Eminence D-Fend experience?

[OzzyGreg]

.
Guys,

Has anyone tried the Eminence D-Fend system?

It sounds like a good way to protect your speakers from over-excursion.

I haven't read deeply into it yet, just seeking opinions on it.

Obviously, if one is careful with gain/volume settings there is no need for it. I already realise that, not looking for that type of advice!

Cheers,
Greg

[billfitzmaurice]

They're not available yet; October at the earliest.

[will33]

I keep seeing that but never read into it, just figured it to be another gizmo I don't need. So what is it, an adjustable low slung hpf or something?

[One Drop]

It's the D-Pends system, protects you from the brown note.

[PhiDeck]

The description of the Eminence D-fend loudspeaker protection includes the fact that it contains active circuits (eg. microprocessor and MOSFET(s)).

The photograph seems to show only four terminals and there is no evidence of a battery, which begs the question: how are the active circuit elements being powered?

If there really is no battery, then one might infer that power is being rectified from the audio input from the amplifier. ie. that a fraction of the power intended for the speakers is being diverted to power the D-fend. In which case one hopes that the microprocessor's start-up time - including its required reset assertion after its input power is in-spec - is very short.

Does anyone not under NDA have any insight into this topic?

[lokikallas]

Originally Posted by One Drop

It's the D-Pends system, protects you from the brown note.

+1

[lelandcrooks]

D-fend
Watch the videos. They're pretty dry, (except for the one with fire), but explain it all pretty well.

[rpsands]

From what I understand it's a speaker level DSP device focused on preventing over-excursion (or overheating?) (but in theory with other options available in the future). Hope that's a good way to sum it up accurately.

* one would expect it to be powered by the current running through it, but again, haven't watched the videos just read the ad copy.

[greenboy]

It's also an OEM thing, because how many end users are going to be able to calibrate it properly for their enclosures.

[rpsands]

Originally Posted by greenboy

It's also an OEM thing, because how many end users are going to be able to calibrate it properly for their enclosures.

Not many, But you could prepackage one in a fEarful if it's got enough power handling, which might be neat.

I wonder how far we are from speaker level crossover + dsp eq correction in MI cabinets, if this thing pans out.

[greenboy]

I expect it's a little above most bass cab manufacturers' acumen or willingness to actually use it well. And then there's the cost issue (though I think the item itself is pretty cheap). Could do well in mid-tier PA perhaps because there's already a lot of blackboxing going on.

Eminence could also use it as a nice chess piece in their OEM strategies, supplying not only the unit but the specific calibrations for OEMs.

[Mr. Foxen]

Anything like DDT on Peavey amps?

[lelandcrooks]

Originally Posted by Mr. Foxen

Anything like DDT on Peavey amps?

Maybe in function only.

It does not dissipate the power. No heat is produced at the unit. It varies the impedance for the part of the signal that is over the setting for the unit. Not quite sure how they do it, I assume some kind of voltage divider circuit. But if you watch the videos, he'll run an oscope showing voltage to the driver and voltage out of the amp. It just stops feeding the driver at whatever your prescribed input to the driver is. They drop 6k from a lab gruppen amp into a 4" driver with no ill effects.

In my conversations with them, Eminence also tells me it's very musical. You don't hear the unit engage, or really know it's doing anything.

[greenboy]

Originally Posted by Mr. Foxen

Anything like DDT on Peavey amps?

I would assume not. DDT as my dim long-term memory recalls is a limiter system that when engaged allows maybe 3 or 4 dB of average output level more without clipping; ie a form of peak limiting. But it's tied to amp characteristics rather and has no idea what the xmax of whatever drivers connected are. I've noticed it sounds pretty good in some Peavey products and maybe not so good in others, so implementation across their product line over the decades may differ.

D-Fend on the other hand is about massaging the output of an amp so that enclosures it's used in have their drivers protected from over-excursion. Once adjusted to the enclosure/drivers, it's keeping voltage within bounds and probably able to do that with several methods (frequency dependent). A little different than the first case.

[Mr. Foxen]

Originally Posted by lelandcrooks

It varies the impedance for the part of the signal that is over the setting for the unit. Not quite sure how they do it, I assume some kind of voltage divider circuit.

Not for valve amps then. I guess being low power they don't tend to run into excursion issues.

[craig.p]

My reading of this system is that it's a reasonable fail-safe mechanism to have in place where Best Practices are not being (or might not be) followed. Rental companies come to mind as just one example -- I mean companies that don't send a competent engineer along with the boxes. My guess is that these things are designed to bolt to the back of every magnet. Probably expensive on a per-unit basis, but hopefully will pay for itself with the first driver that doesn't blow past xmax. Could cut way back on warranty returns, replacement time in the field, reconing, shipping costs, thus netting out positive in the long run. At the risk of repeating what GB's already said, the bit of implied fine print for the max-excursion application is that it seems to be aimed at addressing not driver limitations but rather the limitations of a specific driver mounted in a specific box that unloads at a specific frequency. This is because the relationship between excursion and applied voltage is box-specific. (So, the primary target audience would be the cab builders, not the driver builders, the driver builders serving only as the delivery mechanism for the device. For example, the Avatar folks could buy Eminence drivers with the device already bolted on the back of each one, each already pre-programmed to slew maybe 5-10 Hz above where that particular cab lets go of its drivers.)

Of course in an ideal world you high-pass your bottom end (either between preamp and power amp or in the effects loop), keep an eye and ear on your cones, and all the rest. But you say that, for example, to most bass players, and they give you the ten thousand mile stare. Considering that fact, I think the market for this will be significant.

I'd expect the cab builders will have pilot units installed and out in the field with their endorsers pretty soon, if they don't already.

[greenboy]

Exceeding xmax (or hitting xlim) doesn't only happen by unloading however. It also can and often does happen from signals that are strong in the useful passband.

[craig.p]

Yes sir, understood. The only point I was trying to make is that one couldn't have a driver-specific one-size-fits-all program loaded into the device for a particular driver part number, because depending on box design the device might slew too early or too late.

[Bassmec]

This will make sound equipment sound far better and last lots longer in the hands of complete idiots.
Err! So this is supposed to be a good thing?.

[greenboy]

Since there are so many complete idiots, it's not a bad thing ; }

But seriously, once you get into chaotic club SR environments with no guarantee of the same operator every night, it's got some market potential right there... The big boys in SR already have advanced Speaker Management Systems and whatnot, so they aren't necessarily a good target.