Regarding room-speaker EQ -- 50 years ago, I started doing room and speaker measurements... following D. and C. Davis work and Gen Radio and B&K. I started with sine wave and then swept sines because that was easily available. Eventually, I got hold of a GR-1558 octave band noise analyzer. That helped a lot to get a quick view and it was portable - making it easier to see effects in different locations. Eventually, I wondered why not automate this GR thing so it switches to each filter in sequence fast enough to look like it was in 'real time' Thus was born the RTA concept. My EE Tech friend and I built 2 of these RTA which used my scope as readout. We had so much fun with it, that we decided to see if others wanted to build it.... the first RTA was published in Popular Electronics magazine as a DIY project, in 1977. Within a year Japan inc was putting the RTA as display in everything using LED bar graph.... and the rest is history. BTW - that first RTA was 1/2 octave RTA.
between now and then, I have used or tried everything made almost.... software and hardware (DSP etal). I bought the first s/n 001 MLSSA from DRA labs. and more analysis HW/SW since then. This is what I learned as a bottom line, simple answere without the details --->
You can EQ for flat if you are in the Very far reverberant field or if you are in the very Near field. It doesnt work for in-between situations. Unfortunately, a typical listening position of a typical house listening room size is in between. So, the only thing to do at home is to listen near field and then the EQ will flatten the speaker response that you predominately hear.
I would prefer to just get a flat speaker and listen near field. Less HW to deal with in the signal path.
![eqp-gr1558a_lg[1].jpg](https://www.diyaudio.com/community/data/attachments/622/622713-a881824366f22c26aade54cafb66b20f.jpg?hash=qIGCQ2byLC "eqp-gr1558a_lg[1].jpg")
My inspiration for the first RTA.
THx-RNMarsh
between now and then, I have used or tried everything made almost.... software and hardware (DSP etal). I bought the first s/n 001 MLSSA from DRA labs. and more analysis HW/SW since then. This is what I learned as a bottom line, simple answere without the details --->
You can EQ for flat if you are in the Very far reverberant field or if you are in the very Near field. It doesnt work for in-between situations. Unfortunately, a typical listening position of a typical house listening room size is in between. So, the only thing to do at home is to listen near field and then the EQ will flatten the speaker response that you predominately hear.
I would prefer to just get a flat speaker and listen near field. Less HW to deal with in the signal path.
My inspiration for the first RTA.
THx-RNMarsh
Last edited:
And/or absorb early reflections and diffuse late reflections.
But, resonances in a speaker within its passband are problematic, no nice way of managing them beyond picking a better part.
But, resonances in a speaker within its passband are problematic, no nice way of managing them beyond picking a better part.
🙂 😎
yes. Absorbing early reflections has the affect of extending the near-field listening distance. OR, you can use more directional speakers (minimal early reflections) and not have to deal with the room at all.
Actually, you still have floor reflections to absorb.... easily dealt with a thick rug.
-RM
Last edited:
info dump
As an info dumper, that is sweet!
But with so many 'browsers' (non-clickers; you know the type!), I'd:
Sy 2012
"Very well, but some quibbles: minimum phase can apply to nonlinear systems as well. The only requirement is that the phase be the derivative of the amplitude response wrt to frequency.
And single valued functions indeed contain no loops, but if (for example) you have a 2d function unwinding in a 3d space, you can inadvertently have multiple values which are not loops in the 2d representation.
Rooms have 3 dimensions (assuming the room size is time invariant!), the signal applied to them has one dimension plus time. So, no minimum phase (there's delays from reflections) and multiply valued (amplitude varies over space as well as time).
"
Gedlee 2012
"Since the concept of "Minimum phase" (MP) comes from "linear systems theory" it is dangerous to try and apply it to a nonlinear system.
It may appear to be MP at one level and not at another one - so is it or is it not MP? It cannot be defined.
Also MP is a one dimensional concept and has no multidimensional meaning. A room can be MP from a source to one point and not be to a different point - again it cannot be defined
"
Tom Danley 2012
"Hi gpapag, sy, all
When you move from circuits to acoustics, you enter a new domain where “it depends”.
Take cone resonance, that is a resonant system between the motor and radiator in the equivalent circuit. Lets say the response curve looks nice up to say 3KHz where it mounds to a peak of say +10dB over the average level.
You can use a steep or brickwall crossover or eq the response and to first order, one has “fixes” the problem of the excess gain from the mechanical resonance and it’s fixed in magnitude and phase.
On the other hand, that mechanical gain is still present and although the response can be flattened, you cannot get rid of the magnification of the motors natural distortion at sub-multiples of the resonant peak. For example, that +10dB gain at 3KHz, will magnify the 3rd harmonic at 1KHz by +10dB also as well as harmonics at other lower frequencies.
In a room, you usually have a mixture of minimum and non minimum phase conditions. The old rule of thumb was only cut peaks and the logic was the following. When you have a deep notch in the response, you have a “cancelation notch” which is (in a room) usually caused by the direct sound combing with a delayed version of the same signal. If you boost the notch, you are adding energy to the source and the canceling signal BOTH, a non-minimum phase condition.
If you measure speakers, you may have seen a notch in the upper bass, a cancelation notch resulting from the direct path signal mixing with the floor bounce signal, the lowest notch frequency, is where the path length difference is 180 degrees.
You can’t add enough boost at that frequency to fix it and any you add also applies a phase correct which isn’t appropriate. EQ is a double edged sword.
Best
Tom Danley
"
Wavebourn 2012
"George, actually it is good to EQ in the range of mid band, but you should EQ only what does not depend on microphone position. What depends on microphone position is not audible like distortions of frequency response, it is audible like ambiance. It belongs to the room, to the sound in the room. In order to deal with this "room sound" there are 2 major ways: either directional speakers, or dipoles.
The former increases ratio between pressures of reproduced and early reflected sounds, even though the ratios between direct and reflected energies integrated is still the same. But anyway reproduced reverberation sounds from the speakers, and when it is heard reflected from walls it sounds like reverberation of a big hall bouncing inside of smaller room, quite artificial.
Dipoles better blend this 2 reverberations so it is harder to localize that reflections of reproduced reverberation from walls around you in the listening room. That's why dipoles sound more "natural" in the rooms with less sound absorption. That does not mean they reproduce better, that means they in such rooms fool imagination better.
Moving the microphone across the listening positions, both horizontally and vertically, you can find what to EQ, no matter on which frequency. Both uneven response of speakers on middle frequencies and results of rectangularity of the room on low frequencies.
However, it is better when before application of EQ all high Q resonances were properly minimized mechanically. Why? Because as I said before, even when you EQ frequency response you can't make decays shorter and they will be audible.
And second, thanks to Tom Danley for the reminder, resonating media are non-linear, so you can't EQ what happens after EQ. Wavebourn
"
Cheers,
Jeff
As an info dumper, that is sweet!
But with so many 'browsers' (non-clickers; you know the type!), I'd:
Sy 2012
"Very well, but some quibbles: minimum phase can apply to nonlinear systems as well. The only requirement is that the phase be the derivative of the amplitude response wrt to frequency.
And single valued functions indeed contain no loops, but if (for example) you have a 2d function unwinding in a 3d space, you can inadvertently have multiple values which are not loops in the 2d representation.
Rooms have 3 dimensions (assuming the room size is time invariant!), the signal applied to them has one dimension plus time. So, no minimum phase (there's delays from reflections) and multiply valued (amplitude varies over space as well as time).
"
Gedlee 2012
"Since the concept of "Minimum phase" (MP) comes from "linear systems theory" it is dangerous to try and apply it to a nonlinear system.
It may appear to be MP at one level and not at another one - so is it or is it not MP? It cannot be defined.
Also MP is a one dimensional concept and has no multidimensional meaning. A room can be MP from a source to one point and not be to a different point - again it cannot be defined
"
Tom Danley 2012
"Hi gpapag, sy, all
When you move from circuits to acoustics, you enter a new domain where “it depends”.
Take cone resonance, that is a resonant system between the motor and radiator in the equivalent circuit. Lets say the response curve looks nice up to say 3KHz where it mounds to a peak of say +10dB over the average level.
You can use a steep or brickwall crossover or eq the response and to first order, one has “fixes” the problem of the excess gain from the mechanical resonance and it’s fixed in magnitude and phase.
On the other hand, that mechanical gain is still present and although the response can be flattened, you cannot get rid of the magnification of the motors natural distortion at sub-multiples of the resonant peak. For example, that +10dB gain at 3KHz, will magnify the 3rd harmonic at 1KHz by +10dB also as well as harmonics at other lower frequencies.
In a room, you usually have a mixture of minimum and non minimum phase conditions. The old rule of thumb was only cut peaks and the logic was the following. When you have a deep notch in the response, you have a “cancelation notch” which is (in a room) usually caused by the direct sound combing with a delayed version of the same signal. If you boost the notch, you are adding energy to the source and the canceling signal BOTH, a non-minimum phase condition.
If you measure speakers, you may have seen a notch in the upper bass, a cancelation notch resulting from the direct path signal mixing with the floor bounce signal, the lowest notch frequency, is where the path length difference is 180 degrees.
You can’t add enough boost at that frequency to fix it and any you add also applies a phase correct which isn’t appropriate. EQ is a double edged sword.
Best
Tom Danley
"
Wavebourn 2012
"George, actually it is good to EQ in the range of mid band, but you should EQ only what does not depend on microphone position. What depends on microphone position is not audible like distortions of frequency response, it is audible like ambiance. It belongs to the room, to the sound in the room. In order to deal with this "room sound" there are 2 major ways: either directional speakers, or dipoles.
The former increases ratio between pressures of reproduced and early reflected sounds, even though the ratios between direct and reflected energies integrated is still the same. But anyway reproduced reverberation sounds from the speakers, and when it is heard reflected from walls it sounds like reverberation of a big hall bouncing inside of smaller room, quite artificial.
Dipoles better blend this 2 reverberations so it is harder to localize that reflections of reproduced reverberation from walls around you in the listening room. That's why dipoles sound more "natural" in the rooms with less sound absorption. That does not mean they reproduce better, that means they in such rooms fool imagination better.
Moving the microphone across the listening positions, both horizontally and vertically, you can find what to EQ, no matter on which frequency. Both uneven response of speakers on middle frequencies and results of rectangularity of the room on low frequencies.
However, it is better when before application of EQ all high Q resonances were properly minimized mechanically. Why? Because as I said before, even when you EQ frequency response you can't make decays shorter and they will be audible.
And second, thanks to Tom Danley for the reminder, resonating media are non-linear, so you can't EQ what happens after EQ. Wavebourn
"
Cheers,
Jeff
Last edited:
As an info dumper, that is sweet!
But with so many 'browsers' (non-clickers; you know the type!), I'd:
Sy 2012
However, it is better when before application of EQ all high Q resonances were properly minimized mechanically. Why? Because as I said before, even when you EQ frequency response you can't make decays shorter and they will be audible.
And second, thanks to Tom Danley for the reminder, resonating media are non-linear, so you can't EQ what happens after EQ. Wavebourn
"
Cheers,
Jeff
I guess all that answers the question (#2709). And, my short conclusion is in there somewhere as well. This, by now, has been written about extensively.
So, I gave you the bottom line and hope it will save you a lot of money and time.
In 1977 RTA article I said then that one should try to get best (flat) results first and use EQ as last resort and then only a little of it.
THx-RNMarsh
Last edited:
I don't think in most domestic rooms it's an "or" solution, at least not optimally. Your own M2's have controlled directivity, *but* they're fairly wide dispersion, so it's tough to keep energy off the walls. (see graphic on page 7 for JBL's own literature, but the wide dispersion is noted elsewhere: https://www.jblpro.com/ProductAttachments/M2_Brochure_Jan2013.pdf)
If you've got a big room with some space to breath, that's great, but in order to really beam down a source, you've got to have pretty tiny beamwidths in, say a room that's 15x20 feet (4.5x6'ish meters, roughly) in order to keep the horizontal "spray" from getting mixed up on the walls. That says pretty big horns to keep something like a 60 degree horizontal beamwidth (even 90 degrees!) down to 800'ish Hz. So early reflections, both horizontal and vertical are a real problem.
I haven't really invested in room treatments given my life circumstances, but that will be (listening wise) the first concern with a listening room whenever I finally get a place of my own.
I agree... and said a few days ago... 60-90 degree is best.
I also have to remind some that JBL uses a rather large atten to describe its horizontal dispersion. I use -3dB.
I do have a very large room. and I make allowances for any remaining horizontal dispersion. And, I listen near-field. Before the M2's I had figure of 8 polar response panel speakers (ESL) which helped some. Maybe there will be an M3 with more narrow but controlled dispersion. Perfection.
If you can follow my listed specs and guide-lines, you will hear a very accurate reproduction.
THx-RNMarsh
I also have to remind some that JBL uses a rather large atten to describe its horizontal dispersion. I use -3dB.
I do have a very large room. and I make allowances for any remaining horizontal dispersion. And, I listen near-field. Before the M2's I had figure of 8 polar response panel speakers (ESL) which helped some. Maybe there will be an M3 with more narrow but controlled dispersion. Perfection.
If you can follow my listed specs and guide-lines, you will hear a very accurate reproduction.
THx-RNMarsh
Last edited:
My experience of hearing many customers' rooms over the years is a strong preference for high ceilings and complex side walls - lots of books (especially), and all kinds of media storage. The opposite of fashionably minimalist.
In the USA the great unwashed masses (like me) get 8 foot ceilings, the nouveau riche get 10 foot ceilings, and old money gets something that sounds really good.
A perhaps useful metric is that a room pleasant to spend time in with another person also sounds best for music. IMHO of course.
In the USA the great unwashed masses (like me) get 8 foot ceilings, the nouveau riche get 10 foot ceilings, and old money gets something that sounds really good.
A perhaps useful metric is that a room pleasant to spend time in with another person also sounds best for music. IMHO of course.
Yes, it is depressing to be in a small room with 8 foot ceiling and try to have some sort of accurate sound. Might even be better to go to headphones and leave the HiFi gear for fun and background.
??
When i was young and renting.... I used to look for a large living room area and/or connected to dinning so as to get enough space/volume. Same for buying... look into the living room. Where would the speakers go and where would I listen? I rented a 3 bedroom just for the extra living room space. When I could not afford the size, i rented a house and used the 2 car garage to set up a listening room... Sofa and speakers etc. That actually worked fairly well after I put a rug r two down. Turned the garage into a den/man cave. Where there is the will, there is a way.
-RM
??
When i was young and renting.... I used to look for a large living room area and/or connected to dinning so as to get enough space/volume. Same for buying... look into the living room. Where would the speakers go and where would I listen? I rented a 3 bedroom just for the extra living room space. When I could not afford the size, i rented a house and used the 2 car garage to set up a listening room... Sofa and speakers etc. That actually worked fairly well after I put a rug r two down. Turned the garage into a den/man cave. Where there is the will, there is a way.
-RM
Last edited:
I know how awful, almost as bad as not having a blow dried Bentley in the garage. I have 20' ceilings BTW.
Nearfield helps a lot of course, but that's a solitary thing pretty much. Or really large radiating surfaces/ horns.
These mics are as much 'musical instruments' as the drums, Marshall quads, Vox Blue Bulldogs, Ampeg fridges etc etc that they are used to capture sound of.
All this jargon is describing sound sources of extreme character and an appropriate mic with the correct complimentary character is part of the end result that slots into a complete mix.
You have heard and loved more 421's and 57's than you will ever know. 🙂
T
That was what he said to me recently about drivers, not the room, in a thread about driver distortion.
IMO, the people doing the recording often dont actually have any idea about mic characteristics... their response on or off axis. Look at a recording and you see mics at odd angles just to be out of the musicians way. many are near 90 right angle and for a cardioid, has little high freq response (making a poor mic pickup even worse). Thank the Gods for the Mastering Lab with good ears and good accurate speakers. Today, accurate mics (flat) could be used and then EQ'ed/mixed to the sound the producer likes. But keep the Master recording as good as possible.
Now I understand some like a mic for its 'sound' regardless. I have recorded, been to recording, had recording business, used a lot of different mics. I've been to recording at G.Lucas studio in Marin county, Calif and watched classical recordings. I have produced a recording for Kavi's Water Lily. It is accurately recorded. Seen studios and 'live' recording systems. Been there, done that.
An accurate playback is needed in Mastering and IMO at home. Neither of these places are we 'producing' the sound.
Enjoy.
THx-RNMarsh
Last edited:
The only good W12 Bentley is a paid off Bentley. I'm still working on it.
Until this home I have now, I had same type house as most do... 8 foot ceiling type. Track home... spec built. But I have been here for the past 20 years and love it. Partially for the views, clean air, quiet and no crime. But also chosen for the Great Room size; The ceiling slopes from 18 feet to 13 feet and is red wood. 35 foot length. 15 feet wide. Very odd shapes and wall to wall carpeting and hidden absorption all around. The white Ritmuller sounds great in there.
All are welcome to come over and listen and have some wine.
THx-RNMarsh
At the beginning of the third octave analysers and filters, it was hype to equalize big PA systems for Rock concerts.
Both to avoid Larsen effect and try to get a better sound.
I remember the results were so catastrophic and the sound so awful that, near immédiatly, we decided to set the levels amounts at ears, looking at the analyser just to save time, finding where were the most important bumps and holes. If the holes beneficiated from the treatment, correction of peaks were, indeed, always critical. The best results were somewhere in the middle between flat and original.
May-be a problem of phases with the third octave equalizers ?
Last edited:
There is a big difference between equalizing a system for playback compared to one for reinforcement.
The studio guys are used to dead rooms and flat frequency response at a reasonably defined sweet spot. Very low tolerance for monitor loudspeakers with significant resonances.
Some popular music PA systems have significant low frequency resonances. Others deliberately use equalization to boost the low frequencies. That is in addition to the frequent use of colored microphones.
Then for voice lift systems equalization is used to minimize feedback.
Using equalization to flatten frequency response in the far field makes voice lift systems sound artificial.
Most of my systems use less than five filters. Three is better if I can get the results measured by gain before feedback.
Floor and podium bounce require two filters.
The most important parameter in my systems is not musicality. It is speech intelligibility. Actually not hard to measure.
The studio guys are used to dead rooms and flat frequency response at a reasonably defined sweet spot. Very low tolerance for monitor loudspeakers with significant resonances.
Some popular music PA systems have significant low frequency resonances. Others deliberately use equalization to boost the low frequencies. That is in addition to the frequent use of colored microphones.
Then for voice lift systems equalization is used to minimize feedback.
Using equalization to flatten frequency response in the far field makes voice lift systems sound artificial.
Most of my systems use less than five filters. Three is better if I can get the results measured by gain before feedback.
Floor and podium bounce require two filters.
The most important parameter in my systems is not musicality. It is speech intelligibility. Actually not hard to measure.
Last edited:
- Status
- Not open for further replies.