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[Rory Buszka]

Hello Ionescu,

I noticed you have an "extended" version of your enclosure that has extra walls around the drivers. Do you measure a difference in sensitivity or frequency response between the two cabinets? I would not think the extended walls have a meaningful impact, but there have been "PWH"-type subwoofers built that had a duct in front of the driver and I suppose it worked well enough for those designs. Having lugged a fair number of different cabinets I would prefer my subs to be smaller and lighter if at all possible, so I don't know if the extra size of the extended enclosure would make a proportional improvement. Don Keele did a study at one point for JBL comparing output vs cubic volume for different enclosure types using a common type of driver, and he found the bass-reflex enclosure to produce the most output per unit volume, so I don't think it is necessary to experiment with "extended" or "quasi-horn" designs. High-efficiency bass systems like folded horns are there to try to make the most dBs from the fewest drivers and amplifier channels, but the penalty is large enclosure volumes, which must be stored, transported, and moved (sometimes lifted).

Normally, the front edges of your cabinet only need to extend beyond the speaker frame enough to allow for the full mechanical excursion of your speaker (at least double the rated Xmax of the speaker) without contacting the grille and producing extraneous noise. Art Welter's dual-LAB12 subwoofers are an example of a good way to mount a speaker grille, and there are some companies that will custom-cut perforated metal grilles to the necessary shape for your enclosures.

Danley Sound Labs builds the CS30, which is a direct-radiating subwoofer using a single 12" LAB-style woofer in a vented enclosure. This enclosure design from your friend makes me think of a double-CS30. You're probably on a decent track for producing low bass without using large horn-loaded configurations.

As to the concerns about power handling and getting loud enough, anything can get loud if you pile up enough of them. SPL is more directly dependent on air movement than watts, and an enclosure that can thermally handle lots of power may not be able to mechanically turn that power into more sound. You'll run into one limiting factor first - either piston excursion limits or power handling limits, and the ideal design will reach both of these around the same output level. In the upper bass, power handling is usually the limiting factor, and in the lower bass, piston excursion is usually the limiting factor. This can be determined using an enclosure simulation program, even a simple one like WinISD.

[Jim McKeveny]

Don Keele did a study at one point for JBL comparing output vs cubic volume for different enclosure types using a common type of driver, and he found the bass-reflex enclosure to produce the most output per unit volume

The "tapped" horn may eclipse that depending on qualifiers - passband, distortion...

[Ionescu Florin Gabriel]

Hello Ionescu,




I noticed you have an "extended" version of your enclosure that has extra walls around the drivers. Do you measure a difference in sensitivity or frequency response between the two cabinets? I would not think the extended walls have a meaningful impact, but there have been "PWH"-type subwoofers built that had a duct in front of the driver and I suppose it worked well enough for those designs. Having lugged a fair number of different cabinets I would prefer my subs to be smaller and lighter if at all possible, so I don't know if the extra size of the extended enclosure would make a proportional improvement. Don Keele did a study at one point for JBL comparing output vs cubic volume for different enclosure types using a common type of driver, and he found the bass-reflex enclosure to produce the most output per unit volume, so I don't think it is necessary to experiment with "extended" or "quasi-horn" designs. High-efficiency bass systems like folded horns are there to try to make the most dBs from the fewest drivers and amplifier channels, but the penalty is large enclosure volumes, which must be stored, transported, and moved (sometimes lifted).

Normally, the front edges of your cabinet only need to extend beyond the speaker frame enough to allow for the full mechanical excursion of your speaker (at least double the rated Xmax of the speaker) without contacting the grille and producing extraneous noise. Art Welter's dual-LAB12 subwoofers are an example of a good way to mount a speaker grille, and there are some companies that will custom-cut perforated metal grilles to the necessary shape for your enclosures.

Danley Sound Labs builds the CS30, which is a direct-radiating subwoofer using a single 12" LAB-style woofer in a vented enclosure. This enclosure design from your friend makes me think of a double-CS30. You're probably on a decent track for producing low bass without using large horn-loaded configurations.

As to the concerns about power handling and getting loud enough, anything can get loud if you pile up enough of them. SPL is more directly dependent on air movement than watts, and an enclosure that can thermally handle lots of power may not be able to mechanically turn that power into more sound. You'll run into one limiting factor first - either piston excursion limits or power handling limits, and the ideal design will reach both of these around the same output level. In the upper bass, power handling is usually the limiting factor, and in the lower bass, piston excursion is usually the limiting factor. This can be determined using an enclosure simulation program, even a simple one like WinISD.

Hello

For the 4 basses I decided on 2 crown xti 4002 pieces

Before ordering I would like an opinion on its strength

2x1600-2ohms
2x1200-4ohms
2x650-8ohms

Power isn't too much into 2 ohms for a 2x800 how much can labs into 3 ohms?

Into 3 ohms -1066 w Is it OK to attack the subs with this power from the crown xti4002?

[Art Welter]

Hello

For the 4 basses I decided on 2 crown xti 4002 pieces

Before ordering I would like an opinion on its strength

2x1600-2ohms
2x1200-4ohms
2x650-8ohms

Power isn't too much into 2 ohms for a 2x800 how much can labs into 3 ohms?

Into 3 ohms -1066 w Is it OK to attack the subs with this power from the crown xti4002?

Ionescu,

The output of the Crown XTi 4002 into 3 ohms (the impedance minima) would be in between 1600 and 1200 watts, a good amount of peak power for the LAB 12s.

Long term average power should be limited to under 400 watts per driver.

Art

[Ionescu Florin Gabriel]

Ionescu,

The output of the Crown XTi 4002 into 3 ohms (the impedance minima) would be in between 1600 and 1200 watts, a good amount of peak power for the LAB 12s.

Long term average power should be limited to under 400 watts per driver.

Art

Thank you for the answer Mr. Art!

 If in the long term I need below 400w for each speaker, this would mean that I should not go with the volumes at the maximum on the xti4002 to go with them in the long term, or keep them at the maximum but not give the gain from the mixer at all, because events like weddings, will they have to go 8-10 hours continuously?

I usually go with the tools on green, on the mixer -3 dB, even at 0 dB I don't increase the signal, on the LD SYSTEMS amplifier with the maximum volumes I increase the signal up to -10 with light blinking, the gain on the mixer being on the hour 10, and there is already an earthquake on the basses, their stroke being only 5-8 mm depending on the frequencies on the parts.

I have learned that the xmax of the speakers should not be exceeded, once this is done the life of the speakers will tend to infinity.

The bass will anyway be cut at 30 hz or even 35 hz, that's what my friend who designed my enclosure told me, from 35 hz up to full power, below 35 hz low power.

 I'm going to make a complete setup of audio tools, starting with 4 more Lab speakers, 4 b&c speakers tbx 100 and 2 inch drivers all b&c, horns also b&c for the 2 inch drivers, for the 2x12 satellites that I want to I make for the 4 basses, 3 crown xti 4002 amplifiers, soundcraft gb4 16 ch mixer, lexicon mx400 processor, crossover dBx driverack, cables, light-sound scaffolding, lights, including custom-made enclosures.

 And finally, I can use the xti 4002 without problems or go for something else with less power than the maximum 1200 2 ohms as I have on ld systems, but I am tempted by the xti 4002 because it is far above the LD in all respects, already at the ld I have problems with the potentiometer on channel 2, a noise is heard when I turn the knob, it being closed when I turn the first gear, a noise is heard in the labs as if the wires from the labs connectors are not making contact as they should , I hope it's something minor, dust, etc, and not to replace the knob with a potentiometer as I'll have to change the other one as well, it's been bought for 8 months, and that's what led me to return to CROWN?

[Art Welter]

 If in the long term I need below 400w for each speaker, this would mean that I should not go with the volumes at the maximum on the xti4002 to go with them in the long term, or keep them at the maximum but not give the gain from the mixer at all, because events like weddings, will they have to go 8-10 hours continuously?

I have learned that the xmax of the speakers should not be exceeded, once this is done the life of the speakers will tend to infinity.

Ionescu,

Reaching or slightly exceeding the LAB12's Xmax of 13mm is no problem, it's Xlim (mechanical limit) is 22mm.
With a BW24HP at 30-35 Hz, excursion shouldn't be a problem, but long term average (RMS) power still can be.
"Long term" can be a matter of seconds or minutes, hours are not needed to cook voice coils.
As an example, the RMS power of dynamic music when reaching peaks of 1600 watts may be under 200 watts.
If the sub content is highly compressed, it may have as little as 3dB dynamic range, (same as a sine wave) and 200 watts RMS would be reached at 9dB below the peak power.

Gain or volume settings don't limit average power, limiters do that. The Crown XTi 4002 has peak limiters, but not RMS limiters.

Art

[Ionescu Florin Gabriel]

Ionescu,

Reaching or slightly exceeding the LAB12's Xmax of 13mm is no problem, it's Xlim (mechanical limit) is 22mm.
With a BW24HP at 30-35 Hz, excursion shouldn't be a problem, but long term average (RMS) power still can be.
"Long term" can be a matter of seconds or minutes, hours are not needed to cook voice coils.
As an example, the RMS power of dynamic music when reaching peaks of 1600 watts may be under 200 watts.
If the sub content is highly compressed, it may have as little as 3dB dynamic range, (same as a sine wave) and 200 watts RMS would be reached at 9dB below the peak power.

Gain or volume settings don't limit average power, limiters do that. The Crown XTi 4002 has peak limiters, but not RMS limiters.

Art

From what you tell me, now I don't know which amplifier to have, I also gave up on the xti 4002 and decided 100% on the PKN XE2500 because this series shows the impedance as well as the power in real time on the screen.

This way I can set a power of 700-750w from the menu.

 I was told by the guys at that shop that the power into 3 ohms won't drop much over 4 ohms, and I might have a little over 4 ohms in 3 ohms.

BUT I WANT A VERDICT FROM YOU IF I CAN SAFELY AMPLIFY THE BASS WITH THESE AMPLIFIERS.

https://www.poweraudio.ro/amplifier_PKN_XE2500

With respect, Florin.

[Art Welter]

I was told by the guys at that shop that the power into 3 ohms won't drop much over 4 ohms, and I might have a little over 4 ohms in 3 ohms.

BUT I WANT A VERDICT FROM YOU IF I CAN SAFELY AMPLIFY THE BASS WITH THESE AMPLIFIERS.

YOU CAN SAFELY AMPLIFY THE BASS WITH THE CROWN XTi 4002 AMPLIFIERS PEAK OUTPUT OF AROUND 1400 WATTS INTO A 3 OHM LOAD, BUT THE SPEAKERS WILL BURN UP IF YOU USE THE FULL RMS POWER.

[Ionescu Florin Gabriel]

YOU CAN SAFELY AMPLIFY THE BASS WITH THE CROWN XTi 4002 AMPLIFIERS PEAK OUTPUT OF AROUND 1400 WATTS INTO A 3 OHM LOAD, BUT THE SPEAKERS WILL BURN UP IF YOU USE THE FULL RMS POWER.

Thanks for the reply!

And what would be the maximum rms power with which I can attack each 250-300 w speaker?

 Well, in this case, LD SYSTEMS is also too powerful for the two basses, because you told me that on LD I have around 1000 w, although the people from LD declare those nominal powers at 1khz, but we don't know if they are rms.

 I want to use the LAB speakers as much as possible, UNTIL THEY ARE DISCONTINUED AND CANNOT BE REPLACED IN THE FUTURE, I have had these speakers for years, 2 since 2016 and 2 since 2020, and there will be another 4 coming soon , the first 4 speakers were amplified with crown XLS 1502, and I said to have something a little more powerful and I got LD DEEP 2400X.

 On the xti4002 I can go with the volumes to the maximum and give it a gain from the mixer to take the signal to -20 SO NO MORE, EVEN THOUGH I CAN SAFELY GO TO LAB URI UP TO -10 won't I do it?

 Even those from crown do not specify in the manual if the powers of the xti series are rms, but let's say that it would be so.

[Art Welter]

Thanks for the reply!

And what would be the maximum rms power with which I can attack each 250-300 w speaker?

 On the xti4002 I can go with the volumes to the maximum and give it a gain from the mixer to take the signal to -20 SO NO MORE, EVEN THOUGH I CAN SAFELY GO TO LAB URI UP TO -10 won't I do it?

Again, your mixers gain setting does not determine average power use.

Long term "RMS" limiting with attack and release time constants of longer than 500 ms (milliseconds) should be less than the LAB 12 AES power rating of 400 watts, as AES ratings are conducted in free air, while driver's voice coils heat more when loaded in the cabinet, as the impedance is lower.

Going with an impedance of 3 ohms for the dual LAB 12, 49 volts would be around 800 watts. Half that power (400 watts) would be 34.64 volts, probably a good level for long term limiting.

This document may be of more help than I can provide:
https://www.powersoft.com/wp-content/uploads/2019/01/powersoft_TN009_LimiterSetup_en_v1.0.pdf

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