Hi, I just finished a pair of subwoofers for at PA system each with a RCF L15P540 driver 
I got some advice in a previous post as to how I should design the ports: http://www.diyaudio.com/forums/subw...air-15-sub-boxes-fit-rcf-l15p540-drivers.html
Photo of one of the subwoofers
The boxes' final volume is 116 liters. I went with two 10,5 cm ports of 9cm length.
Happy and expectant I fitted the drivers and fired up the amp (an STK VS-20 with 2x 600Watt in 8ohm RMS) - disappointment. The boxes sound horrible. Indistinct, muddy and cloudy. The drum/bass is super weak (not very loud) and totally lacks stiffness and distinction, sound is just blurry - the question is, what did I do wrong?
The boxes are constructed from 19mm wood board. They are glued/screwed together. They are 100% air tight (except for the ports of cause). i did a bit of extra stiffenings inside the boxes using a central cross (see image).
Photo of the inside
(note that there is no dampening material in the boxes as per suggestion, since it's a PA system)
I tried with different length ports (of same diameter) in lengths from 5 to 20cm - no luck, still horrible.
I'm ready to try any suggesting, change box design, change drivers...
PS I use an electronic crossover on the signal before the amp, so no filter in the boxes.
I got some advice in a previous post as to how I should design the ports: http://www.diyaudio.com/forums/subw...air-15-sub-boxes-fit-rcf-l15p540-drivers.html Photo of one of the subwoofers
The boxes' final volume is 116 liters. I went with two 10,5 cm ports of 9cm length.
Happy and expectant I fitted the drivers and fired up the amp (an STK VS-20 with 2x 600Watt in 8ohm RMS) - disappointment. The boxes sound horrible. Indistinct, muddy and cloudy. The drum/bass is super weak (not very loud) and totally lacks stiffness and distinction, sound is just blurry - the question is, what did I do wrong?
The boxes are constructed from 19mm wood board. They are glued/screwed together. They are 100% air tight (except for the ports of cause). i did a bit of extra stiffenings inside the boxes using a central cross (see image).
Photo of the inside
(note that there is no dampening material in the boxes as per suggestion, since it's a PA system)
I tried with different length ports (of same diameter) in lengths from 5 to 20cm - no luck, still horrible.
I'm ready to try any suggesting, change box design, change drivers...
PS I use an electronic crossover on the signal before the amp, so no filter in the boxes.
Attachments
P.s.: from the modeling point point on you didnt do anything wrong from the alignment...173 squarecentimeters with a length of 9 should have a minus 3 db point around 46 hz with an average of 98 db on the ground...BUT...you do not "feel" bass the same way as a loud high mid frequencys, so dont bother because of this ether! .
Swann.
.Swann.
you could try some sort of damping - maybe the back, bottom and one side. Does F3 calculate around 50Hz? those are nice specs on that RCF and more of an upper bass type driver relative to today's funky drop bass stuff. Maybe tailor the response more if doable in your setup, a bit of boost at port tuning.
Besides theres this "rule" for bassreflex...everyone tend to use, ( i even tend to give it a little bit more than this), it says...do not make the port smaller than one third of the drivers cone size.
In this case i would say at least 280 till 300 squarecentimeters...if you wanne take it easy just onr more vent with these 10,5 cm and you will and up with 260 cm^2 and you'll have to make them 15 cm long for the same alignment.
Swann.
In this case i would say at least 280 till 300 squarecentimeters...if you wanne take it easy just onr more vent with these 10,5 cm and you will and up with 260 cm^2 and you'll have to make them 15 cm long for the same alignment.
Swann.
This is not true. Driver break-in has been disproven by several people who measured T/S parameters before and after long hours of high excursion free-air break-in. Statistically insignificant differences.
On the other hand, drivers do change parameters over very long periods (years) of use. Magnets lose strength from age and heating cycles and surrounds and spiders lose stiffness. But this is not relevant unless you're working on very old speakers.
Hi NielsK,
Post #7: "... at least 280 till 300 squarecentimeters..."
I'll attach a quick simulation using Hornresp w/ 4ea. 10.5cm Dia. ducts. That might help as it also reduces the Vnet a little bit.
Have you measured the T/S parameters, and compared them to the manufacturer's?
Regards,
Post #7: "... at least 280 till 300 squarecentimeters..."
I'll attach a quick simulation using Hornresp w/ 4ea. 10.5cm Dia. ducts. That might help as it also reduces the Vnet a little bit.
Have you measured the T/S parameters, and compared them to the manufacturer's?
Regards,
Attachments
If you do not have a proper woof in your system, a sub woofer sounds like a wet f@rt. Too many people are of the wrong impression, a sub-woofer is there to extend the bass an octave or so lower than the woofer.
A sub-woofer does haven exactly what you tell us: "Indistinct, muddy and cloudy. The drum/bass is super weak (not very loud) and totally lacks stiffness and distinction, sound is just blurry - the question is, what did I do wrong? "
What is wrong? It is a sub-woofer, try adding a woofer to the system.
A sub-woofer does haven exactly what you tell us: "Indistinct, muddy and cloudy. The drum/bass is super weak (not very loud) and totally lacks stiffness and distinction, sound is just blurry - the question is, what did I do wrong? "
What is wrong? It is a sub-woofer, try adding a woofer to the system.
A student compiling a mobile disco came to me to develop a 3000 watt sub-woofer amp. I recommended that he see a doctor because having this high powered sub-woofer without the other necessary drivers at an equal sound pressure level, will guarantee that his audience would leave there sick as dogs and not recommend him for any further gigs.
A sub-woofer added to a system is adding final refinement to get the whole sound balance right, The other speakers in your system: woofers; percussion mids and tweeters are all part of the overall equation.
Stop dreaming and slot the blocks in where they should go, tweak the overlap frequencies and phase and levels so there is a smooth progression from one driver to the next, then slap on a CD.
You may have to tweak your system for various clubs and open air stints.
A sub-woofer added to a system is adding final refinement to get the whole sound balance right, The other speakers in your system: woofers; percussion mids and tweeters are all part of the overall equation.
Stop dreaming and slot the blocks in where they should go, tweak the overlap frequencies and phase and levels so there is a smooth progression from one driver to the next, then slap on a CD.
You may have to tweak your system for various clubs and open air stints.
This would make sense if you were aiming for a flat frequency response all the way down, but especially for dance music that is NOT the case.
https://soundforums.net/forum/pro-a...jbl-srx728-vs-eaw-sb1000z?p=120872#post120872
As Ivan (who I trust) says, you can need up to 25db more headroom at your lowest frequencies than your full range signal. That LF 'haystack', as some people call it, is what it takes to make dance music sound right at high volumes.
To me, 3000watts sounds 100% reasonable for a semi-small mobile setup. I'm running 2kw through mine, and given that my tapped horns easily use half the power of what it would take a reflex setup to hit similar SPLs, I don't see an issue.
Edit: To clarify, I'm talking about JUST sub power here. Stuff crossed under 90hz.
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For small to medium mobile disco gigs I used to use a 225WRMS power amp with 4 Fane 12-50 speakers.
So 2kw to 3kw is only twice as loud so will be in the ball park.
fitted the drivers and fired up the amp - disappointment. The boxes sound horrible. Indistinct, muddy and cloudy. The drum/bass is super weak (not very loud) and totally lacks stiffness and distinction, sound is just blurry - the question is, what did I do wrong?
Probably nothing at all if you were listening to the subs alone.. that is exactly how a sub will sound on music without the rest of the sound system playing. Run a tone sweep through them to verify tuning and if that sounds clean then just hook everything up and balance the subs with the mains playing tracks you are familiar with. You will need a low cut filter to protect the drivers below tuning and the sub/mid crossover should be in the 80-120hz range depending what mids they are crossing over to.
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Hi NielsK,
I basically agree w/ Post #18 by conanski, with the exception of the available upper frequency range; that could easily be increased depending on you system requirements. Most definitely use a high-pass filter. I'll attach a simulated filtered bandpass response from the Hornresp simulation posted in Post #12.
Regards,
I basically agree w/ Post #18 by conanski, with the exception of the available upper frequency range; that could easily be increased depending on you system requirements. Most definitely use a high-pass filter. I'll attach a simulated filtered bandpass response from the Hornresp simulation posted in Post #12.
Regards,
Attachments
With the advent of cheap, powerful class D amplifiers, a couple of kilowatts in LF is pretty standard
By all rights, these cabs should sound quite decent. I trust RCF specs to be somewhere near accurate, which makes me wonder about the rest of the setup.
What amp was used, were the drivers definitely in phase, etc etc.
Chris
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