Confused OB project

[SomekPoland]

Hi!
My friend wants to build his final speakers and wants it to be OB. He don't speak english, so I'm representing him right now. Room is around 23m^2, he wants to stick to around 1k Euro for now. I'm confused, because we can't find ready project for such build and I don't know speaker stuff good enough to design one, so I have to rely on you We were thinking about 3-way, 15 inch woofer(Eminence beta?), I don't know what for mids and top end. He can get Focal TBe in good price is it worth it?
Any links and feedback is appriciated

 

[Scott L]

Just please tell me why

Please tell me why on earth he would want to have an open baffle speaker.
I know this might sound critical at first, but believe me, it's not meant to be.
I really don't understand this cult-like following, So I am always curious as to why one would pursue such a compromised design. Thanks.

 

[SomekPoland]

He works at audio shop and claims, that he heard some great OB and met a guy who told him, that OB is fastest, easiest and most effective way to make good speakers. He also likes easiness and style of OB.

 

[Scott L]

A good place to start

So,

To answer your inquiry, here's what I feel is as good a place to start,
as any:



OBL11

 

[bzfcocon]

For OB, there is a question that is particularly important: will it be active - fully or partially - or passive ? DSP ? I would strongly recommend at least the bass to be DSP managed. It makes room integration much easier.

Another one - which you already seem to have an answer for - is woofer type: smaller, long stroke woofers a la Linkwitz or large ones - 15" and bigger ? How big can the baffle be ?

Related to above there is the question of how loud you will listen.

After that we can talk about particular Projects/design. Unfortunately there are not so many documented "ready to make " OB Projects out there.

Please tell me why on earth he would want to have an open baffle speaker.
I know this might sound critical at first, but believe me, it's not meant to be.
I really don't understand this cult-like following, So I am always curious as to why one would pursue such a compromised design. Thanks.

Every speaker design is a compromise in some way. OB is no exception and it does some things better, some other worse. You pick your compromises according to your goals and preferences. Not everyone wants high efficiency or SPL.

 

[dewardh]

I am always curious as to why one would pursue such a compromised design.

One pursues the superior design because, for some kinds of music (primarily "classical") and in some rooms (typically larger than the one described) they sound superior, and do a better job with existing two channel recordings of replicating the enveloping "concert hall experience". For an explanation of how and why:

Linkwitz Lab - Loudspeaker Design

 

[Scott L]

I'm very sorry, but I disagree

I disagree vehemently. A speaker system that fails to pressurize a room, and that adds a back-wave to make lousy recordings sound better, would, to me, be an INFERIOR design. Please understand, though, you all are OBVIOUSLY free to do as you please, but In my (allowed?) opinion, this is a cult-like-fad following.
I'm guessing part of the reason is, building a superior speaker enclosure is extremely difficult and time consuming. Not to mention expensive. Easier to cut a hole in a plank and call it a day.

 

[multitask]

have you listened to his speakers or even read thru its extensive documentation?
"fail to pressurize a room" i dont get what you are saying, name a single instrument that does that like a box speaker? even a bass drum is a dipole.
FWIW, i have not heared any speakers as realistic sounding as the lx521, often you cant even tell the speakers are there.

 

[bzfcocon]

...unless you're listening to electronic music or a reproduction of a rock concert coming out of amplified box speakers.

The room pressurizing argument is valid lower than the room's lowest mode. Above that OB does just fine.

 

[AllenB]

Disappearing isn't a product of the dipole, other types do it too. In this context dipoles incorporate the room earlier adding that to the direct sound. Unless you want to stretch the point and say the room reflections can help hide the speakers.

 

[bzfcocon]

Unless you want to stretch the point and say the room reflections can help hide the speakers.

In a certain sense, they do.

The disappearing trick is all about how convincing the (psychoacoustic) illusion of the reproduction of a real performance is. There are many factors to that and one of them is "spaciousness". David Griesinger studied it intensively for concert halls and came up with frequency-dependent reverberation times and levels, bottom line being that the right D/R ratio and reverberation distance are key for "spaciousness".

Now, that is something where dipoles _are_ different: more directional forward radiation, but at the same time increased reverberant field. This helps with the dissapearing trick.

 

[dewardh]

A speaker system that fails to pressurize a room

Why would one want to do that? Real instruments don't . . .

that adds a back-wave to make lousy recordings sound better, would, to me, be an INFERIOR design..

So . . . a uniform polar pattern that makes pretty much the whole existing catalog of classical recordings sound better is, to your way of thinking, INFERIOR design ? ? ? Did I get that right?

I'm guessing

Yes, obviously. But that's a **** poor way to design a "superior speaker enclosure", let alone build one. Understanding gets better results. And understanding acoustics, and the many disadvantages of "enclosure", will lead you eventually to dipoles . . .

 

[dewardh]

In this context dipoles incorporate the room earlier adding that to the direct sound.

Not so much "earlier" as more uniformly and advantageously. Small room acoustics dominate in, um, small rooms, and two unidirectional point sources have all the obvious (and some not so obvious) disadvantages when trying to establish a convincing "image". Dipoles present all the localization cues that are present in the recording in the first arrival (front wave) sound, while utilizing the room (primarily the front wall) to simulate the distributed sound sources in an actual concert hall. The result is simultaneous good localization with a more natural sense of spaciousness, envelopment and breadth of source. Dipoles can make the listening room sound significantly bigger than it is, sometimes almost to the point of disappearing.

On the other hand if Home Theater is your thing, and replicating the sound of your local Cineplex your acoustic goal, then dipoles would not be the first choice. But one would never mistake the sound of an orchestra as reproduced in a movie theater for the actual sound of an orchestra in a concert hall. "Reality" is not what movies are about, either visually or acoustically.

 

[AllenB]

The disappearing trick is all about how convincing the (psychoacoustic) illusion of the reproduction of a real performance is. There are many factors to that and one of them is "spaciousness".

Spaciousness in this context means early room involvement and that is not directly responsible for making a speaker disappear, though it still may. But this spaciousness is consistent between recordings and doesn't disappear.

Compare this to narrow radiation where both the speaker and room disappear and now the acoustics of the studio (eg) are most prominent.

 

[chris661]

Guys, this has gone way off-topic.

This particular chap has decided that he'd like a pair of OB speakers, using parts available in Europe, for around 1000 euros.

My suggestion (per side):
1x Eminence Beta 15
1x Fostex 6" FR driver, or Mark Audio of similar size
1x super tweeter if more top-end is needed.

Go for a super-simple first order series crossover and call it good. Mount the FR driver off-centre, crossover values of ~14mH and 200uF.
If more bass is needed, a 2nd Beta 15 per side would do the job, but I'd start with one and go from there.

Chris

 

[AllenB]

Not so much "earlier" as more uniformly and advantageously.

Ok, 'uniformly'.. a diffuse reverberant field can be had either way with the right efforts. Wouldn't it take less effort the further out it happened as the wavefront surface has increased in size?

Also these are all likely to be within 10ms. Optional, but advantageous?

and two unidirectional point sources have all the obvious (and some not so obvious) disadvantages when trying to establish a convincing "image".

Please name one..

Dipoles present all the localization cues that are present in the recording in the first arrival (front wave) sound, while utilizing the room (primarily the front wall) to simulate the distributed sound sources in an actual concert hall. The result is simultaneous good localization with a more natural sense of spaciousness.

I agree that dipoles help simulate spaciousness but more natural, than what?

 

[moray james]

Hi!
My friend wants to build his final speakers and wants it to be OB. He don't speak english, so I'm representing him right now. Room is around 23m^2, he wants to stick to around 1k Euro for now. I'm confused, because we can't find ready project for such build and I don't know speaker stuff good enough to design one, so I have to rely on you We were thinking about 3-way, 15 inch woofer(Eminence beta?), I don't know what for mids and top end. He can get Focal TBe in good price is it worth it?
Any links and feedback is appriciated

mh-audio.nl - Home
Project 9 : Eminence Alpha 15A Experimental Open Baffle Design
Welcome To Manzanita Audio Solutions . Open Baffle Dynamic Speaker Designs
Home of the Edge
Dipolplus - Alles über offene Schallwände
http://www.firstwatt.com/pdf/art_slob.pdf
Gainphile
Tip_55

 

[Pano]

I know this might sound critical at first, but believe me, it's not meant to be. I really don't understand this cult-like following,

LOL! Guess you haven't heard a good one, Scott. I can understand your opinion if you haven't. Most people don't know how to do OB right. Choice of driver, baffle size and crossover are important and different enough from box speakers that many people don't get it right. I've heard more OB speakers done wrong than box speakers.

Done right, they sound very good indeed.

 

[Pano]

Ask your Polish friend what size baffles he can use, and how far away from the walls he can place the baffles. With that information we can lead you to a number of good designs.
There are threads on this very forum.

 

[rayma]

I disagree vehemently. A speaker system that fails to pressurize a room, and that adds a back-wave to make lousy recordings sound better, would, to me, be an INFERIOR design. Please understand, though, you all are OBVIOUSLY free to do as you please, but In my (allowed?) opinion, this is a cult-like-fad following.
I'm guessing part of the reason is, building a superior speaker enclosure is extremely difficult and time consuming. Not to mention expensive. Easier to cut a hole in a plank and call it a day.

The Quad electrostatic (and Magnepans, etc.) are OB and have been well regarded by many for a long time.