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post #1 of 11 Old 06-26-2020, 07:45 AM - Thread Starter
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Help setting up 2 subs

Hi all. I’ve seen some good stuff on the other thread running at the moment regarding 4 x ported Dayton UM’s but I didn’t want to by jack the thread out of respect.

I thought ide read up. I thought I knew what i was doing, the theory was there. But i need the knowledge to be able to fine tune my system. And have some specific questions. My system is as follows

1. 2 x 15” alpine type R in sealed enclosures one at front left (not corner. About 1 3rd in to room on front wall.. and one rear left corner. (Not as good natural response in right rear corner as I first tried.

2. Powered by one NX6000d. Channel one to one sub channel 2 to the other one is 4 ohm. Closest run and the other is 8ohm. I’ve set the limiter on the 4ohm channel to match the other.

3. Using 1 mono sub out from emotiva XMC1 processor to nx6000d using balanced XLR

4. Dirac like EQ along with delay and PEQ from nx6000d.

5. UMIK 1 and rew for setup and verification.


Basically I’m trying to get better quality bass, then integrate properly to mains LS50 speakers and also integrate both subs together properly with phase and delay..

I have started by trying to level match the subs which leads to my first question.

Q1. How do you level match the subs do this when the responses of the subs are so different? What frequency do I match to? Seems impossible to do if the level is different at most frequencies.

Q2. I have been measuring one sub on channel 1 (all EQ off and 200hz low pass with mains amp switched off, then swap to subs 2 and measure that, then try and level them up, then set delays on the rear sub and keep measuring until I get what I believe is the flattest response from 20 -200hz. Is the the correct approach?

Q3. I have been measuring the main listening position and no others as it seems a lot more time consuming and difficult to try for 2 or three measurements. Is this correct?

Q4. Once the delays have been set I used to the PEQ of the nx6000d to flatten the response by taking peaks. And not boosting anything. Running about just less than 3/4 gain. Then I run Dirac live..Is this recommended method? Or should I just leave it and let Dirac do it?.

Q5. And main question. I want to utilise the waterfall that is very one talks about but don’t really know what I’m looking at in that graph. Or understand what it shows me. An explanation would be good.

Is there anything more I should be doing / looking out for?

Also I don’t even know if I’m measuring correctly in rew . I just press measure, set the channel I want and measure it at around -30 volume in a quiet room. No timing reference, no smoothing applied. With the 90 degrees cal file for my UMIK loaded.

Sorry for the long post but wanted to provide more info and will be running measurements tonight and posting graphs so you can all slate my system. Lol


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post #2 of 11 Old 06-26-2020, 07:57 AM
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I generally prefer gain-matching to level-matching, but especially in a situation like this where there isn't a ton of headroom and I could be pushing the subs to their limits. It's very simple to do in a situation like this with identical subs and a single amp, just run them at the same gain. This way both subs run out of headroom together rather than one running out before the other. If the levels at the MLP are different between the two it's not a big deal because they shouldn't be localizable anyway.

Find the best relative delay for summation, then EQ both together, and you maintain that equal headroom relationship.
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Take the Red Pill (BassEQ) BassEQ Demo Clips TR Curves
Video: Sony 85" X900F @ 80" eyes-to-screen (49.4° viewing angle)
Audio: Denon AVR-X4400H 7.2.4 Atmos
Mains: Fusion-15 LR, Fusion-8 Center, Ported Volt-10 Surrounds, Custom 45°/45° Double-Angled Ported Volt-6 Atmos
Subs: The Two Towers (HT18 32cf 11.5Hz x 2), UM18 4cf x 2, Crowson MAs x 4

Last edited by aron7awol; 06-26-2020 at 08:03 AM.
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post #3 of 11 Old 06-26-2020, 08:17 AM - Thread Starter
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That sounds perfect and is helping already. I spend a lot of time EQing the subs individually to try and get it flat and end up with a bit of gain on one and reduction at certain frequencies on the other and obviously that means both subs are under different loads all the time.

Thanks for the suggestions.

Is setting delay to max DB across the F range correct or should I be also setting delay for least ringing on the waterfall graph instead, sacrificing perfect FR for better bass quality?

Also I will be posting graphs but I’m a bit pissed off that my rear sub drops off a cliff at 27hz and literally nothing at 20hz where as the front sub is strong at 20hz. I didn’t think my room was big enough to cause nulls this low on frequency. I get no DB gain at all at 20hz from adding a second sub. Disappointed in that

Room is 5.1m long x 4m wide


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post #4 of 11 Old 06-26-2020, 08:25 AM
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I must say that I also struggle with this
I usually just let my Denon AVR with dual outputs handle things

I have taken loads of REW data of possible sub woofer locations also have a miniDSP HD but I still don't trust that I have got things right

I don't know if it is possible for someone with the correct knowledge can log in using Team viewer and set things up remotely?

I have just bought 2 x SVS16 SB Ultras so will be following your progress
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post #5 of 11 Old 06-26-2020, 10:56 AM
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Quote:
Originally Posted by trojantrow View Post
Is setting delay to max DB across the F range correct or should I be also setting delay for least ringing on the waterfall graph instead, sacrificing perfect FR for better bass quality?
The relative delay that is optimal for summation is almost always very reasonable, say a few ms or maybe more if the subs are far apart in distance from MLP, and should have minimal impact on the waterfall graphs.

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Originally Posted by trojantrow View Post
Also I will be posting graphs but I’m a bit pissed off that my rear sub drops off a cliff at 27hz and literally nothing at 20hz where as the front sub is strong at 20hz. I didn’t think my room was big enough to cause nulls this low on frequency. I get no DB gain at all at 20hz from adding a second sub. Disappointed in that
Such is life with subs in rooms. You can/should do your best with changing sub locations and/or changing the seating location to whatever extent is possible, but ultimately, in most rooms the options are limited and we choose the best compromise. At that point, adding more subs in more locations and/or upgrading to more capable subs are the real solutions.

Take the Red Pill (BassEQ) BassEQ Demo Clips TR Curves
Video: Sony 85" X900F @ 80" eyes-to-screen (49.4° viewing angle)
Audio: Denon AVR-X4400H 7.2.4 Atmos
Mains: Fusion-15 LR, Fusion-8 Center, Ported Volt-10 Surrounds, Custom 45°/45° Double-Angled Ported Volt-6 Atmos
Subs: The Two Towers (HT18 32cf 11.5Hz x 2), UM18 4cf x 2, Crowson MAs x 4
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post #6 of 11 Old 06-26-2020, 11:05 AM - Thread Starter
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I do find it very strange that the rear sub has this 20hz issue at any place along the back wall including both corners.

I though it may have something to do with the temporary 5m of 1.5mm speaker cable being used at the moment until the thicker stuff arrives. Or maybe something wrong with the enclosure design.

Going to test near the cone tonight to get the response without the room in play.

Im maybe thinking about going down the 3 subs route. 2 up front and one rear to fill the nasty 50hz null I get front the front subs.

It never ends.


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post #7 of 11 Old 06-27-2020, 05:00 AM - Thread Starter
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so i finally got round to doing some measurements and it seems that i cant really do anything about my 20Hz problem.

However, please see my waterfall graph and FR attached. (No smoothing).

i have no clue how to read the waterfall graph and if its any good or not. hoping someone can let me know how it looks.
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post #8 of 11 Old 06-27-2020, 05:45 AM - Thread Starter
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Forgot to mention this is fully correct with Dirac and delays set.

I can post with just delays and no eq if it’s better. Just want to know that’s it’s half decent results / performance


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post #9 of 11 Old 06-27-2020, 08:55 AM
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Your 20Hz looks fine to me. It's below 20Hz that seems to have an issue.

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post #10 of 11 Old 06-27-2020, 09:26 AM - Thread Starter
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There’s around 5db of boost added to 20hz over both subs. Where as if the rear sub was in a position where it could output 20hz ide not have to apply this boost in Dirac.at all. Or it would be very minimal.

The rear sub is like 8db down compared to the front at 20hz naturally

As you can imagine, when getting really loud ( -15) they are more or less at Xmax so this is because of the boost I think.

I don’t know how important lower than 20hz is but I’m thinking about porting both subs and tuning to 16hz. With a 14hz high pass filter LR 4th order. If that’s the correct way

That would sort the issue out I think. Obviously below 14 hz I would then have nothing but i think it may be a good compromise.


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post #11 of 11 Old 07-03-2020, 07:19 AM
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It would be helpful if you'd post individual subs sweeps and then combined, so we can see how they are summing.

Also that sweep seems to be with a pretty low crossover/LPF. It's generally a good idea to raise that for these sort of sweeps to show the sub response.

Take the Red Pill (BassEQ) BassEQ Demo Clips TR Curves
Video: Sony 85" X900F @ 80" eyes-to-screen (49.4° viewing angle)
Audio: Denon AVR-X4400H 7.2.4 Atmos
Mains: Fusion-15 LR, Fusion-8 Center, Ported Volt-10 Surrounds, Custom 45°/45° Double-Angled Ported Volt-6 Atmos
Subs: The Two Towers (HT18 32cf 11.5Hz x 2), UM18 4cf x 2, Crowson MAs x 4

Last edited by aron7awol; 07-03-2020 at 07:22 AM.
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