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Discussion Starter · #1 ·
I'd rather not use an EQ, partially because I don't feel like spending some big bucks on a good analog parametric unit but I'm curious if any of you know if building some tube traps for the rear corners would at least kill some of this room peak? It doesn't seem to be affected by moving the speakers around very much... definitely a room resonance but it's fairly severe and in a pretty bad mid bass spot, so a lot of music hits it (60-100hz).


Here's a graph of the room.


(separate, left, right and sub)




The room is 13'3" wide, 24' long (goes into the kitchen), and has 8' ceilings.


Think some hefty tube traps will tame this beast?


Thanks in advance.
 

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Quote:
I'd rather not use an EQ, partially because I don't feel like spending some big bucks on a good analog parametric unit
How about $100 for a cheap digital EQ like the BFD? Set your speakers to “small” (as they should be anyway), EQ the sub and you’ll be in business. And it won’t cost you any floor space in your room.


Regards,

Wayne A. Pflughaupt
 

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Quote:
Originally Posted by Turbo99 /forum/post/19571119


I'd rather not use an EQ, partially because I don't feel like spending some big bucks on a good analog parametric unit but I'm curious if any of you know if building some tube traps for the rear corners would at least kill some of this room peak? It doesn't seem to be affected by moving the speakers around very much... definitely a room resonance but it's fairly severe and in a pretty bad mid bass spot, so a lot of music hits it (60-100hz).


Here's a graph of the room.


(separate, left, right and sub)




The room is 13'3" wide, 24' long (goes into the kitchen), and has 8' ceilings.


Think some hefty tube traps will tame this beast?


Thanks in advance.

can you do time-dimension graph/measurements? e.g. measure decay time?
 

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Quote:
Originally Posted by Wayne A. Pflughaupt /forum/post/19573629

How about $100 for a cheap digital EQ like the BFD? Set your speakers to small (as they should be anyway), EQ the sub and you'll be in business. And it won't cost you any floor space in your room.


Regards,

Wayne A. Pflughaupt

eq cannot do anything to cure decay times, which he may be having severe issues with and just doesn't know it yet.


eq is not a proper solution but for $100 it may be worth a shot to experiment. but then again, it depends how wide his listening space is (e.g. is it home theater? or just a single listening position) ... eq'ing for one position and then moving a few feet could and probably will have drastic differences in response.


is that acceptable to the original poster?
 

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In my opinion, any typical subwoofer system in a HT can benefit from EQing down the inevitable peaks induced from room modes. Additionally, bass trapping can be very helpful to knock down some of the lingering effects with respect to time.

Quote:
eq cannot do anything to cure decay times

If LF ringing is problematic in room, then as it's addressed by whatever means, it becomes acceptable after it reaches a certain (x) level, at the (t) duration, then everyone's happy.


However, if the primary room mode is attenuated in magnitude with EQ, less modal excitation, and subsequently less magnitude with respect to time (t). So doesn't that illustrate that both EQing and bass trapping address achieving acceptable low levels of problematic ringing?
 

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Quote:
Originally Posted by FOH /forum/post/19573940


However, if the primary room mode is attenuated in magnitude with EQ, less modal excitation, and subsequently less magnitude with respect to time (t). So doesn't that illustrate that both EQing and bass trapping address achieving acceptable low levels of problematic ringing?

well, i said eq only - not eq + bass trapping.

the point i was attempting to communicate is that even though he's eq'ing down his peaks, he may have decay issues in the time domain that he's completely unaware of. so just looking at the response graph and deriving a solution based on that is not looking at the entire picture. he may have decay issues at a frequency .. but his mic/listening is in a null at that freq. so by his graph, he may think he doesn't have an issue at 100hz (example # only) because he isn't in a peak --- but he could have very long decay times at that frequency. bass trapping can help both of these issues (peaks/nulls, and decay times)


and for the price of a decent EQ, he could get a couple boxes of OC703 and DIY bass trap a decent portion of his room.


i guess i would recommend the OP take more graphs, especially within the time domain to further shine light on any issues he may have and may not be aware of? instead of strictly focusing on the response graph?
 

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Yes, you're right. One needs to look at everything.


I just can't imagine a HT system that couldn't benefit from some subwoofer EQ.


If an individual was considering purchasing an EQ to address response smoothing of LF, I would strongly suggest the Antimode, as a big step forward toward smoother, more consistent LF in room. It enables one that isn't that proficient in EQ, to realize some tangible results, at the push of a button.
 

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A parametric EQ will tame the sub’s response peak and bring its decay time back in line with what the rest of the measurement displays. But even if it doesn’t improve decay, just getting the peak in line with the rest of the response curve will result in an audible improvement.


What the graph downplays, since it was generated by measuring one speaker at a time, is that running the mains as “large” is only exacerbating the problem. With all speakers + sub operating together, each main speaker adds an additional 2-3 dB to the 70-90 Hz problem.


Regards,

Wayne A. Pflughaupt
 

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Quote:
Originally Posted by FOH /forum/post/19574646


If an individual was considering purchasing an EQ to address response smoothing of LF, I would strongly suggest the Antimode, as a big step forward toward smoother, more consistent LF in room. It enables one that isn't that proficient in EQ, to realize some tangible results, at the push of a button.

i suppose it probably is the easier way, but it's still a bit of a "band-aid solution for a flesh wound"


i guess the original poster needs to chime in with what his design requirements are. is he looking to do the job properly or just apply a band-aid.


and eq still will only provide a flatter response in one position. moving inches or feet can have drastically different responses. so that's up to the OP to decide as well whether it is one listening position or maybe 2 rows and he needs to accommodate for that.
 

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Quote:
Originally Posted by Wayne A. Pflughaupt /forum/post/19575153

...What the graph downplays, since it was generated by measuring one speaker at a time, is that running the mains as “large” is only exacerbating the problem. With all speakers + sub operating together, each main speaker adds an additional 2-3 dB to the 70-90 Hz problem...

Nice catch there, I didn't even see that on first glance but you are right, he needs to be running his mains "small".
 

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Quote:
Originally Posted by Wayne A. Pflughaupt /forum/post/19575153




A parametric EQ will tame the sub’s response peak and bring its decay time back in line with what the rest of the measurement displays.



how does an EQ have anything to do with decay times? they arent 100% linear correlation. just because he eq's some of the LF down to be a bit more flat/in-line with the rest of the response, that in no way shape or form effects decay because decay is dependent on the room. granted, less energy at that frequency will obviously provide less energy to decay, but it's not linear. so if the response at those peaks is brought down, how can you say (without even knowing his room or seeing time domain responses) that "decay time will be brought back in line" ??? he could fix his peak at 90hz but still have 450ms decay time --- it's still going to cause huge clarity issues.



Quote:
Originally Posted by Wayne A. Pflughaupt /forum/post/19575153

But even if it doesn’t improve decay, just getting the peak in line with the rest of the response curve will result in an audible improvement.

sure, but im still confused why you are pushing a parametric EQ as the primary solution.


imho, the proper solution is to tame some of the acoustic energy in the room and then finish it off with EQ adjustments on the LF side. (e.g. icing on the cake).


i feel that your recommendation of an eq (alone) to fix this is lacking the proper thought about the fundamental issues with the room. it's taking a very simple approach that, again, acts more as a band-aid than a true, scientifically thought out solution.


also, eq can tame peaks because peaks are generally +6dB or so, but nulls can be essentially be much much worse. how would you use eq to bring back frequencies if he is sitting in a null? again, proper bass trapping will help alleviate this issue as well.


but it all depends on the OP's design requirements. maybe he has 1 chair (small listening sweet spot) so eq will be sufficient for his needs.
 

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Discussion Starter · #13 ·
This is doubled as a HT, but primarily all I'm concerned about is my one listening position because it's only bothersome when I'm listening to music (which I do a lot). The room is already treated with OC705 24x48x4 traps mounted at the first and second reflection points, 24x48x2 traps mounted directly to the sides and just behind the mains (side walls), and with two 24x48x4 traps on the rear wall.


The only thing not treated in this room is the corners and the ceiling.


I was just curious if you thought building some hefty tube traps would do some damage to the peak. Was looking for more of a yes or no answer instead of getting super technical about it.


I can build floor to ceiling 24" wide tube traps (or superchunk) for about 100 dollars a corner, so it's a matter of whether or not you think 200 dollars would get me a reasonable amount of improvement.


Thanks again.
 

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Generally the "traps" available do not provide much benefit below 100Hz. Your mains have horrible response at the seating location with modal response starting at about 500Hz. Bass traps will provide some benefit in that region. Do not run your mains as large. As well, your subwoofer volume and L/R main volumes are not matched and your mains are not level matched to each other. At 4kHz you have a timbre mismatch between the two front speakers ... possibly caused by an SBIR notch.
 

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Discussion Starter · #15 ·
I don't really have an option to not run the mains as large because it is a 2 channel setup and I do not run a processor. This is run strictly on a separates preamp and amp setup.
 

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Quote:
Originally Posted by Turbo99 /forum/post/19576209


This is doubled as a HT, but primarily all I'm concerned about is my one listening position because it's only bothersome when I'm listening to music (which I do a lot). The room is already treated with OC705 24x48x4 traps mounted at the first and second reflection points, 24x48x2 traps mounted directly to the sides and just behind the mains (side walls), and with two 24x48x4 traps on the rear wall.


The only thing not treated in this room is the corners and the ceiling.


I was just curious if you thought building some hefty tube traps would do some damage to the peak. Was looking for more of a yes or no answer instead of getting super technical about it.


I can build floor to ceiling 24" wide tube traps (or superchunk) for about 100 dollars a corner, so it's a matter of whether or not you think 200 dollars would get me a reasonable amount of improvement.


Thanks again.

i haven't built my superchunks yet, but am so in the next few weeks --- but those will have far more effect on LF and decay times than your thick traps on the walls. bass trapping at the boundaries is most important, as that's where pressure builds (all corners, ceiling, wall, floor, etc)... the ceiling is very important too (another big reflection point). and you can calculate what modes you have for the ceiling (you could be sitting in a peak or null or somewhere in between) - so some trapping hanging from the ceiling will help as well (broadband, since it will be functioning as a reflection point absorber too)
 

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My thoughts:


measure the combined output. You might be lucky, or well designed, and have that peak cancel out. If they are out of phase you might even end up with a null!


I'm surprised by the low freqeuncy peak in your mains - do you have them in corners?


You do need to look at time response.


4" thick panels will not help much. Load as many corners as you can with absorption as thick as possible.


Your peak might be a vertical mode, in which case you probably want to use floor (or ceiling) and wall corners. I have several large blocks of 703 disguised as benches - I could probably use more. Think big blocks of fiberglass. Or tuned absorbers to capture the primary room modes.
 

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Kinda moot since the OP says he can't use EQ, but...
Quote:
Originally Posted by localhost127 /forum/post/19575391


how does an EQ have anything to do with decay times? they arent 100% linear correlation. granted, less energy at that frequency will obviously provide less energy to decay, but it's not linear.
Fortunately, reducing the energy of the peak is all that’s needed to improve the sound quality of the subwoofer. Decay issues or not, every case I’ve seen where someone eliminated a peak with EQ they said it sounded better.
Quote:
so if the response at those peaks is brought down, how can you say (without even knowing his room or seeing time domain responses) that "decay time will be brought back in line" ??? he could fix his peak at 90hz but still have 450ms decay time --- it's still going to cause huge clarity issues.
Don’t confuse “decay time” with the rate of decay. Decay time is largely dependant on SPL levels (you can make decay times “look” better merely by taking a measurement at a lower volume), so reducing a peak will quite naturally bring its decay time generally back in line with what the rest of response displays.
Quote:
sure, but im still confused why you are pushing a parametric EQ as the primary solution.


i feel that your recommendation of an eq (alone) to fix this is lacking the proper thought about the fundamental issues with the room. it's taking a very simple approach that, again, acts more as a band-aid than a true, scientifically thought out solution.
You’d be surprised how many people are unwilling to deal with reconstructing an existing room, or filling it with thousands of dollars of panels and traps, to the extent that would be required to adequately address low frequency ringing. Band-aids are cheap and reasonably effective.
Quote:
also, eq can tame peaks because peaks are generally +6dB or so, but nulls can be essentially be much much worse. how would you use eq to bring back frequencies if he is sitting in a null?
I’ve never had any problem taming peaks of 10 dB or even more. Actually, true nulls are not that common. Bass is omnidirectional, so in most cases there are ample reflections present to swamp a null. This is why most depressions in response can be address with EQ.
Quote:
again, proper bass trapping will help alleviate this issue as well. but it all depends on the OP's design requirements.
As Dennis noted, most traps have little effect below ~100 Hz, which is where the OP’s problems are. By the time he got enough traps in the room to alleviate the problem, he’d have to sit outside the door.



Regards,

Wayne A. Pflughaupt
 

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^^^


Ethan,

Remarkable...what were the details? That's significant.
 
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