LOL. Lots of nice systems with bass to 30 Hz to blast all through the house and my boys always default to the JBL Charge and Bluetooth from a phone. So nice to see the defective genes (audiophilia) skip a generation!
Mitch wants the recording playback room to create as little masking of the recording as possible (free field headphones). He's not trying to emulate a home playback environment.
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Have you figured out how much bass boost to apply on playback to counteract the lesser reverb time at home vs auditorium?
DDF - not in any precise manner, only by listening and adjusting. I target a subtle 3 dB rise at about 40 Hz starting below 100 Hz. This is not a lot and some would certainly like more (tastes will vary), but clearly a flat response below 100 Hz sounds anemic.
Regarding Mitch, I understand, but my point was that a typical small room will hardly mask the long reverb of a larger room at all - not something that I would worry much about. We completely agree on the early reflections at higher frequencies masking the imaging on the recording. If Mitch's position were absolute then an anechoic chamber would be ideal, but that is clearly not the case. We must have some local acoustic for a realistic playback, but we want to minimize certain characteristics that inhibit the perception of what is on the recording. This is a very fine line to walk.
Regarding Mitch, I understand, but my point was that a typical small room will hardly mask the long reverb of a larger room at all - not something that I would worry much about. We completely agree on the early reflections at higher frequencies masking the imaging on the recording. If Mitch's position were absolute then an anechoic chamber would be ideal, but that is clearly not the case. We must have some local acoustic for a realistic playback, but we want to minimize certain characteristics that inhibit the perception of what is on the recording. This is a very fine line to walk.
In small rooms the decay time at low frequencies is way longer than at middle and high frequencies. This is due to modes. In concert halls the decay time at low frequencies is not nearly as much higher than at higher frequencies. This explains why speakers that have flat anechoic response have a bass rise in a small room, but not in a large venues such as concert halls. A PA system that would measure flat in an anechoic chamber would sound horribly thin in a large venue. A 6 dB bass rise generally is a good starting point.
Keyser
That would only be true for a poorly damped room and ONLY right at the resonances (as I said). Averaged across frequency and the RT60 would be quite low in a room with any amount of damping. Even if the LF RT60 is higher in a small room at LFs it will not be as high as the RT60 found in a larger room. The only place that sound is absorbed at LFs is at the boundaries. In a small room the sound impinges the boundaries at least a 1000 times more often than it does in a large room. This results in a very large difference in RT60 across the frequency range.
That would only be true for a poorly damped room and ONLY right at the resonances (as I said). Averaged across frequency and the RT60 would be quite low in a room with any amount of damping. Even if the LF RT60 is higher in a small room at LFs it will not be as high as the RT60 found in a larger room. The only place that sound is absorbed at LFs is at the boundaries. In a small room the sound impinges the boundaries at least a 1000 times more often than it does in a large room. This results in a very large difference in RT60 across the frequency range.
Some time ago, in a different discussion, we talked about room size. Did we ever come to an approximate guideline of a small, medium and large room? Either in surface area or volume? I can't remember.
I'm wondering how any normal listening room has any damping in the bass region.
Other than wall flexure.
In fact I have a few studies on conventional North American style framing that shows that gypsum board clad interior walls and also exterior walls are essentially invisible in terms of being a reflector below 30 hertz.
Other than wall flexure.
In fact I have a few studies on conventional North American style framing that shows that gypsum board clad interior walls and also exterior walls are essentially invisible in terms of being a reflector below 30 hertz.
Pano - its always difficult to partition a continuum. All I would claim is that virtually all home listening rooms are small. Beyond that I don't have an opinion about "medium" and "large".
Mark
Leakage is the major loss at LFs, except in room construction like mine, which is hardly "code". In my room the walls are intended to flex (suspended) and use Constrained Layer Damping so they are very highly damped at LFs, but not leaky, because they are also double walled with internal insulation. I can only find a single mode in my room at about 30 Hz, and even it is fairly well damped. Above that and no modes are apparent at all.
Mark
Leakage is the major loss at LFs, except in room construction like mine, which is hardly "code". In my room the walls are intended to flex (suspended) and use Constrained Layer Damping so they are very highly damped at LFs, but not leaky, because they are also double walled with internal insulation. I can only find a single mode in my room at about 30 Hz, and even it is fairly well damped. Above that and no modes are apparent at all.
Earl what are your room dimensions?
I'm sure you know that modal points within a given listening space are dominated by the dimensions above all else. Walls what ever their STC rating will only reflect of pass the sound generated within the rooms boundaries. It's the geometry that makes the biggest difference.
I have worked on the design and construction of a few rooms built for sound isolation. I find it an interesting endeavor. And hard work to!
I'm sure you know that modal points within a given listening space are dominated by the dimensions above all else. Walls what ever their STC rating will only reflect of pass the sound generated within the rooms boundaries. It's the geometry that makes the biggest difference.
I have worked on the design and construction of a few rooms built for sound isolation. I find it an interesting endeavor. And hard work to!
My room is something like 22 x 14 x 8 ft.
I understand how modes work and how shape defines things. My PhD was on the LF modes in non-rectangular rooms.
I understand how modes work and how shape defines things. My PhD was on the LF modes in non-rectangular rooms.
While on opposite sides of this world, in different rooms with totally different speakers here's a side by side comparison of Mitch's favoured room curve compared to what I ended up liking the most in my room:
The curves look very similar to me. I didn't start with his curve as a target, I grew to like this over time.
I do have to say our room treatments do have strong similarities.
The curves look very similar to me. I didn't start with his curve as a target, I grew to like this over time.
I do have to say our room treatments do have strong similarities.
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Apart from the lower frequencies, in my opinion room-curves don't make much sense. What you need is a good speaker, with flat response and smooth dispersion. The response at the listening position very much reflects (no pun intended) the direct-to-indirect ratio.
This is true, but I think that people have almost universally found that a wide directivity at the HFs will sound bright if this response is flat. Turn it down a bit and it's not so bright. A directive speaker like a dome tweeter can probably get away with a flatter on-axis response because its power response has fallen so much.
I noticed that. On-axis would seem the dominant factor, especially when early reflections are eliminated.
@ Mitchba,
Great links and info you provided, thanks a lot for that.
Could you please tell me what is the dynamic gap needed (difference between the lowest and the maximum spl) to listen a red book reccording and also a 20 or 24/96 today reccording please ?
I try to know what could be a confortable average listening level ar home while not having to compressed dynamic peaks in relation to the maximun spl output my speakers allow ! Btw, in relation to the reccording industry, what max spl output capability do you advise for a speaker for having no compression on peaks with a home listening level (80 dB average ?) ?
Thanks a lot for your input of this (question is asked in relation to an ideal 24 bits DAC)
Great links and info you provided, thanks a lot for that.
Could you please tell me what is the dynamic gap needed (difference between the lowest and the maximum spl) to listen a red book reccording and also a 20 or 24/96 today reccording please ?
I try to know what could be a confortable average listening level ar home while not having to compressed dynamic peaks in relation to the maximun spl output my speakers allow ! Btw, in relation to the reccording industry, what max spl output capability do you advise for a speaker for having no compression on peaks with a home listening level (80 dB average ?) ?
Thanks a lot for your input of this (question is asked in relation to an ideal 24 bits DAC)
The maximum crest factor that I have measured out of 100s of Jazz recordings thus far is ~ 25 dB.
So to answer your question, I'd say that for 80dB average at the listening spot, you want speakers that can produce 105dB peaks at the same distance.
Marco
Thank you Marco,
Jazz is nearly half of my listenings 🙂
So 25 dB of dynamic gap !
Well, don't know about the reccordings of big orchestra but as the peaks can be for the most powerfull at 125-130 dB for drums & tambours... , so even with higher dynamic gaps, we are far with our domestic speakers to glue to the reality (not speaking of the room and its EQ to try to make it disseaper !
Jazz is nearly half of my listenings 🙂
So 25 dB of dynamic gap !
Well, don't know about the reccordings of big orchestra but as the peaks can be for the most powerfull at 125-130 dB for drums & tambours... , so even with higher dynamic gaps, we are far with our domestic speakers to glue to the reality (not speaking of the room and its EQ to try to make it disseaper !
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