Volume pot adjustment

Tweaker · « **on:** 2 Apr 2005, 04:25 am »

I have a pair of RM2's and would like to offer some volume pot adjustment advice. Don't assume that because you have the L-pad adjustments set identically to 2:00 or whatever on both speakers that the output will be the same for each speaker. The L-pads don't seem to have a very tight tolerance, at least mine don't or perhaps they are not installed exactly the same (the entire housing rotated a bit) I don't know but 2:00 on my left mid panel is about the same as 5:00 on my right speakers mid panel. Quite a difference in output. I use a Radio Shack spl meter held hard up against the middle of the panels (and tweeters because they too are different) and adjust the output of each panel and tweeter using pink noise so each is exactly the same. I then re-check them every few months to make sure they haven't drifted. The tweeter and mid panel speakers on my RM's are output matched identically this way and each L-pad is in a different position with the mids being way different from each other.
My apologied if this subject has been discussed before.

warnerwh · « **Reply #1 on:** 2 Apr 2005, 05:37 am »

I haven't measured but listen very hard to every nuance I can for hours. With the pair of RM 40's I have my pots are identical on both speakers and balance seems perfect. On my last set of speakers, Supertower/R SE's, there were three pots on each and on the right speaker I had the tweeter level a notch below the left side and all others were at the factory recommended starting points. You are correct that it's possible that they may not be set perfect from the factory but the room layout is what will dictate where they should be set as one side could easily be brighter than the other side even in a pretty symetrical room like what I have. On the Supertowers my settings were identical to factory starting recommendation and on the RM 40's the mids are at the starting point of 12:30 and tweeters are at 12:00. In both cases I've found best balance in my room very near the factory recommended starting point. My room, 12x17x7, is LEDE with bass traps.

John Casler · « **Reply #2 on:** 4 Apr 2005, 01:07 am »

Quote from: Tweaker

I have a pair of RM2's and would like to offer some volume pot adjustment advice. Don't assume that because you have the L-pad adjustments set identically to 2:00 or whatever on both speakers that the output will be the same for each speaker. The L-pads don't seem to have a very tight tolerance, at least mine don't or perhaps they are not installed exactly the same (the entire housing rotated a bit) I don't know but 2:00 on my left mid panel is about the same as 5:00 on my right speakers mid panel. Quite a ...

Hi Tweaker,

While your situation is unusual, It is conceivable that somehow the L-Pad was "moved" before the glue set and that your pad "is" off.

While this is not detrimental to the sound it does make setting them different than we generally suggest.

I would suggest that you turn each L-pad as far as it will go "counter clockwise and mark that position with a small mark. Then turn each as far "clockwise" as possible and also mark that position.

Then set the L-pad at the "midway" position between the two marks.

That is your 12:00 position for "that" pad.

Make all your adjustments based on that "re-calibration" scheme.

Hope that helps.

Tweaker · « **Reply #3 on:** 4 Apr 2005, 03:16 am »

John,
Thanks, good advice. I have got them dialed in to a tee, however,using the Radio Shack meter and am very happy with the results. I think that even with the pots being exactly matched I would still want to use the SPL meter as I described to make sure the outputs are precisely matched. For me it takes the guess-work/uncertainty out. I'm just kinda fussy that way. I'm also one of those who uses a tape measure to make sure each speaker is precisely the same distance from the side and rear walls and toed in at exactly the same angle. Just can't help myself.

zybar · « **Reply #4 on:** 4 Apr 2005, 03:37 am »

Quote from: Tweaker

John,
Thanks, good advice. I have got them dialed in to a tee, however,using the Radio Shack meter and am very happy with the results. I think that even with the pots being exactly matched I would still want to use the SPL meter as I described to make sure the outputs are precisely matched. For me it takes the guess-work/uncertainty out. I'm just kinda fussy that way. I'm also one of those who uses a tape measure to make sure each speaker is precisely the same distance from the side and rear walls and toed in at exactly the same angle. Just can't help myself.

Tweaker,

Hope you aren't using 1/3 octave tones to measure things. If you are, you want to change to 1/12 octave tones ASAP. Run the measurments with the 1/12 octave tones and you will be shocked at the difference.

George

John Casler · « **Reply #5 on:** 4 Apr 2005, 03:59 am »

Quote from: Tweaker

John,
Thanks, good advice. I have got them dialed in to a tee, however,using the Radio Shack meter and am very happy with the results. I think that even with the pots being exactly matched I would still want to use the SPL meter as I described to make sure the outputs are precisely matched. For me it takes the guess-work/uncertainty out. I'm just kinda fussy that way. I'm also one of those who uses a tape measure to make sure each speaker is precisely the same distance from the side and rear walls and toed in at exactly the same angle. Just can't help myself.

That's why you're the "Tweaker"

Tweaker · « **Reply #6 on:** 4 Apr 2005, 12:12 pm »

zybar,
just using pink noise to measure/match the outputs.

ctviggen · « **Reply #7 on:** 4 Apr 2005, 12:40 pm »

You know, that's not a bad idea. How accurate is the RS meter, though? I might do that. Also, I had originally thought that one of my speakers was different than another, so that imaging was shifter. However, when I put a Real Trap in front of my RPTV and matching stand, this helped imaging tremendously. The image was no longer shifted. So, for critical listening, I put Real Traps in front of my equipment. (The other listening is HT anyway, and I have a center channel for that.)

ted_b · « **Reply #8 on:** 4 Apr 2005, 01:17 pm »

Quote from: Tweaker

zybar,
just using pink noise to measure/match the outputs.

Tweaker,
How do you measure and adjust both tweeter and mid pots with full-bandwidth pink noise? (I assume RM2's have both, right?)

Ted

ctviggen · « **Reply #9 on:** 4 Apr 2005, 01:37 pm »

I think he holds the RS meter up to a midrange on one speaker and records the level. He then adjusts the other speaker to the same level. For the tweeter, he holds the RS meter up to the tweeter and records the level, then adjusts the other speaker to the same level. You'd have to do this at close range, in other words, right near the speaker element.

Tweaker · « **Reply #10 on:** 4 Apr 2005, 08:47 pm »

Allright, let me explain exactly how I do this. I play a test cd's pink noise track set to a modest level as I am measuring directly of off the speaker. Set the spl meter to slow and c-weighted for the mids, a-weighted for the tweets. Then I take a reading directly of off the center of the top mid range panel. The meter is held directly against the panel. I take note of the reading and then go to the other speaker and kneel down to one side and while holding the meter up against it's top mid panel use my other hand to adjust the pot using a screwdiver to exactly match the level I measured of off the other speaker. I then repeat with the tweeters, again holding the meter hard up against the tweeter. Then I'll play some music to see if the blend sounds right to the woofer. If not I'll repeat the procedure except I'll adjust the output up or down as required by just 1 dB at a time untill I'm happy with the results. Then every few months or so I recheck to make sure that no drift has occured.

ted_b · « **Reply #11 on:** 5 Apr 2005, 12:10 am »

Well, I use a 1/12 octave and measure from the listening position. That way I've measured the speakers interaction with the room, as well. Although my room is quite symmetrical, and the speakers are within 1/4 inch of symmetrical in each corner/side measurement, I find that measuring from the listening position helps me feel the speakers are balanced correctly. I'll augment it, though, with your process, and see if there are benefits for me. Thx,

Ted

warnerwh · « **Reply #12 on:** 5 Apr 2005, 12:48 am »

Where do you get a cd with tones spaced at 1/12th octave?

ted_b · « **Reply #13 on:** 5 Apr 2005, 03:52 am »

Quote from: warnerwh

Where do you get a cd with tones spaced at 1/12th octave?

I have one from Revel (Madrigal) that a buddy gave me that are 1/12. In addition, I use the new tones from Realtraps for rough bass measurement. They are 1hz spaced! It can be downloaded from their website.

Ted

ctviggen · « **Reply #14 on:** 5 Apr 2005, 08:30 am »

So, do you turn one channel off and measure that channel, then reverse this? I have the ETF software and was thinking about doing the same, but I'm not sure I'd be able to tell what to do once I got the results. Just looking at low frequencies and all the peaks and dips can drive one crazy.

ted_b · « **Reply #15 on:** 5 Apr 2005, 02:06 pm »

Yes, I just unhook one ic from the pre (very accessible) then the other. ETF is well-used here. I'm sure you'll get some responses. Maybe a new thread is needed.

Ted

John Casler · « **Reply #16 on:** 5 Apr 2005, 04:12 pm »

I think for the purpose of "balancing" the L-pads, the White/Pink Noise is the only type of tone one might find useful.

That is, the White/Pink Noise could also possibly be used at the woofer.

(I might add that you would have to set the initial SPL at the woofer, then proceed to the L-pads)

I haven't tried this yet, (so I can's say it will cause the proper blending at the listening area) but it would seem like a reasonable place to start.

The "specific" frequency/octave tones will only be valuable for band equilization, or for use with a DSP system, since specific tone bands cannot be adjusted at the L-pads.

ted_b · « **Reply #17 on:** 5 Apr 2005, 05:25 pm »

John and Tweaker,
How do you set the output for the two different l-pads with one pink/white noise output? IOW, how do you measure what each l-pad is doing when both are active during full-bandwidth pink noise, and all you are using is an SPL meter? I use separate bands so as to measure the tweeter pad/output separate from the mid output. I make sure I measure a few bands in each range.

Ted

John Casler · « **Reply #18 on:** 5 Apr 2005, 05:31 pm »

Well I just did a "Quicky" test and ran some Pink Noise through and measured all 3 drivers against their opposite speaker counterpart.

I didn't have to make any adjustment. The left and right FST were within .5 db and the neos and woofs were exactly the same.

But I did see where this method while yeilding a balance between L&R drivers could be valuable, it is not a good way to assess the balance between the drivers in a single speaker.

My 626Rs have a single Neopanel and the RM/x have 6. I don't see how this could give a useful "balancing" with multiple panels.

Brian has mentioned that the best method is to use your "auralcranial" measuring device and look (listen for)

Quote

maximum clarity, definition and good tonal balance

It would appear that the actual "balance/blend" of the drivers at the listening position will be affected by distance, room, listening height, (angular incidence to all drivers) and number of drivers, so a specific balance "at the driver" itself, while it might offer a starting point, should be listener adjusted as needed.

John Casler · « **Reply #19 on:** 5 Apr 2005, 05:37 pm »

Quote from: ted_b

John and Tweaker,
How do you set the output for the two different l-pads with one pink/white noise output? IOW, how do you measure what each l-pad is doing when both are active during full-bandwidth pink noise, and all you are using is an SPL meter? I use separate bands so as to measure the tweeter pad/output separate from the mid output. I make sure I measure a few bands in each range.

Ted

Hi Ted,

I simply put the meter right on the center of the driver being measured.

Again, I don't think this is valuable "except" to check left to right speaker driver balance.

While B, could answer this much better than I, I don't know what "balance" reading would be between the FST and the Neopanel, much less between multiple Neos