Rookie at large - new subs - need advice please

[genesis471]

Hi, I was here when the website was launched, and now I am finally back. I wanted to do some room upgrades, as well as get new subs before I really got into this REW thing!
So, I am asking for possibly some ongoing advice as I start this thread. I will start with details of my room, and relivent components, photo's etc.
Gear: Denon 3805, playback via Denon 3910. I have a sinewaves disc that I downloaded from somewhere (can't remember). Hope it is acceptable or I'll have to get the much talked about Avia. Speakers: Axioms all around, but most importantly here (2) SVS PB10-NSD's which are brand new! And of course, Behringer DSP1124P (with $10 upgrade chip on the way). I downloaded the new 4.0 REW and it runs fine on my Mac. I am ready to do this, but have done some initial tests with my RS meter (manually).
So below, there are photo's of my room, and the chart of my first manual test.

I ordered bass traps from GIK ($OUCH) because I have a nasty dip (take a look), so I hope they help! I am thinking I will try them in the back corners on each side of the window. What do you think? Oh yes, room size 2000cf.

Things I am wanting to do:
Use REW 4.0 (works on my Mac but I have read that the author is working on improvements)
Setup a file on the DSP1124 for Music, and one for movies.
Get a nice curve so the bass sounds nice. The subs sound better then I have ever heard, now to get them fine tuned for the room!

Tested settings:
Crossover @ 80hz
Sub gain (on Denon) @ -5.0db
Sub gain on both subs about 1/3
Volume @ -20db

Thanks for the much needed advice forthcoming, this is a great site, with great people!

Mike

[cyberbri]

A few observations and suggestions.

First of all, is the couch against the back wall? If so, move it up at least a foot. You don't want to be up against a wall.


Second, switch the position of the subs and the speakers. Put the subs in the corners and the speakers closer to the TV. They should ideally be out on the floor, not inside the enclosed space, which will make them sound bad. But it looks like you have covers that go over the front, which probably have speaker grill cloth or something. If that's what you have to do, then so be it. But that's some pretty **** nice equipment to have the speakers inside cabinets...

Bass traps in rear corners will work. But if you could get your mains out of the cabinet, try leaving the subs in their current location or move them over a bit towards the walls, and treat those front corners with something. GIK's Tri-Traps might work there. Or DIY build something yourself to go in there.

Also, the SPL meter looks to be in front of the couch. To really get accurate results, it needs to be on the couch where your head would be. The response could be +/-10dB different between the meter's location and the position on the couch. If you need to, put a stool or something in front of the couch, extend the front leg of the tripod out, and prop it so it's in the right location and angle.

[Sonnie]

Excellent advise by Bri... especially about the speakers and subs... and do all you can to get those speakers on out into the room a little bit.

You might also consider posting about the GIK products in the Acoustics thread since the GIK guys moderate there.

Btw... welcome back!...

[genesis471]

Cyberbri, thank you for the advice. I of course have a few more questions from your advice, and comments.

1. Couch is an easy fix. Consider it done
2. Unfortunately, the cabinetry was there first (I didn't know any better 5 years ago!), and my wife wants it flush - and yes I have fronts with covers that go on.
3. The M60's sound the same out front, as they do resessed in the cabinetry (stellar I may add).
4. Bass Traps - I have ordered (2) of the tri traps. If I move the subs outward next to the walls, are you suggesting that I put tri traps behind the subs in that front corner(s)? If so, I would have to order something else that fits that height. I could put the tri traps behind the couch (up on the perch is what I had in mind), and order some others to fit in the corner behind the subs. If it does the job, it's worth the money.
5. I will do the above you suggest, ~location of bass traps, and swap the subs with the mains. Then I will re-measure, and go from there!

Thanks much for the advice!

And Sonnie, thanks, and thanks for getting me here in the first place!

Mike

[cyberbri]

Sounds good. The Tri-Traps can go behind you, and you can get something else for the inside fronts. You can even order the insulation or rock wool and custom-build something yourself that will fit in there. If nothing fits, at least you'll have the Tri-Traps in the rear corners.

[DrWho]

Just to offer another viewpoint...

The distance you sit from the rear wall isn't really going to change the reflections bouncing off the rear wall. With this in mind, you are simply going to move the fundamental boundary cancellation to a lower frequency, which ultimately is going to make the issue more audible. Even if you move forward 10 feet (which doesn't look possible in this room), you're still going to be within the Haas window. I would much sooner pin your head against the rear wall, which will result in you not hearing any difference between the direct and reflected sound. I would only recommend moving forward if it also involved adding acoustical treatment to the rear wall.
http://www.peavey.com/support/techno...ncellation.cfm

As far as the mains in the cubby hole...how far is the listening position from the speakers? I would suggest the configuration in your picture, but toe-ing in the speakers to reduce early reflections off the side wall (even if it means making the axis fo the mains cross in front of the listening position). You'll have to play around with trading HF extension at the listening position for less comb-filtering due to reflections off the side walls. But since you're sitting so far back in the room, I don't think you're going to be able to avoid early reflections...so again, acoustical treatment along the side walls would be beneficial too. (it's interesting to note that you can achieve more toe-in by moving the listening position forward....)

As far as optimal subwoofer placement - this is going to depend on the modal distribution in the room. Moving the subs as little as an inch can have a dramatic influence on the dips and peaks you see at the listening position (likewise, moving the mic a few inches can have a dramatic effect too).
http://www.ethanwiner.com/believe.html

I've gotta run, but just wanted to mention that it's a huge system of compromises and you'll have to choose your poison. Every room and application is going to be slightly different...

[cyberbri]

Sitting against a wall is a no-no for bass. Bass collects at room boundaries, so it's going to be boomy and bloated against the wall. HF is another issue, because at least you can add panels to the wall behind the couch to remedy that.


And with the speakers right next to the wall, leaving them there and only changing the toe-in angle is going to change the location of the first reflection point. If there is any reduction in bounced frequencies, it's only going to be a very small percentage. That is why I suggested moving them in closer. Speakers should be at least a few feet from the side walls because of this.

[DrWho]

Sitting against a wall is a no-no for bass. Bass collects at room boundaries, so it's going to be boomy and bloated against the wall.

Wouldn't that equate to free bass gain, thus allowing one to turn down the sub and reduce distortion? And then with a BFD you can address any frequency specific issues - but I highly doubt any frequency specific anomalies due to the size of the wavelengths and the pathlength difference of the reflection. It'll be more like the 12dB/octave rise as is typical with room gain. (in the meantime you'll also be exciting the resonances of the room less because the initial output of the sub can be turned down).

And with the speakers right next to the wall, leaving them there and only changing the toe-in angle is going to change the location of the first reflection point.

In an ideal scenario you would be able to completely avoid all early reflections from the side walls. The classic example is a speaker tucked into the corner with a true 90 degree horizontal dispersion aimed out at 45 degrees. Every speaker is different, so it doesn't work all the time. There is also the issue that every speaker is designed with different boundary gain in mind...I just wanted to point out that there is more at play than simply putting a pair of speakers in the middle of the room...the best sound systems I've heard actually have the speakers flushmounted in the wall - you can't get much closer to the wall than that

[cyberbri]

The point is to get the best response possible with placement (sub and listening position) and by addressing room issues with treatments, then use an eq as a last resort.

And if a speaker is meant to be put in a corner, it will be made known. But generally, speakers are not meant to be put in corners because of what it does to the frequency response. That being said, if the system is in a corner, tv in the middle in the corner, and the speakers along the walls, aside from the speaker-rear to wall distance, the side wall reflections are greatly reduced because of the angle the system is oriented in the room and the side reflections hitting the walls much further down the wall (I've heard a system like this, with GR Acoustics (?) A/V 2 MTMs - sounded very good). This doesn't really apply to systems against walls and putting speakers in corners of the flat wall, firing forward with a side wall parallel to where the speaker is firing. At least not at close distances (within a foot or so). Corners act like megaphones, but not in a good way because the boosting is uneven. It works better with subwoofers, because the frequency range is very limited.

It is generally accepted that moving speakers away from walls/side boundaries greatly improves the imaging, clarity, and size of the soundstage. Moving them closer to the front wall reinforces bass response, and this is something people experiment with. But moving speakers away from side walls is the general way of setting up speakers in a room. In fact, for many speakers, the suggestion is to divide the wall they are placed on into 3rds, and have the speakers at those fractions (1/3 and 2/3). Combined with any sort of speaker-specific formula outlined by the manufacturer based on the specific speaker traits.

[genesis471]

Thanks guys for your rapid response. The GIK tri-traps should be here any day.
Cyberbri, I will look into the DIY materials for behind the speakers. One step at a time.

My next step will be to correctly measure the room based on Cyberbri's previous recommendations, and then measure again once I have the first set of bass traps in place. I will post then, and go from there!

Thanks again.

Mike

[genesis471]

Finally, after a week of having that horrific flu, I am back to playing with my toys.
I have got the bass traps, but they don't seem to make a significant difference where I put them. A couple of things:
-moved couches forward one foot or so forward from the back wall
-changed location of measurement
-ran before and after with bass traps
-this is pre-BFD - no adjustments

for graph:
Pink = pre bass traps placement
Blue = Bass traps in place
Vol -20db
sub gain -5db
sub vol about 1/3

So what do you guys think? Not sure I'm getting the bang for the expensive buck out of the traps but correct me if I'm wrong.

Mike

[cyberbri]

Do you have pics of where you put the traps? Any up front, or just in the back?

You need to measure out higher, say 500hz, to see the real effect they have on the frequency response. But it's not all in the frequency response. A lot of it has to do with removing ringing and boominess, which doesn't come through in the frequency response graphs.

[brucek]

So what do you guys think?

I think you should use REW and then you'll have graphs that are more accurate. It will also give you access to impulse response etc.....

brucek

[genesis471]

cyberbri wrote:

Do you have pics of where you put the traps? Any up front, or just in the back?

Just the ones in the back for starters. I was thinking of doing the DIY type for the front.

You need to measure out higher, say 500hz, to see the real effect they have on the frequency response. But it's not all in the frequency response. A lot of it has to do with removing ringing and boominess, which doesn't come through in the frequency response graphs.

Makes sense!

Thanks, Mike

[genesis471]

brucek wrote:

I think you should use REW and then you'll have graphs that are more accurate. It will also give you access to impulse response etc.....

brucek

I actuall have tried to get it up and running on my Mac. Version 4.0 runs fine, but I have been trying to learn simply how to calibrate my meter, and my internal sound card. I think I have the meter figured out. Dunno about the sound card yet. This stuff is a bit over my head I'm afraid. I'll give it some more effort tomorrow or next weekend. Now I have a headache!

Thanks,

Mike

[Sonnie]

This stuff is a bit over my head I'm afraid.

Don't feel lonely Mike... I tried it out initially and then procrastinated forever before I finally figured it out and then realized how great it was. The procrastination was mainly due to it being what I thought was intimidating.

Seems like a few of us procrastinated on using it for one reason or another and realized how great it is once we did use it.

[genesis471]

Sonnie wrote:

Don't feel lonely Mike... I tried it out initially and then procrastinated forever before I finally figured it out and then realized how great it was. The procrastination was mainly due to it being what I thought was intimidating.

Seems like a few of us procrastinated on using it for one reason or another and realized how great it is once we did use it.

Thanks Sonnie! It can do that to you that's for sure. For now it's come down to the Mac version having issues. I have my buddies laptop that runs Windows XP I think. I just don't have an external sound device to use.

Mike