When does a sealed sub mimic IB?

[kramskoi]

For all who've heard critical Q subs and IB setups...what are some differences between typical IB installations and low Q sealed subs, in regards to sound signature? Why would a ELQ sub (<.4 Qtc.) not sound similar to an IB installation, given extreme cabinet bracing?

[Scott Simonian]

Dunno. I think its the fact that in a "true IB" the owner knows that there is no restoring force on the sub other than what the coil sees. That's just my take on it.

Personally, I would love to have a quadruple stack of your TC3000s in that Q5 box. With a EP2500 strapped to each coil. Cause, why the phuck not?

Ah....eight TC-3000s.....

*Homer Simpson drool*

Actually, I think 4 or more 18" LMS-5400s would pretty much tap me out! :E

[ThomasW]

It's not just the "Q", it's the lack of the interaction with the box that gives an IB the edge with regard to SQ.

[kramskoi]

Dunno. I think its the fact that in a "true IB" the owner knows that there is no restoring force on the sub other than what the coil sees. That's just my take on it.

Personally, I would love to have a quadruple stack of your TC3000s in that Q5 box. With a EP2500 strapped to each coil. Cause, why the phuck not?

Ah....eight TC-3000s.....

*Homer Simpson drool*

Actually, I think 4 or more 18" LMS-5400s would pretty much tap me out! :E

i'm seriously thinking about adding a second 2x15 unit like kgveteran...most likely i'll just add a third tc3000 in a single box with a lower Qtc. of .3-.4...this should pull up 7-8 Hz a bit more... :T...as is, the 8 Hz signal in "Irene" is definitely felt with this sub...

[Dennis H]

Assuming the box is totally rigid and not radiating, one difference is air spring distortion. According to SL's worksheet:

(Air spring distortion %) = 140 * (driver 1-way Vd) / (box volume)

Another is the non-linearities due to heating etc. that drivers experience when you pump a lot of power into them. If you have a small box with a lot of EQ on the low end, it's going to take a lot of power down low.

[Mark Seaton]

For all who've heard critical Q subs and IB setups...what are some differences between typical IB installations and low Q sealed subs, in regards to sound signature? Why would a ELQ sub (<.4 Qtc.) not sound similar to an IB installation, given extreme cabinet bracing?

Everyone has their own perspective on the matter, but there are a variety of factors that sneak into contribution that are often ignored. As Dennis mentioned, heat from current through the VC will obviously be greater for a less efficient subwoofer. The part that is often overlooked or forgotten is that the current through the VC for a given Voltage input is highly dependent on the impedance curve of the driver. While I personally tend to think that with many of the high excursion woofers too much concern is given to box Q since the Le and other factors skew the response from a simple 2nd order high pass, there is an interesting quality that is consistent is the relative changes in the impedance curve with lower Q and higher motor strength systems. While the lower Q systems are not quite as sensitive (to Voltage) as higher Q systems, either or both of the peak and width of the impedance peak at Fb increase vs higher Q and/or lower motor strength systems.

If the impedance is higher at a given frequency, less current flows through the coil, and heat in a motor can only come from I^2*R where R = Rdc.

If you take a look at a few preferred IB solutions you might notice some trends related to this. :roll: