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Optimising my minidsp Flex HT+Fosi V3+ xtz cinema edge 1x12+revel m16 system

marX

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Jan 8, 2019
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Hello. This is to document (and seek help) setting up and optimising my music and movie system.
I’m at full volume on the laptop ( source), 3/4th on the fosi stereo amp and 1/4th gain on the xtz with port closed with the supplied foam bung and the eq set at reference. The volume at minidsp is -12.

The procedure I found I the Internet is this:
1. Get the sub to output 75db while muting other speakers and find the response and eq it to as per the target curve (Harman).
2. Then right front.
3. Try sub+right overlayed and find an optimum crossover frequency. Then find the response of sub+right and do 3 measurements to the either side - imagine it’s 80hz. Then 60, 70,75, 80, 85, 90, 100 hz and select the most optimum frequency.
4. Do the above with left speaker.
5. Set the output L+R and sub with the optimum crossover and check the response. Fine tune the eq as needed.
6. That’s it?

I’m failing at the first step. When I apply the biquad filters to the sub in minidsp, the response does not match the predicted response in REW. It does not make any sense. I need your guidance to troubleshoot. At the moment I put a temporary crossover (-3db per channel on the input to the sub and -24db slope on the speakers and sub) in order to listen to the music but I feel there is too much sub-bass.
 
Current SPL with phase.
default 100hz crossover.jpg
 
I can't fault your process although I never found xovers like that. Maybe that's a better way though? And until you figure this out, you can roll off the sub-bass in the Minidsp via the crossover tool.

My understanding is that Crossovers in the bass region are as room dependent as anything. A crossover into a null is probably a bad idea etc.. To my poorly trained eye, an xo of 65-80 looks promising. That looks like a room null 50-60. Below that your subwoofer is likely able to fill in, especially with two. I usually used a steeper sloped roll-off.

I would then just do the sub and speaker together and get biquads for each side together.
 
Subwoofer SPL+Phase (no crossover, sub only) - very bad response.
default sub.jpg
 
I can't fault your process although I never found xovers like that. Maybe that's a better way though? And until you figure this out, you can roll off the sub-bass in the Minidsp via the crossover tool.

My understanding is that Crossovers in the bass region are as room dependent as anything. A crossover into a null is probably a bad idea etc.. To my poorly trained eye, an xo of 65-80 looks promising. That looks like a room null 50-60. Below that your subwoofer is likely able to fill in, especially with two. I usually used a steeper sloped roll-off.

I would then just do the sub and speaker together and get biquads for each side together.

As you can see in the sub response, there is a huge null at 54hz. Also a rising response from 30 hz. I'm using the sub as sealed. Should I change the XTZ sub options to Eq1 or 2? Or do I take the bung off and make it a ported sub to reduce the sub-bass (30 hz and below)?
 
That's without any EQ? Honestly, I doubt there is much you can do about it. Pretty much everyone here has one unless they are fortunate, highly skilled or rich. You might try moving the subs around. I don't know your subs at all but porting or not shouldn't dramatically change your room curve.
 
That's without any EQ? Honestly, I doubt there is much you can do about it. Pretty much everyone here has one unless they are fortunate, highly skilled or rich. You might try moving the subs around. I don't know your subs at all but porting or not shouldn't dramatically change your room curve.
What I meant is ported sub generally has a bigger roll off after the port's tuning frequency.

Currently the sub is sitting in front of the display. I'll try different positions tomorrow.

Btw I have only a single sub.
 
Try the sub in the corner first. Plugging ports might help a little.

Honestly, with eq you should get a decent FR out of that.
 
Don't you think putting the sub in the corner excite all the room modes?

See, I bought this iPhone app called SubZone which would would suggest good placement zones for the sub based on the room size and listening position.

It recommended some locations which I will try and report back. Let's see.

It says putting the sub in the corner would result in very bad nulls BTW.
 
I tried 12 different positions. No dice. I need to do more positions.

There is like 25DB difference between nulls and peaks between in most measurements.
 
Damn. I never thought it would be this hard but I managed to do it. I haven't cared about the phase though. I'll deal with it later. The only issue is the dip at 110 hz and 87 hz. Apart from that. its within +- 1 db mostly (but I had to eat a lot of amplifier power though).
 
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