That is not a course I want to pursue. I'd rather leave things as is than put a processor in the signal path. But I do appreciate the thought, and it would be a good recommendation for most folks. I want to solve this acoustically. I am not that far off. If I can gain 2-3db in the null range specified, ill be a happy camper.
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I fully appreciate your steadfast determination.
I also holey agree with by-passing any digital manipulation of your signal.
I too, am a stalwart of keeping the path unencumbered as possible.
Especially with regard to my vinyl playback, but also for my digital source.
While many are touting the efficacy of DSP, especially for LF, I do not deny that it can be a V good solution for some situations.
I recently heard the Legacy DSP products at the Capital Audiofest & it was impressive.
But I still prefer my coffee black, my scotch straight up, my women wholesome & my audio pure.:W- Bottom
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I fully appreciate your steadfast determination.
I also holey agree with by-passing any digital manipulation of your signal.
I too, am a stalwart of keeping the path unencumbered as possible.
Especially with regard to my vinyl playback, but also for my digital source.
While many are touting the efficacy of DSP, especially for LF, I do not deny that it can be a V good solution for some situations.
I recently heard the Legacy DSP products at the Capital Audiofest & it was impressive.
But I still prefer my coffee black, my scotch straight up, my women wholesome & my audio pure.:W
I am a Crown Royal guy, but strait up is the only way!
I like the DSP's for guys that wont (lazy?) or cant (wife?) treat their room acoustically. They seem to do more than merely EQ.
If the case here was that the problem was in the range the sub operated, then I wouldn't have any qualms to putting a DSP type device on it. Its from 100hz up I don't want any signal degradation. My sub cross over at 40hz, way below the 170-250hz range where my problems lay.Last edited by jim1961; 27 September 2013, 22:08 Friday.Seek out and destroy early high gain room reflections- Bottom
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One of OEM features of my 35+ yo modified Carver C-19 pre that I truly love is its by-pass function.
It allows zero gain in the output stage through the upgraded Alps volume pot that was installed.- Bottom
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Out of curiosity, and off subject, if you don't need the gain, why not go full passive?Seek out and destroy early high gain room reflections- Bottom
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The C-19 also has a built-in phono section that, since the entire unit’s modification 2 years ago, is one of the best I have ever heard in the < $2k category along with providing a selectable sub-sonic filter.
It has tubes which, up to this point, have proven quite helpful in taming the digital signals that are fed to it when I am not spinning vinyl.
It was a gift seven years ago from my V best friend, mentor, teacher, surrogate father & most extraordinary individual that I have ever met. Since Rod’s passing just over a year ago, I doubt even more that I will be replacing this most cherished object, ever.
Lastly, it is Black……
& it has had its LED converted to Red……
…….therefore, meeting the two most important requirements related to producing the most accurate reproduction earthly attainable. :W- Bottom
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Is the dip centered around 225 Hz a function of the anechoic response or the room interaction? It's actually pretty wide for the latter, I'd think...
Other than that, looks pretty dang nice, bitty the drop in the 200 Hz area corresponds with what is usually referred to as the power region for classical symphonic music as well as key upper fundamentals in many other kinds of music- should be fairly audible. how's it sound to you, compared with reference grade headphones?
Leeuwarden, Your intuition has the same merit.
Looking at this again, it does seem the speaker response is part of it. The similarity to the near field my brother measured has some striking similarity.Seek out and destroy early high gain room reflections- Bottom
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That makes more sense- and might be addressable.the AudioWorx
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At LP
Here is a ETC (no smoothing) at 200hz .33 octave bandwidth (176-222hz) with just the mids tweets running (ignore blue line at top). If it was room interaction, wouldnt the ETC show a significant peak somewhere?
If the mid lull (160-250Hz) isnt caused by a reflection (SBIR), then what does that leave? Room modes? If its room modes, im sunk :cry:Seek out and destroy early high gain room reflections- Bottom
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BTW, where is the woofer to mid crossover frequency? Is this dip possibly due to floor bounce effects?the AudioWorx
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The mid/woofer Xover is right in the middle of the null. Around 200-225hz. Floor bounce is a definite possibility. Even probable. But I already have so many rugs on the floor on top of each other that I nearly trip over them.Seek out and destroy early high gain room reflections- Bottom
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Floor bounce was the direction I was heading yesterday so I did some experiementing:
1) Put a 24'x24" 2" OC703 panels at bounce spot
2) Put rather large 3/4" board angled to deflect reflection
3) Used solid board and OC703 panel to block reflection
In each case, the 200hz response went down not up. If the floor bounce is responsible, wouldn't one of the attempts above yielded MORE energy at 200hz, not less?
Ive spent over a year treating my room to get this response.Seek out and destroy early high gain room reflections- Bottom
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Jim,
Have you contacted Troels about what you've measured? I don't particularly want to suggest monkeying around with another guy's design, but I know from experience that getting the woofer to low mid crossover down just right isn't particularly easy- one of the many reasons three ways are harder than two ways. But my first impulse is to say, this should be fixable- or at least worth investigating to see if that's the case.
Troels has some pretty complete graphs and info for response above 200 Hz, but it seems to me that he treats below 300Hz as "There be dragons", as the old saying used on parts of the map where there is no information.
If you could measure the response and generate FRD files for the woofer, mid, and tweeter on axis at a listening position, with the speakers in a good position in the room to avoid too much in the way of boundary interaction, I'd be curious to try modeling the system with the published crossover and see if there is any straight forward way to move forward or not. I'm going to be real busy at work (probably 7 days a week) starting the end of next week for a while, but still I can find some time somewhere to squeeze that in, even if later in the fall or November.
Your call of course, if you want to investigate this some more. This particular response short coming is something I find fairly annoying and obvious- my GF says she almost feels sorry for the "ear" I have, both for acoustics and music (I'm very strict about being in key, and poorly tempered instruments drive me up the wall!) (I just gave her a new digital tuner with a built in microphone, if that tells you anything... :W )
Let me know what you think... It would be better philosophically if Troels could provide a solution, but he might not even have these sitting around.. Let me know what you think.the AudioWorx
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If you look at my brothers near field reading (earlier in this thread), and my own unpublished ones, I think the speaker may have a null in the crossover region of the mid/woofer, but only a part of what I am seeing at the listening position. In other words, I can make the 220hz null either go away or move to a different frequency by moving the mic position. Post #192 clearly shows the midrange null goes away when reading at a closer distance.
So what we are up against is mostly a non perfect room (aren't they all?). Are your proposing we counter the room deficit with a proportion "hump" in the speaker response? If not, please explain what you are proposing.
This shows the L and R channels for the woofer/sub vs mid/tweeter responses. The sub and tweeter are inconsequential so including them doesn't tarnish the data. Even these responses are a bit different today than what these show per yesterday for I moved things a bit (again).Seek out and destroy early high gain room reflections- Bottom
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I'm proposing that you do gated measurements of the woofer and mid woofer which will result in quasi-anehoic response to confirm if the existing crossover design is the issue or if room boundary and room modal effects are causing the issue. You can't separate out floor bounce- the design has to deal with that.
What is the window gate time on these measurements, and what kind of room position do you have for the speakers and measurement microphone? What position makes it worst, what position for the mic makes it "go away"?
Normally when I do in room measurements I do them at a minimum of 2 meters, and at ear listening height. I use the minimum window length with a Half Hamming window that gives me valid LF data down to at least 100 Hz, but preferably 50 Hz. Not many data points down there, and not very good resolution, but for a crossover in the 200-300 Hz area, it's desirable to have valid data points at least every 25-50 Hz. It's a balancing act for getting the system response without too much room effect. But then I also do measurements with 200 msec window, just to compare, and identify room issues and boundary effects that can mess up things in the crossover region.
Part of the system design, of course, is picking the driver positions relative to the floor boundary in the initial design and making sure that doesn't put problems in the crossover region, to where one could be fighting the crossover and the floor issues at the same time.the AudioWorx
Natalie P
M8ta
Modula Neo DCC
Modula MT XE
Modula Xtreme
Isiris
Wavecor Ardent
SMJ
Minerva Monitor
Calliope
Ardent D
In Development...
Isiris Mk II updates- in final test stage!
Obi-Wan
Saint-Saëns Symphonique/AKA SMJ-40
Modula PWB
Calliope CC Supreme
Natalie P Ultra
Natalie P Supreme
Janus BP1 Sub
Resistance is not futile, it is Volts divided by Amperes...
Just ask Mr. Ohm....- Bottom
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I'm proposing that you do gated measurements of the woofer and mid woofer which will result in quasi-anehoic response to confirm if the existing crossover design is the issue or if room boundary and room modal effects are causing the issue. You can't separate out floor bounce- the design has to deal with that.
Post #188 attempts to compare the near and far field responses.
Black = Absorber
Orange = Diffuser
Gray = Reflector
This ^^^^ shows the basic speaker to mic orientation.
Post #192 shows when the null goes away and also describes at what distance (46"). Basically speaking, the closer the LP (mic) is to the speaker, the less the null. The closer the speakers are to each other, the less the null.
Normally when I do in room measurements I do them at a minimum of 2 meters, and at ear listening height. I use the minimum window length with a Half Hamming window that gives me valid LF data down to at least 100 Hz, but preferably 50 Hz. Not many data points down there, and not very good resolution, but for a crossover in the 200-300 Hz area, it's desirable to have valid data points at least every 25-50 Hz. It's a balancing act for getting the system response without too much room effect. But then I also do measurements with 200 msec window, just to compare, and identify room issues and boundary effects that can mess up things in the crossover region.
Omnimic (my measurement system) doesnt have a half hanning feature. So I would trust the measurements in post 114 and 130 for the near field readings.
Part of the system design, of course, is picking the driver positions relative to the floor boundary in the initial design and making sure that doesn't put problems in the crossover region, to where one could be fighting the crossover and the floor issues at the same time.
This is my latest measurementLast edited by jim1961; 14 October 2013, 11:41 Monday.Seek out and destroy early high gain room reflections- Bottom
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This is my best attempt to put the far and near field measurements on one graph.
I used the "blended" setting thats defined as: blends from the "only to" calculation at higher frequencies, to the "all" calculation at lower frequencies. In other words, this mode removes echoes when it can, and doesn't when it can't.
The "only to" in this case is a 5ms gate. "all" refers to no gate. The Green graph is my "blended" response at 1M distance at midrange height. The Red graph is the far field (listening position response, 2.4M distance 250ms gate)Seek out and destroy early high gain room reflections- Bottom
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So as long as I keep surpassing previous milestones, I keep pushing on.
I think I need to add that despite the emphasis here on the FR, I actually find more bang for the buck in working on early high gain reflections. When you get ALL those down to -20db, -30db even better I hear things in the recording never experienced before.
I could achieve a better FR curve if I ignored the ETC data. So what is seen here is the lower priority aspect of my goals.
Getting this ^^^^ was much harder than getting the FR decent. As it turns out, removing early high gain reflections naturally makes the FR better given nulls and peaks caused by room interaction are minimized. The present course I am on is the icing on the cakeSeek out and destroy early high gain room reflections- Bottom
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Wow!
I absolutely love that graphic!
First time I have seen that used.
It really shows the data in a manner that one can easily conceptualize.- Bottom
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Black = Left Channel (1/24th oct smoothing)
Red = Right Channel (1/24th oct smoothing)
Orange = +3db peak
Cyan = -3db null
Blue = -4db null
[the bass (below E3) isnt considered given the intentional +3 - 4db]
Just looking for new ways to look at the data and put it in a context most easy to assimilate. What id really like to do is plot a graph right on the keys themselves. Havent figured that out yet.Seek out and destroy early high gain room reflections- Bottom
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