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Searching for matching(?) Subwoofer solution

Hi folks,

I have a relatively new setup in my home office (12' x 14' with hardwood floor) and am seeking recommendations for a subwoofer solution.

Speakers: Ologe 5
Preamp:    Bryston P26 
Amp:         Forte 1A
Budget:     Flexible but just want something to provide a good match for the above components.
Music:       Mostly Classical and Jazz.  Some rock, some fusion.
Source:     Well, that's something else I am seeking advice on too and will post under the appropriate discussion topic

Problem is none of the local Hi Fi shops here in the Boston area have any experience with, let alone heard of Ologe speakers.  Couldn't get any recommendations there.

Has anyone owned or at least listened to these speakers? Or any of the other Ologe speakers?
The Ologe site (http://www.ologe-acoustic.com/) features a subwoofer called Ologe 20 at USD $8550.  
Just wanted to look into alternatives before dropping over 8 grand on the Ologe 20.
 I am open to but don't know much about subwoofer swarms.

I am not looking for anything overkill.  Just a subwoofer solution to nicely complement my somewhat modest home office system.

Thanks,
H
hleeid
mijostyn's avatar
mijostyn
8,570 posts
 
Wow this topic has legs. I like to simplify things. First of all it is not a sweet spot. It is a sweet line 90 degrees from the center of the speaker axis.
On this line the speakers are in perfect phase with each other and will cast an image of the recording to the degree that the system is capable. 
Now because of standing waves and interference patterns the frequency response below about 100 Hz on this line can vary up to 10 db. It depends on room dimensions and the way the subwoofers are used. 
You can hear this easily in your system. Just play a test tone at say 60 Hz and walk back and forth across the room and you will be flabbergasted at how the volume changes within just a few feet. When I was using two woofers I dealt with this by moving my listening position along the "sweet line" until I felt the bass sounded right. Doing this even with room control is a benefit because it will cost you much less amplifier power to correct the response at your listening position. With a point source system and one favored listening position 2 subs can do the job fine and as Raul suggests I think two good woofers is better than 4 bad ones. 
But, when it comes to other situations like having multiple listening positions along that line or having line source or linear array speakers you run into trouble. It is difficult to compensate for two positions and two point source subs will not project as well as line array speakers so the sound gets thinner as you move away from the system. This is where multiple subwoofers come into play. It seems that the SWARM group wants to place their subs anywhere in the room. This will smooth out the frequency response throughout the room but depending on the distance between to subs may cause phase issues. Here is a rule of thumb. For the drivers to act as one they can be no farther apart than 1/2 the wavelength of the crossover point. So say you are crossing over at 100 Hz. That is about 10 feet at sea level. If your subs are less than 5 feet apart they are acting as one and no matter where you are in the room they will always be in phase and as long as additional subs are closer than 5 feet to the last one in line they will always be in phase no matter where you are in the room. If you make the array longer than the lowest frequency you want to reproduce you have created a line source subwoofer. At lower cross over frequencies say 80 Hz the distance would increase to 7 feet between subs. 
Now in my case I need a subwoofer linear array to match the output of my ESL linear arrays and the woofers are arranged across the front wall with the outside subs in the corners. I am doing this to make the array function to below 20 Hz but a point source system does not have to worry about this. So, what I am suggesting to the SWARM people is to place their woofers in configurations so that one is no farther than 7 feet from the next assuming you cross at 80 Hz, 5 feet if you cross at 100 Hz. This will make all of them in phase no matter where you are in the room and should increase the dynamic response of the bass. Try it and let us know what happens. This rule is used by designers that use multi driver arrays. If you study various designs you will always notice that tweeters are always closer together than midranges which are always closer together than woofers. We are just extending the same principle to subwoofers and the much longer wavelengths involve. Pheyew that was tiring.

Mike
audiokinesis
2,737 posts
 

Mijostyn wrote:

"For the drivers to act as one they can be no farther apart than 1/2 the wavelength of the crossover point."

You do an excellent job of explaining your suggestion, but imo the issue it addresses is not one that a distributed multisub system is concerned with.

With a distributed multisub system, "the drivers acting as one" is definitely NOT the goal. We want each sub to interact with the room very differently from the others, and that is accomplished by spreading them far apart. So not only are there subs more than a half wavelength apart, they will also (almost always) have different path lengths to the listener(s).

Because the ear has very poor time domain response, such that it cannot even detect the presence of bass energy from less than one wavelength, a bit of smearing in the initial arrival times of the different subs is inconsequential. What DOES matter a great deal from a perceptual standpoint is how the notes decay. Since speakers + room = a minimum-phase system at low frequencies, when we have fixed the frequency response we have simultaneously fixed the time-domain response. Imo this is something that a good distributed multisub system does well.

(The ear hears low-frequency ringing quite well, but such ringing is always accompanied by a frequency response peak, and vice-versa. Anywhere in the bass region where there is a peak, whether it originates from a speaker anomaly or a room anomaly, the energy in that region takes longer to decay. It is actually the frequency response peak that we hear, not the ringing - the slow decay - itself. But when we have fixed the one, we have simultaneously fixed the other.)

Duke

mijostyn's avatar
mijostyn
8,570 posts
 
Hi Duke,
You will have to give me some time to think about it. Humans are extremely sensitive to phase. It is why we have two ears 8 inches apart. In nature it is how we locate danger and why a listener can put himself perfectly in phase with two speakers just by moving his head side to side a little. So the statement that the ear (which should be ears) have very poor time domain response is 180 degrees wrong. Now most of us can accurately locate a test tone at 60 Hz. Anyone can prove this to themselves by unplugging all the subs but one.
Blindfold the listener and in the middle of the room spin them around a few times, play the tone and ask them to point to it. Below 60 Hz and it gets progressively more difficult. Now this is a test tone, not music which is more complicated. If you put two subs in front of you and reverse the wires on one putting it 180 degrees out of phase the bass output decreases dramatically everywhere in the room. With more subs out of phase at various angles things get more complicated. Next in regards to very low bass, sensory input is not just coming from your ears it is also coming from visceral sensation. If I set off an M80 50 yards away from you you will hear it and feel it at the same time. All frequencies travel at the same speed. Regardless of what your ears are hearing if your woofers are out of phase with each other you may hear bass but you will not feel it. Speakers + Room do not equal a minimum phase system. They equal a confused phase system as you have the primary signal from all the drivers and their reflections bouncing all over the place. With the drivers acting as one the bass drum impact will strike the listener in phase with the greatest force resulting in the largest smile. The decay afterwards is of no great significance. 
So I suggest to those interested in this thread who have SWARM systems to play around with positioning and see what happens. This is a group experiment. I only know what happens in my room with my system which is different acoustically than most of yours. I know of one person who set up his four subs as I suggested and he thought it made an improvement. But, others indifferent situations may not feel this way. Or maybe not:)

Mike
audiokinesis
2,737 posts
 

Mijostyn wrote: "The statement that the ear (which should be ears) have very poor time domain response is 180 degrees wrong."

You are correct! I did not proofread carefully. Here is what I should have said:

"Because the ear has very poor time domain response AT LOW FREQUNCIES..."

The ear is indeed quite sensitive in the time domain at higher frequencies.

Mijostyn again: "Speakers + Room do not equal a minimum phase system."

Yes they do at low frequencies, which is what I said. This according to Floyd Toole and Earl Geddes. The in-room frequency response tracks the time domain response. The phase behaviors of individual reflections don’t matter when viewed in isolation, but their sum is relevant as it shows up simultaneously in both the in-room frequency response and in-room time domain response. It is the sum that we hear.

Mijostyn: "With the drivers acting as one the bass drum impact will strike the listener in phase with the greatest force resulting in the largest smile. The decay afterwards is of no great significance."

This is what our intuition tells us, and our intuition is wrong.

We literally cannot detect the presence of bass energy from less than one wavelength, which is 22.5 feet at 50 Hz (ballpark resonant frequency of a bass drum). A study was done in which less than one full wavelength of low frequency energy was played over headphones, so there were no room reflections, and it was UNDETECTABLE. And it took MANY cycles before the ear began to register the pitch. By the time your ears BEGINS to hear the impact of that bass drum played over your system, so much time has passed that any minor arrival time differences are inconsequential.

The decay is of enormous consequence because it shows up as a frequency response peak. And this is because speakers + room = a minimum-phase system at low frequencies. If the decay is slow at some frequency then the bass sounds fat because there is a response peak at that frequency.

Mijostyn:  "I know of one person who set up his four subs as I suggested and he thought it made an improvement."

The improvement may not have been for the reasons you suggest.   I strongly suspect that what happened is, the frequency response improved.  The in-room frequency response is what dominates our perception at low frequencies (though the in-room frequency response is merely a manifestation of the in-room time domain response, and vice versa).

Duke



noble100's avatar
noble100
2,419 posts
 
Hello Mike,

     I usually crossover my four Swarm subs at 40 Hz for music and HT but sometimes as high as 50 Hz.  According to your method of 1/2 the length of the crossover frequency, this would mean my subs should be no more than 14 feet apart at 40 Hz and no more than 11 feet at 50 Hz.
    My room is 23'x16'x8' with my main speakers (with bass extension rated at 35 Hz +/- 3db) along the 16' wall and run full-range. Two of my subs are along this 16' front wall with each about 2' away from the nearest corner and about 6' apart from each other.  The other two subs are located, one each, along the left and right 23' walls and each about 3' away from the corners along the rear 16' wall.  This results in my rear subs being about 16'apart from each other and about 20' apart from the nearest sub along the front 16' wall.  So, since some of my subs are more than 14' apart and exceed your rule of thumb, you're suggesting I should have bass phase issues in my room.
     The Swarm amp/control unit does have a continuous phase control adjustment.  I set this by inverting the phase on both of my main speakers and setting the phase control to the position at which the bass sounded the weakest at my listening seat.  I then reattached the speaker wires to in-phase and the bass sounded equally very good throughout my entire room and at the 6 seating positions in my room.  Do you think this is why I don't detect any obvious bass phase sound quality issues in my room?
    Although I've never heard one, I do understand from what I've read and from your comments that subs configured in a line array are capable of even better bass performance than subs configured in a distributed bass array.  However,  my music listening and HT room also doubles as my living room and devoting the entire 16' wall of my living room to a line of subs is not practical. I'm not stating I disagree with the high quality bass capability of a line array bass system.  I'm just stating that I'm willing to sacrifice optimum bass response performance in my room for the extremely good bass response performance of a distributed bass array that blends much more inconspicuously in my living room.  

Tim
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