Objectively support for overhang for bandpass subs? - diyAudio
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Old 11th November 2012, 07:12 PM   #1
Omholt is offline Omholt  Norway
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Default Objectively support for overhang for bandpass subs?

I have seen many commenting that bandpass subs give a typical one note bass and has audible overhang. Are there any objective studies that show this for even a good bandpass sub or is this simply based on results of poor designs?
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Old 11th November 2012, 10:04 PM   #2
Moonfly is offline Moonfly  Spain
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Couple links for you that might be worth a read:

Dan McGrath's Subwoofer Project

What's smaller than a fridge and bigger than a washing machine?
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Old 12th November 2012, 01:16 PM   #3
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I doubt very much, that one can hear "hangover" as an isolated
property of a subwoofer in an acoustical small room.

What we hear as "hangover" or "one note bass" is usually a bad
matching between the woofer and the room.

Take two 2nd order systems as an example:

If you have a closed box with say fs=40Hz and Qtc=1, that box might
sound "having a hangover", "being bass heavy" or even "like one note bass"
if the room is rather small and the box resonance is well within the range of
room pressurization.

Same with the speaker exciting a room resonance around 40 Hz, which might
also be a higher order resonance in a bigger room.

An open baffle speaker with fs=40Hz and Qtc=1 might not sound
that "heavy", if the driver's Qts is chosen to compensate
for the falling response of the dipole towards lower frequencies.

However in both cases the excitation of room modes play an important role.

The "ringing" of both systems in free field will be quite the same,
but the audible effect in a given room can be different, also
the measured inroom response at the listening seat.

As long as the Q of a subwoofer is well below typical Q(s) of room modes,
we neither can really audibly estimate the Q of the subwoofer itself,
nor can we estimate the order of the subwoofer system
(e.g. whether it is a closed box or bandpass).

You can implement a bandpass having a more balanced freauency response
than a (high Q) CB even under freefield conditions.

Most important is how the subwoofer interfaces with the room, due to its
own FR and its position in the room.

That is the major issue, the tendency of prolonged ringing with rising order
of subwoofer systems is a minor issue, as long as you keep it within sane limits.

Nevertheless in a real room balanced steady state response at the listening
seat and high values of the modulation transfer function are not the same goal.

Dipoles positioned to predominantly excite the longest axis of the room are quite
good in modulation transfer, but balanced frequency response can still be a problem.

Things get more relaxed if you go for excitation of the room at multiple
positions and EQ of the system.
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Last edited by LineArray; 12th November 2012 at 01:39 PM.
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Old 12th November 2012, 04:51 PM   #4
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Quote:
Originally Posted by LineArray View Post
I doubt very much, that one can hear "hangover" as an isolated property of a subwoofer in an acoustical small room.
I built an interesting bandpass sub designed by Phillip Graham (dubbed the Resopump) using an Eminence HL10c .
After a few cabinet revisions, the output closely conformed with his simulations.
Very smooth response through the bandpass, and very high sensitivity.

However, it just sounded bad, "hangover", poor definition of bass lines, floppy kick, etc.
It did not matter whether outdoors, or indoors in an acoustical small room, when compared to other Eminence loaded ported cabinets EQed to a similar response, they sounded fine, the Resopump did not.

There may be a good sounding band pass sub design, but so far, I have not heard one, and have been hearing them since around 1990.

Art
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Old 12th November 2012, 05:06 PM   #5
tb46 is offline tb46  United States
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Location: Texas
Hi Omholt,

My personal experience is only with 4th order bandpass subs, and it is very positive. It takes a little work to properly integrate the sub, the other speakers and the room (which holds true for any other sub too.) Overhang was not a problem.

I would recommend you experiment on your own, and find out if this approach works for you.

Also, gedlee (Earl Geddes) seems to like them: Subs.

Regards,
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Old 12th November 2012, 05:44 PM   #6
Omholt is offline Omholt  Norway
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Quote:
Originally Posted by weltersys View Post
I built an interesting bandpass sub designed by Phillip Graham (dubbed the Resopump) using an Eminence HL10c .
After a few cabinet revisions, the output closely conformed with his simulations.
Very smooth response through the bandpass, and very high sensitivity.

However, it just sounded bad, "hangover", poor definition of bass lines, floppy kick, etc.
It did not matter whether outdoors, or indoors in an acoustical small room, when compared to other Eminence loaded ported cabinets EQed to a similar response, they sounded fine, the Resopump did not.

There may be a good sounding band pass sub design, but so far, I have not heard one, and have been hearing them since around 1990.

Art
I wonder why you have experienced this.
Did it cover too wide of an area? From what I understand one will experience ripple if the bandwidth is too broad.

Bandpass subs seem more difficult to build correctly, so I can understand that something may go wrong for people. Other then that and room related issues, it's difficult to see why there should be an overhang.
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