MJK - A Method for Designing a Compact Back Loaded Horn Loudspeaker System

[gaston senac]

Has anyone read the MJK article "A Method for Designing a Compact Back Loaded Horn Loudspeaker System (added 06/21/12)" ?
What about any builds or comments?
Other drivers that can be used?

The only reference on DIYaudio is this one: http://www.diyaudio.com/forums/full-range/218332-smaller-fostex-backloaded-horns.html#post3135704
Also: why is the MJK account "Account disabled at member's request" ?

 

[mp9]

I read it, somewhat different approach then other designs i'm familiar with. Although the requisite corner loading does limit it's use room/placement wise, was wondering if a version for 6.5" drivers would work well with the new Mark Audio 12P driver?

 

[chrisb]

I read it, somewhat different approach then other designs i'm familiar with. Although the requisite corner loading does limit it's use room/placement wise, was wondering if a version for 6.5" drivers would work well with the new Mark Audio 12P driver?

probably - someone just needs to do the math - it's probably a whole lot easier to build a successful BLH than to design one (or more)

 

[tsiros]

I don't get the idea behind the whole thing

Is the basis of it the fact that in a normal cabinet you "get rid" of the back-propagating waves by absorbing them inside the cabinet (thus losing pretty much half the acoustic energy that the speaker driver produces) but in a BLH you design the cabinet not to get rid of the back-wave but instead take advantage of it so, in the end, you get something for nothing? ("nothing" in this case being "spend quite some time designing it" ) ?

Um

how big would a decent BLH be for a pair of 12" AN CFs ?

 

[Scottmoose]

You don't get anything for nothing in this life. All chambered back-horns are essentially more or less extreme variations on the bass reflex theme, and like all back loads, are only useful over a relatively narrow BW.

The short version is that Martin's added an internal Helmholtz resonator to his back-horn, tuned to the design / target Fh to increase the acoustic low-pass slope.

 

[RK1]

in my opinion, you will first need to:
- determine the lower frequency of operation - it determines the diameter of the outlet (it is important from the point of view of size),
- then selects the transducer,
- later determines the length of the line, and other parameters.

 

[Scottmoose]

I don't think that has much to do with the OP's question. However. Some general points:

-The first thing one normally does is to determine the requirements, budget and size constraints

-Evaluate a range of drive units that meet, or will meet, the above. Select preferred unit from shortlist

-The horn terminus size determines the lowest frequency it is impedance matched to, once boundary conditions are accounted for. Axial length and taper determines the 1/4 wave cutoff frequency. These do not necessarily have to be one and the same. Standard horn profile equations become progressively less useful the more the horn expansion is compromised / reduced.

 

[RK1]

Everything is correct (almost)
Scottmoose - Can you show me some of your designs Back Loaded Horn ?

 

[Scottmoose]

What have I said that is incorrect?

Surely. I don't want this thread to go any further off topic though since it's about Martin's box, not mine, nor is it a thread about horn design in general. However, if you want a handful of my designs, look up Frugel Horn 3 (done with DaveD & ChrisB), all of the Spawn designs (past & current) on the Frugal-horn.com site, the Madisound BK12m etc.

 

[RK1]

Very interesting.
Could you tell me something about this design.
Maybe not here (PW ?), so as not to disturb others.
Have a nice day

 

[Scottmoose]

Which design in particular?

 

[RK1]

For example The Frugel-Horn
Could you tel me something more about this project ?

 

[planet10]

Start here:

http://www.diyaudio.com/forums/full-range/172605-frugel-horn-mk3.html

IMHO, the FH3 was an inspired flash of genius on Scott's part.

dave

 

[Bigun]

completely off topic, but Scott, if you fancy a Canadian style moose for your avatar I think you should get a nice shot from the Fall when their antlers are in full display.

I'm a big fan of this animal, and have experienced one arising out of a lake and walking through my camp site early one morning in the middle of the Canadian wilderness.

 

[RK1]

Good - thank you
"genius" - sounds good

 

[Scottmoose]

completely off topic, but Scott, if you fancy a Canadian style moose for your avatar I think you should get a nice shot from the Fall when their antlers are in full display.

I'm a big fan of this animal, and have experienced one arising out of a lake and walking through my camp site early one morning in the middle of the Canadian wilderness.

A fine moose (a creature I have a great liking for). It's the nose that does it for me. As it happens, my avatar is actually of a yak, which I also happen to like, particularly after reading Donald Bisset's various stories feature said creature.

 

[chrisb]

A fine moose (a creature I have a great liking for). It's the nose that does it for me. As it happens, my avatar is actually of a yak, which I also happen to like, particularly after reading Donald Bisset's various stories feature said creature.

BBC NEWS | Science/Nature | Moose back on the loose


with or without an impressive rack, a full grown moose is not to be trifled with, as any game hunter or truck driver in the interior of BC will tell you

I don't think anyone has successfully tried to domestic the species

Scott's avatar is

Datei:Yak at third lake in Gokyo.jpg ? Wikipedia

An externally hosted image should be here but it was not working when we last tested it.

I'm not sure if he's been up close and personal with one, but for some reason I suspect it'd be like Hans said about the Tauntaun sleeping bag


survive the solar orbit celebration mostly intact, Mr L?

 

[gafhenderson]

You don't get anything for nothing in this life. All chambered back-horns are essentially more or less extreme variations on the bass reflex theme, and like all back loads, are only useful over a relatively narrow BW.

The short version is that Martin's added an internal Helmholtz resonator to his back-horn, tuned to the design / target Fh to increase the acoustic low-pass slope.

if possible could you give me a quick brief on what exactly a helmholtz resonator does and why it would be included in a design?

thanks

 

[Scottmoose]

A Helmholtz resonantor is a cavity that resonates at a specific frequency -well, narrow BW of frequencies to be exact, since it doesn't just appear at one point & instantly vanish to either side of it. They're often used in loudspeaker design to reinforce the low-range: that's what a bass-reflex enclosure is. However, they can also be used for the opposite effect: to trap a specific frequency or narrow BW of frequencies. That's how some of the big bass-traps you see work. They're just boxes with a port, tuned to a specific problem frequency.

What we have here is an internal version of this. Martin has used it tuned to, or slightly above, the upper corner frequency of the horn, to provide a steeper acoustic low-pass slope than it would otherwise have -it's not a new idea, but it isn't used all that often either. It's a useful card to have up your sleeve, but there are a couple of things to keep in mind: while it will increase the rate of the initial roll-off, the resulting slope will be akin to a cauer (eliptical) filter since the resonator / absorber is by nature a narrow band device. Therefore, you need to ensure you have a reasonably fast acoustic low-pass initially to ensure the secondary peak that will result above the tuning frequency of the absorber is at a sufficiently low level not to be noticable. If you've done that, as Martin evidently has, you're in business.

 

[chrisb]

IINM, Lowther and likely others have used the HR approach, but perhaps not as thoroughly "new" mathed out as any of Martin's projects would be.