which frequencies?

[brucek]

More just to see how room responce changes with volume

If you want to see this, then have a single set of filters and use REW to do a response at the different volume levels....

brucek

[eddthompson]

i havnt had the time run sweeps or to set the filters yet, ive got a new subwoofer on order so im being lazy.

my theory is at 75 db you need to kill a peak by 3db, at 90db, the peak is even larger, so it needs more cut could be wrong though.

I got my bfd 1124 used for £50, no idea what that is in euros, about $90, total bargin for how much it improves the sound.

[brucek]

my theory is at 75 db you need to kill a peak by 3db, at 90db, the peak is even larger, so it needs more cut

In reality likely not, but in perception it may indeed be so. The frequency response of hearing at low sound pressure levels drops off rapidly for both low and high frequencies. This weakness was the idea behind the "loudness" button you might see on some older receivers. Compensation today for such a response curve with respect to sound level could easily be ameliorated within a DSP, but I don't suspect that's being done too often.

brucek

[dimmie]

I'm gonna take first meassurements tonight, when setting the input volume and the measurement level, should I use the speakers or the sub to meassure?, as asked in the little dialogue box?...

dimitri

[brucek]

should I use the speakers or the sub to meassure?,

SUB

[dimmie]

Well.....

I think I have the measurement level, input volume, spl calibrated and so far no problems.

I'm now tackling the soundcard calibration measurement, and the first part was ok, a pretty straight line with a roll off at the beginning and end. with a rimple at the end.

When I checked the calibration, I got the message that the highest level in the measurement is -21,7?.

And apparently that's too low....What is the smartest thing to do now?, I don't want to turn up the amp any further, as it is already at 0.

[brucek]

When I checked the calibration.............

Are you referring to the checking of the soundcard calibration, in that it was successful before doing any more measurements?

If so, did you select a TAB other than the soundcard tab to do this as is specified in the Help files?

brucek

[dimmie]

Yes I did, when I made the soundcard calibration measurement all looked ok. After that the help file tells you to select the left channel and check if the calibration was succesfull. I then get the message that the highest level in the measurement was too low(-21.7).


I hope I'm being clear enough, in my questioning.

[dimmie]

The red line in the "left"graph is around the 67 db. point. Which means it's too low right?, My real question is: Shouldn't this red line be around 75 db.?. And What's the best way to get it there?. Which volume should be changed?.

thanks

[dimmie]

I've upped the soundcard volume a bit, and now the red line reads about 75 db. But the previous measurements have been made with the soundcard volume in the middle. Should I leave the soundcard volume as it is now?, and start from the beginning, or can I just continue to room response measurements?. I'm afraid that my measurements will be off now. Because I've changed the soundcard output volume.

EDIT; I've upped the measurement level to -12 db. which gives me a straight red line at 75 db. The soundcard output is back in the middle now. Iguess I'm ready to start measuring. just have to set the target level, right?.

[dimmie]

Here's the first one, I can't realy make heads or tales from it......

Hope it will make some sense to you.

[dimmie]

And after restarting the program, and measuring again, I got this.

[brucek]

Set the vertical scale from 45db to 105dB and the horizontal scale from 20hz to 200hz.

Measure the sub only with the crossover set to your normal crossover and the mains shut off...

brucek

[dimmie]

brucek wrote:

Set the vertical scale from 45db to 105dB and the horizontal scale from 20hz to 200hz.

Measure the sub only with the crossover set to your normal crossover and the mains shut off...

brucek

Can I shut the mains off in REW?, or do I have to disconnect them?

[brucek]

Can I shut the mains off in REW?, or do I have to disconnect them?

REW is simply a signal generator that feeds your receiver, just like a CD player. It has no control over your systems speakers.

If you have a seperate amplifier for your mains, shut it off. If not, remove your speaker cables (with the power off) to the mains and don't allow then to short together. Obviously you'll have your receiver in stereo mode, so that no other multi-channel speakers will be on besides the mains.

brucek

[dimmie]

Here's the next one, looks a lot better.

One question though: When I close REW and start it up again later, do I have to make new calibrations before I begin?. or does the program remember these?.

I didn't calibrate anything today, before I ran the sweep.

Is the dotted line the soundcard response?.

thanks,

dimitri

[brucek]

When I close REW and start it up again later, do I have to make new calibrations before I begin?

Yes, since all the variables that control the setup have changed.... i.e. receiver levels, soundcard levels, microphone positioning etc.

REW will of course remember your soundcard calibration because it will load the file you created for it. You don't ever have to do that again.

Once you've done it a few times, the REW setup takes seconds...

Is the dotted line the soundcard response?.

Yes, you can turn that off the display with the same buttons you used to turn off the display of the RS meter calibration file graph.

brucek

[dimmie]

Ok, I'll start from the top again and see what changes.

I'll even make a new soundcard calibration file because I had some trouble yesterday with the output volume and played with the volume controls. It turned out I had to select the soundcard itself and not the java engine. because java didn't give me the proper volume(I think).

Or would you say that's not nescessary and the soundcard is properly calibrated?. Maybe you can tell just by looking at the graph.

[brucek]

Looks fine in the frequency area you're using it.........

[dimmie]

Ok, I'll leave that as is.

I calibrated and came up with this one.

What's your verdict bruce?, pretty big dip at 29 hz?.......will this be a problem, or is this a treatable response graph?. It doesn't show how low the monolith goes, does it?.

I guess I'll start reading my BFD manual, I'll have to get some rca/phono to jack plugs tomorrow.

Is there anything else I need to do before I start filtering?.

Dimitri

[brucek]

What's your verdict bruce?, pretty big dip at 29 hz?.......will this be a problem, or is this a treatable response graph?. It doesn't show how low the monolith goes, does it?

The response is pretty good. The peak at 46Hz is the one that would cause a bloated sound. The BFD will take care of all the peaks without any problem. The dip at 29Hz is too narrow to notice. It does tend to drop off at 30Hz though. Do you have it in a corner - that would be best to bring that bottom end up. That monolith shouldn't be down that far at 20Hz (~-10dB)...

brucek

[dimmie]

brucek wrote:

The response is pretty good. The peak at 46Hz is the one that would cause a bloated sound. The BFD will take care of all the peaks without any problem. The dip at 29Hz is too narrow to notice. It does tend to drop off at 30Hz though. Do you have it in a corner - that would be best to bring that bottom end up. That monolith shouldn't be down that far at 20Hz (~-10dB)...

brucek

I have it in a corner, and I'm sitting in the opposing corner.

I'll add a photo.

[brucek]

Looks like a large room with vaulted ceilings...

Your satellite mains are quite small, what do you have the sub crossed at - 80Hz?

brucek

[dimmie]

It's approx. 5 meters wide, 7 meters long and that's not counting the kitchen which takes a piece out of that space(as you can see in the second picture). I'm basicly in an L shaped room. The ceiling is about 2.5/3.0 meters high.

I've got the x-over set at 100 hz. now which is the middle option on my amp(80/100/150)

Should I measure all three?, I liked my sound the best at 150hz. really. But I did lose a lot of my stereo soundstage that way.

Dimitri

[brucek]

I've got the x-over set at 100 hz

Yeah, that's probably best, but the reason I asked is because to me it looks like the crossover is at 80Hz in your graph, both the subs response and REW setting?

Here's a 100Hz crossover set on REW - it looks different than yours......

I liked my sound the best at 150hz. really. But I did lose a lot of my stereo soundstage that way.

Yeah, no doubt, given the size of the mains. But, as you say, you will lose a lot of separation. You'll have to decide...

brucek