Question about subwoofer upgrade

SteffMarinov

Active Member
...or is it an upgrade...?

Hi guys,

I’ve got two dual 15” passive subs, I bought the cabinets here but can’t remember who from... anyway. Loaded with 4 SiHT 15’s and powered by a QSC CX1402 that delivers 1400 watt at 2oHm per channel. Mini DSP out of my Sherbourn PT-7030 pre.

I’m familiar with REW, have an Umik-1 too.

My problem, well actually a couple, are:

I need to apply A LOT of EQ to get the subs to a desired house curve. I’ve tried all possible placements that my living room allows for, it’s a mid sized room - 3.5m by 6 with an oval wall at one side. I get massive 45 and 59Hz peaks and some nasty looking nulls, in most of the placement positions they match rather than oppose, and in 1 or 2 positions I get a slightly different response but not enough so that the subs fully complement each other.

Now because of that I need to equalise a lot to get rid of the peaks, which leads to reduction where the dips are too (I’ve done a lot of home work and tried inverting phase and delays although the non Hd dsp only allows for a 7.5ms delay), I do get a half decent looking REW graph (have used both manual and auto Rew EQ filters, on both input and output of the minidsp). However. The sound is dull. I manage to get rid of the ringing frequencies but when I play a movie, and I can’t play very loud but still a decent volume, the couch vibrates but I don’t get that chest slam I used to get with a single SVS PB1000 in the past...

So the question is - am I over equalising, or am I listening too quietly? My graph looks flat from 12 to 30Hz, then slopes down about 10db at 80Hz. I’ve tried different crossover points, my fronts are time aligned with the subs, but just can’t get that hit I used to with the SVS.
Do I need to change my approach, my expectations, or split the 4 drivers in 4 ported boxes?
Thanks
 

SteffMarinov

Active Member
This is what subs look like in the current position which is front left corner and front right slightly away from the corner, before and after
B81ADE30-91D1-43D5-BBAB-509FAA9D97AE.jpeg
F413E535-F218-4B28-A3E5-018A460114CA.jpeg
DB42AB80-9A30-43CB-ACB0-9AB1F9911823.jpeg
41CE5606-5BFE-48F8-80D1-2B4C6294A64B.jpeg


This below is a different positioning but end results were the same

C710DAA7-0B49-4A5E-8BBD-E9AA8ECBCAD1.jpeg


EAB6C0DB-FE3D-4A67-B149-F3CBC0496901.jpeg
DE737978-CC1B-4CA7-B83C-0B7F079F6052.jpeg
 

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SteffMarinov

Active Member
This below is a graph of example 1, both subs before REW or MiniDSP filters but I think I had something like -12db on both 45 and 58 hz in the processor at that point

Unfortunately couldn’t find a saved graph of example 2 subs pre EQ but take my word it was very peaky and dip-y

59E5B4B1-F35B-4C4B-A94F-E4283CA10D31.jpeg
 

SteffMarinov

Active Member
Sorry just realised I’ve posted the same end result photo for both - will find the correct example 2 end result in a bit and post it.
 

SteffMarinov

Active Member
Example 1 (current) end result
7BD52AAC-FA50-4A1F-A759-30B161864A31.jpeg
 

sm1ggsy

Active Member
You need to be on all spl tab , you can upload your mdat just rename extension to .text
 

SteffMarinov

Active Member
You need to be on all spl tab , you can upload your mdat just rename extension to .text
No I must have deleted that measurement before saving the bunch, it’s not there...
 

Conrad

Moderator
You have to do Save All, not just Save.

Are you applying EQ to each sub individually?
 

SteffMarinov

Active Member
You have to do Save All, not just Save.

Are you applying EQ to each sub individually?
Yeah I think I’ve accidentally closed the tab during the set up before saving the whole project. It’s not an issue, if a raw graph is needed I can always disable the EQ’s and take a measurement.

No I measure the subs individually, then time align them to the best response, then measure together and work on the EQ as one single sub either manually or with the REW auto EQ.
 

SteffMarinov

Active Member
So I’m about to do it all over again (for the joy of my neighbours 😂..) and I will post progress photos.
One question. What’s the rule regarding where you stay during REW sweeps? Been googling all morning but cannot seem to find anything on whether you should position yourself at MLP, or in a place of the room that’s not gonna be used for listening later? I’ve done both but in regards to the end result when all is finished I can’t seem to hear a difference.
 

Conrad

Moderator
You can't be at MLP as that's where the mic should be!

If you find that it's not measuring differently with you in different places then it doesn't really matter.
You can set a delay on the measurement and give yourself time to leave the room, or just sit next to MLP or something.
 

SteffMarinov

Active Member
Ok this is where I’m at:
Sub 1 - near field, back wall left of the MLP in somewhat of a corner but the short wall opens up into an arch after 2 foot, anyway -

2B938C51-0EBF-44AB-B6A9-D0A9DD28E880.jpeg


Sub 2, front right corner

E76410CE-DB85-4BEC-B86F-0991C59AE507.jpeg


Both subs, with sub 1 phase inverted, two options

Delay on sub 1 - 2.28ms

3985D0F5-FA56-409E-A0F6-567DC99D6427.jpeg


Delay on sub 2 - 2.08ms

9769AB29-5F71-4137-880C-3B55C9B80F53.jpeg


I think I’m gonna start working on the green graph - one that sub 1 (the closer one) is delayed as the graph looks smoother and with a smaller null around the 80-90Hz region

Will appreciate any advice or critique on what I’ve done so far :).

All 4 together for comparison

FD4237FA-648D-41DB-94EB-42C9A9FC5E70.jpeg
 

SteffMarinov

Active Member
Ok actually changed my mind and decided to work on the second graph as it was smoother lower, and the null albeit deeper was a lot more narrow, and past the crossover point, so I’ll deal with it as best as I can after I integrate with the mains.

Before:

BF827D1E-C497-44B9-AF00-00E6BDCE83FE.jpeg


After:
41ED8BA6-FB88-44FB-9B94-4E821C834B73.jpeg


Both for comparison:

8AB7D71D-735F-49CB-AA37-3DB7FDCAB9E8.jpeg


I’ve tried using as little EQ as possible but it took some to tame it
Filters (From Sherbourn EQ)
-9 dB at 46 Hz q8
-12 dB at 57 Hz q11
-8 dB at 102 Hz q9

Filters (From MiniDSP)
-5 dB at 52 Hz q2.5
+3 dB at 70 Hz q13

Now moving onto integrating the mains.
 

Conrad

Moderator
Looks good. That dip might disappear once you add the mains.
 

SteffMarinov

Active Member
Not looking great so far but I’ve only just started playing with the integrating. The REW alignment tool didn’t produce any different results than the graphs below.
Part of the issue might be that my pre only adjusts at 0.5ft steps and the precise REW number was between two steps 🤦🏻‍♂️
E6BBA467-1A5C-4E61-8D8D-9B2DA6CA0B29.jpeg
D4C3E5B4-0F9D-4094-9525-069B385E95E6.jpeg

I guess it’s “measuring all possible combinations” time 😂
 

SteffMarinov

Active Member
Ok this is the end result and I think the best I personally can achieve with my (lack of) knowledge, equipment and room.

Subs and mains, no smoothing
D81EF7A0-144B-4C60-A926-11A90D09B020.jpeg

Full sweep, 1/6 smoothing
D9F0A371-9660-48FF-9E3B-526CF8212856.jpeg

Can’t do anything about the 200 and 300 Hz dips and 500 peak as (beyond any logic of mine) my pre doesn’t have filters there!?
Just listening to some music now and it sounds full and pleasant (after taming the top end of my Adams). Will check a movie shortly and report :)
 

Conrad

Moderator
Looks very nice. You're +-5dB up to about 190Hz, which is great.

A couple of tips:
  • use variable smoothing, it uses different smoothing levels at different frequency bands so that you're seeing about the best result in all cases. You can just use that globally pretty much.
  • Rather than take photos of the screen you can use the camera icon in the top right of the measure window (although you have to hit default on the export to make it observe your settings). Other than that screenshots are easier to read (cmd + shift + 4, if you didn't already know)

If you want to post up your file I and others will take a look, but I can't see anything obviously improvable, it would just be a case of trying different timings.
 

SteffMarinov

Active Member
Gotcha, here it is:

Subs + Mains.jpg
Full sweep.jpg


This time I didn't use REW auto EQ filters, did all manually. So far I am very pleased with the results, bass sounds full, punchy, there's no ringing. Will have to do some more listening but so far it sounds like the best I've ever had.
 

SteffMarinov

Active Member
Right so after some listening and a couple of movies, I can definitely tell there’s some issues. There was a ringing tone in the spectrum and there was no kick.

I decided to play this YouTube test - which goes from 10Hz to 200Hz and I noticed something really strange. 10 and 20 sound very quiet which is understandable since I haven’t cranked up the volume, however - 30, 40, 50 sound at the same volume whereas 60 is audibly a few dB louder. Then 70 is as 30, 40, 50, and 80 peaks like 60 again. 90 and 100 sound in balance. Further up I’m gonna deal with later as there’s some issues there too but how in the world am I getting peaks on 60 and 80 since my graph is flat, if anything I have about 1-2 dB drop on it in the 60-70 region and the big null at 86...?? I’m confused.

If somebody could play this on their system that they know and see if it’s just the video?

Or is there a chance that my Umik is faulty or there’s something wrong with the calibration file...? I’m getting lost.
 

Conrad

Moderator
Did you measure the sweep?
If you turn on the RTA in REW and play the video it'll record the peak levels for each frequency.
 

SteffMarinov

Active Member
Ok I decided to start over because that 85hz null was impossible to get rid of as it was...

So I moved one of the subs away from the corner which reduced its 80 something individual dip and then, after a lot of thinking and googling, decided to cascade the output of my minidsp to its other input in order to get a total of 15ms delay capability (its actually about 17-18, because turns out the dsp adds about 2-3ms delay - even better).

The two moves completely got rid of the null and my subs are now the smoothest they’ve ever been. They needed about 8-8.5ms delay (the value is 6 but I can’t tell how much delay the dsp adds exactly) which was just out of the range of the non HD dsp. Now because my subs were misaligned, when I tried to integrate them with the mains, no matter what I did, one was always gonna be out of phase with LR. This time there was no such issue and the rew alignment tool calculated the delay spot on.

I will post the graphs tomorrow as I’m out at the moment but it looks great. It also sounds very impressive - somewhat “quieter” (might not be the right word but because there’s zero ringing at MLP, I perceive them as a lot tighter, any mud gone and they pack a kick!) but they blend with the mains perfectly.

Now onto dealing with my mains next as they have massive issues in the 100-500hz region... more googling needed! :)
 

Conrad

Moderator
That's a pretty smart way to use the minidsp, very nice.
Hopefully it doesn't introduce any noise into the chain, they're not the quietest of devices.

If you were curious you could find out how much delay it adds by comparing the difference between the delay for a straight sub and that same sub when looped through the minidsp. Not that it really matters.
 

SteffMarinov

Active Member
Thanks - I can't take credit for it cos I got the idea from the MiniDSP forum :)

Right so, update:

I repositioned my L and R out of the bookshelves (They're very tricky to fit cos they are large Adam Audio A77X's and can't just throw them anywhere...) Which resolved some of the room resonance issues, not all but definitely an improvement:

SUBS+MAINS+FULL.jpg


Only this dip between 140-160 Hz which I can't do anything about. This is after EQ'ing them.


Then I measured and equalised the centre and surrounds - centre also has problems around 100-500 Hz range but this one (another Adam 77) I can't move anywhere else. Centre is black, subs red, surrounds are the rest. All are with var smoothing.

SUBS+CENTRE+SURR.jpg


I have since level matched them better. Off to watch a movie and see how I like it :) At least on "paper" though they've never looked better. Well, I've never attempted to eq anything apart subs before anyway so that was a first...
 

Conrad

Moderator
That 140-160Hz dip is quite narrow so I doubt it's too audible.
Those subs look like they're running very hot though, that looks to be about 20dB?
 

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