Need advice on REW, DDRC and spinorama

[Pieter1267]

So i found great EQ for my Revel F208 on Spinorama. First tip is to adjust gain setting of the pre anp to minus 2.6.

Since im using minidsp as the pre amp cross over into the amp that drives the F208 im confused. The minidsp controller software has a gain adjustment part but also an output level adjuster. Wich one does one adjust for the adviced gain setting?

Since im using a 2.2 setup, 2 other channels sending signal to subwoofer amp im also wondering: if the spinorama advice is to keep the gain input at a certain setting, wich controller on the subwoofer channels do i use to level the volume between main speakers and subwoofers? The gain or the output adjustment?

After extensively studying REW, autoeq and such im also confused about the target spl to adjust. Lots of rew teachers advice to set output with generator at around 75db. Then you make a few measurements and put them into the autoEQ section. Why is there a need to "match target spl?" Why can you lower or increase it? Is it for instance, okay to calibrate at 85 or 62db and use that as target? If not, why not?

Last question: the waterfall has colours and a ruler next to it. What are these colours for? I thought waterfall is only used to see how long the decay is, and that ridges are unwanted?

Okay another thing that i dont understand and ive read many help pages. The distortion graph. I see 6 or 7 measurements and then a thd number. Is the aim to get that as low as possible?

Been measuring for 3 days straight. Many many pages. My head spins.
I did learn that 2 subwoofers are fantastic and my dayton 15" so good even at current placement, they dont need a lot of filters. Ive only turned down 3db on 75hz. Further, full range speakers are more difficult to get right. The subs are the way to go to deal with as much as possible.

Thank you all!

 

[Keith_W]

So i found great EQ for my Revel F208 on Spinorama. First tip is to adjust gain setting of the pre anp to minus 2.6.

Since im using minidsp as the pre amp cross over into the amp that drives the F208 im confused. The minidsp controller software has a gain adjustment part but also an output level adjuster. Wich one does one adjust for the adviced gain setting?

Pass. I'll let someone who owns a MiniDSP explain that one.

After extensively studying REW, autoeq and such im also confused about the target spl to adjust. Lots of rew teachers advice to set output with generator at around 75db. Then you make a few measurements and put them into the autoEQ section. Why is there a need to "match target spl?" Why can you lower or increase it? Is it for instance, okay to calibrate at 85 or 62db and use that as target? If not, why not?

The measurement should be taken at your normal listening volume. This is because loudspeakers are nonlinear devices and suffer from dynamic compression or enhancement. Watch this video by Erin where he explains it beautifully:

Unfortunately, Amir did not measure compression when he reviewed the Revel F208's here. Erin routinely measures compression, but he hasn't reviewed this speaker.

This is Erin's review of the Revel F226. The 75dB measurement is normalised to 0dB, and what you want to see is the measurements taken at all other volume levels should be a flat line sitting exactly on top of 0dB. This means that measurement and corrections made at one level will be less relevant when played back at another level because (as you can see) the frequency response varies +/- 2dB ... and this is for a good speaker. A bad speaker will vary by much more.

This is why you measure at your listening volume. Listen to the sweep and ask yourself if you want to listen to music at that level. That is the level you should be measuring at, and performing corrections upon. The reason the 75dB recommendation exists is because most people listen at that volume. There is nothing special about 75dB measurement unless you were doing a formal measurement for publication, like Erin. This is for your home DSP, so measure at your listening volume.

Last question: the waterfall has colours and a ruler next to it. What are these colours for? I thought waterfall is only used to see how long the decay is, and that ridges are unwanted?

The colours indicate dB SPL below reference (0dB). Some waterfall graphs generated by other software suites omit the colours. But the colours certainly make it look prettier.

Okay another thing that i dont understand and ive read many help pages. The distortion graph. I see 6 or 7 measyrements abd then a thd number. Is the aim to get that as low as possible?

The aim is to avoid performing corrections that create copious distortion. Try this: measure your speaker at 65dB, then 75dB, then 85dB. Examine all the distortion graphs. You will see that no matter what you do, you will have more distortion the louder you play. All speakers are like this, even very good speakers like the Revels you own.

Some DSP might inappropriately try to boost a notch. If it does that, then you will see a spike of distortion associated with that notch.

Been measuring for 3 days straights. Many many pages. My head spins.

We have all been there! I am more skilled at reading measurements now, but I still find a head scratcher every now and then. So yeah, my head still spins.