3 chamber dual band pass enclosure! help !

[abhihemu]

Hi

i am new to the diy world, haven't done any diy yet. I have 2 Yugal 10" 8 Ohm, 120 watt woofers (my old amp plays them well on single channel in parallel config. so i will use them in parallel) :-

Qts:0.26
Vas: 290 liters
Fs: 30 Hz
Re: 4 ohm
Le: unknown
Xmax: 3 mm
Qms: unknown
Qes: 0.27
SPL: 94 dB
Dia: 10 inch

I want to make this type of Box for my woofers :-

ImageShack® - Online Photo and Video Hosting

and i have calculated this Box for me :-

ImageShack® - Online Photo and Video Hosting


as i am new to diy and electronics i don't know whether it will act as per my plans or not !! specially middle section of 80 Liters which i have tuned to 20Hz, i don't know it will produce 20Hz or not but i want to try it, WinISD is showing a Vent Match of 0.25 which is my cause to worry if i select 2 vents then WinISD doubles the port length !! please help me how to solve it !! other two chambers are i think good.

Please help me, this is my first Diy !
someone please correct the photo links !!

[Patrick Bateman]

Originally Posted by abhihemu

Hi

i am new to the diy world, haven't done any diy yet. I have 2 Yugal 10" 8 Ohm, 120 watt woofers (my old amp plays them well on single channel in parallel config. so i will use them in parallel) :-

Qts:0.26
Vas: 290 liters
Fs: 30 Hz
Re: 4 ohm
Le: unknown
Xmax: 3 mm
Qms: unknown
Qes: 0.27
SPL: 94 dB
Dia: 10 inch

I want to make this type of Box for my woofers :-
%20%20Uploaded%20with%20ImageShack.us[/IMG]
ImageShack® - Online Photo and Video Hosting

and i have calculated this Box for me :-
%20%20Uploaded%20with%20ImageShack.us[/IMG]
ImageShack® - Online Photo and Video Hosting


as i am new to diy and electronics i don't know whether it will act as per my plans or not !! specially middle section of 80 Liters which i have tuned to 20Hz, i don't know it will produce 20Hz or not but i want to try it, WinISD is showing a Vent Match of 0.25 which is my cause to worry if i select 2 vents then WinISD doubles the port length !! please help me how to solve it !! other two chambers are i think good.

Please help me, this is my first Diy !
someone please correct the photo links !!

It's very VERY difficult to get the tuning on a bandpass right unless you have a way to run an impedance sweep. And if you don't get the tuning right, the sub will sound all wrong. IMHO, this is the main reason that bandpass boxes have such a terrible reputation. If built correctly, they can sound very good, but they're easy to screw up.

If this is your first DIY project, I'd stick with a sealed box. Tapped horns are also less sensitive to mistakes because they're simpler than bandpass boxes. (In a bandpass box there are more variables than in a tapped horn.)

[head_unit]

Welcome abhihemu! Patrick is correct, it is quite difficult to get tuning correct on a bandpass. Bandpass enclosures purposely are very resonant, and so very sensitive to every dimension. If you build something within +-1mm of every dimension of your simulated box, it will never be exactly as simulated.

I can't comment more, because your images are blank-host is dead or something.

What are your goals for a subwoofer? Is there a certain size enclosure you want? What types of music do you listen to? How loud do you want to play (once in a while showing off, how loud really?)

And why did you choose a 3-chamber bandpass (again, I can't see your pictures so don't understand the actual design)

[col]

I think the image abhihemu is trying to put up is this one:



I recently built a 6th order bandpass that works quite well. I had a Woofer Tester 3 at hand though and was able to do the impedance sweeps and port tuning. This thread outlines my experience:

Help with 4th Order bandpass enclosure for a 15" 600W dual voice coil subwoofer (PA)

col.

[abhihemu]

Sorry for late reply ! my monitor fell down to the ground after posting this thread today got a new one.

Thanks for your replies !

@Patrick yeah i have heard it's hard to achieve the desired results in a bandpass, please tell me how should i tune the middle chamber to 20Hz, is it possible ?

@col yeah that's the same image... this is my plan -
ImageShack® - Online Photo and Video Hosting

@head_unit actually i want this box to play deep bass strokes and i usually listen music at 12 O'clock volume , but not more than it...can you guys suggest me any other type of enclosure for 20Hz to 60Hz+ tuning ?

[vacuphile]

20 Hz is not realistic with these drivers. 10 inch with 3 mm Xmax just will not pump enough air at that frequency.

The only possibility would be in a closed box with heavy compensation for the roll off at the low end, but you won't be able to play very loud without running out of Xmax. With a BR, you might get to the low 40's, but it would need a very large enclosure, using both speakers in one enclosure about 300 liters. It would be better to build two separate subs, though, because that would facilitate optimal room placement.

[mdocod]

Your picture is of a sort of quasai 6th order band pass, with a neat separate baffle loading idea (push pull or whatever it's called that should cancel out box vibration and give the drivers an effectively more rigid platform to work from). I would suggest turning the drivers around so they have their magnets pointed at eachother inside the center chamber, and installing a brace between the magnets of the 2 drivers (careful not to block a vented pole).

The idea of having the 2 outer boxes tuned differently whilst the drivers share a common loading on the the center box is something that I would not suggest dabling in. I'm not even sure if simulation software exists that wold support such a configuration.

Here's a hypothetical 6th order band pass box based on 2 of the drivers you have there....

As you can see, yes, you can tune to 20hz, 20ft^3 on the rear chamber is what it takes to make a 20hz tuning sort of practical/worthwhile for this box type.

As you can see, the design takes a hit on efficiency across the listening range (-6dB) but, if the driver characteristics are correct, the bass region can be produced relatively flat from 20-100hz with the box volumes and tuning shown.

Unfortunately, The Xmax limitation comes in with a vengeance at this point. Xmax limited to about 2W per driver, or about 4.1W total. (see sim).

If you simulate the ports with 4W of input, the port dimensions and air velocity are easy to make an acceptably quiet. (see sim)

At 4W, the system is theoretically good for ~100dB across the bass listening range. Nothing fantastic, but, not terrible either.

The odds of this simulation matching reality with those drivers; probably pretty poor.

The final chart on the right there, assumes no use below ~35hz, a still large but more practical box size, and an Xmax limited Pe of 13W instead of just 4W, the combined improvements in efficiency (+6dB) and Pe result in a full 10dB improvement in output capability.

Eric

[abhihemu]

Thanks for replying with sims mdocod !

One thing i am sorry for, all the driver details i given in my first post are true except Xmax and Fs (due to scratches in Fs and Xmax part on the back of my woofer), they were my guessings, perhaps Xmax would be double than what i stated i.e. 5mm as that driver sound very well and produces good bass with my 80 liter sealed box. I am new to such details but Xmech for that driver as i see would be 8-10mm. I thought (keeping 3mm Xmax in mind ) that single driver wont be enough for moving required air and so i planned two woofers having one common chamber, but after reading your post i took a visual test (as i am a newbie and cant test it through mic or such things) of that woofer playing in high volumes, now i think Xmax would be 5mm and Xmech would be 8-10mm. I will turn the magnets inside the middle chamber as you suggested. So if Xmax is 5mm than what effect it should have on sound quality ?

[abhihemu]

Is there any guideline for minimum required Xmax of a driver of a specific size i.e. 10"/12"/15" for an enclosure having specific volume ? should i buy any other driver which has sufficient Xmax for my planned box (same sized) ? if yes then what should be the minimum Xmax of that new driver ? please through some light on it...

[mdocod]

Box sizing is based on Qts and Vas. Xmax has nothing to do with it. Assuming your Xmax "guess" was off, then the simulations hold true minus the couple more dB that the Xmax will buy. If Fs was off, forget the sims, that changes everything.