Non-noob noob questions about starting REW

[toecheese]

I've done all this before and I must have just lucked out.

But now, with a new fancy IB.. I'm brain dead.

This beast puts out a lot of low frequency sound (I know, I should post graphs, but I want to cover some basics first).

When I fire up REW, there's a curve for subs that looks a lot like the house curves people are talking about. Is that correct?

Assuming it is, I've tuned my sub-only to match it pretty closely.

However, when I add in my mains (sending signal to receiver instead of to bfd directly), it goes bad. I'm getting a lot of overlap in the 100Hz area and up.

So, for basics, once I add in my mains- and still am testing for sub frequencies:

1) To what should I set my receiver's crossover frequency? 100/150/200
2) What size should I set my receiver to think my main speakers are? (large/small)
3) There's a Bass Plus on the receiver- allegedly it gives a boost to the sub- what to do with it?

TIA

[brucek]

When I fire up REW, there's a curve for subs that looks a lot like the house curves people are talking about. Is that correct?

No, that's a subwoofer target that matches the target set in the left REW panel for level and crossover frequency and slope. If you set it to 80Hz and your receiver crossover is set to 80Hz, then your response should track that target.

However, when I add in my mains (sending signal to receiver instead of to bfd directly),

Normally, when you test a sub, the REW signal is fed to the receiver AUX or CD input and the crossover is set to the frequency you normally use. The mains would be turned off and a sub only measure taken.

1) To what should I set my receiver's crossover frequency? 100/150/200

Well, 80Hz is normal, but if you only have the selections you show, use 100Hz.

2) What size should I set my receiver to think my main speakers are? (large/small)

Always set your mains to small, so the crossover is engaged for both the sub and mains.

3) There's a Bass Plus on the receiver- allegedly it gives a boost to the sub- what to do with it?

Turn it off.

brucek

[toecheese]

Thanks BruceK- but my sub doesn't roll off like the default graph shows; dual 18 high excursions...

Since my sub can go high- should I set the mains to higher?

The house curve doesn't look all the much different than the rolloff.

Re: using aux input and turning off mains. For some reason, my receiver freaks out when there's no load on the mains- I can't bypass them.

However,

I'll set them to small and lower the crossover and let you know if things are better, thanks!

[brucek]

my sub doesn't roll off like the default graph shows; dual 18 high excursions...

A sub rolls off at the frequency set in the receivers crossover. It really doesn't matter how high a frequency the sub itself can attain, it's limited by the crossover.

Since my sub can go high- should I set the mains to higher?

Absolutely not. Any crossover higher than 80Hz results in localization of a sub. That's undesireable. You want the mains to extend down to the 80Hz crossover and the sub limited to frequencies below that.

For some reason, my receiver freaks out when there's no load on the mains- I can't bypass them.

Could you expand on that statement. Is it not a solid state receiver?

brucek

[toecheese]

brucek wrote:

A sub rolls off at the frequency set in the receivers crossover. It really doesn't matter how high a frequency the sub itself can attain, it's limited by the crossover.

Ah; that makes more sense. With the mains added in, should it be flat(ish) after that point?

Could you expand on that statement. Is it not a solid state receiver?

Sure: if I unplug or set my main speakers to non-existent (b-speakers), the receiver immediately starts to overheat (I assume that's what happens, as I hear a fan kick on).

[brucek]

With the mains added in, should it be flat(ish) after that point?

Depends on whether you like your sub louder than the mains, but certainly the mixing of the mains and sub should be a smooth transition at the crossover.

The pic below shows an overlay of the perfect sub response overlayed with the perfect mains response and the resulting flat resulatant after they are combined in the air.

if I unplug or set my main speakers to non-existent (b-speakers), the receiver immediately starts to overheat (I assume that's what happens, as I hear a fan kick on).

Rather strange behavious for a solid state amplifier. The higher the impedance of the load, the less the current drawn from the amp. So an infinite impedance (read no speakers connected), should result in no current. Why would it overheat?

brucek

[toecheese]

Perfect explanation, Bruce! Okay, I'll have my sub concentrate on the low stuff and get REWing again.

[toecheese]

Okay- more newbish questions.

To what should the gain be set on my AMP? I have an EP2500. Right now it is right in the middle.

[brucek]

That's a balancing act depending on your own equipment situation.

Ideally, you would like the BFD input level to be as high as possible without clipping under most conditions as indicated by its VU LED's. That level is set by your receivers sub output trim adjustment.

Then, once that BFD level is set, you adjust the sub amp to the level for the correct balance between the sub and mains. Hopefully that level is attained without having to add any line amplification before the sub amp.

brucek

[toecheese]

Another newbish one: how flat a curve should I strive for? I'm using 7 of 12 filters already. I could go as far as putting the two inputs on the BFD in serial and get 24.

What's the delay of the BFD in general?

[brucek]

how flat a curve should I strive for?

No need to get it super flat. You wouldn't hear the difference. Certainly, narrow dips and peaks should be left alone.

What's the delay of the BFD in general?

About 1 msec, so you would add a foot to the actual subwoofer distance.

brucek

[Wayne A. Pflughaupt]

Another newbish one: how flat a curve should I strive for? I'm using 7 of 12 filters already.

That’s probably too many. I’m working on an article on this subject that I’ll post on this Forum – keep an eye out.

Regards,
Wayne