My experience is different but I think I might go about it differently
than most. Up at the crossover point I am just listening and I do not
want to hear it. The subwoofers should just disappear(remember I use a
crossover point of 125 Hz). It has to sound like I am listening to one
speaker. As I evaluate lower down I go from listening to feeling. Do I
feel that kick drum the way I do at the club. Are those low synthesizer
notes shaking me the way they should. Does the room move under low organ
pedal. Hearing is one thing feeling is another. Part of the thrill of
live music are the visceral sensations you get.
These sensations are missing or greatly attenuated in most home systems. @mijostyn You mentioned that your room has not standing waves which is a bit of an achievement so naturally you would not set up your system the same way. Crossing over the woofers at 125Hz requires that you do what you are doing. Try crossing over so that there's no output at 80Hz and see how much correction you need. I get similar impact on my speakers at home, which are flat to 20Hz. The problem I run into is a standing wave that causes a loss of bass on certain notes at the listening chair- they are certainly there in other places in the room! That's why I got a pair of the Swarm subs, just to break up the standing waves. The speakers can shake the organs in your chest and the cuffs of your pants and they don't sound boomy. |
I find it rather comical that people can say phase is not an issue. Wire
one of your speakers 180 degrees out of phase and what happens to the
bass. @mijostyn Generally speaking, if you have a DBA setup, two of the subs will be in front and in phase with each other and the mains. But the other two may not- take a look at Duke's instructions above. Below 80Hz time alignment simply isn't an issue. Its great that you were able to build your room to prevent standing waves (which is hard for me to understand how that is possible). In such a situation a DBA does not make much sense. Most people do not have that luxury!! But that is such an exception to the norm that in a nutshell, your situation does not exist for most people. But having such a room, you must be aware that your comments, while correct for you, really won't apply to anyone else. |
it is not fine to run satellites full range while adding subs for three
reasons. First is you miss the opportunity to lower distortion and
increase head room significantly in the satellites. Second is you make
integration much more difficult. You are down where the wavelengths are
over 10 feet up to 30 feet. Unless you are using digital bass management
matching phase and time are difficult, usually by trial and error
moving the speakers and perhaps by using a phase control on the sub.
Without a two way crossover there will be more overlap making the
problem worse. I get the part about distortion and headroom in the mains (which you are calling 'satellites'). Its an issue that has concerned me. But as far as getting matching time and phase, below 80Hz its simply not a thing. The reason why has been explained here several times so I'm not going to repeat it. I ordered a pair of the Swarm subs to supplement my Classic Audio Loudspeakers which are flat to 20 Hz. The problem is I have a standing wave at the listening chair and too much bass elsewhere. So I only need two subs and I got Swarms since they are designed to operate inside the room boundary effect. I need them to be against the walls out of the way. Here are the instructions Duke sent along. When you look at his comments, its obvious that all the things that you are commenting about are on his mind as well, but are easily solved without resorting to DSP: You MIGHT try this: Start the subwoofer amp's phase control at 90 degrees (that may change later in the process), and wire the two subs
in opposite polarity from one another. This will tend to prevent them from making the low bass region too loud, while they are improving
the in-room bass smoothness. If the two Swarm subs are to the left and right of the listening area, this may also increase the sense of
immersion in a large acoustic space.
I normally leave the 18 Hz protective highpass filter ON, but that's up to you. Also, have the "Bass Boost" off. These controls are
on the back of the amp.
As a suggested starting point, going from left to right across the front of the subwoofer amp,
first the EQ: Frequency 18; Bandwidth .1; Level "0". This effectively turns the EQ "off", so it's in reserve in case we need it.
Next the other controls: Phase 90 degrees; Frequency 10:00 (about 75 Hz); and Gain at 11:00.
If you are going to be "dialing in" the subs by ear, here is the sequence of events that I suggest (you can also use this sequence
if you're using measurements):
1. First, adjust the Gain for best sound. This is the control which will make the most difference.
2. Next, adjust the Frequency. This will make the next most difference.
3. Cycle back through Gain and Frequency at least once.
4. Adjust the Phase. This will make the least amount of difference.
5. If there is too much bottom end, try plugging one port, and then unplug that one and try plugging the other.
If it's still too much, plug 'em both.
6. If there is not enough at the bottom end, try putting both subs back in "normal" polarity. If you lose smoothness from doing
this, go back to having one in reversed polarity and plan on using the single band of parametric EQ.
7. If there is still a problem area, OR if you need to boost the very bottom end, use the parametric EQ. Unless you have
measurements, expect some trial-and-error.
8. Cycle back through Gain - Frequency - Phase one last time.
It may still take several days before the Gain is dialed in exactly right. There are two reasons for this. First, the ear is
especially sensitive to changes in SPL in the bass region, so a small change makes a larger perceptual difference than you would
have expected. Second, the little knobs on that Dayton Audio amplifier are maddeningly small, so it's real easy to move the knob
more than you intended. |
The problem is that the room has a dimension and bass waves will
reinforce at certain frequencies and cancel in others. So unless your
bass traps are actively able to move about the room as the bass notes
change they will have little effect. DSP doesn’t work because it tries
to make your amplifier put out more power at one frequency and less at
another. But when you are dealing with a standing wave you might be able
to kill a bit of bass bloat at one frequency but you can put as much
power as you want into the bass nulls and the waveforms will still
cancel. So its only slightly more effect than bass traps. If
you really want to deal with this problem, the elegant way to do it is
to use a distributed bass array which can break up standing waves,
resulting in evenly distributed bass throughout the room. Do do this,
you take advantage of the simple fact that below about 80Hz in all but
the largest rooms, the ear cannot detect where the bass is coming from
so you can run the bass in mono. But it is important that the subs do
not reproduce anything above 80Hz; in this way they will not attract
attention to themselves. You’ll need at least four subs to do this
right. They need to be asymmetrically placed in the room and therefore
do not have to be aligned with your Harbeths. One sub system called the
Swarm ( www.audiokinesis.com)
is also the most well-known sub designed for this purpose. To minimize
their size they are designed go directly against the wall and take
advantage of the room boundary effect, to go flat to 20Hz. This is basic physics- in almost any room there will be standing waves. I've seen audiophiles fight them for decades- only to find out that by using a DBA that suddenly all is well. If you want an elegant and effective way to solve this issue, this is how its done. |
