Effect of exceeding XMAX in real life

jondoe

Member
2004-10-08 8:06 am
Hello all.
I apologise if this question has been raised before on these forums but i haven't been able to find it using the Search facility.

As the title suggests, i want to know what are the audible effects of going over the xmax excursion in a fullrange driver. Now, there is the theory that says this and that. What i really want to know is what gets to the ears if a fullrange speaker in a cabinet that goes down to 40-50Hz goes beyond xmax.
As you probably know, these babies don't have breathtaking excursions, at most 2-4 mm.
I am interested of this because i want to build me some speakers and decided to do some form of woofer/satellite combination. As you probably figured by now, i want the satellites to be fullrandes.
On my herculean task of finding suitable drivers i managed to reduce the list down to these two (well, not really two):
- Visaton B200
- Paudio coaxials (BM 12CXA/BM12CX38 or theyre smaller sibblings).

You may wonder, with such excellent drivers such as FE206e and Jordans and what not, what came to this guy to pick on exactly these ?
Well, glad you ask. There aren't any others around here. No, seriously. There aren't really any speakers around her worthy enough (basically, except Visaton all you can get is PA speakers-most are not even close to fullrange, car speakers, and junk speakers).

I've had these babies checked using unibox in whatever enclosure there was. At full power, all exceeded Xmax under 150/200 or even 300Hz.
I can get the excursion to stay within Xmax for down to 40Hz but i would have to feed them at most 50W.
Does that compute ? or shoul i just let it go let's say double the XMAX ? (alltho i wouldn't gain much).

I am concerned about this because if i buy a pair of these, i won't have the money to buy some decent woofs to go with them for something like 6 months to a year so using these as complete speakers is a must.

PS
I know 50W is a lot more than needed for a 3/4m room especially with the high SPL these things have but i don't want my satellites to be 200L (that may make them bigger than the woofers :bawling: )
I await your input.
 

soongsc

Member
2005-03-26 2:31 pm
Taiwan
I had the same question in 1990. And I was asked to do my own tests.:bawling:

Normal drivers are rated by continuouse steady power we refer to as rms. Music in not one frequency, and you are not continously playing at high power, it is the dynamics that gives use the sensation. Most drivers will take twice as much music power without exceeding XMAX.

If you really need all that XMAX, double the driver count and you can get the same pressure level at reduced travel.

When you design a speaker system, if the type of application is already acounded for, this situation is not a problem.;)
 

jondoe

Member
2004-10-08 8:06 am
Most drivers will take twice as much music power without exceeding XMAX.
If you are in the right frequency band, yes. If you go below the specified band, 50% to 10% of Pmax to load the driver is not uncommon (the lower f goes, the lower the power you can feed it).
If you really need all that XMAX, double the driver count and you can get the same pressure level at reduced travel.
I don't need all that XMAX. I have these drivers. Now i'm designing them some enclosures. No matter what kind, size, etc of enclosure, under 150 (or even 300) Hz i exceed Xmax.
Meaning, (in my opinion), if i want the specified Power i need to cross it higher (eg. 200-300Hz). I don't necessarily need that much power and if i want LFE i need to feed it max 50W (even if the speaker has 300W RMS).
Thing is i can easily exceed Xmax without wanting and i was interested if i will "hear things".
I've seen all kind of enclosures (close, vented, TL, horns built around these drivers, some horns excessively big, think 300 litres) and was wondering how it was possible to not exceed xmax. My answer was lower Power, like 50W for a 300W driver.
When you design a speaker system, if the type of application is already acounded for, this situation is not a problem.
Who said designing was easy ?:bawling:
When you exceed Xmax in real life the distortion will skyrocket, then if you push it too far, the voicecoil might hit the backplate and you risk breaking the speaker.
Thanks bigtime. I will never go as faar as Xlimit.

So any of you guys ever built such a monstruosity ?
I am interested in plans, info, whatever.
 

jondoe

Member
2004-10-08 8:06 am
joensd,
Nice box plans. However the max Power still stands. 40W. (well, i know, speaker power is still 40W and with music, you get 20W bass 8W mid and 2W hi so...). I don't understand very well german but i got it.
simon5,
i know, less is good, but what about the unexpected? What if something goes and i get big power on the outputs ?
This is somewhat of a moot point if i use an active setup with sub (which i will).

However, some things still persist. Which one of the two shoul i choose?
Visaton: little cheaper (not alot), probably more musical, not a great deal of power, many regard it as excellent, somewhat limited in very hi freq hi's.
Paudio: little more expensive, probably not as musical, a whole lot more power, many see it also as excellent, is coaxial therefore has strong mids and very strong hi's up to the sky.

Premises:
small room 3/4m
like the music to be pleasing, not annoying or downright impossible
have a lot of amp power to spend
money is not necessarily an isuue (for the following year, :devilr: )
 

soongsc

Member
2005-03-26 2:31 pm
Taiwan
I think with that size room, almost any driver would do. It is not likely that you will reach XMAX. The only time I have seen drivers reach XMAX are trying to play the 1812 cannoms:devilr: Not something a normal person would do all the time.

The reason some drivers are designed to take larger power is because these would most likely be used for public listening and the volume would be continously high, thus the need to dissipate power so that the drivers do not overheat.:hot:

I think you will not have to worry about this until you have overpowered your first pair of speakers and experience the excitement of seeing smoke.:eek:
 

Ron E

Member
2002-06-27 10:41 pm
USA, MN
It usually takes more than the predicted amount of power (some 2-4x the power) to reach Xmax than the power that software predicts. The stiffness vs excursion is a curve that gets steeper the farther the cone moves.

The farther the cone moves out of the linear range, the more the peaks are rounded off - sort of soft clipping. By the time Xmax is reached it will be at about 10% distortion, depending on how Xmax is defined.
 

jondoe

Member
2004-10-08 8:06 am
Thanks guys.
I understand the software simulates excursion using only the fundamental, no harmonix, no nothing. And music is nowhere near that. Basically i would have low freq. only about 50% from total power.

P.S.
Now i have to make my mind on which of these two i have (want) to buy. And since they're pretty expensive (for me), i didn't want no magic smoke :( out of them.
What's your opinion on them ?
Which one is worth now that xmax is taken out of the picture ?

good day (or night).
 

jondoe

Member
2004-10-08 8:06 am
Visaton
P 40W
Le 0.5
Bxl 3.9
Qt 0.75
SPL 96

Paudio BM12CXA
LFunit
P 300W
Le 0.75
Bxl 13.58
Qt 0.352
SPL 96
HFunit
P 60W
SPL 106
They're not really the same.
Somebody built a horn with the Paudio and says sounds CORRECT.
Nobody i know ever heard the Visaton.
I heard neither :bawling:
 
Ron E said:

The farther the cone moves out of the linear range, the more the peaks are rounded off - sort of soft clipping. By the time Xmax is reached it will be at about 10% distortion, depending on how Xmax is defined.

I tested 3 car stereo's (single fullrange driver/side) so far with the SPLmeter I bought a week ago. I think you can easily hear what happens once you reach Xmax.

By the time you reach 97dB, you notice the bass is not so dynamic anymore, hence the compression starts to kick in. Still no distortion on the bass dough.
If you keep turning the volume up, the measured SPL starts to roll of till at around 103dB it doesn't goes any louder. The highs keep getting a bit louder if you turn them up more, but distortion is noticeable, especially during the basskick you have a SLIGHT *krrrk* *krrrk* krrrrk* sound. You are putting like 30 watts in them at that moment, and that is usually the most a standard radio can do. I didn't turn it up further than that, since the SPLmeter didn't give any more progress beyond that, and i didn't want to pay for new drivers.

So what happens once you turn it up too much:
- First you 'll have rolling of of the peaks (bass), but no real audible distortion.
- Then your overall volume flattens off and you'll start to hear distortion in the bass.
- If you then push it further, you'll probably start to hear the voice coil hitting the magnet etc ... --> Destroying your speaker.

Get into your ca
 
(oops, slipped my fingers!)

So get into your car and test this *gently*. You'll get a much better idea of what you'll get. You can also do this with any single full range driver you have around the house. (TV, portable radio, ...)
(I once pushed my Sennheiser HD25-1 till the compression level for about 5 seconds. Very low distortion at that level and VERY impressive!)

Oh, one thing: this is all for sealed enclosures. If you use ported enclosures, the cone movement won't be dampened by the compressed air inside, so you'll get till Xmax at less SPL/power levels, especially with lower frequency's!

About your choice of rivers, I'd go for the one with the highest BL. To get decent high freq with such a large cone, you need a stronger motor for more control. The Visaton also doesn't go so high.
IHMO it's easier to add more lowfill later with a subwoofer, than to add highfill with crossover and tweeters. :scratch:
 
Oh, one thing: this is all for sealed enclosures. If you use ported enclosures, the cone movement won't be dampened by the compressed air inside, so you'll get till Xmax at less SPL/power levels, especially with lower frequency's!

Oh stop it! Vented enclosure REDUCE excursion at and near the resonant frequency. Above resonance, the exursion will not be any greater than a sealed box of the same volume. Below resonance unloading will occur and yes excursion will be uncontrolled.


Here's my suggestion. If you get those full rangers and spend most of your money on them then go really really cheap a seperate sub(cross over below 150hz) or some woofers to put beneath your full rangers(cross over at 200-300hz)
 
BassAwdyO said:


Oh stop it! Vented enclosure REDUCE excursion at and near the resonant frequency. Above resonance, the exursion will not be any greater than a sealed box of the same volume. Below resonance unloading will occur and yes excursion will be uncontrolled.

I checked it again: *above* -3dB of the sealed enclosure, the excursion is indeed the same in vented and closed. *at* res freq the excursion is greatly reduced, and off course under -3dB of Vented it shoots up. *Between* res freq and 'sealed rolloff freq', excursion is slightly higher, which is what I meant. Sorry if I wasn't clear on that. :eek:

Anyway, Fullrangers don't go that low, so with BR there's a real danger of overexcursion imho. Definately try to go as low as you can, and then use a sub.
 
Between it is slightly higher? Doing graphs on WinISD I dont see this... It must be a very small difference.

I wouldnt suggest porting them either really. I try to stay away from porting in the audible range because of the resultant group delay. Tuning those speakers below 20hz wouldnt do any good.
 

jondoe

Member
2004-10-08 8:06 am
Well, basically, here's how things stand.
1" i buy now the fullranges (i kinda prefer the Paudio over the Visaton) and make a small close box (10-20L) for them, buy 2 woofers (mounted in whatever enclosure is optimum) and cross them at 200-300 Hz.
2" i buy now the fullranges and later the woofers. The crossing should be at about the same freq.

Option 2" is the one best for me (financial restraints).
So now things are:
a) i make a huge box (i have plans for horns and TL for both fullranges)
so that i have some bass, even if i play at most 20W.
b) i make small boxes win no bass whatsoever and live with it for the following year.:bawling:

Now, if i do a) i'll have 2 huge boxes in excess when i build my woofs and that is not very nice, unless...
Unless the woofs are interchangeable with the fullranges (T/S wise) so i mount them in these big enclosures and move the fullranges in they're own, new, small boxes.

Hmmm, this sounds like an idea. I'll have a great deal of looking for the appropriate woof if i choose this path.
Or i may like how the fullranges sound on theyre own and don't add woofers (something says bad ideea, distortionwise).