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Old 5th January 2011, 08:59 PM   #21
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Guys, the article I linked to has a section on low frequency bass energy in different music.
The average bass energy (sub 40Hz) was 11.88dB down on stuff above 40Hz. There's a chart of some different music there, feel free to take a look.

Kipman, we've established the need for an infrasonic filter, however, I'm not sure where this 11Hz has come from. The lowest I've ever heard of (certainly never experienced) is 16Hz, bottom of large pipe organs. The music composed for such frequencies is very rare, too, as so few organs have these pipes. Even after that, the buildings in which they're enclosed won't stand a loud 16Hz on a regular basis. So, how, pray tell, does 11Hz come about?

Chris
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Old 5th January 2011, 09:05 PM   #22
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Quote:
Originally Posted by chris661 View Post
So, how, pray tell, does 11Hz come about
Most likely from electronic instruments and digital processing I suppose.
A chip in a computer can generate 5Hz if needed.
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Old 6th January 2011, 11:40 AM   #23
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My response to post 8 has been removed.

The person responsible for post 8 has sent me a private message with similar drivel....

I am running a sytem with LTX, its a shame that i have to cut thru the crap of others, before i can give PRACTICAL advice on the implentation of this setup to people who are interested, not helped by people who MAY (they didnt say) have tried and failed / or were not happy with their results
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Old 6th January 2011, 12:03 PM   #24
AndrewT is online now AndrewT  Scotland
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Henry,
you have offered advice in posts 14 & 15.
I will not argue with that.
Your statements do not prevent other Members offering their advice, even when it appears contradictory.

I do not like the personal remarks you make about other Members.
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Old 6th January 2011, 05:04 PM   #25
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Henry, I currently (well, up until very recently, where I removed the amp's PSU) ran a LT circuit on a pair of 8" drivers in a 40 litre cabinet. There was around 14dB of gain to get the f3 down to 28Hz.

At low levels (up to comfortable listening, maybe 80-85dB in a small room), the subwoofer worked fine. Turn it up a little, excursion became visible, but it was still a passable performance. Remember, this is in a small room. Turned up, the drivers quickly hit the stops when any sub 40Hz bass came along. In larger rooms, the cone excursion to fill a room at normal listening levels got kind of silly. Almost a passable performance, but given anything sub 40Hz, there were loud mechanical noises.
Having lived with said subwoofer for nearly two years now, I know it's limits. It won't do movies without a high pass filter to stop the drivers bottoming out. This is not a low and rumbly subwoofer, it was reasonably tuneful, reasonably deep, with reasonable output. Fine for music in a small room, but at ~3mm Xmax per driver, distortion got out of hand when really turned up.
In conclusion, yes, you can get away with a (relatively) small driver and plenty of eq. But you must get used to the limits of the system. I wouldn't try to take an 8" past 40Hz without a specialist subwoofer driver with plenty of linear(!) Xmax, and sufficient amplifier headroom to get there.

Chris
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Old 6th January 2011, 05:19 PM   #26
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It should be easy to note that any two sealed subwoofers with same drivers will have to produce the same cone excursion to have same acoustic output, no matter the enclosure volume, in theory.

In practice the same driver in a smaller volume will require greater excursion at the coil to match acoustic output power because of increased cone flexure.

The problem is the reduced enclosure volume will have to achieve higher box pressure swing at that same cone excursion, leading to increased power requirements and increased motor and cone distortion.

For very small, high output boxes I'd recommend metallic cones, straight conical or dome. Exponential or some kind of curved paper would seem to be a fairly high distortion no no.

Last edited by Andrew Eckhardt; 6th January 2011 at 05:25 PM.
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Old 6th January 2011, 05:59 PM   #27
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by kipman725 View Post
no Andrew is correct I can think of many tracks where the greatest amplitude signals are <50Hz
I can also think of a few where the greatest amplitude signals are <20Hz necessitating the need
for high pass filters on most systems or some kind of dynamic limiting. A 11Hz fundamental signal
going though 12dB of gain from a circuit similar to a LT is not pretty in terms of cone excursion
(cone slams into mechanical limits).
Hi,

No. The principle applied is wrong and always will be be.
Of course low bass can have high signal levels, inevitable.

What can happen and what actually does is very different.

A theory based on what can happen, disregarding what must
and actually does happen, is rigorous but not IMO practical.

rgds, sreten.

With an LT you can trade smaller speaker size against more driving power. In the end
max driver SPL at any frequency does not change, only the power needed for max SPL.
If you don't understand the issues don't comment on them, e.g. +12dB is "bad".
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Last edited by sreten; 6th January 2011 at 06:10 PM.
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Old 6th January 2011, 06:21 PM   #28
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Originally Posted by kipman725 View Post
no Andrew is correct I can think of many tracks where the greatest amplitude signals are <50Hz I can also think of a few where the greatest amplitude signals are <20Hz

Please list some tracks you refer to.
If possible list tracks of different genre.

Last edited by Henry8; 6th January 2011 at 06:23 PM.
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Old 6th January 2011, 06:24 PM   #29
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Hey sreten:

>In the end
max driver SPL at any frequency does not change, only the power needed for max SPL.

This is optimistic. In the end max SPL is reduced (by the time you exceed driver power handling) for highly compensated small boxes because of power compression effects, which arise in various amounts in every subcomponent of a loudspeaker. Everything that's good for bandwidth is bad for an optimized driver in this application too. You'd even want to avoid breakup rings, which only work because of flexure. A very strong, high mass cone is needed, which is also bad for efficiency. All these things and more end up placing a lower limit on the practicality of reducing box volume.

Last edited by Andrew Eckhardt; 6th January 2011 at 06:27 PM.
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Old 6th January 2011, 06:35 PM   #30
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Andrew Eckhardt View Post
Hey sreten:

>In the end
max driver SPL at any frequency does not change, only the power needed for max SPL.

This is optimistic. In the end max SPL is reduced (by the time you exceed driver power handling) for highly compensated small boxes because of power compression effects, which arise in various amounts in every subcomponent of a loudspeaker. Everything that's good for bandwidth is bad for an optimized driver in this application. You'd even want to avoid breakup rings, which only work because of flexure. A very strong, high mass cone is needed, which is also bad for efficiency. All these things and more end up placing a lower limit on the practicality of reducing box volume.
Hi,

Its a further detail that does not change the basic principle.
If you have the power to spare, making a box smaller increases
power handling, due to the poorer bass response needing more
power to reach excursion limits, and its this trade off that does
effectively define most commercial subwoofers that use EQ.

The practicality depends on the perceived efficacy of smaller boxes.
Of course "bigger is always better" for bass, but not always practical.

rgds, sreten.
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