• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Dr. Klaus Heinz of HEDD Audio (ex ADAM Audio) - measuring speakers, in particular speaker dynamics

Krunok

Major Contributor
Joined
Mar 25, 2018
Messages
2,824
Likes
1,307
Location
Zg, Cro
  • Use digital XO to crossover to sub(s) at a point that makes sense for your mains and in-between room modes. In my case, the big JBL’s easily play to 40 Hz, but I have a room mode there, so I digital XO’d at 45 Hz to my subs between two modes. Don’t blindly follow the XO at 80 Hz and leave mains capability on the table. Find the measured F3 of your mains in the room and hand-off or offload to subs around that point.
Speaking of that, if I understood correctly when you were doing that experiment with LS50 and the subs you set XO point to 70Hz, correct? Wouldn't it be better that you have set it higher to offload LS50 a little bit more than that?
 

Krunok

Major Contributor
Joined
Mar 25, 2018
Messages
2,824
Likes
1,307
Location
Zg, Cro
@mitchco is it possible to use your uncorrected impulse response and test it with other (open source) DSP's? I am curious to what extend this is achievable with freely available software, and where the difference will be most noticeable.
It is possible, but without measuring the results you won't be able to make any comparison. Audiolense and Accurate are among the best money can buy. If you want to see how DRC works you can start with free software in which case I would recommend DRC-FIR as it does quite a decent job.
 

Arnandsway

Active Member
Joined
Sep 13, 2018
Messages
150
Likes
102
Actually, no. FR can, and indeed is, calculated from IR, but you can't possibly conclude anything about FR by looking at step response. This almost perfect step response actually means that phase is linear.

Take, for example, step response of Performa3 F208:

View attachment 27615

As you can see, not only that it is nowhere as perfect as @mitcho 's but it is totally time unaligned. First peak is from tweeter, second from midwoofer and third from woofer(s). However, this speaker has very linear FR and is considered to be one of the best (if not the best) speaker in it's price range.

So, the answer to your question is this: IR response contains both, frequency and phase information so everything is derived from it - frequency resposne, phase responsee, step response, GD, distortion, .. But looking at step response you can't conclude anything about FR. As step response is happening in time domain you can conclude only about phase (time coherence) of the speaker drivers. Let's also not forget that, as mighty as step response looks, it's significance on SQ is actually small to none. It is the FR that matters, esepecially when measured not only on-axis but on a wide range of horizontal and vertical angles, as is shown on famous spinorama graphs.

But, yes, @mitchco speakers indeed have extremely linear FR. :)
This is quite different than what @dc655321 is saying. I understand that because of time delay between the drivers that the impulses will not be on the same spot.
You say nothing to be concluded from an impulse response. That seems odd to me because FR can be derived from it.

As you showed your impulse response, which didn't look quite "textbook", might this be the result of alternative speaker designs such as dipoles, cardioid etc.?
 

Krunok

Major Contributor
Joined
Mar 25, 2018
Messages
2,824
Likes
1,307
Location
Zg, Cro
This is quite different than what @dc655321 is saying. I understand that because of time delay between the drivers that the impulses will not be on the same spot. But the rest is quite the opposite. This confuses me.
You mean this part?

And because of this almost perfect impulse response, means your FR is extremely flat too?
Indeed.

Well, first of all Mitch showed step response, not impulse response. Besides that, I am not aware of any way you can conclude how FR would look by looking at step response. The only thing I know you can conclude from step response is about how speaker drivers are time aligned which is part of the phase response.
I wouldn't of course mind to be corrected, the only thing that matters is that we learn something new. :)
 

Arnandsway

Active Member
Joined
Sep 13, 2018
Messages
150
Likes
102
You mean this part?

And because of this almost perfect impulse response, means your FR is extremely flat too?
Indeed.

Well, first of all Mitch showed step response, not impulse response. Besides that, I am not aware of any way you can conclude how FR would look by looking at step response. The only thing I know you can conclude from step response is about how speaker drivers are time aligned which is part of the phase response.
I wouldn't of course mind to be corrected, the only thing that matters is that we learn something new. :)
I edited my post just before you replied :).

It might be that I'm confusing step response with impulse response (if they're not the same)..
 

Krunok

Major Contributor
Joined
Mar 25, 2018
Messages
2,824
Likes
1,307
Location
Zg, Cro
Let's try this way: if you would want to time align drivers of F208 speaker, which step response I posted above, you would have to correct it's phase characteristics. Once you do that, assuming you did a good job, step response would look similar to Mitch's step responsee. Frequency response wouldn't change in that process as you would be changing only the phase.
 

Krunok

Major Contributor
Joined
Mar 25, 2018
Messages
2,824
Likes
1,307
Location
Zg, Cro
It might be that I'm confusing step response with impulse response (if they're not the same)..

Here they are, both shown on the same graph. From IR you can't conclude much, you can only see when reflections are occuring. For that reason you can integrate (accumulate) IR over time to get step response from which you can than see when each of speaker's drivers jumped into action. But this all happening in time domain, so phase related, not frequency.

Capture.JPG
 

Krunok

Major Contributor
Joined
Mar 25, 2018
Messages
2,824
Likes
1,307
Location
Zg, Cro
Same thing, but for right speaker. This one is looking better as I had to make some changes in phase of the left speaker to compensate cancellation at some low frequencies when both speakers are playing. :)

CaptureR.JPG
 
Last edited:

RayDunzl

Major Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
6,803
Likes
2,900
Location
Riverview, FL

Krunok

Major Contributor
Joined
Mar 25, 2018
Messages
2,824
Likes
1,307
Location
Zg, Cro
Two years ago I questioned "How can Impulse and Step Response be accurately calculated from a Swept Test Tone when it has no step or impulse visible, just what sounds like a smoothly ascending frequency?"

For grins, here's the result of the little experiment I came up with...

https://www.audiosciencereview.com/forum/index.php?threads/impulse-response.1765/#post-44352

and

https://www.audiosciencereview.com/forum/index.php?threads/impulse-response.1765/#post-44440
I was about to say "you nailed it", but then it occured to me that "you spooned it" might be a better choice of words. :D
 

RayDunzl

Major Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
6,803
Likes
2,900
Location
Riverview, FL
A couple of days ago, I had REW create a 5Hz to 20kHz WAV file of its Masurement Sweep tone and looked at it in Audacity.

There's the Acoustic Timing Reference at the start of the left track, and the swept sine in both tracks.

1560409413404.png


@JohnPM

Not sure what I'm seeing there in the Spectral Analysis...

Measurement artifact or stepped tone?
 

RayDunzl

Major Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
6,803
Likes
2,900
Location
Riverview, FL
I was about to say "you nailed it", but then it occured to me that "you spooned it" might be a better choice of words.
I have some nails I could try.

1560409798788.png
 

Soniclife

Major Contributor
Joined
Apr 13, 2017
Messages
1,239
Likes
747
Location
UK
I have gone very deep on the audio DSP rabbit hole and one DSP stands above them all for ease of use plus the capability that one can get a pretty good, towards almost perfect correction in less than an hour.
For those of us who peeked over the edge into the very deep hole, but don't fancy the long trip to the bottom, what's the easy solution called?
 

Daverz

Active Member
Joined
Mar 17, 2019
Messages
179
Likes
89
A couple of days ago, I had REW create a 5Hz to 20kHz WAV file of its Masurement Sweep tone and looked at it in Audacity.

There's the Acoustic Timing Reference at the start of the left track, and the swept sine in both tracks.

View attachment 27619

@JohnPM

Not sure what I'm seeing there in the Spectral Analysis...

Measurement artifact or stepped tone?
That, I believe, is the "picket fence effect".
 

andreasmaaan

Major Contributor
Patreon Donor
Joined
Jun 19, 2018
Messages
3,306
Likes
2,421
Just to change the topic somewhat, and perhaps @KSTR would care to weigh in on this as one of the former engineers at HEDD, but it seems to me that by using minimum phase filters in the speaker and then linearising the signal as a whole via DSP, one creates a situation in which there is no DIRAC impulse at any position in front of the speakers.

Or, to put it another way, since phase linearisation must create pre-ringing, and since this is applied to the signal as a whole prior to the speaker's internal crossover, there is no position on axis at which the crossover filters' pre-ringing cancel each other to create a ringing-free output. The linearisation filter's pre-ringing is equal (and maximum) at every location in space.

This would seem a suboptimal approach to me (again, no comment on audibility per se as I'm not aware of much research either way on this matter).
 

Krunok

Major Contributor
Joined
Mar 25, 2018
Messages
2,824
Likes
1,307
Location
Zg, Cro
Or, to put it another way, since phase linearisation must create pre-ringing, and since this is applied to the signal as a whole prior to the speaker's internal crossover, there is no position on axis at which the crossover filters' pre-ringing cancel each other to create a ringing-free output. The linearisation filter's pre-ringing is equal (and maximum) at every location in space.
This seems logical to me.

This would seem a suboptimal approach to me (again, no comment on audibility per se as I'm not aware of much research either way on this matter).
Sure it is, but what else can you do with speakers with passive crossover apart from converting them to active digital? And, as you said, nobody ever proved nor even claimed to hear that ringing.
 

andreasmaaan

Major Contributor
Patreon Donor
Joined
Jun 19, 2018
Messages
3,306
Likes
2,421
This seems logical to me.

Sure it is, but what else can you do with speakers with passive crossover apart from converting them to active digital? And, as you said, nobody ever proved nor even claimed to hear that ringing.
Sure :) But if you want to take that approach, nobody's ever proved they can hear the the group delay caused by the minimum-phase crossover in the first place either, and far more work has been put into trying to demonstrate that that can be heard!
 

Krunok

Major Contributor
Joined
Mar 25, 2018
Messages
2,824
Likes
1,307
Location
Zg, Cro
Sure :) But if you want to take that approach, nobody's ever proved they can hear the the group delay caused by the minimum-phase crossover in the first place either, and far more work has been put into trying to demonstrate that that can be heard!
I agree. But on the other hand, we probably all agree that once you make FR linear (and room will always make it non-linear down from Schroeder frequency unless you live in anechoic chamber) you will be able to hear the improvement. Contrary to all these timing-related stuff that really helps.. :)
 
Thread starter Similar threads Forum Replies Date
Purité Audio Desperate Dealers Forum 2

Similar threads

Top Bottom