The subject of equalizers has been brought up a lot lately. As most audiophiles will tell you, the best route for an audio signal is the simplest path possible (source, preamp, power amp, speakers). That is to avoid the use of tone controls and equalizers when ever possible and avoid surround similators echo effects, etc. all together. These devices have a much greater potential for harm than they do for any good. Also, to truly adjust an equalizer properly takes time and skill. I'll give a few pointers below, but if what I can suggest here in print as opposed to being there and showing you works out, guess what? You got lucky! I once spent 3 hrs adjusting an eq for a lady who insisted that her speakers be no more than 1 ft away from the wall. There was no reason why they couldn't be 2ft away where they sounded almost perfect, but she wanted 1 ft. So, she got 1 foot with reduced bass and great sound. The customer was happy!
They key to getting the best possible sound from your speakers is to find the best place for them in whatever room you'll be listening to music in. Moving them closer to or further away from walls, moving them to different locations in the room, etc will effect how they sound.
What if you're limited in your choice of spots? Say you have floor speakers that sound great 3 feet from a wall and because of the arrangement of doors, windows and other factors, you can't keep your speakers 3 ft from the wall and moving them closer causes the bass to over power the rest of signal, the room and ultimately you! In such a case, the first course of action should be to turn down the bass control on your amp. However, this is a very broad control which will most likely turn down ALL of the bass. If only a particular portion of the bass is all that needs to be reduced, say the very deep bass, then you have one of the few situations where an equalizer is truly necessary. In this case once the speakers are placed as far from the wall as possible (1 - 2 feet), while listening to a recording with reasonably strong bass, you should start by turning the balance to the left channel only. Then starting with the lowest band, move it down to -3 db. If this is not enough, move it down to -6 db and the next band down to -3. Still not enough? Set the first band to -9, the next to -6 and the next to -3 and so forth. Basically, you'll want to keep a smooth transition between bands. You can also do 1 and 2 db steps if 3 db is too severe a drop. Then set the balance to the right channel and adjust it. Once this is done and the balance is back to center, it should sound good.
If your bass seems weak and moving the speakers closer to the wall doesn't correct it, instead of turning the bass up, the first course of action should be to add a subwoofer to the system. If this is not a viable option and Eq is the only way, the midrange and treble should be reduced rather than boosting the bass. If this doesn't work, you might have to see about making a sub work. It has been pointed out more than once in this forum, that using the eq to boost parts of the signal, especially the bass adds strain to your amp and may cause it to clip and distort. This will harm your amp and speakers.
Again the bottom line is avoid using an eq if at all possible. If you have no choice, reduction is the key.
You just described the exact challenge I was facing. I have Klipsch Reference RF-52 II fronts and an SW-310 sub. At the time I was using the sub to extend the bass from the fronts - cutoff at 40 Hz. The only place I have for the fronts right now are within about 12 inches from the wall behind them.
The bass was overwhelming in many locations. Klipsch reference floorstanders have rear ports. I suspected the rear ports were the source of my issue since the speakers I had before - which were front ported - didn't present this challenge (as far as I can remember).
Moving my speakers 3 to 4 feet away from the walls helped considerably. The bass response was still uneven throughout the listening area although the standing waves problem improved considerably for the few spots it becomes most drastic - I could almost live with that sound - but I cannot keep the speakers in that position. I'd have to move them out to listen and move them back when done. I tried that for a few months and grew really tired of moving them. It's also not very healthy for your speakers IMO to keep moving them daily like I was doing - the boxes get loose over time.
I tried using the EQ to solve the problem and I ended up with fronts that produced no bass at all - the sub handled all the bass. It was better than what I started with but still not acceptable to me. I had to subtract -12dB at 60 Hz to get the standing waves to go away. At that level the bass from the fronts were almost nil.
The solution I finally came up with was super hi-tech. In the spirit of GoldenEar speakers I call it the Spherical Intra-portal Acoustic Dampening Bio-fabric. I attached a picture of this super hi-tech solution since it is so immensely complex that it's best to just show you. With those in place in both speakers the bass response was weaker but much cleaner and even across the listening room. I raised the sub output and frequency to make up for the loss in bass. Now the sub is crossed at 100 Hz and is turned up a tiny bit. I like it. It sounds great to me - and I guess that's all that really matters in the end.
I just wanted to pass on this tip to anyone wrestling with an outrageous standing waves issue who cannot move the speakers away from the walls. IMO this is a much better solution than using an EQ to subtract bass - for this specific set of circumstances. I'm with you super - i'm trying to avoid using the EQ whenever I can - I keep that as a last resort. Here's one more tool to achieve that.
Rocker, you've likely created an "aperiodic" vented enslosure. Dynaco used this loading system in their A25 loudspeaker back in the '60's; http://home.indy.net/~gregdunn/dynaco/components/speakers/
Marantz supplied damping plugs with their top o' the line Imperial 9's back in the late '660's (without the plugs, the 9's were faily assessed as "boom" machines in most rooms) and then the idea disappeared for a few decades. B&W revived the idea (mostly) for HT use in the '90's as the result of most HT systems requiring more "discreet" speaker placement and most HT system's also including a subwoofer.
The idea is to present a certain amount of "mass" at the vent of the resonant enclosure. This mass loading affects the system's bass alignment which, in your case, raises the speaker's "system resonance", thereby altering the frequency or frequencies which are most strongly reinforced by the air mass resonating inside the box.
If your "bio-fabric" is dense enough - which rolled like it is, it probably is - you've changed the vented Klipsch design from a bass reflex system to an acoustic suspension system. If the driver selected by Klipsch falls into the range which is suited to either a vented or a sealed system, the system resonance would have been raised - where the bass cut off occurs will have been raised - and the bass roll out rate would have changed from a -24dB per octave rate to -12dB per octave. This would be fine if your low frequency driver(s) were suited to either system.
The system resonance would have been raised and your adjustment to your subwoofer would have been correct, the sub would need to operate up to a higher frequency to compensate for the higher cut off of your speakers.
Problems might occur which would be related to your blocking the port though. Nothing which would damage your speakers. Klipsch is unlikely to have used a driver not suited only to a vented enclosure. Changing the bass alignment by adding mass to the vent would create rather ragged bass response. It sounds though as if your room already has some peaks and nulls which would likely swamp this issue, making it just one more issue in a group of issues. More importantly, IMO, is the roll out of the bass response vs the filter action of your subwoofer.
There really is no middle ground between a vented system's roll out and a sealed system's roll out, the system is one or the other and nothing occurs in between those two rates. Your subwoofer, however, could have any filter rate between -6dB and -24dB. IMO the steeper the filter roll in/out of a subwoofer the more effectively it can affect how the sub mates with your main speakers.
Do you know the filter order or rate of your sub's crossover? Are you running your main speakers through your sub's crossover? Or, are you running your main speakers directly from your HT receiver's speaker outputs? Where do you have your receiver's LFE filter set? What frequency are you using for that setting?
Did your speaker's enclosures actually "get loose" by moving them?
Rocker, you've likely created an "aperiodic" vented enslosure. Dynaco used this loading system in their A25 loudspeaker back in the '60's; http://home.indy.net/~gregdunn/dynaco/components/speakers/
Marantz supplied damping plugs with their top o' the line Imperial 9's back in the late '660's (without the plugs, the 9's were faily assessed as "boom" machines in most rooms) and then the idea disappeared for a few decades. B&W revived the idea (mostly) for HT use in the '90's as the result of most HT systems requiring more "discreet" speaker placement and most HT system's also including a subwoofer.
The idea is to present a certain amount of "mass" at the vent of the resonant enclosure. This mass loading affects the system's bass alignment which, in your case, raises the speaker's "system resonance", thereby altering the frequency or frequencies which are most strongly reinforced by the air mass resonating inside the box.
If your "bio-fabric" is dense enough - which rolled like it is, it probably is - you've changed the vented Klipsch design from a bass reflex system to an acoustic suspension system. If the driver selected by Klipsch falls into the range which is suited to either a vented or a sealed system, the system resonance would have been raised - where the bass cut off occurs will have been raised - and the bass roll out rate would have changed from a -24dB per octave rate to -12dB per octave. This would be fine if your low frequency driver(s) were suited to either system.
The system resonance would have been raised and your adjustment to your subwoofer would have been correct, the sub would need to operate up to a higher frequency to compensate for the higher cut off of your speakers.
Problems might occur which would be related to your blocking the port though. Nothing which would damage your speakers. Klipsch is unlikely to have used a driver not suited only to a vented enclosure. Changing the bass alignment by adding mass to the vent would create rather ragged bass response. It sounds though as if your room already has some peaks and nulls which would likely swamp this issue, making it just one more issue in a group of issues. More importantly, IMO, is the roll out of the bass response vs the filter action of your subwoofer.
There really is no middle ground between a vented system's roll out and a sealed system's roll out, the system is one or the other and nothing occurs in between those two rates. Your subwoofer, however, could have any filter rate between -6dB and -24dB. IMO the steeper the filter roll in/out of a subwoofer the more effectively it can affect how the sub mates with your main speakers.
Do you know the filter order or rate of your sub's crossover? Are you running your main speakers through your sub's crossover? Or, are you running your main speakers directly from your HT receiver's speaker outputs? Where do you have your receiver's LFE filter set? What frequency are you using for that setting?
Did your speaker's enclosures actually "get loose" by moving them?
I started out with Klipsch RF-62 fronts - probably too much for someone living in a condo as do I. I've never owned rear ported speakers before - I had no idea they could send so much deep bass out of the rear ports (RF-62 have 2 ports tuned to the back of the woofers and it sounds like just as much bass come out the back as what gets pushed from the front). Anyway - I was getting the craziest uneven bass response i've ever heard. In fact - if I didn't hear it myself I would not have believed it. Pulling them out from the wall 3' to 4' helped a lot.
Yes - after 2 months or so the boxes actually started to loosten. So I knew I had to find a better solution. I replaced the RF-62 with RF-52 - not related to this issue - for other reasons - and the RF-52 have the same problem although not nearly as pronounced.
The socks is not something I want. It has a sort of a stupid redneck look to it. But it works really really well. Now - I have the most even bass response i've ever had. I get a little more bass near walls and in corners = that will always be true regardless of the speakers - that's how sound behaves - but all around my place the bass sounds exactly the same.
I thought about the sealed box concern when I came up with this. The sock is quite thin. It lets air in and out of the port. I mean it's not sealing it up tight. What I mean is I could cover my mouth with that sock the same way i'm doing those ports and I could easily breathe through it. So I was hoping the speaker could "breathe" through it too. But it does obviously make a huge difference in the sound - so it is blocking air in some way. If that alters the performance of the speaker its not something i've noticed. Not saying it isn't happening - just that I didn't notice it. I was hoping that since i'm playing these things at low volume that it wouldn't hurt them to do this. Glad to hear you don't feel i'm risking them with this.
I do not have an LFE channel. My receiver is an old Dolby Surround model. The sub is just an extension of the fronts. I have it cutoff for now at around 80 Hz judging by the markers on the dial on the back of it. I tuned that by ear. It blends with the fronts about as well as I could hope for with old equipment like this (as far as I know).
I tried using the EQ to solve this problem - trust me when I say the sock thing was my last resort - and I had to subtract like -12dB at 60 Hz (my bottom band on the 7-band EQ) to get the bass even close to normal while i'm sitting here on the couch - and that made the bass response everywhere else terribly flat. The EQ on this system applies to all channels - so the subwoofer gets the -12dB cut too and well - you can imagine how strange that gets. No, the EQ is just not a good solution with this old equipment for this problem.
If and when I finally do get a new AVR with bass management i'll try cutting the fronts off at say 80Hz or 90Hz and see how that works out. yes I would very much like to get the socks out of my speakers. I looked at the manual and specs for the Yamaha RX-A720 and it has a 12dB/octave hi-pass cutoff and a 24 dB/octave low-pass cutoff on the selected xover frequency. I'm hoping I can cut the fronts off at a frequency low enough to retain some decent bass from the fronts and still fix this issue (without socks). With the sub at 80Hz now it sounds fine - but there's no cutoff on the fronts though - well - that is unless you count the socks - hey - maybe I should put a dial on the socks - it's amazing what people fall for these days - we'll see.
I'll never buy another rear-ported speaker system ever again.
Dave, you have a relatively small room right? You're also using a subwoofer. Is using book shelf speakers out of the question? They could do you a world of good. Perhaps you could give them a try?
HSU subs...and others....come with multiple ports. My HSU also comes with a SINGLE port plug and a switch on the plate amp labeled 'Maximum Output' or 'Maximum Extension'. After test, I leave the plug OUT and set for max output, but still get musical bass. Some movie effects will vibrate the entire room.
