26 replies to this topic

[Fury♫]

Well i've been reading up on unity/synergy horns lately and i'm impressed with a lot of aspects of these designs.
In particular the phase response.
The unity has near perfect phase response because all drivers are placed within 1/4 wavelength of eachother (albeit in a horn), and it is said to give incredible coherence.

Sadly i'm not up to speed to design and construct a unity, nor do I have the time for something so complex just yet (have enough projects on the go), but I thought i'd experiment with some drivers I had on hand and design a speaker with exceptionally close center to center (CTC) spacing between drivers, to see how it impacts crossover points and polar response through the crossover region.

One of my other requirements was the ability to not only play loud, but sound effortless doing so.
Ultimately I would have loved to use high efficiency drivers, but due to wanting to use drivers stashed away in my cupboard, this was not possible.

This is where the Peerless Nomex drivers come in.
They use a truncated basket which allows them to be placed flat against each other.
To meet the "loudness" requirements would mean the use of multiple drivers.

I made a quick sketch of the baffle design I had in mind:
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I then sent this off to Andrew at Aslan Acoustics, and he was more then happy to help cut it out on his CNC and ship it down to me...
The result:
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Tonight I had a chance to load one up with drivers, and this is how it looks
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The design uses:
Vifa BC25NC tweeters
Peerless Nomex 5" midranges
Peerless Nomex 8" midbasses


I need to get myself some alligator clips to wire these up easily and have a listen.
I'm going to first try them OB, and take measurements of polar response to see what it's like.
I'll then determine if they're suitable OB, or build enclosures for them.
I won't be going quite as overboard as I did with my high efficiency project, although these will get 25mm mdf boxes with bracing.


Also got to play around with my brothers camera, he has a nice Canon SLR with L series lense... Still getting used to it, but took a few pictures of the new Panasonic drill and jigsaw I bought:

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[romano.inc]

looks awesome mate should get nice and loud! jigsaw looks pretty snazzy too haha

[Drifte.au]

Looks good mate, bet you can't wait to fire them up

[Sorin-Andrei]

Great design - and some awesome tools there too!

[Big_Valven]

Love some hefty peerless cone area

[scraverX]

I'd really like to have enough space for a decent home system but it's just not viable with book cases everywhere...

[muzzy66]

Where on earth did you get those 5" Nomex?

A short while ago I was looking everywhere for them and no one had them!

Does Andrew do cutting like this for anyone, or is he just a friend? I could use somebody to cut the baffles on my new hifi project...they are pre painted so I'm worried I'll screw them up if I do it myself

[Fury♫]

Muzzy, I had to buy a box of them - I have spares if you're after some, pm me

Andrew will do cutting for anyone I believe. I contacted him through SNA. He's very helpful to DIY'ers

[Fury♫]

Well just hooked these things up for a quick listen and wow, the bass is impressive!
It's "immediate" for lack of better word. It's snappy and it hits nicely.
They go quite low too, and the low end roll off is very smooth (as you'd expect from OB).

There's a blaring in the midrange... Sounds a bit shouty at a certain frequency.
My crossover is very rushed 24db @ 3.5khz between mid and tweeter so this doesnt surprise me.
Also it could be the rear wave reflection as the speakers are just leaning against the wall (well now they're sort of firing out into the hallway from behind)...

When I get a chance i'll measure these...
I've got to build a stand of some sort that won't ruin the baffle, and still enable me to put these in a box if i choose to...

[syd-monster]

get em off the wall and play with x-over, they'll come good...
Im a big fan of open baffle.... so props on these Danny!
Also you will want them isolated/decoupled of the ground... some rubber feet would help.
I got a HDS project to add on here, but its lower octave dedicated.

Edited by syd-monster, 13 June 2011 - 12:59 PM.

[Sierra]

Wow Danny ... you are really getting into speaker design in a big way ... very impressive!!!

This is probably a dumb question ... but if you are going to run them open baffle wouldn't a wider baffle have been better?
You're not going to get interference from front and rear waves like that?

[Fury♫]

Hi Al,
Everything is a trade off... bigger baffles take up more space...
I didn't design these to be used OB, and most likely will build boxes for these, i just figured i'd try them OB first.

[Pulse-R]

nice,
nice close driver spacing should suit passive crossovers quite well.

[268669♫]

Looking good Danny,

Nice choice of drivers and a very nice baffle you've got there. Just a quick question, how are you going to get a big enough volume for all those 8's? Or are you happy to roll them off higher?

Ant

[Fury♫]

Looks like the box for the 4 x 8's will be roughly 2.2 cu.ft sealed.
850 x 280 x 400 deep, 25mm thick walls.

There's enough clean excursion with using 4x8's that if I need to use a bit of eq to bring the bottom end up it's not a problem.

The midranges will take up the space above this (350 x 280 x 400) with a divider between them.

The enclosures will be lined with 25mm thick acoustic foam.