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EQ a sealed subwoofer with miniDSP


Poleepkwa
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Hello! 

I am looking for some help in "baking" in some EQ for my DIY subwoofers, before doing bass management in my processor. 

I currently have a pair of sealed 150liter cases with Faital 18XL1800 elements.

These are EQ by a MiniDSP 2x4 HD and powered by bridged Pascal amps.

These are inspired by the sealed subs from Grimani, Procella and of course JTR.

I have REW and UMIK and some basic understanding of the steps involved, but I am unsure as to what will be the " correct" way to proceed.

In the JTR Captivator S2 review their is stated that  "S2 is still employing significant low frequency boost in order to extend and flatten the response down to below 20Hz" 

The way I see it is too: 

a) use a Butterworth 6db LPF@25hz to bring out the low bass

Or

 b) add bass boost where the room gain starts to drop off.

How should I proceed to design and implement that freq shaping for my subwoofers?

I am unsure why most people seem to be using option (b) and not (a)?

Anyone able to explain the theories behind these methods?

 

 

 

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Not sure if I understood correctly, but many will add 10db from the 16hz to 32hz range and then deploy an overall 10db gain cut. 

Expectations/theory being the 10db add in the low frequency range won't ask too much from the amplifier due to the global 10db gain cut.

With many designs (sealed probably more so), the 10db add to the low range will result in a "flatter" response frequency VS SPL curve. 

Not sure how that works in practice VS theory as I've never tried it myself.

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Yes. I think you understand. I am asking in a rather long-winded way how does JTR get their subs frequency response looking like it does (flat from 20-160 Hz and then a steep rolloff after that).

 Meaning that any sealed subwoofer will start to roll off towards the lower end without any EQ, right?

Could it be that they are using a Linkwitz transfor to improve the low-end extension?

 

 

 

 

 

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You can use an LT circuit for this or regular dsp EQ filters. 

You will need to be able to take measurements of the subwoofer in order to develop EQ that modifies the response in the manner you want. Without measurements of the sub you are somewhat shooting in the dark. You can use simulations of the sub system to develop EQ but this will usually be in the ballpark only. 

Also keep in mind that EQ for flat response outside will often result in excessively boosted low end once the sub is placed in a room. Again measurements of the sub in room help a lot. 

If you want to play around with filters REW is free and has a robust EQ function, plus the ability to take measurements of course. 

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@RicciThanks.

I manage to apply a Linkwitz transform to my subs.

 

So after this the steps would be:  

1)measure subs combined in-room response with no filters or crossovers with REW

2) use REW Auto EQ to flat like in this example.

https://www.minidsp.com/applications/auto-eq-with-rew

3) Apply filters and crossover if needed in MiniDSP.

4) Experiment with housecurve if needed.

Does this seem like a good procedure?

Anything  else should I keep in mind?

Is it good to apply the Linkwitz transform first (boost), and then the room EQ (cut)?

 

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On 12/28/2021 at 10:13 AM, Poleepkwa said:

@RicciThanks.

I manage to apply a Linkwitz transform to my subs.

 

So after this the steps would be:  

1)measure subs combined in-room response with no filters or crossovers with REW

2) use REW Auto EQ to flat like in this example.

https://www.minidsp.com/applications/auto-eq-with-rew

3) Apply filters and crossover if needed in MiniDSP.

4) Experiment with housecurve if needed.

Does this seem like a good procedure?

Anything  else should I keep in mind?

Is it good to apply the Linkwitz transform first (boost), and then the room EQ (cut)?

 

Add first and then subtract later. Or subtract first then add later. It’s all the same in terms of maths.

 

for a commercial product that you were trying to sell you probably do want to show that it has good bass response and works well in many rooms so you’ll probably need to boost 1st to target your Anechoic response (-3dB/-6dB/-10dB) etc. and allow user to EQ for good in-room smooth bass response. 
 

For your own use no need to worry about that. Just plonk it in for desired room; take measurements at the listening position and EQ it to your taste.

if you are using it in theatre with multiple listeners, use of multiple sub place throughout the room may help smooth out the bass response.

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  • 2 weeks later...

This will probably work out the easiest, or least time-consuming.

Just measur them in-room and EQ to flat, without any need for Linkwitz transforms.

It has been pretty informative to test the different Q settings with that though.

EQ them flat in-room to flat in room. Getting the rest of the room done, so hopefully I can start to test so REW EQ settings soon.

@Ricci

I have a small "half wall" right behind my listening position. It's a stairway that goes down to the groundfloor. This is a open area so, cannot listen very loudly when kids are in bed. Some one suggested that so could build in some smaller subwoofers on that wall to provide "tactile" response. 

That wall is roughly 5 inches thick so That would be the max depth. 

One of the few options that could work in such a small spaces (at least her in Europe seems to be the old Peerless XLS 12/10 series and a few pro drivers that could work in about 40 liters sealed( Faital Pro 10RS350, Sica 10SR2,5CP). Al of these will be about 100-130€ euros. Peerless can be had pretty inexpensively when buying used.

 

15" pro driver might work too, bit it will need quite a a bit of EQ. 

I seem to remember that you like the Peerless XLS for what it was. Would you still recommend them? 

Not sure if it is even a good idea considering I have the 18" Faitals upfront....

Any thoughts and suggestions?

 

IMG_20220109_191238.jpg

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Doing nearfield subs behind the seats isn't a bad idea when you still want to feel the bass but also want to keep the volume manageable. The XLS series is a decent woofer still. For this type of use look for something with a bit of xmax since you'll probably want to boost the lower freqs where the tactile shake happens most. I'd choose something like the XLS for this versus the 15" pro woofs. Cheap 12" car woofers from JBL or Infinity could work well also. 

One thing to consider is the backwave of the drivers in that stair wall. If it isn't solid you may have trouble with noise and vibration from it. The drivers will be coupled to it and that wall will act as an enclosure. 

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I'd recommend the $30 JBL driver under your couch/sofa as another option worth perusing. Being across the pond, not sure if you have access to that driver and/or at that price, but many use them on avsforum. Think they call it BOSS setup or something similar.  

 

Edit: it is indeed boss - back open sub shaker on AVS 

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18 hours ago, Ricci said:

Doing nearfield subs behind the seats isn't a bad idea when you still want to feel the bass but also want to keep the volume manageable. The XLS series is a decent woofer still. For this type of use look for something with a bit of xmax since you'll probably want to boost the lower freqs where the tactile shake happens most. I'd choose something like the XLS for this versus the 15" pro woofs. Cheap 12" car woofers from JBL or Infinity could work well also. 

One thing to consider is the backwave of the drivers in that stair wall. If it isn't solid you may have trouble with noise and vibration from it. The drivers will be coupled to it and that wall will act as an enclosure. 

Thanks. Good point about the pro-woofers. I will start to keep my eyes open for some used Peerless XLS drivers.

 

That wall is not solid. Just studs and gypsum board. So might have to keep that in mind....

33 minutes ago, klipsch said:

I'd recommend the $30 JBL driver under your couch/sofa as another option worth perusing. Being across the pond, not sure if you have access to that driver and/or at that price, but many use them on avsforum. Think they call it BOSS setup or something similar.  

 

Edit: it is indeed boss - back open sub shaker on AVS 

I will check it out. That seems like another good option.

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I second the BOSS idea, I have tried it and it's really nice. You can build one in a way that it only elevates your seating by an inch if you want to keep it low profile. It won't make any noise, but will greatly enhance your bass 'perception'.

Mounting drivers to your walls is a bad idea, as the vibrations will transmit through them (unless they're infinitely stiff) and probably still end up disturbing others. De-coupling your sub from the floor with a rubber mat or foam works wonders sometimes too.

I used two jbl stage 1210 in my BOSS build.

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12 hours ago, peniku8 said:

I second the BOSS idea, I have tried it and it's really nice. You can build one in a way that it only elevates your seating by an inch if you want to keep it low profile. It won't make any noise, but will greatly enhance your bass 'perception'.

Mounting drivers to your walls is a bad idea, as the vibrations will transmit through them (unless they're infinitely stiff) and probably still end up disturbing others. De-coupling your sub from the floor with a rubber mat or foam works wonders sometimes too.

I used two jbl stage 1210 in my BOSS build.

While this forum this seems to cater to subwoofers for pro-use, folks have been very helpfull and welcoming. Much appreciated.

You have a build somewhere on another forum? I tried to decouple the subs but since my whole backwall is open(and second floor), it did not help much. 

This also makes it  very hard to really pressurise it properly. The sealed Faitals do a good job, but it still lacks that "chest compression". That said I am still learning about EQ and setup so that might also be apart of it. I first.

I usually do not listen very loudly, so this Boss platform seems very promising for not much money.

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5 hours ago, Poleepkwa said:

While this forum this seems to cater to subwoofers for pro-use, folks have been very helpfull and welcoming. Much appreciated.

You have a build somewhere on another forum? I tried to decouple the subs but since my whole backwall is open(and second floor), it did not help much. 

This also makes it  very hard to really pressurise it properly. The sealed Faitals do a good job, but it still lacks that "chest compression". That said I am still learning about EQ and setup so that might also be apart of it. I first.

I usually do not listen very loudly, so this Boss platform seems very promising for not much money.

I posted a few pics somewhere in this thread, but you'll find all the information you'll need in there anyways:

https://www.avsforum.com/threads/the-hideaway-theater.2991522/

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  • 2 months later...
On 1/1/2022 at 10:32 AM, tktran303 said:

Add first and then subtract later. Or subtract first then add later. It’s all the same in terms of maths.

 

for a commercial product that you were trying to sell you probably do want to show that it has good bass response and works well in many rooms so you’ll probably need to boost 1st to target your Anechoic response (-3dB/-6dB/-10dB) etc. and allow user to EQ for good in-room smooth bass response. 
 

For your own use no need to worry about that. Just plonk it in for desired room; take measurements at the listening position and EQ it to your taste.

This has been a interesting experiment.

I have tried both.

On 12/27/2021 at 7:59 PM, Ricci said:

You can use an LT circuit for this or regular dsp EQ filters. 

You will need to be able to take measurements of the subwoofer in order to develop EQ that modifies the response in the manner you want. Without measurements of the sub you are somewhat shooting in the dark. You can use simulations of the sub system to develop EQ but this will usually be in the ballpark only. 

Also keep in mind that EQ for flat response outside will often result in excessively boosted low end once the sub is placed in a room. Again measurements of the sub in room help a lot. 

If you want to play around with filters REW is free and has a robust EQ function, plus the ability to take measurements of course. 

I have now tried both ways.

- use LT to extend low-end and use PEQ to flatten response. ( boosting and cutting)

- no LT and PEQ to flatten the response. (just cutting).

Strangely enough they sound a bit different! 

After pondering about it a bit I realised that it could be the Q of the subs. My current Q according to the simulator is 0.5.

used the LT is set it to 0.707. and 20hz.

Could this be the reason that (even with EQ and similar frequency response) it sounds different? 

The 0.5 seems drier and faster than the 0.707 alignment.

It seems that  the LT is usually used to lower the frequency response AND lower the Q of a subwoofer in a too small box. 

 

Currently I am increasing the Q instead of lowering it. ( Some other people that have the same elements have increased the Q even more)

Does it make any sense to use a LT if the element it is optimal sizes sealed case?

 

 

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