A few unanswered questions

[lovingdvd]

Hi - I'm just getting started and have spent the past day soaking up as much great info is available here and in the help file and AVS - great stuff.

Some quick background. I'm interested in using BFD and REW only to smooth out my sub. Currently I measure this (adjusted for dB / RadioShack SPL levels):

16 Hz 82 dB
20 Hz 82 dB
25 Hz 86 dB
31.5 Hz 92 dB
40 Hz 80 dB
50 Hz 74 dB
63 Hz 75 dB
80 Hz 70 dB

So my main goal is to smooth out the 25-35hz range and fill in from 50-80hz.

Here are some remaining questions I have after going over all this:

1) I read that target response allows selection of 12 or 24dB/octave crossover slopes. What does it default do and where can this be changed? I have a HSU sub - am I correct to use 24dB?

2) Am I correct that the best thing to do is to send the output from the sound card into the receiver, and let it apply its processing and crossover to the signal for my measurements? I then tell REW to use Full Range. Correct?

3) My fronts are set to Small and crossover is 80hz. The fronts are rated down to 32hz so they still put out some good base well below 80hz (because of the sloped cutoff). When I measure this 20-80hz range I want REW to take into account the bass from BOTH the front left AND right channels. Therefore I take it I need to feed both channels from the sound card output into my receiver, right? I ask because surprisingly the docs and diagrams only show hooping up the left OR right. Why would someone want to do this and leave the bass out of one of the fronts from the measurement if they are measuring Full Range?

4) Is there any type of test I can perform on my sound card (or any things I can look for in its software/drives) to see if it supports full duplex? For example perhaps there is only a certain setting in the software options under Windows sound controls available for cards that support full duplex?

5) Will REW run ok with the new Java 6 available from Sun?

6) Does anyone know of any higher end A/V receivers that have built in calibration capabilities and editable parametric EQ data specifically for the low bass say 20-100 hz? I could us a new receiver, so if so, it may be easier to just do all the tweaking in the receiver and not have to use the BFD?

Thanks!

[JohnM]

lovingdvd wrote:

1) I read that target response allows selection of 12 or 24dB/octave crossover slopes. What does it default do and where can this be changed? I have a HSU sub - am I correct to use 24dB?

That is set in the Target Settings pane. The sub low pass would usually be 24dB/octave.

lovingdvd wrote:

2) Am I correct that the best thing to do is to send the output from the sound card into the receiver, and let it apply its processing and crossover to the signal for my measurements? I then tell REW to use Full Range. Correct?

Yes, going through the receiver is best. You would tell REW to use Subwoofer when looking at measurements of the sub alone (e.g. disconnect your mains or switch off their amp), bass limited when measuring your main speakers and full range when measuring both sub and mains together.

lovingdvd wrote:

3) My fronts are set to Small and crossover is 80hz. The fronts are rated down to 32hz so they still put out some good base well below 80hz (because of the sloped cutoff). When I measure this 20-80hz range I want REW to take into account the bass from BOTH the front left AND right channels. Therefore I take it I need to feed both channels from the sound card output into my receiver, right? I ask because surprisingly the docs and diagrams only show hooping up the left OR right. Why would someone want to do this and leave the bass out of one of the fronts from the measurement if they are measuring Full Range?

You need to measure the various speakers/sub independently first to understand the contribution of each, so that you know which channel to apply filters to (if you have the ability to filter more than the sub), but you also need to measure combinations of speakers as the combined response can differ.

lovingdvd wrote:

4) Is there any type of test I can perform on my sound card (or any things I can look for in its software/drives) to see if it supports full duplex? For example perhaps there is only a certain setting in the software options under Windows sound controls available for cards that support full duplex?

Not really, just about every soundcard runs full duplex these days.

lovingdvd wrote:

5) Will REW run ok with the new Java 6 available from Sun?

Yes

lovingdvd wrote:

6) Does anyone know of any higher end A/V receivers that have built in calibration capabilities and editable parametric EQ data specifically for the low bass say 20-100 hz? I could us a new receiver, so if so, it may be easier to just do all the tweaking in the receiver and not have to use the BFD?

Lexicon and a few other high end brands have those features, but I believe a few other (more realistically priced) processors and receivers have similar features nowadays, try asking on the equipment forum.

[brucek]

I have a HSU sub - am I correct to use 24dB?

Yes...

Am I correct that the best thing to do is to send the output from the sound card into the receiver, and let it apply its processing and crossover to the signal for my measurements? I then tell REW to use Full Range. Correct?

Yes, to the first part of the question.
Why full range? Select subwoofer to equalize a subwoofer.

Why would someone want to do this and leave the bass out of one of the fronts from the measurement if they are measuring Full Range?

Because we normally only equalize the sub. The mains are generally set to small and any equalization of them is provided with room treatment or positioning. If you want to do your mains, then use a Y cable into left and right channel.

Is there any type of test I can perform on my sound card (or any things I can look for in its software/drives) to see if it supports full duplex?

Most cards support full duplex. Run the soundcard calibration test. If it works, you're fine....

Will REW run ok with the new Java 6 available from Sun?

"REW requires V5.0 or later of Sun's Java Runtime Environment"

brucek

[lovingdvd]

JohnM wrote:

You need to measure the various speakers/sub independently first to understand the contribution of each, so that you know which channel to apply filters to (if you have the ability to filter more than the sub), but you also need to measure combinations of speakers as the combined response can differ.

I do not have the ability to filter anything really except for the sub. Therefore just to try and keep things a bit more simple, I'm thinking that I will not take any separate measures. All I'm really after is that the "real" bass is smooth when playing in a complete system.

So in that case am I correct to assume that I should feed both right and level RCA plugs into the receiver? I know bass is non-directional, but if I don't feed them both then I'm thinking I'd only have bass coming out of one of the fronts and the sub, instead of both fronts and the sub which is what I need to be more like the real system running. Is this a correct assumption?

[lovingdvd]

brucek wrote:

Yes, to the first part of the question.
Why full range? Select subwoofer to equalize a subwoofer.

Well the reason I want to do the full range is because it doesn't really matter to me what the fronts are doing and how they are contributing, because I cannot reposition them or equalize them (short of what the Yamaha YPAO calibration does automatically).

So I figure I might as well just address the whole system i.e. full range from the gecko. Is this not a valid approach? Thanks.

[brucek]

So I figure I might as well just address the whole system i.e. full range from the gecko. Is this not a valid approach?

No, the sub is always equalized first, then the mains are added after that to see if they integrate well together in their levels and at the crossover. Use a Y cable at the receiver, it will be the best situation for testing the sub and mains together.

brucek

[lovingdvd]

brucek wrote:

No, the sub is always equalized first, then the mains are added after that to see if they integrate well together in their levels and at the crossover.

Thanks! I did not know this. So do I understand correctly then that I should equalize the sub first and get that flat (or well suited to my house curve).

Then once I am happy with that, add in the fronts and measure based on Full Range, and make any necessary adjustments based on that?

The only thing I'm thinking is that why not just calibrate everything together at once. Ultimately it seems like I'll just wind up with the same settings but following the way you suggest I'll have to calibrate twice to get there. Would it not be more direct to just do it all at once? Obviously I'm missing something or you wouldn't be recommending that approach - so I'm just trying to better understand the logic here.

Use a Y cable at the receiver, it will be the best situation for testing the sub and mains together.

With the soundcard hooked up to the receiver, obviously the fronts and sub are going to play together. So if I am going to do a sub only calibration, what's the best way to turn the speakers off?

Obviously I could just disconnect them. However I remember reading that it is very bad for an amplifier to be sending signals out to a speaker which is not attached. Will this be ok when I'm outputting 80dB to left/center/right and nothing is hooked up to it? If not then how do I isolate those channels so I can have the sub only play?
brucek[/quote]

[Dent]

brucek wrote:

If you want to do your mains, then use a Y cable into left and right channel.
brucek

I'm not understanding why you have to use a Y cable if you want to feed the left and right input of the receiver. You are basically saying to take one side of the soundcard's output (let's say the right channel) and split that signal with your Y cable so that the right channel feeds into both the left and right input of the receiver. The left and right output from the soundcard is supposed to carry identical signals so why can one not feed the left and right soundcard output into their respective inputs in the receiver?

[lovingdvd]

Dent wrote:

I'm not understanding why you have to use a Y cable if you want to feed the left and right input of the receiver. You are basically saying to take one side of the soundcard's output (let's say the right channel) and split that signal with your Y cable so that the right channel feeds into both the left and right input of the receiver. The left and right output from the soundcard is supposed to carry identical signals so why can one not feed the left and right soundcard output into their respective inputs in the receiver?

Good question. I am wondering the same thing. Thanks.

[brucek]

So do I understand correctly then that I should equalize the sub first and get that flat (or well suited to my house curve).

Equalize to the target crossover chosen in REW and the receiver (i.e. 80Hz)

The only thing I'm thinking is that why not just calibrate everything together at once.

Because you won't know if it's the mains or the sub that are contributing to the problem. Isolate the sub, and you'll know.

So if I am going to do a sub only calibration, what's the best way to turn the speakers off?

Obviously I could just disconnect them. However I remember reading that it is very bad for an amplifier to be sending signals out to a speaker which is not attached.

Disconnect them with the power off and ensure they don't touch. A solid state amplifier has no problem with it. No current, no power.... Use the receiver in stereo mode and you don't need to disconnect rear, centers, etc...

The left and right output from the soundcard is supposed to carry identical signals so why can one not feed the left and right soundcard output into their respective inputs in the receiver?

REW outputs on one channel only...... split it, if you want both mains playing.

brucek

[JohnM]

brucek wrote:

REW outputs on one channel only

REW puts the test signal on both left and right outputs, so you could just connect a stereo lead from soundcard to receiver.

[Dent]

JohnM wrote:

REW puts the test signal on both left and right outputs, so you could just connect a stereo lead from soundcard to receiver.

Thank you for clarifying that.