Impulse measurements

[Drudge]

Hello,I'd like some opinions on these impulse responses are they acceptable.They are LCR and surrounds each is measured with the sub included.

left


center


right


left surround


right surround

[JohnM]

They look like good measurements, changing to dB axis will let you see where the noise floor is. Couple of large-ish early reflections in the Centre trace, may want to see if those could be tracked down and tamed. Left and Right look quite clean.

[Drudge]

Do you mean using these measurements?I think those reflections are do to a ceiling fan(off of course).Are those reflections to high in level?
LEFT


CENTER


RIGHT


LEFT SURROUND


RIGHT SURROUND

Thanks JohnM,by the way I love your software it has really helped me create a better audio experience

[JohnM]

All looks good. Re the reflections on the centre channel, might want to check whether an absorption panel (or a thick rug of a folded-up duvet) on the floor between you and the centre channel has an effect on the reflections and the frequency response.

[Drudge]

Thanks for the suggestion JohnM.

Does my noise floor coincide to the dB levels listed to the right of each of the check marked boxes for each measurement?For example(left/sub -75.5dBFS)

Also do my RT60 times seem to low?I see that for home theater the ideal is around 300/400ms and a studio control room 250ms a majority of mine are below 200ms.Could that mean that I am over absorbing in the mid to high bands or is it related to the small size of the room(15x11.2x8)?

Thank you for your much needed insight. I know your a busy man.




All impulses
Attachment 9734

1/3 octave rt60
Attachment 9735

1/1 octave rt60
Attachment 9736

[JohnM]

Those attachments all come up as "invalid" for me, sorry. The noise floor is the approximate level the response flattens out at, it is often easier to see it from the response before the peak. It is around -70dB for your plots, which indicates good measurement quality. The RT60 values you mentioned in your post would be quite low, but that is not necessarily a bad thing in smaller rooms. Is the room heavily treated acoustically? For in-depth discussion of room acoustics and acoustic treatments visit the Home Audio Acoustics section of the forum.

[Drudge]

Sorry about that I don't know what happened there.In case your still interested I've reposted the RT60 measurements below.

As far as the room being heavily damped I have two 4" 2x4 ATS panels on each side wall at 1st reflection points Auralex versatiles(pseudo bass traps because their foam)in all 4 corners from ceiling to 1ft from the floor then the front wall has more versatiles which cover an area about the size of 2 1/2 2x4 panels.From there I have two 2x4x4" bass traps in each front corner standing on the floor and a medium weight curtain covering the front wall.I also have the same curtains on the back and side walls because there is a window on the left side and at the rear left so for the sake of symmetry I put a curtain on the right side as well.

I figured the room was maybe medium damped.

I know I need more bass trapping around 100Hz and below but due to my economic/job situation that's all on hold for the time being so I'm making do with what I have.


RT 60's

[JohnM]

Quite a lot of absorption in the room, but for HT surround that can work well, relying mainly on the soundtrack to provide the acoustics not the room. If it sounds good then always a good idea to devote more time to enjoying it

[Drudge]

Yeah,since my Lexicon MC-1 processor uses ambiance extraction and recreation modes for creating a realistic space the combination seems to work quite well.Lexicon also recommends a more heavily treated room in their theory and design manual for that reason.

Other than the low frequency ringing below 100Hz the room does sound pretty good to me but I don't know what(technically)sounds or measures well so I like any input I can get.

Thank you especially for your input and insight JohnM it is definitely a pleasure hearing it from the man himself.

[brucek]

The lower meaningful limit of RT60 is about 200Hz. Below that you should rely on waterfall or decay plots.

brucek

[Drudge]

Thanks for the reminder brucek I had forgot about those measurements not having accurate readings below 200Hz

As you can see my waterfalls show significant ringing below 80Hz and to big nulls as well, but my listening position and the sub's are pretty much the best were they are right now and there is a open doorway as well.Otherwise I have to make sacrifices in other areas of the setup for the other speakers.


Sub with 3 filters



Left and sub

[brucek]

Actually, it looks pretty good. You might consider that some of that signal you have condemned as ringing may be low level noise not associated with your signal. i.e. furnace, air con, refrigerator, outside cars, etc.... Use the spectrum analyzer and examine the lower octaves for any outside noise (see here for set up).

brucek

[Drudge]

Thanks for the positive feedback brucek it's much appreciated.

Funny you mention low level noise I happen to live near a main highway(US-1) and a railway line and on the RTA of the DEQ2496 I get a lot of 40Hz and below noise when a train rolls by.I did take the measurements fairly late in the evening when I used REW and I made sure all the house hold noise makers were minimized and the A/C was turned off.I also took measurements when I thought no trains were passing but it is hard to hear them from inside so one may have snook by.

I'll have to use the spectrum analyzer on REW to see more in detail.I'll just have to borrow a notebook computer again.

I think you may have hit the nail on the head though. Thanks again

[brucek]

I think you may have hit the nail on the head though

Maybe, maybe not, but an indicator to me is when I see a very nice drop in ringing as you have (evidenced by wide spacing between slices), and this continues until about 50-55dB, and then you have these tunnel tails coming out straight at you and actually rising in level (as shown in the purple waterfall). What else could cause an increase in the level as time passes other than outside influence noise). But I've been wrong before.



brucek

[Drudge]

Just so you have a better picture of whats happening I've posted the other measurements that I saved.


Two of the measurements seem to show the same thing but the other 2 are a little bit harder for me to tell if it is just noise.

Well I'm guessing that if all the waterfalls are not showing the same exact pattern that it would have to be something random(meaning noise).

Can a static room change it's reverberation times radically from measurement to measurement without some noticeable pattern if it's not noise?


Center/sub


Right/sub


Left surround/sub


Right surround/sub

[brucek]

Can a static room change it's reverberation times radically from measurement to measurement without some noticeable pattern if it's not noise?

No, not if you measure the same speaker. The waterfall should be the same each measure. If the noise was consistent though, the measure would also result in the same display.

The telltale is that some of your tails rise in level over time. A ringing signal would normally fade into the floor over time. Yours aren't doing that. That's why I feel there may be low level noise mixing in with the normal signal ringing, causing your room to look worse than it actually is...

brucek

[Drudge]

I learn something new everyday!That's why I like these types of forums.

Thanks again for your help.