D-Fend Settings??

[yigba]

Thinking of pulling the trigger on one of these for a pair of 24" T39's with 3012LFs.

Here's a link to the manual: http://www.parts-express.com/pedocs/man ... manual.pdf

Looking at the manual's definition of F3 (the frequency where the low end response crosses a line 3 db below the mid-band sensitivity) and Fb (the frequency at which the tuned ports minimize the cone excursion) has me trying to figure out those numbers for my T39's.

My best guess is that F3 is around 50 Hz and Fb is around 48 Hz?? Anyone have any other ideas on this? I could always just set it to limit 55volts at around 60 Hz setting but I wanted to try and be more precise than that.

And yes, I know it's $200 and I can just use something else cheaper but I want something completely idiot proof that is set and forget. The limiter on my DSP doesn't have attack settings fast enough to truly act as a brickwall limiter.

[miked]

You just might be the first person here using this gadget. I know it's been talked about here before, but I don't think anyone's used it.

Sorry I can't help, but it's a free bump for you.

[Bruce Weldy]

At 200 bucks per cabinet, it's cheaper to just get a good limiter.

Everybody was excited when these were announced, but at that price point - forget it.

[yigba]

You can use one D-Fend for two cabs in parallel. Look at the manual.

You can actually use it for up to 4 cabs provided the power and ohms are within the stated limits.

[Bruce Weldy]

You can use one D-Fend for two cabs in parallel. Look at the manual.

You can actually use it for up to 4 cabs provided the power and ohms are within the stated limits.

Yeah, but then you have to build a box for it and put it inline, or you install it in one cab, then the cabs have to always be connected in a certain order or it doesn't work.

Too much expense, effort, and work to when you can accomplish the same thing much cheaper and your system can be moved/changed on the fly.

It's a great product - it's too damned expensive. At $50 a unit (which is probably what they get for OEM suppliers) it would make perfect sense.

[yigba]

I'm not building a box - probably just velcro it to the cab so I can remove and not have to put screws in the cab. Or just place it away from the cab.

I don't know - no rack or power required, no knobs to turn just set it and forget it. Even a dope like me can't screw it up - which is a major plus.

Plus I have a credit on Amazon that's just burning a hole in my pocket....

Back on topic - anyone have comments on my estimates of F3 and Fb?

[Bill Fitzmaurice]

Plus I have a credit on Amazon that's just burning a hole in my pocket....

They sell limiters and loudspeaker management systems too. I agree that the price of the DFend takes it out of consideration. If you do get one follow the plans instructions for high pass frequency and voltage limits.

[yigba]

Leland made the cabs for me and as a result I don't have the plans. I know they should be limited to 55 volts. And I high pass them at 48 Hz.

Hence my estimates above.

You had the original prototype didn't you Bill? And you created the speaker cabs. What would you use for Fb and F3?

[Gregory East]

Afaik T39 has no Fb, at least not in any useful sense. Only the THT suppresses its own excursion as frequency drops lower. The rest only proceed to shred themselves as frequency drops and power maintained.

Iirc, 3012lf takes 60v @ 45hz if you feel like going for gold. 55v is safer.

[yigba]

Thanks Gregory. I ordered the unit so I'll give my feedback on it when I set it up.

[djtrumptight]

3012LF is limited to 50 volts in a T-39's,high passed at 45 hz.

[Bruce Weldy]

3012LF is limited to 50 volts in a T-39's,high passed at 45 hz.

You're both right. The old plans said 60, the new say 50. I run at 54.

[yigba]

In case anyone's curious the unit arrived today and I have programmed it per the Wizard. The choices in HPF for subs are 35Hz, 50Hz, 60 Hz and 85 Hz. The Wizard assigned a 50 Hz hpf.

It was very easy to program and the wizard gave me smaller limit parameters than I'd like. I manually programmed the peak to limit at 55 volts for my T39's with 3012LF's and there is also a full frequency band RMS limit threshhold that I have programmed at 38 volts.

Gonna hit it with the sine wave test tonight to see if these settings are good to go.

I know it costs $200 but there are no buttons to accidentally touch, no rack space to take up, can limit significant power if needed to, no power needed, it has both RMS and peak limiting, it's small and it's a breeze to program. I like it so far but the proof will be in the pudding when I test it with the sine wave.