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Old 24th March 2006, 10:26 AM   #1
m@ is offline m@  Thailand
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Default Bandpass Woofer/Midrange?

I've been playing around with dipoles, full rangers, and tri-amped systems, but have recently been researching more conventional closed box, passive two and three way systems.

I've been wondering what people have experienced using bandpass loaded (sub)woofers, esp from around 100 to 20. For the lowest octaves, it seems ideal as it could eliminate the more complex and expensive part of a crossover network. In my sims, it also reduces overall volume by 25% or more, while maintaining an optimal alignment.

I've also read that they have better transient response than a standard BR when tuned properly.

I guess this is technically a subwoofer, but i'm talking about integrating it into a floorstander with a forward firing port.

Most complaints I've found were about 'boomy, one note bass.' But most complaints about BR cabinets are the same - and i've heard plenty of good speakers with BR loading.

And does anyone know how a bandpass enclosure actually works? I've read 'acoustic cancellation' on a couple of sites, but I'm not sure what that's supposed to mean. Do they mean the high frequencies are coming through the cone and cancelling? That doesn't seem accurate to me. Doesn't it just mean that you're containing the front wave (as well as AS loading the cone) and you get the normal BR thing going on in the port side?

Also, has anyone every heard of a mid or midbass that was bandpass loaded?

Any experience/opinions on this?
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Old 24th March 2006, 11:57 AM   #2
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I have never seen a midrange in a band pass I would think they would wreck the imaging. PA systems could use it for effiecieny but I think horns are far more common.

If you model it: For efficiency they will have 1 note but you can build them for more bandwidth giving up efficieny and probably having 2 humps.
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Old 24th March 2006, 12:20 PM   #3
sreten is offline sreten  United Kingdom
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in hifi something is only rarely new.

In a typical bandpass the lowest frequencies use sealed box loading,
hence "better than reflex transient response". By enclosing the front
of the driver and adding a port you get a 2nd order low pass function.

This does save on crossover components for an add on subwoofer.

The add on AB1 sub for the LS3/5a is a good example of a stand/sub.

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Old 24th March 2006, 05:15 PM   #4
infinia is offline infinia  United States
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Bandpass designs are good for maybe an octave range at best. Sort of a double tuned BR design. Efficiency is good as the pass bandwidth is narrowed. Suffers from max SPL as all the air has to be moved through the ports. Used as subs are not good for people that are looking for so called "bass slam" effect.
like four million tons of hydrogen exploding on the sun
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Old 24th March 2006, 05:52 PM   #5
RJ is offline RJ  United States
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I experimented with bandpass subs. Only the bass drums sounded any good. Other bass instruments didn't.
It did get me to research bass drums on other enclosures. Well, it's not the box but the drivers. Turns out the low Le (voice coil inductance) drivers were the key in obtaing good clean & fast bass.
Enclosures were then matched to the driver.

Also, the slope in simulation programs don't match real world frequency response. You don't get a 24 db slope front or back, especially the back portion. The back slope also has a secondary resonance that has to be mitigated with a crossover, You can kill some of the midrange and tame that resonance with stuffing, but I found a plate amp was the best. The midrange coming through the port sounds really hollow, as if the band is playing in a cave.
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Old 25th March 2006, 02:10 AM   #6
GM is online now GM  United States
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The LS 5/8 BBC monitor's midrange is technically BP loaded, albeit very modestly:

Of course all compression midrange horns are BP loaded.

Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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