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View Full Version : Help to find out tuning freq for 2 subs

Beginer
04-30-2007, 11:28 AM
Hello,

Some months ago I made box for ONE (1) Type R subwoofer.
Net Volume: 3cu.ft
Tuning Freq: 30Hz
Port Width: 3.25 inch
Port Area: 40.625 square inch
Port Length: 35.25 inch
http://i47.photobucket.com/albums/f200/Scarrell/boxdims.jpg

Now I want to put TWO (2) Type R subwoofers to same box.

So how can I calculate what will be tuning freq with two Type R's in this box?
Port width, area, length will be same.

It would be great if you could explain how to calculate that tuning freq :)

Thanks.

MikeNeufeld
04-30-2007, 11:39 AM
2.0-2.5 per 12 @ 33hz would be good...

profundus-sanus
04-30-2007, 11:43 AM
so you want to put 2 type-r's in the same box that you had one type-r in?

So basically the only thing that would be different is the .071 displacement of the second sub.

Comes out to [email protected] Your initial calculations were a little off or something.

Immacomputer
04-30-2007, 11:44 AM
2.8 @ 31hz.

The enclosure's tuning frequency is based on the port area, length, and net volume. The only thing that changes when you add the second sub is the net volume and by a very small amount.

That enclosure is probably going to lose a little bit of low end and get peaky around 40hz with two subs in it.

Mr Cabinetry
04-30-2007, 11:46 AM
The minor displacement of the subwoofer added to the enclosure isn't going to effect the port tuning to any great degree that you would notice it.

Decipha
04-30-2007, 11:51 AM
you will notice that the box lacks the low end it once had though... new box time

Beginer
04-30-2007, 11:53 AM
so you want to put 2 type-r's in the same box that you had one type-r in?

So basically the only thing that would be different is the .071 displacement of the second sub.

Comes out to [email protected] Your initial calculations were a little off or something.

Yes I want to put 2 Type r's 12" to same box.

Mr Cabinetry
04-30-2007, 11:58 AM
you will notice that the box lacks the low end it once had though... new box time

WHAT!!!! That's a load of nonsense.

He'll still have the low end he had before, the addition of the second subwoofer ain't changing the port tuning to any great difference of increase.

Add the second subwoofer and see how it sounds, then decide for yourself if building a new enclosure is worth the effort, just don't go building a new enclosure thinking that it's going to change any of the bass/performance response from what you have presently.

almond
04-30-2007, 12:01 PM
mainly because now two subs are sharing the "3" cubes instead of one in three cubes. take 1 sub in three cubes and one in 1.5 and see how different they sound. i'm not saying it will lose or gain anything, just that it might sound different and you might not like it. or on the other hand you might love it. personally i would build a new box.

Mr Cabinetry
04-30-2007, 12:06 PM
mainly because now two subs are sharing the "3" cubes instead of one in three cubes. take 1 sub in three cubes and one in 1.5 and see how different they sound. i'm not saying it will lose or gain anything, just that it might sound different and you might not like it. or on the other hand you might love it. personally i would build a new box.

OK, in that I would agree 100% given the volume is now split for two sub's and the output is definitely going to increase along with the F3 of the sub/enclosure.

Beginer
04-30-2007, 12:10 PM
you will notice that the box lacks the low end it once had though... new box time

Well I could agree with you. I will lose low notes. So this mean that box will be tuned higher. This is what I'm seeking. I want to make SPL box :)
It was SQ box because was tuned low and was playing low notes. And if I put second subwoofer I will lose low notes. If I lose low notes it will mean that box tuned higher. Agree?

But I don't believe that tuning freq will increase only to 31Hz...

Are you guys sure that only subwoofer dispacement will affect tuning freq?

Mr Cabinetry
04-30-2007, 12:13 PM
Well I could agree with you. I will lose low notes. So this mean that box will be tuned higher. This is what I'm seeking. I want to make SPL box :)
It was SQ box because was tuned low and was playing low notes. And if I put second subwoofer I will lose low notes. If I lose low notes it will mean that box tuned higher. Agree?

But I don't believe that tuning freq will increase only to 31Hz...

Are you guys sure that only subwoofer dispacement will affect tuning freq?

The port tuning is effected by the Net Volume, Sub Displacement, Port Size and Length, plus any other displacements = Port Tuning.

Change any of these and your port tuning changes, by how much depends on which program you used to design the enclosure to get the spec's.

almond
04-30-2007, 12:17 PM
your tuning will still stay the same, but your frequency response will change. 3 cubes at 30 hz will have a different responce than 1.5 cubes at 30hz. it depends on the sub. try playing with winisd to see how the different volumes affect the response curve.

profundus-sanus
04-30-2007, 12:18 PM
the box won't be tuned higher but it will probably peak higher because of the smaller port gain(which is centered at tuning frequency) of 1.5 per sub instead of 3 per sub.

You probably will lose some low end, but you'll also probably get a flatter response than before as well.

Mr Cabinetry
04-30-2007, 12:23 PM
Yeah, but he's not going to lose enough low end that he'll notice it and as for a slight high peak, of course he's going to get a dB gain just by adding a second sub.

Beginer
04-30-2007, 12:28 PM
your tuning will still stay the same, but your frequency response will change. 3 cubes at 30 hz will have a different responce than 1.5 cubes at 30hz. it depends on the sub. try playing with winisd to see how the different volumes affect the response curve.

Well tryed to play with WinISD.
And if I set 3cu.ft box with 30Hz tuning and ONE sub. So peak is at ~32-33Hz.
And if I set 3cu.ft. box with 30Hz tuning and TWO subs. So peak is at ~44-45Hz.

So if I get peak at higher frequency this don't mean that tuning freq is higher? :confused:

Because I played with WinISD and before and noticed that peak is ~3-6Hz higher than tuning freq. If box is tuned to 40Hz so peak is at ~43-46Hz.

Mr Cabinetry
04-30-2007, 12:31 PM
Well tryed to play with WinISD.
And if I set 3cu.ft box with 30Hz tuning and ONE sub. So peak is at ~32-33Hz.
And if I set 3cu.ft. box with 30Hz tuning and TWO subs. So peak is at ~44-45Hz.

So if I get peak at higher frequency this don't mean that tuning freq is higher? :confused:

Because I played with WinISD and before and noticed that peak is ~3-6Hz higher than tuning freq. If box is tuned to 40Hz so peak is at ~43-46Hz.

NO, it just means that you dB response increased, but, that will be effected as well by the cabin gain frequency of the vehicle as well,however, since your looking to increase the SPL response, you just might like the end result.

Keep in mind that were talking in generalizations here as to what is going to occur, the true measure will be cut for the second sub, mount it and stick it in the vehicle and then determine the result for yourself.

Beginer
04-30-2007, 12:57 PM
So tuning freq will be the same. Understood.

With two subs dB response increase and peak will be at ~44Hz(with one sub at ~33Hz) by WinISD curve.

Ok. Let's say I will play 44Hz tone.

And let's say we have two boxes:
1st. 3cu.ft tuned to 30Hz with TWO subs
2nd. 3cu.ft tuned to 40Hz with ONE sub

So if we play 44Hz tone with 1st and 2nd box, we will get more dB's with 2nd box right? :confused:

Sorry that I'm asking so much, just trying to understand everything :)

Mr Cabinetry
04-30-2007, 01:11 PM
So tuning freq will be the same. Understood.

With two subs dB response increase and peak will be at ~44Hz(with one sub at ~33Hz) by WinISD curve.

Ok. Let's say I will play 44Hz tone.

And let's say we have two boxes:
1st. 3cu.ft tuned to 30Hz with TWO subs
2nd. 3cu.ft tuned to 40Hz with ONE sub

So if we play 44Hz tone with 1st and 2nd box, we will get more dB's with 2nd box right? :confused:

Sorry that I'm asking so much, just trying to understand everything :)

Well, Naturally your going to get a given amount of db's increase if you up the port tuning, but only in terms of the peak response in vehicle.

SPL is going to increase as well and at what point it hits with a 44 hz test tone to the cabin gain frequency is where your going to hit at and if your aiming for the highest possible SPL/db gain, your going to need a meter to measure that to determine that if your goal is to compete.

He!!, I know someone that has been trying to break 150 for the pass couple of months and tired different enclosure's at different port tuning freq's using the combo of subs and amps and finally broke 150 yesterday using 2 subs and one amp.

So, it really all boils down to experimenting with the combination of subs/ enclosure design to find what your desired goal. Your not going to hit it first time right out the gate.

Beginer
04-30-2007, 01:30 PM
Yea I know that I need to experiment, but I think that then you know basics you can reach your goal easier.
He made 150dB with two Type R's?? :eek:

Mr Cabinetry
04-30-2007, 01:44 PM
Yea I know that I need to experiment, but I think that then you know basics you can reach your goal easier.
He made 150dB with two Type R's?? :eek:

No, he finally achieved that 150 mark with 2 SS -15's.

Yeah, sounds kinda lame that he only did 150 with 2- 15's, but, it took him sometime to get there and alot of trial and error.

Gettin to 150 ain't as easy as led to believe and every system, vehicle and install presents there own set of circumstances.

Who knows, you might break 150 with two 12's with alot of work and effort and alot of patience.

Immacomputer
04-30-2007, 05:43 PM
So tuning freq will be the same. Understood.

With two subs dB response increase and peak will be at ~44Hz(with one sub at ~33Hz) by WinISD curve.

Ok. Let's say I will play 44Hz tone.

And let's say we have two boxes:
1st. 3cu.ft tuned to 30Hz with TWO subs
2nd. 3cu.ft tuned to 40Hz with ONE sub

So if we play 44Hz tone with 1st and 2nd box, we will get more dB's with 2nd box right? :confused:

Sorry that I'm asking so much, just trying to understand everything :)

Your frequency response in a given enclosure will vary per sub. The tuning frequency is not based on the subs in the enclosure but by the nature of the enclosure itself.

Let me give you an example of something I did.

I used the same sub but different enclosures all tuned relatively close to each other.
Enclosure 1: 3 cubes tuned to 29hz
Enclosure 2: 2.2 cubes tuned to 32hz
Enclosure 3: 1.5 cubes tuned to 30hz.

Enclosure 1 frequency response: Peaked around 30-35hz with a loss in 60hz on up.
Enclosure 2 frequency response: Peaked around 33-40hz with loss from 80hz on up.
Enclosure 3 frequency response: Peaked around 37-45hz with a loss from 30-35 and no noticeable upper frequency extension loss.

Even though the enclosures' tunings were similar, the response was very different between each because of the net volume the sub was seeing.