Sound expert required!

[yourdj]

can anyone explain to me in plain english the following :)

I have bought an LD Dave sub (12inch 300 watt sub - 100 watt satilites out x 2).

i have plugged my RCF 310a's in and they are as loud as they were before when used with this amp which is 400 watts a channel - http://www.thomann.de/gb/the_tamp_tsa_4700.htm

My mate said that its to do with the SPL (127) of the RCF's and 1000 watt is only half 100 watt apparently which does not make sense to me (i assume its logarithmic) :confused:

Quite happy however as it's saved me a fortune as i was going to buy a £2,000 Fohhn system but this will do me fine. :p

[Solitaire Events Ltd]

Explain what?

RCF 310A are active - why would you use active speakers with an amp?

[surround sounds]

Explain what?

RCF 310A are active - why would you use active speakers with an amp?

Yes
I was thinking the same:bang:

[Excalibur]

Due to the response of the human ear being logarithmic, to be twice as loud as a 10 watt system, assuming everything else is constant, you need not 20 watts, but 100 watts.

Twice as loud as 20 watts needs 400 watts.
Twice as loud as 30 watts needs 900 watts !! :eek: :eek:

If you were running the 310's with a 400 watt amp, then indeed you're unlikely to hear a lot of difference if you feed them 100 watts.

[Corabar Entertainment]

Due to the response of the human ear being logarithmic, to be twice as loud as a 10 watt system, assuming everything else is constant, you need not 20 watts, but 100 watts.

Twice as loud as 20 watts needs 400 watts.
Twice as loud as 30 watts needs 900 watts !! :eek: :eek:
:confused: :confused: But you can't hear watts :p :p :p :daft:

[sleah]

:confused: :confused: But you can't hear watts :p :p :p :daft:

I was thinking that too Angela!

A speaker capable of handling 50W but putting out 130db is going to be louder than a speaker capable of handling 500W but only putting out 120db.....

[yourdj]

Explain what?

RCF 310A are active - why would you use active speakers with an amp?

sorry 310 - Passives. :)


Due to the response of the human ear being logarithmic, to be twice as loud as a 10 watt system, assuming everything else is constant, you need not 20 watts, but 100 watts.

Twice as loud as 20 watts needs 400 watts.
Twice as loud as 30 watts needs 900 watts !! :eek: :eek:

If you were running the 310's with a 400 watt amp, then indeed you're unlikely to hear a lot of difference if you feed them 100 watts.

I think I understand? So the SPL is the most important thing when buying speakers?

What is RMS then as i understand that is a more accurate reading?

Sorry stupid questions :muppet:


A speaker capable of handling 50W but putting out 130db is going to be louder than a speaker capable of handling 500W but only putting out 120db.....

Thats the reason i got them. They are really good for 10 inch cabs. :)

[CRAZY K]

so the SPL is the most important thing when buying speakers?



Course not--- its the price silly;)

Seriously if you are happy with the sound--dont query it---enjoy:D

Sounds like a good set up to consider for the future when I CANT HEAVE THOSE PEAVEYS ON THE STANDS.

How many people will it cover comfortably ?

[Excalibur]

:confused: :confused: But you can't hear watts :p :p :p :daft:


I was thinking that too Angela!

A speaker capable of handling 50W but putting out 130db is going to be louder than a speaker capable of handling 500W but only putting out 120db.....

One disingenuous, and one who doesn't read what I write. :bang:

COMPARATIVE.

Which part of " Assuming everything else is constant" was difficult to comprehend? :confused: Of course if you change the Class D's for Peaveys, it'll be louder, you :muppet:

A system putting 10 watts into its cabs is half as loud as the same system turned up so that 100 watts go into them, with all compoments unchanged.


Angela, no indeed, you can't hear watts, but you can tell when I turn up the knobs on the front of the amp, and allow more of them into the cabs. ;)

[Corabar Entertainment]

One disingenuous, and one who doesn't read what I write. Now, I wonder which one of those I was? :D :D :D

[Tom]

RMS is an indication to tell you how much power you will need to reach the maximum SPL of the driver/s or cab as a total.

As already stated, a more efficient cab or speaker will give more output with less watts


So when you look a cabs, take a look at the SPL instead of how many watts the cab needs. The more SPL, the louder the cab will be.

[Excalibur]

Now, I wonder which one of those I was? :D :D :D

I composed a witty reply to that. This would be the shortened version.

:whistle: :zip: :D :D

[yourdj]

Course not--- its the price silly;)

Seriously if you are happy with the sound--dont query it---enjoy:D

Sounds like a good set up to consider for the future when I CANT HEAVE THOSE PEAVEYS ON THE STANDS.

How many people will it cover comfortably ?

Dont know. It was good in a marquee and a hall at the weekend :)
I would guess 200.

[Happy Jack]

Due to the response of the human ear being logarithmic, to be twice as loud as a 10 watt system, assuming everything else is constant, you need not 20 watts, but 100 watts.

Twice as loud as 20 watts needs 400 watts.

I'm a little surprised, Peter, as this isn't correct and Toby seems to have taken it on board...

Rule of thumb as to what is generally perceived as 'twice as loud' to most people is a 10dB increase for calculated acoustic intensity. This translates into factor of 10, and can be expressed in its simplest terms as -

10 log (P2/P1) = 10 log 10 = 10dB

So the red example should read 200, not 400 watts, and should be applied as such -

10 log (200/20) = 10 log 10 = 10dB

Likewise, a 20dB gain translates in to a factor of 100 and is twice as loud still. For those interested, it can also be expressed as -

10 log (2000/20) = 10 log 100 = 20dB
derived from
z = 10 to the power of (ΔL/10)
or
z = 10 to the power of (20/10) = 100
and
ΔL = 10 log z
or
ΔL = 10 log 100 = 20
where
z = Factor, ΔL = Level Change in dB

[Excalibur]

Apologies Jack, it's been a long time since I did logs. :o :o :o :o :o :o I stand corrected. I had square in mind, not log.

However, my point still stands that doubling the power delivered into a set of speakers may not produce a significantly louder sound, as perceived by the human ear.

[Happy Jack]

Absolutely no need to apologies, Peter! I just thought I'd make the distinction and elaborate a little for all those who care. I would agree with the way you put it forward - it is a concept that demands a little respect and, at least, some basic understanding.

[yourdj]

I'm a little surprised, Peter, as this isn't correct and Toby seems to have taken it on board...

Rule of thumb as to what is generally perceived as 'twice as loud' to most people is a 10dB increase for calculated acoustic intensity. This translates into factor of 10, and can be expressed in its simplest terms as -

10 log (P2/P1) = 10 log 10 = 10dB

So the red example should read 200, not 400 watts, and should be applied as such -

10 log (200/20) = 10 log 10 = 10dB

Likewise, a 20dB gain translates in to a factor of 100 and is twice as loud still. For those interested, it can also be expressed as -

10 log (2000/20) = 10 log 100 = 20dB
derived from
z = 10 to the power of (ΔL/10)
or
z = 10 to the power of (20/10) = 100
and
ΔL = 10 log z
or
ΔL = 10 log 100 = 20
where
z = Factor, ΔL = Level Change in dB

:what: ;) plain english :confused:

I think I get it? kind of. I did maths in my degree but never understood it then
Basically buy a speaker that has the max SPL rating :)

[csg]

yes, but take spl ratings with a big pinch of salt...

many manufacturers publish calculated rather than measured spl ratings, often ignoring the effects of power compression.

Power compression, which is an artefact of the higher coil impedance caused by heat when working at or near rated power effects all speakers to some degree, and can lower the output between 1 - 5db commonly. Only a few speaker manufacturers specify power compression, but no speakers are immune
So, measured spl rating tend to be much more accurate.

Then, you need to quantify the spl rating - some are given as continuous, others as peak, taking into account the peak power rating of the driver and measuring / calculating the peak output

This is commonly 6db higher than the constant spl output which can equate to 4 times the amplifier power, but if you are not aware that a spl rating is peak, it can distort how the performance of a unit looks on paper.

Of course, if you buy a new speaker system capable of say 125dBA cont., 131 dBA peak and wish to take advantage of the whole output, then you will need a power amplifier capable of providing CLEAN power bursts of 4 times the RMS rating of the speaker.....

so, basically, buy the speaker that sounds the best to you -use ratings as a guide, but never buy on them alone.

[CRAZY K]

yes, but take spl ratings with a big pinch of salt...

many manufacturers publish calculated rather than measured spl ratings, often ignoring the effects of power compression.

Power compression, which is an artefact of the higher coil impedance caused by heat when working at or near rated power effects all speakers to some degree, and can lower the output between 1 - 5db commonly. Only a few speaker manufacturers specify power compression, but no speakers are immune
So, measured spl rating tend to be much more accurate.

Then, you need to quantify the spl rating - some are given as continuous, others as peak, taking into account the peak power rating of the driver and measuring / calculating the peak output

This is commonly 6db higher than the constant spl output which can equate to 4 times the amplifier power, but if you are not aware that a spl rating is peak, it can distort how the performance of a unit looks on paper.

Of course, if you buy a new speaker system capable of say 125dBA cont., 131 dBA peak and wish to take advantage of the whole output, then you will need a power amplifier capable of providing CLEAN power bursts of 4 times the RMS rating of the speaker.....

so, basically, buy the speaker that sounds the best to you -use ratings as a guide, but never buy on them alone.

Most of us who have been around the block a few times and worn out a few T shirts ignore all the technical :Censored:

We use our ears--im glad to see you agree;)

[yourdj]

OK. Thanks for the help people!

agreed a good ear helps allot and having the eq set correct is paramount.


I was just having a look with alex at the little speakers the LD Dave system came with (which i have blown up) and they are 4ohms.

Basically the high end coming out of the sub is 4ohms into my RCF's (8 ohms).
Has this anything to do with why its pretty loud too and is it dangerous to run them on this system?

[Excalibur]

OK. Thanks for the help people!

agreed a good ear helps allot and having the eq set correct is paramount.


I was just having a look with alex at the little speakers the LD Dave system came with (which i have blown up) and they are 4ohms.

Basically the high end coming out of the sub is 4ohms into my RCF's (8 ohms). Has this anything to do with why its pretty loud too and is it dangerous to run them on this system?

Panto time again:
" Oh no it isn't "

I can't muster the energy for the long explanation, but anything you feed the little cabs with is exceedingly unlikely to damage the RCF's , as long as you haven't got as many red lights as a dodgy Amsterdam street.

[yourdj]

Panto time again:
" Oh no it isn't "

I can't muster the energy for the long explanation, but anything you feed the little cabs with is exceedingly unlikely to damage the RCF's , as long as you haven't got as many red lights as a dodgy Amsterdam street.

nah, I tried to clip it the other night but nothing :)

[ppentertainments]

Most of us who have been around the block a few times and worn out a few T shirts ignore all the technical :Censored:

We use our ears--im glad to see you agree;)
WOW - that's the most sensible post I have read concerning speakers. :)

Figures mean nothing, have a listen, if they sound good and within price range, buy them.

[CRAZY K]

WOW - that's the most sensible post I have read concerning speakers. :)

Figures mean nothing, have a listen, if they sound good and within price range, buy them.

Common sense--yes thats something thats often missing isnt it these days--most of the schmucks who ring us for the cheapest quote appear to have very little;)