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Old 8th February 2013, 04:09 AM   #11
OMNIFEX is offline OMNIFEX  Jamaica
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The problem he is going to face is power. As the frequencies go lower, the loudspeaker is going to require more current from the amplifier to give him the SPL (volume) he is seeking. Surely, if he can afford an RCF 18 P 300, he can afford a 200-watt amplifier, which will offer him less distortion in addition to more current on demand when the loudspeaker needs it in order to play lower frequencies.
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Old 8th February 2013, 06:16 PM   #12
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by umut1001 View Post
Hello.Does anyone have an experience on these drivers?Or some advice?I want to make a subwoofer with this and use it for home cinema and also for hi end system(2fullrange + subwoofer).I will use it for my 20m2 little saloon but in future i may move to a bigger house.In my country we can not find hi end subwoofers and i am tend to use PA woofers...

Hi umut,
Good idea, I have built/designed many 'subs' for flea-power amps....

Can it give good sound with low distortion between 1-10 watts power too?I do not know anything about this.
Waiting some reply.Thanks in advance.
Have a look at my suggestions. Both can be driven with a low power amp because the high inherited passband impedance is guaranteed when properly stuffing are applied in these quarter-wave designs.

The current consumption of both are lower than if substituted using an ordinary closed or ported design.

b
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Last edited by bjorno; 8th February 2013 at 06:18 PM.
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Old 9th February 2013, 12:13 AM   #13
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by bjorno View Post
Both can be driven with a low power amp because the high inherited passband impedance is guaranteed when properly stuffing are applied in these quarter-wave designs.
Hi Bjorno,

The Thiele-Small parameters of RCF drivers are measured after a 2 hour warm-up period of full power handling capacity!
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Old 9th February 2013, 11:07 AM   #14
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Hi.So what will be the technical differences between hot and cold driver?
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Old 9th February 2013, 12:30 PM   #15
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by umut1001 View Post
Hi.So what will be the technical differences between hot and cold driver?
Hi umut1001,

Djim is right, new High power PA drivers equipped with hard cone suspensions or drivers that have been stored over a longer period after manufacturing are prone to be stiff and have to be 'braked-in' to loosen up the suspensions in order to recover their advertised parameters.

If you have access to an 18-24V Rms >= 50VA(~2Amin) transformer connected directly to the speaker terminals to break in the driver suspension a couple of hours over a period of a few days...

Or by using a power amp and a tone generator set at a few Hz lower than fs where the cone excursion is suspension limited: The driver would show up consistent T/S that will remain very stable particularly if used on a daily basis in a speaker system.

b

PS: http://www.klippel.de/fileadmin/klip...Cooling%29.pdf
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Old 9th February 2013, 07:49 PM   #16
Djim is offline Djim  Netherlands
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Quote:
Originally Posted by umut1001 View Post
Hi.So what will be the technical differences between hot and cold driver?
Hi umut1001,

Yes, there is a significant difference between a 'hot' and a 'cold' driver. You need proper measurements of a 'cold' driver. Like Bjorno already mentioned, it needs first a break-in-period of the mechanical parts.
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Old 9th February 2013, 08:09 PM   #17
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umut1001,
Please don't confuse breaking in a driver with the change in impedance values you will see when a driver changes values due to heating of the voicecoil. When you take a driver and exercise it at high excursion with music or with a sine wave this is changing the physical properties of the spider and depending on the type of surround in a permanent way. Once these parts of the suspension are broken in no amount of sitting around is going to change them back to like new unused condition. Measuring the T/S values on a cold loudspeaker verses a heated driver will in fact give you different results. Keep this in mind when working with the values here. If you are only going to use low power amplifiers on a speaker such as the RCF the values you should aim for would not be the same as a PA company is going to need to work with that is driving the same speaker with a 1000 watt amplifier running at this elevated power level over many hours time.
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Old 10th February 2013, 10:35 AM   #18
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I want to use one of these PA subs because they have a very good Price quality ratio.They can be found easily here in my country.And also in future when i move to a bigger house i can also use them in every big place for music and cinema.Yes i will break it in.I hope it won't disturb my new neighbours while playing music/cinemaThanks everyone for suggestions.
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Old 10th February 2013, 11:09 AM   #19
epa is offline epa  Netherlands
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for home cinema ,you would be looking for a driver with a lower fs then that.imo.
also a common mistake is to look at the efficientie figur.
this tels you nothing how it wil preform in the sub range.
Quote:
rcf:3 Sensitivity measurement is based on a 100-500 Hz pink noise signal with input power of 2.83V @ 8 Ohms
Quote:
18sound:sensivity represents the averaged value of acoustic output as measured on a forward central axis of a cone,at a distance 1m from the baffle panel,when connected to 2,83v sine wave test signal swept between 100hz and 500 hz with a test specimen mounted in the same enclosure as given for(1) above
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Old 10th February 2013, 11:13 AM   #20
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We are looking at the graphic of SPL.Yes i know about SPL/Frequency graphics.They are much better than hi end subs i can buy at these prices.I will use active crossover and make adjustment
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