AudioKinesis Cabs Part VI...

[steubig]

lol

 

[kittywithabanjo]

I was packing for my gig tonight considered bringing my TC112 along with my hathor but decided I didn't want another thing to carry in.
I am sure the hathor on its own will rock enough.

 

[Al Kraft]

Depends who wrote the book and what it's about.

At least Duke had you doing this with a book. When he taught me this lesson he made me use a cereal box!

 

[tombowlus]

Which cabs are you talking about? My 115's are -4 dB at 62 Hz "on paper", though I've been told they sound like they have more low end than that number implies.

If you're talking about one of my 115's, my modelling program says -10 dB @ 43 Hz with all ports open.

I have not measured my TC115AF (wide body), but it sounds absolutely huge. Literally a "do anything" kind of cab, for sure.

 

[kittywithabanjo]

Man this little cab roars it puts a smile on my face every time putting it up on my dewalt tote has been working great.

 

[DukeLeJeune]

I have not measured my TC115AF (wide body), but it sounds absolutely huge. Literally a "do anything" kind of cab, for sure.

Ah, I should have specified those numbers applied to my "current" 115 cabs... your TC115AF was from a previous generation that had a bigger bottom end. I traded that for other stuff (a particular upper-mid voicing and higher efficiency) in the woofer that I now use.

 

[tombowlus]

Ah, I should have specified those numbers applied to my "current" 115 cabs... your TC115AF was from a previous generation that had a bigger bottom end. I traded that for other stuff (a particular upper-mid voicing and higher efficiency) in the woofer that I now use.

Good to know!

 

[DukeLeJeune]

Good to know!

The new woofer's T-S parameters predict about 2 dB greater broadband efficiency, plus it has a nice big peak at 1.6 kHz (switch-off-able via the midrange "smoothy/growly" switch). But the old woofer is slightly more efficient down at 62 Hz.

 

[tombowlus]

The new woofer's T-S parameters predict about 2 dB greater broadband efficiency, plus it has a nice big peak at 1.6 kHz (switch-off-able via the midrange "smoothy/growly" switch). But the old woofer is slightly more efficient down at 62 Hz.

Are you using the new 15" in your Hathor designs, only, or are you also using it in a newer TC115 design?

 

[DukeLeJeune]

Are you using the new 15" in your Hathor designs, only, or are you also using it in a newer TC115 design?

I'm using the new 15" woofer in Hathor, Thunderchild, and Changeling cabs. The closest comparison would probably be to the Kappalite 3015 (non-LF) woofer.

My custom 4-ohm 15" woofer has about 1/2 dB higher efficiency and about 2 dB higher voltage sensitivity than the Kappalite 3015 (non-LF), but otherwise it's pretty similar until we get to the upper midrange region. The reason the voltage sensitivity difference isn't greater is because my woofer is a "high 4 ohms" woofer, with a voice coil DC resistance just a little under 4 ohms, while the "8-ohm" 3015 (non-LF) has a voice coil DC resistance of just a little over 5 ohms.

The "high 4 ohms" nature of my woofer makes it practical for me to add a "4/8 ohm" switch to my 115 Hathor and Thunderchild cabs. This switch adds just enough series resistance to transform those cabs into a "low 8 ohms" cab, which can be safely paralleled with an 8-ohm cab, for use with a 4-ohms-rated amp. The power handling of that bank of series resistors is well into the overkill range.

With the switch engaged and the cab in "8 ohms" mode, the voltage sensitivity is just about identical to that of the Kappalite 3015 (non-LF).

 

[Lowendtech]

Would a Changeling 15 be 4 ohm only or switchable?

 

[strost]

Would a Changeling 15 be 4 ohm only or switchable?

Not to answer for Duke, but I was told 4 ohm only (due to the power needed for the rear facing mids?).

 

[DukeLeJeune]

Would a Changeling 15 be 4 ohm only or switchable?

4 ohms only. Sorry I left that out - strost is right.

The Changeling 115's rear-firing mids are in parallel with the front-firing ones and the resulting impedance is too low for us to get away with simply adding series resistance to end up with a "low 8 ohms" cab. The series resistance changes some of the woofer's parameters (electrical Q is effectively increased), and I think we can get a way with a little bit of change, but imo a lot of change is too detrimental.

 

[svtb15]

Just a fantasy wish list.
I would like to see a Full Range cab with flush or recessed mounted drivers. That goes down fairly Deep, that's not boomy in the 160 hz area, that is smooth thru the upper Mids and still be able to PUNCH for finger style .. I don't do slap much anymore. It was big in the 80s . but not so much now.
A cab that takes SIMPLE Eq easily if possible so one doesn't need to have a Para EQ.. And to be at least as loud as a 410 or louder if possible ..
55# or under would be fine. I wouldn't care if it was 4Ω if it were able to equal or out perform a 410 in volume with 500 watts input.

Is that possible?

Would be great to have a One cab rig that's american made, Loud, Full Range,

 

[winegamd]

I think a Thunderchild is in order for you.

 

[Thumper]

svtb15, except for the flush or recessed mount,you're describing my 32 lb Thunderchild composite 115 V1

 

[svtb15]

Please Please Please make flush mount drivers one day. Pretty please! I'm sure there are others with equally as bad luck ....
I only know how my gear is handled at times.
If it's not in a road case when im on my real gig, and knowing my crap luck, I KNOW something would be sheared off, Somehow , someway something would be cut, snapped off, etc. It just happens. I have bad luck like that..

ANYWAY... I'm just wishlisting... I don't want to force any change onto already GREAT sounding , great built product line by a builder that gives truth when publishing specs. And that is very appreciated these days with so much gear hype out there.

Praises to you Duke

 

[TomB]

I think a Thunderchild is in order for you.

Yep - A 115, or maybe a 212?

 

[svtb15]

Is a speaker such as a 3015 nonLF used is a generic commercial cab able to be designed to LIMIT it own output due to some design implementation?
. .OR do speakers LIMIT only when the Coil begins to heat up too much. Just wondering..
Or is what i'm asking make no sense at all

 

[DukeLeJeune]

I would like to see a Full Range cab with flush or recessed mounted drivers...

I don't have plans to do a "conventional" bass cab with the drivers on a recessed flat baffle behind a big full-face metal grille. Nor do I want to do a new design with four layers of plywood for the front baffle in order to flush-mount the woofer & round grille (yes, it took four layers of plywood to flush-mount those side-firing woofers on the Birdhaus 415).

That being said, I must admit that your request is perfectly reasonable.

So, what do you think of this: Perhaps I could add a wooden"lip" around the perimeter of the front baffle of an existing design, deep and thick enough so that the round woofer grille is effectively recessed a little bit?

Is a speaker such as a 3015 nonLF used is a generic commercial cab able to be designed to LIMIT it own output due to some design implementation?

. .OR do speakers LIMIT only when the Coil begins to heat up too much. Just wondering...
Or is what i'm asking make no sense at all

Well this is probably a longer answer than you wanted...

There are, in effect, two different mechanisms that limit what a woofer can do, namely "mechanical limitations" and "thermal limitations".

Mechanical limitations are related to how far the cone moves. If the voice coil moves far enough that it starts to go outside the magnetic gap, distortion starts to rise rapidly. At the same time, the suspension system (surround and spider) become less and less linear with these long excursions. At some point, either the voice coil moves so far beyond the magnetic gap that it causes audible distortion, OR the suspension system is stretched to the point that it causes audible distortion. The point at which the cone's excursion exceeds this threshold, whether due to voice coil or suspension system limitations, is called "x-max". Ideally it is measured, but often it is simply calculated, and sometimes a rather optimistic formula is used for the calculation.

As a real-world example of this, the Kappalite 3015LF's x-max is 9.6 mm, which is the point where the voice coil's excursion beyond the magnetic gap causes excessive distortion. The Kappalite 3012LF has exactly the same voice coil length and exactly the same magnetic gap height as its 15" sibling, but its x-max is only 9.1 mm! The reason is, the limiting factor for the 3012LF is the suspension system - the surround goes non-linear before the voice coil does. The actual distortion measurements reveal this (or so said the engineer who designed those woofers and did the measurements).

If we push the woofer all the way to "x-damage", well that's not good. We've either slapped the voice coil against the backplate or stretched the suspension system to its maximum. The woofer may have survived, but we have probably shortened its life expectancy significantly. The old adage "That which doesn't kill you makes you stronger" does not apply to woofers!

Okay, now let's look at the thermal side of things. First a bit of background: Woofer motors are extremely inefficient devices - out of every hundred watts that goes into a woofer, maybe 2 watts are converted into sound if we are lucky, and the other 98 watts are converted into heat. So a 500-watt peak is like hitting the voice coil with a 490 watt soldering iron! It gets hot, and it gets hot fast. And before it has a chance to cool down, along comes a bunch more wattage which gets converted into heat. The voice coil's heat is spread to the motor (magnet and other metal parts) and the air. If the voice coil gets too hot, the glue that holds it together softens a bit, and the physical stresses it's under cause it to go slightly out-of-round. So you might make it through the gig, but then the next day you notice that the voice coil sounds scratchy when you play the speaker or push gently on the cone. Or even if you never quite push the woofer to the point where you melt the glue, you are still putting a lot of "miles" on it when you push it very hard for a long time.

But long before the voice coil overheats, "thermal compression" is happening. As the voice coil heats up, its resistance increases. So it takes more wattage input to get it to play at a given level, which in turn causes it to heat up more, which in turn... yeah, it's a vicious cycle. At the same time the same thing is happening to the magnet - as it gets hotter, it loses strength (temporarily), which means that the woofer loses efficiency, so you need to put more wattage into it to reach the same SPL, which in turn heats everything up even more... I've simplified things a bit but basically that is what happens. So you keep feeling the need to turn up more and more, and it SEEMS like your amp is crapping out. By the end of the set the amp is turned way up and everything sound mushy and lacks clarity and impact, and you tell yourself that you need a more powerful amp. But then after the break (which gave the motor a chance to cool off so the magnetic strength returned), you come back and by golly it sounds fine again! The solution would be to bring more cab(s), and not necessarily more amp, to the next such gig. (The other solution would be to have everybody turn down and keep it turned down, but that's probably not going to happen.)

To recap, the woofer can get into trouble from too much excursion or too much wattage. The ONLY built-in safety mechanism I can think of is, the woofer warns you that it's unhappy by starting to sound bad. Fartout is a sign that you're exceeding x-max, and thermal compression (mushiness/loss of clarity/loss of impact) is a sign that you're starting to cook your woofer. Now for the bad news... these Kappalite-class "uberwoofers" usually have such long x-max that they probably won't fartout before the voice coil melts! So you gotta pay closer attention with your ears, and be willing to turn down as soon as you start to hear obvious thermal compression.

So now let's look at your question: "Is a speaker such as a 3015 nonLF used is a generic commercial cab able to be designed to LIMIT it own output due to some design implementation?"

If I was given the job of "design a cab for the 3015 nonLF that will protect it by limiting its output", here are the things I'd think about: A sealed box will make it very difficult to drive the woofer to x-damage, but a ported box allows better heat-exchange with the outside world due to air circulation. I think heat is more likely than overexcursion to kill this woofer as long as the cab is well designed, so I'd opt for a ported box. Maybe even put one port higher than the magnet and one port lower than the magnet in order to get a bit of "chimney effect" cooling... but none of this REALLY protects the woofer.

Since protecting the woofer is the top priority in this hypothetical, and assuming we're limited to cab design (and I can't cheat and put a $200 Eminence D-Fend unit in the cab programmed to electronically protect the woofer), I'd use deliberately inadequate ports. I'd use ports that are going to chuff and thereby tell you to "turn down" hopefully before the woofer starts to take damage, but hopefully not so early in the game that the cab becomes unusable.

Well that turned out to be a much longer and more complicated post than I'd planned on.