the PowerPouf, dual opposed sealed footrest sub.

I have designed and am in the process of gathering the materials for my WAF friendly Pouf subwoofer.

This will be a dual opposed 12" sealed, passive sub, DO mainly because i don't want vibrations in my feet or cabinet vibrations traveling to my neighbors.
I got a deal on 2 lightly used (allegedly) Eminence LAB12 drivers, so those are locked.

I modeled the design in 3D and adjusted the size of the box to end up around 85L netto using boxNotes, which gives a Qtc of 0.76 in WinISD.
I end up having 35hz at -6db with I believe is fine for my hybrid HT living room.

I will be building the box myself, but the upholstry is something I may be getting a professional to do, as it is outside my comfort zone.

I am eyeing a pretty good deal on a Lab Gruppen IPD 2400 amp, but am having a couple reservations I'm hoping someone here can help me clear up before I buy it.
Lab Gruppen IPD 2400

The drivers are 6 ohms and asks for 400W RMS, (800W max) efficiency is 89.2db.
The amp is 2 channel and can provide Max output power (per channel)
2 ohms - 800W, 4 ohms - 1200W, 8 ohms - 600W, 16 ohms - 300W.

The amp does not appear to have a bridge mode, which is a bit unfortunate.

Because of that I am considering a way to wiring them up which i'm unsure if its at all a good idea:

Connect the receiver (Marantz SR7013) from
LFE1-out to IPD2400 channel1-in then channel1 to LAB12(driver A).
LFE2-out to IPD2400 channel2-in then channel2 to LAB12(driver B).
This means that the drivers will not be connected either in parallel or serial but utilize that I have 2 LFE outputs. If I need to indicate impedance on the amp I would set it to 4 and probably end up around 800W max per driver.

This way I'm assuming that I'm getting something similar to a mono signal but using both channels in the amp.

The question is then if the balance is maintained and the benefit of DO reduced vibrations is compromised, can I count on both the receiver and amp to get the signal through without the slightest variation?

If I end up having to connect the drivers in serial or parallel, I will likely need to choose a different amp.

I've attached my 3D drawing of the design and an exploded view.
The transparent designs are only size comparisons to commercial Poufs that are wife approved.

As this is my first sub build I'd greatly appreciate if anyone sees anything I should consider before I start building!
I'm a bit unsure if I need any damping inside, whats the consensus on that?

Cheers
Andreas
 

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SpeakerBob

Member
2002-08-15 6:21 pm
UK
A pair in the box specified hit xmax at 30Hz with around 540 watts wired in parallel. I'd just use one channel of the amp.

The amp specs look weird to me. Usually the 2 ohm rating will be higher than the 4 ohm rating.

I always put a bit of damping in my sealed sub boxes in case there are any higher frequency noises generated by the suspension etc.. Can't prove it either way myself but to me its good insurance.

Rob.
 
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Thanks for the replies!
I'll be sure to add a bit of damping in there.

So i gather that splitting it in both channels is a bad idea, gotcha.
Just out of curiosity, should I try it and see if my idea works, or could I end up frying something?

Running them in parallel would end up with a 12 ohms resistance, I figure using only 1 channel I would end up getting max ~400W, I supposed for my purpose that would be enough.

looking at spl in WinISD, the curve looks flatter if I run it in 3ohm (serial), could that be preferable if the output isn't limited too bad?

Cheers!
 
You can run that amp if you want, as you wish, but it is really overkill. You just won't use all of the power and the amplifier will have plenty of headroom and potential should you ever change your sub design.

In parallel, your dual 6 ohm drivers will run a 3 ohm impedance, not 12. (12 ohms would be the pair run in series.) As you run it dual-channel, the channels will see 6 ohms each. The LFE2 preamp output might be a redundancy if the LabGruppen amp is able to be set as single-input/dual-output and run the same input to both channels. On my Crown, the setting is call 'Y-Input', and it is nice to have the option.

A little stuffing never hurts, IMO, and that will be a HEAVY Ottoman. You might want casters installed to wheel it around easily.

Later,
Wolf
 
Thanks for the correction Wolf, I got that reversed!

It sounds to me like I'd not utilize the second channel of that amp, and while the deal was quite good, I can probably find another amp that will do the job for a little less.
I've spotted a used Crown Xti 1002 for just a bit less, that should have bridge mode and should be of a decent quality, wouldn't you agree?
I honestly don't think I would ever find a use for that extra channel in the IPD2400.

As for the weight, I actually like that it's quite heavy, so it doesn't slide around. I can put some felt on top of the rubber feet so I can "easily" slide it around on our varnished wooden floors.
 

scholl

Member
2012-12-30 5:07 pm
Certainly a worthy project.

Keep in mind with an opposed design the frequency response starts to comb filter at the 1/4 wavelength of the driver distance. That's not much if any of a problem if it's played below 80hz.

If the IPD2400 is a very good deal, get it. build or buy a "y" cord to drive both channels with the same preamp. With subs a little too much isn't so bad and sometimes a person just has to take a good deal when it comes along.
 
Certainly a worthy project.

Keep in mind with an opposed design the frequency response starts to comb filter at the 1/4 wavelength of the driver distance. That's not much if any of a problem if it's played below 80hz.

If the IPD2400 is a very good deal, get it. build or buy a "y" cord to drive both channels with the same preamp. With subs a little too much isn't so bad and sometimes a person just has to take a good deal when it comes along.

Thanks for the heads up, I suspect I will end up crossing it over around 80hz.
My system is currently a 5.0.4.
Receiver: Marantz 7013
Front L+R: Quad Z4
Center: Quad ZC
Surr: Z1
Heights: DIY DML plywood panels.

The fronts cover down to 40-ish but not with much kick, i'm sure they appreciate not having to go there.

I read the comb filtering issue is also dependent on distance, so perhaps it's less of an issue when the PowerPouf would function a bit like a near field sub, my feet will literally be on it.

Regarding a Y-splitter, that will not address the issue of the amp only using 1 channel.
I'm ok with the amp having plenty headroom and possibly run cooler, but if i'm only using 1 channel, will the amp simply count the unused channel as headroom? it's a class D, but I don't know much else about the internals of that amp.
Regarding choice of amp, in the end it will come down to what sounds best and output an ok spl. Price means something too, but i'm going to spend a lot of time building this thing, I don't want to skimp on the electronics.

I can get the IPD2400 2nd hand for 680 USD / 600 Euro.
I can get the Crown iXT 1002 2nd hand for 330 USD / 300 Euro.
What would you pick?

I have a Umik-1, so i'll post some measurements when I get that far, it may take a month or two though.

Cheers
Andreas
 
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scholl

Member
2012-12-30 5:07 pm
Thanks for the heads up, I suspect I will end up crossing it over around 80hz.
My system is currently a 5.0.4.
Receiver: Marantz 7013
Front L+R: Quad Z4
Center: Quad ZC
Surr: Z1
Heights: DIY DML plywood panels.

The fronts cover down to 40-ish but not with much kick, i'm sure they appreciate not having to go there.

I read the comb filtering issue is also dependent on distance, so perhaps it's less of an issue when the PowerPouf would function a bit like a near field sub, my feet will literally be on it.

Regarding a Y-splitter, that will not address the issue of the amp only using 1 channel.
I'm ok with the amp having plenty headroom and possibly run cooler, but if i'm only using 1 channel, will the amp simply count the unused channel as headroom? it's a class D, but I don't know much else about the internals of that amp.
Regarding choice of amp, in the end it will come down to what sounds best and output an ok spl. Price means something too, but i'm going to spend a lot of time building this thing, I don't want to skimp on the electronics.

I can get the IPD2400 2nd hand for 680 USD / 600 Euro.
I can get the Crown iXT 1002 2nd hand for 330 USD / 300 Euro.
What would you pick?

I have a Umik-1, so i'll post some measurements when I get that far, it may take a month or two though.

Cheers
Andreas

Depends on condition, If the Lap was beat up, I choose the Crown. Both being equal and I had the money, the Lab. I would use both channels either way. One for each woofer. I'd make it work, That's what I do now. Use a balanced "Y" cable from the crossover out to a big Crest amp.
 
Your room looks like you live in a Copenhagen apartment, so quite small room? Often they have soft walls making bass sound better than the old swedish concrete bunker apartments...

Having a subwoofer in the middle of a room can be difficult. Have you tested that 2x12" sealed gives you the SPL you are looking for? Wall placement vs middle of room placement are very different.
 
Hi Johnny, thanks for chiming in.

You are right, it's in Copenhagen, it's an appartment building from 2018, entirely concrete on outside walls, ply + drywall inside, including one wall next to the sofa. The appartment is 95 sqm with an L shaped space for kitchen, dining space and TV area.
The TV-area is 3 meter at the screen wall, 3.6M on the side and open at the back to dining+kitchen.

The good news is that the appartment is extremely well insulated, when neighbours or us have a loud party on occasion it it completely inaudible, but let's see if that hold with a sub in the mix :)

I am not looking for maximum SPL, just enough to give movies a solid bottom, and most of all WAF. I'm hoping the fact that it will be near-field will reduce the need for precision placement, I could be wrong though. One driver will be aimed directly at the well polstered leather couch, I'm guessing that will dampen one side quite a bit, it'll be interesting to see what that means over all.

The amp I got has some nice DSP built in, so I should be able to compensate for some of the issues I'm inviting.

Yeah, lot's of guesswork and wishful thinking, It may just end up being an expensive learning experience, I wont know until I try, right!

Cheers
 
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I finally finished the Powerpouf, and i'm quite pleased with the appearance and sound.

This post has the box build, next post will have some upholstry pics and a REW measurement (var smoothing).
 

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Upholstry and a measurement. Room has a mode at 37, I can't really fix it with DSP and moving the pouf is obv. not an option. It does still sound very nice, not boomy but punchy when it needs to, it's mostly used for films.

feel free to ask questions.
 

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