Audax multi-driver project

Dedicated to those large boxes at one end of the room
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SimonC
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#1 Audax multi-driver project

Post by SimonC »

Hi folks,

After playing with single drivers for a while now, and also being inspired by Scott and Colin's various tall narrow multi-driver designs, I keep looking at my collection of audax mid-bass drivers and can't help thinking mmm, there's potential there to have some fun (you can tell I don't get out much...)

Anyway, I've got 2xHM100CO and 2xHM130CO to hand, a few tweeters etc kicking around, plus a DCX2496... :-)

I like the aesthetics of the tall narrow multi-driver designs, and these drivers lend themselves to being mounted close together, so I've started throwing together a rough design outline.

Taking the volumes for the Vb1 curves from the datasheets as a starting point (they were the largest volumes, I can always reduce the volume very easily in use) get to a volume of about 55l, which gives me internal measurements of about 1000mm high, 140mm wide and 400mm deep. Port dia and length I can tune to suit. I'm going to get in the right ball-park with a simple sim for a vented box with a composite driver (not perfect by any means, but I'm only after a starting point).

I've put together an outline of the design, its a mule thats made to be modular and let me play around with different drivers and ports.

http://www.madisound.com/store/manuals/hm100c0.pdf
http://www.madisound.com/store/manuals/hm130c0.pdf

This is a learning exercise, I'm sure there will be loads of things I've got wrong, over-looked and have made bad assumptions about, but for me its as much about the journey as the final outcome...

Onwards!
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layout2.png
layout1.png
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Dave the bass
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#2 Re: Audax multi-driver project

Post by Dave the bass »

SimonC wrote:Hi folks,

I keep looking at my collection of audax mid-bass drivers and can't help thinking mmm, ....
"..maybe I should sell them all and just buy a pair of Fostex 4inch'ers"...

I finished off your sentence for you MrC! No need to thank me :)

Heheheheheheheheh(etc).

DTB
"The fat bourgeois and his doppelganger"
chris661
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#3

Post by chris661 »

I'd consider making the entire baffle removable if possible - much more room to play around that way.

Looks like a fun project, though.

Chris
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Toppsy
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#4

Post by Toppsy »

Interesting project you have there Simon. I wish you luck.

With 3 different sized drivers in this design are you intending making it a 3-way speaker? In which case I would have expected the 2 smaller drivers to be acting as mid-range and in there own closed volume area within the cabinet. At least that is how I understand all 3-way speakers are designed and the rest of the cabinet volume is for the bass drivers. The tweeter would also be in a sealed small space but this is not so important as most (if not all tweeters) are sealed units so don't radiate any rear reflections into the cabinet.

One other observation being the internal baffle as detailed. Not sure this will work this way to dampen out and break up internal standing waves. I'm sure Scott could elaborate more. I believe this would be better horizontal.
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IslandPink
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#5

Post by IslandPink »

I don't know if you've looked at Troelsgraven's site Simon, but there may be some useful ideas & construction details here, even if not directly applicable to your drivers -
http://www.troelsgravesen.dk/Diy_Loudsp ... ojects.htm
"Once you find out ... the Circumstances ; then you can go out"
SimonC
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#6 Re: Audax multi-driver project

Post by SimonC »

Dave the bass wrote:
SimonC wrote:Hi folks,

I keep looking at my collection of audax mid-bass drivers and can't help thinking mmm, ....
"..maybe I should sell them all and just buy a pair of Fostex 4inch'ers"...

I finished off your sentence for you MrC! No need to thank me :)

Heheheheheheheheh(etc).

DTB
Why would I want to go 4" when I've got such nice Fostex 3"s in my FF85/FE103 collection?

But slightly more seriously, I did consider doing that but those smaller audax units have got something about them that make me want to give them a project.

Onwards!
SimonC
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Location: West Yorkshire

#7

Post by SimonC »

chris661 wrote:I'd consider making the entire baffle removable if possible - much more room to play around that way.

Looks like a fun project, though.

Chris
Hi Chris,

Both the front and rear baffles are fully removable, its not that clear on the quick layout prints I did, but there's an internal frame that they all fasten to. The idea being that if I want to play around with different drivers, or driver spacing, I just make a new baffle panel. Same for the tweeter and ports panels.

Simon C
SimonC
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#8

Post by SimonC »

Toppsy wrote:Interesting project you have there Simon. I wish you luck.

With 3 different sized drivers in this design are you intending making it a 3-way speaker? In which case I would have expected the 2 smaller drivers to be acting as mid-range and in there own closed volume area within the cabinet. At least that is how I understand all 3-way speakers are designed and the rest of the cabinet volume is for the bass drivers. The tweeter would also be in a sealed small space but this is not so important as most (if not all tweeters) are sealed units so don't radiate any rear reflections into the cabinet.

One other observation being the internal baffle as detailed. Not sure this will work this way to dampen out and break up internal standing waves. I'm sure Scott could elaborate more. I believe this would be better horizontal.
Hi Colin,

I'm glad you have brought up some interesting comments... I was planning on it being a big 2 way, with the 4 drivers series/paralleled to get them to around 8ohm (I know it will take some current to drive it though, F4 anyone?), but now I'm thinking about building some slotted internal sections that would let me partition it down if needed.

Tweeter wise, I was being lazy as the tweeter I have to hand is sealed. You raised a very good point if I want to swap to an open backed one in future. I'm going to seal it off while its still on the drawing board.

Internal bracing is an interesting subject, my initial idea's have been around bracing the long thin side panels to reduce their resonance, rather than trying to stop internal standing waves. There's also a school of thought that uses thin panels (12mm thk) and lot of bracing to move the panel resonances up high enough to where they don't get excited (que DTB comment about excited panels...). Its on area's like this where the forum comes into its own, there are lots of ways of doing it and lots of reasons why, and its great to have people throw them into the mix for discussion.

Keep them coming :)

Simon C
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