18 replies to this topic

[islandman]

hello, this is my first post and i must say this board is exactly what i am looking for...one dedicated to audiopiles

i am wanting to purchase two 12" xxx subs to wire parallel/series to a final 2ohm mono load. They will be powered by an interfire ifh-2120 which will send 600w to each sub..lookin for excellent sq, that's why i am using this line of the RE subs.

the questions are, will i be safe using a 2.0 cu.ft box for these woofers.? they will be in seperate chambers...and should i be adding any polyfil to the enclosure?

thanks

[ultim8DTM5]

2.0cuft total or each?

[islandman]

my bad...that would be 2.0 cu.ft total. the subs will be in separate 1.0 cu.ft enclosures.

[ultim8DTM5]

Hmm I was playing with one of these some time ago although I had a box larger than that for one- different applications this was when I was toying with SPL.

If you want SQ I would do a lot of experimentation in box design- XXX's are known for their excursion abilities rather than their controlled suspension = tightness.

[HISPL]

I would reccomend a slightly larger enclosure.

You want to try to model your -3db point below 30hz.
Off the top of my head 1ft3 will not be big enough to get any sort of low frequency extension from them.

I thought the XXX had very stiff/controled suspension
I think you will find they have a relativly high resonant frequency and tuning to arround roughly 35hz will give you a decent sort of response.

You will find that a "tight" sound is achieved by putting the right woofer in the right box.

Install makes more of a difference most people think.

Woofers really don't sound like anything, woofers in the right box with the right power sound like something.

I would suggest that If you can get in touch with Don Hebig (He posts on Termpro and runs a company called Inhuman Audio in Canada)
he would be the man to ask about an enclosure design.
He is an RE Wholesaler and knows more about woofer enclosures than you can imagine.

[ultim8DTM5]

I was probably getting myself confused FUBman, the XXX in the wrong box is less forgiving than others due to its design- it can pound with the very best of them however overhang like hell!

[islandman]

my bad again......the enclosure will be sealed and not ported as some ppl might assume..

[Mr_Bob]

it behaves very similarly to a brahma.
i've modelled it in a 55-65L 23-26 Hz tuned boxes,
you need to be in that sorta region for it so sound good in a ported enclosure.

from memory it prefers smaller sealed boxes, but RE are good with their recommended enclosures, i'd expect it to sound best in a 0.7-1cuft enclosure.

[HISPL]

You can still tune sealed boxes,
If you plot them on a design program like WIN ISD it will still plot -3db point etc.

By changing the volume of the enclosure you can change the tuning.
Hope this helps.

[Bassaholic]

ultim8DTM5 said:

XXX's are known for their excursion abilities rather than their controlled suspension = tightness.

Rather than their controlled suspenson? Huh?

Firstly, the suspension is controlled. The cms IS linear over a long range. (longer than most subwoofers) That is controlled in my book.

The cone is controlled by the motor, the original and main reason for the suspension was simply to keep the cone/coil centred. The interesting thing about stiffening the suspension is, as the VAS goes down, the Fs and Qes go up, so the EBP (using the Qes) stays the same. The only real difference is the mechanical losses and since the VAS is lower, the box volume requirements for a given Qtc will be lowered. However, in the same volume enclosure, the frequency response will still be very similar, so realistically they will still sound similar.
(also, since the Fs and Qts are shifted upwards, a speaker with a stiffer suspension will be more suited to a infinite baffle situation, since the Fc and Qtc can't really be lower than the Fs and the Qts. Therefore the response will be relatively fixed regardless of the amount of volume behind the speaker)

Secondly, what do you mean by "tightness". If you mean, respond quickly to the signal (minimal overhang), then the goal is to have minimal voice coil inductance (relative to the dc resistance) including lowering the qtc at resonance. Of course the suspension has nothing to do with the voice coil inductance and the enclosure, the speakers other specs have a lot to do with the Qtc.
(practically however, the inductance really only has to be low enough so the subwoofer can cover the required bandwidth, which in a typical car audio installation does not extend all that high)

On the other hand, a lot of people seem to confuse frequency response with tightness and perceive that speakers that happen to play lower are less tight, when really all they are noticing is a lack of bandwidth.

What does all this mean? It means that the RE XXX has perfectly acceptable specs. There is no reason why it should "overhang like hell" unless there is something seriously wrong with the install...

A 12" RE XXX will have a Qtc of around 0.7 in a sealed box of around 1 cu/ft which is perfectly acceptable.

Remember that the location of the subwoofers is also important...

[DD]

go 2 cuft ported tuned to abotu 30 hz ..

[HISPL]

Yes, I would have to agree there.
The motor assembly on the XXX and MT woofers has been designed for maximum linear excursion.
A woofer with overhang (boomy sounding) is in the wrong box, unless you want it to sound like that.
I would like to see a nice little "bump" in the frequency response that drops off arround 28hz and peaks around 35hz.
I think that real low end response is important, after all it is a SUB woofer you are buying.
If you have a decent front end you could bandpass the subwoofer from 20hz to 60hz and

[Cyberpunky]

Use a devided box, as it has inherent advantages, one is that if a sub blows the other isnt presented with twice the volume. The other reason is it makes for a more rigid(better braced) box, which is always a good thing.

Forget polyfill as it literally does nothing, and cant do anything due to the physics of what happens at subbass freqs inside a box. Search richard clarks forum at carsound.com for more info.
peace
Cyberpunky

[ultim8DTM5]

Bassaholic- notice I corrected myself, this has been from my own testing and impressions of a XXX almost a year ago.

I apologise if my vocabulary isn't floating your boat.

[islandman]

thanks for all of the replies but i have decided to go with the idmax instead