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Old 18th July 2013, 08:59 PM   #1
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Default Why bandpass enclosure?

This forum is full of audio guys that have been doing this for many years and I in no way can stack up to them in experience or knowledge. I wanted to register to this specifically so I can learn from some very intelligent people.

Well occasionally I have some dumb questions and don't feel like signing up to some other forum where my questions will be considered acceptable so here I go.

I've done some reading and research and cannot find anywhere why exactly do people bother with bandpass enclosures? I can't seem to find any reason they are better than a normal sealed, ported or even infinite baffle setup. All I find is alot of problems and complications with this design.

1. Bandpass subwoofer enclosure increase your chance of blowing the woofer.
2. Bandpass enclosures from what I can tell are not louder or better sounding (SQ)
3. They are extremely complicated to build and are not forgiving for even the smallest mistakes.
4. the boxes are huge so space is not saved like in a IB setup.
5. some have many ports which I assume adds to the port noise, and a bandpass enclosure tuned to a particular frequency from what I learned will not put out much more at that frequency than a ported enclosure tuned to same frequency.

I understand you can build a bandpass where the sound is played from both ends of the woofer, so you get more output. but the same thing is achieved with a ported box

So what gives, is there some factor I am missing here or are they just built for the hell of it, "because I can" type of thing?
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Old 18th July 2013, 09:21 PM   #2
Scott L is offline Scott L  United States
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Default OK Let me chime in first

Greetings and Welcome to the forum.

I've been building speakers for 41 years and have never considered a band-pass for anything. That doesn't necessarily make them bad, I just have never had any interest. Other memebers here may have, and might like to post their results.

I am a bit puzzled by your post. You state you can't see any advantge to a band-pass, so why are you even dwelling on it ?
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Old 18th July 2013, 10:24 PM   #3
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Quote:
Originally Posted by Scott L View Post
Greetings and Welcome to the forum.

I've been building speakers for 41 years and have never considered a band-pass for anything. That doesn't necessarily make them bad, I just have never had any interest. Other memebers here may have, and might like to post their results.

I am a bit puzzled by your post. You state you can't see any advantge to a band-pass, so why are you even dwelling on it ?
Thank you for the reply,

I don't know what you mean by dwelling on it, I'm simply learning. I guess I'm a information ninja!

I was just seeing if there is something else I am missing or haven't learned yet that would make a bandpass enclosure make sense, I guess a good follow up question is; in what scenario is a bandpass enclosure practical if any?
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Old 18th July 2013, 10:57 PM   #4
kevinkr is offline kevinkr  United States
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Actually IMHO there is nothing stupid at all about this question as I ponder it. Perhaps the thread ought to be renamed as I think it will get a lot more attention if you pose the question directly in the title. I can change it for you, just let me know by PM.

Edit: Thread title updated after PM request. I am quite curious to hear the answers myself.
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Old 19th July 2013, 12:02 AM   #5
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Quote:
Originally Posted by Aleksrussian View Post

1. Bandpass subwoofer enclosure increase your chance of blowing the woofer.
2. Bandpass enclosures from what I can tell are not louder or better sounding (SQ)
3. They are extremely complicated to build and are not forgiving for even the smallest mistakes.
4. the boxes are huge so space is not saved like in a IB setup.
5. some have many ports which I assume adds to the port noise, and a bandpass enclosure tuned to a particular frequency from what I learned will not put out much more at that frequency than a ported enclosure tuned to same frequency.
You can read here.

JL Audio header Support Tutorials Tutorial: Bandpass Enclosure Characteristics
Steinigke Blog (english) Overview on subwoofer types
Patent US1969704 - ACOUSTIC DEVICE - Google Patents
Attached Images
File Type: jpg bandpass.jpg (65.8 KB, 166 views)
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Last edited by Inductor; 19th July 2013 at 12:15 AM. Reason: Patent US1969704
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Old 19th July 2013, 12:06 AM   #6
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I've actually read that, still didn't see any significant improvement in any department.

What have the people that have built a bandpass box used it for on this forum?

Edit: der... That's a similar but slightly different article, reading through now

Last edited by Aleksrussian; 19th July 2013 at 12:10 AM.
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Old 19th July 2013, 12:15 AM   #7
Ron E is offline Ron E  United States
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Quote:
Originally Posted by Aleksrussian View Post
...why exactly do people bother with bandpass enclosures? I can't seem to find any reason they are better than a normal sealed, ported or even infinite baffle setup. All I find is alot of problems and complications with this design.

1. Bandpass subwoofer enclosure increase your chance of blowing the woofer.
2. Bandpass enclosures from what I can tell are not louder or better sounding
3. They are extremely complicated to build and are not forgiving for even the smallest mistakes.
4. the boxes are huge so space is not saved like in a IB setup.
5. some have many ports which I assume adds to the port noise, and a bandpass enclosure tuned to a particular frequency from what I learned will not put out much more at that frequency than a ported enclosure tuned to same frequency.
1. Depends on implementation
2. Depends on implementation
3. More complicated than sealed or vented, but not extremely so.
4. Depends on implementation
5. Depends on implementation

Think of it as degrees of freedom. For a given woofer, a sealed box has one (box size), a ported has two (Size and tuning), a 4th order bandpass has three (sealed and vented volumes and tuning) and a 6th order bandpass has 4 (2 volumes and 2 tunings). More degrees of freedom means more chance to shape the response to your liking. Their inherent lowpass characteristic makes them most useful as subs.

Bandpass enclosures can be designed with more or less sensitivity than the woofer, with narrow or wide (not more than ~1.5-2 octaves though) bandwidth. The filter of the port can reduce distortion (and perhaps lead to more stress on the woofer). Box sizes are typically on par with a vented box for similar sensitivity and similar F3, but with a slower rolloff (in the case of 4th order).

Premade bandpass boxes give them a bad name - some very high end speakers (KEF to name one) have used bandpass enclosures.
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Old 19th July 2013, 12:24 AM   #8
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Quote:
Originally Posted by Ron E View Post
1. Depends on implementation
2. Depends on implementation
3. More complicated than sealed or vented, but not extremely so.
4. Depends on implementation
5. Depends on implementation

Think of it as degrees of freedom. For a given woofer, a sealed box has one (box size), a ported has two (Size and tuning), a 4th order bandpass has three (sealed and vented volumes and tuning) and a 6th order bandpass has 4 (2 volumes and 2 tunings). More degrees of freedom means more chance to shape the response to your liking. Their inherent lowpass characteristic makes them most useful as subs.

Bandpass enclosures can be designed with more or less sensitivity than the woofer, with narrow or wide (not more than ~1.5-2 octaves though) bandwidth. The filter of the port can reduce distortion (and perhaps lead to more stress on the woofer). Box sizes are typically on par with a vented box for similar sensitivity and similar F3, but with a slower rolloff (in the case of 4th order).

Premade bandpass boxes give them a bad name - some very high end speakers (KEF to name one) have used bandpass enclosures.
Okay thank you, that cleared up some of it.

I guess if you have a problem with a particular frequency you could use a bandpass to work that out?

I guess my confusion was stemmed in, why would some one build a bandpass that increases the volume of let's say the 30hz area, when they can use some type of eq to get that to their liking without all the trouble of a bandpass.

Or use a ported box tuned to the same frequency.

I guess it's really a toy that is more useful to people that build stuff to experiment than something used in a practical application?

I suppose the KEF engineers put in a ton of time into designing it to sound right, I doubt they were able to design a speaker that is better in some single way than other high quality speakers designed with a different approach.
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Old 19th July 2013, 12:28 AM   #9
OscarS is offline OscarS  United States
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Quote:
Originally Posted by Ron E View Post
1. Depends on implementation
2. Depends on implementation
3. More complicated than sealed or vented, but not extremely so.
4. Depends on implementation
5. Depends on implementation

Think of it as degrees of freedom. For a given woofer, a sealed box has one (box size), a ported has two (Size and tuning), a 4th order bandpass has three (sealed and vented volumes and tuning) and a 6th order bandpass has 4 (2 volumes and 2 tunings). More degrees of freedom means more chance to shape the response to your liking. Their inherent lowpass characteristic makes them most useful as subs.

Bandpass enclosures can be designed with more or less sensitivity than the woofer, with narrow or wide (not more than ~1.5-2 octaves though) bandwidth. The filter of the port can reduce distortion (and perhaps lead to more stress on the woofer). Box sizes are typically on par with a vented box for similar sensitivity and similar F3, but with a slower rolloff (in the case of 4th order).

Premade bandpass boxes give them a bad name - some very high end speakers (KEF to name one) have used bandpass enclosures.
I competely agree. I've built bandpasses before. More complicated? Hardly. Time consuming yes, but not complicated IF you take necessary precautions first so you don't make rookie mistakes. If you make mistakes, you're a rookie.

If one can successfuly design AND properly implement (meaning verify with measurements) sealed and vented bass-reflex enclosures, designing and properly implementing a bandpass is not all that different.

Aleksrussion, which books do you currently own that go over the topics of designing sealed/bass-reflex loudspeaker enclosures?

Last edited by OscarS; 19th July 2013 at 12:33 AM.
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Old 19th July 2013, 12:29 AM   #10
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Originally Posted by OscarS View Post
I competely agree. I've built bandpasses before. More complicated? Hardly. Time consuming yes, but not complicated IF you take necessary precautions first so you don't make rookie mistakes. If you make mistakes, you're a rookie.
What was your application? How come you chose the bandpass over the other options?
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