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Old 18th January 2010, 04:55 PM   #1
freddi is offline freddi  United States
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Default bandpass vs TH vs reflex vs sealed as musical foundation?

how are well designed bandpass boxes considered to sound versus other type? - I've only built two BP - neither as good as they could have been - one an overly large BP4 with 12" and other a BP6A with dvc 10. The BP4 sounded pretty good and BP6A decent. For an already built unit I'm looking at Geddes new 12" sub which appears to have distributed front chamber vents.
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Old 22nd January 2010, 10:38 PM   #2
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Roughly speaking, the more complicated the box, the worse the time response.

For example, a sealed box will have the cleanest time response. A ported box will "ring" more. A bandpass will ring even more. Horns, it depends a lot on the construction.

On the other hand, the more complicated boxes can get more low frequency SPL per watt, and more maximum SPL for a given distortion level.

You can find a lot of debate of sealed versus ported, but generally everyone will agree bandpass boxes are all about SPL not great sound (Dr. Amar Bose's marketing department notwithstanding).

As for the Geddes design, Earl is always fascinated by efficient design. I couldn't comment about his personal sonic taste. Which sub exactly do you refer to?

P.S. Why not just ask him directly how the sound quality is versus other designs?
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Old 23rd January 2010, 07:44 AM   #3
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Originally Posted by freddi View Post
how are well designed bandpass boxes considered to sound versus other type? - I've only built two BP - neither as good as they could have been - one an overly large BP4 with 12" and other a BP6A with dvc 10. The BP4 sounded pretty good and BP6A decent. For an already built unit I'm looking at Geddes new 12" sub which appears to have distributed front chamber vents.
I have little experience with BP except for some cheap PA subs, so not much to add.

Ported, or PR can be excellent if you design them well and choose a good driver.

Sealed is even easier to design and build, but less LF typically, but a shallower roll off that may gel better with any room gain.

TH's tend to be big, but are efficient within their passband, especially if you want HT depth bass. For 40Hz they are much smaller.

Power is cheap, great drivers like the Maelstroms are very inexpensive for what they offer so sealed and EQ'd appeals to me most with conventional systems. If I were in the US the AE AV15 + PR's + box kit they have going would be very appealing too.

Personally I am torn between building some of these because I have the drivers (though they are huge) or getting another Maelstrom 18 or two and going sealed and EQ'd with the big Quest amps I have here.

I think more than anything it comes down to what you want/need and how it will work with what you have, your room, desired SPL etc. I want a combined music/HT system that does it all, whereas my friend Terry is 2ch only and his Frank's do a measured 35Hz flat, sound spectacularly good and go damn loud without strain.
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Old 23rd January 2010, 01:26 PM   #4
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Quote:
Originally posted by freddi
how are well designed bandpass boxes considered to sound versus other type?
I had a JBL SB-5 way back when it first appeared. Was quite disappointing. Bought a few more other brands, results were equally unsatisfactory. That left me with a negative impression of bandpass.

Recently, I decided to build a bandpass just to find out how well it fares against sealed and vented boxes. The result was stunning. Its exactly what I'm after. Very good definition.

I thought perhaps it was by chance. Designed another bandpass using a different driver. This is a 10" long throw woofer that I've tested extensively but have never been able to get satisfactory results in a vented or sealed box. Result was even better than the first.

I'm now convinced that bandpass is superior. The trouble is, its difficult to get it right. Bandpass is very sensitive. T/S must be accurate. Otherwise, box tuning will be far off. The wonderful part with bandpass is you don't need expensive drivers to get good performance.
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Old 24th January 2010, 12:37 PM   #5
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As far as sealed vs ported go, I'd go for sealed every time.

For ported, the excursion above port tuning is high as well. If you try to tuned low (~20Hz), you'll hit excursion limits quickly at 40Hz, where the bass drum and bass guitar lie.

Sealed has no such problems. They also, to me, sound deeper, possibly down to the shallower roll-off, which integrates better with room gain.

I've heard cheap bandpass designs, but never been that impressed - they always sound odd. This could be down to poor integration with other speakers (gap in frequency response), or for other reasons.
I know they can go pretty loud, but only in their specific frequencies. Go outside this, and you'll get little sound for lots of excursion.
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Old 24th January 2010, 05:31 PM   #6
freddi is offline freddi  United States
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when I played with 170 liter (way too large) BP4 for a nondescript Eclipse 12" with only 6mm xmax.
the top speakers were AR M1 which rolled on naturally where the bandpass box rolled off -
upper bass due to the little 6.5" woofer was dynamically weak but overall tautness was much better than my Khorns.

A capacitor (and sometimes inductor) can be added into sealed rear chamber bandpass design to manipulate things.
Bass seemed omni sounding probably due to the small size source (only a 4" port on the BP4)

if a bandpass sub's top end overlaps or underlaps the mains too much - will that smear the sound? or does this not matter in practice in real rooms?

there have been patents to create additional mechanical filters on the front chamber.
midrange port leakage can create an additional spatial source.

what are good choices for bandpass sub drivers for home use these days?

Last edited by freddi; 24th January 2010 at 05:34 PM.
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Old 24th January 2010, 05:43 PM   #7
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Originally Posted by Michael Chua View Post
...Recently, I decided to build a bandpass just to find out how well it fares against sealed and vented boxes. The result was stunning. Its exactly what I'm after. Very good definition.

I thought perhaps it was by chance. Designed another bandpass using a different driver. This is a 10" long throw woofer that I've tested extensively but have never been able to get satisfactory results in a vented or sealed box. Result was even better than the first.

I'm now convinced that bandpass is superior. The trouble is, its difficult to get it right. Bandpass is very sensitive. T/S must be accurate. Otherwise, box tuning will be far off. The wonderful part with bandpass is you don't need expensive drivers to get good performance.
I think "superior" is a misnomer. It's all about tradeoffs. In your situation, you're probably enjoying higher SPL with less distortion. Another listener, with different ears/brain, might find a lot of fault with the transient performance. What kind of music you play can also make a difference-Motorhead doesn't sound too clean in the first place versus say Stanley Clarke bass solos.

And you're right, bandpass is very sensitive to the box design and somewhat less sensitive to the driver. Basically the bandpass is-on purpose-a highly resonant system, so any driver will excite the resonance to some degree.
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Old 24th January 2010, 06:38 PM   #8
freddi is offline freddi  United States
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hi head unit - will the bandpass sub unconditionally smear the transients of bowed bass viola, etc. creating a drone sound rather than good tracking of the signal? I don't have enough experience with BP to know.
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Old 25th January 2010, 06:23 AM   #9
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Well, everything in speaker building can have exceptions, but yeah, that's the general idea.

What to some may sound really powerful and great can sound to others like boomy mush. It's a matter of hearing and taste and the music being listened to.

One exception might be small drivers-if you're trying to use a 6" as a sub, it will fail miserably in a sealed box. But in the right bandpass, it might sound much "improved" simply because there would be much more bass with less distortion. The sound might not be as "pure," but if the sealed box just kinda sucked in the first place the bandpass would sound "better."
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Old 26th January 2010, 12:47 AM   #10
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Having just built a pair of bandpass subs, I'd have to say that they have the potential to sound very good. In my case, having two subs with good placement, levels and a bit of EQ to knock down the remaining peaks in the response, I hear very musical bass. They go quite deep and are capable of playing very loud as well. On the other hand, these are my first subs (apart from the small computer speaker kind), so I can't really comment on the relative virtues/vices of sealed vs ported from first hand experience. One of the reasons I went for bandpass, however, was that they are reputed to combine the responsiveness of sealed alignments with high output and low distortion. In my case, this seems to be the case although I would agree that careful design and measuring is needed. The drivers in mine are the same as the ones Earl G. uses (in fact I got them from him when I bought my Abbey kits). I wouldn't be surprised at all if his sound even better than mine.

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