Nulls and sub crawls and fun stuff.

[rdgrimes]

So I'm working on setup of my new 1400 Array, 880 and 1500 subs.

A brief breakdown of the rough setup. The 1400 are about 1 ft from the front wall in a large rectangular room, both 1500 are about in the middle of the room right behind the main LP. Main LP is about 12 ft back from the 1400 and roughly center of the room with an equal sized space behind.

So I kept getting odd results with the PEQ setup in my Yamaha AVR. Missing a significant amount of mid bass in the main LP, the 1400 just sound flat. Then I noticed that if I lean forward off the sofa there's all kinds of bass. Damn. So out come the sine wave tones and I'm crawling around like a fool.
From 20-40Hz everything is pretty good, there's a small null area behind the sofa (LP) but it doesn't matter. So placement of the 1500 pair is adequate.
But there's a big null covering the entire sofa, and pretty much only the sofa, from roughly 50-100 Hz. Leaning forward a foot off the sofa - no null.

The 1400 are on a 40Hz crossover to the 1500. I tried shifting that upwards, 60-80-90, and each step increased the levels on the sofa, but also increased the levels in front of the sofa. The standing wave in front of the sofa is significant, and is about 8-10 feet from the 1400 baffles.

Exact same setup with the previous PS1400-PT800 stacks did not have this issue, or at least not to a noticeable extent. They are not as deep though, so were probably another 6" out from the wall.

So---
Changing sub locations doesn't seem to be called for, they appear to be near optimal for placement and levels.
Moving the sofa forward or back is an option, but not something I want to do unless I'm sure it will help and won't just move the null with it. Pulling the 1400 out from the wall a little bit is an option, what will that do if anything?

[rdgrimes]

I temporarily pulled the sofa forward about 2 ft and the null seemed to move with it - at least to some extent. It seems this sofa is acting as sort of a big bass trap. I never would have expected that.

I may try using the AVRs multi-position EQ setup routine and see if that helps, but I don't expect it to do anything about the null itself.

[Ed Zeppeli]

What kind of EQ does the AVR have; Audyssey? I didn't think too many AVRs even mess with sub frequencies in a lot of cases. Noteably, Audyssey XT 32 does and is supposedly good.

Do you have many options on sub placement?

[rdgrimes]

This doesn't appear to have anything to do with the subs, its mid-bass from the 1400 that's evaporating. Yamaha uses their own system called YPAO.
Anyhow, this is a room problem that EQ don't help much.

[LowPhreak]

Exact same setup with the previous PS1400-PT800 stacks did not have this issue, or at least not to a noticeable extent. They are not as deep though, so were probably another 6" out from the wall.

... Pulling the 1400 out from the wall a little bit is an option, what will that do if anything?

I would certainly try that. It could move the null's position relative to the LP or change the frequency enough to make a difference. 3"-6" change in speaker position has helped me in many rooms, but not always of course.

Have you tried speaker placement calculators such as this? http://noaudiophile.com/speakercalc/ They can be a great help to get you in the ballpark then dial in from there. Don't be afraid to get out the tape measure and a straight edge to measure both speakers to the same symmetrical positions and angles (once you get the low end settled as best you can to the room). Guessimating but being off by 1/4"-1/2" can be lousy for the imaging/soundstaging.

[rdgrimes]

I ran setup using multi-position mode using 5 positions surrounding the main LP. This seemed to help. I'm convinced now that the sofa itself is a huge bass trap. Moving the sofa or moving the speakers out has no real effect. I'm sitting on a big bass trap. Its hugely noticeable playing a sine wave, but not very much playing music, so I may just have to live with it. I compensate with the EQ by bumping 61Hz a couple db.

I can see me at the furniture store explaining that I need to test-drive a new sofa at home to see if it traps bass.

[Triumph Don]

I'm sure I am not alone here, could you post some pictures of this way cool modern stuff off the crate and out of the boxes?

[rusty jefferson]

Congratulations on the new system.

So I'm working on setup of my new 1400 Array, 880 and 1500 subs.

A brief breakdown of the rough setup. The 1400 are about 1 ft from the front wall in a large rectangular room, both 1500 are about in the middle of the room right behind the main LP. Main LP is about 12 ft back from the 1400 and roughly center of the room with an equal sized space behind. .....

In a largish room as you've described, I think the 1400s should be 7'-9' off the front wall as opposed to only a foot or so. It may help the null, and will certainly improve the soundstage. I don't think the sofa is absorbing the bass. Just normal room anomalies.

[rdgrimes]

, I think the 1400s should be 7'-9' off the front wall as opposed to only a foot or so. .

This sort of suggestion always make me smile. In most rooms a foot or two is all there is to play with.

Anyhow after more use, I think the multi-point setup has addressed the issue well enough. I'm pretty happy with what I'm hearing now. With music I don't hear anything like what I hear with sine waves (like I did before). I'm comfortable with where things are at.

[audiomagnate]

I'm glad you've worked it out and that you have my dream system in place. As to a bass null at the sweet spot of your listening couch, I'm pretty sure that's Murphy's first law of room acoustics.

[rdgrimes]

I'm pretty sure that's Murphy's first law of room acoustics.

I'm well familiar with that one. There's also the rule about auto-setup routines in AVRs, which is that no two measurements will produce the same results.

[Mr. Widget]

There's also the rule about auto-setup routines in AVRs, which is that no two measurements will produce the same results.

That has absolutely been my experience. Do you feel that your AVR's "correction" is better than none at all? For me that is always the acid test.


Widget

[rusty jefferson]

This sort of suggestion always make me smile. In most rooms a foot or two is all there is to play with. .....

Well, glad I could make you smile anyway.

It sounded like you were interested in improving a bass null. I believe my suggestion would help. You didn't mention you were unable or uninterested in having them more than a foot or so from the front wall. You specifically asked about pulling them out from the wall.


I just looked at the calculator link LowPhreak provided (http://noaudiophile.com/speakercalc/) and for a room 20'x25' (my guess), the closest recommended position was about 4' from the front wall, and the average starting position was about 8'. I understand now that's not in the cards for you.

I still believe your sofa isn't causing the null. Your room, and the speaker placement in the room are.

...... I'm comfortable with where things are at.

That's all that matters.

[rdgrimes]

That has absolutely been my experience. Do you feel that your AVR's "correction" is better than none at all? For me that is always the acid test.


Widget

Absolutely. I really need the EQ in my room. But I do always take the time to compare it with and without. And the processor lets me re-adjust all the PEQ manually.

[LowPhreak]

I just looked at the calculator link LowPhreak provided (http://noaudiophile.com/speakercalc/) and for a room 20'x25' (my guess), the closest recommended position was about 4' from the front wall, and the average starting position was about 8'. I understand now that's not in the cards for you.

I still believe your sofa isn't causing the null. Your room, and the speaker placement in the room are.

I don't think it's the sofa either, but a function of the room dimensions and speaker placement. Those are usually the greatest determinant factors in the low end. Fairly simple acoustical physics here folks.

There are a few ways to use that calc. You don't always have to use all 3 dimensions as it calculates, sometimes just the speaker-to-side-wall is enough, or the speaker (front of baffle)-to-rear-wall distance, or the listening position. Sometimes 2 of the 3 is sufficient to find very good response, or just one of them may eliminate most of a bump or null. You just have to put in some effort and try different positions...and measure. And of course there is always room to adjust by ear.

Yes it may be tough to hump these monoliths around much, but hey - you wanted a 100-200+ lb. speaker so get yerass to work!

Let's say you can't realistically use the 'Cardas' position because the speakers can't be that far into the room, or even some of the other positions. You could however use the distance to the side wall and perhaps the LP, and find a multiple of the rear wall distance that may help. You'll need a little ingenuity here.

Not sure if it's mentioned in that calc but I've found often that a multiple of 1.2 times the distance between the center of the speakers is a good spot to start for the LP; sometimes it proves to be the best overall position, not the "traditional" equilateral triangle you see given as rule-of-thumb in your standard Owner's Manual. (Aren't they like Christmas fruitcakes - someone made the first one and it's just been passed around for the last 50 years?)

I'm actually surprised that with the knowledge and expertise around here that more LH'ers don't discuss this very important aspect of their often quite expensive systems. You can't always just plop down a big-assed speaker & amp rig and think it's going to be audio nirvana, and I don't care who designed it or what it costs. Obviously we saw that the last time someone got on here with a pair of LaScalas and Studio 590s.