Sierra Tower w/RAAL in room response question

[curtis]

Can room modes and boundaries cause these types of results?

Absolutely!

This is where placement and room treatment comes into play.

That miniDSP should also control sub output. Currently, you really don't have much to adjust the integration of your mains and sub. That is why I suggested using the HPF on the sub between the preamp and amp inputs on the HK.

[curtis]

Unfortunately, it doesn't look like the L12 has an HPF out.

OK...then my suggestion won't work.

Yes...something like the miniDSP would be very useful. Does the Antimode do high-pass?

[curtis]

Oooh...miniDSP has a new model. I would be all over this if I had a 2-channel rig with a sub.

https://www.minidsp.com/products/minidsp-in-a-box/flex

[jimlucci]

Absolutely!

This is where placement and room treatment comes into play.

That miniDSP should also control sub output. Currently, you really don't have much to adjust the integration of your mains and sub. That is why I suggested using the HPF on the sub between the preamp and amp inputs on the HK.

I did try many different room placements and orientations, but was not able to affect the large nulls and peaks in the 10-500Hz range - I guess I thought I would see more of a change in response than I did. I also measured each Tower individually pointing the Umik1 directly at each speaker from a meter away, no change in measurement (not sure that is a legit test though).

Everything appears to be working as it should - just some anomalies in either the readings or the room. I don't have a lot of experience reading these, so that is why I figured I would ask here.

[davef]

Hi Jim,

We are jumping too far ahead here.

First off, there is nothing wrong with your sub, towers or receiver. Your in-room response looks good and you are fully enjoying the sound. +/- 10dB swings (and even higher) are perfectly normal for an in-room response.

I didn't realize you are running the towers full range, that changes things dramatically with regard to what is causing that dip at ~ 80Hz. More than likely, and as others pointed out, it is simply a null at your listening position. You can keep the towers and sub where they are and place the mic at different positions in your room and you will see things change.

Now, assuming you are NOT using the LFE input on the L12 (in your setup, you should not be) - I recommend turning the low pass filter on the sub all the way up, and then adjust the phase setting on the sub using an 80Hz sine wave (not a sweep) with REW can generate for you. As Curtis mentioned, use an SPL meter and set the phase to where the output level is highest. You must run the towers and sub together for this.

This is the best you can do in your situation unless you want to change your listening position.

If it were me, and I was going to spend some additional $$$, I would get a modern receiver with bass full management, auto EQ such as Audyssey or DIRAC etc., and pre-outs. This way you can properly integrate sub and speakers and the Auto-EQ function will easily compensate for that dip.

That being said, after all that - you may or may not even hear a difference. This is one of the problems when consumers now have readily available access to software like REW. They begin to think something is "wrong" and the majority have little understanding of room acoustics. It is shocking to me how much more time I spend these days assisting people with understanding measurements they take of their rooms. It has gone from perhaps 1-2 hours per week to at least an hour per day just in the past 2 years, especially during COVID lockdowns.

Again, don't go nuts with this, sometimes room issues can not be solved - and even worse, sometimes the solution makes things even worse. Enjoy the system!

[davef]

Jim,

In addition, your room is nearly a perfect square. Those are the worst dimensions for an even room response below the Schroeder frequency. Based on the room dimensions, you have a very strong axial mode and a strong tangential mode at ~74Hz. That is what you are seeing in your measurements. Ideally, you never want to see axial and tangential modes at the same frequency, but this is the issue with square or nearly square rooms.

2 subs will help, as will my suggestion about raising the LPF and adjusting phase, and you will also need EQ to fill in the rest - if you want to try and get rid of the null. No amount of room treatment available to you will help with your null as it is too low in frequency, so don't waste your money and time trying room treatments. Also, understand that correcting this null at your listening position will cause problems in other areas of the room, not a big deal if you only listen at this one position though...

You can also set the PEQ on the L12 to the same frequency as the null, and adjust the boost amount...

[jimlucci]

Hi Jim,

We are jumping too far ahead here.

First off, there is nothing wrong with your sub, towers or receiver. Your in-room response looks good and you are fully enjoying the sound. +/- 10dB swings (and even higher) are perfectly normal for an in-room response.

I didn't realize you are running the towers full range, that changes things dramatically with regard to what is causing that dip at ~ 80Hz. More than likely, and as others pointed out, it is simply a null at your listening position. You can keep the towers and sub where they are and place the mic at different positions in your room and you will see things change.

Now, assuming you are NOT using the LFE input on the L12 (in your setup, you should not be) - I recommend turning the low pass filter on the sub all the way up, and then adjust the phase setting on the sub using an 80Hz sine wave (not a sweep) with REW can generate for you. As Curtis mentioned, use an SPL meter and set the phase to where the output level is highest. You must run the towers and sub together for this.

This is the best you can do in your situation unless you want to change your listening position.

If it were me, and I was going to spend some additional $$$, I would get a modern receiver with bass full management, auto EQ such as Audyssey or DIRAC etc., and pre-outs. This way you can properly integrate sub and speakers and the Auto-EQ function will easily compensate for that dip.

That being said, after all that - you may or may not even hear a difference. This is one of the problems when consumers now have readily available access to software like REW. They begin to think something is "wrong" and the majority have little understanding of room acoustics. It is shocking to me how much more time I spend these days assisting people with understanding measurements they take of their rooms. It has gone from perhaps 1-2 hours per week to at least an hour per day just in the past 2 years, especially during COVID lockdowns.

Again, don't go nuts with this, sometimes room issues can not be solved - and even worse, sometimes the solution makes things even worse. Enjoy the system!

Thanks Dave!

I can definitely see how people might go down the measurement bunny-hole - I am not interested in doing that to be sure. I will say, however, it has been a good learning/understanding exercise. Thanks for your advice and input on this. I think I have everything setup about as good as I can in my environment and as I have said from the beginning - it sounds amazing!

[jimlucci]

Jim,

In addition, your room is nearly a perfect square. Those are the worst dimensions for an even room response below the Schroeder frequency. Based on the room dimensions, you have a very strong axial mode and a strong tangential mode at ~74Hz. That is what you are seeing in your measurements. Ideally, you never want to see axial and tangential modes at the same frequency, but this is the issue with square or nearly square rooms.

2 subs will help, as will my suggestion about raising the LPF and adjusting phase, and you will also need EQ to fill in the rest - if you want to try and get rid of the null. No amount of room treatment available to you will help with your null as it is too low in frequency, so don't waste your money and time trying room treatments. Also, understand that correcting this null at your listening position will cause problems in other areas of the room, not a big deal if you only listen at this one position though...

You can also set the PEQ on the L12 to the same frequency as the null, and adjust the boost amount...

I definitely think another sub would help in my room. I had anticipated doing that when I bought the Towers and the L12 in the beginning. The REW measurements did help find the best spot for the Subwoofer I have (which is different than where I had it) and also helped phase align it with the mains, but I can see where people can get obsessive about readings - not something I am interested in doing....JC

[racrawford65]

OK...then my suggestion won't work.

Yes...something like the miniDSP would be very useful. Does the Antimode do high-pass?

The Antimode Dual Core does (both HP & LP). The Antimode 8033 only has LP.

[djDANNY]

Actually, just the opposite. Phase issues between the sub and speakers will cause peaks and nulls in the response that cannot be corrected by EQ (it will only make them worse). Once phase on the sub is properly set, EQ'ing becomes much simpler as you are then simply adjusting for room acoustics.

I get what you’re thinking but in real life practice, unless you were good at creating the proper filters manually, it’d be pretty difficult. I personally like to start with having as flat of a frequency response as I can get for both the speakers and sub and let the proper crossover slopes allow them to summate to be flat (no different than how you would design a speaker with two drivers). That means I EQ first, then get the phase between speakers and sub aligned as much as possible over the crossover range. You could do it the way you suggested but now you’re running sweeps that have combined outputs of the speakers and sub and then trying to just EQ one to affect the summed response in the crossover region. Not impossible to do but not the preferred method in my opinion. Much easier to EQ both separately then phase align them after.