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Discussion Starter · #1 ·
hi how do you model a push pull in winIDS isobarik ? I'm finding my twin 40 liter sealed subs very boomey and over powering. so now im considering a push pull with using one amp my room is small so 380 wrms will be more than enough power any input would be gratefully received cheers andy
 

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Elite Shackster
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Re: 175 litres - dual AV15X Push Pull Backfiring Sub

What drivers are you using. Even most 12" drivers would find 40 litres pushing the QTC of the sub up. What is the QTC of our sub in its model. To model a push pull you simply need to model a sealed sub using 2 drivers, isobaric is a different alignment that allows you to make a sub in a much smaller cabinet, but at the expense of some spl performance.
 

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Discussion Starter · #3 ·
Re: 175 litres - dual AV15X Push Pull Backfiring Sub

305mm aluminium cone

Fs: 24.85Hz
Qms: 6.46
Qes: .486
Qts: ..452
Vas: 48.44 L
Re: 2.79 ohm
Z: 4 ohm
(dual 2ohm)
BL: 16.04 Tm
Cms: .143 mm/N
Mms: 286.8g
Rms: 6. 937kg/s
Le: 2.95mH
Pe: 500W cont.
2.83V: 88.42dB
Xmax: 23 mm
Xsus: 30 mm
Sd: 498 sq cm
Vd: 2.33 L
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I don't get why you want isobaric. All it does is reduce the box size, halve output and efficiency. The basic FR will be the same as what you have now. You already have a very small box for the AV15X; Qt = 0.82.

You really need to do some measuring to get to the cause of the 'boominess' before you start looking for solutions.

What do you mean by 'backfiring'?

Going to work. Will model isobaric later for you if you want.
 

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Discussion Starter · #5 ·
I think things have been confused I have a pair of av 12's each in a 40l sealed box the sit one on top of the other I'm the corner of the room behind the tv this is the only wife approved space in the room I am finding them very boomey. So I'm considering a push pull in a 80 liter sealed box
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Elite Shackster
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I havent modelled these drivers specifically, but a QTC above .7 in a sealed sub will lead to a boomy sound from someone who like very clean tight bass.

Have you run a model for your drivers, or did you just guess the 40 litres? If you did model them, take another look at it and check out the QTC, higher than .7 can sound boomy, while lower will sound deeper and cleaner. .7 is the best all round.

I'll run a model myself when I have a few spare minutes, I'm off to a mates to do a bit of an install in a moment. If you have had no luck looking at the model yourself, I'll do it for you and give you some ideas on alignment and cabinet volume. Again, to model a PP sub, just use a sealed cabinet with 2 drivers, and you required input power. Also, dont forget that with a single amp and 4 ohm drivers, the load of a push pull sub will be either 2 ohms or 8 ohms.
 

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Discussion Starter · #7 ·
40 liters has a qtc of About 6 with the av 12 drivers if you could model it would be a grate help just to compare results. So would a push pull need 80 between the drivers or more cheers for you help andy
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Elite Shackster
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Are you sure you modeled with 2 drivers. A QTC of .6 sounds low for a dual driver setup in a 40 liter cab, although I'll have to check that one (I'm still out out on the install :D). A .6 QTC should be leaning to the deeper cleaner sound, so if your QTC is correct then a boomy sound is likely down to either room position or a response issue that needs some eq'ing.

I'll run a model ASAP and confirm the QTC is correct, and move from there.
 

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Discussion Starter · #11 ·
The oaudio amps I have have a room mode feature so I will have a play and get back to you. I have a massive peak around 48hz which needs taming.
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Elite Shackster
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48hz is very audible, and if you have a massive peak there then I would single that out as your biggest issue.
 

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Elite Shackster
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Sorry there are two cabs 40 liters each
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That sounds a little more like it. As we have said, the issue does not look like it is one of your build. The best advice now is to look into REW and room eq, that is likely the best solution to the problem your having, as well as being much easier than rebuilding a sub.

If you were to build an 80litre push pull sub now, you are still going to have a boomy sound, and possible slightly more as I feel push pull adds authority and impact. EQ'ing is an essential part of getting any high end sub(s) to sound right, and that should be your next step.

If you need help with any of that, the best thing to do is start a thread in the REW forum and we'll help you from there :T.

Drop a link if you do that, it'll be easier for us to keep track.
 

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Discussion Starter · #15 · (Edited)
a single sub in a 1.7cu ft / 48 liters sorry not 40 has a qtc of 0.659 and an fs of 36.5
i can only have the in the wife approved location in the corner. i now have one facing along the wall parallel with the tv and one at 90 deg facing towards the sofa. with the eq on my amps i have -12dB at 50hz with the hi low Q in the middle so far so good here is what it looks like with no smoothing.
i can now tune the subs up to mach the rest of the system is the any rules for this or is it do by ear?
 

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Andy,

Set the graph scale to logarithmic and a range of 15-200hz. Also set the overall spl range to 45-105db or some other variation that results in a total SPL range of 60db.
 
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