Maybe I'm nuts here but isn't a decoralation filter pretty easy to design in the analogue domain. Isn't it nothing more than a lattice-ladder filter, as in the same filters we use for creating signal delay? If I'm thinking right this could be achieved with 2 opamps and a small handful of resistors and capacitors mounted on strip board (i.e. a very simple circuit).
Simple delay was not my idea and I don't think that the filter that you describe would create a decorrelated signal. It would still be highly correlated but at a delayed time.
You need a back of these filters, all with different delays and random levels. This will decorrelate the signal. Easily done digitally, but a lot of analog circuitry.
You need a back of these filters, all with different delays and random levels. This will decorrelate the signal. Easily done digitally, but a lot of analog circuitry.
noah katz said:
Yes, of course, large rooms have it and small rooms don't. But how do you get this in a small room?
I hypothesized an electronic simulation of a bank of added room modes. When I did this I found that the LF sound field smoothed out almost like that at HF. Then I found that this filter was called a decorrelation filter - also know as a reverberator. But We don't want to do this at HFs, just the LFs.
room lf
Interesting reading.. thanx all..
My experience in my rather largish room 25' x 30' rectangle + 15' x 15' open to kitchen 2 story, maybe 15,000 ft^3 SCREAMS don';t put ANY subs in the corner... else HUGE standing 32 hz wave at the ceiling/floor peak ~17.5 feet that dominates the bass response.
After years of moving first one sub from one corner to another (either room boom or total suckout, depending on the corner) my current setup has 2 12" sonotubes ~1/2 way along shorter walls 2 - 3 ' out, and yields smooth extended bass to below audible freqs. at floor rattling (and drywall joint splitting) levels for both audio and movie HT listening at a large arc maybe 15' across 15' back at the viewing/listening position.
Corner loading in this setup is just plain stupid.
Mathematical calculations may be good for guidance, but with all the assumptions/deletions re: boundary effects or not, trial and error seems to be the best approach. I've tried most of the different setup motifs, and this current setup is by far the best.
Not all of us are limited to small rooms with low ceilings. I'm driving 7.1 surround with 140 wpc on the mains and surrounds, and 300 w/sub for the 2 sonotubes. Not for the faint of heart. Definitely envelopes one into the movie...
I'm not sure how much better this could get, but I'm open to suggestions (short of rebuilding the room w/o windows, drywall, etc.
John L.
Interesting reading.. thanx all..
My experience in my rather largish room 25' x 30' rectangle + 15' x 15' open to kitchen 2 story, maybe 15,000 ft^3 SCREAMS don';t put ANY subs in the corner... else HUGE standing 32 hz wave at the ceiling/floor peak ~17.5 feet that dominates the bass response.
After years of moving first one sub from one corner to another (either room boom or total suckout, depending on the corner) my current setup has 2 12" sonotubes ~1/2 way along shorter walls 2 - 3 ' out, and yields smooth extended bass to below audible freqs. at floor rattling (and drywall joint splitting) levels for both audio and movie HT listening at a large arc maybe 15' across 15' back at the viewing/listening position.
Corner loading in this setup is just plain stupid.
Mathematical calculations may be good for guidance, but with all the assumptions/deletions re: boundary effects or not, trial and error seems to be the best approach. I've tried most of the different setup motifs, and this current setup is by far the best.
Not all of us are limited to small rooms with low ceilings. I'm driving 7.1 surround with 140 wpc on the mains and surrounds, and 300 w/sub for the 2 sonotubes. Not for the faint of heart. Definitely envelopes one into the movie...
I'm not sure how much better this could get, but I'm open to suggestions (short of rebuilding the room w/o windows, drywall, etc.
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John L.
Like I said, we know a guy who supplies the furniture mills and he gives us great pricing on wood. There is a 6' tall stack of 3/4" MDF at the shop now. We get anything from 1/4" to 1 1/4". We are a car audio shop and build a lot of sub enclosures for our customers and other shops.
Ultimate goal is to get a Shopbot.
Ultimate goal is to get a Shopbot.
John_E_Janowitz said:
pedroskova said:
Excuse me, but that is a lot of a difference!
Markus and aubergine, that wasn't meant to be rude. I'm a scientist, too, but most people here are hobbyists and that may lead them to take such statements from a scientist with acoustic expertise like gedlee for granted without thinking about it.
I have no problems with the "high gain" of pro-gear but a lot with the sold "aura" of some highly prized consumer gear
It is "professional" to have a high amplification at an early stage in the signal path, that's an old rule in communications engineering!My 8024 runs between the CD player and my Sony AV Receiver with no problems. But one time I will change the Sony "consumer" receiver with its "unprofessional" unbalanced connections aganist this for example with professional balanced connections:
http://www.d-mpro.com/users/folder.asp?FolderID=4214&CatID=17&SubCatID=165
An externally hosted image should be here but it was not working when we last tested it.
Corner subs...
Glad it works for you... doesn't work in my room.
Many other listeners agree with this. Changing the phase, changing the sub, putting the sub in the listening location and mapping the room by ear or meter, all yield excessive modal sound vs. mid-wall side loading at the preferred listening locations. So generalizations about stimulating the maximum # of modes don't always work.
John L.
gedlee said:
Glad it works for you... doesn't work in my room.
Many other listeners agree with this. Changing the phase, changing the sub, putting the sub in the listening location and mapping the room by ear or meter, all yield excessive modal sound vs. mid-wall side loading at the preferred listening locations. So generalizations about stimulating the maximum # of modes don't always work.
John L.
Dr Geddes,
did i understand this correctly, that you process your bass with a decorrelation reverb to smooth the modal response? What is the advantage of this compared to equalizing? And how do you find the correct reverb settings?
This sounds really interesting, as i never have heard such an idea before.
did i understand this correctly, that you process your bass with a decorrelation reverb to smooth the modal response? What is the advantage of this compared to equalizing? And how do you find the correct reverb settings?
This sounds really interesting, as i never have heard such an idea before.
noah katz said:
But the long reverberation time at LF is exactly what I want - so long as it is broad band. The problem in a small room is a long decay time at precise frequencies - the modes. What a lot of people don't realize is that a tone in a room does not decay at its driven frequency, but at the frequency of the modes it excites. Example: modes at 30 Hz and 40 Hz and a tone at 35 Hz. When the tone is turned off the decay is at 30 Hz and 40 Hz NOT at 35 Hz. If the tone only excited the 30 Hz mode then it would decay at 30 Hz not 35 Hz. Basically this effect detunes the instrument. The more modes that are being excited by a single tone the closer the decay will be to the original.
If there were a lot of modes then the long decay (reverberation) would be a good thing as it would reinforce the perception of the bass (time versus intensity).
MaVo said:
I don't do that now, I hypothesized that this would improve the bass. When I get multiple subs working right however, I have no complaints with the bass (and neither does anyone else) so I haven't gone as far as to actually test this hypothesis. In a very real sense adding subs is like adding modes. The sub IS a mode, which is why I suggest tuning them all to different frequencies. I do that in my room. Identical subs in symmetrical locations is strongly sub-optimal IMO. Differently tuned subs in random locations has always worked for me.
And please can we move this discussion somewhere else.
Fosti said:
Excuse me, but that is a lot of a difference!
Markus and aubergine, that wasn't meant to be rude. I'm a scientist, too, but most people here are hobbyists and that may lead them to take such statements from a scientist with acoustic expertise like gedlee for granted without thinking about it.
I have no problems with the "high gain" of pro-gear but a lot with the sold "aura" of some highly prized consumer gear
My 8024 runs between the CD player and my Sony AV Receiver with no problems. But one time I will change the Sony "consumer" receiver with its "unprofessional" unbalanced connections aganist this for example with professional balanced connections:
http://www.d-mpro.com/users/folder.asp?FolderID=4214&CatID=17&SubCatID=165
An externally hosted image should be here but it was not working when we last tested it.
From this and an earlier post, I get the impression that you are an engineer, or at least, attempting to pass yourself off as one. I happen not to consider engineers and scientists the same thing, and I can say that, the sentiment here at Purdue, a huge engineering school is that, Engineers consider themselves scientists, and those doing the scientific research used by the engineers consider them engineers, i.e. those who take the scientific findings and apply it. That is, of course, a pretty big blanket statement, and both fields will often have their dividing lines blurred, but I think its important to recognize the difference in training and work style between the two groups. Anyway, I'm curious, what is it you do for a living exactly, what is your education in, and did I understand you correctly saying that you have the German doctorate of engineering? What is this specifically in, what area of engineering, and what was your dissertation research on? One reason why I don't take Dr. Geddes words lightly is that I did my homework and read as many of his published works as I could, looked up some of his patents, and have read most of this white papers and web published work.
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