# First room measurement..advice needed from newby



## Daniel0012 (Sep 30, 2010)

Hello,

finally managed to take some first measurements, enclosed my results, using REW and the radioshack SPL, 
with dolby sorround giving the sweep on all speakers









same volume settings etc. with thx









and the waterfall










would be greatful for tips which ones (peak at 30hz, low at 35 Hz) to treat, would a helmholtz do the job, do they work for lows at well ?
How do you measure a typical cinema setup, using fronts/sub only or using all speakers? Quite suprised I get so different results on the bass level switching between dolby and thx...

Regards

Daniel


----------



## bpape (Sep 14, 2006)

Not perfect but I've seen a lot worse.

30 and 35Hz are going to be very difficult to deal with via treatment. I'd suggest working with mic position to see if you can help with small seating position changes. If you can't, or another problem them pops up, I'd consider using the RTA function of REW to play with sub position to try to smooth it out.

Bryan


----------



## Daniel0012 (Sep 30, 2010)

Thanks Brian,:T
good to get some expert judgement on how to focus before building lots of resonators and stuff, will try playing around with sub position first, any hints where a good position might be? Between the fronts wont work due to size and the the thing is heavy ;-) Will a sub equalizer/BFD do a good job, they seem a comparable cheap solution :scratch: ? 

Regards

View attachment Kino.pdf


----------



## bpape (Sep 14, 2006)

I'd play with seating position first if possible. 

Experimentation is best for sub positioning and you can use the RTA function in REW to help you.

EQ may be needed but only after exhausting seating and sub positioning. 35hz and down is very hard to do even with tuned absorbers as many times, when tuned that low, they can cause their own problems.

I'd also recommend doubling or tripling the thickness of the absorbers on the rear wall behind your seating. 5cm isn't enough to approach the deeper bass. Its' still not going to go to 35hz fully but it may help a bit and will definitely help with other things.

Bryan


----------



## MatrixDweller (Jul 24, 2007)

I found that when I moved my sub around it changed where the dips were, although they still existed. So you might be able to move your sub into a position so that the dip occurs at a lower frequency that is not as audible or to a higher frequency where it is more treatable.

Most people tend to recommend super chunks in corners and as thick as possible. That will help with the waterfall graph's representation of room decay and might alleviate some of the frequency anomalies. The end result is to minimize the room's colorization of the sound. Of course your speakers and/or AVR will have their own colorization. You could add in EQ to tackle things once you've made some improvements to the room.


----------



## marty1 (Jun 29, 2010)

I have spent a lot of time trying to get as flatter response as possible, I have managed to get a fairly good response from subwoofer, the upper frequencies I am yet to tackle with room treatment.

I would advise picking where you would like to sit first, ideally away from walls and the centre of the room. Put the mic there and measure the sub in every possible position with any eq on amp or sub switched off, unplug the speakers and measure just the subs response alone in each position. Set the sweep from 10hz-200hz, 512k.

Compare your results and look for the best result, as close to flat as possible. Once you have that position sorted out start adjusting subs phase and peq (if available) to tweak any peaks, dips in the lower hz levels are pretty much only dealt with by sub placement so just try and bring the peaks down. :T

Regards
Marty

P.S. When you Measure speakers aswell set amp to stereo not dolby surround as it overcomplicates measurements, do not worry about rears just try and get 2 front mains and sub perfected first


----------



## lesmor (Dec 30, 2009)

As a novice I concentrated too much on the sub and graphs in one seating position
Perhaps there should be a room/seating/ sub setup guide . as I too found you should try and find the flattest seating position.
I positioned sub as best I could , then I run a line down the centre lenght of the room taking readings with the meter up and down the line until I found the best/ flattest seating position.
You could then try and fine tune by moving sub slightly . I didnt need to.

As always every room will be different but there has to be a better way then lugging subs around doing your back in.
Far easier to move the meter


----------



## Daniel0012 (Sep 30, 2010)

Thanks guys, this has been tremendously helpful so far, especially the hint just connecting the sw and runnung up 200hz helped a lot. 

problem is, the sw ist just fine were it was, assuming i will run it up to 80 hz anyway (few other otions to place it anyway, bit too bulky)









problem are the fronts, these seem to drive most resonances, and there's just no other way to place them









well, altoghether looks a lot better then before playing a bit around with positions and sw settings, plus some thicker panels for the back already ordered but haven't arrived yet, I hope that will do the yob, what do you think










txs again 

Daniel


btw.: great fun, playing around with REW, still the impact of running thx, dolby etc. keeps me quite frustrated, all of them at least on my receiver don't seem to change things for better


----------



## marty1 (Jun 29, 2010)

Try using 1/3 octave smoothing and click on measured at the top of rew graph, I think it makes the response a bit clearer.

Again measure with your amps sound settings set to stereo, not surround, with any eq on your amp or your sub switched off.

It is important you get everything correctly balanced before adding any eq.

Do a measurement for sub and speakers combined, phase on sub set at 0, then move phase dial 1 step measure again then move it again and again until the dial has done a complete 360, then compare the results, that dip around 50hz you have is more than likely a phase issue so this again will allow you to determine the best position for the phase dial.

Just out of curiousity, do you have your amps crossover set at 80hz, the subs crossover fully open and speakers set to small?


----------



## Daniel0012 (Sep 30, 2010)

Thanks Marty for taking care of this 

enclosed the smoothed graph










will try that, haven't changed the phase yet, will try if that further improves.

I have the SW open for the measurement only since I do all the digital processing on the BD-Player and run the Amplifier pure analog via Ext-in when watching movies (I don't use the amplifiers digital section) In my normal setup I have the fronts on large (The Logans go down well w´below 30 HZ) and the other speakers on small, SW crossover at 80Hz. Thus the 100hz distortin should dissapear, but cant really measure that. 

Can you use REW for pure recording as well without using it as a signal? then I could try the setup with a test-dvd I have at hands using the BD-Player.

BTW, I will try not to use any EQ, I am more of an analog guy, believe in good analag equipment, even if its old stuff. So I really would like to smooth this out with room acoustics and placement, still some free space on the wall to add more foam ;-)

If the drop at 100hz stays, do you think a helmholtz or plate resonator would be an option?

Txs again

Daniel


----------



## marty1 (Jun 29, 2010)

Daniel0012 said:


> Thanks Marty for taking care of this
> 
> No probs :T
> 
> ...


You would probably know more than me about the accoustic treatments to deal with the mid to high frequencies as I said I am a novice in that area at the moment.

I am not sure you can use rew for pure recording, post that question on the rew forum.

Regardless of your logans being capable of the lows you are always better off setting the amps crossover to 80hz, 60hz at the very lowest, the low frequencies put a strain on your speakers drivers, you will find by allowing your sub to deal with the lower end your mains will become a lot clearer and gain breathing space to deal with the mids-highs a lot better. I would only ever set any speaker to large or full range if I didn't have a sub.

Your response is near perfect, which concerns me, if you have everything set on rew correctly then you should be in heaven with that response. have you followed the setup proceedure for rew in terms of calibrating the soundcard and spl meter?

Regards
Marty


----------



## Moonfly (Aug 1, 2008)

marty1 said:


> Your response is near perfect, which concerns me, if you have everything set on rew correctly then you should be in heaven with that response. have you followed the setup proceedure for rew in terms of calibrating the soundcard and spl meter?
> 
> Regards
> Marty


The graph is showing the speakers as well as the sub. With smoothing on its not uncommon for speakers to look quite flat, they are designed to give a good flat response, and the frequencies arent affected by the room dimensions the same way sub bass is as the wavelengths are shorter than the rooms dimension. The effects the room has on higher frequencies is more to do with things like echo, which can be addressed with room acoustics materials like softer furnishings etc.

The response looks good, but REW's use is best focused on the sub as you cant do much about tiny (by which I mean very narrow spikes and dips) variance's in the higher frequency range, much less actually hear them. To better see the subs response, use the standard graph limits, 45 - 105db and 10-200 hz. This will let you see the effect your room is having on your subs response, and will let you see the area where the speakers and sub crossover. Above 200 hz, there is little you can do from an eq POV beyond the usual trim levels and distance (phase), and thats where room acoustics starts to come into its own. Your ears are the best tool in that area above REW IMHO.


----------



## Daniel0012 (Sep 30, 2010)

*Question for Marty*

marty,

thanks for your advice, very helpful, just one think I don't get, why I shld set my fronts on small.
The Logans have a compeltly seperated woofer for the lows, and I am not evn using the power amp section of my ampliefier but an extra parasound amplifier for these. I don't really get why they should sound better not going into low frequencies, txs for clarification

Daniel


----------



## bpape (Sep 14, 2006)

There are 2 reasons.

1. The best place for imaging and screen lock is rarely the best place for smoothest bass response.

2. If you don't cut them off, then you'll have 3 speaker reproducing the lowest frequencies and likely will have a lot of peaks and dips caused by that.

Bryan


----------



## marty1 (Jun 29, 2010)

bpape said:


> There are 2 reasons.
> 
> 1. The best place for imaging and screen lock is rarely the best place for smoothest bass response.
> 
> ...


On top of that Subwoofers are specifically designed to deal with the low frequencies, the speaker just cannot compete with the sub in the low frequencies so let it do its job :T


----------



## Moonfly (Aug 1, 2008)

What the size of the bass drivers in your speakers, because I'll bet they are smaller than your sub(s). They will probably do a pretty good job, and dual subs placed with your front 2 speakers usually works pretty well. However, when you add your sub into the mix, running those in speakers sub will likely create more issues than it solves. The bass the independent sub produces will be far superior to that any speaker subs can produce, so your speakers added input will at some point start to colour the cleaner sound of the sub, particularly at lower HT frequencies. Add to that the fact your speakers will likely end up with phase issues in relation to the sub when large crossover fields are present, and you usually end up with the conclusion that its not worth it.

You could run that setup, but you would likely need to lower the crossover on your sub so the interaction between sub and speakers stays positive. You may or may not prefer the sound of that. For music its not unlikely you will prefer it (I usually find speakers sound more musical that way IME), but for movies the chances are it will sound worse. Only you can decide on that really, but most people stick with keeping the crossovers at the typical 80hz, especially if the complexities of unusual setups are not something your confident with.


----------

