Im using a microphone from an older version of this device:
Room Analyzer II
Unfortunately its not calibrated.
Later on i will try to measure with 2 different laptops.
The mic response is not a factor for a delay timing effort. The phase of each driver is impacted just the same on the measurements so the phase tracking is just a accurate as with a calibrated mic.
I was looking at the measurements again and while I was able to do this job the data is not really good enough for most uses. The signal level is only about -40dB. I assume you adjusted the sweep level to provide about 75dB in the room. If that is correct then there is not enough gain in the mic input channel. A level providing about -15 or -20dB would be much better. Correcting this will help a lot, but it would also be helpful to reduce or eliminate the tick as well.
I assume the source of your tick is similar to mine. I use a FocusRite 2i2 USB audio interface with REW and it requires using a loopback cable on the other channel for a timing lock. The 2i2 has poor channel separation and a tick can also be seen on my charts from bleedthrough of the timing channel onto the measurement channel. My ticks are much smaller in level than yours are however. In your case the tick is much higher than the MR Horn IR. Without knowing you specific setup and connections for the soundcard it is not possible to narrow the possibilities.
General Thoughts
Level:
> Are you sure the measurement mic is selected in Holm so that Holm is not using an internal mic on a notebook PC?
> Is the input sensitivity of the line input (or USB input) on the PC volume controls set too low?
> Is there a pad or boost option in the operating system for this mic input that would help?
> Maybe monitoring or 'listen to this device' is selected in error in the PC device? That would prevent you from increasing the input gain because feedback would occur.
Ticks:
> Have you tried both the line input and the USB connection of the mic with the same results?
> Is the sweep signal being routed to both channels such that crosstalk in the soundcard or other component may be the cause? Remove any loopback cable on the channel not being used for measurement.
> In your settings shown above you show 'HOLM/Device & Signal/Output' selected to use both Left and Right channels for output. Disable the channel not being measured.
General:
> If you use the line/mic input on a PC soundcard then have you done a loopback calibration of the sound card to create a soundcard calibration file and to assure a clean signal?
> A loopback calibration can also include any additional line level equipment that you may have connected before the P-amp.
These are just random thoughts and some may not apply to your setup. The point is that it would best to assure that the entire measurement system is operating at reasonable levels before using it to analyze the audio system. If this delay timing activity is the only job you intend to do, the measuring system may be just good enough as is to get the job done.
I was looking at the measurements again and while I was able to do this job the data is not really good enough for most uses. The signal level is only about -40dB. I assume you adjusted the sweep level to provide about 75dB in the room. If that is correct then there is not enough gain in the mic input channel. A level providing about -15 or -20dB would be much better. Correcting this will help a lot, but it would also be helpful to reduce or eliminate the tick as well.
I assume the source of your tick is similar to mine. I use a FocusRite 2i2 USB audio interface with REW and it requires using a loopback cable on the other channel for a timing lock. The 2i2 has poor channel separation and a tick can also be seen on my charts from bleedthrough of the timing channel onto the measurement channel. My ticks are much smaller in level than yours are however. In your case the tick is much higher than the MR Horn IR. Without knowing you specific setup and connections for the soundcard it is not possible to narrow the possibilities.
General Thoughts
Level:
> Are you sure the measurement mic is selected in Holm so that Holm is not using an internal mic on a notebook PC?
> Is the input sensitivity of the line input (or USB input) on the PC volume controls set too low?
> Is there a pad or boost option in the operating system for this mic input that would help?
> Maybe monitoring or 'listen to this device' is selected in error in the PC device? That would prevent you from increasing the input gain because feedback would occur.
Ticks:
> Have you tried both the line input and the USB connection of the mic with the same results?
> Is the sweep signal being routed to both channels such that crosstalk in the soundcard or other component may be the cause? Remove any loopback cable on the channel not being used for measurement.
> In your settings shown above you show 'HOLM/Device & Signal/Output' selected to use both Left and Right channels for output. Disable the channel not being measured.
General:
> If you use the line/mic input on a PC soundcard then have you done a loopback calibration of the sound card to create a soundcard calibration file and to assure a clean signal?
> A loopback calibration can also include any additional line level equipment that you may have connected before the P-amp.
These are just random thoughts and some may not apply to your setup. The point is that it would best to assure that the entire measurement system is operating at reasonable levels before using it to analyze the audio system. If this delay timing activity is the only job you intend to do, the measuring system may be just good enough as is to get the job done.
sumaudioguy - but maybe many of us didn't see that and you didn't reference it. Why not just give us an explanation of your rather blunt statement. One that I have real trouble accepting since I have used Holm for many many years and never found timing to be an issue. I would have thought that "phase and timing information from HOLM is useless" would have somehow shown itself by now.
It's only a few posts back Earl http://www.diyaudio.com/forums/soft...requency-impulse-response-29.html#post3935714
Tony.
Tony.
I think i solved the problem with the tick. I shut everything not needed of in the control panel on the laptop and i also increased the volumes, both microphone and speakers and also on my preamp.
Ive sent some measurements to Jtalden, i hope he will find these more useful to work with.
Im not 100% sure what you mean but my measurements are pretty the same
if i do new measurements (without any software changes of course).
Microphone distance is about 4.5 meters, no wall directly behind.
If Jtalden is not happy with my new measurements this will be a good thing to try.
Here is some new pictures with polarity changed on midbashorn and a delay 2.19ms on HF-horn.
Im have no idea how to read the phase curves but Jtalden says there looking good and i trust him.
I will make some new measurements with the microphone close to the speakers just for the fun of it
Im have no idea how to read the phase curves but Jtalden says there looking good and i trust him.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I will make some new measurements with the microphone close to the speakers just for the fun of it
Looks good.
there was a minor slip of the time lock between the TW measurement and the TW+MR measurement as can be seen by the 140° phase difference at 20kHz. I often have this much time slip in my measuring session also. We can see this had a trivial impact in the 1k XO range so it was no issue here. It's just something to watch for.
The closer measurement should help reduce the strength of the room reflections and provide a smoother phase trace. It will be interesting to see.
there was a minor slip of the time lock between the TW measurement and the TW+MR measurement as can be seen by the 140° phase difference at 20kHz. I often have this much time slip in my measuring session also. We can see this had a trivial impact in the 1k XO range so it was no issue here. It's just something to watch for.
The closer measurement should help reduce the strength of the room reflections and provide a smoother phase trace. It will be interesting to see.
A few comments on "why he is wrong" would be useful before I start investing the time to familiarize myself with this software (I've been using SoundEasy and ARTA).
New measurements, mic distance 2.5 meters.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I just found nothing of substance in his claim, no supporting data or even a plausible explanation. Something about HOLM making "incorrect assumptions about a loudspeaker" - HOLM simply takes data and analyzes it, it doesn't make any assumptions about that data. It doesn't even know if the data is acoustic or just electrical.
As Pan says, I have used HOLM for about a decade now and I find it to be (nearly) perfect. I have seen a few glitches along the way, mostly things that do not repeat themselves.
For some reason, on one of my computers, the time base lock simply jumps at random for no apparent reason. This is obvious in my case (linked polar response impulses), but may not always be so obvious. But this could also be the sound card resetting itself for some reason. I suspect that it is not HOLM doing this at all.
If the original claim is to be substantiated, then examples of what the error looks like would need to be shown. No such examples were given.
Last edited:
In this case 2.5m was not close enough to do much good. It only cleaned it up a little bit. It would have been better to be closer as Earl and I suggested.
That said, the delay setting still looks to be correct.
Last edited:
Gedlee and I almost never agree on anything. What he claims is possible using impulse is not possible. In HOLM, the highest amplitude of the impulse signal is compared to the highest amplitude of the microphone signal with that being assumed to represent the distance to the speaker. In short, loudness equals distance. Almost hilarious. It is extremely easy to show HOLM measures distance to the driver and phase response incorrectly. Simply do a two tone test series with any driver plotting phase and this fact will become obvious.
As a matter of fact, almost everything gedlee writes does not agree with anything written and published prior to 1975 concerning audio transducers and multi-way transducer systems. gedlee is in his own world there. I actually ignore all his post as they are almost always wrong and misleading. If you like what he does ignore my post instead.
OK so if the phase info is useless then the following would not work.
set up speaker and mic at arbitrary distance.
measure tweeter.
lock time zero
measure woofer
mesaure both tweeter and woofer
above assumes nothing has been moved during the measurements.
export the three measurements and import into a crossover simulation program.
set up a network with just the woofer and tweeter.
Compare the simulations output to that of the actual measurement.
I'm pretty sure I've done this with holm and that the result was that the two curves were identical. next time I have some speakers set up for testing I will make sure I do this.
I have definitely done the above to compare crossover sims to the actual crossover implementation with good correlation.
Tony.
set up speaker and mic at arbitrary distance.
measure tweeter.
lock time zero
measure woofer
mesaure both tweeter and woofer
above assumes nothing has been moved during the measurements.
export the three measurements and import into a crossover simulation program.
set up a network with just the woofer and tweeter.
Compare the simulations output to that of the actual measurement.
I'm pretty sure I've done this with holm and that the result was that the two curves were identical. next time I have some speakers set up for testing I will make sure I do this.
I have definitely done the above to compare crossover sims to the actual crossover implementation with good correlation.
Tony.