How do I control specific frequencies?

Howdy all, I could use some help diagnosing and solving another audio problem. I've noticed that while listening to several albums (in this case, CDs), there are certain bass frequencies that are super loud and seem to overpower everything else. I'm hoping to tame them if possible.

So here's what's happening: While listening to a few CD's (Metallica's Justice, Pantera's Vulgar) at a reasonable volume for listening to Metal (LOUD! ), I've noticed that certain parts of songs have unpleasant "woofing" bass that overpowers the rest of the music. It sounds unnatural and my ears can "feel" that it doesn't sound right. Using a simple frequency analyzer app from my phone (I know, not accurate, but it's all I got), it seems to be concentrated around 125-150 Hz at -25 to -20 Db. Is this a common phenomenon? If so, how can I correct it?

My first assumption is that it's inherent to the album, being poorly mixed/mastered, and that there is little to be done, other than turning the volume down . This seems to be a common problem for Metal...poor production.

My next thought is correcting room acoustics...adding bass traps. I have added some acoustical treatments (OC 703) and it has helped clean up other problems and allowed me to better hear what my speakers are doing. It helped so much that I dumped my Klipschs, got some KEFs and am much happier.

My final "guess" would be better isolation. I don't really have any; don't know where to start.

Any suggestions or advice would be greatly appreciated. If this has been discusses in another thread, would someone kindly point me there? Thanks for all your help!

 

I'm assuming you mean there are peaks around 125-150Hz ...? If they're 20dB HIGHER than the rest of the spectrum that would make sense. Yes, then bass traps seem to be in order. I think most bass traps absorb pretty well, that seems like 'upper' bass to me. I see you have a 30 x 15 room ? In that room, ~75Hz and ~150Hz are (multiples of) fundamental frequencies and the length is 2x the width (exactly). This will 'amplify' the resonances giving a large boost at those frequencies.

In the 22 x 18 room, 51 and 63Hz are fundamental, 102 and 126 are harmonics, so these can be 'boosted'.

If you want to try EQ that may help as well ... (there are those that insist that room treatment is the ONLY way to go ...).

 

This might work for you . Firing your speakers across the shorter distance of your room but far apart as possible. Also to have lots of furniture (carpet, cushions, rug etc) in the room. Good luck.

 

We used to solve these things with a parametric equalizer - not a general equalizer. The best units have a microphone so you can tune the system and the room to flat response, or any response you want, at least at one point in the room. I can't recommend a particular model now, since I haven't followed what's out there now.

 

You didn't detail what you are listening with, but smaller speakers (such as ones that come from Framingham, Mass) often make up for lack of deep bass by over-emphasizing boomy midbass, which is good enough for fooling the rubes.

There isn't much you can do to improve specifically midbass with room treatment. You can bring back some deeper bass by placing the speakers right against the back wall, and turn down the bass tone knob (which often are centered around a 100hz instead of the 50hz we'd want).

Since it is particular recordings, rip the CD on your computer. Free Audacity software has equalization (under effects) - take 3dB out of 125 or 160hz, and make yourself a new CD. That might let you determine if it's worth picking up a basic graphic EQ unit to put between your CD deck and receiver.

 

I recently changed speaker wire from stranded to solid core 16awg and it really cleaned things up as my system suffered similiar problems.
Does the cd sound ok with headphones? Don,t use them anymore, but they can sometimes be useful.

 

Ditching Klipschs for KEFs ? Oh man ! Klipschs are ideal for metal ! Did it not occur to you that bass peaks might have been caused by poor placement of the speakers ? They have 12¨passive radiators so they have to be placed away from walls.

 

Thanks for everyone's replies and suggestions; this is exactly the help I was hoping to find.

Here's a little more information to help fill in details I left out. The room is 22' wide by 18' deep, with the set up being on the longer 22' wall; the walls are painted sheetrock with minimal pictures, etc., on the walls; the floors are laminate hardwood (over concrete) with a few rugs. The speakers area roughly 9' apart and my listening position is about 11' from the setup (which is between the speakers). The speakers are about 2' from the wall and toed in and spiked; behind the speakers are 2 acoustical panels. My listening position is about 3' from the back wall, which has another panel. The other 2 panels are on the first reflection points (all of the panels are 2'x4' and 2" thick). The left speaker is about 3' or so from the corner, but there is no corner on the side with the other speaker (it opens up into the rest of the house). The gear in this set up is my Technics TT, old Sony ES CD player, Conrad Johnson PV7 tube preamp, and a Crown XLS 1500 power amp connected to KEF 104/2 speakers by Cardas 101 (14 gauge) speaker wire. I have heard this unpleasant "woofing" on a few LPs and other CDs, but I guess it really caught my attention recently with the 2 previously mentioned CDs...that's when I decided to "measure" it with my phone app. The CJ preamp does not have any tone (bass, treble) controls.

Rick58, yes, I believe that's what I'm trying to describe...a peak at 125-150. When I hear the "woofing" or whatever it's called, that's the point where it's really jumping on the frequency analyzer thing. Would you, or anyone else, mind explaining what "fundamental frequencies" are, or point me to something that explains it? This is totally new to me and I would like to understand more. I am not against using an EQ, just don't have one. The CJ doesn't have any way to adjust bass, etc. I'm planning on building bass traps this summer and was thinking that might help.

Harby, I hope I've provided some useful information here. The KEFs are kind of "not small," and I do get enough deep bass from them. The CJ doesn't have any tone controls to play with, unfortunately. Great idea about ripping the CD with Audacity, thanks!

 

The preamp doesn't have a headphone section, and I rarely listen to headphones. I think the Sony CD player has a headphone input, but I've never used it...but I will now! Thanks for the suggestion.

 

HA! You were the first person I thought of when I was typing that! Believe me, I tried and tried to love the Quartets, since many, many folks said that were great for Metal. I even built the acoustic panels because I thought it would make them sound better. Turns out, it only amplified the problem: too much high end treble and listening fatigue...and that HONK! It was killing me. I switched them with my Focals from my AV setup and BAM! All my problems were gone! But I needed the Focals back in the other setup, so I picked up some totally restored KEFs and I absolutely love them. I think those Quartets are great speakers in the right room...just happens it does work well with mine. To be fair, I haven't used the Quartets with the CJ tube preamp (I only recently picked that up), so that might change things...but those KEFs do Metal very, very well!

 

Well thanx for that I guess !. Yeah interaction with the room can be a bitch

 

Those KEFs don't have a rear radiator or any special voodoo, they have an internal pair of woofers that play into a fourth-order single-reflex bandpass box with a port out the front, electrically crossovered at 150hz. This is a somewhat strange design for a high-end speaker, because this type of enclosure doesn't just low-pass, it also accentuates around its port bandpass resonance frequency (which is also likely designed close to the crossover frequency).

The pros to the design are that the speakers mounted in opposing directions cancel out their directional excursion distortions, and the bandpass muffles higher order distortions.

Extend the port length another few inches to lower the bandpass and you have created a mechanical "notch filter"... doubt you want to experiment with modding the speakers though.

The wavelength of 200 hz is 6.5 feet. The distance between the speaker baffle to the wall and back is about 6 feet. The wall-reflected bass wave will reinforce around 200 hz, and cancel at other frequencies. The same effect with the wall behind you. I would move the speakers closer to or against the wall, or at least not listen with the wall behind you at identical spacing.

The acoustic panels probably don't absorb much in the bass frequencies, and the speaker's tweeters will be directional anyway (no treble from the speakers to the wall), so placing panels behind you might be a better choice. It sounds like you have an otherwise bright room with lots of hard surface.

 

Is the booming consistent throughout the room? Or is it localized to corners and near walls?

 

You were using Klipsch speakers with a solid state preamp and a Crown power amp? God help you.

 

F2s+Pioneer SX-980 =sweet, crisp, detailed sound. No need for those light bulbs on a chrome chassis.

 

Is the boom everywhere in the room or mainly at the listening position?

Walk around the room to hear where in the room it is boomy. You might be sitting on a mode, boomy spot.

Also as suggested start with placement. It is the cheapest adjustment. Try adjusting the distance from the side walls and from the front wall. Move one direction at a time then test, or listen for changes. Get the placement first then adjust your panel placement.

 

I had the same problem and after trying everything a sound engineer friend got hold of a DSP and with his help and the use of his knowledge i no longer have the "bass boom" problem. It occurred on a few cds and on a lot of Vinyl. George Ezra for example was unplayable but now all is resolved. The problem is the room and no amount of treatments would resolve it.

 

Ok, so I have no idea about anything you just said, but it sounds good. Where can I go to get a quick tutorial about "forth-order single-reflex bandpass" or crossover frequencies, or any of this stuff you just mentioned? I really don't understand much of this, but I would like to learn. From what I'm gathering, you are suggesting to either move the speaker closer to the wall, or to move my listening position, because the wavelengths...(please fill in the blank).

As for the panels, how many and where would I place the panels behind me? I have one directly behind my listening position. And yes, the room is rather bright with a lot of hard surfaces.

 

Good question. I would say I hear it more coming from the left side, the speaker that is nearer the corner.

 

I was previously using the Quartets with a Marantz 2270 and sometimes a Sansui 2000x. I've only use the tube preamp with the Crown and it's a great combo.

 

Hey Kyhl, great to hear from you again. That's an interesting question as well. I will try walking around the room and comparing it with where I normally sit. Thanks!

Is this a common problem that other listeners face...sitting on a "mode" or a boomy spot? Is there also a counterpart for sitting in a harsh/treble spot?

 

What is a DSP? How does it work and how did it help fix your room?

 

All rooms are different. It can be a problem if you are unlucky. Some may luck out and miss modes and nulls.

The other option may be that the speakers have a resonant frequency that is causing your issue. If so, you may find that the bass is the same all around the room. So the cheap test is to walk around the room and see if the problem exists all over, as @timind first suggested.

 

DSP Digital Sound Processor. My mate from BLACK SEA AUDIO tried bass traps and various other treatments with little effect. He used a computer to measure which sound waves were distorting the bass and then programmed the DSP to cut out those frequencies. I have 4 different settings which we called "flat" "warm" "mod" and "normal" . Each setting except flat cuts out certain frequencies and has no impact on the overall sound quality but now a few discs and Vinyls that were distorting are now sounding great. Check out his sight; worth a look. Karl is VERY helpful

 

Thanks for sharing Fish, glad to hear it worked well for you. I googled around for DPS, but not sure what kind of device I'm looking for. Is it something like a rack mounted piece of gear? I don't have a computer hooked up to my system, and it's pretty much all "vintage" stuff, with no USB's, etc. How does the computer measure the sound waves? Does it use some sort of external microphone? Sorry for all the questions. I've had other people suggest something like that before, but I never really understood much about it...and again, I don't have equipment that connects to PC's, etc.