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Looking for the BASS

For some time I wanted to open a discussion about subwoofer set-up, where audiogon-ers can share their experiences and knowledge on the matter.

My story is about REL subwoofers (the only subwoofers with which I have experience). However, since the physics of low waves does not change when going from REL to VELODYNE to JL Audio, etc., this discussion should definitively NOT BE restricted only to REL subwoofers. Any tips and tricks that might help us improve our set-ups are very welcomed.

Here goes my story:

In august last year we have moved to a new home where I've got to have my own music/study room. The dimensions of the room are (L x W x H) 4.70 x 3.60 x 2.40 (i.e. 15.42 x 11.81 x 7.82). While it is not a very large room I find its dimension more than decent. My system consists of Accuphase electronics (E-550 class A integrated amp, DP-550 cd player and the DG-38 vicing equalizer) and a pair of Focal Micro Utopia Be speaker complemented with a REL Stentor 3 subwoofer. (For more detail see the page of my current system, i.e. Kosh Naranek.)

In the last 6 months I have been moving the system around the room, placing the speaker and woofer agains each of the four walls, then further optimizing the position of the subwoofer. While getting a good stereo image was never a problem, obtaining a smooth bass response was challenging. Depending on the wall against which the speakers were place I was getting either too much or too less bass.

Placing the speakers against the long walls yielded much better results then when placing then against the short ones. This is in agreement with my findings in my previous rooms, though this need not be always the case. As can be seen in the 3rd pic on my Kosh Naranek system, I ended up with the subwoofer between the speakers, about 30-40 cm behind de plane of the speakers and rather close to the left speaker (about 20-25 cm).

** SPEAKER PLACEMENT:

From experience I know that it is best to place my MicroBe about 2.0 - 2.30 meters apart and place the listen chair at approximatively the same distance form the speakers. Thus, given the dimensions of my room, the speakers were placed approximately 1.2-1.6 meters from the back wall and 0.75-1.5 meter form the lateral walls (different room layouts led to different values, of course).

** SUBWOOFER PLACEMENT:

* I start by following the REL procedure - as indicated in the REL manual. With the subwoofer in one of the corners behind the speakers and while playing a track with repetitive strong bass I do the following:

a) adjusts the phase of the subwoofer in order to get the loudest bass,
b) moves the subwoofer away from (or closer to) the corner, again looking for the position that gives the loudest bass
c) adjusting the crossover point and the volume of the subwoofer in order to obtain the smoothest response

While this method yields decent results, one can almost always improve the results obtain with it. This is how I accomplish this:

Using the settings for the crossover and volume determined using the REL procedure, I moved the subwoofer in my listening position. Then, I move around the room looking for the position that has the most even bass response. What I actually do here is: 1) Play an walking bass line, most often the first 3 seconds from track 3 on Norah Jones's "Come away with me" album, i.e. Cold cold heart. I make a loop with my CD player and play the first measure of this track continuously. 2) Walk around the room and look for the place where all notes of the double bass sound equally loud. Once I have found the right place I move the subwoofer there (keeping the sub orientated exactly as it was when placed in the listening position). Further fine tuning can still be done by moving the sub in very small steps of 5 cm or so. Slight movements of the listening chair closer or further from the plane of the speakers can result in additional small improvements. Finally, I should mention/stress that in my room I always had to change the phase setting of the REL (compared to the setting determined when using the REL procedure, even though the REL is still behind the speakers) in order to obtain the most even bass response.

Following this procedure I was able to obtain a very natural and full body bass in my room. At this point, I have run the room set-up procedure of the Accuphase DG-38 voicing equalize. This has improved things even further, much further actually, i.e. by clearing up all bass notes (by removing any bass bloat) and making them sound much faster.

The final result was definitively worth the effort, though moving my large drum kit around the room 5 times (and then setting it up) was a bitch. Moreover, my wife has now the greatest respect for my patience and determination. She knows me for 11 years and had no idea I have this in me ... though, like all women, she wishes I would put this kind of effort into something more useful ... :)

Take home messages:

1) BE PATIENT AND DO NOT GIVE UP EASILY!
2) Subwoofer placement is crucial
3) Electronic correction can make a huge difference BUT apply it only in the last stage and as little as possible

As mentioned in the beginning of this post I look forward to hear your thoughts/experiences on subwoofer set-up procedures.

Best wishes,
Paul
nvp
don_c55
1,025 posts
 
Just give up on LOW BASS below 30Hz!

Standing waves, peaks and valleys in different spots, impossible equalization, ugly room treatments, lack of musical information! DO NOT BOTHER!

THe lowest note on a Fender bass is 42Hz!

Who are you trying to impress???
nvp OP
317 posts
 
Bondmanp, REL recomands that REL subwoofer to be placed in the corner, most likely there are also other manufactures that recommend this and/or design their woofers with this in mind. Some see this as a weakness or a sign of poor design, viz. the sub requires reinforcement from walls as by itself is not powerful enough and/or can't go low enough. To some extent they have a point. Personally, I do not care - I love my REL very much.

Don_C55, ignorance is bliss!

Firstly, standing waves and constructive and destructive interference happens also above 30 Hz. Secondly, there are quite a few instruments that go lower than a bass guitar, e.g. Pipe Organ (20 Hz), Piano (27.5 Hz), Doublebass, Tuba, Harp, etc.

No body is trying to impress anybody. I started this thread and described in details what I have done because there are very many people asking questions about subwoofer set up procedures and/or how to deal with bass problems. (I have found three new threads on this topic since my last post here, i.e. a month ago).

Best regards,
Paul
vicdamone
850 posts
 
The physics may be similar but the designs and electronics are like comparing apples to oranges.

I've owned a number of subs from pro audio sound reinforcement, Electric Bass stage units, and subs for home use. In most all cases they have taken a line level input into their amplifier.

Powered home subs offer the ability to use the high level output of a systems receiver with limited line level outputs as a necessity and/or a convenience option. You will almost never find this option in pro audio.

It's my experience that using the high level connections on the subs I auditioned all had differing affects on the main speaker performance varying from slowing transients or pace, reducing output, to outright degeneration of the signal to the main speaker. Keep in mind with a high level connection the addition of added circuitry, its design and quality, all contribute to the output.

I found the one manufacturer who's design is optimized for using the high level connection method had a lesser amount of the issues as with the other subs but by direct comparison with similar subs using line level connection their products output was simply unacceptable to me. Still, many find their products to be wonderfully musical, so it really is a matter of taste.

I don't understand why one would limit the extra low output of a capable, properly calibrated subwoofer other than personal taste. In live music and a great deal of recorded music instruments such as Basses and Drums can produce overtones below their fundamental of the string or head tension.

Controlling the output of a subwoofer system is key to system and room integration which, in my experience, results in the overall musicality a subwoofer/s can provide. In my experience it's very difficult if not impossible to attain the room integration with a sub that simply provides crossover, volume, phase, and the physical positioning as the method of control. Modern powered subwoofers using internal or external, analog or digital, detailed equalization, provides a much more seamless integration and subsequent musicality to a room and can still allow a large degree of the subs volume attenuation while maintaining room integrity.

Being able to remotely attenuate the subs output is one of the most fun aspects of getting good room response. Pace, prat, Schiit just put on Prince.
nvp OP
317 posts
 

Vicdamone, thanks for the contribution. Writing a good long post takes time and often is not appreciated.

Of course, choosing the right type of connection is essential for achieving a seamingless integration between subwoofer and the main speakers. (My sub has both types of connections, i.e. high level and low level. I use the high level one because this is what the manual recommends.) However, while essential, choosing the right type of connection does not guaranty a successful integration.

The main point I am/was making in this thread is that the position of the subwoofer in the room is really essential, viz. interference patterns depends very sensitively on the relative position of the sound sources, i.e. sub and reflecting walls (which need not necessarily be the walls of the room where the sub is). Interference really has nothing to do with the type of correction one uses (low or high level inputs). Also, while not a bad argument, the fact that pro subs most often do not have a high level input is not that relevant (IMO). This can be pure commodity :).

The second point I made in this thread is that electronic equalization is important. Here we fully agree. Most often, even after carefully optimizing the position of the speakers and subwoofer, one still has a few frequencies that are excited (or partially canceled) by the room. Having the ability to tame down or pump up a little very specific modes can make all the difference in the world. (In this regard REL is definitively lacking a very important and essential feature. I believe you were referring to REL in your post, right? Fortunately, I can use my Accuphase DG-38 voicing equalizer to address this issue.) However, I firmly believe that electronic equalization should be done only after optimizing everything else - trying to even out peaks and valleys of 10 dB or more without adjusting the crossover, volume and position of the sub in the room is wrong.

Best wishes,
Paul
vicdamone
850 posts
 
Ahh, the easy way...

["REL Studio III subwoofer
By Larry Greenhill • Posted: Oct 26, 2004 • Published: Oct 1, 2004
Setup
Two Sumiko installers, Patrick Butler and Allan Hager, traveled to my listening room to install the big REL. They had all the desired criteria: youth, intelligence, physical strength, and lengthy experience with and respect for REL subwoofers. Together, they lifted the Studio III off my garage floor, carried it carefully into my house, up the stairs, and into my listening room. Patrick—taller, more fastidiously dressed, more precise in diction—orchestrated the physical installation. Allan—more casually dressed, more poetic—provided a lengthy description of how to accomplish the subwoofer's fine-tuning and room-matching.

The second reason that installing a REL Studio III is no solo task is the degree to which the sub must be tuned to one's listening room. A minimum of two people are needed: one to listen, the other to set the controls on the Studio III's service panel. This Patrick and Allan did. In fact, Sumiko trains dealers across the US to install and tune REL subwoofers; any buyer of a new Studio III would get the same assistance in delivery and setup that I did."]

[{"Finally, I should mention/stress that in my room I always had to change the phase setting of the REL (compared to the setting determined when using the REL procedure, even though the REL is still behind the speakers) in order to obtain the most even bass response.'}]

Just an FYI for everyone using a sub. The phase of recorded material, regardless of the type of media, can change from track to track on the same album. It's most noticeable in popular music were the, "Kick," or Bass Drum has a dominate voice.

If your subwoofer has remote control with a phase button, from your listening position try switching the phase. It's not always noticeable but if that track is out of phase you'll notice the Bass Drum tighten up with the rest of the music. A pain in the butt to be sure but if you're doing some serious listening its worth checking.
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