Sub Integration

Did you measure the response? This does sound like room modes. See the thread on room acoustics: https://forum.audiogon.com/discussions/room-acoustics-10
However, you may also have set the crossover frequency (much) too high. With my main speakers (Quad 2805) I have the crossover at 33 Hz and with my little Harbeth P3ESR mini monitors the optimum was 45 Hz.
Did you also try to omit your external crossover and just use the low pass on the subs (at a lower frequency?).
Maybe you need room equalization like the Antimode 8033. It worked a treat for me.

Are the Klipsch subs ported?  If they are ported then that is why they sound boomy! You are always better off with a sealed sub for a 2 channel music only system!

You kind of answer your own question. If money were no object, you need bass traps and an EQ. Make sure you are cutting off your main speakers above 80 Hz.

Good free software is Room EQ Wizard (Google it), but there is also Audio Tools for android + a $27 imm6 microphone from Dayton:

http://amzn.to/2yJi0VH

You'll probably also need mini to RCA cables for the test signal.

Best,

Erik

Set the subs to cross over around 55Hz and you should still have plenty of low end with less boom.


Matt M

Well, first it probably would be better to stuff the ports of your main speakers.  Go to a drug store or similar place and buy a pair of women's ankle-high nylon stockings.  Then go to Home Depot or similar and buy a small amount of rolled up fiberglass insulation (you can find small packages).  Cut a piece that is about as long as the port is in the short dimension, then roll it up until it seems a little bigger in diameter than the port.  Cut off the rolled-up piece and, keeping it rolled up, put it in the stocking.  Tie off the open end of the stocking.  Now repeat for the second speaker.  Then put your stuffers into the ports of your main speakers.

Now, find some music that has decent bass -- a jazz trio works well because you can hear the individual double bass being played and it will span the range of your main speakers and subs.  Set the subs' cross overs at the lowest frequency setting, and the levels at zero.  Now, start playing the music.  Gradually increase the first sub's level control until you are just aware of the sub as a separate sound source, then back off just a bit.  Do the same for the second sub.  Make a note of the level settings . . . you'll want them to be the same on both subs.  If one sub's level setting is higher than the other's, turn it down, but not all the way to the setting of the other sub.  Then turn the other sub's level control up, to the same setting as you established for the first sub.  Does the bass appear not to be coming from the sub, but somewhere between the main speakers?  If so, you've got it.  Now, listen to the quality of the bass being played.  As the player plays lower notes on the bass, does the loudness appear to be the same as the higher notes?  If the player is running up or down the scale, is there a note "in the middle" where the loudness seems to falter?  If so, raise the cross over setting just a little, and listen again.

This sounds tedious (and it is) but if you work at it, eventually you will get the seamless bass that you want.  In my long experience fooling around with subs, I have found it is hopeless to try and set up a sub based on the frequency response specs of the main speakers and whatever is indicated on the frequency control of the sub.  You will just never get there.  The problem is that the frequency control on the sub is likely inaccurate, the indicated response of the main speakers is also likely inaccurate, and every normal sized room (i.e. not an auditorium)  has a fundamental resonance somewhere between 40 and 50 Hz with a peak of up to 6 dB.  And, with a ported main speaker, there is a phase shift at the speaker's  system resonance point where the sound from the port predominates (below the system resonance point).  This sound is 180 degrees out of phase from the speaker's sound above the system resonance point, which comes from the driver.  As long as you're running the speaker alone, this shift doesn't matter.  But, when you bring a subwoofer into the picture, it does because this shift takes place right about where the subwoofer and the main speaker are working together.  That's why I suggest you stuff the ports of the main speakers, to reduce this output.  This reduces your main speakers' bass extension, but you don't care about that because you've got the subs!

Thanks Bruce,
You've offered some very good suggestions. A couple more questions that maybe you and others can weigh in on......
The PSB Imagine B speakers are rear ported and PSB suggests that the closer the speakers are placed against the rear wall the more enforcement there is in bass. Mine are placed about 3 feet away from the wall. PSB offers port plugs for some of their floor stander models but not for these. I have considered plugging the ports and port plugs are offered in a generic sense on the Internet but I wouldn't know which and what size to order. For an initial experiment on the results of plugging the ports with the design you suggest, I have an abundance of foam of different sizes, much like sealing up openings around a window air conditioner (soft foam). Compressed and sealing up the ports, would that suffice for an interim port plug?
The Outlaw ICBM that I use for bass management recommends to set the crossover frequency on the subs to their highest frequency and then let the ICBM determine what frequency the subs actually see. Does that make sense?
The NAD amp and the PSB speakers sound very good. I originally had the speakers connected to a very good HK receiver. The sound was horrible. Like many have said that there is some truth to NAD and PSB having some chemistry since they are, or were, sister companies.
So far I have received some great advice from you and others. Will continue to obtain sound that is as good as my system is capable of.
Thanks All

You should look into using the 1/3 rule especially if the speakers are rear ported. 1/3 rule is to move your speakers 1/3 of the room length from the front wall and move your listening chair 1/3 of the total room length from the behind the chair. This is a common practice as a starting place for the speakers. Also, don’t put the subs in the corners, never do this unless your designing for a home theater. Move the subs out into the room and you will get more even bass. Check out Jim Smith books/videos or the Cardas website for better clarification 

I’ve run a test CD to see where my main speakers "actually" roll off in the bass realm, as opposed to confusing "in room" compared to "anechoic" ratings, or actually misleading published specs. You can use a test tone to reveal room bass issues without the expense of some digital EQ gadget. Your ears might work! My main speakers (Silverline Preludes) are allegedly capable of 35 hz or something but really 50hz is where they drop off (you can hear there is a teeny bit of 35hz coming from these things if you put your ear an inch from a woofer, but hey…nonsense)…consequently I use 50hz as the starting point for woofer settings (2 REL subs) and that works swimmingly. Also, I recently committed audio heresy by getting a Schiit Loki 4 band EQ and I can now highly recommend these…an el-cheapo and utterly noiseless little gizmo that really does it’s thing. I only use it when I feel a source sounds weird or when I want low level sound tweaked…like a "loudness" control…the 8k higher level knob is a serious cymbal booster and the 20hz low knob will tame bass issues. I doubt many people can actually do the 1/3 rule thing as often they have to live in the place where the audio rig resides, but there clearly are other solutions.

The 1/3 rule suggested by rbstehno is appreciated but does not apply to my listening space. My room is 15' wide and 20' long. If I apply the 1/3 rule then my listening point would be only 8' away from the speakers and in the way of casual traffic in the room. Not practical for my space. I really appreciate all of the suggestions offered and will continue to experiment with all of them. Perhaps I have a very challenging task.
Thanks

I would crossover your sub naturally in the nighborhood of 50/60hz, where you hit the -6db point from your speakers.  This will take care of the boominess.  As for the volume level,  you can use white noise and music and do it by ear.
Most of the music is played at above 50hz, so there's no need for sub above that unless you like fat low bass.  To me, a sub is meant to be used for sub-bass (40hz and below).

Audiotools good
vandertones = free
need Analog spl Meyer radio shack

use Ray Brown Soular Energy as Bruce suggests to set bass output level

attenuate the port do not plug 

DEQX

yogiboy suggests that sealed and not ported subs are better for music and ported are better for for HT. My aim is for music. I have read opinions from others that this is true. Originally I had one sealed Klipsch sub. The second sub I added is also a 10" Klipsch sub but is front ported. If I plugged the port on the second sub would I have, in effect, two sealed subs? If so, what plugging material would I use? The front port is located in the front bottom and is a rectangular opening. The system is not played at extremely high volume.
Thanks for any suggestions.
 

@jrpnde .. like you, I have 2 ported subs in my 2-channel system and use an ICBM-1. The ICBM-1 is a great component and you should be able to tame the subs boominess with it. I agree with @chrisr and would start by setting your crossover to 60Hz and turn the "subwoofer level" all the way down. Play some music and adjust the level up by ear. Mine is always set between minimum and the center line. Try placing your subs next to your speakers as well. BTW do you utilize the ICBM-1 in stereo subs mode?

Thanks wtf,
My system isn't quite the same as yours. I have two 10" Klipsch subs but one is sealed and one is front ported. That's why I considered plugging the ported one to bring the two closer in performance. Yes, I am using the ICBM in stereo subs mode. ICBM manual suggests setting the crossover on the subs to their highest setting and then select the actual crossover point on the ICBM. I assume this is the correct way to incorporate the unit with the subs? Thanks again for your suggestions.

ICBM manual suggests setting the crossover on the subs to their highest setting and then select the actual crossover point on the ICBM. I assume this is the correct way to incorporate the unit with the subs?

Exactly. I also set the volume on the subs to the same level (half way on mine).  And if I wasn't clear, set your ICBM-1 crossover to 60Hz and use the the ICBM-1 "subwoofer level" to dial it in. As mentioned above, mine is always between minimum and the center line on the ICBM-1. You'll know quickly when it gets boomy. Best of luck.

Note that properly utilized subs add far more to your sound than simply bass tone, as the overall "feel" of a system can improve dramatically with the addition of what has been called "charging" of the room with a good sub or two. Everything sounds better as you’re getting the reality of musical low frequency that is part of life (how profound…I think I’m gonna weep), even if you're listening to only mandolins. Also, if you add the sub at the -6db point you’re going to have a gap in the output of the actual music…not recommended, as nobody should recommend anything other than messing around with placement and level until you’re happy as a clam in the sand. Proper sub level is absolutely relative to the main speakers it’s blending with, and the sound of what’s being played…sometimes requiring adjustment which I do by turning the subs up or down a little or using my previously mentioned Schiit Loki.