Is it kosher to use an RCA splitter?
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Subwoofer / Low Frequency Optimization
- Thread starter amirm
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Yes, no prob - the source impedance is typically two orders of magnitude lower than the load impedance, so no issue.
Yes. A RCA splitter and an Y cable are the same thing from an electrical point of view.
The problem I had when doing my research is that many articles these days are concerned with multi-sub setups as most people have given up on single subwoofer use. Also 5.1 and 7.1 H.T. articles are of little use to a 2-channel listener in my opinion, it's not 2.1 after all.
I strongly agree with the quote you made far above, I've tried corner and off center locations with no luck.
What convinced me on getting away from room boundaries and other topics was this Dennis Foley video:
https://www.acousticfields.com/ideal-subwoofer-placement-pressurization/
This article by Barry Ober............... almost everything you ever wanted to know about subwoofers
http://soundoctor.com/whitepapers/subs.htm
A thread about subwoofer crossovers possibly inverting phase.
https://whatsbestforum.com/threads/subwoofers-and-time-relationships.2990/
And a reoccurring diagram (because I'm a visual person).
https://ledgernote.com/reviews/best-studio-subwoofers/
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So here I am enjoying the fruits of my labor.
https://whatsbestforum.com/threads/kach22is-system.30259/
Sub is connected via low level IC's (inverted) from second set of outputs on the preamplifier.
Very low volume, very low crossover point.
Just enough to center a drum kit.
NOTE-1: I do not claim this setup slays any possible room mode issues, only that from a single seating position they are not an item of concern.
NOTE-2: The listening position is NOT nearfield, it is proportional for this small room, however it is nearfield for the subwoofer as I'm in the pressure zone of long wavelengths. It's working, that's all I know.
NOTE-3: Please read the Barry Ober paper (warning, it's long), is he right about the analyzers and charts many depend on? How would you know when your bass is 360 degrees out of phase?
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Yep, let's put this in context, it's a different problem to solve for a single sweet-spot.
From that link:
Digital_Thor
Senior Member
I see many nice curves - below around 120hz. But how do we blend them sweetly with the mains, so that we do not get a rather big suck-out?
I try to do what Geddes describe, which is to let the mains run down as far as possible, creating a low-order downward slope and then cross the subwoofers above this slope. An example could be F3 at 60-70hz on the mains and subwoofers crossed between 90-110hz - depending on what fits the best in a given situation.
This should add 2 more sources of bass in the critical region around 40-110hz and also let them blend better - leaving only bumps to dampen, since suck-outs are something to avoid.
I found that getting the mains to blend well with the subs - really helps improving the overall sound. How do you do it?
I try to do what Geddes describe, which is to let the mains run down as far as possible, creating a low-order downward slope and then cross the subwoofers above this slope. An example could be F3 at 60-70hz on the mains and subwoofers crossed between 90-110hz - depending on what fits the best in a given situation.
This should add 2 more sources of bass in the critical region around 40-110hz and also let them blend better - leaving only bumps to dampen, since suck-outs are something to avoid.
I found that getting the mains to blend well with the subs - really helps improving the overall sound. How do you do it?
Andysu
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It vibrates the THX cinema.
Stargate theatrical Laserdisc Dolby Digital AC-3 LFE.1 at normal level
What you see in the film, is make-believe actors that are acting to no bass sound no vibrations all that we see is stuff filmed and then film edited then sound designers editors coming up with new sound effects, and then mixers mixing blending it all-together for a final mix. The lows ain't gonna shake the home would take lots, lots of subs so it is just wasted power. A real earthquake would unleash tremendous tactile energy that would damage the home depending the magnitude and time duration of the Quake that is felt for miles. Not even Earthquake in 70mm six-track Sensurround I doubt did damage to the local ABC screen 1, Bournemouth in late Dec 1974 though to almost mid 1975 the months that it played for, you'd think it would damage the walls and ceiling..
Maybe a sub/s that has the back of the box open and attached to the wall and then sealed all around so the bass wave can also travel directly into the wall and only way find out play a sine wave to see if it does some vibration and checking the watts or volts on the multi-meter to see how much is being used and checking that the sub attach to the wall isn't producing any resonate rattle buzzing noises which is gonna be hard to achieve as the buzzing rattle sounds wouldn't be part of the soundtrack those sort of noises are placed on the soundtrack of the LCRS to give us the liaison that it is.
Some bass waves can get trapped in corners and builds up it doubles in dB and why not use that with some sort something made to push that bass wave aimed towards the seating. Oh yeah bass shakers can be used and can use less power than the sub and the bass shakers vibrate and again the bass shaker should produce any resonate buzzing rattling noises other than producing the soundtrack vibration.
stargate dtshdma the LFE.1 has been unnecessarily boasted +10dB this is why I can't stand bluray 4k format they fake the levels by boasting it near field mixes. Also the rubbish bluray has missing sound where it fades from the past scene to present day, makes bluray unwatchable so got go with Theatrical Laserdisc AC-3.
It's really about translating the frequency of the LFE.1 as well as it is important to translate the LCRS into the room so the LFE.1 a narrow part of the frequency range with wavelengths so long and stuffing all that in the room.
I can use a direct amplifier reading via the Lucasfilm Ltd THX Sound System and using the audio mixer I can patch in x6 Behringer ECM8000 microphones and look at two waterfalls at the same time to sort of THX/TAP align it.
Playing the scene in the lab with the stargate over and over. Extending the LFE down lower - waterfall monitored on the Lucasfilm Ltd THX Sound System.
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Yeah this is also what I do. Mains running full range and then subs having a much larger overlap with the mains (depending on the location - one is front and center and it tapers at ~180hz and one is directly behind and I have it taper off at ~80hz).
I guess the main question I have with this approach is if it truly is the best thing for the mains?
Would all the low frequency info cause significant distortion when the mains try and reproduce it?
My potential solution (which I actually don't know if it truly fixes the issue / helps) is to run my speakers full range yet plug the ports and let the speakers naturally 'roll off', but I don't know if that would be adequate and prevent my speakers from trying to reproduce the 20-60hz which they simply cannot do with any true fidelity.
Does anyone have thoughts on this?
Andysu
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red is amplifier direct THX amp return . green is JBL subs in the room mic placed middle seat front row , and blue microphones inside JBL subs left/right of the front . so three graphs with few trade-offs like 40Hz dip i can fell that in with other JBL subs at back of room and one middle behind the oled .
i , not bothered to adjust the off-sets to see which frequency is closest nearest to the amp direct frequency response as that is the original .
i , not bothered to adjust the off-sets to see which frequency is closest nearest to the amp direct frequency response as that is the original .
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Is there any concern with phase problems from using multiple subwoofers? I understand that using 2 or 3 subs in a room, when positioned correctly, can get a flatter frequency response but isn't this just a product of phase cancellation at certain frequencies? When positioning more than one sub at different distances from the mains (which likely go down to the same frequencies with significant magnitude) won't there be interactive phase problems there? Would you actually point 2 subwoofers in different directions in a room without correcting for phase? Or does it matter less in smaller rooms because we are energizing the room? I have never done multiple subwoofers in a room, but I have obtained flat frequency response integration in a way that took the punch and life out of the low end, which is a sure sign of phase problems. Maybe I need to read more about the theories on how to integrate this, but I would imagine that it's really tricky to get correct.
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I'm not sure if plugging the ports is the correct direction since the box was designed that way. I would leave it ported and work with that. I would definitely leave the mains at full range and integrate the subs in after that. Leaving the mains at full frequency range should not cause distortion problems. They should be designed to handle it and the low end will roll off properly. Adding a filter to them will cause phase shift, which can make it more difficult to integrate subs with.
To offer counterpoint - the air spring of a sealed enclosure will (proportionally!) resist attempting low-frequency reproduction, whereas ported enclosures unload below the tuning point, and so offer no resistance whatsoever. That's why they work best with a high-pass filter just below the tuning frequency protecting them.
Sealed speakers also have better phase response than ported, due to the lag involved in getting the energy behind the cone to couple with the air mass in the port and then off to the room.
My vote is for plugging the ports and running full-range!
Regarding
...likely the more accurate statement is that flat frequency response was measured (at one location! or just a few!) which is not the same as actually having flat power response in a room (which is most easily achieved by having multiple subwoofers fill in the peaks and troughs of the long low-frequency wavelengths throughout the room through random constructive/destructive "interference").
Cheers!
Sealed speakers also have better phase response than ported, due to the lag involved in getting the energy behind the cone to couple with the air mass in the port and then off to the room.
My vote is for plugging the ports and running full-range!
Regarding
...likely the more accurate statement is that flat frequency response was measured (at one location! or just a few!) which is not the same as actually having flat power response in a room (which is most easily achieved by having multiple subwoofers fill in the peaks and troughs of the long low-frequency wavelengths throughout the room through random constructive/destructive "interference").
Cheers!
Phase is (or should be) corrected in multi-sub systems, either by the room correction program (e.g. Audyssey, Dirac Live), another optimization program like MSO (multi-sub optimization) or SFM (sound field management), or manually by the user. It's usually not all that tricky even manually (been there, done that) though may take some time and tweaking.
Note the problem you are correcting with multiple subs is usually a null and/or peak caused by room dimensions.
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Ahh yes. This all makes sense. I guess if you plug the ports and the box is a bit too big (likely due to being designed for a ported enclosure) then the roll off will just be slightly flatter but the phase will be better due to it being sealed.
Is the constructive/destructive interference that you speak of with multiple subwoofers still just phase interaction in the room? While this might create a flatter response throughout the room, doesn't it mean that there are phase problems with the low end? Or would you say that the phase problems are inherent in the room and using the multiple subwoofers works with the phase in the room to create a more equal power response?
Room modes: https://www.audiosciencereview.com/forum/index.php?threads/room-modes.25433/
Comb filtering: https://www.audiosciencereview.com/forum/index.php?threads/comb-filter-effects.25432/
In a room the sound can travel directly to the listener from the speaker, and also be reflected from a wall or other surface so that it arrives later in time. That can be considered a frequency-dependent phase shift since the phase change is related to the path length, e.g. distance and thus time the sound travels. The direct and reflected sound can interact constructively, increasing the level for a given frequency, or destructively to reduce the level heard by the listener. Certain frequencies will create peaks and (often deep) nulls based upon the dimensions of the room, mainly in the bass where standing waves (resonances) are created.
Treating everything as phase may not be the best approach, since phase is a function of frequency and distance, while the problems come about due to distance. The phase is different for each frequency since you are dealing with a fixed distance speaker-to-speaker, speaker-to-listener, and speaker and/or listener to reflecting surface (wall, floor, ceiling, table, whatever). Correct the phase at one frequency and you may make the sound worse at other frequencies.
Adjusting the phase of one speaker relative to another can help or hurt the sound at the main listening position (MLP). Adjusting the phase at one frequency may cause other frequencies to be worse. Adjusting the delay can improve one speaker relative to another so their wavefronts arrive in phase at the MLP, but that will not necessarily help variations caused by reflected sounds. That usually requires room treatment to reduce the reflections, or moving the MLP away from annoying nulls. Nulls are usually a bigger problem than peaks since peaks are usually only a few dB, well within the range of EQ, but nulls can be 20~30 dB deep, outside the range of EQ. Plus boosting a null frequency makes that frequency overbearingly loud anyplace else in the room where the sounds are not cancelled.
Comb filtering: https://www.audiosciencereview.com/forum/index.php?threads/comb-filter-effects.25432/
In a room the sound can travel directly to the listener from the speaker, and also be reflected from a wall or other surface so that it arrives later in time. That can be considered a frequency-dependent phase shift since the phase change is related to the path length, e.g. distance and thus time the sound travels. The direct and reflected sound can interact constructively, increasing the level for a given frequency, or destructively to reduce the level heard by the listener. Certain frequencies will create peaks and (often deep) nulls based upon the dimensions of the room, mainly in the bass where standing waves (resonances) are created.
Treating everything as phase may not be the best approach, since phase is a function of frequency and distance, while the problems come about due to distance. The phase is different for each frequency since you are dealing with a fixed distance speaker-to-speaker, speaker-to-listener, and speaker and/or listener to reflecting surface (wall, floor, ceiling, table, whatever). Correct the phase at one frequency and you may make the sound worse at other frequencies.
Adjusting the phase of one speaker relative to another can help or hurt the sound at the main listening position (MLP). Adjusting the phase at one frequency may cause other frequencies to be worse. Adjusting the delay can improve one speaker relative to another so their wavefronts arrive in phase at the MLP, but that will not necessarily help variations caused by reflected sounds. That usually requires room treatment to reduce the reflections, or moving the MLP away from annoying nulls. Nulls are usually a bigger problem than peaks since peaks are usually only a few dB, well within the range of EQ, but nulls can be 20~30 dB deep, outside the range of EQ. Plus boosting a null frequency makes that frequency overbearingly loud anyplace else in the room where the sounds are not cancelled.
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I understand this. I'm questioning the ability to get a flatter frequency response with more subs rather than using one (or maybe 2) sub sources and then using EQ to knock down the peaks along with really good room treatment. I would suggest using the same EQ filters on the mains (time align subs to the mains then apply EQ to all of it). I just think that adding subwoofers might flatten frequency response but could be adding phase problems, though there could be a more constructive way of doing it that I am not aware of (and I certainly haven't tried).
Aside from extending the frequency response of the mains, the main reason to add subs is usually to counter nulls, not flatten peaks. EQ is usually good enough (has enough range) to knock down peaks since they tend to be smaller, in the 6 dB range or so. I set up (crossover) my subs to operate below the range of the mains, and room modes generally fall below that range, so would not apply the same EQ to the mains (not needed). In general your sub(s) and main speakers will require different delays (or phase) to provide the best sound at the listening position.
Room treatment depends upon wavelengths so at bass frequencies becomes impractical (too large and thick) for most of us. You need very deep (thick) absorbers or diffusors (several feet). There are special treatments using resonators that are thinner but usually cost more and work only at specific frequencies. There are papers on broadband resonator (membrane) diffusors and absorbers but I have only seen a couple commercial products and they were pricey.
Any time you have more than one speaker there is the potential for phase problems. If you add a speaker (any speaker, sub or otherwise) at a different location and distance from the listener you will need to match the delay for cohesive sound. You can match phase at one frequency (and its harmonics) and that is often good enough if you align phase at the crossover point so mains and sub(s) are in phase at that point. Below that the mains contribute less, and above that the sub rolls off, so interaction beyond maybe an octave or so (depending on the rolloff rate) is less concerning. The reason for adding a subwoofer is to provide a signal phased to cancel room modes and such. It is not a problem, it is why we do it. Time (delay, "phase") alignment is required and can be done via a room correction program, outboard processor (e.g. PC program or stand-alone HW like a miniDSP or AntiMode), or controls on the sub itself.
I guess I do not understand your basis for assuming correcting frequency response can cause phase problems. You must time-align the subs, true, but adding subs should not cause phase problems unless you do not take that step to align them. Have you read papers by Welti, Geddes, et. al. on the subject? You seem to be conflating phase and delay. I suppose the easy answer is that, if you feel it causes problems, then don't do that.
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So, I get what you're saying here and I agree with a lot of it, but most speakers that we use as mains do go just about as low as subwoofers. They just don't do it as efficiently. You can high pass your mains, but that doesn't get us away from phase problems, especially at the crossover region. Also, I'm not saying that correcting for frequency response causes phase problems. I'm. saying that having multiple subwoofers can flatten frequency response but increase phase problems. You can correct for the nulls, but what happens to the spaces that were working properly. My concern is that you can add more problems than you fix, but again, I've never tried 3 subwoofers in a room. I'm merely trying to understand why this is a better approach. The reality is that I would have to hear it and see if I like it. In my experience with multiple subwoofers (mostly in arenas and other systems where we use sub arcs to decrease modes and create a more even low end response, we often sacrifice punch and clarity.) I'm wondering if that's what happens in small rooms also.Aside from extending the frequency response of the mains, the main reason to add subs is usually to counter nulls, not flatten peaks. EQ is usually good enough (has enough range) to knock down peaks since they tend to be smaller, in the 6 dB range or so. I set up (crossover) my subs to operate below the range of the mains, and room modes generally fall below that range, so would not apply the same EQ to the mains (not needed). In general your sub(s) and main speakers will require different delays (or phase) to provide the best sound at the listening position.
Room treatment depends upon wavelengths so at bass frequencies becomes impractical (too large and thick) for most of us. You need very deep (thick) absorbers or diffusors (several feet). There are special treatments using resonators that are thinner but usually cost more and work only at specific frequencies. There are papers on broadband resonator (membrane) diffusors and absorbers but I have only seen a couple commercial products and they were pricey.
Any time you have more than one speaker there is the potential for phase problems. If you add a speaker (any speaker, sub or otherwise) at a different location and distance from the listener you will need to match the delay for cohesive sound. You can match phase at one frequency (and its harmonics) and that is often good enough if you align phase at the crossover point so mains and sub(s) are in phase at that point. Below that the mains contribute less, and above that the sub rolls off, so interaction beyond maybe an octave or so (depending on the rolloff rate) is less concerning. The reason for adding a subwoofer is to provide a signal phased to cancel room modes and such. It is not a problem, it is why we do it. Time (delay, "phase") alignment is required and can be done via a room correction program, outboard processor (e.g. PC program or stand-alone HW like a miniDSP or AntiMode), or controls on the sub itself.
I guess I do not understand your basis for assuming correcting frequency response can cause phase problems. You must time-align the subs, true, but adding subs should not cause phase problems unless you do not take that step to align them. Have you read papers by Welti, Geddes, et. al. on the subject? You seem to be conflating phase and delay. I suppose the easy answer is that, if you feel it causes problems, then don't do that.
I question applying different EQ to mains and subwoofers when they're operating in the same frequency range in the same room. Wouldn't they have the same problems in the room?
My basis here is that flat frequency is a great goal, but not if it sacrifices the listening experience in other ways (which I generally describe as phase problems). I see the same problem in some crossover designs where drivers sum flat but not in phase. When you add a subwoofer that flattens the response by canceling peaks but summing the nodes, does it not also effect other areas of the frequency spectrum and listening experience?
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