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Help me tame my out of control bass

Hey all,

Hoping to get some advice on how to tame what appear to be some pretty bad room modes. See my system here:
https://systems.audiogon.com/systems/8800

I’m in a bit of a pickle for a few reasons. First, my NY apartment is on the small side and requires me to set up on the long wall with the listening position against the opposite wall. On top of that I upgraded to my dream speakers, Egglestonworks Kivas. They sound amazing but they’re big and have a lot of low end reach. The combination of these two factors leads to the waterfall you see in my system - a pretty massive bump in low end, particularly at 40-44hz and from 60-70hz.

There’s also a huge bump at 120hz, but I don’t understand how that one is possible. I think that might be a measurement or microphone error - I don’t hear that at all and it doesn’t go away even when I EQ 120hz out completely, but maybe it’s a resonance?

Things I’ve tried so far, each with modest success:
- Plugging the ports gave me about a -5db reduction in the trouble spots (all measurements are with the port blocked)
- I don’t have a ton of placement flexibility but moving them back from their original position gained me about a -3dB reduction in bass
- I added a pair of 5.5” thick GIK bass traps, but they didn’t do much that I’m seeing in the measurements. Maybe a -1-2dB reduction, tops. They honestly helped more with the mids and highs.
- Convolution curve in Roon - this works the best, but doesn’t solve the problem for home theater or vinyl

I’m pretty stumped as to what else I can do. I think that the amount of bass traps needed to fix this is more than my marriage can withstand. I’m considering the PSI AVAA active bass traps, but only if I can do a home trial of them first to see if they’ll actually help - I worry this 8-10dB bump I’m seeing will be too much for even a pair of those. I could get a DIRAC processor from miniDSP and that would at least then work for all digital sources. Vinyl is mostly not a problem since this is so low and most of my vinyl is rock and jazz.

Any other ideas? Rolling tubes that have less bass? Are there any less expensive EQs with digital in and out that I could use as an alternative to the DIRAC for home theater only?
hudsonhawk
59 responses Add your response
erik_squires
15,877 posts
 
I wonder if you have a ground loop from your test signal source? 
audio2design
1,351 posts
 
Odds are the microphone/mic-input is picking up 60Hz and rectifying it (hence 120Hz).
oldhvymec
5,101 posts
 
Hummmm, Maybe that's why I've never see one on my stuff. 2496 Behringer, it's their mic, it's all their stuff. Your saying the equipment the mic is hooked to may have a ground loop? AND that through rectifying it, that causes that spike.

It doesn't sound so "Rectified" "To be made right" A2D
Can you hear a spike like that A2D, or Erik?

OK I'll DMDD, I'll learn.. Maybe:-)

OP, can you hear that narrow spike?

Maybe I need to see if I can make it happen, and give it a listen..

I guess I'm lucky.  I have been in the same home for 40 years,  May..

Regards
lemonhaze
410 posts
 
OP, ignore the comment from @mijostyn that 'bass traps don't work' This is blatantly wrong. Bass traps most definitely work but the 5" thick panels GIK supplied are not proper bass traps, they form broad-band absorbers and are very useful. They are in business to sell so be aware of being sold too many absorbers which will dull the room down.

I see about 10dB between nulls and peaks which really is not too bad. Looking at the CSD you provided I don't see the 120Hz peak being any higher than the other peaks. The suggestions to use EQ to boost the partial nulls will bring no you no happiness. Using EQ to pull down the peaks will work BUT only for one listening position which is rather restrictive.

As I am sure you know, to gain 3dB, it takes a doubling of power. I don't know how loud you listen but to gain 9dB of boost you would need to double the power into the speakers 3 times, so if the 88dB speakers are using about 60 watts average on peaks, then to bring the nulls up to that level would require 480W. If the amp can't provide 480W clean power then it will clip and when it clips the wave begins to take on a square shape and a square wave is just a sine wave with harmonics. Danger!  Harmonics are higher multiples of the fundamental so the crossover does it's job and sends high frequencies to the tweeter which is not designed to handle that kind of power and it politely fries itself.

If the missus won't allow full sized super-chunk bass traps, take heart, you can employ a Distributed Bass Array. Read up on Geddes and Toole on multiple subs and how to deploy them. This will smooth out the modal region below the Schroeder frequency and you will no longer be confined to just one spot. With a smooth power response the whole room sounds good. The 3 or 4 subs recommended randomise the nodes and you get many more but smaller partial nulls and peaks. Needs to be heard.

A DBA is great but although you now have smooth bass it still needs to decay within the correct time for your size room and this of course will need bass absorption. Gearslutz was mentioned and has an acoustics forum with much good info.



analogguy
4 posts
 
I wonder if you're getting to much bass reinforcement from close placement to the wall behind them. If possible (as an experiment), pull them out so you have 24 to 30 inches of space behind the cabinet and see if that evens out the response. If that helps, and living accommodations require close placement to the wall, it may be possible to place a bass trap directly behind the port at the bottom of the speaker and allow your current positioning. 

The other possibility is - Eggleston has great bass to begin with and the Kiva's may be too large for your space...
jazzguy43
33 posts
 
try a jl112/3 or a velodyne dd12/15. locate it on the same wall as your listening position but a ft or 2 out into the room. reverse the polarity on the sub then tunre w/phase control on sub. You will be amazed at how the room will flatten wrt bass response. I have eq curves I can share w/you showing how the room modes become less dominate. This a a solution, the other solution is to get smaller speakers like Harbeth M30.1 or .2s w/a sub.

Happy listening.
pmiller115's avatar
pmiller115
95 posts
 
Like many of us, I have also struggled with bass - too much, too little, uneven room response, etc. I recently purchased some Townshend Seismic Podium isolation devices. These are essentially steel platforms with spring loaded adjustable cylinders at each of the four corners of the platform. As much as I had followed somewhat conventional thinking and had spikes on my speakers I decided to give these things a try. I must say they positively transformed the performance of my speakers (Linn Akurate floor standers). The bass problems have been dramatically resolved. They are not cheap but they really do tame the bass and I could not recommend them more emphatically. Try an outboard bass equalizer along with these "podiums" which were reviewed in the Jan., 2021 issue of Absolute Sound. This article also contains contact information for the US distributor who is located in S. California and was very decent to deal with. 
audiophilenm
6 posts
 
This is a classic example of a system that can benefit from a properly integrated sub. In almost every room there will be a place where the speakers image best and have the most even natural response above 150Hz. There will also be a place where the speaker’s bass response will be the most even. I have yet to work in a room where those two places are the same. You likely don’t have the floor space to optimally place a sub, so there will be concessions.

In my experience, proper listener and speaker placement is always preferable to any amount/type of EQ, but your hands are tied. You’ll have to work with EQ to tame this, but try to use the absolute minimum that gets you an acceptable balance between engaging sound and a resonant mess.

And anything that you do to try to fill in dips in the response using EQ will be a disaster! What you’re seeing in that response curve is cancellations and emphases. If you can knock the peaks down, even by 1-2dB with better placement of speakers and listener (stay away from that back wall as much as possible), it should also bring many of the troughs up. You’ll be chasing a series of tiny victories that will add up to the best your system will get in that room.

I suggest that you try using a more acoustically transparent plug for the speaker ports, as the ones that come with most speakers are so dense that they create enough back pressure to stifle the natural sound of the driver(s) that share the port cavity. This won't help the excess bass but it will likely improve the overall sound.

I agree that the best way forward on the 120Hz issue is to do a nearfield measurement of each speaker separately to see if the issue is with your speakers, mic, or a room resonance. Common room resonances are often caused by light lamps, wall sconces and recessed light fixtures. If you have a signal generator, input a 120hz (+/- 5Hz) steady-state sine wave into the system and you’ll likely find the problem pretty quickly.
hudsonhawk OP
137 posts
 
So an update here: nearfield measurement shows the speakers, unsurprisingly, have an almost flat response.

And massive kudos to those who said the 120hz spike was a harmonic - you win a prize for that one. When generating a 60hz tone, the spike at 120hz is visible on the analyzer. Very interesting!

For now, I’ve been able to do a little EQ’ing to address the problem, at least with music played from my music server. Interestingly I didn’t really like the results when using a convolution curve in Roon - it reduced the bass way too much - and I ended up just using Roon’s parametric EQ, using the room’s graph for reference.

Longer term, I’m arranging a demo of the PSI AVAA C20, and waiting to see what happens with our lease before deciding between that and more bass traps.
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