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Setting up speakers

I have a simple, if somewhat tedious method for setting up loudspeakers in a room. It starts with the premise that rooms are imperfect acoustically, and will suffer the effects of reflection. There are two steps to my method:

1. Optimising LF evenness

A loudspeaker's bass response depends on proximity to walls, floor and ceiling. If some of the distances are coincident, then there is a multiplier effect on reflections resulting in nodes and modes. The objective is to spread these out as much as possible so that the room response gets closer to linearity. Working with odd-fractions is a good start. For example, placing each loudspeaker (of a pair) to be equidistance from each other as they are to their respective side walls (1:1:1). Same deal with distance between listening position and backing wall, e.g. 1:3:1 or 2:3:2 or 1:5:1 etc. Point the loudspeakers square towards the opposing wall. Toe will not matter just now.

The most optimal combo is the one that pressurises the room most evenly. By this, I mean you can walk around the room to a range of bass notes and they sound more or less equally loud irrespective of whether you are in the middle or corners of the room.

Another way of achieving the same result is to use an SPL meter with 1/3rd octave test tones. Position the meter/mic at the preferred listening position and take a set of readings for each of those loudspeaker spots. If your room is perfectly symmetrical, you could do that in mirrored pairs. Otherwise, you could measure each loudspeaker singly in turn. Moving them in various directions will change the LF response. Graphing the results will show the dramatic effects visually. I spent a bit of time on my knees when I last did this. It is tedious, but rewarding.

2. Optimising spatiality

Once you have chosen the optimal spots for best LF, you can adjust toe and possibly tilt. This needs to be done by ear. Grab some close-miked recordings of vocal music. The size and perspective of the singer's mouth should be proportionate and well defined. Adjust toe-in until the balance between an ambiguous wall of sound and a squashed sonic image emerges to your satisfaction. Generally, loudspeakers sound best when they are toed to cross listening axis at or behind the listening plane. As usual, there are exceptions and YMMV.

I hope that helps.
 
Thanks James for a concise explanation. Any thoughts on firing diagonally across a square room? The reason I did this was to try and avoid first reflections from side-walls as the room is dedicated but small at 3.6m (12') square by 2.1m (7'-6") high. Speakers are currently just over 6' apart and baffles are about 600mm (2') from back-walls on centreline, with a listening distance of just over 7' toed to cross just in front of the listening position (found this was best balance for forwardness) and I have plenty of "stuff" on the rear pair of walls for dead-end (much to the wife's dismay!) Very small adjustments of distance from back-walls and toe-in have produced the best sound I have had so far but the middle image can sometimes fall apart a bit (lack focus) and wondered if moving the speakers slightly closer together might help. You are right about it being long / laborious as I have found you can listen to several recordings and all is well but then you will find one that was acceptable before the tweaks but worse afterwards so getting an acceptable balance for various recording is also difficult. To be honest I am not sure I will get much better out of the current configuration because of the square room but I would like to get the best possible out of them. Trouble is you never really know if/when you have achieved this, especially as this is an unproven own-design.
 
I have found the method James sets out to work for me. However I do step 1 as a variant of his last paragraph.

I use Room Eq. Wizard (REW) to generate pink noise from one loudspeaker at a time (not too loud, and the low-pass filter engaged at 1,000 Hz or so to attenuate high frequency content that might damage tweeters). Then an omni-directional microphone at the listening position with REW's real-time analyzer running and displaying 20 Hz to 500 Hz or so, at 1/6 octave resolution.

I move each loudspeaker around separately for the flattest LF response I can get. It doesn't get really flat so I don't obsess too much and settle for improvement rather than perfection. But the bigger peaks can be made flatter and troughs partially filled in.

However I agree that final by-ear adjustments as per James' step 2 are always needed. And sometimes that involves moving a loudspeaker as well to get imaging right, so step 1 might need to be repeated to check flatness is still improved.
 
John,
Thanks for your thoughts which I appreciate. I didn't really want to go down this route to be honest because of the financial outlay. Especially as I have a condenser mic' and used this with an old integrated amp with a voltmeter on the output to get an idea of the relative output, using test tones which I found produced very "lumpy" results, confirming what I have read about the subject in that a room can give as much as +/- 10dB. Anyway I have slightly adjusted one of the upper baffles (RH speaker slightly forwards, equivalent to the 'tilt' that James mentioned) which has got the overall balance a little better, so I will continue to make very fine adjustments. It is surprising how a small adjustment of the upper baffle changes the integration markedly.
Thanks,
AP
 
I but the baffle adjustment back as before (so they measure identical) and moved the r/h speaker back a little further (only about 1mm) and reduced the toe-in of the left hand speaker slightly and this has improved the centre-image somewhat. I still think there is further tiny adjustment necessary as I can get some 'phasing' especially on some organ notes which are well positioned but sound similar to out-of-phase. Also, some vocals sound to far left; they are left of centre in 'phones, but not that far.
 
Some minor adjustments and I was quite pleased with the sound.... until playing Miles Davis Kind of Blue, especially track 5. The trumpet is fairly well centred, but the first sax sounds too large bridging from far right (higher pitch notes) to mid-image (lower pitched notes) whereas the sax left is hard left with some echoes mid-image so playing with toe-in as I suspect that this might be skewed, skewing the sound. That is unless anyone knows something that I don't about this recording?
Cheers.
AP
 
Carefully re-read James post and info from the website quoted earlier. Used a straight wooden lath to project the speaker baffles across onto the centre-line and where these crossed i marked a point. Measured the distance of the corner of the speaker cabinet to the crossing point and found the LH speaker was about 20mm further from this notional centre-line, so moved the LH speaker to make the offset the same. This improved imaging and bass weight somewhat. On Love: Forever Changes, there are several tracks where the intro is an acoustic guitar, hard right and found some notes were "wandering" towards the mid-image position. I disconnected the left channel and still observed the same effect, so I now know that the room is causing this effect. Bought a copy of Famous Blue Raincoat (but not the 20th aniv. edition so doesn't have "Ballad of a runaway horse") but the size / positioning of vocals pretty much mirrors what headphones show as some of the vocals have quite a large "halo" around them. Found this is a very good recording, although there seems to be a slight emphasis to sibilants in both headphones and speakers. DSOTM also sounds as good as I have ever heard with better differentiation where there are multiple overdubbed guitars, etc. Might try and just eek out a little further with very minor adjustments but I have come to the conclusion that the room is now the main stumbling block and probably won't allow further improvement.
Thank-you all who have contributed as this has vastly improved my appreciation of critical listening and understanding of the subject of speaker set-up.
AP
 
a.palfreyman said:
Some minor adjustments and I was quite pleased with the sound.... until playing Miles Davis Kind of Blue, especially track 5. The trumpet is fairly well centred, but the first sax sounds too large bridging from far right (higher pitch notes) to mid-image (lower pitched notes) whereas the sax left is hard left with some echoes mid-image so playing with toe-in as I suspect that this might be skewed, skewing the sound. That is unless anyone knows something that I don't about this recording?
Cheers.
AP
Click to expand...
I found it much harder to get the stereo image right than to get rid of the peaks and troughs...
 
Presumably very small incremental adjustments followed by lots of different albums?
Yes I have found so far that it is laborious to say the least. Passes a few hours though. :)
Otherwise the devil makes work for idle hands!
 
a.palfreyman said:
... I have come to the conclusion that the room is now the main stumbling block and probably won't allow further improvement.
Click to expand...
That is the unfortunate truth. More of us will have sub-optimal rooms than less. Whatever the imperfections (I had a -18dB suck out at centred narrowly at 80Hz in my previous house), careful positioning can help lessen the effect of a less-than-ideal room.
 
Yes,
I think that what I might try next, now that I have good overall balance is to slowly bring both speakers forwards by the same amount (to keep the coherence) and see if I can get rid of this reinforcement. Problem is, what am I going to trade this off with? Who knows :eek:
Thanks,
AP
 
Finally realised that although the balance was better there was still something not quite right as what should have been centred was offset left by about 6" with a 'hole' right of centre. Turns out the LH speaker was not toed in quite the same as the RH speaker so ended up increasing the LH toe-in by 1 degree. This seems to have balanced things out somewhat and got rid of the hole but only got about 1hr set like this over w/end so will see how things settle.
 
Been playing with toe-in and tried moving one or other speaker forwards / backwards to play with the timing to see if I can get rid of the right-of-centre "hole" but not really to any avail, even playing one channel via an RCA splitter into both channels to give a pseudo mono. Despite plenty of "stuff" in the room to absorb / diffuse behind and to the sides of the seating position, I have a wall to my left and a window to my right which has a set of light-weight curtains but with a second draped over the top close to the seated position. I can only assume that this is a major contributor to the imbalanced sound?
AP
 
I've learned to live with the imbalances.
I have big armchairs to the left, and a fireplace plus stove to the right, but...
my right ear has a high frequency drop-off which partially compensates.
If I listen to scales played on piano the image moves all over the place.
Curiously, classical music always sounds louder on the left channel than the right, whereas Rock etc is much more balanced.
 
Thanks Zippy,
I'd wondered if my own hearing (or lack of it from 5k upwards, gone by about 9-10k) was a further factor. Headphones sound more balanced through left-right so although rolled-off, I don't think I have any gross imbalance.
Could do with getting some references i.e. simple but excellent recordings with pin-sharp imaging. I have a small amount of Blue Note jazz which is convincing, but was thinking about a really good recording of such as a drum solo as cymbals seem to be really telling in the mid/top cross-over region, solo acoustic guitar, etc. I have some solo piano but these seem mixed to give an 'overlapped' image, presumably so all the bass isn't left and all the upper range isn't right. I bought a Murray Perahia recording of the Goldberg Variations which sounds like you've got you head 'under the cover', so to speak: almost as though you are inside the piano! Unfortunately recordings like Alan Parsons' Soundcheck are rare as hens teeth. Any suggestions?
 
I can't find the Soundcheck CD anywhere.
I've made do with a very old hifi News test disc cd but that's more to impress/scare your friends than genuine checks (garage door?).
 
Zippy,
Wasn't sure about your comment re garage door, but don't like 'garage' anyway other than 'garage days revisited' by Metallica :)
Anybody any suggestions on good solo recordings?
Cheers,
AP
 
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