Choppy Bass

[progers13]

Originally Posted by sentinel41

I'll try and explain this simply, sorry if it comes across as patronizing. It really depends on your setup, In 90% of cases 0 is the best option. Everything the original sound signal passes through adds a little bit of delay and changes the phase of the signal. You can also do this with speakers by hooking up the right and left connections backwards. A phase difference of 180 means that instead of your speaker pushing out when the signal tells it to, it sucks in because the signal is reversed at that point. To correct this problem with subwoofers companies add phase control that allow you to add even more phase to push the signal back around to 0. For most peoples setups their phase will likely not be push far enough away from 0 to justify using the phase control. You only want to use phase if you can push the signal back around to 0 (or closer to it then you are currently at).

Newer receivers have calibration functions that also test if your speakers are out of phase. I don't know if it works for subs tho. If you want help finding the phase of your sub I can help. I'd wager that 0 would be a better option then 180, but I can't know for sure with out having you run a test.

This is true of 1 sub in a setup, in which case you would almost always want it to be set at 0. However, in cases of 2 or more subs, phase becomes a bigger issue. When I added my second sub last month, I used the SPL meter to calibrate both individually. But when I turned them both on at the same time and ran test tones, I could clearly hear a void on the right half of my room. I even had to touch my sub to make sure it was firing (it was, but it was cancelling due to phase). This was solved by adjusting the variable phase knob on one of the subs from 0 to 180, and now I have even bass response across the whole room. -Thanks again to db01 (Dennis) for pointing me in the right direction to solve this little mystery I had.

[dewd]

Originally Posted by eyekyu

ive since re-ran audyssey since my 1st post. i can get as low as -15db, which is where audyssey puts the sub no matter when in my roon it is.
ive set my LFE to 120hz and the sub is at -8db

Then the volume on the sub is too high. You need the system calibrated properly first, then you can troubleshoot the choppyness (if it still exists).

[Fors*]

Originally Posted by JBL4645

Go over to home theatre shack http://www.hometheatershack.com/forums/rew-forum/ and sign up for there remarkable REW Room Equalizer Wizard. Your goal is aiming for flat near flat response that has less dips or nulls because nulls are just plan hopeless to address with EQ boosting that would but enormous stress on the amp with near clipping!

The odd peaks or two can be reduced over an average near flat response.

You can try moving the seating forwards and backwards to find the spot where the sub is near flat with less boom around 30Hz to 40Hz and possible 60Hz to 70Hz.

My room has the issues its not cinema auditorium size its common living room. I have the sofa placed fairly close to front at present to get near flat before EQ I have less nulls. If shift it back I’m in the few (null zones) that sucks the 40Hz range down and I need the 40Hz as most common lows in the LFE.1 are cantered around that mark.

It also keeps less power to drive some frequencies without over doing it. The lows that sound way too deep loud peaky high, needs less level! Then your stuffed for the other frequencies because there far too low down in level and you need those low tones.

+1...I used REW and it did a good job. It takes a little computer know-how to set it up though. Luckily I had another member walk me thru the set-up or I would never had known what I was doing.

[kareface]

Originally Posted by eyekyu

120hz, and the fronts are set to full band?

If radically adjusting the gain didn't help and the choppyness is very audible (it's clear that it should be the normal limitation of the sub) then I have to agree with Big Daddy and say your amps likely faulty.

There are a few things that are odd, that I don't think will impact this fact. The volume of your sub is set too high, you should turn it down and rerun Audyssey till you achieve around a 0 for the sub level. After getting a 0, you should set your gain to it's lowest setting and play something with a lot of bass. Turn the gain knob up slowly until you start hearing audible distortion. Once you get that far you should turn it a few notches down. Rerun Audyssey once more and see if that helps at all. I suspect that it won't as it sounds like it's something more problematic.

Originally Posted by JBL4645

Go over to home theatre shack http://www.hometheatershack.com/forums/rew-forum/ and sign up for there remarkable REW Room Equalizer Wizard. Your goal is aiming for flat near flat response that has less dips or nulls because nulls are just plan hopeless to address with EQ boosting that would but enormous stress on the amp with near clipping!

I love REW, great plugin. However I don't think that this is the problem at hand. I could be mistaken but I suspect one of the 2 problems I've mentioned in this thread.

Originally Posted by progers13

This is true of 1 sub in a setup, in which case you would almost always want it to be set at 0. However, in cases of 2 or more subs, phase becomes a bigger issue. When I added my second sub last month, I used the SPL meter to calibrate both individually. But when I turned them both on at the same time and ran test tones, I could clearly hear a void on the right half of my room. I even had to touch my sub to make sure it was firing (it was, but it was cancelling due to phase). This was solved by adjusting the variable phase knob on one of the subs from 0 to 180, and now I have even bass response across the whole room. -Thanks again to db01 (Dennis) for pointing me in the right direction to solve this little mystery I had.

This is one of the possible solutions. The downside to this solution is you're reducing the subsonic output of one of the subs by running it out of phase. In my case I managed to find a 2 sub configuration that allowed them to remain in phase. Asymmetrical subwoofer configurations and odd shaped rooms are more forgiving for phase cancellation.

[Steve]

Originally Posted by sarge1976

Hi, I tried setting the phase to 0 for a few hours and I noticed less bass from my sub so I set it back to 180. Does the crossover on my sub and on my reciever have to be set to the same hz? example- AVR-80hz and Sub-80hz, Thanks

I don't know for sure, but it might be a good idea to re-run Audyssey after you change the phase of your sub.

As far as the crossover goes, it's always been my understanding that you should turn the crossover knob on the sub as high as it will go and use the crossover setting in your receiver. The idea here is that the sub will basically use whichever crossover setting is set lower. An example would be that if your receiver's crossover is set at 80 Hz and the crossover knob on the sub is set at 60 Hz, then your sub will only play up to 60 Hz. The problem this presents is that because the receiver is set at 80 Hz, your regular speakers will start to roll off at 80 Hz as the receiver begins to transition the sound over to the subwoofer, which is only playing from 60 Hz down. This means you will have a 'hole' in the audio between 60 and 80 Hz. Turning the crossover knob on the sub all the way up essentially removes it from the equation and allows everything that has to do with the crossover to be handled in the receiver.

[eyekyu]

Originally Posted by sentinel41

If radically adjusting the gain didn't help and the choppyness is very audible (it's clear that it should be the normal limitation of the sub) then I have to agree with Big Daddy and say your amps likely faulty.

There are a few things that are odd, that I don't think will impact this fact. The volume of your sub is set too high, you should turn it down and rerun Audyssey till you achieve around a 0 for the sub level. After getting a 0, you should set your gain to it's lowest setting and play something with a lot of bass. Turn the gain knob up slowly until you start hearing audible distortion. Once you get that far you should turn it a few notches down. Rerun Audyssey once more and see if that helps at all. I suspect that it won't as it sounds like it's something more problematic.

anything i should mess with on the receiver or just get the sub close to 0, should i leave the crossover on the sub to max

[Steve]

Originally Posted by eyekyu

anything i should mess with on the receiver or just get the sub close to 0, should i leave the crossover on the sub to max

Just to be clear you can use a crossover setting of 80 Hz (or 60 or whatever), but the LPF of LFE should be left at 120 Hz. This is only IF your receiver allows the two to be set individually. Some do and some don't. If you can't set them individually (which is the case for Pioneer Elite receivers) then you can experiment with it some. If you set the crossover up to 120 Hz and your sub becomes localizeable, then you would want to start lowering it until you can no longer localize your sub. You would probably have to lower it to 100 or 80 Hz if this is the case.

[eyekyu]

i got the sub to -1db, i dont have steady hands haha. then adjusted the gain again while watchin transformers imax scenes. im at about 10oclock position and ran audessey again and it came up woth -7db . it does sound better but i think i wanna try a new amp just to be sure

[sarge1976]

Originally Posted by fireman325

I don't know for sure, but it might be a good idea to re-run Audyssey after you change the phase of your sub.

As far as the crossover goes, it's always been my understanding that you should turn the crossover knob on the sub as high as it will go and use the crossover setting in your receiver. The idea here is that the sub will basically use whichever crossover setting is set lower. An example would be that if your receiver's crossover is set at 80 Hz and the crossover knob on the sub is set at 60 Hz, then your sub will only play up to 60 Hz. The problem this presents is that because the receiver is set at 80 Hz, your regular speakers will start to roll off at 80 Hz as the receiver begins to transition the sound over to the subwoofer, which is only playing from 60 Hz down. This means you will have a 'hole' in the audio between 60 and 80 Hz. Turning the crossover knob on the sub all the way up essentially removes it from the equation and allows everything that has to do with the crossover to be handled in the receiver.

Thanks for the education fireman, I'm going to do what you suggested and see how it goes. What did you mean when you said Pioneer Elite recievers don't have a certain crossover option in an earlier post? I have an SC-27, should I do something different from what you suggested earlier? Thanks again.

[Steve]

Originally Posted by sarge1976

Thanks for the education fireman, I'm going to do what you suggested and see how it goes. What did you mean when you said Pioneer Elite recievers don't have a certain crossover option in an earlier post? I have an SC-27, should I do something different from what you suggested earlier? Thanks again.

When I had an Onkyo receiver the crossover and LPF of LFE could be set independently of each other. With my Pioneer Elite SC-25 there is only one setting for the crossover and it also encompasses the LPF of LFE. This is one area where Pioneer Elite gets some negative criticism.

[sarge1976]

Originally Posted by fireman325

When I had an Onkyo receiver the crossover and LPF of LFE could be set independently of each other. With my Pioneer Elite SC-25 there is only one setting for the crossover and it also encompasses the LPF of LFE. This is one area where Pioneer Elite gets some negative criticism.

Oh, I understand now. I think my Onkyo 805 had that feature as well.

[JBL4645]

Originally Posted by Fors*

+1...I used REW and it did a good job. It takes a little computer know-how to set it up though. Luckily I had another member walk me thru the set-up or I would never had known what I was doing.

That it is a mind boggling device that takes a while to get used to and it does the tick smartly, without spending silly amounts of money.

If I can find spot that is relatively smooth with less nulls then fine the EQ should handle the peaks for an even smoother low end. At present I moved the sofa within 6 feet of the front and it also changes the way the stereo fronts is heard.

If I shift the sofa back by 2 feet I’m in pitiful null spot in relation to where the main sub is located that is used for the LFE.1 only. I placed the LCRS sub bass extension at the back of the room as that is where the best frequency response plays to the listening area sofa.

My room is real pigs-ear to solve and REW makes it easier and faster with locating the SPL db metre in different locations and running the REW frequency sweep over and over while checking each graph for less dips and fewer nulls, nulls just diminish the low end impact.

[JBL4645]

Originally Posted by progers13

This is true of 1 sub in a setup, in which case you would almost always want it to be set at 0. However, in cases of 2 or more subs, phase becomes a bigger issue. When I added my second sub last month, I used the SPL meter to calibrate both individually. But when I turned them both on at the same time and ran test tones, I could clearly hear a void on the right half of my room. I even had to touch my sub to make sure it was firing (it was, but it was cancelling due to phase). This was solved by adjusting the variable phase knob on one of the subs from 0 to 180, and now I have even bass response across the whole room. -Thanks again to db01 (Dennis) for pointing me in the right direction to solve this little mystery I had.

Interestingly enough I was running my second mismatched sub as I have two different subs and while looking at the REW graph noted the few null issues with the JBL 4645 then thought add or splice the Eltax A12-R onto the same signal even thou it only handles LCRS content while the JBL 4645 handles LFE.1.

It mildly filled in on the nulls but wasn’t stratified until I moved the SPL db meter further up-front and ran the sweep again only with the JBL 4645 and noticed the response can’t get any better than it was previously.

If I had smaller 12” JBL subs I’d place them all around the room along the sidewalls and rear wall and the few limited areas around the front and run special hook-up with single EQ thou multiple EQ would be wiser to get each one smoothed out then run the sweep again and use master finalize EQ to address the whole thing.

It’s not really practical it would cost a lot to run it! Also cables everywhere! But the gaol is total smooth frequency response uniformly around the room and even if it is, it will still have few peaks or dips when walking around while listening to (single sine wave tone).

It’s just the same in real life. If you hear an engine on bus its tone will change if you walk around the bus or inside up and down the bus.

But if you can get smooth within the seating area then you’ve done your job, nothing more to do after that expect relax and enjoy a flick on Bluray.

I’ll post a new REW graph of the two subs tomorrow its not as if its late right now, I don’t give hoot about the neighbours, I’m just knackered been up since 6am. 15 hours.

[JBL4645]

A few frequency graphs here shows the sofa placed a few feet back from the front where its been for some time. A few frequency graphs of the sofa being simply shifted forwards shows a different frequency response range.

If I had more or the same sub I could no doubt get it smoother with the sofa placed a few feet back not that I mind being 6 feet from the projection screen. The size of the image looks just that bit bigger.

So being a few feet forwards gives a low end with less fewer nulls the dips a few peaks are more manageable to handle with parametric EQ which is handled by the Eltax A12-R LCRS sub bass extension. Also most action Foley effects are played actively over the LCR and even the odd low end rumble reaches down on the surrounds sometimes down around 25Hz or lower.

Eltax A12-R 7 half feet from sofa


Eltax A12-R 5 half feet from sofa


The LFE.1 handled by the JBL 4645 there’s not much I can do about this its less dip at the from 40Hz to 70Hz most action Foley effect punches tend to be within the 30Hz to 60Hz range sometimes.

JBL 4645 6 feet from sofa


JBL4645 7 half feet from sofa

[kareface]

What range do you crossover at and what microphone are you using for the calibration? What PEQ did you end up using? What resolution are the graphs you have above? What are you doing for bass trapping? You can probably smooth out you FR above 70, but it won't matter if you're crossed over below that.