What Is Comb Filtering & How Does It Relate To Room Acoustics? - www.AcousticFields.com
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- čas přidán 12. 09. 2024
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- - Today we’re going to talk about comb filtering and how it affects you. Comb Filtering is a series of unwanted reflections between a speaker and any surface. It’s a series of back and forth reflections that are trapped mainly from middle and high frequencies.
So in today's video you'll learn:
1. Why your equipment rack could be causing this right now in your two channel setup,
2. Why you need to be beware of the comb filter off your console in a recording studio setup and
3. Why the center channel in your home theater setup could be the culprit.
So enjoy the video and as always please let me know if you have any follow up questions.
Thanks
Dennis
P.S. Sign up for my free room acoustic training videos and ebook at www.acousticfie...
This video wasn't just valuable to me, it was invaluable to me. Thank you! So many questions answered from past events because of this one video.
M, Thank you. If you have any other topics you wished covered, send me topics to info@acousticfields.com
What you are describing is a Comb filtering effect, not a comb filter. A comb filter is a device that delays a signal so it either destructs or constructs a signal. Fo example a noise canceling headphone works by sampling ambient sound, run it thru a comb filter, or phase shift (simple inverting) that delays this ambient sound by 180° and introduces it into the audio stream to cancel the ambient sound. Adding a phase shift of 180° to a signal will cancel the signal out. You can make a 60hz hum filter by the same method.
A signal that is slightly delayed, by speaker placement etc. will distort the original signal which is what you are describing here, but its not a filter, its an effect.
I don’t get it. How does putting two floor standing speakers next to each other on each side not create comb filtering?
Thank you so much! For a while I thought my TV speakers were bad, but I had 'em right up against the wall!
The difference is great. This is a good example of the power of comb filtering.
As always, geart insights from the master himself, Dennis. Thanks for educating us. And since we are in the comb filtering topics, can you share some insights how comb filtering may happen between 2 drivers, the woofer & tweeter, and 2 tweeters, mainly for speaker DIYers, because this happens a lot too in my experience with speaker DIYers.
Hi Nelson de Leon
The radiation patterns of speakers must be addressed in all speaker designs. The cabinet refractions themselves must be a nightmare to deal with, let alone the interaction between the physical drivers themselves. How about the crossovers? Getting three speakers to sound like one? Yikes! Some designers have it figured out but most do not, thus all the different manufacturers. Since the speaker, in my opinion, is the weakest link in the sound producing chain, it is time for a new approach.
How are you? Long time no speak. How did the BDA build progress for you?
Thanks
Dennis
Hi Nelson de Leon
How are you? I answered your question in a little more depth in this weeks Google Hangout. You can see your answer here:
czcams.com/video/4tHfHH0_7Jg/video.html
Thanks
Dennis
This was very helpful and informative. Thanks man! :)
Thanks Dennis, I now understand the effects of comb filtering (I think!). Thanks once again. Regards, Mike.
Thanks for sharing your knowledge.
Great channel...as always. Thanks!
Great explanation and demo
B, Thank you. Think of comb filtering as "no filtering". Its all noise and usually in the middle frequencies right in vocal range. Exactly where you don't want or need it.
That was super great thank very much.
Thanks, I will be taking my equipment off my speaker height stand and I will be moving them to the floor.
Blacklightning die you haar a differente?
so how do i set my PC monitor(screen) regarding to the speakers , and how do i set the speaker regarding to my desk (console)
Osama Said El Sayed
Remove the monitor from between the speakers and hang it on the front wall. You may have to get a larger monitor but the sonic improvement will be well worth the additional screen cost.
Thanks
Dennis
Okay ... no rack between speakers when rack is high and in line with speakers.
How about 2 sets of speakers that are close to each other? Will that be an issue? If so, how far apart should they be or it’s best never to set up in that manner?
TQ!!!
Speakers are never designed to be positioned next to each other.
@@AcousticFields ... got that! Thanks
I have a topic
Wires
Why is it that you spend tons of money on top notch speaker wires from the amp to the speakers but inside the cabinet there's very cheat wires. What effect does this have on the sound and what are the benefits of changing the internal wiring of the speakers ????
Great question eonblue2112
You are correct. The signal path quality you describe is critical and in the past cheaper cables were used. With such short lengths, I do not see it being as critical as an amplifier to speaker connection length, but quality is a concern.
Most speaker designers today, at least the ones I know, use quality hi - fi cables. I know cable manufacturers that build their own cable technology into cables to meet the speaker designer's specifications.
Thanks
Dennis
eonblue2112
How are you? I answered your question in a little more depth in this weeks Google Hangout. You can see your answer here:
czcams.com/video/eJGjC_R0C-k/video.html
Thanks
Dennis
Very helpful video, thanks a lot! I was just wondering if this phenomena is an assembled word for all different types of sound reflections you would get from any kind of angle? Because at first it sounded like the phenomenon only happened if your sound source and its reflector reflected the same sound many times (it would go back and fourth as it did in the monitor and equipment rack example) but in the console example there was only one reflection drawn from the speakers to your desktop and then to the listener. Does that happening give you the same result and is that happening also called comb filtering? Because if so the comb filtering phenomena is something that you never can get rid of? I mean you're soundsource and its reflections are always gonna hit some angel in some way. Because you cannot be in a room without angles or reflections? And your only way to diminish the happening is by reducing the amount of angles? Im just checking to se if I've understood you correctly!
I, Angled boundary surfaces can impact middle and high frequencies. They have the greatest impact at the listening position.
M much of what you describe is a type of phase cancellation
A room is a large phase inverter.
Dear sir where i have to place video monitor(mine 22") between speakers in my home studio to avoid comb filtering .if I put little angled towards ceiling and one foot behind (center of speaker's) Thankes
M, I will need to know much more about your room. Fill out the information in this link:www.acousticfields.com/free-room-analysis/
I always wondered about doing a left and right for the center, rather than a single speaker. . . would they be double mono??
D, Yes, we do it in our theater builds to keep the center channel in the vertical domain instead of the horizontal domain to fit under a screen. Placing a center channel, horizontally under a screen, when the left and right are vertical is the most crazy thing I have seen. It makes no acoustical sense creating phase and sound field irregularities.
@@AcousticFields Many home theater processors offer a "Phantom Center" mode that includes the center channel content in the signal that is routed to the primary L+R speakers, negating the need for an additional set of L+R speakers. While this reduces comb filtering due to reflections as described in your video, it introduces comb filtering due to the monaural sound traveling different distances between each speaker and each ear (acoustical crosstalk). For mitigation, do you recommend room treatment (e.g.- diffusion) or signal processing (e.g.- phase decorrelation)?
Dear sir, this is very helpful. But can you give me some advices on how to maximize my bedroom playing? I playing my guitar with a 1w amp with 8 inch speaker. If i place it on top of a chair i lose bass and gain more treble which i dont like. I need more mids and bass, i want to eliminate those treble that makes my sound thin. How should i set my amps position? Thanks.
G, You will have to move your amp around in the room until you find a spot that has less modal pressure. Try different positions starting at room center.
is there any distortion issues between the speakers itself?if so how it can be manajed?
A, Speakers are the largest source of distortion in the whole signal chain. They have phase, cross over , SBIE , all types. We need a better way to produce sound and the music within sound.
What do you say about stacking speakers like a tower. I have two 18" subs on top of another stacked, then putting a 12" inch Speaker on top of the sub and then adding another 12" speaker on top of the speaker making it like a tower. I have this on each side of my DJ booth. Do you recommend this? If not, what do you suggest to get the most out of my Powered speakers.
I Use Yorkville LS800P
EV ETX 18SP
Then two EV ELX 112P stacked one on top of another
E, I would make all the subs you are stacking the same manufacturer,
and same number and diameter of drivers. Elevate the first sub at least 24" off the floor.
@@AcousticFields thank you for the response! And regarding stacking two 12" inch Speaker on top of another won't cause issues of phasing? Since I want to gain the most out of the Highs from the speakers
E, keep each stack the same manufacturer so the driver speed is the same. make sure they are all 12's, 15's and 18's. Do not mix the sizes.
@@AcousticFields Sounds great! What would sound better, the 12" tops stacked on top of another or would you have them on a dual pole stand side by side on top of the subs
I understand this vid is mostly about mid to high freq comb filtering, but can anyone give me any tips on how to tackle comb filtering (assuming that's what I'm experiencing. It's some kind of reflection or phase cancellation I think) in the sub frequency ranges, mostly around 20-60Hz? I've built a bass bin using a good quality old 12" Celestion bass driver, and used the Thielle-Small parameters along with advice from Celestion themselves to get a box that's tuned & measured for this driver (front ported, tuned to 30Hz). First test of the speaker was great, and this thing goes low without even having to drive it much. The response definitely isn't flat, there are a couple resonant peaks but not major. The biggest problem is that in certain areas of the room, the sound almost completely disappears. There's one area in particular where you can't miss it (it's literally like "a pocket of anti-bass space"). Move your head into it and the bass is gone, move your head back, and it's bass time again! Can anyone give any advice on what I can do about this? It may well have something to do with placement, although AFAIK, bass is omnidirectional, unlike mids & highs.
Thanks to any hifi gurus or speaker builders who can help me.
N, If its low frequency, it is more a size/volume/ usage paradigm. You have a low frequency generating source that produces frequency and amplitude that won't fit into the room volume. Unwanted low-frequency pressure areas will room load depending upon SPL. frequency, and room dimensions. There are two treatments: New room size and volume or diaphragmatic absorption.
Interesting, it is in quite a small room, with a lot of furniture & appliances close together! I can't do anything about room size or room volume at the moment (most of whats in here is essential) but I'll look into diaphragmatic absorption and any other possible acoustic solutions. I saw you have a video on those absorbers so I'll check that out. Thanks for the pointers ;)
N, Front and rear wall coverage with diaphragmatic absorption.
Trying to figure out why literally none of the pro mixing engineers do this. Like look at Dave pensado, one of the most respected long time people in the industry. His speakers are directly next to each other. Nothings angled down as well.
A, Near field monitoring takes many forms. It depends on distance to side walls, room volume, usage, desk dimensions, and pressure level used. There is no one size fits all. Be careful when you say everyone uses it, it must be right. A lot of studios use building insulation to manage reflections without any concern for proper rates and levels of absorption for music and voice. Eighty million people smoke cigarettes, that does not make it right. Do your own thinking.
Wonder what Dr. Floyd Toole would have to say about this
Nopal wrong no clue laugh out loud
Edm producers: is that a threat?
T, Yes and no. If it is middle and high frequencies then yes. Frequencies below 100 Hz. no.
Riddim
S, Comb filter is important for rhythm and anything else that requires critical evaluation.