Advantages/Disadvantages of bigger than recommended box

[stratusrt01 10+ year member]

I want to build a sealed enclosure for my MTX 9512-44 and the recommended enclosure size is 1-1.5 cf. I want to build a box that is 1.7 cf net. What are the advantages or disadvantages of building it a little larger than recommended?

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[Defconx3 10+ year member]

Since it isnt that much larger you should be fine. Heres the advantages / disadvantages in a nutshell:

Advantages: Less power needed to reach max excursion, louder sound

Disadvantages: Transistant responce suffers, aka boomier sound, if you are using too much power you can bottom out the sub's suspension.

 

[JimJ 5,000+ posts]

Since it isnt that much larger you should be fine. Heres the advantages / disadvantages in a nutshell:
Advantages: Less power needed to reach max excursion, louder sound

Disadvantages: Transistant responce suffers, aka boomier sound, if you are using too much power you can bottom out the sub's suspension.

Transient response gets better in a larger-than-recommended sealed enclosure, that's why IB setups are ideally suited for SQ...

And overall SPL drops as volume increases...

 

[stratusrt01 10+ year member]

Well, the sub is 1000 watts rms, and I'm hitting it with 1200 rms. Think I'll have a problem bottoming it out? I could always just add a couple small plates inside to bring the airspace down. I'm actually looking more towards more SQ, hence building a sealed box.

 

[stratusrt01 10+ year member]

....and since it's bigger than recommended, is there any need for polyfill?

 

[JimJ 5,000+ posts]

Polyfill would make it seem even larger...

I would probably stick to the recommended size if you're running that amount of power to it.

 

[Rattlebrain 10+ year member]

Thread jack!

Something I have been wondering about for a while....

HYPOTHETICAL: Sealed box

Say I have a 12" mid to higher end sub. Brand not necessary to my question. The builder recommends 1 cu. but you can build a box up to 7 cu. If high SPL is not your goal but you still would like a little volume there, could you use all 7? What would it do for output, SQ, power handling. For example, the subs RMS is 300 and your amp matches that, would you have to turn the gains down to match a lower power or will the sub still handle the whole 300. What would be a good rule of thumb to use to make sure you get the best out of you equipment?

Hope that makes sense.

 

[CBFryman2 5,000+ posts]

Depending on the subs Vas, once compliance of the subs enclosure reaches that of the drivers Vas the sub essentially becomes IB

 

[Rattlebrain 10+ year member]

Depending on the subs Vas, once compliance of the subs enclosure reaches that of the drivers Vas the sub essentially becomes IB

Thanks for the reply but that only answers part of the ??

Anyone else want to elaborate?

I would really like to know because if it would be beneficial to SQ, I was thinking of using a 12" or 15" in a 5-6 cu box sealed. Sub yet to be determined. Possibly a Sound Splinter, just dont know yet.

 

[squeak9798 5,000+ posts]

Depending on the subs Vas, once compliance of the subs enclosure reaches that of the drivers Vas the sub essentially becomes IB

There's differing opinions on this.

Some say a subwoofer/speaker is effectively IB when the volume of the enclosure is 3x Vas, while others say a subwoofer/speaker is effectively IB when the volume of the enclosure is 4x - 10x Vas. Others will tell you that "true" IB is when the Qtc is extremely close to Qts....and if you've ever modeled a subwoofer to try to create this effect....most subwoofers will need close to or over 1000ft^3 to even approach this limit. Because anywhere below this point, the enclosure is still having acoustic-suspension effects on the driver (as evidenced by the increased Qtc).......and many people would not consider that to be "true" infinite baffle.

 

[squeak9798 5,000+ posts]

Thread jack!
Something I have been wondering about for a while....

HYPOTHETICAL: Sealed box

Say I have a 12" mid to higher end sub. Brand not necessary to my question. The builder recommends 1 cu. but you can build a box up to 7 cu. If high SPL is not your goal but you still would like a little volume there, could you use all 7?

If you wanted to, yes.

What would it do for output,

Decrease peak SPL, but increase the output in the low end.

SQ,

Well, that would really be up to whether or not you enjoyed the sound of the resulting Qtc. Group delay would improve and overhang/ringing would decrease.

power handling.

Substantially decreased.

For example, the subs RMS is 300 and your amp matches that, would you have to turn the gains down to match a lower power or will the sub still handle the whole 300.

You would need to decrease the power output of the amplifier.

Chances are very high that the woofer would bottom out with that much power.

Just for an example....in "infinite baffle", most subs can only mechanically handle ~ 50% (or less) of their rated RMS power.

 

[CBFryman2 5,000+ posts]

Basically larger box = lower over all system compliance. Lower Qtc (overall compliance, i think that is what Qtc is) the flatter the responce curve anecho which means more low end output, less peaks, but also quieter. Also, the larger the volume the lower mechanical powerhandleing becomes.

In non audiophile terms, Large = Flatter and a tad quieter with less power handleing mechanically (means it will bottom out sooner) Small = Peaky, tad louder in certian ranges, greater mechanical powerhandleing (means it takes mroe power to bottom out the driver).

Because low end extension in an acoustic suspensionand IB set up is completel reliant on excursion, too large of a box wont be as loud as it potentially could be and your driver may bottom out on the lower notes where it wont on the higher notes and also wont be satisfyingly loud on the higher notes as well.

However, transient responce improves which means SQ improves slightly in all real music types (not monotone beats) and the responce curve is flatter.

Basically

Anal SQ Audiophiles = Large sealed/IB

SQ audiophiles = medium to small sealed

Almost everyone else = Ported/4th Order Bandpass

Thoes with room and Knowledge who dont even toil in CA.com except when bored = Transmission lines, Horns, 6th order bandpass, Excetera

 

[CBFryman2 5,000+ posts]

didnt even notice you already covered it squeak...oh well

 

[Dante 10+ year member]

same applies to vented enclosures?