Stretch's room EQ efforts

**Stretch** · **05-07-08, 02:02 PM**

Hello all. Having spent a few evenings futzing with REW and getting the basics figured out on my Mac*, I've finally got to the point of being able to take some measurements. What a great tool this is! Thank you John for the software and thank you to the expert users like Bruce and Wayne for all the support and advice.

Here's my first graph, with a few caveats. The sub used was an old 12" JBL that our home's previous owner stashed outside under the back porch to go with some outdoor speakers around the pool. It's roughed it through a good few freezing Boston winters and frankly I'm surprised it still works at all! It'll be replaced by an Epik Castle in a week or so, I hope. (Ship it! Ship it! Ship it!) Location was the usual starting point, up front between the left main and center channel.

Much appreciate any thoughts from the gurus about what this may indicate about the potential of that position -- which I'm really, really hoping I can get away with. (Don't much like the look of that null at 43Hz, though.) I've got a BFD still sitting in the box, but am not going to bother to do any EQing until the decent sub gets here. (Ship it! Ship it! Ship it!)

(* I'll be happy to write up a cheat sheet for other future Mac-using noobs, if that'd be useful? Could either put it up at the top here, or in a thread of it's own.)

Thanks.

**brucek** · **05-07-08, 06:24 PM**

Quote:

Don't much like the look of that null at 43Hz, though

The null at 43Hz ain't that bad really, but the two peaks at 60Hz and 80Hz could use some filtering with the BFD. You'll find peaks like that will cause you to turn down the level of the bass since you hear the peaks louder than anything else. Once you filter them it allows you to turn up the wholesale level and the very low frequencies can now be heard....

brucek

**atledreier** · **05-08-08, 02:54 AM**

Not to hijack the thread, but how do you effectively EQ a 'plateau' like Stretch has from 80-110Hz? I have a similar problem. Not defined peaks like the 60Hz one, but continuous.

**brucek** · **05-08-08, 05:34 AM**

A couple of filters would probably do it fairly easily. Since REW allows you to "see what you get", it's very quick. Remember that it isn't important to have the result ruler flat..

brucek

**atledreier** · **05-08-08, 06:47 AM**

I know I don't need it ruler flat. I just wanted to try it to see how I liked it. I didn't.

**Stretch** · **05-08-08, 09:29 AM**

No worries about hijacking. I was wondering that myself.

Here's my first theoretical EQ effort, taking some of Wayne's advice and lowering the target level to 73dB to try and deal with the low-40s null, which I assume is a room mode. I moved the sub around a bit, including into both corners, and didn't see any change in that area. I didn't bother filtering much above 100Hz, as I'll likely be crossing over well below that.

With a bit more time for tweaking, I reckon much the same response could be had with a couple less filters. But I gotta go earn a crust. Stupid real life.

**atledreier** · **05-08-08, 11:26 AM**

That's one of those responses I call ruler flat.

I'd kill for a natural response like that..

Could you please post your filters as well?

**Stretch** · **05-08-08, 01:05 PM**

Quote:

atledreier wrote:

That's one of those responses I call ruler flat.

I'd kill for a natural response like that..

Could you please post your filters as well?

Would happily do so, except I just realized you have to save filters and measurements separately and ... I didn't.

Live and learn.

Here's a quick and dirty do-over.

**atledreier** · **05-08-08, 01:25 PM**

I just simulated a new run from my original un-E'ed measurements... Looks promising. I've also added a hard knee house curve, +6dB at 20Hz. Match the inroom response better than a flat target anyway. The dip down low is location related, I get it ruler flat to 40 in another position, but then the 40-60 area is messed up. I'd rather sacrifice a little down low. It's not like I'm lacking much down there anyway...

**Stretch** · **05-08-08, 01:49 PM**

Quote:

atledreier wrote:

It's not like I'm lacking much down there anyway...

I bet you say that to all the girls!

Looks good to me. I need a decent sub. Then I need another one to stack on top of it.

**atledreier** · **05-09-08, 03:22 AM**

Hehe! I'd like to see you stack mine!

They are 170cm tall.. Each...

**Stretch** · **05-10-08, 04:54 PM**

Ran and measured the Audyssey calibration in my pre-pro today just out of interest. Red is after, obviously.

Need to do some more reading on Audyssey/manual EQ interaction. Am I correct in thinking the general consensus is: 1)EQ sub(s) flat 2) Run Audyssey 3) Re-EQ to house curve if desired?

**brucek** · **05-10-08, 05:19 PM**

Quote:

Am I correct in thinking the general consensus is: 1)EQ sub(s) flat 2) Run Audyssey 3) Re-EQ to house curve if desired?

That's certainly not how I would do it.

I would run the Audyssey first and let it take its best shot.

Then I would clean up with EQ....

brucek

**atledreier** · **05-11-08, 02:03 AM**

I agree. Audyssey first, then EQ.

**3ll3d00d** · **05-14-08, 08:04 AM**

Quote:

brucek wrote:

That's certainly not how I would do it.

I would run the Audyssey first and let it take its best shot.

Then I would clean up with EQ....

brucek

I don't think you can make a blanket statement like that as it depends on what your raw response is and what your goals are. IMO there are 2 good reasons to run the EQ first (both of which apply in my case).

1) If you have some particularly savage peaks then you will almost certainly get a better response from audyssey if you tame them with an external EQ device first as Audyssey has limited filter resolution and it can only cut so far. Therefore it makes perfect sense to remove such peaks freeing up it's horsepower to focus on other issues more effectively.
2) if you want to implement a house curve; Audyssey is designed to deliver a reference curve and there is nothing you can do about it. If you EQ flat --> audyssey --> EQ house curve then you can have audyssey do it's thing as well as designing your own house curve.

I also find that audyssey can do some induce some odd shapes to the response low down, I've seen some curious cuts around 18-20Hz that exacerbate the hump in the response around the tuning frequency. By EQing flat you can avoid this sort of issue.

What I would say is that you need to understand your room response before you do this, you can't just take 1 reading and then EQ against it. Instead you ideally need to take readings from the same positions as you give to audyssey then EQ the averaged result. In practice you may find you don't need to take all 8 readings, so in my case it is sufficient to take readings across 3 positions & I only use the BFD below about 60Hz as the room interactions become more complex above that point and I'm wondering into mains territory which I leave to audyssey. Whereas <60Hz my response is dominated by a slight hump around the tuning frequency (12Hz), a big big peak at the room length mode (which the sofa sits across so response is v v similar in all 3 seating positions) at 37Hz and a variety of responses at the room width mode around 50-55Hz. In reality I therefore EQ flat through a combination of a higher subsonic filter + BFD cuts, then run audyssey (and it demonstrates that it understood my intentions by performing measurable changes about ~55Hz or so) and then re-EQing (slightly lower subsonic filter + slightly smaller cuts).

Cheers
Matt

**Stretch** · **06-03-08, 03:02 PM**

We're back in business -- the new sub just got heaved off the truck. Spot the difference!

Blue -- JBL Powersub 12
Red -- Epik Castle

Let the tweaking begin.

**atledreier** · **06-03-08, 03:09 PM**

Wicked!

Although just a tad hot, maybe?

**Stretch** · **06-03-08, 04:44 PM**

Quote:

atledreier wrote:

Although just a tad hot, maybe?

Perhaps a smidgen.

**Stretch** · **06-03-08, 07:46 PM**

OK, here are the uncorrected responses at my three seating positions (main is the gold trace) together with the average (purple trace). Calibrated to 75dB.

Given the close correspondence up to about 30Hz, I'm leaning toward cutting here first with the BFD and then letting Audyssey sort out the seat-to-seat variation in the 40Hz to 60Hz region, since that's supposed to be one of its strengths.

What do you reckon?

**brucek** · **06-03-08, 08:17 PM**

Could you show one of the responses (gold), except put the target line on, at the crossover you are using?

brucek

**Stretch** · **06-03-08, 09:30 PM**

Sure. I'm crossing over the mains at 70Hz.

**brucek** · **06-03-08, 09:47 PM**

I wonder if there's a better position for the sub to help reduce that rather large peak. It's quite a large cut.

brucek

**Stretch** · **06-03-08, 09:47 PM**

And here (because I have absolutely no patience) is the averaged response after running Audyssey MultEQ XT at 8 positions across the seating area.

Sounds pretty good, I have to say. And if you were looking at an 80dB target level...

Add the BFD and one boost at 46Hz? The sub has plenty of headroom.

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