BillFitzmaurice.info

Hey there all.

I was wondering why using the calculator provided here:
https://leaprofessional.com/blog/limiter-calculator/

which from what I can tell simply uses the Vpeak = sqrt(PContinuous * R)
Using the provided specs from 18sound found here:https://www.eighteensound.it/en/product ... /12NLW9300
I used the following values:

Power Rating : 1200
Min Resistance: 5.7
High Pass Freq: 40 Hz
Speaker Type: Subwoofer
This yielded a result of:
RMS : 82.7 v
peak: 117v

This is substancially different from the Titan48 plans which state that the limit is 70v and for safety should be set around 10v below that.

Is there a reason for such a difference? or is the 70v mentioned on the plans already taking those extra 10v of safety in consideration.

I understand we don't get that much advantage from a couple of extra volts, but this seems like way more than 3db difference.

That calculation doesn't consider the mechanical limits of the driver, so it's worthless.

works for me! ty Bill

To add a little clarification... every driver responds differently in different cabs. That driver in one cabinet may be able to take it's full rated power/voltage and never exceed it's Xmax. Put it in another cab and it may bottom out the coil on half rated power/voltage. So, the voltage limit is dictated by the cab/driver combination and the voltage is ideally limited to a figure that keeps the cone and attached motor structure movement within it's designed operation range throughout it's intended frequency range. The only way I'm aware of designating an accurate voltage limit is using cab modeling software.

And, to put it into proportion:
A few extra volts at the top end of output is probably wasted in power compression anyway.
Whereas adding another cab with a driver capable of 70V is going to add, at a minimum, +3dB...

This explains a lot. Thanks guys.
I guess I'll take this thread to ask a different question related to this driver then:

We run 4 boxes each pair in parallel, so I assume this would turn each pair into 4ohm 800w. But I see the driver specs state a minimum load of 5.7ohm. So I guess my question is, is it because of the speaker / cab combination and the fact that we run them on different "limit" values that allows us to use this in 4ohm. Or am I completely off? Also, what would then be the safest load I could run with this driver? Could I run 3 parallel cabinets ?

jmanso wrote: ↑Fri Jun 02, 2023 5:37 am the driver specs state a minimum load of 5.7ohm.

That's free air, not loaded in an enclosure. You're very safe to consider them 8 ohm loads.

jmanso wrote: ↑Fri Jun 02, 2023 5:37 am We run 4 boxes each pair in parallel, so I assume this would turn each pair into 4ohm 800w. But I see the driver specs state a minimum load of 5.7ohm. So I guess my question is, is it because of the speaker / cab combination and the fact that we run them on different "limit" values that allows us to use this in 4ohm. Or am I completely off? Also, what would then be the safest load I could run with this driver? Could I run 3 parallel cabinets ?

You're almost completely off lol.

One step at a time:
On the same page that tells you the minimum impedance is 5.7ohms, is an impedance chart.
Impedance is frequency dependant. You can see from the chart it's lowest between 200 and 300Hz, and highest at Fs, 120 Ohms at 47Hz.
As Bill said, the nominal impedance load is 8 ohms per driver.

Setting limits is possible to do for "normal" direct radiator subs, but essential for horn subs. 800W is the manufacturers measurement in an infinite baffle. Put that same driver in a horn sub and the result will change.
So stop using watts, use volts.
In order to set your limiter, you use a voltmeter to read volts. You don't set a different limit based on impedance as such, you just set a voltage limit.

If you take those 2 things as given, let's move onto the rest.
2 x 8 ohm drivers in parallel per channel, as you say, is 4 ohms. Each driver is still 8 ohms, but 4 ohms is what your amplifier "sees" as a load.

So what is 3 x 8 ohm drivers per channel? That's 2.66 ohms your amp "sees".
Since you haven't stated it, if, according to it's specs, your amp can safely operate 2 ohm loads, it can do 3 x 8ohm drivers per channel technically.
But I wouldn't do that. I would get another amp and feed the sub signal to that for more cabs.

this is awesome Grant, thank you so much. I'm a slow learner but I'll get there

Let me try again then:
The specs provided by the manufacturer once used in a cab simulation software, using some math that's likely way beyond me, will produce the actual load of the driver on the given design.

in the case of the 12NLW9300 on the titan48 it'll be somewhere near 70v. I'll go on a limb saying the width of the titan isn't important as the driver enclosure part remains the same.

By connecting 2 in parallel, they'll still be 70v 8ohm each, but the total load the amplifier needs to provide will be at 4ohms, because we have 2 drivers. I guess this also explains why 70v is the same limit regardless of impedance.

We are running our subs on a powersoft T604A, which is rated at 4x 1500W @ 2 Ω | 4 x 1500W @ 4 Ω | 4 x 1250W @ 8 Ω ( 145 Vpeak | 50 Apeak @ 8 Ω)

In theory we can confortably run 8 subs there, 2 per channel.
But I was wondering if I could move to Armonia DSP completely and have that amp power the full stack. 2 channels for subs | 2 for tops

This works fine for 4 subs | 4 tops (2Subs|2Subs|2TopsL|2TopsR) but because it's stable at 2ohms could I consider adding 2 more subs to this.

This is a bit hypothetical at the time as we'll likely not build more subs this year, but always good to learn