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Old 23rd May 2005, 06:25 AM   #1
jondoe is offline jondoe  Romania
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Default Effect of exceeding XMAX in real life

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 )
I await your input.
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Old 23rd May 2005, 07:17 AM   #2
soongsc is offline soongsc  Taiwan
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I had the same question in 1990. And I was asked to do my own tests.

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.
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Old 23rd May 2005, 07:37 AM   #3
simon5 is offline simon5  Canada
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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.
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Old 23rd May 2005, 08:06 AM   #4
jondoe is offline jondoe  Romania
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Quote:
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).
Quote:
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.
Quote:
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 ?
Quote:
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.
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Old 23rd May 2005, 08:37 AM   #5
joensd is offline joensd  Germany
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Hi,
have a look at Visatons "Solo" series:
http://www.visaton.de/english/uebersicht/6_89_u.html
http://www.visaton.de/vb/showthread.php?threadid=5234

greets
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Old 23rd May 2005, 08:38 AM   #6
simon5 is offline simon5  Canada
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You will hear it if you exceed Xmax, that's perfect so you can lower the volume before damaging something hehe!

If you want to go lower with alot of power handling, you can consider a ported box or a dual chamber ported box.

The easier solution is always to use less power hehe!
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Old 23rd May 2005, 09:04 AM   #7
jondoe is offline jondoe  Romania
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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, )
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Old 23rd May 2005, 09:26 AM   #8
soongsc is offline soongsc  Taiwan
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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 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.

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.
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Old 23rd May 2005, 10:54 PM   #9
Ron E is online now Ron E  United States
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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.
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Old 24th May 2005, 03:21 AM   #10
soongsc is offline soongsc  Taiwan
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I was just listening to an Organ recording CD WCD-806/8419 from Wilson Audiophile, The low end was so low that you can definitly see the cones move. It is very rare that they move that much. It sounds like lower than 40Hz, possibly closer to 25. These are reaching XMAX.
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