sound from 20-300hz or so would be pretty limited in how it sounds, but it seems to dramatically improve the overall sound when you do it. I think part of it is that when you have big peaks in the bass popping out, they tend to mask details in upper frequencies. IMO the net effect is that the whole experience improves, not just the bass.

Adyssey is actually probably already doing a lot of this for you, but if you want to go further on the EQ / DSP front you're going to want to figure out PEQ.

Thanks @kemmler3D - I am familiar with parametric equalisation, my electric piano has that function and I've been tweaking that to get some good piano tones.

From what i can see, it looks like something like this 'should' have parametric EQ: https://www.selby.com.au/wiim-pro-w...yTsSR3_dj-LZcn7cCmQaAhFhEALw_wcB#gad_source=1

Doesn't mention it in the add but there is a how to guide on the WiiM site: https://www.blog.wiimhome.com/post/how-to-use-parametric-eq-a-comprehensive-guide

I note the one i linked is the 'Aus edition' (and lets face it - companies love branding things the same then selling an inferior version over here - so i'll need to check that it actually allows the parametric EQ.

Something like that would actually be pretty handy, as my amp only has airplay (and I'm an android user).

Ah, yes, the grey is Dirac automation target curve in default position to fiddle around with. I just didn't have a better pic at hand.

Neat - I presume its only a target between the 20Hz and 500 and something Hz bands? I was wondering about the 'wiggles' your target curve had below 20 but then - thats below human hearing so I guess its immaterial.

By the way, do you have further interests/plan to make your Sony SP "fully active" by eliminating/bypassing the passive XO network and connect each of the SP drivers to multiple dedicated amplifiers, just like in my setup (ref. here)? You do not need powerful amp for tweeters, as you may easily agree.

I would love to delve into this sort of thing - but unfortunately being the living room and with three kids who just LOVE hitting buttons and twirling knobs, I just don't think it would be a reality for me.

I have heard of active cross-overs - is what you are doing with the amps, effectively building an active crossover which you have full control over?

 

[Xmall]

Onto some more measurements - I did manage to get a few readings done - I've thought through a couple of explanations but would love to get the forums input.

So the first, was having a crack at testing room reflections with doors open/closed.

For this one, I moved the couch sat the speaker at the front of the coffee table (so there was nothing between it and the double door, except the phone, microphone and boom stand). The door is 4.6m wide, with a 2.3m opening (double slider) - speaker was positioned facing about the centre of the doors. Marked up on the photo below (except all the washing, chairs etc moved):

The mic was ~ 550mm from the speaker, then the door was about 4.5m behind that. With most of the front wall being glass - I imagine this will have a fair impact on what frequencies are reflected vs which travel through?

Anyway - results are below.

Green: Doors OPEN case
Purple: Doors Closed Case

I have to admit - I kind of expected the opposite here. I suspect perhaps the higher low base may have been wind interference - or general noise outside? As I cant see how the base would increase if more sound was reflected?

The other thing that surprised me, as other than that base region... we are not really seeing any real change? With the earlier discussion on early reflections (@Keith_W @Verig) - i was wondering, am i just not picking up the reflections here, because the peak is picked up after a half meter - but the reflections have to go 9m - then since they are not early they are not being detected?

Probably need to learn how to look at the time side of things here - but not sure if i have the tools for that?

Second test, I did a crude on/off axis test on both the tiny Klipsch satellite and the bigger Sony. Results as follows:

I've probably Ballsed this up - as I did it by setting the mic 550mm from the speaker - then moving sideways in 200mm increments (increasing distance away each time).

But for the sake of scientific discussion - first my 'reference' Klipsch speakers:

Orange: On Axis (550mm)
Red: Off Axis ~ 20 degrees
Green: Off Axis ~ 36 degrees
Blue: Off Axis ~ 48 degrees

Seeing not much change in the base - through to about 12 dB at 10KHz.

And the Sony Speakers:

Light Blue: On Axis (550mm)
Purple: Off Axis ~ 20 degrees
Dark Blue: Off Axis ~ 36 degrees
Magenta: Off Axis ~ 48 degrees

Similar sort of change in the base - but a much smaller reduction in the treble.

I'm guessing that the 'tighter' spread between the two speakers could be:

1) Simply the Klipsch being a MUCH smaller speaker outputting considerably less energy;
2) The Sony speakers have larger domes - so you get more 'throw' of sound? (I'm guessing there is probably a proper term for this.... but i dont know it!.

I do find it interesting that generally the peaks and troughs (I.e. 200 , 250, and 7K) seem to have a larger spread of sound energy than other areas. Would be really interested in any theories on why this might be the case?


I'm interested in playing a bit further with time and reflections. I found a 'spectogram' and 'LeQ' function which look like they Might(?) allow some measurement with time. WIll read up on those and maybe have a play through the week.

Thanks again all for the great input and support thus far