Author Topic: REW questions  (Read 23767 times)

Online whitesox

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REW questions
« on: January 16, 2017, 09:55 »
What is REW real time measurement ? Hmmm... Initially I thought it is too complicated to learn for my old brain that was why I ignored it but bcoz
I was poisoned heavily after visited bro Roni... Heard rumbling effects of his Rythmik+KK subwoofers therefore I decided to give a try and
begin my journey with.
I am so lucky that bro Roni helped me to tune my 3 subwoofers. We have a good discussion !
(He told me that bro Jag is his si-fu and helped him too. He learned a lot from bro Jag)

Used REW to locate my best locations, manipulate room gain and how to integrate between subwoofers and Centre Speakers.
Surprised me that my good location end up become my worse location to place one subwoofer there.
One subwoofer needs to turn 180 deg for phase...  OMG I never expect that before :o
Tweak here and there for phase, distance and Xover

I used Fantastic-4 (2015 movie) to test.
So now, I have new experience to enjoy my movie (don't know how many layers of bass..haahaa but surely
my sofa vibrate longer than usual without bass shakers).
Because of this experience that's why I would like to encourage HT lover to learn this powerful tool.
 ;D
Watching movie without good bass (rumble experience) something like eat good food but without salt ...

After Audy calibration was being carried out, I still don't understand why I must set same reading (-8) in the AVR for sub-1 and sub-2
despite location of sub-1 is closer than sub-2 towards MLP? I thought nearest sub will get trim/cut more as what Audy gave.
(note: all knobs at sub are pointed to the same level 78db)
 ???
« Last Edit: January 16, 2017, 15:43 by whitesox »

Offline ronildoq

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Re: REW questions
« Reply #1 on: January 16, 2017, 22:19 »
Hi Bro,
Had a great sweaty time calibrating the system, but was well worth it.

We have successfully gain matched all 3 subs, so now all 3 subs are working equally hard. You dont have to worry about any of the subs running out of steam, all will run out of steam at the same time. But you have tons of headroom. So that is fine. All you need to do is adj the AVR trim equally for subs 1 and 2 for syokness SPL level.

Offline ronildoq

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Re: REW questions
« Reply #2 on: January 16, 2017, 22:42 »
Visited bro whitesox yesterday and helped our fellow member with his set up. He had 3 similar svs SB12 subs but wasnt happy with the bass. Thank god we have REW to thank for that. We ran through some measurement and sweeps and this is his original A+B+C subs response. His MLP was at 2/3 back wall, but I was shocked, as all 3 subs were measuring as follows.



We used REW's RTA feature to find the best location for the subs and then Phase aligned all 3 subs, so here is the response after our exercise.



So much better! turns out the subs were not phased aligned and was co located at the worst place. Ideally if you have 3 subs, try to spread them out, that is the best!

Its very difficult to find subs best location without REW, crawling helps but REW is powerful,accurate and free. We all love our FREE stuff!!
Listening to phase align subs is for pros, after tweaking repeatedly over time, you will be able to phase align the subs without REW. But before that, your ears need to be trained by measuring and seeing the response. Once you have that experience, it becomes easier.

You could see why bro whitesox was not enjoying his bass despite having 3 subs. Hopefully he is now able to enjoy his system ;)

Offline ronildoq

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Re: REW questions
« Reply #3 on: January 16, 2017, 23:20 »
Bro has a very nice B&W centre speaker, very powerful centre. Nice.
But after audyssey, you can see the response of the C+Subs crossed at 60,70,80



Since we know the subs are flat up to 100hz, and there is dip in the crossover region after measuring C+subs, a way to solve this is to use the AVR's sub distance to tweak by bringing up the dip in applying equal distance increments to both subs. or reduce in equaly amounts for both subs. we went with steps of 30cm. It was already late and we went with the following distance between sub 1 & 2



That brought up the dip a little, but it was not the best. I wish i had more time to fine tune to perfection. See the response above of the C+Subs after distance tweak.

Hopefully you are now able to do your own measurement and compare the results. There are a lot of other features on REW, these are just the basic stuff and you can always use this when you upgrade your subs to a more powerful sub! You will definitely enjoy since your room is very good and you have no room modes. Very lucky !

Online whitesox

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Re: REW questions
« Reply #4 on: January 17, 2017, 08:56 »
Hi Bro,
Had a great sweaty time calibrating the system, but was well worth it.

We have successfully gain matched all 3 subs, so now all 3 subs are working equally hard. You dont have to worry about any of the subs running out of steam, all will run out of steam at the same time. But you have tons of headroom. So that is fine. All you need to do is adj the AVR trim equally for subs 1 and 2 for syokness SPL level.

haaahaa... yeah it was so hot... sweat, sticky and smelly...  ;D

Really sorry, I have no choice must turned OFF AC otherwise cold air blowing to your mic umik-1 and affecting all measurements.
We should 'bottom up' to celebrate this with beer after successfully improve my 3 subwoofers.
Thank you so much beyond words !
Let's arrange for a good time  ;D
« Last Edit: January 17, 2017, 13:11 by whitesox »

Online whitesox

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Re: REW questions
« Reply #5 on: January 17, 2017, 09:01 »

Since we know the subs are flat up to 100hz, and there is dip in the crossover region after measuring C+subs, a way to solve this is to use the AVR's sub distance to tweak by bringing up the dip in applying equal distance increments to both subs. or reduce in equaly amounts for both subs. we went with steps of 30cm. It was already late and we went with the following distance between sub 1 & 2



That brought up the dip a little, but it was not the best. I wish i had more time to fine tune to perfection. See the response above of the C+Subs after distance tweak.
....

Current crossover applied at 80hz for centre speaker so since there is dip at (70-90)hz so do you think it will get
better response if I can change (down it) to 70hz ? Audy gave 40hz value for my centre.
My centre spk has rear port, 7cm placed away from wall.. do I need to move forward in order to get more space to 'breath' then will get room gain? will it help?
Hear your opinion (Jag, Sevenz need your help by giving opinion also pls)
 :)
« Last Edit: January 17, 2017, 12:57 by whitesox »

Offline ronildoq

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Re: REW questions
« Reply #6 on: January 17, 2017, 14:21 »
bro, you can try 70 or 60hz also, then tweak the distance. But you will need a Umik 1 measurement mic to do it. A lot of times, we just follow the audy recommended crossover of 80hz. Audy doesnt set the crossover, the crossover is set by the AVR. And in this case, your centre can go up to 40hz flat, no downward slope. Hence you can play around with 60,70,80 hz. All will work. The dip you are seeing is after integrating C+subs, it is common to see a dip in the crossover region.  As far as your LFE channel goes, you have no dips till 100hz. So audy got the distance set correctly for both your subs. I believe no one can answer your question, it is only through measurement you will know this.

I tried 60 & 90hz, i went with 60hz in the end. 60hz was very pleasant especially when it came to music (i watch a lot of animation). So the midbass is not over bloated. When you cross at 90hz, you will be sending <90hz information from the centre chanel to the subs. That wasn't as nice for me. So its down to preference

Get a UMIK -1 mic, its not expensive. then you can slowly take your time measure and tweak to nirvana. It will also help u when you upgrade your AVR or subs etc. Because you have all the power to measure and implement whats best for your set up with a simple mic.

Offline deadrick

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Re: REW questions
« Reply #7 on: January 18, 2017, 16:19 »
hi roni and whitesox, like to understand why changing the sub distance will affect the dips? is it a tweak for multi sub or can tweak for single sub too?

Offline ronildoq

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Re: REW questions
« Reply #8 on: January 18, 2017, 18:08 »
hi roni and whitesox, like to understand why changing the sub distance will affect the dips? is it a tweak for multi sub or can tweak for single sub too?

Hi Deadrick,
Changing the subs distance = changing the delay. here is a simple explanation by Rythmik.

Quote:
How to adjust phase with a home theatre receiver

The simple method is to compensate by changing the speaker distance setting on your receiver. Bass management in HT receivers has a speaker distance adjustment which process the signal on digital domain. If one puts distance of the sub x feet further away than its physical distance relative to other speakers, the HT receiver will put out the signal to the sub x/1000 sec before it puts out signals to other channels. That essentially puts a negative delay on the sub which can be used to reduces the "phase lag" on the sub and therefore reduces the phase difference between the sub and the front speakers.
This trick enables us to use the speaker distance as a tool for phase adjustment between subwoofer and front speakers. Since it is a constant delay adjustment, the phase adjustment is not fixed for all frequencies, instead it is proportional to frequency. That does not affect its effectiveness as our objective is to get correct phase alignment at the crossover frequency.

Unquote

The reason you are seeing the dip after measuring the Centre Channel with subs is because when you set the Mains Crossover at 80hz after audy, the mains will cut off at 80hz and start sending all information below that to the sub. Because of this, a lot of times there is cancellation at the crossover region. and the way to solve this is to use the distance to tweak for integration of mains and subs. That is also another reason why i dont like to High Pass one sub and Low pass the other, it will always somehow screw up the response because we are not taking advantage of the power of dual subs to even out the response. Also I prefer not to set it beyond 90hz as the subs will start to localise, which is not pleasant.

Most just set it at 80hz and assume thats it. It is very important to make sure the mains integrate well with the subs, that makes or break a system as a whole. The only way you can check if this is done correctly is by using a Mic to measure. There is no way you can tell at which crossover there is a dip at which freq if you do not have the measurement tool. You would just have to stick to 80hz and hope for the best.

Mic is not exp, USD75, great tool! Learning REW is a little bit of a challenge, lotsa reading to do. But its never too late to start, highly encouraged

Offline sevenz

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Re: REW questions
« Reply #9 on: January 19, 2017, 18:49 »
do you think it will get better response if I can change (down it) to 70hz ?

My centre spk has rear port, 7cm placed away from wall.. do I need to move forward in order to get more space to 'breath' then will get room gain? will it help?
Hear your opinion (Jag, Sevenz need your help by giving opinion also pls)
 :)

7cm from wall for rear ported speaker IMO is too near and likely affect the Sq. Suggest at least 1-2 feet if u can.

The xover,  u need to measure the FR and do trial and error by changing freq and dist Bro. No bao chiak straight forward solution.

Agreed w what ronil suggested, invest in a mic and learn rew.
« Last Edit: January 20, 2017, 18:55 by sevenz »

Offline Yubaba

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Re: REW questions
« Reply #10 on: January 19, 2017, 19:00 »
No investment, no return


I have gone down to the path of Dynaudio and it has dominate my destiny

Offline joagib

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Re: REW questions
« Reply #11 on: January 19, 2017, 19:10 »
7cm from wall for rear ported speaker IMO is too near and likely affect the Sq.

The xover,  u need to measure the FR and do trial and error by changing freq and dist Bro. No bao chiak straight forward solution.

Agreed w what ronil suggested, invest in a mic and learn rew.

Wah..bro!
You very Pro leh...Hopefully you can help me out for my next setup..

Offline sevenz

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Re: REW questions
« Reply #12 on: January 19, 2017, 21:03 »
Hopefully you can help me out for my next setup..

Offline ronildoq

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Re: REW questions
« Reply #13 on: January 20, 2017, 09:08 »
7cm from wall for rear ported speaker IMO is too near and likely affect the Sq.

The xover,  u need to measure the FR and do trial and error by changing freq and dist Bro. No bao chiak straight forward solution.

Agreed w what ronil suggested, invest in a mic and learn rew.

Bro, u wouldn't want any "boundary gain" for your Centres, what u want is clarity. Bass is handled by subs, If ur back wall is reflective, u want your Centres away from the wall for better clarity, 7cm is too near to wall as Sevenz mentioned. Same for your mains.

Having said that, move your Centres 3 cm forward will still not solve the dip in the crossover region, neither will placing treatment at the wall. U can experiment with phase tweaking the mid wall subs, we have seen that 2 subs are good enough to smoothen the response, the 3rd sub didn't contribute much. U can try using the dial on that sub to tweak for integration. this will be very time consuming as chances r u will have a dip in another range.

I've experimented and the best way I feel is using the avrs distance tweak. In your case, go with equal increments to max, then slowly come down.

Again, an experienced person can tell u yes it doesn't sound right and u can use ears to tweak but it is very time consuming and has its limitation. Very hard to fix the problems and get it right without any measurement tools.


Offline deadrick

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Re: REW questions
« Reply #14 on: January 20, 2017, 09:31 »
How abt experiementing w speaker port foam for speaker placement close to the wall?
I find it helpful for my 2.0 set up. Reduced the boomy effect quite alot.