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Syrot

Dual subwoofer matching

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I am going to try running dual subs in my media room. 

 

What are people's experiences with using two different brands or models?

 

Should they be similar spec's? even if they are different models? Reason I ask is my current sub is a B&W DB1, and I can't afford the matching new model of this sub. These are super rare to see second hand as well.

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Loaded question but what are you trying to achieve with the sub(s)?

It's not necessary for matching subs but the answer will depend on your goal(s).

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hi syrot... different brands or models are not an issue...

 

however depending on 2nd sub you use might add no value at all. or in fact can even completely muck up what have or be to detriment.

 

how you place the subs in the room and setup, EQ and integrate with room and system are key.

 

will you have some system to fully integrate dual subs woudl be essential in my opinion. :)

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Sorry should have been more specific, serves me right for typing in a query on my phone while my computer was updating software.

 

What I am after is to try and  smooth out bass response throughout the seating position of the room so majority of the listening areas enjoy the same low frequency impact and depth.  We have an L-shaped lounge but the L part is mainly used like a chase rather than someone sitting there with their neck turned to the screen.

 

Currently the central seating position  is close to perfect but left side is of the central seating position is boomy and the right side sounds thin.  Now no doubt this is because the DB1 has an auto calibration and room correction software and the central seating position was where I positioned the calibration mic. (after I initially moved the sub around to what sounded the best to my ears).

 

I suppose this is where it becomes complex as noted by betty-boop,  I really need something that can properly integrate dual subs, if mixing subwoofer brands or models is not a real issue.

Edited by Syrot

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If you are prepared for DIY and have some time and patience I recommend you grab a calibrated mic and start learning REW. If not consult some of the specialist services to do it for you, some found in this forum. I DIY'd and enjoying the fruits of my labour.

Suggest you start by making a detailed layout of your room and listening positions down to mm measurements. Identify as many sub1 and sub2 positions as you can, including all possible combinations. Now you can start to appreciate the effort required to test each configuration. May not do all but there are usually some obvious layout combos which makes some sense and is still practical. Of course you need to select a sub first but you need to consider any limitations due to sub size and position. With that in mind and to narrow some selections, what is your current room size and at what sound level do you currently play the DB1?

 

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the way I look at it ,

can you turn off the calibration ?

as this is giving you the eq for the room in your seat and that , may be fine for you but others miss out !

the nodes are still present in your room ,and that is ,I suspect is what you hear off axis,

a rear sub may well be the answer, and is said to null many nodes, introduced using a front sub 

for my 2ch it was a pain ( the bottom end was too much and was making me ill !,

so I went with 2 front subs,and it worked out much better 

just a thought ,dose your room acoustics need looking at 

1 good sub should do pretty well what you want,unless you want earthquake  style realism

most sub frequencies are said to be non directional and in theory saturate the room somewhat evenly,if nodes are taken care of :)

as I said 

just my thoughts 

 

 

Edited by colinm1

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+1 to all of the comments above. EQing to a single spot will likely cost you watts and dynamics and potentially degrade other positions. Averages across say 3-5 seating positions is always good.

Mixing two different subs my opinion is play each to their strengths. Don't try and make them mimic each others capability if they are different.

Why?
You need to assess each brand and model of sub for their SPL and sensitivity specs. Then you need to level match. Then again post EQ.
I'd suggest going 2way if two different branded subs... And cross them over at different settings based on what your room lacks.

E.g. LFE crossover @ 80hz to Sub A, then high pass @ maybe 45hz, 12dB per octave to Sub B
Sub B low pass 50hz 12dB per octave, low pass usual 15hz or something.

This example would be if you wanted more low bass below the 50hz region, or if you have uneven nodes.

It gets complex with different brands and types.

Having said that, it depends how meticulous you are...... [emoji51] [emoji56]

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Yes the joys of getting low frequency sound set up correctly.   The DB1 is an absolute beast and if I want to completely pressurize the Media room with massive ultra LF content then this thing doesn't let me down.  What I do find is the B & W room compensation software is really good and balances out strong and null bass nodes reasonably as well as other room inconsistencies. 

 

Probably me being picky and trying to get an average response over the main seating positions because I tend not to sit in the same spot all the time.   Mostly likely the average person probably would not notice too much difference as it stands.  I also cannot place a another sub behind the  seating position as the wife wont let me move the lounge forward so it would have be another front positioned sub.  

 

In saying that I have not applied any bass traps to see if that improves things.  Just bough a heap of cheap bass traps off Gumtree tonight to experiment with.   (no idea why people would want purple as a color but they were cheap and a good way to test things without any real expense).  I will see how I go with some additional acoustic room treatment, re-calibrate the sub woofer and see if that is a better option rather than buying more electronic hardware.

Edited by Syrot

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Good call. I run various acoustic treatment and bass definitely needs the attention. Generally start with the opposing corners to the Subwoofer and go from there.

If right, what you mainly notice is a slight tightening of your bass response. That's when you know you're controlling runaway frequency resonances....

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On 06/11/2019 at 12:14 PM, colinm1 said:

most sub frequencies are said to be non directional and in theory saturate the room somewhat evenly,if nodes are taken care of :)

subs are omni-directional - ie they radiate in all directions, but the room modes create substantial peaks and dips around the room - and room modes are difficult to take care of.

Even treated rooms have substantial changes in the bass as you walk around the room.

The key is to get the smoothest bass across multiple listening positions - a 2nd sub can help with this.

 

Mike

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On 05/11/2019 at 10:14 PM, betty boop said:

hi syrot... different brands or models are not an issue...

 

however depending on 2nd sub you use might add no value at all. or in fact can even completely muck up what have or be to detriment.

 

how you place the subs in the room and setup, EQ and integrate with room and system are key.

 

will you have some system to fully integrate dual subs would be essential in my opinion. :)

^this

integration between sub or subs with the mains and the room is the key.

Some good information is in @Paul Spencer's bass integration guide - part 1 linked here:  https://www.hifizine.com/2011/06/bass-integration-guide-part-1/

 

Subs don't have to match - I run only a single sub currently, but I have all the bits to DIY a 2nd sub that's just waiting for sawdust to be made. The 2nd sub will be a small sealed sub at the opposite end of the scale to my current "heavy lifter" tapped horn sub...the bass in my room is pretty good, so my lazy DIY gene is keeping progress to nil.

 

A tool I'll likely investigate further if I build another sub is the Multi Sub Optimizer (MSO) - a free tool that will calculate delays and EQ for each sub to get the smoothest bass across multiple seating positions.

https://www.andyc.diy-audio-engineering.org/mso/html/index.html

To get the best out of this tool, you will need the capability to apply delay and EQ individually to each sub - a capability I don't currently have with my setup unfortunately.

This is what @betty boop was alluding to in his post

On 05/11/2019 at 10:14 PM, betty boop said:

will you have some system to fully integrate dual subs would be essential in my opinion. :)

As you'll read in Paul Spencer's papers - to achieve the best integration between mains/subs/room, you need a measurement rig and the capability to adjust EQ and delay on subs, and because often subs lag behind mains, the capability to delay the mains also.

Something like a miniDSP 2x4 HD in between pre-amp and power amp would achieve this.

https://www.minidsp.com/products/minidsp-in-a-box/minidsp-2x4-hd

 

Why do subs often lag behind the mains?

All filters cause delay - your speaker crossovers, your sub crossovers and the woofers in your mains enclosures.

The woofers in your mains enclosures (sealed or ported) will have a natural high pass filter response based on driver specs and enclosure size (and port specs etc).

Delay increases with the steepness of the filter (the steeper the filter the more delay) and inversely with frequency (the lower the filter the more delay).

 

The delay isn't linear either - it varies throughout the crossover region for "typical" filters (excluding "linear phase" filters) - this is where the term "group delay" is used - speaker design tools such as WinISD can plot the group delay curve for a driver in a box

 

A sealed speaker enclosure will have a natural 12dB/octave high pass filter rolloff with the filter delay governed by physics.

Old school analog subs would typically have an electronic 24dB/octave low pass filter again with the filter delay governed by physics.

If you matched the mains low  High pass 12dB/octave rolloff with the sub high low pass 24dB/octave rolloff at say 80Hz, the sub would lag the mains due to the steeper crossover of the sub.

 

If you can match the acoustic high pass response of the mains with the acoustic low pass response of the sub - they will have the same delay - ie symmetrical crossovers have the same delay profile/group delay.

But in real rooms with subs physically separated from the mains this is rarely achievable. 

 

In most systems, when wanting to add 1 or more subs, it's usually the capability to delay the mains more than the subs which is the challenge - especially in analog/passive setups.

 

Most modern subs have the ability to adjust delay on the sub (ie add more delay to the sub), and Paul Spencer uses the analogy of catching buses.

Assuming the sub lags the mains. The mains catch the 1st bus and you delay the sub further to catch the next bus.

This approach can still achieve good results - a smooth frequency response with no suckouts between subs and mains is the target - perfect time alignment between sub/s and mains IMHO is not essential.

 

The crux is that good integration between sub/s and mains is essential to achieve great "in room" bass - which includes speaker/sub positioning, treatment, and EQ/delay, based on measurements.

IMHO this requires delay/EQ capability on the sub/s as a minimum, but preferably on the mains also.

 

cheers

Mike

Edited by almikel
corrections

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3 hours ago, Neilsy said:

I run various acoustic treatment and bass definitely needs the attention. Generally start with the opposing corners to the Subwoofer and go from there.

It makes no difference where treatment is placed in a room for bass absorption as long as it's placed so it's working - the room response dominates everything.

You absolutely need to place subs in the best position to get the smoothest "in room" bass response at the listening position, but the positioning of absorption to manage lower frequencies is about placing absorption in the room to soak up bass irrespective of the position of the subs - straddling corners, well gapped - as wide and deep as you can get away with.

 

Absorption treatment really doesn't work at sub frequencies - it gets too big/deep to operate effectively below 150Hz or so.

 

That said, in my lightly constructed room that leaks low bass like a sieve, with the absorption I have (lots), it cleans up the mid bass massively - and a few bands of EQ cut below 150Hz works wonders to produce a tight dry bass "room" response.

 

Once you've got the room's bass response under control you can't go back - it's ridiculously addictive and you can't stop seeking out tunes/movies with good bass.

 

cheers

Mike

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13 hours ago, almikel said:

 

Absorption treatment really doesn't work at sub frequencies - it gets too big/deep to operate effectively below 150Hz or so.

 

Don't say that :(,  I am trying to convince my wife that all this supposedly 'ugly stuff' I am putting on in the corners, ceiling and walls will make the world a better place......

 

I love it when the wife comes into the Media room and screams what the hell are you doing in here now.!!!   Mind you she never noticed I swapped out the big tower speakers for some nice bookshelves.  Which then my son decided it was a good idea to blow up..

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16 hours ago, almikel said:

A tool I'll likely investigate further if I build another sub is the Multi Sub Optimizer (MSO) - a free tool that will calculate delays and EQ for each sub to get the smoothest bass across multiple seating positions.

https://www.andyc.diy-audio-engineering.org/mso/html/index.html

To get the best out of this tool, you will need the capability to apply delay and EQ individually to each sub - a capability I don't currently have with my setup unfortunately.

With your second DEQX I think you can apply delay to two or more sub-woofers individually.

Yes you cannot EQ them separately but I think this is far less important.

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8 hours ago, Satanica said:

With your second DEQX I think you can apply delay to two or more sub-woofers individually.

Yes you cannot EQ them separately but I think this is far less important.

agreed - DEQX can apply individual delay to each sub - just not individual IIR EQ to each sub.

 

As to how important individual sub IIR EQ capability is - I don't have it - so I've never tried it - but I expect it would make a difference...esp with 2 very different subs...

 

...a thought experiment which goes OT (apologies to @Syrot) based on my DEQX scenario - likely I'll take it to a new thread if it goes too far... :

  • the goal is smooth bass across multiple listening positions with say 2 subs
  • only global IIR EQ is available across both subs, but individual delay on each sub is available
  • FIR EQ is available on individual subs using the "speaker correction" capability of DEQX - I could keep the mike in the same position (eg primary LP), or change it (left side of listening couch or right side of listening couch) for either sub measurement/correction
  • ignoring FIR EQ for a bit - if each of the 2 subs is in a different room position they will produce a different FR at the primary LP, and more so at either side of the listening couch, requiring different IIR EQ

I would say individual IIR EQ on each sub is required, not just delay - and using FIR EQ on individual subs would muck with the phase independently of the amplitude which could easily make things worse...but certainly worth trying when I build another sub...   

 

cheers

Mike

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Well I have experimented and have added some bass traps, and some room treatment..... re-did the room calibration (via dedicated B&W sub-software and the crappy YPAO that Yamaha has)  and yes the bass is more evened out  (and I did a much wider listening position calibration as well).  Still going to investigate dual subs, and I did see someone selling a DEQX kit a week ago, not sure if I have the time and patience to play with one of these or the money for one, not to play around with that is...

Edited by Syrot

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