Room Frequency Response With Rives CD...Now What?

[Doug917]

I measured just my right front channel / sub this morning and was surprised how out of whack things are. I ended up with about a 33dB spread from the highest to lowest readings I took for those channels. I have been looking into EQs for a while but wasn't sure I needed it. Now, I think the results are pretty clear I need some sort of room treatment / equalization. The subs could easily be turned down to give me only a ~ 30 dB spread. The Yamaha 2500 I use will give me 7 bands of up to 30dB of adjustment with multiple Q settings, but the sub channel has no equalization. I'm not even sure where I should start and I'm looking for suggestions. My room in the basement is a rectangle (19' x 12' x 7') with the front wall and floor carpeted, paneling on the walls with sheetrock behind it and fiberglass tiles in a suspended ceiling. Any suggestions on where I should start, or what would be most beneficial to my room acoustics? Here is a link to the frequency response of the above channels:

http://www.ht.dblattman.com/RF-SubFreq.doc

There is also a picture of the front of my room at that subdomain as well. I have meant to do more with the site, but haven't had time to get to it.

Thanks!

 

[mtrycrafts]

I measured just my right front channel / sub this morning and was surprised how out of whack things are. I ended up with about a 33dB spread from the highest to lowest readings I took for those channels. I have been looking into EQs for a while but wasn't sure I needed it. Now, I think the results are pretty clear I need some sort of room treatment / equalization. The subs could easily be turned down to give me only a ~ 30 dB spread. The Yamaha 2500 I use will give me 7 bands of up to 30dB of adjustment with multiple Q settings, but the sub channel has no equalization. I'm not even sure where I should start and I'm looking for suggestions. My room in the basement is a rectangle (19' x 12' x 7') with the front wall and floor carpeted, paneling on the walls with sheetrock behind it and fiberglass tiles in a suspended ceiling. Any suggestions on where I should start, or what would be most beneficial to my room acoustics? Here is a link to the frequency response of the above channels:

http://www.ht.dblattman.com/RF-SubFreq.doc Thanks!

WOW.

You have your work cut out for you. Room treatment and EQ, 1/3 octave kind.

There is also a picture of the front of my room at that subdomain as well. I have meant to do more with the site, but haven't had time to get to it.

 

[Buckle-meister]

Doug917, have you read this?

I was in the exact same situation you now find yourself.

Your present results are too coarse, i.e. they give no indication of what is happening between your plotted points. You first need to obtain a more accurate plot of your low frequency response (makes you wonder why you bought the Rives disc eh? ) so you know exactly 'what you're dealing with'. This can be achieved by downloading ETF. The demo version is minus a few of the functions of the full (bought) version (I'd recommend it if you decide to take things a step further and look into Room Treatment), but it will still enable you to plot 2-dimensional graphs such as this.

To make the biggest inroads to acieving as flat a response as is realistically possible, I believe Room Treatment will be the way to go.

Regards

 

[Ethan Winer]

Doug,

> was surprised how out of whack things are <

It's likely even worse than that. As Mr. Buckle explained, the real response - between the frequencies you measured - probably varies even more that. You can't really fix this stuff with EQ either. With a parametric EQ, and a way to measure more accurately, you can tame the peaks somewhat. But you can't fix nulls, and they're what do the most harm and make such a large "spread" as you worded it. Nor can EQ reduce ringing, which a raw response plot doesn't even show.

> fiberglass tiles in a suspended ceiling. Any suggestions on where I should start <

Start by laying foot-thick fiberglass batts above the entire ceiling. If you don't want to cover the entire area, at least do around the perimeter. Then treat the interior of the room, focusing mainly on bass traps and the first reflection points.

--Ethan

 

[bpape]

And take the carpet down off the front wall. If you want a dead front wall, use something more broadband like 2" rigid fiberglass, acoustical cotton, rockwool, etc.

Also consider carefully your seating and speaker locations. Much good can be had from proper placement. Then tame things by treating the room as Ethan and others have suggested. Once you get the basic environment as good as you can, THEN you can tweak the last few peaks (don't try to EQ nulls) down to bring those last few problem children into line.

 

[Audioholics]

treat the interior of the room, focusing mainly on bass traps and the first reflection points.

We tend to start with subwoofer placement if that is a variable metric in your room (adding another sub and varying locations). If you are leaning towards taming bass using "traps", be sure to use bass trap systems that aren't simple friction absorbers, which don't work unless they are correctly placed (usually in a null)and large enough to sufficiently scrub the low frequency standing wave. You'll need to use some kind of resonator-based system and before you do anything, will have to find out where exactly your trouble spots (frequencies) are in the room.

It's a complex thing to address, but there is hope if you do it correctly.

 

[Buckle-meister]

As Mr. Buckle explained...

Oh no no no. Mr Buckle's my old man!

Regards

 

[bobwood]

What's REALLY going on?

Agree with Ethan. REAL TRAPS' site has a great video on it in which they show you a room response in real time at a microphone for discrete frequencies. They move it through a (relatively small) space and you can see the dips and peaks are far more than we tend to think because we look at equipment specs and think we can achieve that. For me, this just pulled everything I had experienced together. It explains why you can't easily get same gear to sound the same way from room to room (or seat to seat!)

Implied in this is the relevance of seriously taking a review as gospel because as they say, YMMV to which I add MTYT (more than you think!)

Bob Wood
http://www.GreatHomeTheater.com
http://www.woodsgoods2.blogspot.com

 

[Glenn Kuras]

Doug,

If it makes you feel any better I have seen rooms that are much worse and have been fixed. I would tend to think that if you place 8 to 10 bass traps in the room you will see your graph change for the better. Just make sure you focus on all corners.

Glenn
GIK Acoustics
www.gikacoustics.com

 

[Doug917]

Thanks for all your replies. I have tried moving subs (only by ear though) and it didn't really seem to help. If I stand anywhere in the room and clap my hands, I get a "tinge" echoing in the room. Also, any time I balance my channel leves I always hear (kaaaaaaaa, kssssssss, koooooo, etc) meaning althought the speakers are from the same manufacturer across the front (same model in some cases) they all sound differently, which has to be attributed to the room. I am looking at the Auralex foam treatments to put in the tri-corners and to kill the first order reflections from the front speakers. The only bad thing with this is that I have DVD racks built into one of my side walls (included pics in the post) and don't know how I can make the panels look very good...I'm open to any suggestions! Also, with my bipolar surround and surround back speakers do I want to kill any reflections from these as I know normally you thrive on the reflections from speakers like these? If I use a mirror on the ceiling, I can see the first order reflections in a straight line across the ceiling, which makes since as the speakers are in a striaght line across the floor. I am also looking at a few EQs from Rane and Audio Control to smooth out what the treatments don't grab. I figure as opposed to upgrading another component (speakers, etc) I would like to start with the room and don't mind spending ~$1000 (for both EQ and treatments) if it will make a large difference in the sound.

 

[Buckle-meister]

...any time I balance my channel levles I always hear (kaaaaaaaa, kssssssss, koooooo, etc) meaning althought the speakers are from the same manufacturer across the front (same model in some cases) they all sound differently, which has to be attributed to the room.

I'm not so sure. My own speakers are matched, but I too hear the difference you speak of. Where are you listening to them from when you are calibrating your system? If you are skew to all three speakers, it might explain why they all sound different.

Can't say for sure though...

don't know how I can make the panels look very good...I'm open to any suggestions!

After going through the following process, look at what Sploo () made.

Regards

 

[Doug917]

Buckle-meister,

I am sitting in the sweet spot in my listening position and calibrating levels when I hear the differences. The center sits lower than my ears and is pointed up directly at my ears. The fronts and presence channels are "toed-in" right at my position and the presence are pointed at ear level, while the fronts are a little lower than ear level. The surround/surround rear are all mounted at the same height ~5.5ft off the floor above ear level and at equal distances from the walls (I included a pic of the rear that show all but one of the surround speakers). Thanks for the links. I do not have an industrial workshop , so I am looking into something already made at a reasonable price I can permanently affix to the walls/ceiling which has brought me to the auralex. I am open to other suggestions.

Thanks!

 

[Ethan Winer]

Doug,

> don't mind spending ~$1000 (for both EQ and treatments) <

For that budget forget an EQ and just focus on broadband absorbers that extend low enough to also serve as bass traps. Perhaps I'm prejudiced, but I'm not convinced that the foam you mentioned is up to the task.

--Ethan

 

[Buckle-meister]

...I am looking into something already made at a reasonable price I can permanently affix to the walls/ceiling which has brought me to the auralex. I am open to other suggestions.

I am considering picking [a Z9]...up so I can run 9.1...

I appear to have quite a bit in common with you; I have the Z9!

It'll be a very difficult decision I know, because the Z9 is a real beauty, but if you spent the same as the Z9 on Room Treatment instead, I'm fairly confident you'd actually (as opposed to psycologically) hear a bigger difference.

The choice as they say, is yours!

Regards

 

[Glenn Kuras]

Doug,

> don't mind spending ~$1000 (for both EQ and treatments) <

For that budget forget an EQ and just focus on broadband absorbers that extend low enough to also serve as bass traps. Perhaps I'm prejudiced, but I'm not convinced that the foam you mentioned is up to the task.

--Ethan

For a $1000.00 you should be able to treat your whole room and still have a few bucks left to have a couple beers!!


Glenn
GIK Acoustics
www.gikacoustics.com

 

[Doug917]

Today I realized I majorly goofed on equalization. I chose "Front" which leaves the front channels unequalized. I loaded the 2500 editor with a laptop I picked up and it is pretty awesome software. The only downside is it is quite slow uploading and downloading. I ran YPAO again for the EQ option only and set it for "Natural" this time. The same right front channel I measured last time was much better above 80Hz. The lower frequencies still need adjusting as YPAO does nothing below 62.5Hz. I am going to set the crossover down to 60Hz, as all my speakers can easily handle it and rerun YPAO. I'm still not as flat with response as I would like to be, but I am much closer now. Channels sound much closer to each other now.

 

[Buckle-meister]

I loaded the 2500 editor with a laptop I picked up and it is pretty awesome software.

What is this? Is it the software that Technicians/Installers might use, connected through the receiver's RS232 port, to see the settings the receiver makes during YPAO. If so, the all important question is...can I get it for the Z9!!!?

Regards

 

[Doug917]

Ask and you shall receiver:

http://www.yamaha.com/yec/dealers/dealer_download.htm

This ought to keep you busy for a while. You will need to pick up a null modem and straight cable if you don't have one.

Peace!

 

[Buckle-meister]

This ought to keep you busy for a while. You will need to pick up a null modem and straight cable if you don't have one.

Thanks mate. Remember that I actually have the DSP-Z9 A/V Amp as opposed to the RX-Z9 Receiver, but hopefully it will still be ok.

What is a 'null' modem?

Regards

 

[Doug917]

Meister,

A null modem is a connector that has pins 2 & 3 and 7 & 8 crossed over so when something is transmitted on one end, the other end can receive it. I would also download the Z9 instructions at the same site as above as they cover the pin connections as well. What are the differences between your Z9 and the ones here (USA)?