Do I need room EQ?

**clausdk** · **06-28-07, 04:25 AM**

Read and downloaded instructions for measuering room response. Used radio shack Model 33-4050 Analog RS Meter.

Here's the results:

bass-response-radioshack.jpg

I got an amazing response at 28 hz corrected ~ 102 db, where as the 63 hz tone is only 74 db in comparison. Thats 102-74db = 28 db difference. It's noticeble in movies as I got alot of bass really - I even measured 110 db once and this is "just" a velodyne CHT 10.

Anyways, I'm decided on getting a new / better sub, but until then I'm considering using some sort of EQ system for better bass response particularly for music.

/claus

**JimP** · **06-28-07, 07:41 AM**

In your 12' X 18' room, where is your sub located and roughly where is the primary seating position.

**mojomike** · **06-28-07, 09:02 AM**

You can certainly use eq, but it's going to take more than eq to correct that huge dip at 63hz. You should first experiment with repositioning either or both your sub and your seating positions to see what you can achieve without eq, then use eq to smooth out the rest.

**clausdk** · **06-28-07, 09:41 AM**

Here's a very primitive "paint" drawing of my viewing room.

The position it's in now delived the best low end response. When I installed it, I didn't have the radio shack sound pressure meter though. Position was done with a friend of mine and we both agreed that the corner placement added most punch, however at the expense of a very uneven response curve. At the time we used some test tones that I downloaded of the web, again without a db meter, we simply listened. The dip seemed to accur less in the spot right next to the couch (Just left of the coach). Using our ears we agreed that there was a suckout.

We spend the better part of an evening, but I really realised that it wasn't going to be as simple as I had hoped for.

The corner placement is also the most practicle I'm not sure I'm being allowed anywhere else to put it! Better half got a shock when I got the big black box delivered! - I thought it was small and cute - she didn't really agree!

room.JPG

**mojomike** · **06-28-07, 10:26 AM**

Realize that what give you the most perceived punch like the corner does not always give you the flattest frequency response. Generally, your best sound will be when you can flatten out the large peaks and nulls in the response, then get your punch back by boosting up the overall sub volume by a couple of db. You might find that you can improve your response by just moving the sub out of the corner by a foot or so.

In that area of that dip, your are losing most of an entire octave of bass. In movies and in music, there is a lot of stuff in the area between the 50's and the 80's.

**brucek** · **06-28-07, 10:33 AM**

It's a fairly large room to fill with that sub, but it sounds like you aren't going to be stepping up because of WAF.

Unless you like to punish yourself, you could speed up and increase the accuracy of the frequency response measurement process by using the free REW software. We know you have a PC and an SPL meter, so you're almost ready to go except for some cables. Give some thought to using it.

Your big problem is certainly the dip in response at ~60Hz and the peak at ~28Hz. Adding gain filters to dips like that isn't the best idea since it eats up headroom. You may not have a lot of that left to bargain with, and dips are usually stubborn. The peaks are easily removed with EQ filters. Disregarding specific levels and assuming the graph is a sub only measurement with an 80Hz crossover used, below is an example target you would shoot for, realizing that the dips are likely going to remain unless you move the sub or listening position.

bass-response-radioshack.jpg

If you're going to continue using the excel method, I would recommend modifying the spreadsheet to use a horizontal axis of 20Hz to 200Hz.....

brucek

**JimP** · **06-28-07, 10:34 AM**

Claus,

I'd venture to say that when you move across your sofa the frequency response changes quite a bit.

Given your setup, you're going to have problems regardless of using an equalizer. The question is going to have to be what can you live with and what you can't.

Ideally, move the sub to the other size of the display and move your sofa forward 4 ft and away from the side wall.

Is any of this possible?

**clausdk** · **06-28-07, 05:15 PM**

First of all, thanks for all the replies. Just signed up for this forum and already it seems very good!

Quote:

mojomike wrote:

Realize that what give you the most perceived punch like the corner does not always give you the flattest frequency response. Generally, your best sound will be when you can flatten out the large peaks and nulls in the response, then get your punch back by boosting up the overall sub volume by a couple of db. You might find that you can improve your response by just moving the sub out of the corner by a foot or so.

In that area of that dip, your are losing most of an entire octave of bass. In movies and in music, there is a lot of stuff in the area between the 50's and the 80's.

Tomorrow I'll experient moving the sub around. I'll make a new spreadsheet starting off at 20hz.

Quote:

brucek wrote:

It's a fairly large room to fill with that sub, but it sounds like you aren't going to be stepping up because of WAF.

Unless you like to punish yourself, you could speed up and increase the accuracy of the frequency response measurement process by using the free REW software. We know you have a PC and an SPL meter, so you're almost ready to go except for some cables. Give some thought to using it.

Your big problem is certainly the dip in response at ~60Hz and the peak at ~28Hz. Adding gain filters to dips like that isn't the best idea since it eats up headroom. You may not have a lot of that left to bargain with, and dips are usually stubborn. The peaks are easily removed with EQ filters. Disregarding specific levels and assuming the graph is a sub only measurement with an 80Hz crossover used, below is an example target you would shoot for, realizing that the dips are likely going to remain unless you move the sub or listening position.

If you're going to continue using the excel method, I would recommend modifying the spreadsheet to use a horizontal axis of 20Hz to 200Hz.....

brucek

I could consider a new sub for sure. One thing I havent mentioned is that I'm building a house, but not moving until 9 months or so. I havent decided on what to get for my setup in the new house, but I was possibly thinking something like Velodyne DD 15 or so. Until I move I'm reluctant to invest in the wrong sub that I cannot take with me into the new house. However as I crave for better bass I might buy it sooner rather than later and risk it.

I would definately consider using the software you mention, however I thought I needed the BFD for it as well? I could easily buy cables and such and I was very much considering the BFD. I am however a little worried it will be too complex for me.

Quote:

JimP wrote:

Claus,

I'd venture to say that when you move across your sofa the frequency response changes quite a bit.

Given your setup, you're going to have problems regardless of using an equalizer. The question is going to have to be what can you live with and what you can't.

Ideally, move the sub to the other size of the display and move your sofa forward 4 ft and away from the side wall.

Is any of this possible?

Yes, actually I've stepped all around the room, it's simply quite amazing how moving 2 feet can make for instance a 30hz sin tone disappear completely.

Moving the sub to the other side might work, however, it will be near a door and we're entering the whole WAF issue then. Moving the coach is not an option really, there's some furniture beside it. My crude drawing did not show this - sorry.

As mentioned above in my reply here, I'll try moving it around tomorrow and do some tests and see if I can find a spot with few dips and an even curve.

Thanks again for the inputs so far, really appreciate it.

/claus
DK

**salvasol** · **06-28-07, 05:31 PM**

Quote:

clausdk wrote:

.....I could consider a new sub for sure. One thing I havent mentioned is that I'm building a house, but not moving until 9 months or so. I havent decided on what to get for my setup in the new house, but I was possibly thinking something like Velodyne DD 15 or so. Until I move I'm reluctant to invest in the wrong sub that I cannot take with me into the new house. However as I crave for better bass I might buy it sooner rather than later and risk it.......

I can't give you an opinion about your original question .... but I'm curious: Are you building a dedicated HT room in your new house???? .... I think now is the right moment to plan for a nice Theater

**mojomike** · **06-28-07, 05:57 PM**

Quote:

clausdk wrote:

First of all, thanks for all the replies. Just signed up for this forum and already it seems very good!

Tomorrow I'll experient moving the sub around. I'll make a new spreadsheet starting off at 20hz.

I could consider a new sub for sure. One thing I havent mentioned is that I'm building a house, but not moving until 9 months or so. I havent decided on what to get for my setup in the new house, but I was possibly thinking something like Velodyne DD 15 or so. Until I move I'm reluctant to invest in the wrong sub that I cannot take with me into the new house. However as I crave for better bass I might buy it sooner rather than later and risk it.

I would definately consider using the software you mention, however I thought I needed the BFD for it as well? I could easily buy cables and such and I was very much considering the BFD. I am however a little worried it will be too complex for me.

Yes, actually I've stepped all around the room, it's simply quite amazing how moving 2 feet can make for instance a 30hz sin tone disappear completely.

Moving the sub to the other side might work, however, it will be near a door and we're entering the whole WAF issue then. Moving the coach is not an option really, there's some furniture beside it. My crude drawing did not show this - sorry.

As mentioned above in my reply here, I'll try moving it around tomorrow and do some tests and see if I can find a spot with few dips and an even curve.

Thanks again for the inputs so far, really appreciate it.

/claus
DK

The DD-15 you are considering is a honey of a sub and it has a built-in system for measuring and eq-ing the sub. It ain't cheap, but it's a good sub.

The REW software does not actually do the eq-ing, but it measures the frequency response and calculates the filter settings to use on the BFD to get the frequency response you want. I'd suggest starting out with some REW measurements along with some placement experimentation before eq. You may be able to get a big improvement without any eq.

Also, experiment with the phase of the sub. Somtimes the phase relationship between the sub and the mains can cause bass cancellation in the crossover region.

**clausdk** · **06-29-07, 04:04 AM**

Quote:

salvasol wrote:

I can't give you an opinion about your original question .... but I'm curious: Are you building a dedicated HT room in your new house???? .... I think now is the right moment to plan for a nice Theater

I thought about it, however two things decided against it.

1) Budget. It's our first house, so building and extra 20x30 feet home cinema wasnt really an option at this point.

2) Sometimes I like watching a comedy in a lit room. And if you have friends over, it's nice to enjoy all your equipment in a more lit up room.

However, when we build our next house, which I suspect we will some day, I will most likely be in a position to go "all out" and have a living room with decent equipment and also a dedicated HT.

/claus

**clausdk** · **06-29-07, 04:07 AM**

I'm trying to get the REW software up and running now.

Connected the PC to my reciever and it's working.

However, I dont get any input from the SPL meter - BUT when I physically tap it I can actually hear that in my speakers!

When I run the SPL calibration it does not register any input.

My question is, am I using the wrong connection?

To connect it the only cable I had was this:

1 mini jack <-> 2 RCA phono. (Connected the radio shack to the "red" phone")

/claus

**clausdk** · **06-29-07, 05:30 AM**

Wow, its working now!

However, the results are not like the ones i did manuelly at all, so thats wierd? Will work with it some more and post results here shortly.

/claus

**clausdk** · **06-29-07, 06:35 AM**

Sigh, spend all day now working this program. Got some progress atleast!

However....look:

graf 1.jpg

My sub doesnt even play 20 hz...

I did however get some earlier readins, which I deleted though, and they have some dips in them and looked a bit more realistic. I can only generate this graph at the moment though.

Going to look through the helpme files and continue working with it.

/claus

**clausdk** · **06-29-07, 07:12 AM**

I keep getting this graph when running the measurements.

I've checked the SPL cal. and it's where's it's supposed to be, really can't see what the problem is.

I even tried to set the cycle to 21.5 secs, and I can CLEARLY hear dips and peaks when running the 2-200hz sweep - clearly!

For some reason the results don't show in the program. It's funny because my very first readings actually had some dips and peaks but now all of the sudden its this wierd curve..

Argh getting pretty frustrated with it now

graf 2.jpg

**JimP** · **06-29-07, 07:26 AM**

claus,

Using the Radio Shack SPL meter, have you checked "c weighting SPL Meter" on the MicMeter tab of the "Settings" window?

**clausdk** · **06-29-07, 07:33 AM**

Yes, doubled checked.

I used the guide to set it all up. Only deviation I had to make was to use "what you hear" as input, otherwise no input was detected. Turns out only "wave" works and not microphone..? well I can do the SPL cal and it shows the db etc.

My soundcard is audigy 2 ZS.

Other noteworthy information:

PC to reciever is done via Minijack <--> coax (only have 1 mini jack <-> 2xRCA)
PC to SPL meter is done via minijack <--> 2 x RCA (Using left, as right make the SPL meter's clip)

/claus

**bobgpsr** · **06-29-07, 07:53 AM**

Claus,

I don't think you are yet really using the SPL meter output. I used to use the Audigy 2 ZS and I recall that it was tricky to get a "Line Input" (note do not use a "Mic" input) to be selected. From what you describe, instead you are using the PC synthesized "Wave" output. Seem to recall some helpful notes on getting an Audigy to work in the REW help files. I don't have the reference material handy right now -- will see what I can dig up tomorrow.

Bob

**brucek** · **06-29-07, 08:16 AM**

Quote:

Only deviation I had to make was to use "what you hear" as input,

You must use the line input. The problem you are experiencing is that the output of your soundcard is looped to the input by being in the 'monitor' mode. This is a feature to allow a a person to hear what they record. You don't want this for REW. The result is simply a graph of the inverse of your meter calibration file.

Look at the proper setup in this thread. It should help.

You're almost there.

brucek

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