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Discussion Starter · #1 ·
Howdy all. Just getting started here with addressing real room interaction with the speakers. (A dilettante, I. Using reasonably nice gear, but nothing pro and just for fun). In short, I've spent the past 6-7 hours trying to figure this all out, and wondered if someone might be so kind as to let me know whether I've been at least headed in the right direction.

Using a Mac mini and the Rat Shack SPL meter. The onboard soundcard (such as it is) was looped and calibrated (at least I think so: running an offboard USB DAC, Ayre QB-9, which made the loop complicated, but ended up looping the RCA right channel back into the 1/2 of the mic input on the mini, with the other channel coming off of the Rat Shack. Seemed to work perfectly...?). The meter is calibrated. Everything appears to be functioning perfectly (at least within the limits of its tolerances -- realize that this is pretty inherently limited kit).

So, I've run dozens of tests. And they just look awfully wrong. Guess it looks reasonable (reasonably in need to serious help, but at least logically so) up to about 150hz, but then the db measurements just take a dive and begin to look irrational. We're talking about a 75db baseline that, above 150hz, begins trending around 30-35db. This just seems totally implausible, and leads me to suspect that I have done something wrong. But, what do I know...?

If all has gone as planned, there will be a graph attached here as well. Set to default / suggested parameters (which only begin to capture the hash above 150hz -- and which convinced me more and more that I've gone astray...). Ah, yes, appears to work. The graph is the averaged product of 8 sweeps, seems I had it set for 15Hz-15kHz.

So, lost at sea here a bit. Any pointers would be hugely appreciated. Of course, I would be happy, pleased and honored to offer up any additional bit of information that might be of use. Many thanks.
 

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Hi !

So, I've run dozens of tests. And they just look awfully wrong. Guess it looks reasonable (reasonably in need to serious help, but at least logically so) up to about 150 hz, but then the db measurements just take a dive and begin to look irrational. We're talking about a 75db baseline that, above 150hz, begins trending around 30-35db. This just seems totally implausible, and leads me to suspect that I have done something wrong. But, what do I know...?
How about simply uploading ( as an attachment ), the .mdat file that you're currently working from/with ?

I'll take a look at it & let you know if you're on the write track .


:sn:
 

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Discussion Starter · #3 ·
Oh, dear, but that's a wonderful idea. ;)

Let me, perhaps, offer a better file. Having performed dozens of readings, I quit in dismay to apply some mental lubricant (Knob Creek Bourbon, in fact) and then ran a couple more measurements for good measure. These make more sense to me. Now, things indeed go wacky and all combfilter-ee above a certain bandwidth -- but where its supposed to. Other than the passage to time, nothing has changed in the system.....

As far as attachments go, afraid that I failed to save the actual data file for the graph I posted. (Yes, clever, I agree). So, I've attached an older file that reflects what I would consider similarly irrational results as well as a newer file ("More Rational Data File") that is, well, as advertised -- at least in my avowedly ignorant opinion. Thanks again.
 

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> Here's a pic of both of your files ( combined into a single ) .

> I've smoothed them both with 1/3 octave smoothing ( a normal procedure for viewing full-range sweeps ).

> The huge ( deep "V" ) dips can be explained as nulls caused by floor reflections ( or other hard, flat surfaces ) .

> The significant difference in levels between LF & MR levels can be easily explained by the test mic position .

:sn:
 

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Discussion Starter · #5 ·
Many thanks. Guess that means that I'm on the right track -- that things aren't so patently irrational to be considered wrong. Clearly, I've got some room treatment to figure out. Know, and have known, that I've got a nasty bump on the bass end and some pronounced null fields on a sweep tone, but these numbers were definitely damaging my calm. Guess, as they say, acknowledging you have a problem is the first step.... Thanks again.
 

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Discussion Starter · #7 ·
OK, following much reading and days of new measurements, I might (repeat might) actually be getting the hang of this. This should be two measurements, one with little smoothing (1/48) and one with a lot (1/3). The measurements pretty consistent otherwise. More encouraging still, I have been getting very consistent measurements, on different days, following recalibration of all of the gear from scratch. (My inner child-scientist is encouraged by repeatable & verifiable results.) Also, I suppose, the low-end waterfall plot for the same 1/48 run. Just have to say, this program is way cool. Enjoying playing with it a whole lot. Any comments would be lovely -- just excited about this and eager to share (and my wife, bless her heart for humoring me, is just not the best of audiences).

And now that I seem to have reliable measurements, the need for actually doing something to address my issues is all the more stark. Fun as it is, however, sometimes wonder if ignorance is bliss. (While the wife definitely humors my playing with instruments and measuring stuff, she will by no means go for filling the corners of the living room with bass traps, let alone mucking with reflection points).... Alas. Any other bright ideas for taming the peaks and valleys? Cheers.
 

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And now that I seem to have reliable measurements, the need for actually doing something to address my issues is all the more stark. Fun as it is, however, sometimes wonder if ignorance is bliss. (While the wife definitely humors my playing with instruments and measuring stuff, she will by no means go for filling the corners of the living room with bass traps, let alone mucking with reflection points).... Alas. Any other bright ideas for taming the peaks and valleys? Cheers.
> Measuring things ( like speaker response within a room ) definitely opens up a "Pandoras Box" type situation .
> Unless your wife is unhappy with the way things sound then I think you are presently at an impasse ( until she gives you a buy in of some sort ) .

> FYI, the newest curve that you display really isn't all that stark ( ie; dished out lower mid & dished out presence area ) . I would look to address those areas electronically with EQ ( eventually ) .
> Maybe with a new AVR that has extensive EQ capabilities is in your future ( just spit-balling here ) ?
> The response weakness between 50 to 60hz might be somewhat addressable with new speaker positions, which might just have to wait until the better-half suggests re-arranging the furniture .

:sn:
 
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