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Change woofer in very compact 18” sub

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serioussound View Drop Down
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    Posted: 10 July 2019 at 9:24pm
I recently bought some very compact 18” subs really cheap.

They are very small:
53cm wide
53cm deep
68cm height

Is it even possible to make a 18” sub sound good that small?

Woofer is RCF L 18 P540. These drivers dont handle so much power so I want to replace them. But with what? Is there any other 18” driver out there that plays good in such a small cab?

I want to keep them because they are really handy and well built cabs.

Maybe change baffle and put 15” in there? :/




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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2019 at 12:51am

How much power are you feeding the RCF L 18 P540? You are using the old RCF series in which, the power was conservatively rated. The cabinet is fine for the RCF L 18 P540. However, if you are looking for lots of 50 Hz – 40 Hz, you may find yourself living on your equaliser.


If you cannot feed that driver anywhere from 1000 – 1300 watts RMS, you are just going to make matters worse swapping to a modern day woofer. A modern day woofer will need even more power to drive to optimum levels.


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Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote serioussound Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2019 at 8:21am
I drive them with EV P3000. I just thought with 350 w power rating and only 3” voicecoil I would be better of with a more modern driver?

Would a modern standard 18 fit in such a small cab?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2019 at 11:27am

The EV P3000 offers 750 watts per channel @ 8 ohms. It is a good suggested match for the RCF L 18 P540 as, it delivers 2 times the rating of the RCF L 18 P540. I own a good amount of RCF L 15 P540 woofers and, each driver will get anywhere from  1300 - 1500 watts RMS (4 times the rating of the RCF L 15  P540 ) of amplification power. So, you can feed the RCF L 18 P540 1000 watts – 1300 watts as they both were rated the same when the RCF L 18 P540 was in production.


All the old RCF models were conservatively rated as they did not adopt the AES method of power rating.


Unless you blew the driver, there is no need to look for modern day drivers especially, if your biggest amplifier is a EV P3000. That is a small amplifier under today's standards as far as modern day woofers are concerned. So it is not a matter of if a modern day driver will work, it is not having a strong enough amplifier to drive a modern day driver properly will be your dilema.


The size of the voice coil and the xmax does not determine how much power a loudspeaker can handle in a reflex box. How the loudspeaker reacts in a reflex box (based on its TS Parameters) will determine its outcome in terms of performance.


Best Regards,




Edited by Elliot Thompson - 11 July 2019 at 11:37am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote serioussound Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2019 at 11:36am
Ok but just for interest is this a inflexible cab since its so small or can many modern drivers play good in such a small vab?

I have some rcf l18 851 kn laying around would they play good in these cabs for example (they are not new drivers I know)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2019 at 11:44am
Originally posted by Elliot Thompson Elliot Thompson wrote:

The EV P3000 offers 750 watts per channel @ 8 ohms. It is a good suggested match for the RCF L 18 P540 as, it delivers 2 times the rating of the RCF L 18 P540. I own a good amount of RCF L 15 P540 woofers and, each driver will get anywhere from  1300 - 1500 watts RMS (4 times the rating of the RCF L 15  P540 ) of amplification power. So, you can feed the RCF L 18 P540 1000 watts – 1300 watts as they both were rated the same when the RCF L 18 P540 was in production.


All the old RCF models were conservatively rated as they did not adopt the AES method of power rating.


Unless you blew the driver, there is no need to look for modern day drivers especially, if your biggest amplifier is a EV P3000. That is a small amplifier under today's standards as far as modern day woofers are concerned. So it is not a matter of if a modern day driver will work, it is not having a strong enough amplifier to drive a modern day driver properly will be your dilema.


The size of the voice coil and the xmax does not determine how much power a loudspeaker can handle in a reflex box. How the loudspeaker reacts in a reflex box (based on its TS Parameters) will determine its outcome in terms of performance.


Best Regards,



Yes, I have 15p540's too but they seem to go out of control around 1kW. Flapping, bottoming out no matter the high pass setting. Might be wrong enclosures tho, one dual manifold/reflex loaded and cubo 15 extended which I have tested with these.  Or possibly uneven cone load.. who knows. 

Otherwise good drivers and I do like the sound they make. 




Edited by Tonskulus - 11 July 2019 at 12:34pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2019 at 11:52am
Originally posted by serioussound serioussound wrote:

Ok but just for interest is this a inflexible cab since its so small or can many modern drivers play good in such a small vab?

I have some rcf l18 851 kn laying around would they play good in these cabs for example (they are not new drivers I know)


The cabinet is not small. You do not have enough power to drive modern day woofers properly. Instead of worrying about switching loudspeakers, invest in a more powerful amplifier. You would be surprised how well those RCF L 18 P540 will perform if you fed them more power.

This how it works. You always feed the loudspeaker more power than it is rated. The RCF L 18 P 540 is rated 350 watts. The RCF L 18 851 is rated 1000 watts. You have an EV P3000 amplifier that delivers 750 watts per channel @ 8 ohms. Which loudspeaker will be easier to drive on the EV P 3000?

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Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote serioussound Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2019 at 11:57am
Some guys I talk to says that for bass you cannot compare the real watts of EV P 3000 with modern amplifiers...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2019 at 12:06pm
Originally posted by serioussound serioussound wrote:

Some guys I talk to says that for bass you cannot compare the real watts of EV P 3000 with modern amplifiers...


If you want to believe them, its up to you.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2019 at 12:23pm
Originally posted by Tonskulus Tonskulus wrote:


Yes, I have 15p540's too but they seem to go out of control around 1kW. Flapping, bottoming out no matter the high pass setting. Might be wrong enclosures tho, one dual manifold loaded and cubo 15 extended which I have tested with these. 

Otherwise good drivers and I do like the sound they make. 





It could be the box is tuned too high. That is the only time I have seen woofers loosing control.

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Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2019 at 12:38pm
Originally posted by Elliot Thompson Elliot Thompson wrote:

Originally posted by Tonskulus Tonskulus wrote:


Yes, I have 15p540's too but they seem to go out of control around 1kW. Flapping, bottoming out no matter the high pass setting. Might be wrong enclosures tho, one dual manifold loaded and cubo 15 extended which I have tested with these. 

Otherwise good drivers and I do like the sound they make. 





It could be the box is tuned too high. That is the only time I have seen woofers loosing control.

Best Regards,

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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Post Options Post Options   Thanks (0) Thanks(0)   Quote midas303 Quote  Post ReplyReply Direct Link To This Post Posted: 11 July 2019 at 1:22pm
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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