SPL vs SQ vs Daily, motor/suspension cooling the works

[kryptonitewhite 1]

So I have been under the misconception that the main difference in build was spiders. I thought that the main difference between SPL subs and SQ subs was SPL had super tight multiple spiders, raising the Fs, raising power REQUIREMENT, where as SQ subs had 1 loose spider lowering the Fs and allowing the speaker to move easier reducing power "handling".

I am now learning I am WAY off. I thought SQ subs were most efficient, and SPL subs were super inefficient power hungry beasts wasting power.

So now I am hearing that... let's go with the Fi lineup for comparison:

I see the BTL on 1 end of the spectrum has the largest permenant magnet, a solid pole piece...no pole vent. I believe it has a smaller/narrower gap with less tollerance making it have even more metal, adding more power derived from the magnets, as well as the closer the gap is to the coil the least amount of flux lost?

On the opposite end, we have the IB3 series, very small magnet structure, thin top and bottom plates, and the least amount of metal in the pole piece, as the pole vent is MASSIVE. So it has less steel in the middle to "soak up" the ferrite's flux? Having torn mine open for a recone, I was very shocked to see that the gap is HUGE... the pole vent maye be pretty tight with the coil former, but on the outside of the voicecoil, theres a LOT of room.

So here's the next part that confuses me, that I want to learn about: first let me make sure I am accurate on a few things:

having a very large permenant magnet AND lots of metal, and a tight gap means more power, more efficiency, and more power HANDLING as well... but cooling becomes an issue.

Having less metal, larger pole vent, decreases efficiency, decreases BL, but increaes cooling... so less overall power handling, but handles things better for longer periods of time.

The burper handles lots more power but short term, the SQ takes less but for longer periods?

As well, I believe the BTL is 8 layer, where the IB3 is 2 layer.... so 4X's the windings also increasing windings in the gap, so increasing BL and efficiency, as well as handling more power.... the IB3 has less windings in the gap, less efficiency, less power handling, but probobly lower Le/inductance?

So now to bandwidth/inductance/Le (same thing?)

The SPL beast has longer coil, raising inductance, decreasing high end extention/bandwidth... more peaky responce.

The SQ has shorter coil, less inductance, smoother/flatter responce, higher extention, wider bandwidth???

If i am anywhere close with all of this, I wish I could have an IB3 but with a larger permenant magnet... tripple 12" slugs, and an 8 layer coil (maybe even 4" ) so that it handles more power, has more BL, but still has the vented pole piece for longer periods of time... still has 1 soft spider (if it could maintain linearity in an excursion fasion... no rocking issues, no scraping) so it still has a lower Fs (even lower with the heavier coil, but I assume the larger perm mag and more layers of coil increase the Fs again) and still has some efficiency with a loose suspension...

WOW I said a lot, and I hope I'm not too far off...

Edited March 26, 2009 by kryptonitewhite

[Adrian_D 520]

These assumptions about "SQ" subs and SPL subs are totally ridiculous.

There are far more things involved in a good sounding sub than a spider pack.

One more ridiculous thing : "power requierment". IMO no subwoofer requiers a certain amount of power "to get moving". Internet hype.

[kryptonitewhite 1]

These assumptions about "SQ" subs and SPL subs are totally ridiculous.

There are far more things involved in a good sounding sub than a spider pack.

One more ridiculous thing : "power requierment". IMO no subwoofer requiers a certain amount of power "to get moving". Internet hype.

I'm not sure using the word " ridiculous " is the best idea to help someone who is openly admiting they aren't sure, that they are ASKING... open about not knowing.

But anyway, since you must have a very good understanding about what I am asking, rather than just saying "NO, that is not correct" (which would have been a far better way to say it to begin with) how about tell me why. Explain to me how it really is.

That would be a very nice thing for you to do, in fact, I am of the obsured opinion that's what this forum is here for... someone asks a question, someone answers. If you don't have the answers, don't reply.

[diablo_331 23]

they tend to do that....

[Adrian_D 520]

My apologies, I missed this :

I am now learning I am WAY off

To my understanding, the ib3 was optimised for an ib application (yes, I know your thoughts on this) where an extremely strong motor and a high'ish fs isn't needed (you also reach mechanical limits before thermal limits, so no need for a coil that can handle gobs of power). And the btl was build to take some abuse, just why they were designed like they are.

One more thing about the btl motor is the fact that there are other cooling techniques. Venting the pole isn't the only cooling technique and, iirc, the bp power option consists in blocking the pole vent, to re-direct the air flow.

I probably didn't cover everything you asked. If there's more, be a tad more specific

[offtopic]

SQ refers to a style of competition. It is not a term to describe a good sounding subwoofer. Maybe it can describe a complete system (not just sub + amp + head unit).

[/offtopic]

[Adrian_D 520]

they tend to do that....

Yes I am an ass. Will I change for somebody that doesn't like me ? NO.

EDIT : Please don't label me.

[kryptonitewhite 1]

My apologies, I missed this :

I am now learning I am WAY off

To my understanding, the ib3 was optimised for an ib application (yes, I know your thoughts on this) where an extremely strong motor and a high'ish fs isn't needed (you also reach mechanical limits before thermal limits, so no need for a coil that can handle gobs of power). And the btl was build to take some abuse, just why they were designed like they are.

One more thing about the btl motor is the fact that there are other cooling techniques. Venting the pole isn't the only cooling technique and, iirc, the bp power option consists in blocking the pole vent, to re-direct the air flow.

I probably didn't cover everything you asked. If there's more, be a tad more specific

[offtopic]

SQ refers to a style of competition. It is not a term to describe a good sounding subwoofer. Maybe it can describe a complete system (not just sub + amp + head unit).

[/offtopic]

good info there, thanks Adrian

What would you think if they made a Q 22" and I dropped it in 18 cubes.... would you think the more balanced Q would have the push for a larger 22" sub with a large low Q enclosure?

[lithium 358]

i think only the bl and btl will have the 22 incher available

[DevilDriver 28]

having a very large permenant magnet AND lots of metal, and a tight gap means more power, more efficiency, and more power HANDLING as well... but cooling becomes an issue.

Having less metal, larger pole vent, decreases efficiency, decreases BL, but increaes cooling... so less overall power handling, but handles things better for longer periods of time.

The burper handles lots more power but short term, the SQ takes less but for longer periods?

Having a large magnet means you have a lot of potential flux in the system. You must have enough steel to carry the flux while still making sure the steel is saturated (ie. can't carry any more flux). Air has greater reluctance (resistance to carrying flux) than steel, so keeping the gap tight ensures you have the most flux possible in the gap (since the coil is closer to the steel). Any time you're able to increase BL, you're able to increase efficiency.

There is no strong correlation between the amount of magnetic material in the motor and the power handling of the driver (note that talking about power handling and cooling is essentially the same thing). The steel in the motor does play a role, but the dominant factor is always the coil. The goal is to get the heat off the coil; in the past, the idea has been to get as much air moving in the motor as possible, which is, in part, one of the reasons the pole vent has been used. In reality, we just need to get the heat off the coil, so moving it anywhere else will be useful. So instead, you have a lot of steel in the motor, add some copper or aluminum shorting rings, and design the motor such that air is drawn down into the top plate, over the windings, and then passing the heat into the shorting rings below the gap or into the steel above the gap. The pole vent is still useful for relieving pressure under the dustcap, but it is best to keep as much steel as possible, in my opinion.

Keep in mind that another dominant factor in efficiency is the mass that is being moved (Mms).

So now to bandwidth/inductance/Le (same thing?)

The SPL beast has longer coil, raising inductance, decreasing high end extention/bandwidth... more peaky responce.

The SQ has shorter coil, less inductance, smoother/flatter responce, higher extention, wider bandwidth???

The longer the coil, the greater the inductance. Since the inductance and resistance of the coil acts as a first-order (6 dB/octave) low-pass filter, it is preferable to have inductance that pushes the corner frequency (at which response begins to roll-off) above the bandwidth in which you'll be using the subwoofer. For SPL, you typically want a lot of windings in the gap (for both power handling and BL), so inductance is often higher.

[kryptonitewhite 1]

having a very large permenant magnet AND lots of metal, and a tight gap means more power, more efficiency, and more power HANDLING as well... but cooling becomes an issue.

Having less metal, larger pole vent, decreases efficiency, decreases BL, but increaes cooling... so less overall power handling, but handles things better for longer periods of time.

The burper handles lots more power but short term, the SQ takes less but for longer periods?

Having a large magnet means you have a lot of potential flux in the system. You must have enough steel to carry the flux while still making sure the steel is saturated (ie. can't carry any more flux). Air has greater reluctance (resistance to carrying flux) than steel, so keeping the gap tight ensures you have the most flux possible in the gap (since the coil is closer to the steel). Any time you're able to increase BL, you're able to increase efficiency.

There is no strong correlation between the amount of magnetic material in the motor and the power handling of the driver (note that talking about power handling and cooling is essentially the same thing). The steel in the motor does play a role, but the dominant factor is always the coil. The goal is to get the heat off the coil; in the past, the idea has been to get as much air moving in the motor as possible, which is, in part, one of the reasons the pole vent has been used. In reality, we just need to get the heat off the coil, so moving it anywhere else will be useful. So instead, you have a lot of steel in the motor, add some copper or aluminum shorting rings, and design the motor such that air is drawn down into the top plate, over the windings, and then passing the heat into the shorting rings below the gap or into the steel above the gap. The pole vent is still useful for relieving pressure under the dustcap, but it is best to keep as much steel as possible, in my opinion.

Keep in mind that another dominant factor in efficiency is the mass that is being moved (Mms).

So now to bandwidth/inductance/Le (same thing?)

The SPL beast has longer coil, raising inductance, decreasing high end extention/bandwidth... more peaky responce.

The SQ has shorter coil, less inductance, smoother/flatter responce, higher extention, wider bandwidth???

The longer the coil, the greater the inductance. Since the inductance and resistance of the coil acts as a first-order (6 dB/octave) low-pass filter, it is preferable to have inductance that pushes the corner frequency (at which response begins to roll-off) above the bandwidth in which you'll be using the subwoofer. For SPL, you typically want a lot of windings in the gap (for both power handling and BL), so inductance is often higher.

that was beautiful... exactly what i was looking for. Thank you Neil! I'm gonna have to re-read that a few more times to get more understanding of it

[kryptonitewhite 1]

In reality, we just need to get the heat off the coil, so moving it anywhere else will be useful. So instead, you have a lot of steel in the motor, add some copper or aluminum shorting rings, and design the motor such that air is drawn down into the top plate, over the windings, and then passing the heat into the shorting rings below the gap or into the steel above the gap.

Do you know of any cutaway pics that would give a good view of this? I recall years back studying the Adire Audio Extremis and it's sleeves, but that was a long time ago.

Thanks again, this is exactly what I was looking for.