Subwoofer Crossover Setting/Directional Bass Freq.

My speakers are rated down to 28 Hz. I decided to experiment and hook up my sub woofer that I had in my home theater system to my music only system. The sub woofer (HSU VTF3 MK2) has a built in amp. I must be getting old because lugging a 70 pound box up the stairs took some concentration. At any rate the sub woofer has a crossover control. Should I set it to take over where the speakers drop off (28 Hz.)or should I set it to overlap the speakers say at 60 or so Hz.?

I have heard that at some point, bass frequencies become non directional. This might also come into play on which crossover frequency I use. At this point I may have to power the sub from another outlet/circuit and placement might have to be away from the main speakers. Does anyone know at what point/frequency bass becomes non-directional?

Lastly, I'm wondering if I really need a sub with my speakers that go down to 28 Hz. Initially after hooking the sub up to my music system, I'm not totally crazy about it. I may have to play with the settings a bit. It seems that the best setting is one that makes the bass very, very subtle. If the sub woofer bass is not set proportionately, it almost seems overpowering and takes away from the music. Maybe I would be better off without it.

I am new at all of this so if anyone has any suggestions or opinions on the matter, please free to pass them my way. Thanks in advance.
I'm not sure that is the right sub for your application HT subs don't mate well with two channel only systems
Its more challenging to incorporate a single sub into a two channel system
Low bass under 80hz will be non directional as you stated
You will need to tweek with placement and crossover settings
You don't want the sub firing back at your main speakers from across the room. This will actually cancel out bass frequencies from the sub and speakers you end up with odd bass anomalies similar to the issue you are experiencing
The best place to start is to position the sub with your main speakers firing in the same direction.
My Veledyne DD-15 makes it very easy to equalize for the room and for a smooth integrated frequency curve with its software that you can see on the TV and then adjust.

I mainly listen to 2 channel but also some HT and my processor has both music and movie modes and the DD-15 is set-up differently for each mode.

My speaker's do down to 30-35hz with no problem but you do have to play with phase and polarity and crossover to get a seemless integration. One of the more common errors is setting the volume on the sub too high and 'hearing' the sub as a separate speaker. It should blend seemlessly into the music or movie sound without drawing attention to itself.

Quite honestly, I don't know how I would have been able to do all this without the Velodyne's room eq software and on-screen frequency graph that instantly depicts andy changes made to crossover, phase, polarity, placement, etc.

Without it as the previous poster said, I'd start maybe 5-10 hz above your speakers' low end range and go from there.

Be prepared to spend some time but once dialed in, it will sound very good even with stereo music.
First, there's no basis at all to the statement regarding HT subwoofers (what is an HT subwoofer?) and music systems. A well designed and implemented sub will work equally well in both and Hsu makes good subs. It can be argued that a sealed versus ported cabinet has better application in one or the other.

You can not go by what the manufacturer states is the bass response of your speaker. You need to actually measure your speaker's bass response in your room.

There are two basic approaches to integrating a sub: 1) bass augumentation and 2) bass replacement. In bass augumentation you attempt to augument the bass response of the main speakers. Obviously, this works better with full range speakers that are capable of producing clean bass. In bass replacement you use a crossover to high pass the main speakers and low pass the sub thereby moving the bass chores from the main speakers to the sub.

Either approach can work. I'm a fan of bass replacement because the majority of speakers are not capable of producing clean bass and perform better when they don't have to handle bass.

The THX crossover point for subs is 80Hz. As the crossover point is raised above this, the sound becomes more and more easily to localize. A sub can be localized, regardless of the crossover point, if it causes nearby objects in the room to resonate or if the volume is not matched to that of the main speakers. The key to integration is setting phase and matching volume.

Almost every system can make good use of a sub. There are very few speakers on the market today that have bass drivers large enough to produce clean bass. Also, being able to place a subwoofer independently of the main speakers gives it a huge advantage in obtaining smooth in room bass response.

Optimally, you should not know a sub is in the system until you turn it off and realize what's missing. If you know the sub is there, then the setup still needs work. It's doubtful that you can setup a sub properly without an SPL meter and test tones.

You might want to look at the Harman papers: Click on White Papers and then these two papers: "Subwoofers: Optimum Number and Locations" and "Part Three: Getting the Bass Right".

As pointed out by Nick778, the Velodyne software is very useful. You might consider their SMS-1.

Best of luck.
I agree completely with Mr. Reynolds. I use a Velodyne HGS-15 with SMS-1 to supplement my KEF 104.2 mains. I find that the KEFs sound fine by themselves, but when used with the sub, they sound a bit more transparent if high-passed at 80 Hz. Maybe something about double coverage of the mid low range. Even careful listening cannot identify the sub as a separate source, except you realize the KEFs could not produce certain sounds, especially that felt more than heard vibration when a large pipe is invoked, the feeling you get at a live organ recital.

I agree with all that Bob has posted here, but I'd add that the single biggest
issue I have with augmentation is the difficulty in achieving smooth
integration. When "augmenting", you have a narrow range of
potential x-over frequencies that you're filling in "under". In this
case, let's say that means 30hz-40hz with your speakers in your room. If
there's lumpiness around or above those frequencies, I doubt that you'll ever
get good integration. My experience has been that the key to smooth
integration of subs is flat on-axis frequency response through the x-over

That's why I tend to agree with Bob's comments about HT vs Music subs. A
really good sub designed primarily for HT will probably sound great if you
can get flat response through the x-over point, and even a so-so sub will
sound more than decent. I use decidedly so-so subs -by today's standards -
and, to my ear, they sound great because I've gotten them to integrate very
smoothly. OTOH, before I got them dialed in, they were a problem. My
system might sound even better if I used true high performance subs, but it
sounds awfully good right now.

Similarly, I suspect that even a great sub which is poorly integrated will drive
you nuts. IME, many rooms will cause too many peaks and nulls in full range
speakers to achieve flat enough response to avoid this problem. However,
even if you're fortunate enough to get the type of smooth bass response
from your main speakers that allow you to augment for flat response, there's
another issue.

Even in the absence of "lumpiness", there's the issue of level.
That is, even if your current speaker happens to be perfectly flat for 2 full
octaves above your chosen x-over point of, say, 35hz (possible, but highly
unlikely) how does that level compare with the rest of the frequency range
above? If the band from 35hz through 140hz (in this example) is perfectly
flat but elevated by 5db or 7db relative to the mids/highs (actually pretty
good results relative to many rooms I've had), you'll get good integration, but
probably too much bass overall.

If you can augment successfully, it may be a better choice, because you can
get the active x-over out of the chain. However, IMHO, replacement will
usually be a better choice because it gives you broader freedom to choose a
x-over point that is both smooth and appropriate in level. IME, though, it's
hard enough to get it right even WITH the flexibility offered by an active x-
over. ( That's why I also use EQ in the bass. )

Good Luck


My point was not to pick on HT subs but to say that a single HT sub integrated into a two channel system can impose additional problems if placement is less than ideal.
When using two subs in stereo there is more flexibility for tweaking each sub for its placement crossover and slope without allot of additional EQ. But then again the room size will need to be considered for the particular subs.
I've heard quite a few different HT subs in a two channel set up and they tend to be over equalized for two channel but do a great job in HT.
I just have not heard a HT sub go from HT to two channel seamlessly. Two channel bass is more challenging to harness than HT.
I also agree entirely with Bob Reynolds.
The only thing I would add is that in the 2)Bass Replacement option, not only will your existing speakers sound better because the woofers are not being asked to do what they can't, but your existing amplifiers will suddenly develop far more 'headroom' as they are relieved of the power-sapping chore of supplying frequencies below 80Hz?
Nice post Bob! I agree completely.