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Old 7th April 2003, 06:34 AM   #1
OMNIFEX is offline OMNIFEX  Jamaica
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Default High Xmax is Great But.................

I've noticed there's been a trend going on. Everyone
wants a High Xmax woofer.

Thats fine, and, all providing you have the power
to use it to its full potential.

But, if your using these high Xmax woofers
with low power, why bother?

The higher the Xmax, the lower the efficiency. So,
are we really making a wise choice going for these
larger than life Xmax drivers, when we don't have
the power to drive them to their full capacity?

What are your thoughts..................
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Old 7th April 2003, 07:01 AM   #2
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Xmax is cool. everyone like watching subs move... (and if they do so linearly everyone is happy)

but yeah, i guess i see your point.
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Old 7th April 2003, 07:42 AM   #3
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I do not believe that extremely high excursion woofers are necessary at all......

Theres an interesting post going on at the diysubwoofers.org discussion forum at the moment regarding high excursion woofers, see:

http://www.diysubwoofers.org/talksho...ages/30880.htm and
http://www.diysubwoofers.org/talksho...ages/30882.htm for the main argument.

Adrian
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Old 7th April 2003, 08:40 AM   #4
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Xmax is just but one parameter, one has to consider all the parameters when picking out a suitable driver (for your needs).

Both xmax and efficiency can be high. It just so happens that a majority of off-the-shelf high excursion drivers were designed for very small enclosures -- making them inefficient (or power hangry).

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Old 7th April 2003, 09:05 AM   #5
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Quote:
But, if your using these high Xmax woofers
with low power, why bother?
Depends watt power level you call low? (excuse the pun :-)

A Shiva (moderate xmax?) will reach excursion in a 5^3 ft box tuned to 22Hz @ about 32Hz with *only* 250 watts.

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Old 7th April 2003, 09:27 AM   #6
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F4ier is absolutely right.
It is not the high x-max that makes a woofer ineffective. If you keep the BL product the same by using a larger magnet then the efficiency stays the same.
It is just because people want small sexy subwoofers which go low - that those special subwoofer drivers (with low Vas) were introduced which offer high excursion at the cost of efficiency.

There is also a trend of introducing program material with more low-frequency content than before.

Nowadays even P.A. speakers are going lower at the cost of efficiency and it isn't a bad thing at all. At least I don't want ghetto-blaster bass at a live concert; i.e. such with a lot of punch at 100 Hz but nothing below 50 Hz. Apart from that: high-power amplifiers are simply using much less truckspace than high-efficiency speakers.

Regards

Charles
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Old 7th April 2003, 11:44 AM   #7
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The way I see it, high Xmax is just a symptom of poor cone-to-air coupling that probably a horn deals with best. But... just as in the same vein as grossly inefficient things like king size heatsinks and flames licking out the exhaust pipes, everybody loves to see a big sub doing it's stuff.
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Old 7th April 2003, 01:58 PM   #8
OMNIFEX is offline OMNIFEX  Jamaica
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Quote:
Originally posted by f4ier


Both xmax and efficiency can be high. It just so happens that a majority of off-the-shelf high excursion drivers were designed for very small enclosures -- making them inefficient (or power hangry).


Please show me a high xmax speaker (over 15 mm) with a
high efficiency. I haven't found any.

Quote:
Originally posted by Dave Bullet


Depends watt power level you call low? (excuse the pun :-)

A Shiva (moderate xmax?) will reach excursion in a 5^3 ft box tuned to 22Hz @ about 32Hz with *only* 250 watts.



Dave.
Please Explain. Are you saying that your driving the Shiva
at its full potential (Xmax linear) with as little 250 watts?

Quote:
Originally posted by phase_accurate
F4ier is absolutely right.
It is not the high x-max that makes a woofer ineffective. If you keep the BL product the same by using a larger magnet then the efficiency stays the same.


Regards

Charles

Are you sure about that? Oversized magnets are used
on plenty of woofers with high xmax, and, still have
low efficiency.
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Old 7th April 2003, 02:18 PM   #9
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Quote:
Are you sure about that? Oversized magnets are used
on plenty of woofers with high xmax, and, still have
low efficiency.

Many large x-max woofers are designed with subbass reproduction in mind. I.e. they are having low Vas and low fs in order to produce low frequencies in small cabinets.

Remember that efficiency is only proportional to BxL and proportional to Vas put it is also proportional to fs^3 !!!

So it is still impossible (and it will always stay that way forever !) to have a box that is at the same time - small, going low and having high efficiency.

So for P.A. works you usually design for economy, i.e. reasonably sized boxes that allow high SPLs at the cost of subbass performance.

Regards

Charles


/not caring too much about efficiency with his 90 dB/Watt 8" woofers having an x-max of +- 11 mm
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Old 7th April 2003, 02:27 PM   #10
OMNIFEX is offline OMNIFEX  Jamaica
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Quote:
Originally posted by phase_accurate



Many large x-max woofers are designed with subbass reproduction in mind. I.e. they are having low Vas and low fs in order to produce low frequencies in small cabinets.


I agree. However, using 4, 2, or 1 ohm dual Voice coils
are not giving you high efficency. Its just pulling more
wattage out of the amp.

Thats their trick of achieving High Efficency. Ever notice
that these enormous Xmax woofers are never designed
at 8 ohms?

There's a reason...............

There are plenty of people that would use these High
Xmax drivers for other use, than cars, but, can't with
these low impedance rating.

You mean to tell me this hasn't crossed any of these manufactures heads????
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