Is my old RS SPL meter dead?

**Chrisbee** · **06-10-06, 04:36 AM**

Hi

And the prize for this years most stupid post goes to: Moi?

I just can't get a signal out of my (old analogue) RS SPL meter from the output jack socket.

I am assuming the RS meter has a mono output socket. So if I stick a stereo jack in there I should still get a signal on a stereo cable. Right?

I have tried every combination of cables and jack adaptors from my collection in every possible way I can think of but every jack and adaptor I have is stereo.

I put my voltmeter across the other end of a stereo jack to phono cable and got nothing on my multimeter even @ 200mV (at any dial setting) from the RS meter.

A continuity check on the cable proved the jack ring was connected to the phono pin and the jack base to the phono shield.

Should I make haste to the nearest pro gear shop and buy a long mini jack to mini jack mono cable? Or just buy another RS meter?

Is life meant to be this complicated?

Any ideas for a conclusive check for output from the RS meter socket using stereo cables or adaptors greatly appreciated.

BTW: The 9 Volt battery in the RS meter is fine.

**brucek** · **06-10-06, 07:04 AM**

Quote:

So if I stick a stereo jack in there I should still get a signal on a stereo cable. Right?

Don't know why you would assume this?

I've never seen a stereo RCA jack. Could you show us a picture. Below is a picture of three mono rca plugs.

brucek

**Chrisbee** · **06-10-06, 10:59 AM**

Thanks brucek

To me, a jack plug (or just jack) looks like the stereo example on the left.
(Formerly used for manual telephone exchanges and now mostly used for microphones and connecting pro-gear)

The pair on the right are phono (or RCA) plugs in the UK and commonly used for stereo audio interconnects.

Does this help?

**brucek** · **06-10-06, 11:52 AM**

OK, the pair of red and white male RCA connectors (on the right in your post) are the type that connect to the line output of the RS meter.
The pair you show are two mono RCA cables glued together for convenience.

See an example cable below:

In fact, you could connect the other end of that mono RCA connector cable (in my picture) into the left or right of the AUX or CD input of your receiver and the RS meter will act like a microphone. Use the dial on the RS meter and your receivers volume control as the adjusters for the volume and speak into the mic - does it work?

Then you can connect that mono RCA connector cable into one input of a stereo 1/8" phono to RCA adapter as shown below and connect that to the line in of your sound card.

brucek

**Chrisbee** · **06-10-06, 12:34 PM**

It grieves me to admit that for 15 years I have assumed (in error) that the output socket on my RS meter was a jack socket rather than an RCA (phono) socket.

I just discovered my error after dismantling the RS meter to discover a mini jack doesn't connect to any of the important bits of the socket.

So, finally, here is my first REW response curve for my 4 x 15" IB with the (40Hz) main speakers running as well. Crossover is at ~80Hz (24dB/octave). HT Shack correction figures applied.

BFD with just 4 filters set from manually recorded sinewaves. I can work on the BFD properly now I have REW working with my RS meter.

Never was I more pleased to see a wobbly line.

I have no idea what that massive dip is at ~150Hz.

Thanks to you all for your infinite patience.

**brucek** · **06-10-06, 01:34 PM**

Quote:

So, finally, here is my first REW response curve

Good stuff. Now we have something to work with.....

You should turn off your mains and do a sub only sweep with all BFD filters off as a starting point (and save that mdat file). Set your target to 80dB rather than 75dB also.

brucek

**Chrisbee** · **06-10-06, 01:54 PM**

Okay. What is this going to tell us?

**Chrisbee** · **06-10-06, 02:13 PM**

BFD switched to 3. (no filters set)

Microphone input Soundblaster Live! External.

Speakers muted.

80dB target.

80dB on RS meter Calibration on pink noise.

REW is not able to control input level. So input level manually set to around 0.25(?) to achieve a close match between REW auto sub curve and my response curve.

I must have missed the lecture on mdat files.

**brucek** · **06-10-06, 03:15 PM**

Quote:

Microphone input

Nope, has to be the line input to the soundcard.

Measure from 15Hz to 200hz....

brucek

**Chrisbee** · **06-10-06, 05:09 PM**

If only it were possible.

On Line-in I can only just get the first bar lit on the input level menu if I literally rap the microphone hard with my knuckles!

On the Microphone input I am totally swamped with signal level.

There seems to be no way to select/deselect between these two inputs on the SB Live!

I have input volume set at maximum.

I have discovered that plugging into the Microphone socket on the front seems to mute Line-in on the back of the box.

I'll keep digging in the SB L! Help files unless you have any good ideas to get Line-in working properly.

Thanks

**brucek** · **06-10-06, 05:51 PM**

Did you look over this thread ?

brucek

**Chrisbee** · **06-11-06, 03:12 AM**

Quote:

brucek wrote:

Did you look over this thread ?

brucek

I have now. (double checked again and all my "logical" settings were wrong)

Thanks for the reminder.

Here we are at last!

4 x 15" IB. Line in. No spkrs. No BFD. No soundcard cal. Old analogue meter correction factors loaded. 80dB target. 80Hz crossover @ 24dB/oct roll-off.

Now what?

**brucek** · **06-11-06, 07:08 AM**

Quote:

Now what?

Why no soundcard cal? Although the corrections are usually quite minor it's a good thing to do and you only do it once.

Anyway, the response looks good. If thats the 'target' you desire, a BFD could certainly correct it. You also appear to be rolling off faster than 24db/oct . Is this adjustable - do you have an external crossover or is it in your processor?

brucek

**Chrisbee** · **06-11-06, 07:40 AM**

Hi brucek

I just haven't got round to calibration on the new soundcard yet. I had such poor luck with both of my cheapy soundcards that I lot interest.
The External SB Live! is hopefully fairly flat anyway.

I'm using a Behringer CX2310 active crossover in 4 channels (2x stereo) to feed my 4 IB drivers in series pairs on the Low Channel driven by an EP2500.

My speakers are on the High Channel with their own Naim stereo power amp.

The CX2310 crossover has a fixed 24dB/octave crossover slope (AFAIK)

It's been fascinating running lots of sweeps with small movements of the RS meter backwards and forwards. With and without BFD. With and without speakers. With various crossover points etc.

One can learn a lot about the response in a relatively short time with these very brief REW test runs. It used to take me 40 minutes per run with sinewaves and results were completely different from REW!

I'm utterly amazed how high I had the bass compared to the speakers after using sinewave tones with manual recording of the results.

Without the BFD it now sounds very bass heavy thanks to the emphasis from 20-60Hz.

Next I'll try pulling that big bass hump down with some broad filters on the BFD.

**Chrisbee** · **06-11-06, 09:54 AM**

This is my best result so far:

Includes speakers and BFD with a borrowed house curve.

**brucek** · **06-11-06, 10:19 AM**

Quote:

This is my best result so far:

Given the house curve target you're using, it's quite good. Not much you can do below 20Hz with a BFD, so you live with that.

The general concensus is that a house curve sounds best when you begin to rise from the crossover down to about 30Hz and then level off from 30Hz down to the bottom end. You're doing just about the opposite of that. Have you tried about a 5dB rise starting at 80Hz and ending at 30Hz.
The housecurve.txt file would be:
30 5.0
80 0.0
That lift you've entered below 30Hz usually translates to a very heavy bottom end.

I encourage you to do the soundcard calibration since it's that area below 20Hz that some cards begin to fall of and the cal file will compensate for a more true picture of your response.....

brucek

**Chrisbee** · **06-11-06, 12:03 PM**

Thanks brucek

I'll fix the housecurve.

This is my soundcard calibration curve.

My wild guess is that the black splodge at high frequencies is an inadequately fast USB connection(?) Or is there another explanation?

I'm also guessing that it is so flat it has virtually no effect and can safely be ignored.(?)

**brucek** · **06-11-06, 12:43 PM**

Quote:

I'm also guessing that it is so flat it has virtually no effect and can safely be ignored.(?)

Yeah, doesn't look like it drops more than half a dB from 100Hz down to 10Hz. Actually you can just open SoundCardCal.cal in the Room EQ directory with notepad and it reads just like a meter cal file. You can see how much its down at 10Hz. Ignore it if you think it's insignificant....

brucek

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