power handling question

[paulspencer]

What happens to the power handling of a driver when you change the bandwidth?

1. Vifa P13 midbass driver has 40 watts rms. Suppose it is crossed over at 200 Hz with a 4th order high pass filter? I assume that the power handling would increase significantly, but how much more could you expect from this driver? 60 watts? 80 watts?


2. What happens to the power handling when it is combined with another P13 wired in parallel? Does the power hanlding double? Stay the same?

Thanks for your help,
regards,
Paul

 

[sreten]

The power handling issue is more complex than you suppose.

For the P13 I presume its thermal limits are 40Wrms continuous.

This is appropriate for up to 100W program handling.

Used as a midrange unit with filtering 200w program handling.

Used in parallel power handling does double, but twice the
current is drawn, so they can't really handle a bigger amplifier.

🙂 sreten.

 

[wintermute]

Hi Paul,

Another thing that I was very surprised to find was that rated power often has nothing to with what power you can apply to the speaker and have it stay under it's xmax. I was modelling a speaker rated at 150W RMS and the modeling program was telling me it could only handle about 12W because that was the power it reached xmax at low freqs. In this case the driver wouldn't be damaged but it would be distorting... (although I have since read that the morel drivers are quite good when pushed past the xmax).....

I posted here about it, and the guys sorted me out 🙂

http://www.diyaudio.com/forums/showthread.php?s=&threadid=19023&highlight=

Regards,

Tony.

edit: Just realised that this is a bit irrelevant considering you were asking what happens when you change the freq range the driver is operating over, but I guess to redeem myself, I can say that as the freq goes up the driver excursion goes down, so the higher the freq you cross at, the higher the power you can drive it at without getting distortion (due to exceeding xmax) 🙂

 

[paulspencer]

The power handling issue is more complex than you suppose.

Actually, I suspected it was and that the only way to really be sure is to try it out. My general philosophy is to operate all parts of an audio system well within their limits. That's why I have two AV12 subs (more than I need, they have a lot of headroom) ... but that's another topic!

For the P13 I presume its thermal limits are 40Wrms continuous.

That would be my assumption as well. They can't really indicate xmax limited power, as it will vary with too many factors.

This is appropriate for up to 100W program handling.

I had thought that this driver would then be appropriate for 40 watts rms program material. So, a typical hifi mid powered amp with say 40 - 80 watts would be appropriate for a bookshelf with this driver. Are you saying, then, that this driver in a bookshelf should be rated at about 100 watts?

Used as a midrange unit with filtering 200w program handling.

This is sounding good

Used in parallel power handling does double, but twice the
current is drawn, so they can't really handle a bigger amplifier.

Now that part is confusing! Can you elaborate a little more? ...

regards,
Paul

 

[paulspencer]

Tony,

yes, it would seem that in midbass drivers, the xmax can be a big factor in the power handling ... well especially for me as I have been known to boost the bass! (not anymore, I now have subs so the mains can rest easy)

Just realised that this is a bit irrelevant considering you were asking what happens when you change the freq range the driver is operating over, but I guess to redeem myself, I can say that as the freq goes up the driver excursion goes down, so the higher the freq you cross at, the higher the power you can drive it at without getting distortion (due to exceeding xmax) 🙂

It's the reason I posted - to find out what the impact on power rating is when xmax becomes less of a factor when used as a midrange driver. (so it is still relevant, even if not the whole answer)

regards,
Paul

 

[sreten]

I had thought that this driver would then be appropriate for 40 watts rms program material. So, a typical hifi mid powered amp with say 40 - 80 watts would be appropriate for a bookshelf with this driver. Are you saying, then, that this driver in a bookshelf should be rated at about 100 watts?

Yes that's basically it.

Music signals are not RMS waveforms. When the amplifier is
clipping occasionally on music program average power is likely
to be 5 to 20 W rms, lower for very dynamic program.

Playing music its impossible to get near the actual RMS output
of an amplifier, even with lots of clipping, if you try this your
tweeters will fry way before you succeed.

But it does depend on the bass content of the type of music you
want to use with the driver, and the bass alignment of the driver.
You can't use small drivers for dub reggae.

A similar driver has been shown to be able to accept 1Kwatt
transients in the midrange without distress, but these tests
used music material with a very wide dynamic range.

Now that part is confusing! Can you elaborate a little more? ...

When you put two drivers in parallel power handling doubles.
Effective sensitivity goes up up 6dB.

But the effective impedance is halved, so current drawn doubles.

So if the amplifier is capable of doubling its output power when
the load impedance is halved you will not need a 'bigger' amplifier,
you will be extracting more 'juice' out of the amplifier you have.

🙂 sreten.

 

[Bull]

reply

Power handling really depends on the application,required volume level and length of time played at that level and what frequency and what music.

eg:So for deep bass music played at high volume levels for hours and hours on end u need high power drivers of about 150w rms +