My graphs - advice welcome

[TRiSS]

I recently added an svs pb10-nsd to my set(see my profile for the rest of my gear), and although happy with the product, I'm not entirely happy with how it behaves in my room... While "low level" bass (not too loud, not too "long") sounds mostly ok, any prolonged rumble seems disconnected from what you see on screen, (eg as in prolonged bass effects on a discs lfe channel (I even lessened the lfe level (not the sub level, the lfe level) by 10 db, because it was that disturbing).... A short "pound" effect, like something dropping,a short slam, etc will sound reasonably ok, but anything with longer background bass effects (eg the scene in lord of the rings - the fellowship of the ring at the beginning where you catch your first glimpse of mordor) sounds bad.

The sub is in a room which is about 4m * 4m (4m = 13.1 feet), with a sloped ceiling on one side.
| \
|_| --> like this

I don't have many placement options, since this room is quite "full", doubling as bedroom (only 2 options, left of the right speaker, or about dead front-center), and the first option came out as best. I made some REW graphs, with a RS SPL meter. Any advice is welcome, (eg, would equalizing the sub help? I guess the major issue is the dip 70-90, so perhaps not?)

sub only:


mains only:


mains + sub:


all three combined:


thanks in advance, oh wise people of the home theater

[Wayne A. Pflughaupt]

Any advice is welcome, (eg, would equalizing the sub help? I guess the major issue is the dip 70-90, so perhaps not?)

Yes, equalizing would help. Your response deviations below the crossover point are fairly broad and fairly symmetrical, which makes for easy equalizing.

Regards,
Wayne

[thewire]

TRiSS wrote:

but anything with longer background bass effects (eg the scene in lord of the rings - the fellowship of the ring at the beginning where you catch your first glimpse of mordor) sounds bad.

This is because of the peak at around 20Hz. If you want to eq that away it will take something with lower eq abilities than 20Hz. Also are you talking about the extended edition release in DTS? DTS does their own thing to the soundtrack, and as I have also read, it is not a good mix. Try the Dolby track.

[TRiSS]

Thanks for the answers.

Yes, equalizing would help. Your response deviations below the crossover point are fairly broad and fairly symmetrical, which makes for easy equalizing.

looks like Behringer will get another sale then... I was probably going to try it out anyway, but this is certainly good news...

This is because of the peak at around 20Hz. If you want to eq that away it will take something with lower eq abilities than 20Hz. Also are you talking about the extended edition release in DTS? DTS does their own thing to the soundtrack, and as I have also read, it is not a good mix. Try the Dolby track.

That peak at 20 is something strange: it shows up consistently in my measurements, but if I play a sine tone in that area, it doesn't seem to register that loud on the meter.... Also, by ear, I don't hear much if anything in that range. Could this bump "originate" from other frequencies? Or perhaps something rattling? I have both the extended DTS version and the regular dolby theatrical version, and both have this problem I described earlier. Also, it is not limited to those disks, eg some scenes in Finding Nemo (parts of when they are in the stream with the turtles) has it as well... In contrast, the glass tap scene from Nemo sounds rather ok (being shorter bursts of bass).

[thewire]

I just did a quick demo of the scene in my HT. I'm only using 3 subs right now and they are at equal distance of my front wall. Two are 5 1/2" from the side walls and 6" from the lower bass traps. I'm not sure what the target is exactly, I didn't check, but my speakers are set to small. Levels are fixed levels on the subs and no adjustment of the output of my XA2 set at 0. I record the ring falling to the ground at 99dB uncorrected and the cheeks on my face shook. I took some lamps out of the room.

I found one area in my tile ceiling that I am currently cleaning to rattle because it was not fit, probobly some air gap. The felt the door pounding really hard when I walked into sit down while they are rushing into the attack. When the ring dropped I felt the pressure coming from the right front corner of my room. This is the area in my room that without having placed a sub in each corner, causes ringing in the 20Hz - 30Hz area.

I would say that the problem is that you have an area that is very strong and is not flexing/absorbing low frequency energy in the room, and a very fast reflection is coming off of that structure/surface from an area with little absorption. If the thud of the ring for example last longer than a split second and you are not hearing the sound of the ring and sand when it drops, this may be related to being underpowered/lacking headroom. I would experement with placing the sub from the wall at different distances, inches at a time, until this improves as this is much to do with the room itself. Best to avoid a corner if it is troublesome. Take a look at the waterfall feature in REW and look for a dip in the lower frequency that is small and looks kind of like a hole that may be located in my estimate very far such as in the 250 - 400ms range. Then experement with placement to improve that.

[TRiSS]

I would say that the problem is that you have an area that is very strong and is not flexing/absorbing low frequency energy in the room, and a very fast reflection is coming off of that structure/surface from an area with little absorption. If the thud of the ring for example last longer than a split second and you are not hearing the sound of the ring and sand when it drops, this may be related to being underpowered/lacking headroom. I would experement with placing the sub from the wall at different distances, inches at a time, until this improves as this is much to do with the room itself. Best to avoid a corner if it is troublesome. Take a look at the waterfall feature in REW and look for a dip in the lower frequency that is small and looks kind of like a hole that may be located in my estimate very far such as in the 250 - 400ms range.

Not had time yet to re-listen that bit to listen for the details you mentioned, but will do that in the coming days....
The surface you describe could be many things here, perhaps the sloped sidewall that has a wooden surface, or a nearby "storage crate" made out of thick wood... There's also a bed nearby, and the subwoofer somewhat fires into the cavity under the bed, could play a part as well I'll try shifting some stuff around in the near future...


here's the waterfall of the sub only, crossover at 80 hz, though I have no idea what to look for to be honest (I hope I saved the graph in a correct way...):

[brucek]

I hope I saved the graph in a correct way

No, use LOG mode rather than the LIN mode that you have used for the waterfall. The Freq Axis button changes between LIN and LOG.

Use the same axis as you would for a frequency plot of vertical = 45dB-105dB and horizontal = 15Hz-200Hz.

brucek

[TRiSS]

sorry about that...

corrected version:

[Wayne A. Pflughaupt]

I'd say that's a better-than-average waterfall. Fairly uniform decay across the board for the most part, fully truncated by 450 ms (at least down to 45 dB).

Regards,
Wayne

[TRiSS]

I got myself a FBQ2496 last week, and an ECM8000 mic, and started measuring and equalising.

Sub only, 80hz crossover, no EQ:


REW proposed the following:
Filter 1: ON PEQ Fc 42,3Hz Gain -13,0dB BW Oct 0,500
Filter 2: ON PEQ Fc 85,3Hz Gain -4,0dB BW Oct 0,125
Filter 3: ON PEQ Fc 140,0Hz Gain -5,5dB BW Oct 0,100
Filter 4: ON PEQ Fc 155,2Hz Gain -4,5dB BW Oct 0,067
Filter 5: ON PEQ Fc 180,3Hz Gain -3,0dB BW Oct 0,033
Filter 6: ON PEQ Fc 195,4Hz Gain -4,5dB BW Oct 0,143

to which I added
ON PEQ Fc 20,0Hz Gain -10,0dB BW Oct 0,750 (--> to get rid of the 20hz bump)
ON PEQ Fc 52,0Hz Gain -7,0dB BW Oct 0,250 (--> the 42 hz rew filter left a fairly large peak higher up)


which got me the following response:




looks OK-ish to me, and sounds much better then without EQ as well....
I'm curious to know what more knowledgeable people then myself think of this?

Already a big thanks to the people here on this forum, and especially to the creator(s) of rew (without which I probably wouldn't have bothered to measure responses etc. and would have been stuck with muddy bass)! The Behringer folks should give you guys a percentage of each BFD/FBQ sold!!

[brucek]

I'm curious to know

I would keep filters 1,2,3 and lose the rest.

Filtering at or above the crossover has decreasing effect as the frequency increases (after the mains are added).

Generally, we equalize up to the crossover point and then add the mains and do a sub+mains measure (measuring exactly the same as with the sub alone) and then re-evaluate the situation.

First the phase of the sub is adjusted to try and get the smoothest crossover region and then if needed a bit of eq can be added.

brucek

[TRiSS]

Do you mean as in keep
set1)
Filter 1: ON PEQ Fc 42,3Hz Gain -13,0dB BW Oct 0,500
Filter 2: ON PEQ Fc 20,0Hz Gain -10,0dB BW Oct 0,750
Filter 3: ON PEQ Fc 52,0Hz Gain -7,0dB BW Oct 0,250


or as in
set2)
Filter 1: ON PEQ Fc 42,3Hz Gain -13,0dB BW Oct 0,500
Filter 2: ON PEQ Fc 85,3Hz Gain -4,0dB BW Oct 0,125
Filter 3: ON PEQ Fc 140,0Hz Gain -5,5dB BW Oct 0,100


I'm assuming you mean set1, since the set2 contains 2 filters at/above crossover, which you come to tell me will not help much....

[brucek]

This may be clearer....



brucek

[Wayne A. Pflughaupt]

What happened between your first graph and your recent one?

Your 45 Hz problem is now narrower and more pronounced than it was before. The first graph would have been an easy EQ.

Regards,
Wayne

[TRiSS]

Thanks, now I understand better indeed... A measurement with mains + sub indeed doesn't show much difference with or without the filters above 80....

This is what I get (sub (equalised) + mains):

the yellowish is phase at 0 degree, the green at 90, and the purple at 180



Any advise on which would be best to go with will be greatly appreciated....

Wayne A. Pflughaupt wrote:

What happened between your first graph and your recent one?

Your 45 Hz problem is now narrower and more pronounced than it was before. The first graph would have been an easy EQ.

Regards,
Wayne

The difference is the first one is measured with the RS SPL stacked on some boxes on my chair, the second one with the ECM8000 using a mic stand on the chair. Nothing much changed apart from that.

[brucek]

Now you have to determine if the nasty dip between 100-120Hz is from one or the other mains, or simply an interaction between the two.

Try a mains only, one at a time (still use exactly the same measurement method for a sub you have been using except turn off the sub - still measure from 0-200Hz - no change).
Do one main at a time and then both together to see if you'll be able to move one or both mains a bit to remove the cancellation.

Then redo the sub + main after you've (hopefully) cleared that dip.

brucek.

[TRiSS]

L = blue
R = green




Both seem to have the dip. I tried moving the speaker(s) around a bit, but haven't been able to do more then make the dip a bit narrower, and to have that tiny improvement I have to put the speaker someplace that's really inconvenient....

I could try to put the x-over at 120 (I can set it 80,100 or 120)in the receiver, and boost the frequencies a bit with the EQ, but not too sure if that'll be a good idea (bass localization issues? will it even work? and it's a bit a shame to crossover "decent" floorstanders that high )

[brucek]

Yeah, I wouldn't change the crossover for the same reasons you gave.

Too bad, both speakers have about the same room problem, and moving them a reasonable distance didn't correct it.

I guess this would be where room treatments would come in.

Anyway, you can see that REW is handy for finding out what's right and wrong about your system. All you can do is play around and get the best plots you can....

brucek

[TRiSS]

brucek wrote:

Yeah, I wouldn't change the crossover for the same reasons you gave.

Too bad, both speakers have about the same room problem, and moving them a reasonable distance didn't correct it.

I guess this would be where room treatments would come in.

Anyway, you can see that REW is handy for finding out what's right and wrong about your system. All you can do is play around and get the best plots you can....

brucek

Yes, too bad, but I'll have to live with it, at least for now.... I find comfort in the fact that it sounds already a lot better then when I started this thread, and that's at least something! Also, thanks to you helpful people, I learned some new things, which can't be bad

Room treatments are out of the question at this moment, not at the least because there 'd be hardly any place to put any.... Out of interest, what kind of things would we be talking about? The so-called bass traps? Or are they only helpfull for reducing peaks?