Sub Integration


Here's my system...
NAD C375BEE integrated amp
PSB Imagine B speakers
2 Klipsch 10" powered subs
Outlaw ICBM Bass Management
For 2 channel music only (not HT)
My listening room is 15' X 20' with plaster walls and carpeting. I have experimented with moving the subs at different locations and sub output volume .The Outlaw crossover is set at 80 Hz to handle lows below the PSB capability (52 Hz). While the mains still sound good the bass from the subs still sounds what many would say is "boomy". I do not have an SPL or any room correction equipment.
Any suggestions as to what I may try next?

jrpnde
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