You mean the 'BBC dip' that people have invented and was not in the speaker design? Tut, bad Jakob for repeating internet lore instead of researching it. 😛
Here's the freq lines file I found.
There is also a phase- and level set but I can't find that right now.
Note that this data changes with sample rate and max allowed crest factor.
My dScope III has this build in, as have the newer AP systems.
For S1 and S2 versions there is an app to specify the data files. The utility used to be named makefile.exe. Could still be in the legacy section on the AP site.
Anyway, you can always download the AP software and run it in demo mode, you can then make multitones and save them as Excel for use for instance in a simulator.
Jan
There is also a phase- and level set but I can't find that right now.
Note that this data changes with sample rate and max allowed crest factor.
My dScope III has this build in, as have the newer AP systems.
For S1 and S2 versions there is an app to specify the data files. The utility used to be named makefile.exe. Could still be in the legacy section on the AP site.
Anyway, you can always download the AP software and run it in demo mode, you can then make multitones and save them as Excel for use for instance in a simulator.
Jan
Okay. I haven't messed with that stuff in awhile, but I'll gather up my files, and see if I can put together some examples of how I've been using it over the weekend. It will be worthwhile to hear suggestions from those who actually understand how this stuff works. 😕
- Jim
P.S. I suppose I should start a new thread when the time comes, but I'll post a pointer here.
- Jim
P.S. I suppose I should start a new thread when the time comes, but I'll post a pointer here.
Usually "i´ve heard different" is sufficient for your purposes so i opt for that... 😉
But to be serious, i´ve first heard a long time ago about this "BBC dip" and was looking for references. It was mentioned by Harwood in a Wireless World article and as several other resources - means people who worked with or at the BBC research department - confirmed the information, i´d say research showed nothing different.
Does that mean it can´t be wrong? No, of course not..... 😎
Thanks Jan. Interesting how the various frequencies "avoid" each other.
I'll try putting together a generator for these tones using the software I mentioned earlier. Unfortunately it only outputs at 16/44, so will be far less useful for anything critical; but it will run on any Windows box for whatever that's worth.
- Jim
Here AP's take on t:
Using Multitones in Audio Test - Audio PrecisionAudio Precision
There are two app notes (they call them tech Notes): TN-18 and TN-12 but I think they are so old they don't run on W10. Maybe even need DOS...
Edit: there's a recent utility that is VERY useful but does not provide multitones: http://www.ap.com/download/apx-waveform-generator-utility-2/
Jan
Using Multitones in Audio Test - Audio PrecisionAudio Precision
There are two app notes (they call them tech Notes): TN-18 and TN-12 but I think they are so old they don't run on W10. Maybe even need DOS...
Edit: there's a recent utility that is VERY useful but does not provide multitones: http://www.ap.com/download/apx-waveform-generator-utility-2/
Jan
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Yeah a 30 year old article from memory always beats 10 seconds of research. In the time you took to type the above you could have actually looked up some real up to date information. Like say this. Harbeth UK - High quality speakers made in England
precis: it was to get around resonances in the plastic cones but did help near field monitoring as it moved the sound stage back. Not used across the board and certainly not in the much loved LS3/5a or any modern BBC 'derived' designs.
Now i´m really puzzled.
At first you accused me of "repeating internet lure instead of researching it" and now, after finding yourself a confirmation that it was more than an internet lure, your´re still criticizing _me_ ? Because i did rely on an article written by the guy who really mentioned it? Strange world. 😎
Btw, what i was talking about (illustrated by some examples from loudspeakers) was the difficulty to define something like "accurate reproduction" and the mentioned "taunus sound" and "british smoothing" were both justified with psychoacoustic and sound field consideration (afair if i´m allowed to say so 😱 ) and the same holds true for the "famous BBC dip" .
Harwood pointed out a long time ago the psychoacoustic foundation:
".....if by "bending" the axial response curve of the loudspeaker a more realistic psychological impression is obtained, then this is entirely justified.
Thus, for example, if a uniform output is maintained at all frequencies an orchestra sounds extremely close. This condition is quite unnatural and a much better sense of perspective is obtained if a slight dip in the 1 to 3kHz
region is applied. About 2dB is sufficient to provide the more distant perspective without destroying the sound quality. It may well be that as techniques progress other such tricks will follow. All that is intended at this stage is to get away from the rigid idea that a uniform axial response is necessarily the best. "
(Harwood H.D., Some factors in loudspeaker quality, Wireless World May 1976, p.48)
That was just a small exerpt from his article and he offered a lot more interesting facts and ideas related to loudspeaker design, room interaction and psychoacoustic results of experiment and he didn´t forget to mention at the end that not all colleagues within the BBC would necessarily agree with all ideas as there was sometimes limited evidence at hand.
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The .wav files I included in my article have some spectra with
"holes" like we used for ADSL testing that are interesting to play with. Folks should be aware that they should have some familiarity with sampling frequency, FFT length, and windowing to accurately interpret results.
A few years back I was able to download AP software that did the multi-tone generation, among other things. IIRC, you could even control the phase of each tone. Is that still around?
Does it need the hardware? The AP software would do a lot in demo mode, not connected to hardware.
I think it does.
The nice thing with the AP utility that you don't have to worry to get all the phases and levels right - does the number crunching for you.
Not sure how Virtins does that.
The very 1st AP utility was a DOS thing and will not run on W10 for me.
Jan
The nice thing with the AP utility that you don't have to worry to get all the phases and levels right - does the number crunching for you.
Not sure how Virtins does that.
The very 1st AP utility was a DOS thing and will not run on W10 for me.
Jan
I downloaded the latest APx500 software and ran it in demo mode.
Then selected Multitone Analysis from the Navigator, then selected Create New from the Waveforms selector mid-right.
See attached. You can specify it here and save it even as a .wav file. Easy.
BTW I ran the software in sequence mode, not in bench mode.
Jan
Then selected Multitone Analysis from the Navigator, then selected Create New from the Waveforms selector mid-right.
See attached. You can specify it here and save it even as a .wav file. Easy.
BTW I ran the software in sequence mode, not in bench mode.
Jan
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I'm learning as I go here, but I see now that these tone sequences are chosen not only for their inharmonicity, but also to synch up with what's listening at the other end. Interesting stuff to be sure.
- Jim
I've been sick in bed for a few days plus and haven't even turned on my computer but am trying to catch back up to where we are on this thread.
A comment to what RNM has said in his response to Jan about how his room does not effect the sound of those JBL M2's, that is pure bs in my eyes. The purpose of the strange horn shape is in effect to fill in the margins, or to put it another way to even out the distributed sound pressure over a wider dispersion angle. That said to call that horn a narrow dispersion design seems to be rather a bold statement, I highly suspect that the horn is working at a wider dispersion pattern than 60 degrees in total. Now bring in the dispersion pattern of the cone driver and you can't possibly call these speaker narrow dispersion speakers as a whole. So to say the room has little to no effect on how they sound just seems silly.
I am not saying they don't sound good to great, I just don't ascribe some magic principals to how they are working. I'm well aware of what can and can't be accomplished with a single horn/compression driver and single cone driver combination, there is no magic here.
A comment to what RNM has said in his response to Jan about how his room does not effect the sound of those JBL M2's, that is pure bs in my eyes. The purpose of the strange horn shape is in effect to fill in the margins, or to put it another way to even out the distributed sound pressure over a wider dispersion angle. That said to call that horn a narrow dispersion design seems to be rather a bold statement, I highly suspect that the horn is working at a wider dispersion pattern than 60 degrees in total. Now bring in the dispersion pattern of the cone driver and you can't possibly call these speaker narrow dispersion speakers as a whole. So to say the room has little to no effect on how they sound just seems silly.
I am not saying they don't sound good to great, I just don't ascribe some magic principals to how they are working. I'm well aware of what can and can't be accomplished with a single horn/compression driver and single cone driver combination, there is no magic here.
The frequencies are chosen to match the resolution and sample rate of the FFT so that all products fall exactly in FFT bins with no overspill.
Jan
Yes, I'm beginning to grok this. My 500-sinewaves thing seems pretty crude & silly by comparison.
- Jim
- Jim
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