Measuring, room responses using REW..

[Hari Iyer]

IMO, any adjustments to the subwoofer should be made in consideration with the front main speakers. There could be quite an overlap of frequencies betweeen the mains and fronts and if they are out of phase then they will cause cancellation in the listening position. IMO, leave the REW aside for a while and start trusting your ears for this. If you have a variable phase control in you subwoofer amp then its more easier to adjust the phase. I usually advise the below,

1. Reverse connect the subwoofer speaker from the main front speakers.
2. Play music with lots of low-end response with equally good mids and highs.
3. Review the low-end of your speaker system sitting at the listening position if they are in sync.
4. Ask some one to adjust the phase control of your subwoofer till bass is minimum in your room with you still sitting at your listening position.
5. Once the minimum bass point is reached then your subwoofer and mains are completely out of phase.
6. Now correct the phasing of the subwoofer and play the same track again to check if the fronts and the subwoofer are in sync.

Its much easier to determine the minimum bass point by reversing the speaker polarity than finding the maximum bass point for your speaker system.

 

[elangoas]

IMO, any adjustments to the subwoofer should be made in consideration with the front main speakers. There could be quite an overlap of frequencies betweeen the mains and fronts and if they are out of phase then they will cause cancellation in the listening position.

Sure..I will take the next measurements with Fronts + subs..

IMO, leave the REW aside for a while and start trusting your ears for this.

Before making REW measurements, all 5 listening positions in my sofa sounded almost same.. i couldn't distinguish them by ear..But the same 5 listening position in my sofa using REW measurements is showing different picture..

The only place in my room where i could distinguish the loudest bass was, when i was standing and moving towards the right side of my listening position near walls..

If you have a variable phase control in you subwoofer amp then its more easier to adjust the phase. I usually advise the below,

1. Reverse connect the subwoofer speaker from the main front speakers.
2. Play music with lots of low-end response with equally good mids and highs.
3. Review the low-end of your speaker system sitting at the listening position if they are in sync.
4. Ask some one to adjust the phase control of your subwoofer till bass is minimum in your room with you still sitting at your listening position.
5. Once the minimum bass point is reached then your subwoofer and mains are completely out of phase.
6. Now correct the phasing of the subwoofer and play the same track again to check if the fronts and the subwoofer are in sync.

Its much easier to determine the minimum bass point by reversing the speaker polarity than finding the maximum bass point for your speaker system.

Would this also help in smoothening the freq resp?..

 

[Hari Iyer]

More than the FR, the phase needs to be smooth without causing out of phase conditions. The very reason there are dips in the FR is due to phase changes at those frequencies after hitting some reflective surface like a sofa/ furniture or walls. If you can maintain a good Minimum phase response of around +90 Deg to -90 Deg without any resonance in the response then you are done. Avoid all phase changing reflective surfaces in the room. You can find that out by checking the frequency dips and converting that frequency to wave length to identify the offending object.

 

[elangoas]

More than the FR, the phase needs to be smooth without causing out of phase conditions. The very reason there are dips in the FR is due to phase changes at those frequencies after hitting some reflective surface like a sofa/ furniture or walls. If you can maintain a good Minimum phase response of around +90 Deg to -90 Deg without any resonance in the response then you are done. Avoid all phase changing reflective surfaces in the room. You can find that out by checking the frequency dips and converting that frequency to wave length to identify the offending object.

Should i measure the response with & without sofa in my room & too see if that causes a dip in one of my listening position?..

 

[elangoas]

Recently completely dual sealed subs and the measurements seem to look good at my listening position up to 60Hz.. If i crossover the subs to mains at 60Hz, should i position my L-C-R on the front wall to minimise width room modes?..

From the above table, i need to position my L speaker 42 inches from left wall, my R speaker 42 inches from right wall and the center speaker at center of room width.. At present my L & R speakers are away from the ideal locations by 7 ~ 10 inches..

Where should i position them ideally to reduce the width modes at my listening position?..

 

[elangoas]

Here is an image of width room modes and the the present positioning of L-C-R in my room..

and the freq response of L + R + subs in my room bet 10Hz - 200Hz..

If i re-position the L/R speakers, by few inches, would it help minimise the peaks & dips?..

 

[elangoas]

Here is the same measurement as above from 10Hz - 500Hz, think should cover most modal responses..

There seems to be huge dip between 80Hz - 100Hz & one more between 100Hz - 200Hz.. Would re-positioning the L/R speaker help? The reason i ask is i have the L/R wall-mounted, limitation to move few inches and re-measure.. If there is a possibility to minimise these dips by moving the L/R, please let me know by how much to re-position them..

 

[sud98]

Sorry wrong thread

 

[elangoas]

comment moved to other thread..