BillFitzmaurice.info

Looks great! I can see that the second cab is coming together much more quickly. It's going to be insane with 8 of those!

Time is just not available the last few days, sadly.
The weekend is all i can hope for right now, should get the time to finish the B and paint A+B then. I think i will spray them, anything to consider when spraying them vs rolling them? The duratex-equivalent.

The thought around the wheelboard-thing evolved a bit further:

Instead of combining the wheelboard and the stacking for the tops, i thought it could be more efficient to combine the wheelboard and the V-plates into one element, and do the stacking frame for the tops in it's own to have that wheelable as well.
I thought of combining 4 of the T30s to one Dolly, and connect the two V-plates to one wheelboard underneath. This would be covering the area of two T30 next to each other, with the frames on whe V-Plate could build an interlocking machanism so the slip together and stay there as one board, and i avoid having anything not needed.
When stacked, the V-plates would each have two wheels sticking on top of it on each side in the front; not sure about the rattling that brings but i think i could cover them if needed.
The other idea of reusing the wheelboard for stacking the DRs does just not work out for a stacking of the DRs i would trust; want more of a sidepanel holding them tight reaching to both tops.
And when seperating that, i could have the DR-Dolly already stacked and angled for Transport, in pairs, so i just lift them on top of the T30s (or besides when putting all T30 in one block) and strap them down and i am done.

Will think about that further, the Dolly of 4 T30 would be sort of heavy to carry around with around 50kg each...+200 summed up then...the wheels can do that, but lifting/tilting around steps or something similar would be painful.
Buut, it would be super compact and the V-plates are already attached with it, so it is a complete stack on wheels sort of.

Design it so that you can stack 4 if the going is easy, but only stack two if there are steps and make two trips.

Also, the furniture dolly style carts will be easier to pull than push over soft terrain, like grass. Perhaps put a little thought into a pull strap or something similar. You're obviously clever enough to figure it all out. I am really excited to see what the final solution ends up being.

Bruce Weldy wrote: ↑Thu Apr 09, 2026 8:09 am Design it so that you can stack 4 if the going is easy, but only stack two if there are steps and make two trips.

This coul make obstacles more rollable, good idea thank you. Will keep that in min when thinking about how to strap all down, to be able to unstrap just the top pair. Thx.

Seth wrote: ↑Thu Apr 09, 2026 8:48 pm furniture dolly style carts will be easier to pull than push over soft terrain, like grass.

I don't think i will get that all-terrain-capability, grass is carry floor not rolling. But pulling could be handy in a lot of situations, will keep an eye on that as well thank you. Wheels will be the bluewheels like on flightcases, not that furniture casters.

Will update when the first idea gets visible, at first i need to build and paint that boxes now :)

Aand cab b finally completed :) front to be cut when the glue set, then sanding and rounding the edges Took a few trys, but i figured the multicutter with a wide blade is super fine to get my connector cutouts; as some do the same for wheels, the multicutter with oscillating blade is your friend on that point: The precutting worked, fits like a glove to my template without touching/pulling anything :) (except the bottom panel, mouth braces are not yet in) when the glue has set, i think i can finish a and b tomorrow and when the weather fits i'll spray them and see how that works out :)


Edit: On the Limiting side, i came to a question where i am not sure about, even after re-reading the limiting-section here from leland...

So, the Driver used is the LaVoce SSF122.50L. 400W/800W 8 Ohm, wired in series in pairs in each cab, and then all cabs parralell.
So the boundary is set by what one cab can take.

In the plans the VPL is referred to the Xmax from T/S-parameters, which the driver used has 11.5mm.
Interpolating the chart in the plans, this comes to a VPL of 53,75V per Driver, in series then doubled to 107.5V.

Taking the other route about wattage like in the leland thread here, the 400W and 8 Ohm multiplied and taken the squareroot from there takes the single Driver to 56V and double to 112V for series wired pair.
When doing the double drivers directly, 800W to 16 Ohm, i end at 113,x V.

BUT the driver is designed for 400W continuus (AES), and 800W Program.
Going from there would be (800*8)^(1/2), 80V as peak limit and 160 for the series wired pair. Which would be around the upper limit the amp can produce (somewhat close to)

So i am supposed to limit it to the 400w rating, which is somewhat close to the xmax-derivation, somewhere between 107 and 113V?

This is the Chart of Options from the amp in use: So i should land at the second row, limiting to 170V to have the current limited to the 118 V, which would be the closest option?
Or the 140V (below the 800W program handling result of 160V)?
The amp has a mice piano to config that, as here but with only two channels instead of four:
Pushing 170V peak into a 4 Ohm load (4 cabs on one channel) would resuklt in 7225 watt, which divided by the 8 drivers affected would give every driver a peak of 903 watt.
Pushing 140V into a 4 ohm load (same config) would give every driver 612 watt, which is just between aes and program.

I tend to drive 2 cabs per channel only, which would result in the same numbers as the resistance is doubled.

I just want to avoid blowing everything up, and i am not sure if i get this right. Well i am sure i do not get this right :D.
Anyone who could push me into the right direction?

In general not as sure as i thought about VPL. Do i want to avoid the clipping from the amp here, or do i want to avoid to exceed the limits of the driver configuration connected?
As i limit the amp output by this...i am not sure anymore.


Edit2:
Rounded and filled, sanding needed :)

Still problematic on the timing side, and in addition the weather keeps pouring rain on me...
But finished except paint...slowly i realize the dimensions of what i started here :D
But i like :)

Cables would run fine when stacked in this way All the panels sorted and cleaned up a bit as well The next picture will be all black :)

I would use the AES number, and drop the voltage by 5v. There would not be much difference in output by using a bit less, but you would save the drivers from over extention. You gain more SPL by adding cabs than you would by cranking up the last bit of amp power.

Tom Smit wrote: ↑Tue Apr 14, 2026 9:43 pm I would use the AES number, and drop the voltage by 5v. There would not be much difference in output by using a bit less, but you would save the drivers from over extention. You gain more SPL by adding cabs than you would by cranking up the last bit of amp power.

I will start there and try around what results from this if 8 cabs start playing along. Thank you for that input :)

Marflinger wrote: ↑Sat Apr 11, 2026 11:52 am So i am supposed to limit it to the 400w rating, which is somewhat close to the xmax-derivation, somewhere between 107 and 113V?

Using a dbx DriveRack or equivalent outboard DSP with a true Brick Wall limiter, set the limit per the plans, based on driver Xmax, not the driver's power ratings. Since most DSP's limiters are adjusted in incriments of 0.1 or 0.5dB, you may not be able to dial inexactly 107.5V. Use the closest voltage to that figure you're able to manage, that's not more than that figure.

I would personally not set the mouse piano (excellent terminology, BTW. Got a chuckle out of that) and just rely on the DSP for voltage limiting. If you don't have DSP yet, I'd set it for 100V.

I just want to avoid blowing everything up...

The voltage limits and high pass filter settings in the plans are there to keep you from damaging the driver from over excursion and are considered strictly mandatory for horn subs. The driver power ratings are thermal limits, to keep you from melting the voice coils. Always limit to whichever is less and you'll be in safe territory. In this case and pretty much any other case I can recall, the limits in the plans are the figure you want to use.

I'd set the gain DIP switches to 41dB.

Seth wrote: ↑Tue Apr 14, 2026 10:51 pm based on driver Xmax, not the driver's power ratings.

Alright, i will go from there. This somewhat equals the AES-Rating pretty close, so you both direct me to the same values.

I will do both, the amp limiting and the limit in the DSP. But to rely on i trust the amp the most, it limits the output no matter what i configure in the signal chain before. And as the mice piano is not just a knob in the front, it is highly unlikely to get changed ever.

Seth wrote: ↑Tue Apr 14, 2026 10:51 pm are there to keep you from damaging the driver from over excursion

Alrightr, so driver protection it is. Thank you for clarifying that, i just started to be unsure about this.

Seth wrote: ↑Tue Apr 14, 2026 10:51 pm I'd set the gain DIP switches to 41dB.

This is just the input gain, i will match that to the other amp for the top to get all amps to a close level of load when running everything to the desired level.

Marflinger wrote: ↑Wed Apr 15, 2026 1:25 am ...But to rely on i trust the amp the most, it limits the output no matter what i configure in the signal chain before...

On principle, I agree.
But, sinse this specific amp doesn't appear to have an appropriate brick wall limimiter (very few do), it's useless for what you need the limiter to actually do. If you want to use both, the 170v limiter setting on the amp is the one you want. But, it won't save your drivers.

I haven't read the manual for your specific amp, but my understanding from dealing with similar amps before is, what you're calling the input gain is in and of itself a limiter of sorts and translates directly to the maximum output voltage gain the amp is capable of producing. I don't have my spreadsheet to reference specifics at this moment, but if I recall correctly unity gain on pro audio signal output (XLR) is something like 1.45 or 1.55 volts. The 38dB gain setting wouldn't be enough voltage gain and the 44dB setting was way too much.

I'll pull up the manual for your amp a little later and confirm. But, I'm pretty sure what I just wrote is accurate.

In my understandimg, voltage limiting should be as brick as it gets?

The current delivered to the output is just cut at a given value, in this case at 140v peak? So no higher current will be brought to my precious drivers...?

The driverack (dbx) limiter limits the signal that goes to the input, i would measure the current the amp produces when fully open and set the limiter to the point where full amp delivers the desired current outwards...or?
No bridging, so voltage swing not that of a point.

The input gain works sort of like a preamp if i get this right, like the dbx limiter limits the output signal i can increase/decrease that on the input side of the amp. I'd use that to have the load of the amp (power drawn) somewhat balanced to the combination of all amps running, so the amp can run below 100% load.

Will take a look at the manual again as well.

Edit:
This shows the correlation from the input gain:

Marflinger wrote: ↑Wed Apr 15, 2026 10:12 pm In my understandimg, voltage limiting should be as brick as it gets?

Not all limiters act the same, but they all limit voltage... just at different times, rates, durations and under different conditions.
The brick wall limiter you need, does it nearly instantly and wont allow it to exceed the set value for any amount of time.

The current delivered to the output is just cut at a given value, in this case at 140v peak? So no higher current will be brought to my precious drivers...?

I'm sure it's what you meant, but I'm going to clarify this for the casual reader... Voltage and Current are related, but are two different things. Limiters attenuate the signal at the set value so the voltage does not increase beyond that value. Current isn't controlled in any way other than as a side effect of the voltage being limited.

The reason the limiter in the amp is useless is, you need to limit to 107v... not 140v. You WILL damage your drivers if you allow them to see 140v. I know the driver manufacturers have a RMS/Peak thermal rating, meaning you can put a constant tone through the driver at the RMS value for extended periods of time OR pulse a tone in short bursts with equal duration of no tone (50% duty cycle) at the "peak" value. But again, this is a thermal limitation. Exceed it and the wire that makes up the voice coil will melt. That's all that means.

You can blow a speaker from non thermal related reasons at less than the rated power, usually related to damage caused by exceeding Xmax at low frequencies. But, that's only a half truth.

Exceeding Xmax doesn't mean instant doom to your drivers. Matter of fact, you can exceed Xmax, within reason, for the entire natural life of a driver. Xmax has more to do with keeping the voice coil within the effective flux of the speaker magnet. When the coil is within Xmax the input signal has high authority over cone movement. When pushed slightly beyond Xmax, a little bit of the coil leaves the strength of the magnet and the signal has reduced control over cone movement, the cone doesn't do exactly what it's supposed to do, but usually close enough to not hear anything too offensive to the ears. Pushed further, you'd typically (I'll come back to this in a moment) start to hear audible distortion in the system. As a matter of fact, drivers designed to be used in guitar cabs intentionally have a very small Xmax and they're intended to be run beyond Xmax for the tonal quality (distortion) it provides. So, exceeding Xmax doesn't automattically turn your drivers into a smoke machine or door stop.

However, Xlim is the mechanical limit of cone travel. The cone surround, spider, voice coil, and backing plate have a maximum allowed amount of travel before physical damage occurs. Push too far into Xmax and you'll find Xlim. The voice coil will smack into the backing plate, the spider can separate from the cone, and the surround can tear and/or separate. The cone itself can even tear and break up into pieces.

That part I said I'd come back to, about pushing beyond Xmax... with a direct radiator it's much more evident. You can hear how bad it starts to sound. With horn loaded subs, you won't hear it as distinctly. You might not hear it at all. There's little to no audible que that you're about to hurt something. Push the volume up, sounds awesome! Push it again, still awesome. Push it again... drivers start blowing, bass reduces. Pure instinct and stupidity will kill the rest of them... when you push the volume one more time. LOL

I'd have to reference some notes and do a little research to refresh my memory, which I'm not going to do... but, I want to say there was usually about 3dB of output (maybe it was 6?) between Xmax and Xlim. It's really dependent on the specific driver design. But, there's more to it. Within Xmax, input voltage, excursion, and measured volume are very linear, a dB on the volume slider measures a dB of measured SPL. The further beyond Xmax you push it, the less and less the cone excursion moves per volt of increase. So, to get that 3dB of not perfect sound, it might take +6dB of voltage... which is where you'll find the thermal limits of the voice coil.

All this to say... ummm, what was my point? Oh yeah! The limit in the plans is the safe limit. Pay zero attention to advertised RMS/Peak values. Your system will have one limit based on keeping the driver within the excursion it's designed to have, which results in linear response, impeccable accuracy, outstanding output, and reliability you can count on for years and years to come. 107 Volts.

140V will damage your drivers.

The driverack (dbx) limiter limits the signal that goes to the input, i would measure the current the amp produces when fully open and set the limiter to the point where full amp delivers the desired current outwards...or?

You essentially got it right. You'll measure voltage output (not current) with the speakers disconnected and reduce the limiter threshold until the voltage is either at or slightly below 107V. There's a little more to it. We can go over the whole process when you're ready.

Marflinger wrote: ↑Wed Apr 15, 2026 10:12 pm Edit:
This shows the correlation from the input gain:

My numbers were off earlier, Unity gain in pro audio equipment is 1.228 volts, not 1.45 or 1.55.

So, you'll want to set it to 41dB

Admittedly, that's not how I thought that worked. Makes sense now though.