Crossover and Nominal frequencey of speakers.

[yahoo0212]

This thread can elaborate on the effect of crossover on different speakers......

Considering the ""classical"" example of Wharfedale 9.5 vs 10.7 ...
Both these speakers are same in respect to all the specs...including dimensions but they only differ in terms of Crossover and Nominal Frequency

in the above example both the speakers have same drivers, (only slight diff is in the wattage .. former is 30-150w and the latter is 20-150 watts) I hope that does not matter much....

In terms of Crossover........!
Wharfedale 9.5 has a crossover of 140hz, 2.2 kHz
with a nominal frequency of 30-24 kHz at -6db
while
Wharfedale 10.6 has a crossover of 100hz, 2.5 kHz
with a nominal frequency of 35-24 kHz

Referring to these specs.. how can one judge the quality or lets say what has the crossover to do with the SQ of d speakers... Can anyone elaborate on these soecifications..!!

thanks .. Yahoo !

 

[doors666]

specs dont matter. the nominal freq doesnt matter, one is an unqualified number (at what db?). the crossover freq just depends upon the specs of the drivers and design of the crossover. these numbers dont mean squat.

 

[yahoo0212]

It has got to mean something... !! i don think they just put up dis on the spec sheet

 

[venkatcr]

in the above example both the speakers have same drivers, (only slight diff is in the wattage .. former is 30-150w and the latter is 20-150 watts) I hope that does not matter much....

In terms of Crossover........!
Wharfedale 9.5 has a crossover of 140hz, 2.2 kHz
with a nominal frequency of 30-24 kHz at -6db
while
Wharfedale 10.6 has a crossover of 100hz, 2.5 kHz
with a nominal frequency of 35-24 kHz

Though I wont be as abrupt as Doors, let me try to explain these terms for you.

Power wattage is something a lot of people have asked me. When you say a speaker has a power wattage of 30-150W, what does it mean? Well, a number of things. Very simply put, the speaker needs a minimum of 30 watts to squeak, and will blow itself off at more than 150 watts.

Let us compare two speakers. One is 200 watts and the other is 100 watts. Which is better? You cannot say that without understanding the sensitivity of the speakers. Let us say the 200 watts speaker has a sensitivity of 94dB, while the 100 watts speaker is rated at 98dB. Which is louder? The 100 watt speaker will produce a SPL of 120dB, while the 200 watt speaker will product an SPL of 122 dB. These figures are very close to each other and does not mean much to human ears. What it does mean is the first speaker needs twice as much power as the second one to create the same sound level.

Crossover frequency refers to the frequency that is spent to the drivers within the speaker. When you say crossover of 100hz, 2.5 kHz, the woofer gets a max frequency of 100Hz, the mid driver between 101hz and 2500 Hz, and the rest is sent to the tweeter. When you say 'a nominal frequency of 35-24 kHz' what it means is that the speaker can handle the frequency range specified.

To a certain extent, all these matter when you match a speaker to a amplifier. It also matters when you decide what frequencies (genre of music) you want to listen to. If you are a metal head used to listening at high volumes you should look for speaker with high sensitivity and a very low frequency handling capacity.

Cheers

 

[jaudere]

For end user, it really doesnt mean anything. But if your question is academic, you need to read a lot at least about passive crossovers. I had a thread related to this called ' crossover question'. I am on mobile. So cannot provide link. But search all the threads started by Jaudere & you will get it. Unfortunately, a member called Cranky has left the forum and all his posts have been deleted. His posts were very informative.

To tell in short, every driver plays well over a frequency range. For e.g. If your woofer plays well from 60hz to 2000hz(you have see the frequency response curve for this) and tweet plays well from 1.5k hz up, you have to have cross over between 1.6 and 1.8hz. Cross over point below 1.5 will damage tweet because it will be fed with frequ it cant handle. If it is above 2khz, no problem for tweet but woofer will not play well the frequ above 2khz. So you will miss important sound.
It also depends upon how steep is the xo curve. If it is first order, it is better not to set the xo near extreme end of frequency range of driver. If it is 4th order (very sharp cut off) it can be near extreme range of frequency. But then the frequency range of woofer & tweet should overlap considerably.
Feeding higher frequency into woofer does not damage it but you miss sound. Feeding lower freque into tweet than it can handle will damage it.

The wharfs in question,even though looking similar on paper, must be having different driver properties(mainly the frequency response curve). That is why xo points are different.

I hope this solves your query somewhat. But do read cross overs and how they function. It is a very intersting topic.

By the way what is 'nominal frequency'?. I have heard nominal impedance.

 

[jaudere]

more about frequency response curves

How frequency response is plotted?
The driver is fed with different frequencies at same power i.e. Watts say 1 watt. E.g. for woofer , a single tone for each frequency starting from 30 hz to 10khz. A graph of the SPL(Sound pressure level , a measure of loudness) that is produced is plotted for the range using special measuring equipment (I think it is called SPL Meter but not very sure).
In our example suppose it produces 80db SPL At 30hz, 85 at 50hz, 90 db from 60 hz to 5khz, again 85 at 8khz & 80db at 10khz.
So apparently the woofer is producing audible sound from 30hz to 10khz but for sounds below 60 and above 5khz, you will have to pump in more watts to get easily audible sound. This is ok if you are playing single tone at a time. But in music multiple frequencies are playing at the same time and by pumping in more watts, you will make everything loud.

So in our example, usable or practical frequ is between 60hz and 5khz. The specs will say 30hz to 10khz at -10db. However if you see the frequency response curve, you will immediately know that meaningfull range is 60hz to 5 khz. Accordingly you have to select your crossover point: 80 hz between woofer & bass driver , 4khz between woofer & tweet. Here you will be in soup if you take 30hz & 10khz as xo points without understanding the curve and what that -10db in the specs means.

This will shade some light on why xo points are different in two models of the said wharf. With the same logic you will understand that you should not interchange the drivers.

Is there any way to increase the response of our driver in example below 60hz & above 5khz?. Yes:

1)you need to use equalizer at that frequency but this will distort sound.

2) you design the speaker box :sealed/ported/others to enhance lower frequency.

Many drivers dont have smooth frequency response curve. In our case, if the driver has sudden dip at say 1khz, it is a bad driver and nothing but equalization at 1khz will be of some help.

Room acoustics also produce dips & peaks in the response. That is where equalizers are really useful.

To make a driver with smooth frequency response curve is a difficult art and thats why good drivers are costly. Otherwise you get 12" driver for rs 700 (like i am using in my open baffle) and leave everything to chance.