Ok, so I want to build my first open-baffle full-range - diyAudio
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Old 25th March 2011, 05:30 PM   #1
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Default Ok, so I want to build my first open-baffle full-range

Hi everyone - as the title says I decided I want to build a pair of open-baffle full range speakers

I have a Peter Daniel-copy Gainclone to drive them, so high sensitivity would be desirable, although not critical.

I would like to have just one full-range driver, supported by a bass unit if necessary. As far as building a case is concerned, I do have some carpentry tool and experience, although I would prefer something relatively simple to build.

The listening room is 3.5 x 4.5 metres, but I may be moving to a bigger space, so I want the speakers to be fairly universal in this respect.

I was looking at these drivers:
- Alpair 10.2 from Mark Audio - I really like these for their looks and engineering, but Im not sure if they will work well in an open baffle?...
- Visaton B 200 - there are some great reviews on the net about these Visatons in a NoBox - but would I be able to modify the appearance of the NoBox bit? I really couldnt live with a plain square box like this...

Any advice will be most appreciated.
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Old 25th March 2011, 05:45 PM   #2
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My first suggestion is that you visit Martin's (MJK's) site: www.quarter-wave.com

I have built a version of his small, passive OB using Fostex FF85k and Eminence Alpha 15a, which I like very much.

Martin's MathCAD worksheets include OB modeling, and I can recommend them as well.

There are at least two schools of philosophy as regards OB design. I admit that based on my experience, I side with Martin. YMMV

Cheers, Jim
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Old 26th March 2011, 03:19 AM   #3
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Quote:
Originally Posted by Jim Shearer View Post
My first suggestion is that you visit Martin's (MJK's) site: Quarter Wavelength Loudspeaker Design

There are at least two schools of philosophy as regards OB design. I admit that based on my experience, I side with Martin. YMMV

Cheers, Jim
I went with a Fostex fe103e over an Eminence Alpha 15A and they still make me smile.
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Old 26th March 2011, 04:05 AM   #4
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Thanks for the link, very informative.

However, I decided that I really, really want to avoid crossover components on the full range driver... I could probably live with signal degradation and phase shifts in the bass, but I want to keep the main spectrum pure and "direct". This, unfortunately rules out both the NoBox and MJK's Fostex/Eminence design...

I could still try building a single-driver open baffle. How big a baffle would have to be to allow a full-range driver like Alpair 10.2 to go into the 60Hz regions? Is there a way to calculate (or approximate) this?

Or, would it be possible to use a bass driver that has significantly higher sensitivity than the fullrange and simply shape the bass driver response so that it matches fullrange's roll-off?
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Old 26th March 2011, 05:51 AM   #5
mor2bz is offline mor2bz  United States
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EV sp12b is as good as you are going to do.

make sure the baffle is big. if do a JE Labs baffle, add an in. to
the bottom of the sides so the front baffle is angled back a bit more.

if you go any smaller than this you are not going to get much bass
and it is not going to go very loud.

you are up against some very severe limitations with your parameters.

I have some in ply baffles if you want them. best offer. will do with
5 watts, better with 10 or 20.
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Old 26th March 2011, 12:58 PM   #6
MJK is offline MJK  United States
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Quote:
Originally Posted by uncle_leon View Post
However, I decided that I really, really want to avoid crossover components on the full range driver... I could probably live with signal degradation and phase shifts in the bass, but I want to keep the main spectrum pure and "direct". This, unfortunately rules out both the NoBox and MJK's Fostex/Eminence design...
Without any crossover on your full range driver, bass frequencies will generate large cone deflections and the associated distortion and compression. Mounted on an OB, the driver's motion is no longer controlled by an enclosure at low frequencies. This will get really bad as you turn up the volume. I would hazard a guess that this problem would be a bigger issue then anything a crossover might do (and I don't agree that a crossover is automatically bad) to the purity of the sound. It is all about trade-offs, I would keep the crossover.

Martin
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Old 26th March 2011, 01:21 PM   #7
Gyuri is offline Gyuri  Hungary
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I apologize for having my post to something, which I do not understand.
But common sense and my experience tells me no harm, if the full range driver is relieved of the lower frequencies, thus preserving their physical integrity. This course is essential if we like the large volume. (and our full range loudspeakers.) I think if we use an OB loudspeaker, the crossover is required. The most active crossover, and multiamp environment, I think.
Wacky Gyuri
P.S.:
Now I'm going to my brain runted, Martin says exactly what I am, just with different words.
Well, he just knows.
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Last edited by Gyuri; 26th March 2011 at 01:35 PM.
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Old 26th March 2011, 01:45 PM   #8
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Quote:
Originally Posted by uncle_leon View Post
However, I decided that I really, really want to avoid crossover components on the full range driver... I could probably live with signal degradation and phase shifts in the bass, but I want to keep the main spectrum pure and "direct".
Is this based on experience? I would suggest trying both if you haven't experienced both. It's easy to try. Having tried both I can say that I have no issues with my crossover at 300Hz. As Martin suggested the benefits far outweigh the perceived drawbacks. Of course if you limit your listening to small acoustic groups with no upright bass, or drums, then listening with out a crossover can be quite rewarding. However as soon as any bass/volume is introduced you might find you prefer the crossover.
Joe
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Old 26th March 2011, 03:14 PM   #9
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I think you'll find this link interesting:
Open Baffle
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Old 26th March 2011, 03:59 PM   #10
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I know what you mean guys, and I realise I'm swimming against the current here. The reason I insist on crossover-less full range is that my experiences with other audio devices so far confirmed the simple truth - with every component you add, you take something away from the original information in the recording. I'm not talking about distortion, frequency response and such, but rather the emotion, the "soul" of music. I hope you understand what I'm trying to say...

So after some thinking and research I arrived at these two concepts: firstly open baffle, which is commonly described as pure and direct, and secondly full range as inherently coherent and requiring no crossover. So the obvious thought was "Let's make an open-baffle full-range loudspeaker and have the best of both worlds" I realise there are some serious challenges with this approach, and it seems rarely employed, but hey, every speaker design has challenges I want to at least try before I give up!

@Josephjcole - no, I haven't tried either of these approaches in practise - as the thread title says, it's my first build of this type.

@Racket Scientist - fantastic link! Just what I was looking for! I think I'm getting a lot closer to my goal now. I like that baffle idea, and I am nearly sure I can make it into something at least remotely attractive. So now it would be just a matter of choosing the right driver for the job...

Of course I'm still open to alternative suggestions.
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