Measuring Frequency Response of Nearfield Monitors.

bouldersoundguy said:
Here's another way to look at it. Say you're monitoring at 83dB SPL and there's a reflection off a wall that's 70dB SPL, the difference being 13dB. If you turn the monitor level down 10dB the direct SPL will be 73dB and the reflected will be 60dB so the difference will still be 13dB. Since hearing and the dB scale are both logarithmic that 13dB difference sounds about the same regardless of the actual monitoring volume.
Click to expand...

I understand what you're saying about the end result. It's the "whys and therefore" that I will have to read up on. I'm one of those that is not satisfied just to know a thing. I also have to know how that thing was arrived at. Thanks for the correction and the pointing in the right direction.

All that aside.......in the end it comes down to what sound arrives at your ear and when. And to get back to my original post, I bet many would be surprised at just what their monitors really measure at their ear. Nothing like what the mfg shows in the sales brochure.
 
Gotta say got a little kungFu'd here. Assumed (wrongly) you were asking about measuring our own speakers, but then you're already doing that.
But then you thought that might have been a home brew' (or whatever :) ...freq plot ?
 
Naw....I knew it was a mfg. plot. In essence, I was calling him out on it. The idea here is to see if anyone has measured their monitors in place, where they are used, and from where they are listened to, and compare it to what the mfg offers for specs. We all know the room makes a difference. Just curious to see if anyone has measured to see what that is. No one mixes in a anechoic chamber with the speakers on an infinite baffle (ie: the same way the speakers are measured by the mfg.and their plots are generated from.)
 
bouldersoundguy said:
Not exactly. Doubling distance causes a 6dB drop in volume (inverse square relationship). Decibels are logarithmic because our hearing is logarithmic. The proportion of reflected to direct sound stays the same regardless of SPLs.
Click to expand...

Did a bit more reading and thinking. Question........What is the distance based on? Wave length (frequency)?
 
I think I'm getting it. Say my ears are 30" from the speakers and, for clarity, I have a wall also 30" from the speaker. The reflection will be -6db (30" to the wall and 30" back, 60". Distance doubled). Now if the wall is 60" away, It will be -6db at the wall and -12db back to my ears. Total 120" traveled. Inverse square numbers being 30", 60", 120" with 30" being the base distance.
 
solo2racr said:
I think I'm getting it. Say my ears are 30" from the speakers and, for clarity, I have a wall also 30" from the speaker. The reflection will be -6db (30" to the wall and 30" back, 60". Distance doubled). Now if the wall is 60" away, It will be -6db at the wall and -12db back to my ears. Total 120" traveled. Inverse square numbers being 30", 60", 120" with 30" being the base distance.
Click to expand...

You're getting it. Now you just have to account for the amount of sound that is scattered, absorbed or transmitted through the wall rather than reflected off it, and how that affects different frequencies.
 
There's certain point (or areas and distances?) from the sources in a room where the inverse square relationship gives over to the reflected energy correct? Not sure what the term for it is..
 
bouldersoundguy said:
You're getting it. Now you just have to account for the amount of sound that is scattered, absorbed or transmitted through the wall rather than reflected off it, and how that affects different frequencies.
Click to expand...

On that, I have a little better grasp on.
 
bouldersoundguy said:
Here's another way to look at it. Say you're monitoring at 83dB SPL and there's a reflection off a wall that's 70dB SPL, the difference being 13dB. If you turn the monitor level down 10dB the direct SPL will be 73dB and the reflected will be 60dB so the difference will still be 13dB. Since hearing and the dB scale are both logarithmic that 13dB difference sounds about the same regardless of the actual monitoring volume.
Click to expand...

This is all a bloody minefield/nightmare! Surely those figures will be frequency/level dependent due to the equal loudness curves (old FM curves)?
Then, HOW much that reflection matters depends upon the instantaneous signal level when it "gets back"? If the wall is 10 feet away a lot can happen musically in 20mSecs! Masking and all that swaddling.

EQ on monitors is a pretty forlorn exercise except for very minor deviations. A moments thought with a calculators shows that some pretty outrageous amplifier power would be needed unless you can live with buggerall headroom!

Oh, and in a "free field" sound does not decay by the inverse square law but by the reciprocal of "r" (I think, will look it up!) How it decays in a reverberant place I do not know. I DO know that for any specific space there is a "Critical Distance" where the direct and reverberant levels are equal (or so I seem to recall from my distant PA days!)



Dave.
 
vinylchord said:
My name's Chanell Carlstrand I'm new to the forum but I'm really excited to be part of a community that can help me grow my small business. Premier online retailer of re-issued vinyl records. Competitive prices, wide selection of new, Radiohead, Vinyl movement, Vinyl resurgence and factory sealed titles in a variety of genres.
Click to expand...

GO SPAM SOMEWHERE ELSE! Mods, you know what to do.
 
Do NOT eq you rmonitors. They are there (flat response) to give you accurate feedback. Just be sure to treat the wall right behind the speakers with acoustic foam panels or hang a folded up quilt from a thrift shop behind then so the wall is not adding anything in. Good Luck,
Rod Norman
Engineer

solo2racr said:
I assume you guys have measured. Besides the obvious "treat the room" answer, (not always practical to do it right), would an EQ in front of the monitors help? I would think it would, to a degree. Depending on the root problem.
Click to expand...
 
By and large, Rod, I agree with you. But I can think of 2 conditions in which you would want to EQ recording monitors. The first being that they are not all that flat to begin with and you may want to improve on that. The trick is to learn the difference between what's the room and what's the monitor. The second is if you want to emulate the average consumer stereo speaker. Of course for that you could just get a pair and listen. And back to the first reason, one could just replace them with better (read flatter) monitors. But then, not everyone can afford to drop $1000.00 - $2500.00/each for a good pair. Bear in mind that in both cases, an EQ is nothing more than a patch on a bad situation, and not a fix. Some (like myself) have to make do with what they have and can't afford to drop mega $$$$ on equipment.

On the other hand, once one learns their monitors and their deficiencies, then they will also know how to work around them. But no matter how good or bad they may be, one still needs to learn their monitors.
 
You must log in or register to reply here.
Back
Top