[Prize78]

Hi all. I'll try to keep a very long story short! Basically, I have a DIY subwoofer: two drivers (Acoustic elegance av12's) mounted in a push pull configuration, sealed box. Powered by Behringer EP4000 power amp. I have recently upgraded a couple of items, namely, speakers to Monitor Audio Silver 6's and AV amp to Yamaha rxa3050. I had noticed that the bass was a little underwhelming, so decided to run REW to see what was going on. I'm having a nightmare of a job to get rew going. I've got a laptop that has line in and out, so I thought i'd be able to use these. Seemingly not as REW tells me that the 'impulse peak isn't in the right place - check settings'. So I have wound up wit a USB adaptor box, offering mic in, line in, front out, rear out and cen/bass out. So. I hooked up red rca to spl meter (radioshack analogue) into mic in (it doesn't work with line in) and left and right RCA's from 'front out' on splitter box into Yamaha video aux in on the front of receiver. I downloaded the calibration file from this forum and entered that accordingly. On running a measurement, i get a clipping message at the end telling me that input is too high (clipping), but persevered anyway.
Well, i'm getting all sorts of graphs now, and the last two measurements taken, gave exactly the same graph, when one of the measurements had the SPL meter on, and one didn't! So how does that work??!

This leads me to believe that I have a dodgy connection somewhere. Any ideas folks?

 

[JohnM]

There shouldn't be any problem using line out and line in on the laptop, so you'd be better sorting out why that wasn't working than just trying a completely different setup.

 

[Prize78]

There shouldn't be any problem using line out and line in on the laptop, so you'd be better sorting out why that wasn't working than just trying a completely different setup.

It says 'None' on the soundcard calibration section and i don't know how to get a file in there? Have tried the loop thing to calibrate but it just freezes?? Is there another way round??

 

[JohnM]

Freezing is unlikely. Calibrating the soundcard goes through a series of steps, click the Next button at the bottom of the soundcard preferences to go to each successive step. The overall process is described in the help.

 

[Prize78]

All I keep getting now is "soundcard didn't provide any data, make sure it's connected"?

 

[JohnM]

Probably best if you post a screenshot of your REW Soundcard preferences to see what you have selected and let us know what OS you are running and what the connections to/from your laptop are.

 

[Prize78]

RIght, after lots of messing about, I have finally got REW working as it should. Turns out the line in was muted!! Anyhow, have taken a few measurements with interesting results. (See graph)

Purple line is from a measurement taken from on the floor.
Pink line is from the main listening area.
Blue line is from the spl meter virtually touching the subwoofer cone.
Green line is from an alternative listening area.

Seemingly, from the main listening area, I am losing bass altogether in the 93Hz region, but only in that one spot, as from the alternative listening position, no such dip is present.

Am I best to have a go at the manual PEQ on the Yamaha for a start?
What alternatives are there to get rid of the dip??

 

[JohnM]

Anything you do with EQ will have the same effect at all listening positions, so if you try to lift a dip at one position you will create bumps anywhere there isn't a dip. EQ also cannot do anything about sharp, deep features in the response. The best starting point is to experiment with listening positions and speaker positions. A relatively quick way to explore that is to use REW's signal generator to play the Pink PN signal and look at the response on the RTA using the settings below, move the mic/meter or sub/speakers to different locations to see how the response changes.

 

[Prize78]

Anything you do with EQ will have the same effect at all listening positions, so if you try to lift a dip at one position you will create bumps anywhere there isn't a dip. EQ also cannot do anything about sharp, deep features in the response. The best starting point is to experiment with listening positions and speaker positions. A relatively quick way to explore that is to use REW's signal generator to play the Pink PN signal and look at the response on the RTA using the settings below, move the mic/meter or sub/speakers to different locations to see how the response changes.

View attachment 129481

Thanks for the suggestion. I shall give it a go. No idea where the real low end stuff has gone as I've seen this sub go down to about 7Hz (albeit in a different room). It's as though there's a filter on it cutting the low end out?

 

[JohnM]

Sub position, measurement position and room can have a very dramatic effect on the sub's measured LF extension.

 

[Prize78]

Sub position, measurement position and room can have a very dramatic effect on the sub's measured LF extension.

Yes i think I've just got an awkward room. In a nutshell, it's a rectangle with one of the 'long sides' getting about a foot wider as you get near the 'listening area'. Tv, LCR and sub are all on a 'short side' of the rectangle with the sub itself positioned in the corner. Options to move the sub Aden very limited. So am considering an Antimode to try and flatten my graph a little?