Author Topic: REW questions  (Read 23766 times)

Online whitesox

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Re: REW questions
« Reply #15 on: January 20, 2017, 16:13 »
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.

When I look at Sevenz's measurements, I noticed higher Xover will get less dip when his C spk interacting with 2 subs.

He ran 3 xover frequencies.
- RED - when i crossed at 80Hz, there seems to be nulls/ cancellation/ modes between 50-80Hz. See the huge dip between the freq?
- YELLOW - crossed at 90Hz, the null seems to be better. But still no good.
- BLACK - crossed at 100Hz, the null seems to be minimized.
http://www.xtremeplace.com/yabbse/index.php?topic=231629.45

but if I adjust it to 90-100hz then will I still get dip at 80hz for 74db although 50-70hz is good?



He has steeper slope down at 50-70hz thats why he tried to use Xover 80hz get <74db, Xover 100hz to get max reading 76db @70hz....  :o


[/quote]
I am so confusing???

Anyway, I do appreciate for your value-able advise. I will take note on that !
Let me get Umik-1 microphone...
BTW, how did you get yours?
I hope other brother are also keen to buy so we can combine for cheaper shipment cost
 :)
« Last Edit: January 20, 2017, 20:26 by whitesox »

Offline ronildoq

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Re: REW questions
« Reply #16 on: January 20, 2017, 18:39 »
In order to find the best cross over, u need to look at the centre channel and the roll of point, then u also need to look at the measurement of combined 3 subs roll off point,
You must put the two graph together and see. My advice is don't go above 100hz, especially when u r running 11 channels, don't forget each individual channel is sending bass info to the subs. It will start to localise and get bloated, especially the midbass.

I believe your Centres r using at least 61/2" woofer , so u can comfortably cross over at 60hz. Go with distance tweak, u won't go wrong.

Let me upload the graph then will be easier to see

Offline ahduck

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Re: REW questions
« Reply #17 on: January 20, 2017, 18:59 »
Hi Bro Ron,
Is it possible to invite me if you happen to drop by anyone of follow members place to assist in measurements or setting up multi subs.
I'd like to learn a thing or two on REW s/w and umik.

Sent from my Game Boy Advance 32gb 4GLTE/WiFi using Tapatalk

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Offline sevenz

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Re: REW questions
« Reply #18 on: January 20, 2017, 19:06 »
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.

Also will work I guess.... i would only put speaker foam if i have no other choice..... u would lose quite a bit of the mid bass and might face more challenge when integrate/ cross with subs.

Esp when u have no sub, u tend to lose a lot on the low and mid bass and overall sound might not sound so 'full' (not sure what is the best word to describe it... ha....)
« Last Edit: January 20, 2017, 20:54 by sevenz »

Offline sevenz

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Re: REW questions
« Reply #19 on: January 20, 2017, 20:59 »
When I look at Sevenz's measurements, I noticed higher Xover will get less dip when his C spk interacting with 2 subs.

Yo bro, u cant assume and apply like that. =) EVERY room is DIFFERENT. The FR that i posted is how it behaves in MY ROOM.

Maybe yours, u use higher freq, it will dip more or react differently. Hope u get what I mean.... :)

Online whitesox

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Re: REW questions
« Reply #20 on: January 20, 2017, 21:10 »
Yo bro, u cant assume and apply like that. =) EVERY room is DIFFERENT. The FR that i posted is how it behaves in MY ROOM.

Maybe yours, u use higher freq, it will dip more or react differently. Hope u get what I mean.... :)

Hahaa... you might be right bro... different room will have different curve... but higher Xover will get flatter response right...? correct or not? 
BTW, did you do measurement when your C spk and 2 subs interacting (sounding) together after Audy calibrated them?
(I am not referring to your combine graphs but something like my graphs)
 :)
« Last Edit: January 20, 2017, 21:12 by whitesox »

Offline sevenz

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Re: REW questions
« Reply #21 on: January 20, 2017, 21:35 »
Hahaa... you might be right bro... different room will have different curve... but higher Xover will get flatter response right...? correct or not? 
BTW, did you do measurement when your C spk and 2 subs interacting (sounding) together after Audy calibrated them?
(I am not referring to your combine graphs but something like my graphs)
 :)

U buy umik mic already then I tell u...  ;D ;D muahahaha
« Last Edit: January 20, 2017, 23:44 by sevenz »

Offline Jag

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Re: REW questions
« Reply #22 on: January 20, 2017, 21:48 »
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)
 :)

My name popped up in this interesting thread. Sorry I didn't reply earlier with me occupied with a very busy day job.

Here are my thoughts about Whitesox's measurements:

1) A measurement of just the center channel alone would be very helpful in determining the correct cross-over point and phase alignment of center and subs.
2) Right now, its most LIKELY the center is cancelling the sub at  65Hz. Measurement from (1) would confirm this.
3) When doing measurements, measure each speaker and each subwoofer independently. This is so as to identify the FR of each transducer first in its individual form.
4) REW could really pick apart all the problems. For sure, your before curves were so bad that just one 1 subwoofer could do far better than 2 subs.
5) I have been adovating the science of HT, rather than the "poetry of words" that overflowed from the audiophile world. Measure, measure , measure. Your example is a classic text book example of maximizing multiple subs.
6) Get a Umik-1 mic and SPL meter from CSL. I'm willing to chip in with shipping costs since I would like to get a SPL meter to replace mine.
7) Don't assume that another friend's same exact model and speaker can go down to 60hz, that means yours also can. At LFE frequencies, the room can change the bass more than you think


Can someone send me whitesox's MDAT file so that I can help to analyze?

The 80hz dip is considered a wide band dip and its not good. But its a better FR than original. The data tells me that the Center and LFE channels are not properly time aligned. If they were properly aligned, you would have peaks at the cross-over freq where they constructively combine.
« Last Edit: January 20, 2017, 21:55 by Jag »
Electronics : Denon 7200, MiniDSP Dirac 88A, Emotiva XPA-5 Gen2
ATMOS Audio : Martin Logan Ethos (L&R), ML Motif X(C), ML Motion 4 (14pcs surround spkrs)
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Video : Sony VPL-HW55ES, Stewart Screen Studiotek 1.3
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Offline whyeme

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Re: REW questions
« Reply #23 on: January 20, 2017, 23:54 »
I am also ready to make the commitment to try learning REW myself. Too bad there is no sticky thread here in XP to ease less technically/mathematically inclined guys like myself into it  :-[

Nevertheless, I would like to join in any mass order purchase for the Cross Spectrum Labs Umik-1 mic and SPL meter to lessen our overall shipping costs.

http://www.cross-spectrum.com/index.html

Also thinking of getting this budget tripod for the umik and spl meter

https://www.aliexpress.com/item/Top-Sell-Portable-Professional-Aluminum-Telescopic-Camera-Tripod-Stand-Holder-For-Smart-Phone-For-iPhone-For/32622915038.html?spm=2114.13010208.99999999.264.trIYNd

Okie now to search for some basic guides to REW...
Hall: Philips 65PFA4350/98. Oppo BDT-101CI. Emotiva UMC-200. Rotel RMB-1512. SB Acoustics ARA. Dynaudio Contour SCX. Dynaudio Audience 42. Wharfedale 10.1. PSA XS30. Orisun DD+12. miniDSP Dirac DDRC-88A/BM. Belden Studio 814. IsoAcoustics ISO-L8R155. Zidoo H6 Pro.

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Offline sevenz

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Re: REW questions
« Reply #24 on: January 20, 2017, 23:57 »
Count me in for the spl meter too =)

ghemml

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Re: REW questions
« Reply #25 on: January 21, 2017, 00:18 »
I don't use REW but I'm a hardcore ARTA user.

I have tutorials and guides to help you guys to setup dual channel measurements, almost like differential mode.

Offline Jag

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Re: REW questions
« Reply #26 on: January 21, 2017, 04:07 »
Guys, there are many (and I really mean many) YouTube walk through guides available.

To begin, the pre-requisites are:

1) 1pc umic-1 from cross spectrum labs .com
2) a laptop running win7 or better connected to AVR via hdmi
3) a mic stand. (I don't recommend camera tripods because we are attaching a mic, not a camera).
4) A few hours to learn REW at a leisurely pace from scratch.

https://youtu.be/ial9y0ipNeU

Lastly, I'm more than happy to help folks here on any difficulties with using REW. But pls ask specific questions rather than "Dunno how to use. How to begin ah?"

« Last Edit: January 21, 2017, 04:39 by Jag »
Electronics : Denon 7200, MiniDSP Dirac 88A, Emotiva XPA-5 Gen2
ATMOS Audio : Martin Logan Ethos (L&R), ML Motif X(C), ML Motion 4 (14pcs surround spkrs)
LFE : Dual Rythmik FV25HP & Crowson Motion Actuator
Video : Sony VPL-HW55ES, Stewart Screen Studiotek 1.3
Source : HTPC
Fully automated HT via Alexa, Z-wave and Logitech Harmony Remote Control

Offline whyeme

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Re: REW questions
« Reply #27 on: January 21, 2017, 11:00 »
Thanks Jag that's very helpful! But in the video abv he doesn't use umik 1. So with umik 1 microphone no need all those other stuff correct? I also have a TECMAN TM810M  SPL meter which allows me to set to SLOW but no C weighting. Is it usable?
Hall: Philips 65PFA4350/98. Oppo BDT-101CI. Emotiva UMC-200. Rotel RMB-1512. SB Acoustics ARA. Dynaudio Contour SCX. Dynaudio Audience 42. Wharfedale 10.1. PSA XS30. Orisun DD+12. miniDSP Dirac DDRC-88A/BM. Belden Studio 814. IsoAcoustics ISO-L8R155. Zidoo H6 Pro.

Bedroom: Plinius 2100i. Dynaudio Excite X12. iFi Micro iDSD. IsoAcoustics ISO-L8R155. Belden Studio 814.

Offline ronildoq

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Re: REW questions
« Reply #28 on: January 21, 2017, 14:17 »
Hahah sifu Lai Liao, I have the mdat data jag, I'll send it to you plus share it here. Looking at all three subs they are all in phase and time aligned, the only problem is when integrating with the centre channel.

I believe the svs subs r using LR filters, but not sure about the b&w  mains.

Count me in if someone is getting the new spl meter! I need to get one to measure absolute SPLs.

Yea I think A sticky on how to use REW on will be really helpful, honestly I have Jag and Sevenz to thank for plus some internet source and videos to watch, otherwise I don't know where to begin too.

Offline ronildoq

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Re: REW questions
« Reply #29 on: January 21, 2017, 14:56 »
ok, the pic below is bro whitesox's centre only channel, and Subs channel only.

subs rolloff approx 100hz and centre there is a dip 75-90hz, that explains the dip when crossing over at 60, 70 & 80.



ok sifu Jag, over to you now... ive sent you the MDAT data... maybe you have a formula to calculate time delay vs distance. Im not sure how to calculate that. what i would normally do is look at the roll off region between the two, somewhere between -6db, that would seem to yield the best crossover response. then tweak the distance in steps of 0.3cm and slowly fine tune till 0.1cm for the perfect crossover.

read up another way to tweak this is by adjusting the mains, but then all 5 main speakers have to be time aligned measuring the impulse response, that is too tedious, so i still prefer the subwoofer distance tweak.

your comments please

guys, only way to do this is with a mic.