ULS-15 "knock" or "thwack"

[JackO]

Just got my ULS-15 and on a recent movie (Hellboy II, scene where dude kills his dad.. stopped trying to watch the movie in fear of killing the sub) I get a 'knock' or 'thwack' at the very low end of the bass range. I had the same 'knock' when i used auddessy to set up the system... neither were playing at very high levels at the time (-20 on my Onkyo 876) I've also played Master and Commander, and Batman begins with no issues. So here's where i'm at with settings and room size:

Gain: 12 o'clock
Sub Volume: 12 o'clock

Onkyo 876 with Auddessy settings:
Sub: -9 db
80 hz LFE

Sub's located about 3 feet from a wet bar corner wall, 4 inches of clearance behind in a 4500 cu ft room (irregular shape).

Pete or anyone got any ideas on help?

Thanks,
Jack

[Pete_Hsu]

Hi Jack,

This could simply be a case where the unit is simply being overdriven on this scene. Try this as an experiment: set the volume knob on the subwoofer to ~ 11 o'clock (no more than 1/3 of the way up), set the subwoofer channel level to +0db, turn Audyssey off, and set ULF trim to 50Hz. What are the results on the movie when you do that?

Thanks

Sincerely,

[skool]

I think this is Audyssey overdriving your ULS-15 into excursion after the auto calibration process. If possible, turn the Audyssey process off for your sub, leave it on for everything else. I remembered reading somewhere that depending on room acoustic, occasionally Audyssey adds low end bass boost in order to flatten in-room frequency response. This could be Audyssey's way of compensating for smooth rolled off of sealed subs.

[JackO]

Audessey is definately doing something on this one... I've read the same on it attempting to flatten out the range. It's only happened on 'hellboy 2' and the audessey setup to this point, all other material the sub sounds great.

I did take Pete's advice and removed audessey, turn the ULF trim all the way up (high) and lower volume... It did stop the bottoming out but pretty much killed all the bass produced by the sub in the process. I know his intent is to get me to start 'tweaking' it... I went ahead and moved the ULF trim to 2 O'clock, 5 O'clock sub volume and re-ran audessey, still bottoming out, but Audessey is clearly trying to compensate for the trim change since it went from a -9db change on the sub to a -6.

Can't disable the Multi EQ XT without disabling it all unfortunetly Skool (Onkyo 876), good thought though. Can't live without Audessey given my irregular room dimensions (trust me, it's a mess of a 7.1...) now that i've had a taste.

I'm going to try and re-run audessey today with the full 50hz trim set... I hate lowering the volume on the sub since it affects more than just the low frequency range (though the audessey is effectively doing the same since it's running at -6db).

Any other ideas are appriciated... I've still only encountered this during the Audessey setup and on Hellboy 2 (i've run the first LOTR movie and Dark Knight with no issue since my last post) and love the sub, so if i have to give up Hellboy 2, so be it.

[lanion]

Don't use wireless if you are...sometimes that causes 'knocks' for me.

[JackO]

Originally Posted by lanion

Don't use wireless if you are...sometimes that causes 'knocks' for me.

Thanks... yea, i'm not. I tried it but couldn't find a clean channel... was running 4 wireless components in the room (Xbox 360, DirecTV wireless lan, Wii, and the wireless controllers on the 360) and every channel caught interference (or put it out, actually froze my 360 on channel 2).

I'll probably try the Audyssey with the lowest ULF trim as well... why try and limit the low end when audyssey will just work to compensate anyways...

[Pete_Hsu]

Jack, after lowering the volume knob on the subwoofer, did you bump up the subwoofer channel level to +0db?

You should be able to run Audyssey without the subwoofer turned on right? The auto-eq could be trying to boost some of the deeper bass, which could put extra strain on the subwoofer.

By the way, I have heard that some BluRay tracks have the LFE running up to 10db hot relative to the mains, which also puts extra strain on the subwoofer. You could try lowering the subwoofer channel level on these tracks to see at what point there is no audible distortion from the driver.

[JackO]

I did move the receiver db's up to 0 on the sub and disabled the Audessey. It pretty much lowered the 'hearable' bass from the sub (I could still feel it) and eliminated the 'knock'.

Originally Posted by Pete_Hsu

By the way, I have heard that some BluRay tracks have the LFE running up to 10db hot relative to the mains, which also puts extra strain on the subwoofer. You could try lowering the subwoofer channel level on these tracks to see at what point there is no audible distortion from the driver.

I honestly believe this to be the truth on Hellboy 2. I've run four 'bass heavy' movies (Batman Begins, The Dark Knight, Fellowship of the Ring, and Master and Commander sourced off of Blu-Ray) and haven't encountered the same issue... those movies sound fantastic with the ULS-15 with Audyssey running.

I'm running Audyssey with the ULF trim set to both extremes as I type. I do think it's Hellboy's LFE track running wild (sourced off of DirecTV) as you more-or-less suggested.

[hometheatergeek]

JackO,

I thought I heard this when I first was playing around with the very low test notes (10 Hz) on the Hsu's supplied test disk when the gain was at 12:00. I now run mine at 10:30 gain, ULF at 16 hz, and adjusted the trim in the AVR upwards.

What I have noticed about these subs, since they are so accurate, is they will only play bass notes when called upon. Meaning you can get away with the gain on the sub below 11:00 and when there is bass it will still come alive. Set this way, they can actually make you jump on a movie you haven't heard before. I have not had that problem with Hellboy 2, but I watched the bluray version with my present setup.

I know you don't listen to music that much, but I listen to alot on the weekends and it is always amazing to listen to one song with very little bass and one with alot. I was flipping thru the digital music channels and was floored by the amount of bass in "Who let the dogs out." Not saying I listen to that kind of music but it was amusing.

Hope this helps you get comfortable with you new sub.

[JackO]

Well, all I can tell you is that for every move I make on the ULS-15 itself, Audessey counters (imagine that from room correction software).

Sub Volume: 12 o'Clock
UHF Trim: 16hz
Audessey automatically adjusted sub volume: -6db.

"thwack" on both the Audessey setup and Hellboy 2 via DirecTV.

Sub Volume: 10:30 (on the white line)
UHF Trim: 16hz
Audessey automatically adjusted sub volume: +1db

Same "thwack", but lost just a tad in the sub range during Hellboy 2(by the ear, sorry no spl meter guys)

I tested all the settings with LOTR: Fellowship of the Ring first chapter (standard dvd), all sub settings sound great (last setting lost just a bit).

There's no doubt that Hellboy 2 via DirecTV is absolutely running 'hot' on the LDF...actually running a hot on all channels... watching it at -20 while I normally watch at -8. So I guess my question for Pete is am I in jeopardy of damaging the sub if I continue to run it as is? After five days of fairly heavy use Hellboy 2 is the first source of material to cause the 'thwack' in normal listening, and that includes some pretty heavy bass movies. I love the way it normally sounds and the finish and size of the sub.

[Pete_Hsu]

Hi Jack,

I don't think you are in danger of damaging the subwoofer. It looks like 99% of the time, you are in great shape. If you hear any bad noises on any other soundtracks in the future, then just back down on the master volume level. It's very strange that Audyssey will not let you manually adjust the subwoofer volume level...

[JackO]

Originally Posted by Pete_Hsu

Hi Jack,

I don't think you are in danger of damaging the subwoofer. It looks like 99% of the time, you are in great shape. If you hear any bad noises on any other soundtracks in the future, then just back down on the master volume level. It's very strange that Audyssey will not let you manually adjust the subwoofer volume level...

It will allow me to adjust the subwoofer sound level, but then it's an across the sub-range sacrifice affecting all the sound below 80hz. The sub is no longer sound level matched with the rest of my speakers. Tried to turn down the volume on the sub itself and increasing the volume if the LFE from the AVR, but it re-introduces the issue.

Thanks again Pete (and all), really appricate the the quick board responses. I've really only hit this problem with Hellboy 2 (via DirecTV) and it's not the first time DirecTV's sound output has been less than consistant. Sitting back and listening to the ULS-15 handle my other material is truly an upgrade over my ol Infinity IL-120 or Elan 1200.

[Pete_Hsu]

Thanks Jack, I really appreciate it! Glad that you like the sub

Sincerely,

[wingnut4772]

Originally Posted by lanion

Don't use wireless if you are...sometimes that causes 'knocks' for me.

Ditto - if you don't have a strong signal.

[JackO]

Alright, so it happened again during the opening credits of 'Get Smart' with the doors clamping down. Got it fixed... here's what i ended up doing for anyone else who may have the same issue.

Ran Audyssey with ULF trim at 16hz and 12 o'clock sub volume.
After Audyssey was finished, adjusted the ULF trim to 12 o'clock.

Audyssey was trying to keep the flat line throughout the sub sound, so rather than fight it pre-calibration I just let it try to calibrate it flat, then adjusted the ULF trim to eliminate the 'knock'. This gave me the rolloff I needed on the low-end without affecting the higher end of the sub's db's/equalization settings. Audyssey pushing too hard too low pretty much caused the issues.

So make that 100% of material Pete... I actually couldn't have done this on many subs since they don't have ULF trim. Great feature!

[Pete_Hsu]

Awesome, great idea Jack! That is a great way to do it, well done

Thanks for taking the time to optimize the unit!

Sincerely,

[skool]

Hey JackO, have you ever done a sweep of your room with Audyssey off? You may not need equalizing with your sub. Do you have access to a Radio Shack SPL meter? How about sweeping your sub using the tones on the Hsu cd and analyze the results?

Are your speakers set to SMALL by any chance? Also, like Pete said, is it possible for you to run Audyssey without turning your sub on?

You mention you didn't like the sub sounds without Audyssey. I think this is probably due to the fact the sub isn't calibrated properly without Audyssey. How about rerun Audyssey without the sub on and calibrate your ULS-15 manually using a SPL meter to match your speakers? You can try running the sub 2-3 dB HOT for better dynamic impacts.

[mystro]

Hi skool, which is the most effective SPL meter and cheap one I can get and where? Any recommendation? Thanks

[JackO]

Let me start with now that I got it calibrated to my liking, I couldn't be happier with the ULS-15 or my sound system as a whole.

Originally Posted by skool

Hey JackO, have you ever done a sweep of your room with Audyssey off? You may not need equalizing with your sub. Do you have access to a Radio Shack SPL meter? How about sweeping your sub using the tones on the Hsu cd and analyze the results?

Didn't have an SPL meter.. you could have been right, I may not have needed sub-equilization, but i'm facing a pretty irregular room with 15' ceiling and a wet bar.

Originally Posted by skool

Are your speakers set to SMALL by any chance? Also, like Pete said, is it possible for you to run Audyssey without turning your sub on?

My old denon had a "small" and "large" setting for speakers, but my current Onkyo 876 does not. I was apprehensive to run Audyssey without the sub. Audyssey would possibly try to extend the speakers I do have lower than it should since no sub exists. Additional issues include double bass, and possible equilization/gain issues around 60-80hz since Audyssey's equalizing according to my main speakers (Elan LS650's) that would then be applied to a 15" ULS-15. I can set crossovers and change db's after Audyssey is done, but you can't change equilization without throwing all the Audyssey's equilization out.

Originally Posted by skool

You mention you didn't like the sub sounds without Audyssey. I think this is probably due to the fact the sub isn't calibrated properly without Audyssey. How about rerun Audyssey without the sub on and calibrate your ULS-15 manually using a SPL meter to match your speakers? You can try running the sub 2-3 dB HOT for better dynamic impacts.

I kinda did a similar tweak above. I let Audyssey do it's thing and then adjusted the ULF trim afterwords an let the low end run off more naturally. One of the large problems I was having was if I turned the ULF trim to 50hz before I ran Audyssey, Audyssey would try and compensate by just giving more juice to the low range in an attempt to flatten it out. I was pretty dead set on not adjusting the settings ON the subwoofer after audyssey ran thanks to this statement by Chris at Audyssey on the AVSForum:

Originally Posted by Chris at Audyssey

...I have 2-HSU ULS-15 subs. They are sealed subs. They have an adjustment call Ultra low frequency trim. It is a knob with a 16 to 50hz range...Will changing this setting after calibration make the calibration less effective or ineffective for the sub?

You should not make changes after the calibration as they will change what was measured. Before is OK, but then just re-run the calibration.

I pretty much took this as law, and I shouldn't have.

Audyssey was much more important to main/surround sound speakers than the sub due to the irregular room dimensions, but I did want the sub equilized/volume set/ timed correctly. who doesn't want the whole enchilada when it comes to there sound system? When I posted, I was really looking for a quick fix for the 'knock', and there just simply wasn't one .

[hometheatergeek]

I am so glad you found the perfect setting for YOU. Emphasize YOU.

I don't like what YAPO on the Yamaha does either to subwoofers. Now it's time to sit back and enjoy YOUR movies YOUR way.

[skool]

Originally Posted by mystro

Hi skool, which is the most effective SPL meter and cheap one I can get and where? Any recommendation? Thanks

Most people would just recommend you buying the Radio Shack one. Stop by your local Radio Shack and get the Analog 33-4050 one. Don't spend more for the digital one, analog is all you'll need.

Here's a link if you're not sure.

Originally Posted by JackO

My old denon had a "small" and "large" setting for speakers, but my current Onkyo 876 does not. I was apprehensive to run Audyssey without the sub. Audyssey would possibly try to extend the speakers I do have lower than it should since no sub exists. Additional issues include double bass, and possible equilization/gain issues around 60-80hz since Audyssey's equalizing according to my main speakers (Elan LS650's) that would then be applied to a 15" ULS-15. I can set crossovers and change db's after Audyssey is done, but you can't change equilization without throwing all the Audyssey's equilization out.

I'm really surprise that an above-entry-level receiver with Audyssey do not such capability. Isn't there a way for you to customs set your speakers setting and then let Audyssey do the rest of the calibration such channel level, acoustic compensation, EQing and etc..? My friend Pioneer Elite VSX-91THX has the auto MCACC feature and when we first ran the auto calibration feature, it sets fronts as LARGE. I changed it to SMALL and rerun MCACC in custom mode telling it to keep my speakers' setting. Does Audyssey not have this capability? Double bass is bad unless you can adjust the phase correctly and I guess Audyssey should be able to compensate for this. Also, with front speakers as LARGE, you're missing quite a bit of low bass content that could've been redirected to your ULS-15 for further dynamic impacts. You'll be surprise how much bass content there is in the front channels of 5/7.1 soundtrack.

Originally Posted by JackO

I kinda did a similar tweak above. I let Audyssey do it's thing and then adjusted the ULF trim afterwords an let the low end run off more naturally. One of the large problems I was having was if I turned the ULF trim to 50hz before I ran Audyssey, Audyssey would try and compensate by just giving more juice to the low range in an attempt to flatten it out. I was pretty dead set on not adjusting the settings ON the subwoofer after audyssey ran thanks to this statement by Chris at Audyssey on the AVSForum:

Unless you know exactly the frequency response of your room, I would not mess with the ULF trim. If I am not mistaken, this is giving you the ability to change where the sub start rolling off its frequency response. Without measurement, it'll be hard for you to know where the frequency response starts rolling off in your room. Thus, since your room is quite large, there won't be much room gain and thus I would leave it at 16 Hz and let the sub roll off naturally.