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PA Systems A forum for discussion of all parts of a sound reinforcement or DJ system: loudspeakers, mixers (desks) etc.

Not satisfied with my 8 RCF 4Pro subwoofers, need help going lower.
Not satisfied with my 8 RCF 4Pro subwoofers, need help going lower.
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Old 8th January 2019, 10:57 PM   #11
Think is offline Think  Netherlands
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Not satisfied with my 8 RCF 4Pro subwoofers, need help going lower.
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Originally Posted by GM View Post
.... stacked across the floor to create a line array to drop the system a 1/2 octave [0.707*40 = ~28.28 Hz].
.....
As far as I know this is not true, any source/weblink?
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Old 9th January 2019, 12:31 PM   #12
steveu is offline steveu  United States
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Originally Posted by Think View Post
Boost 3dB @40hz, cut 10dB from 50hz up and run them with more power or put them together in a corner or at least against a wall.


// the rolloff is so big, stuff the ports with socks/towel (the tuning will go down) or close it completely.
Back in the day, we made our own electronic cross-overs which included a "bump-and-roll" on the low end. This was a ~40Hz high-pass Sallen-Key where the Q was deliberately increased so that a bump was created, boosting the lowest bass just above where it blocked sub-sonic frequencies.

BTW, a sealed box for bass has to be huge. An 18" driver needs a ~64 cubic foot box . In fact, using a smaller driver is a way to get bass from a smaller box, but of course the driver is going to max out quickly.
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Old 10th January 2019, 09:04 AM   #13
chris661 is offline chris661  United Kingdom
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Originally Posted by steveu View Post
BTW, a sealed box for bass has to be huge. An 18" driver needs a ~64 cubic foot box
Steve, I'm not sure where you got this from, but it looks like you have a lot to learn. The cabinet size will be determined by the T/S parameters of each individual driver - saying that all 18"s need 64cu.ft is like saying all cars need 1000 gallons of fuel to make a journey.

Well, which journey?
Which car?
Etc.

Please do some more reading around before spreading misinformation like this.

Chris
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Old 10th January 2019, 10:31 AM   #14
Damo s is offline Damo s  United Kingdom
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Some modern productions in dance or R&B are very unforgiving. A couple of minimal / deep tech tracks I've bought recently have kick drum tails utilising sub at D1 (36.7hz), and even worse a few RnB tracks played on the radio are using a C1 (32.7hz) sub bass note. Reproducing C1 at the same level as C2 (65.4hz) is going to require a huge amount of power (double?).

Its all very well using these frequencies in tracks, moving away from the typical 49hz to 60hz range of old. Most club systems I've played on are simply not up to the job and such tracks will sound gutless so they are somewhat unplayable at live performances.

R&B is definitely the worst offender of late and between certain producers there seems to be some sort of competition on who can get away with using the lowest sub bass note. Whilst the tracks may sound amazing on the right system it will be expensive trying to reproduce them at a decent level.
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Old 10th January 2019, 07:22 PM   #15
steveu is offline steveu  United States
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Originally Posted by chris661 View Post
Steve, I'm not sure where you got this from, but it looks like you have a lot to learn. The cabinet size will be determined by the T/S parameters of each individual driver - saying that all 18"s need 64cu.ft is like saying all cars need 1000 gallons of fuel to make a journey.

Well, which journey?
Which car?
Etc.

Please do some more reading around before spreading misinformation like this.

Chris
Normally I would agree, but this lad is not interested in anything but ~40Hz bass, so normal enclosure design goes out the window. My point is that wrapping a driver in a box no bigger than contains the driver will kill any low frequencies. Sealed boxes are not recommended professional use.

Last edited by steveu; 10th January 2019 at 07:33 PM.
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Old 11th January 2019, 12:03 AM   #16
kipman725 is offline kipman725  United Kingdom
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I have some sealed subs used for small scale PA. I can do a house party with 6*15" drivers down to 20Hz just about, any less and I would be hitting the limiters too much. They are good if you want something compact ISH that can go low. They are however will be bad for almost everyone else:
1. Huge power requirements below tuning
2. Boxes get hot as hot air can't get out and your dumping a lot of power
3. You need lots of displacement which means lots of big drivers
4. Lots of EQ needed to get low with very undersized boxes.

Work for me but I'm not professional and need to hit 20Hz. I'm not sure if this is clear but my boxes are opposed for maximum output not flat response so I'm only using 200L for each 4 drivers.

Last edited by kipman725; 11th January 2019 at 12:06 AM.
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Old 11th January 2019, 08:13 AM   #17
chris661 is offline chris661  United Kingdom
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Originally Posted by steveu View Post
Normally I would agree, but this lad is not interested in anything but ~40Hz bass, so normal enclosure design goes out the window.
No, it doesn't.

The usual speaker design rules still apply. Here on this forum we've got tapped horns going to 25Hz at PA levels.
My compact 15" subs are flat to 40Hz. It's not a big deal to reach that low.

Chris
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