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Old 6th March 2007, 11:19 AM   #21
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There is no BEST principle IMO.
It has to be decided on a case-by-case basis which one of the two principles is better SUITED.

Just a remark: Yes - one can actually tune a reflex enclosure lower in order to achieve gentler rolloff characteristics but in this case the displacement-defined SPL improvement (over the closed box) above the tuning frequency can shrink to approximately 6dB.

I use both - boxes with and without "exhaust". The one with uses a 12" driver and has an f3 slightly below 50 hz. I know some posters here would call this whimpy but keep in mind that it does > 120 dB SPL long-term above 50 Hz.

Regards

Charles
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Old 6th March 2007, 11:57 AM   #22
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I guess the only thing you cannot do with a bass reflex is

a/ get rid of the time delay of aprox 1/24 second with the bass that comes out of the port,

b/ have a sub bass response that keeps up with the actual driver, lets face it there is only so much noise that will come out of a port or resonator,

Unless you actually play an instrument or go and see orchestra's/ jazz bands regularly, the level of realism is not that important.

P.S I have a ported 12" driver with a 3db down at 72hz. @97db watt/ meter. But such a smooth midrange!

I do have a 12" TL sub that works to 22hz. A very different shaped speaker cone though!
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Old 6th March 2007, 09:23 PM   #23
pjpoes is offline pjpoes  United States
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Cameron I think thats an unfair and subjective assessment of the ported box enclosure. Come on now, lets at least be realistic. I too will use each design where appropriate, but to argue that the only benefits of ported boxes is more bass output, and counter it with having slight slight time differences from the port as well as arguing incorrectly that all the sub bass comes from the port. That isn't correct, in the setup I mentioned, the woofer itself is going to be responsible for bass down to 25hz, the port just taking over at that point. I consider that sub bass, don't you?

I dont know if the talk about live music was a stab, but I'm a musician, I have posted my instruments on here before, I attend regular live concerts, be it jazz, classical, or rock. I know what live music sounds like, and frankly, I don't find much of it a very good reference. That isn't to say that some form of natural live music shouldn't be our refrence, but when you listen to a band in a bar, and everything is being reamplified through a crappy PA system, its hard to argue that you are hearing the true sound of a guitar or bass. Even most of the jazz clubs I have been to recently have had the horns, piano's, and basses going through PA systems, and frequently very poorly miced. We have one small jazz club that manages to stay away from that crap, and its a great reference, but man they are getting hard to find. I honostly don't think I would know what a guitar is supposed to sound like if I didn't play guitar myself, its very hard to hear someone playing their guitar either acoustic, or amplified only by the propper guitar amp, which has a very different sound from a PA system.
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Old 6th March 2007, 10:28 PM   #24
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Hi mastermosfet,

I'm surprised no-one has said you can have both in the same box - yup - that's right.

In my example - i have a dual ported / sealed subwoofer. My 12" driver has a mid Qts (approx 0.4).

I designed for a Qtc sealed of 0.5 (is supposed to be best transient response - although at the cost of power handling). I installed a port - tuned to approx 21Hz. The port has a sealing cap (believe me - it seals well and needs to).

I listed to the sub with normal rock, classical or jazz type music with cap on (sealed) and then cap off for drum and bass / movies (ported).

This gives me the best of both worlds - tighter / leaner bass for music, less driver demands for heavy bass music via a port.

Cheers,
David.
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Old 6th March 2007, 10:35 PM   #25
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Yep, I remember that project, Dave.

Glad to see it worked out so well for you..


As a general rule, as Novak pointed out in the 1950's, if you take a sealed box with a box QTC of 0.5 or thereabouts, and port it, you will have a pretty well tuned ported enclosure.

Most ported boxes are well planned out, by now. So it you just seal up the ports, you have a very workable sealed system.
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Old 7th March 2007, 01:44 AM   #26
Geoff H is offline Geoff H  Australia
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Quoting pjpoes "We have one small jazz club that manages to stay away from that ****, and its a great reference, but man they are getting hard to find. I honostly don't think I would know what a guitar is supposed to sound like if I didn't play guitar myself, its very hard to hear someone playing their guitar either acoustic, or amplified only by the propper guitar amp, which has a very different sound from a PA system."

Buskers in the street help. Even if they are out of step, off key, and nervous.

It used to be that drivers were designed with a particular cabinet in mind. With the availability of T&S specs, I think a lot of people assume they should go towards BR. T&S figures apply to sealed cabs as well. If size is not an issue I'd go for large sealed anyday, for it's transient and phase response. To me that's more relevant than a few dB at 30 Hz.
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Old 7th March 2007, 10:48 AM   #27
DAMIC is offline DAMIC  Seychelles
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Quote:
Originally posted by Dave Bullet
Hi mastermosfet,

I'm surprised no-one has said you can have both in the same box - yup - that's right.

In my example - i have a dual ported / sealed subwoofer. My 12" driver has a mid Qts (approx 0.4).

I designed for a Qtc sealed of 0.5 (is supposed to be best transient response - although at the cost of power handling). I installed a port - tuned to approx 21Hz. The port has a sealing cap (believe me - it seals well and needs to).

I listed to the sub with normal rock, classical or jazz type music with cap on (sealed) and then cap off for drum and bass / movies (ported).

This gives me the best of both worlds - tighter / leaner bass for music, less driver demands for heavy bass music via a port.

Cheers,
David.
Interesting concept. Can you describe what amount of stuffing is in the box. I assume that ported box use less stuffing that sealed one. So, what amount of stuffing is a compromise for both. Thanks in advance for reply.
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Old 7th March 2007, 10:56 AM   #28
forr is offline forr  France
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The dual sealed/ported concept used to be exploited by Marantz.
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Old 7th March 2007, 11:44 AM   #29
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Quote:
Originally posted by kelticwizard

Most ported boxes are well planned out, by now. So it you just seal up the ports, you have a very workable sealed system.
This can, in some cases, allow you to take a full range ported speaker and use them with a sub without a hi-pass filter. You only need to adjust the lo-pass filter point of the sub. I would do this with a set of bookshelf speakers when the main speakers were in renovation.
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Old 7th March 2007, 11:52 AM   #30
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Quote:
I dont know if the talk about live music was a stab,
umm no it was not.

What I love about DIY is that there are so many things one can try, and I have tried many different aspects and theories over the last 20 years and have enjoyed the ride.

Firstly boxes are not the ideal shape, 11 sided boxes are made by several hi end companies, wood is not the best material to make speakers out of (concrete would be better). Sealed boxes are not so efficent but generally have a nicer mid bass. ported has a more extended response, TL has both better midbass and bass extention but what a bitch to get right! and I personally love the sound of Altec horn loaded loudspeakers.

I am simply trying to point out the minor problems of bass refex designs. To many the small issues are non issues. Who cares if a double bass sounds a slight bit muddy unless one actually plays it? Classical music is mixed and mastered on different speakers than pop, Films are mastered differently yet again, different speakers and many more tracks.

With the buying public wanting the smallest box with the biggest bass, combined with lifestyle marketing, well thats whats in the shops. Here we can make anything, but lets not pretend that any is ideal, Simply the best and most practical for each application. Its more fun as a designer that way.

Quote:
I'm surprised no-one has said you can have both in the same box - yup - that's right.
mmm post 16

Easiest way would be to design a large bass reflex box, listen to the results, temporarily seal the port, boost the sub bass electronically, and then decide for yourself
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