Secondly, free-field response or in-room response?
I am still trying to find the truth out of all the assumptions, propositions, beliefs, myths, etc, even though this is philosophically impossible. Some people believe that boundary reflections are delayed response therefore can not be corrected with EQ. Others argue that short term reflections are of minimum phase in nature therefore can be corrected with EQ. I guess the devil is in the details, or perhaps the time window of the reflections. But that is only my guess, or my proposition. I would like to learn more from others.
With my current 4 way active open back speaker project, I have used Linkwitz' FRC and in-room measurements (20ms, 40ms, 80ms) with good result, but not sure if it is "perfect" / "correct", as I can not compare it to the otherwise. The system is designed for the room for a single seat. The 20ms, 40ms and 80ms measurements show basically identical response at the listener's position and the crossover is designed based on 40ms measurements in reference to the 6ms / 1m measurement for the tweeter.
It is good that we can compare notes.
I am still trying to find the truth out of all the assumptions, propositions, beliefs, myths, etc, even though this is philosophically impossible. Some people believe that boundary reflections are delayed response therefore can not be corrected with EQ. Others argue that short term reflections are of minimum phase in nature therefore can be corrected with EQ. I guess the devil is in the details, or perhaps the time window of the reflections. But that is only my guess, or my proposition. I would like to learn more from others.
With my current 4 way active open back speaker project, I have used Linkwitz' FRC and in-room measurements (20ms, 40ms, 80ms) with good result, but not sure if it is "perfect" / "correct", as I can not compare it to the otherwise. The system is designed for the room for a single seat. The 20ms, 40ms and 80ms measurements show basically identical response at the listener's position and the crossover is designed based on 40ms measurements in reference to the 6ms / 1m measurement for the tweeter.
It is good that we can compare notes.
Agreed.
But I suspect we can gain some consensus and perhaps develop an objective PFRC if we define a standard method of testing in-room FRC (IN-FRC) which leads to the next...
I think free-field response (FF-FRC) is the only _easy_ way for us to compare notes. In room we might make changes to minimize effects of the room and most would agree that the room is part of the problem.
Of course the in-room response (IR-FRC) is important so we need to compare the IR-FRC to the FF-FRC so we can "see" the effects of a room and how we might improve another room.
This comparison and collaboration of multiple peoples conclusions could help lead us the the PFRC..... but as you say it may be subjective until many open minds have come to the same conclusion.
That sounds like a reasonable test regimen and if you can provide me more insight I would greatly appreciate it.
Perhaps it would be useful to hash out more details of the test plan as well. I'm thinking the following and would be happy to hear feedback to fine tune:
#1 Outdoors/Free-field as the starting point so one can accurately compare one speaker to another independent of the room.
#2 Indoors is obviously important so testing should be included. Since the size of listening rooms vary substantially, we can start with:
- Minimum Phase (MP-FRC) no smoothing: 2ms is the time in which the speaker has _mostly_ completed the impulse response and probably not much room interaction. This would be the basis for comparison to free field.
- Full Impulse (FI-FRC) no smoothing: 3-8ms. This, in my case would be the time at which the speakers have _actually_ completed the majority of the impulse response. I suspect that in most this number would be between 5-8ms and _should) give very close results to free field. Aberations are very likely the first reflections off the floor and possible side walls and roof. They _may_ be minimum phase and _potentially_ could be minimized with EQ. It would be best to have both EQ and non-eq measurements. Others have suggested to me that parhaps this should not be used to measure below 500 hz.
- Single reflection (SR-FRC) no smoothing: 15-20ms. This is the point at which (in most rooms) the first room reflection is part of the FRC. It can help identify how far speakers are placed from the rear wall and the impact of that wall on the free-field response which can be substantial (i.e. out of phase).
- Dual reflection (DR-FRC) no smoothing: 20-30ms. At this point, in many rooms, the second/rear reflection is now part of the FRC. This reflect may not be as substantial as the first, but if it's cancellation is at the same frequency as the first it would definitely indicate a pretty serious problem. Perhaps the primary use of this measurement would be to help determine an alternate placement of the speaker or re-positioning of the listener.
- Multiple reflection (MR-FRC) multiple smoothing options?: 40-50?, 80?, 160? 320?. Now we can compare the full integration of the diffuse sound field and get best visibility into the frequency response in room over time and at low frequencies. It could be suggested that perhaps this should ONLY be used for low frequency analysis. (Below 100Hz?)
Thoughts? Perhaps after we get some more details and forethought into this we could present the idea to Linkwitz and see if he would be interested to provide some of his valuable input.
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Many kinds.... but no crap. 😉
More seriously I enjoy lots of different music but here is some of the stuff I've been listening to recently.
A few of the female vocalists I've been listening to recently are Diana Krall, Tori Amos, The Chieftans, KD Lang, Singers unlimited
I also like male vocalists: Robert Wilson is nice, Jack Johnson, Xavier Rudd,
I like strings: My favorite would be the double bass (Yo-Yo Ma) and acoustic guitars (like Robert Wilson).
I like classical music and even some opera. I've been listening to Vivaldi lately.
I like rock: I've been listening to Pink Floyd quite a bit and Metallica is very good. Tool has some really good tunes.
I even listen to some of the oldies... but alot of the really old recordings aren't so great for evaluating speakers.
I've found it helpful to compare to the sound of the speakers to that of some good headphones. Headphones don't have a very pleasant sound stage but it seems helpful for me to verify an appropriate tonal balance. I recently purchased a pair of Roland RH-300 closed back units. I think you'll find the frequency response interesting.
An externally hosted image should be here but it was not working when we last tested it.
I've been studying this idea some more. I'm let inclined now to believe that the inroom listening results may not be of much us for us in terms of collaborating to determine the FRC. There are way to many room performance variables and I'm not nearly concerned about how your room sounds nor you are overly interested in my room.
I created some new plots and get very nearly the same results as well when I do the 20-40-60 ms testing. Just that with the longest test I get the most accurate data about the low end.
For the single mined and basic purpose of comparing for FRC perhaps we only need to use long term 60ms FF-FRC with 1/3 octave smoothing.
I present, SANE9 Free field, 60ms FF-FRC;
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Thanks, Sanedesign. I am sorry that I have not had time to reply. I have so limited time these days. Perhaps I should never engage in discussions anymore like what I used to if I don't have time to finish a discussion. I will see if I have some time in the coming a few days (at work).
Your last graph likes perfect to me. Mine is quite close to that, except that it goes higher from around 4k, not to my intension, but a compromise for simplicity in XO network.
By the way, thanks for that link. It was a good read.
Regards,
Bill
Your last graph likes perfect to me. Mine is quite close to that, except that it goes higher from around 4k, not to my intension, but a compromise for simplicity in XO network.
By the way, thanks for that link. It was a good read.
Regards,
Bill
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What Software
Sanedesign
What software are you using for you measurements? Most importantly, is it easy to use?
David
Sanedesign
What software are you using for you measurements? Most importantly, is it easy to use?
David
Linkwitz transform can be realised using notch filter and shelving lowpass. It is not required for low-Q woofer equalisation as normally two shelving lowpass will do.
Cascaded filter:
Crossover topology mistakes
I have been thinking more about this and since he needs two DCXs to handle 4-way pair of speakers can he not split the single channel signal on the on DCX and cascade using the filters available to each channel before each ouptut gets filtered??
I don't think so. The DCX can't branch off between the high pass and the low pass filter of a crossover. And there is no re-entry to use the second half of a Xover filter either.
Rudolf
So setting a HP filter on input CH1 and a LP filter on input CH2 doesnt effectively split branch off the the signal?
Output 1 and 2 could use CH1 and Output 4 and 5 could use CH2.
Im essential creating picture with this.
Output 1 and 2 could use CH1 and Output 4 and 5 could use CH2.
Im essential creating picture with this.
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I'm using Fuzzmeasurepro. It seems very easy to use.
http://www.google.ca/url?sa=t&sourc...sg=AFQjCNFCUu_JLgBvVlXOHjqe9j4d0b9TbQ&cad=rja
The input filters are no real crossover HP/LPs, but shelving EQ filters only. And if you want to go from one filter to another one in another channel you have to pass a DAC at the exit of the first channel and a ADC at the next input 🙁
I don't see any serious way to do cascaded Xovers with the DCX - regardless of how many you have.
Rudolf
Agreed.
I have 2 EQs available per channel but:
1. multiple crossovers per channel would be very useful and in my opinion are the biggest limitation. (This would enable proper dipole compensation and possibly cascaded filters)
2. I also don't believe that the existing crossovers nor the EQs are phase linear like other solutions might offer.
3. The EQ circuits simply do not perform exactly the way they are configured and they should be able to.
Still, I think they are a great value and the performance is quite good.
Totally agreed.😉
For a long time the DCX was the best value in digital EQ you could get for small money. But with the advent of systems like miniDSP the shortcomings become more apparent. Still - as long as those miniDSPs are less "plug-and-play" than the old Behringer, I'll stick to my DCX. 😀
I'm thinking about that miniDSP... I'm not clear about how I can use it to replace DCX. Can I somehow use digital input and it does all processing digitally and provide me 10-12 analog outputs?
I'm thinking it might be easier to do all my processing on a PC and use outboard multichannel soundcard like a ProFire2626. (My understanding is that this would be something similar to the way StigErik does that monster no baffle setup)
I appreciate any insight.
The manufacturers thread I found it really helpful. And those people appear to listen to what users say ... 🙂
I have had both, and the MiniDSP is just as plug and play as it gets. Og vourse you have to put it in a box, if you want digital in/out. For analog in/out there is a boxed version.
Alright... I just read the whole thread. Looks like it might do everything we need doesn't it? With the exception of long delays I can't think of much I would miss. Am I missing anything?
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