Change woofer in very compact 18” sub |
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2543 |
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Posted: 16 July 2019 at 12:28am |
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5175 |
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The percentage you do not subscribe to is higher than you might imagine. It usually boils down to not having enough woofers/amplifiers to get the job done in which, SPL is all that matters. Best Regards,
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Elliot Thompson
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2543 |
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I see you point about having some headroom but I don't subscribe to the notion that a speaker "needs" a certain amount of power to sound good, in this case the OP has the drivers program rating which for all but the most dynamic material is fully powered. And your description is just another way of describing a muppet operator that pushes a system beyond it's capabilities, it is my experience that this type of operator will always push the system too hard and it doesn't matter how it's powered or what the systems overall capabilities are. We have to assume the OP is not such an operator since this is his rig afterall. |
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5175 |
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When using a more powerful woofer in which the amplifier has difficulty to drive, the user will drive the amplifier harder in order to achieve the proper SPL. Unfortunately, the amplifier tends to clip under the given circumstances constantly in which, will lead to overheating the voice coil of the loudspeaker.
It is one thing to have headroom so you do not have to drive amplifier ragged and take advantage of the dynamics. It is another thing to not have enough volume in which, you will drive the amplifier harder until you reach the proper SPL. This is why many tend to use amplifiers that are 2 times the rated power to their loudspeakers. It will lead to achieving maximum output from the loudspeaker without clipping the amplifier during the process.
Best Regards, |
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Elliot Thompson
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2543 |
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I'm going to disagree with that for a couple reasons. A) it depends heavily on the program material in question, while a driver will generally handle more power with really dynamic music it could be in danger of failure at RMS levels with other genres. B) The difference between 750w and 1500w is 3dB which might just be enough to notice but this happens to be at the power compression end of the spectrum where voice coil heating tends to eat up most or all of that gain. So I'm of the opinion that the OP would be better off adding more cabs and powering them the same than adding more power to the existing cabs. I own some L18 851 loaded reflex subs.. dual 18 boxes actually, and at 1000w/driver I think they are fully powered, I'm actually afraid they are a bit overpowered for music genres with those long synth tones. The point I want to make though is that it takes 4 of these 18's to generate any appreciable amount of thump.. dynamic punch you can feel. A pair of reflex 18s can produce a good amount of bass but you're not going to get much kick drum punch.. that simply requires more air displacement, four 18's just starts to get into that zone. So how many of these compact subs do you have and what about the sound do you feel is lacking? They won't go super low by todays standards.. 40hz is probably where they should be high passed, and it's going to take a small wall of them to produce kick you can feel in large rooms or outdoors, so maybe your expectations are just too high.
Edited by Conanski - 12 July 2019 at 2:35pm |
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5175 |
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It depends on the TS Parameters of the driver. The most important TS figures for a reflex design is the fs, Vas and, Qts. If your aim is 50 Hertz, in which, the driver offers an fs of 50 Hertz, you should not tune the box to 50 Hz for, you are creating a response curve that will be -3 dB @ 50 Hertz. The VAS may allow you to go lower at the expense of a larger enclosure even if the fs is higher than expected. If the cabinet is too small, you can forget about the VAS helping you to go lower despite what the fs states. I have not seen a measured much less a simulated response of the Cubo 15 Extended so, I cannot say where the roll-off point begins on such a design. However, from what little response curve I could find on the Cubo 15, such a design would create the havoc you are describing using the RCF L 15 P 540 in the Cubo 15 enclosure. Best Regards, |
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Elliot Thompson
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Tonskulus
Registered User Joined: 15 September 2017 Location: Finland Status: Offline Points: 425 |
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Yes, I have tested different amps too (it was actually the first thing that came to my mind) which are excellent with my 18" hog-scoops, 18" reflex etc.. and giving good control for them. I also have small tops w/12" JBL 2206H's, those can take some serious punshment and not a single problem ever. No flapping, no bottoming like L15P540 does with same power levels..
I have four of them and was thinking to make some kick cabs with these. Elliott thank you! Need to try that. So never tune the reflex to around Fs of the driver? I think you are right, it has to do something with those enclosures.. Sorry, ot :) Edited by Tonskulus - 11 July 2019 at 5:33pm |
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JonB67
Young Croc Joined: 22 April 2016 Location: UK Status: Offline Points: 1376 |
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My subs used to lose control and go all flappy when pushed but it was the old amp losing control, not the drivers. My modern matrix amp drives them much harder without any flappiness!
Id try them on a different suitable amp before swapping out the drivers.
Edited by JonB67 - 11 July 2019 at 2:16pm |
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5175 |
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It may be the fs of the RCF L 15 P540 in the Cubo 15 Extended is around the resonant peak frequency of Cubo 15 Extended. This could lead to the driver unloading from the box and acting as if it is in free-air. Try sweeping (a slow sweep) a sine wave from 100 Hz to 40 Hz. If you approach 50 Hz - 40 Hz in which, you hear no sound however, the driver is moving erratically, that is the point the driver is unloading from the box. Best Regards, |
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Elliot Thompson
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midas303
Registered User Joined: 03 July 2019 Location: Barrow Status: Offline Points: 17 |
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Just out of interest, it wouldn't be the guys who sold you the amps that told you they can't be compared to new amps would it?
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Tonskulus
Registered User Joined: 15 September 2017 Location: Finland Status: Offline Points: 425 |
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Might be.. dual 15 is 220 litres, tuned to 45Hz or so. Cubo 15 extended.. in this box these woofers can handle more power compared to dual 15. When cone bottoms (bangs), I can see cone moving around 10-15mm which is no where near the Xlim. Not sure whats going on there.. Edited by Tonskulus - 11 July 2019 at 12:40pm |
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5175 |
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It could be the box is tuned too high. That is the only time I have seen woofers loosing control. Best Regards,
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Elliot Thompson
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