No Bob, it's sound pressure level instead of distance. With the sumiko Master Set the distances are rarely equal, because of the room annomalies. The Master Set takes into account multiple interactions at once.
Dave |
Hi Dave, you said, " It's easiest to imagine thinking of a mono signal through a stereo system. It'll come equally out of each speaker, so time alignment of the two speakers must be precise or you hear an inbalance and/or a smearing."
You you are saying then, that the first issue to address is exact measurement of speaker to ear distance and extrapolating that out, probably exact placement of speakers and listener within the room? To avoid odd arrival time of the original sound and reflected sound.
Is that correct?
Bob |
Yes Bob, very similar to that, but not exactly. With phase you can have speakers literally pushing a pulling against each other. With IMD it's more about timing of the direct signals arriving in-phase but not at the same time. It's easiest to imagine thinking of a mono signal through a stereo system. It'll come equally out of each speaker, so time alignment of the two speakers must be precise or you hear an inbalance and/or a smearing.
In an anechoeic environment that would be simply time alignment, but then you add the room interaction and the nodes and you do get cancellation, emphasis and timing all rolled together. In my experience, you perceive it as added harshness and loudness. When it's minimized (I doubt that it can be eliminated) the loudess measured with an SPL meter is the same, but your perception is that the loudness declined. It's amazing. You find yourself comfortably listening to music 12dB or so louder.
My understanding is only as a layman and from the little I've been told by Rod Thomson based on his training by Sumiko.
Dave |
Hi Dave, Thanks for the answer regarding IM distortion. Is this associated with phase? Such as main speaker to sub?
Bob |
I own (and like) Cremonas, but you might want to think about speakers with a more limited dispersion pattern. If you're willing to move the speakers out into the room when listening (and back when you're done) a narrow planar (Final, Martin-Logan, etc) might do the trick. If you're unwilling to schlep, you might consider a horn or horn/subwoofer set-up. Either way, you'll be pouring less off axis energy into the side walls.
Good luck.
Marty |
IM distortion is also caused by speaker-to-speaker timing misalignments. If you think it's important for the drivers within a speaker to be properly time aligned, then you'll likely agree that getting both speaker firing in sychronicity will also be beneficial. It very critical, yet easy to hear when done correctly.
Dave |
Hi Newbee said, "BTW, if you do this, buy some graph paper and keep careful notes of your set up distances - it can get a little complex trying to keep all of these in your head, as it will also give you some visual clues about what you can change, cannot change, and whether its lspeakers or listening position that is causing the issues you like or dislike.'
I say, just download the Room EQ Wizard for FREE and you dont need graph paper just click and save the measurements. Also 1/3 octave test tones are not enough, you need much finer measurements than that to really see what is going on in your room.
Hi Dave, you said "Until you minimize IM distortion you can't enjoy your system to the max, no matter how flat the EQ. My method is set the speakers first, for the best combination of low IM Distortion and minimal bass nodes, then start addressing any problems that remain with room treatments and/or active EQ."
I know what IM distortion is, but what are you talking about? How are you adressing IM distortion with your speakers placement? Or are you talking about IM distortion in equipment?
Bob |
Bob, you can get the EQ "right" at any listening position, but if you left the IM distortion in then it'll sound like CRAP, no matter what speaker you use. Go to any audio show and you'll hear it in room after room. (Harsh, edgy, grating sound from really good components).
Like you said, "You paid for the speaker, why not get all you can from them?". Until you minimize IM distortion you can't enjoy your system to the max, no matter how flat the EQ. My method is set the speakers first, for the best combination of low IM Distortion and minimal bass nodes, then start addressing any problems that remain with room treatments and/or active EQ.
Dave |
I agree with Bob;
1) Common sense - use rule of thumb configurations
2) Perform in room measurememts
3) Listen and decide what works best for you (usually a compromise is needed anyway as there is no "perfect position" for all aspects of the sound)
Why are measurements so useful - because it is very hard to be objective in listening tests and the most exciting engaging position may actually be the worst in terms of accuracy and ultimate musical clarity/enjoyment...the old boom boom tizz setup that most people fall for....impressive...wow I can really hear the bass...and the highs are scintillating ....sure but it is not musical cause you just downplayed the most important element the midrange... |
Hi Dave, Have you ever done an in room response of you room?
The ultimate answer to this issue is bass traps. The last approach is EQ after all room treatment is exhausted by either aesthetic reasons, AAF (audiophile acceptance factor, we can't blame it all on "the wife")or WAF.
As far as IM distortion, "how it sounds", freq extensions etc. that is all up to the system and its owner desires. I believe the better the in room response becomes (and you dont need to hire a "Master Set" as you can do this yourself with REW) the better. Even the worst speakers deserve this. You paid for the speaker, why not get all you can from them, whether you like the speakers or your equipment is "good enough" is another story. A tape measure tells you nothing, except that speakers should be (obviously) set within the room and seating position within a "1/4 inch" or some such.
Moving your speakers 1/4 inch can make a big difference in sound, and this can be measured.
Bob |
Bob, let's not get into that 83dB stuff again. We'll NEVER agree on that, but you're having fun with it and are welcome your concept.
As for measuring your way to proper setup, I was thinking of tape-measure, not SPL. Indeed, SPL can help, but only after you've optimized as best you can with Master Set and still want to further tame a node, either with traps or active EQ (attenuation only) such as Rives.
You've got to get the speaker working together coherantly and minimize intermodulation distortion. Once you've done that, then tweaking with room treatment or EQ can get you even flatter. Intermodualtion distortion is often heard as glare and loudness. When it's controlled, then you can actually listen several dB higher without fatigue. Said another way, 83dB with intermodulation distortion sounds louder and more fatiguing than 88dB without intermodulation distortion.
So, I say, address this first. Moving the speakers a fraction of an inch can make a big difference in perceived sound.
Dave |
Hell, Hi Dcstep, you said, "Most people think that you can measure your way to the best placement, but it doesn't work. See the following thread for something that actually works:" Which has the following quote:
"Anyway, Rod accepted the challenge and The Ballad of the Runaway Horse soon filled the room. I could attempt to reveal the whole process, but that would be futile. I witnessed the whole thing, start to finish, and actually helped a time or two and I couldnt replicate it in a new speaker positions. I will say that he started with the bass, beginning with the speakers just a couple of inches from the rear wall and then moving them out an back while listening to the nodes. He worked the left speaker first, and then the right, focusing on getting the bass balanced between the two speakers, but with no nasty nodes in the midrange. Toe-in and rake angle were critical to the midrange and balance, but I think that getting the bass right and avoiding the midrange nodes was the single most important factors. Still, its a comprehensive system that youre not going to be able to read about and then do. Listening and hearing the nodes takes some training. I was amazed to hear MAJOR changes with just ¼ of movement."
What do you think is wrong with measuring an in room response of your system? If moving the speakers as a Master Sumiko dealer does to find the best freq response in a room, why not do it by a REW measurement? Do you believe he would be doing something different? I mean, that, if we both agree that moving speakers changes the inroom response by going in and out of nulls and peaks and yes, some have a percieved better or worse sound position by just this fact, why not just measure it and use your ears for the position you prefer. But at least this way you know where the nulls and peaks are through an analysis of your room. Plus it is free and repeatable.
Then, Dave, all you have to do is go for 83db playback level! You just knew I had to throw that in! But please ignore that issue to not confuse everyone.
Bob |
Not possible. 3 feet off the wall in a 112 width will have the mains less than 4 feet apart. The speakers are about a foot in width. Well just do the best you can in terms of distance from side walls and also toe them inwards to reduce the magnitude of side wall reflections (effective once you get past about 40 degrees). |
Most people think that you can measure your way to the best placement, but it doesn't work. See the following thread for something that actually works:
http://forum.audiogon.com/cgi-bin/fr.pl?rspkr&1197744079&openmine&zzDcstep&4&5#Dcstep |
Finally use a PEQ or TACT or PARC to fix the worst of the room modes I decided on the Audyssey EQ after auditioning for some time. I auditioned 2 other EQ's. Rule of thumb - speakers placed well out into the room will excite less room modes. Keep away from side walls (at least three feet). Not possible. 3 feet off the wall in a 112 width will have the mains less than 4 feet apart. The speakers are about a foot in width. |
Actually your room is not quite that small. A bit narrow but otherwise I'd consider this a smaller mid-size room. I only have 8' usable width. I have fire place on 1 side and bookshelves on the other. I also have cabinets in the fron and back of the room. So even though the room might no be so small, usable space is. |
Very cool room BTW. Thanks. But from what I can tell from your picts. Old pics. Sorry. The actual room is the same, but I did many tweaks over the years. A professional once cam and moved the speakers by ears. I also bought a BIG 2 seater HT seat. I put curtains to block off the bay window amongst many other tweaks. I also have an EQ. I will have around 8 possible response graphs for every speaker based on different placements. My current plan in order of priority: 1) The placement that has the least BIG peaks. 2) The placement that has the least BIG dips. 3) Flattest Bass Response |
Rule of thumb - speakers placed well out into the room will excite less room modes. Keep away from side walls (at least three feet). Sit at around 40% or room length (do not sit with back against wall - very very bad) Subs are best well out into the room against the left or right wall about 3 feet in front of your mains. Try walking around the room while listening - the best positions or setup will have the broadest sweetspot and most even sound.
You will be surprised but rule of thumb works best - it won't give you that "jaw dropping" sound that you get when something is wrong and one note seems to rumble the whole room - so be careful - best setup is actually the most neutral and the least "sizzle" or "emphasis".
Finally use a PEQ or TACT or PARC to fix the worst of the room modes (notch down the "peaks" and leave the nulls alone and above all DO NOT aim for absolutely perfectly flat with thousands of filters - it often doesn't sound right at all - just "flatten" the bumps to with 3 to 6 db of the average and you may find it the most natural sounding - the lower you go in frequency towards 20 Hz the less relevant it becomes to get absolutely flat - flatish between 40 and 100 Hz is most important to achieve!!) |
Actually your room is not quite that small. A bit narrow but otherwise I'd consider this a smaller mid-size room.
Anywhere you place your speakers is a compromise. The goal of course is to find the least compromising placement. As you can see there are several ways to find this spot. I just do it by ear which can take a very long time. In my previous room it took me about 9 months to find that spot. But I also only moved the speakers maybe 3 or 4 times a month.
But from what I can tell from your picts, I would start by bringing your speakers about 4ft further out from the back wall and perhaps a foot closer to the side walls as the initial starting point.
From there, every so often move the speakers out, in, forward or back in about 2 inch increments. Eventually you'll find that least compromising location.
I would also suggest shutting down the subwoofer while searching for this least compromising location as it will only add to the confusion.
Very cool room BTW.
-IMO |
Hello, do yourself a favor and search Real Traps bass traps and the Room EQ Wizard at Home Theater Shack. Use the EQ Wizard and do a graph of your romm and post the results on the site and you will recieve all types of suggestions and go from there. It will be the easiest way for you to tune your system with room tratments or without room treatments or with EQ. You need to do your research there.
Bob |
I see possibilities:
I can simply take the flattest response.
Or I can take the flattest bass response.
Or I can choose the flattest human voice range response. |
Helps a lot. Thanks. I will research.
I want to take baby steps for now.
Acoustic treatment is not an option.
For step #1 I want to do speaker placement. I have a very small room so there is not that much leeway. I figure there are about 8 positions each main can go. (That's counting 1 inch increments.) I hired a professional to move the speakers and give me response graphs for each placement. He's coming in 2 weeks.
Also, I want to take a few measurements to see if my sub placement near the L main interferes too much with L main. I would give up a flatter bass response for a flatter main response. |
Flat isn't possible except under the most ideal conditions in a fairly large room. Placement of speakers too close to the wall behind them is the biggestest contributor to getting an uneven frequency response below, say, 500 hz.
The next biggest contributor is location of the listening chair. Optimize both and you will still have dips and bumps but there are some room dimensional suck outs or humps you just can't get rid of. BTW frequency response much above 500 hz has more to do with your equipment synergy, speaker toe in, and killing first reflection points on the side walls, floor, and ceiling (if possible).
I'd suggest, if you have not alread done so read so set up theories which will give you some god starting points. Cardas for one, Physic's for another, and look up Rives site - last time I was there he has a CARA program which just might even include your speakers. That program works well, but all of these are just starting points.
With a SPL meter (Radio Shack), a test disc with 1/3d octave test tones (Stereophile) you can pretty much do your own set up work. It takes a lot of time and experimentation so patience will be necessary but the initial frequency response flattening isn't very hard. Its the subsequent fine tuning that takes a lot of small moves and time listening to the results.
BTW, if you do this, buy some graph paper and keep careful notes of your set up distances - it can get a little complex trying to keep all of these in your head, as it will also give you some visual clues about what you can change, cannot change, and whether its lspeakers or listening position that is causing the issues you like or dislike.
Hope that helps a bit. |
