i'm on the hunt - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 6 Old 06-24-13, 11:50 PM Thread Starter
Join Date: May 2013
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i'm on the hunt

let's face it..

adjusting the equalizer with a calibrated microphone gives enough of a difference to be a bit wowed turning the equalizer on and off.


when grabbing an impulse response and loading it into a convolution plugin for digital correction .. well when turning the convolver on and off doesn't provide as much wow as the equalizer, something is clearly wrong with that situation.

it is kinda hard to do it wrong i'm thinking..
set up the mic where it was used to calibrate the equalizer
run a measurement
export the impulse response
load the impulse response inside a WAV editor to trim the beginning and any excess tail off the file
flip the wave and export
load file into convolution engine
stuck messing around with wet & dry statements when truthfully the signal should be convoluted as one whole

when doing the equalizer leaves a plus or minus of five decibels.. one would think the digital correction would fix the last few decibels.
what i've found is a very dull result that sounds heavily washed out.

i'm wondering (because i cannot afford to try) .. are all of them sounding washed out?
do any of them really flip a wig of invisibility with silenced darkness & rich dynamic audio that seems to be like a built shelf holding audio details in it like a carton .. and from there the audio can float out like a ghost?

it sounds like the listening position fills with a bright washed out sound that doesnt seem to stun the existance of the room much.

i want to know if it is better (or different) out there.. or do we need to keep waiting for an increase in bitdepth .. or even keep waiting for the convolution plugins to see their compilers extended ..??
what is it going to take?


a brief short on how the digital room correction works..
you need to zoom in and view with your brain,
as the cone moves out to push on the air.. the gelatin of the room begins to wiggle.. the cone moves inwards and the puff of air detaches ... but since the gelatin of the air can wiggle.. you dont need to rely on the detachment floating across the room.
instead it can slap on the walls as if an instant virtual speaker in contact with anything within the wiggles reach.

the accumulation of sound, whether directly from the speaker or from a bunch of those virtual speakers adding up to create room noise... well that cause peaks and dips in the response the microphone records.

the peaks require the speaker cone to move outwards less.. exactly like an equalizer.
there are two choices:
1. reduce amplitude
2. change the phase enough degrees until the decibel is the right level.

reductions in amplitude to cure room peaks 101..
if your speakers are flat outside with no wind
then suddenly your going to be straining to hear whatever portion of the frequency response that has been reduced, simply because it is lower in volume and you are relying on the room to keep the portion 'amplified' or 'boosted' because of the peaks.
with that said, you start to really destroy localization from the speaker because you begin to listen to the entire room .. something that sounds thrilling, yet highly nuisance because it is only a portion of the frequency response.

i knew something was terribly wrong when i wanted to sit in the warm candle lit heat of the speakers but the sound wasn't oriented correctly to allow me to do such a thing.

i want to hear the speakers, but every movement seems to smear the audio, and i'm not totally opposed to the smearing .. but i hate it when it loses amperage, dynamic range, detail & clarity.
not only does it sound winded.. but it starts to sound like the frequency response in the upper portions are brighter .. it sounds like a mouth that has rather numb lips & tired or ache-y tongue.

there is a magnitude more effort present from the speakers before i touch them.. thus i feel like i've taken steps in an opposite direction or something needs to get turned up more to fulfill a sense of completion.

**edit again**

there's two ways to do it:
1. output the wet portion as everything added to cancel out something
2. don't output anything additional because the portions were already subtracted before the audio went to the speaker cone (i think this is the one i want)

...yes, if your room echos you can pour out an echo that spills into the room that causes the echo to cancel itself out - but listening to nearfield speakers that are doing this sound rubbish...

there is also the option to do a mixture between the two.

Last edited by siptu; 06-25-13 at 01:51 AM.
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post #2 of 6 Old 06-26-13, 07:31 AM
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Re: i'm on the hunt

- Here's a testimonial supporting drc ( Digital Room Correction ) that you may want to read .

- You might also want to follow all the postings of Mitchco ( or Mojave for that matter ) at this forum and others ( such as jRivers ) to better grasp the how-to's of successful dcr implementation .

- OTOH, if using outboard EQ works best for you ( within your particular circumstances ) , then "have at it " .

Last edited by EarlK; 06-26-13 at 11:45 AM.
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post #3 of 6 Old 06-27-13, 03:55 PM
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Re: i'm on the hunt

It sounds like you are exporting the impulse response of the measurement to your convolver. That would, in effect, be convolving the room with itself, so you would get the room's response multiplied by the room's response. Ordinarily it is the impulse response of the filters that is exported to the convolver, using the convolver to apply the desired filter response.
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post #4 of 6 Old 06-28-13, 12:59 PM Thread Starter
Join Date: May 2013
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Re: i'm on the hunt

i do invert the impulse response before exporting it.
one of the very first things i learned was if i didn't.. the echo was much worse.

what i had been faced with.. well its a bit of a list & i need to start somewhere.

1. confused about why i was hearing an echo at all since my thought was the echo of the room was shaved from the output signal.

2. the echo i did hear wasn't blending with anything to give it a sense of fitting function.

3. there was details & clarity after doing the equalizer that were lost after applying the convolution.

4. it sounded like there was a lot of emphasis to draw (pull) the sound from the speaker until it was to the listening position, rather than fix the decibel fluctuations at the speaker (or the listening position).

5. the sound from the speaker (since one of them is only about 5ft away) sounds brighter as if more treble all the way down to the vocal range.

6. the sound from the speaker loses reason to listen to it directly because the sound isn't solid enough, but the floating soundstage in the middle is too weak & missing detail.. as if to say airy and a weaker attempt than what was coming directly from the speakers.
sure.. i've messed with plugins to eventually get the middle portion louder, but it wasn't any more detailed in comparison to what the result was after doing the equalizer.

i believe there is a time and a place for the soundstage centered, but i do believe the time delay is meant to do the same thing.. that is to say, i'm appreciative something is happening.. but i'm looking for something that i can benefit from (rather than feeling like something is sucking the benefits from me).

as of most recently, i went back to the free SIR convolution plugin.
i was playing around with the envelope, predelay, attack.. but i really didn't hit any mark that was alleviating.
but then i started messing with the 'stretch' feature and the first thing i noticed was the strong difference rather than a tiny one.
i ended up settling on looking at the measurement of each speaker and noting the U seconds (the ones that come before millisecond)
instead of putting it right on the middle, i put it on one just before.. because my room's size is supposed to have a resonance around 45 but three of the walls at the top have a 45 degree baffle connecting the wall to the ceiling.
(the one without is the wall behind me, also where the doorway is)

what that did was make the sound of the echo go away, but it still hasn't brought the details back from before doing any convolution at all.

i can only imagine maybe the room echo is down enough that the sound is less loud (or non-existant) in the other rooms next to the listening room.
(i cant tell because the hallway will echo anything, and above me is another apartment.. with the other walls being dirt behind 'em .. as the final wall has a door opening that cant be shut)

something else that seemed to help is adjusting the predelay as far as it would go before the first spike shown in the impulse response.. in my situation it is 1ms because the first spike happens around 1.5ms

however, the manual says the 'stretch' feature is simply oversampling or undersampling.

i thought the impulse response was a measured line of all the peaks & dips, as well as what degree of room echo.. then all of it gets smashed into a chirp by system of fundamental instructions that are read, as if compressed and then decompressed.

are people like me that do the equalizer first, then look for some digital room correction on top of that, walking in a bad direction?

it makes me confused about an impulse response working with 'filters' when the impulse response is meant to be the filter itself.

where can i read up about adding filters to an impulse response, and also.. do we need to invert the impulse response before it goes into the convolver?

i feel locked out of the digital correction part, and i jst asked for the last opportunity of hope before feeling like the entire industry needs an upgrade to reveal new options.

the DRC (digital room correction) doesn't work because it refuses to read my microphone's calibration file .. as if the format is wrong after changing the file format to .txt
it looks easy if you are doing with with .bat files... but those files are 44.1khz only.
all the graphical user interface options are broken.

the room correction options are almost all too expensive, especially considering this infant time where 24bit recordings is the typical maximum for most soundcards.
the movie might be 24bit audio, but the room's echo is higher.
(mine are still stuck in 16bit)

as i said above, there are two ways to do it..
i think there should be an option for either one.
sometimes it's personal taste, other times it might be speaker specific (because i figure they will inevitably lean to preferring one over the other).
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post #5 of 6 Old 06-30-13, 05:09 PM
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Re: i'm on the hunt

Simply inverting the impulse response does not work, that is why DRC was written. Wikipedia has a brief explanation of why, and useful links to further discussion (though the DRC Wiki seems to have gone AWOL, unfortunately).
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post #6 of 6 Old 06-30-13, 07:19 PM Thread Starter
Join Date: May 2013
Posts: 13
Re: i'm on the hunt

i managed to figure out how the filters work without reading anything.
the frequency response did sound flatter.
i felt more accomplished exporting the filters impulse response than the measurement impulse response, and hi.. i even managed to be satisfied with the normalized sample value the first time.

second thing i did was go back to get me some distance delay because my speakers are uneven.
(had some before with the THX studio, but it doesn't install on windows 7)

third thing i did was play with a VST plugin i've been rather impressed with but didn't know how to correctly utilize it.
the name of the plugin is 'full phase'

what to say about it?
it uses the two speakers to change the phase.
i'm guessing you've got two choices, use it to adjust the phase of the room for two seperate speakers in the room ... or use it to build up a phantom center.

i think i'd like to suggest start with the slider all the way to left or right... then adjust the up down slider until it sounds something decibel even.. then go back to the left|right slider to adjust the balance.
i don't know if it does a bit of good for speakers that are all the same even distance.. but my computer monitor seems to speak more than the speakers in the corners.
(not that i am aiming for the sound.. but inevitably a solid wall of sound is desireable , if only ignoring the entire room as a potential aquarium of sound)

it seems like the character slider makes the phantom image louder with a bit more amplitude.
(then feel free to move the up|down slider a notch for any final leveling)

i think it is worth saying something about not wasting time with the measurement's impulse response in a convolver, because i've done exactly that.

i can be picky .. but i also cherish being easily pleased.. when i say i am still not satisfied.

i'm at a point where i know multiple speakers only ruins a stereo effect, but there is enough missing that i feel i want 'em.
it's because my sides aren't getting anything.
all of it floats from speaker to center, back and forth.. a little bit of behind.. but nothing on the sides.

i want to use the sides as a 'buddy'

Last edited by siptu; 06-30-13 at 07:42 PM.
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