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Discussion Starter #101
I tried my REW connection in a different analog source on the back of the receiver. I was able to get both speakers to play at the same time while reaching 75dB.

:huh:
 

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The only way you're going to solve the problem of whether that's an actual mammoth room mode or a bad crossover is to take the test outside.......... hehe you'll need a long speaker and microphone cable...............

brucek
 

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Discussion Starter #103

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Yeah, but there's bad and then there's real bad.

I think you take the prize so far as having the single largest room mode peak I've ever seen (or your receivers crossover is not engaged).

It's obvious to me why your mains were so low in relation to your subwoofer. It's because your SPL meter simply reads the level of that peak when using your receivers test tones, and so the rest of the mains above the peak frequency is down about 20dB from the 75dB setting.

The trouble is, that if you set your mains level to an actual 75dB, then that peak would be way too high and would add with the sub to produce an unusable system.

Sure would be nice to take a test outside that room. Outside would be the best option.

brucek
 

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Discussion Starter #105
What about doing your suggestion of taking a measurement at 1' from the speaker?

Here is a graph of possible room modes. Review the graph in post #64 and the previous one for the highs. It looks like a lot of the peaks correspond to this graph.
 

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I'm not doubting that you have a room mode at 50Hz. That's a given.......

I'm doubting your crossover.

OK, try this.

Do a single mains sweep with a crossover of 80Hz and then do the same sweep with the speaker set as large.

Make sure you set the levels for each test and don't move the mic.

Overlay the two plots on the All Measured tab and use the Trace offset adjustment to exactly line up the two plots around the 2KHz area, so that we're comparing apples to apples.

The two plots should show lots of difference below 80Hz.......

brucek
 

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Discussion Starter #107
:wits-end: No change. :wits-end:
 

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As I suspected.

There are lots of settings on receivers today that you may have missed?

I know that most receivers allow settings for each input. Is there any way you're using an input that the settings are enabled as Large Mains? I've even seen receivers that allow a different crossover for mains and sub.

OK, I wonder if the crossover for the sub is working. This one is easy to check.
Feed the soundcard to the receiver as normal, but now feed the soundcard line-in from your receivers subwoofer line output. This is now checking only the receiver, while the speakers and sub have been removed from the mix.
When you set the Check Levels you'll have to fuss with the receiver volume control a bit to get the REW line-in Input level set up, and then do the standard Calibrate to 75dB.
The result should be a text book 80Hz low pass plot.

brucek
 

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Discussion Starter #109
As I suspected.

There are lots of settings on receivers today that you may have missed?

I know that most receivers allow settings for each input. Is there any way you're using an input that the settings are enabled as Large Mains? I've even seen receivers that allow a different crossover for mains and sub.
There is only one screen to make those settings (see previous picture). I will try and filter through the different inputs and see if anything changes.

I turned down the sub setting to as low as it would go (-12dB) and took a measurement. You will see that pesky 50Hz mode surpassed the sub settings. The mains look to be still off more than 6dB from the lows.
 

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Discussion Starter #110
Went through all the different inputs and the settings screen did NOT change from small or xo of 80Hz.
 

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Discussion Starter #111
OK, I wonder if the crossover for the sub is working. This one is easy to check.
Feed the soundcard to the receiver as normal, but now feed the soundcard line-in from your receivers subwoofer line output. This is now checking only the receiver, while the speakers and sub have been removed from the mix.
When you set the Check Levels you'll have to fuss with the receiver volume control a bit to get the REW line-in Input level set up, and then do the standard Calibrate to 75dB.
The result should be a text book 80Hz low pass plot.
This will have to wait until tomorrow. Can I use any of the subs out after the y splitter and still get the same result? I don't have enough cable to connect before the y splitter.
 

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Splitter? I'm guessing you have more than one sub. In that case just disconnect all subs at the splitter and use it as the connection to the soundcard line-in.

brucek
 

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Discussion Starter #113
Splitter? I'm guessing you have more than one sub. In that case just disconnect all subs at the splitter and use it as the connection to the soundcard line-in.

brucek
Yes, LFM-1 EX and MBM-12. I will try and use one the lines from the splitter.
 

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Discussion Starter #114
OK, I wonder if the crossover for the sub is working. This one is easy to check.
Feed the soundcard to the receiver as normal, but now feed the soundcard line-in from your receivers subwoofer line output. This is now checking only the receiver, while the speakers and sub have been removed from the mix.
When you set the Check Levels you'll have to fuss with the receiver volume control a bit to get the REW line-in Input level set up, and then do the standard Calibrate to 75dB.
The result should be a text book 80Hz low pass plot.
Was able to give it a try tonight. What is this?
 

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Was able to give it a try tonight. What is this?
Once you clear your meter calibration file (not required since you aren't using a meter right now), you will see that it is a flat response, indicating that the subwoofer output has no crossover enabled.

You don't need to redo the measure after you remove the meter calibration file. Simply select the IR Windows buttons (top right corner) and then select Apply Windows in the popup. This will apply "no cal file" to your measure. You should then show a flat response (instead of the expected low pass response of a 80Hz crossover).

Looks like the subwoofer output is working without a crossover.

The output should look like the target you have showing if you clear the house curve.

brucek
 

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Discussion Starter #116
Looks like the subwoofer output is working without a crossover.
So basically, I need a new receiver or some form of filter for the L/R main speakers. :foottap: Any other options? Their cost?
 

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So basically, I need a new receiver or some form of filter for the L/R main speakers.
Well, you would also need a low pass for the sub and high passes for all other five main and surrround channels, so that's not really an option.

And I think you want to be sure that there's a problem. It certainly would appear so from your testing, but you want to be sure. Receivers aren't cheap.

So, let's be sure of the subwoofer measurement you just did, as it's easy and definitive (because no pesky speakers or rooms are involved).

You connected the right channel of the soundcards line-out to your CD or AUX (right and left) input of the receiver.
You connected the subwoofer output of the receiver back to the right channel of the soundcards line-in.
Your receiver is in stereo mode with no soundfield or effects turned on, and you have the CD or AUX input set to (main speakers as small) with an 80Hz crossover and subwoofer enabled.

You ran REW and set up the levels and did a measure from 0-200Hz and the result was a flat line response instead of a low pass filter target.

Is that correct?

brucek
 

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Discussion Starter #118
You connected the right channel of the soundcards line-out to your CD or AUX (right and left) input of the receiver.
You connected the subwoofer output of the receiver back to the right channel of the soundcards line-in.
Your receiver is in stereo mode with no soundfield or effects turned on, and you have the CD or AUX input set to (main speakers as small) with an 80Hz crossover and subwoofer enabled.

You ran REW and set up the levels and did a measure from 0-200Hz and the result was a flat line response instead of a low pass filter target.

Is that correct?
The only variation was that I connected to the splitter on the back of the BFD (which was in by-pass mode).

So.... Yes.
 

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Discussion Starter #119
Just checked and my center and (2) surrounds only do 100Hz to 20kHz. Where as my mains do 40Hz to 20kHz with a rolloff at 250Hz @ 12dB/octave.
 

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Well, I think you can see that the subwoofer loop should have measured with the crossover enabled at 80Hz rather than a straight line.

As an example, here's my processor doing the same test, except I use a 60Hz crossover.

You can see it tracks the target line so close, that it's hidden, except around 10Hz you see it start to drop off a bit. That's what it's suppose to look like. Yours isn't dropping rapidly at 80Hz as it should. It isn't filtered at all. I wish there was some switch you had in the wrong mode.....

bryston sp2 subwoofer 60hz cross loop.jpg

brucek
 
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