REW Noob - Page 11 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #101 of 191 Old 09-10-08, 11:40 AM Thread Starter
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Re: REW Noob

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.

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post #102 of 191 Old 09-10-08, 12:03 PM
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Re: REW Noob

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...............

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post #103 of 191 Old 09-10-08, 12:28 PM Thread Starter
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Re: REW Noob

When I use this room mode calculator, it looks like 47Hz is bad!

http://www.bobgolds.com/Mode/RoomModes.htm

Room dimensions are 24' L x 12' W x 7.9' H
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post #104 of 191 Old 09-10-08, 12:38 PM
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Re: REW Noob

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.

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post #105 of 191 Old 09-10-08, 12:49 PM Thread Starter
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Re: REW Noob

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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post #106 of 191 Old 09-10-08, 12:57 PM
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Re: REW Noob

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.......

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post #107 of 191 Old 09-10-08, 01:11 PM Thread Starter
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Re: REW Noob

No change.
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post #108 of 191 Old 09-10-08, 01:26 PM
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Re: REW Noob

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.

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post #109 of 191 Old 09-10-08, 01:54 PM Thread Starter
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Re: REW Noob

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brucek wrote: View Post
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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post #110 of 191 Old 09-10-08, 02:25 PM Thread Starter
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Re: REW Noob

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