Thick person about to cry - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 42 Old 05-20-08, 04:51 AM
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Re: Thick person about to cry

OK, the Stereo input to the soundcard should split into 2 RCA ends, only one of them will work when connected to the SPL meter. Be sure to switch between them and try.

I am also sure you are already a Shack success story

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Yamaha RX-V2500, Wharfedale Diamond 9.6 Fronts, Wharfedale Diamond CM Center, Diamond DFS Surround and rear, Behringer FBQ 2496, Dual RL-P18s 625L LLTs, Dual TA-2400 Pro (2 * 2000 W Amp), Samsung HD870 DVD player, Carada BW 16:9 106" screen, Epson TW-2000, 60 Gb PS3
Important HT proverbs:
- "You can never have too much headroom" (talking about bass)
- "you can never have too big a screen" (talking about still pictures)


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post #22 of 42 Old 05-20-08, 02:16 PM Thread Starter
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Re: Thick person about to cry

Right oh chaps,

I bit the bullet and went and bought a soundblaster live 24, usb soundcard. I did what i did before and checked the settings against the soundblaster sticky at the top of the page and produced the following.

I would appreciate it if someone gave me the nod before i proceed with getting the rest of it wrong.

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post #23 of 42 Old 05-20-08, 02:48 PM
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Re: Thick person about to cry

Blasted,

I think you really need to take the time to carefully read the help files again. This will save you a lot of time.

After that you need to check the thread few posts above where Brucek made detailed explanation. Then if you have a problem, let us know.

PS: The response of the soundcard looks good to me

ASME AI
Yamaha RX-V2500, Wharfedale Diamond 9.6 Fronts, Wharfedale Diamond CM Center, Diamond DFS Surround and rear, Behringer FBQ 2496, Dual RL-P18s 625L LLTs, Dual TA-2400 Pro (2 * 2000 W Amp), Samsung HD870 DVD player, Carada BW 16:9 106" screen, Epson TW-2000, 60 Gb PS3
Important HT proverbs:
- "You can never have too much headroom" (talking about bass)
- "you can never have too big a screen" (talking about still pictures)


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post #24 of 42 Old 05-20-08, 02:57 PM
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Re: Thick person about to cry

Quote:
I would appreciate it if someone gave me the nod before i proceed
Proceed............

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post #25 of 42 Old 05-21-08, 04:43 PM Thread Starter
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Re: Thick person about to cry

I think i am getting somwhere, slowely, but getting there none the less.

I switched to the soundblaster live 24 external usb card, set it up as per what the on line notes say and followed through till i made a measurment.

the first measurment was set to finish at 200



the second one i set the upper limit at 24,000, this did not finish as it said clipping was detected, and advised me to lower the volume on my amp, which i did. I got the following



im not quite sure whats going off but it looks odd at the end.

Am i on the right path or am I making a massive mistake?
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post #26 of 42 Old 05-21-08, 04:56 PM
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Re: Thick person about to cry

They're both quite good except for graph scaling.

For the subwoofer graph change the axis to the standard vertical 45dB-105db and the horizontal to 15Hz-200Hz. Always return to this standard after each measure with a simple push of the Graph Limits button at the top right hand corner of REW.

For the full range graph keep the standard vertical 45dB-105dB, but change the horizontal to 15Hz-20000Hz. Also with full range graphs, click the Smoothing to 1/3 octave to remove the comb filtering.

I also don't see that you have loaded a meter calibration file? This is required. They are obtained from our download page for the Radio Shack and Galaxy and ECM8000 types.

If you are using an ECM8000 then you may continue to measure to 20000Hz. If you are using a Radio Shack meter, then limit the upper range to about 3000Hz. They're not reliable after that.

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post #27 of 42 Old 05-21-08, 05:12 PM Thread Starter
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Re: Thick person about to cry

Thanks for that, i have re done it and got a better looking graph



this is with the radio shack cal applied and 1/3 octave smoothing.

So from here is it case of moving it around and twidlling the dials, retaking measurments until i get a flat responce? To be honest im not sure what i should even be aiming for.
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post #28 of 42 Old 05-21-08, 05:26 PM Thread Starter
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Re: Thick person about to cry

i have been randomly fiddling with the dials and managed to do this, the roll of seems smoother and the dips less pronounced around 80hz, assuming i am reading it right though

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post #29 of 42 Old 05-21-08, 06:01 PM Thread Starter
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Re: Thick person about to cry

i turned the gain up to 2 o clock and shifted it to the other side of the room, now facing the sitting position and got this

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post #30 of 42 Old 05-21-08, 06:41 PM
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Re: Thick person about to cry

Quote:
i have re done it and got a better looking graph
I won't let you off the hook yet.

You must always use LOG (logarithmic) graphs and not LIN (linear) graphs as you've done. Push the Freq Axis button to accomplish that. The look will change quite a bit when you do that.

Also note that all the graphs you show (besides the LOG / LIN problem) are not 45dB-105dB vertical and 15Hz-200Hz horizontal.

Quote:
To be honest im not sure what i should even be aiming for.
OK, well now that you are an expert in measuring, I'll tell you what you're looking for.

You should first measure the sub by itself without the mains. You accomplish this by simply disconnecting the mains (with the power off) and running the sub as you normally would through your receiver using the standard crossover point. Always measure in stereo mode BTW.

You set the target line on REW at the crossover point that you normally use (i.e. 80Hz) and your goal is to try and get as close to that target as possible. You can do this with placement, treatment or EQ or a combination of all three.

Next, you add the mains to the sub and continue to measure the same way up to 200 Hz. Now you try and get the sub and mains level matched and the transition at the crossover as smooth as possible (usually with the phase control on the sub).

The end result should be a smooth flat line. Some like to boost the bottom end somewhat to get a more natural sounding bass (they call it a house curve).

See the pic below. It shows the desired target for a 80Hz crossed sub combined with a desired target for 80Hz crossed mains. The additive resultant is the red line at the crossover......

Desired Subwoofer and Mains response targets
Thick person about to cry-crossover-80-sub-mains.jpg

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