[Andy G]

I am introducing myself to those whom don't know me.    HI !

I have spent several years "playing" with loudspeakers, but last year I built my first OB loudspeaker, called "Gumby".   http://users.tpg.com.au/users/gradds/ARGOS/Gumby.htm

It wasn't really fully planned as an OB, but I had read stuff from several other that OB sounded good, so I planned the line array section of Gumby so that it was a U-frame with the option of adding a back on if I didn't like it.  Initially he was a bit too strong in the mids, but i found that by padding the U-frame with 2" thick poly wadding things settled down perfectly (to my ears).   I used 4.5" drivers because I managed to pick up a whole heap of the Vifa P11WH really cheap. 
It was obvious that a bass unit was going to be required from the start,  so I experimented with a vented boxed, active bass using the Jaycar 12" carbon driver I had on the shelf, and with some patience it has worked out perfectly (imo).
I love Gumby, he is listenable all day at sensible volumes, but can really go loud if I desire )

The second OB was designed from the start as such.  I had 4 x Vifa M11WG's on the shelf and some 10" bass drivers.  Now John K's Nao and SL's Orion were both designed using dipole sub drivers, this lead to the obvious use of actively EQ'd 8" mids (for excursion reasons) and hence to a lower, steeper tweeter x-o point. One way of approaching things.  I chose to approach things from a simpler perspetive, use the 4.5" mids in an mtm arrangement, then use the 10" bass up to the point where the mtm OB naturally rolls-off.  IMO, the end result has created one of the most listenable speakers I have ever made. The only drawback being the limits of the small mid drivers, wrt volume level, they do struggle with VERY loud. 
http://users.tpg.com.au/users/gradds/ARGOS/blackwood.html

The third OB I have had the pleasure to meet was one done by Peter from RZAudio. He heard 'Blackwood' and immediately set out doing an OB himself.
His used (iirc) Scan drivers for the OB mid and tweeter, and then uses an active Vifa M22 bass reflex cab for the bass.  We played with the active x-o a bit until we got it just right.  Peter is much more fastidious than I, so he has posted the whole speaker, construction, diagrams etc. One SWEET speaker  !!!
http://www.rzaudio.com/rz52/rzss.htm

So.... I have no intention on building anything but OB mid from now on ....

boxes for mids are passe !!!

One day i may get around to doing an OB bass, but all the EQ needed worries me. I prefer to let thing happen as they happen.

[Bob in St. Louis]

Andy those are all REAL good looking speakers.
VERY nicely done, my hat's off to 'ya. 

You'll fit in nicely in the OB world!

Bob

[mcgsxr]

Welcome to AC's Open Baffle world!

Love your designs, nicely done!

[Wind Chaser]

Hey Andy,

I see you're from New Castle.  If you don't already know Nigel Smith (AC moniker Oldtimer) you might want to make his acquaintance.  He's a real gentleman, pro joiner and OB enthusiast with plenty of experience.

[Bob in St. Louis]

Wind Chaser, Good point about Nigel.

Andy - I chat with a few guys on the Decware forums that are very knowledgable OBers and they live close to you. There must be something in the water down there that breeds OB  Some real smart fellows around that area. If you need an introduction let me know, I'll get you guys in touch.

Bob

[Russell Dawkins]

Hi Andy, welcome to AudioCircle.

I see on your website that you also build PA speakers. Now that you are into open baffle mids, maybe you'd like to see a design for a functional full range open baffle PA design:

http://www.mfk-projects.com/dipole_pa_system.htm

Russell

[Andy G]

Hey Andy,

I see you're from Newcastle.  If you don't already know Nigel Smith (AC moniker Oldtimer) you might want to make his acquaintance.  He's a real gentleman, pro joiner and OB enthusiast with plenty of experience.

Yep, I have met Nigel, he came around here once to have a listen to Gumby. He's also a sorta 'single driver' guy and I think he found the 3-way, active bass, OB line array concept a bit over the top (gees, can't think why)

I really must arrange to go and have a listen to his at some stage.

[Andy G]

Wind Chaser, Good point about Nigel.

Andy - I chat with a few guys on the Decware forums that are very knowledgable OBers and they live close to you. There must be something in the water down there that breeds OB  Some real smart fellows around that area. If you need an introduction let me know, I'll get you guys in touch.

Bob

It would certainly be nice to know if there are other DIY guys apart from Peter, Nigel and myself in Newcastle.   Sydney if closeish, but nowhere else is !!
By all means let them know we exist up here, always nice to meet fellow loonies !!

[Bob in St. Louis]

Andy,  I threw your name in the mix at the Decware forum here:
http://www.decware.com/cgi-bin/yabb2/YaBB.pl?num=1171415996/101#101
(Post #101) ....and linked them to here.

Bob

[Wind Chaser]

Bob,

Nice looking baffles you have there.  How do they sound without the bottom fiberglass shield?

[Bob in St. Louis]

Wind Chaser, I only have the one built. The other is still in pieces waiting for assembly. I didn't intend on having the first one this much built before starting the second, but after the HUGE P.I.T.A. the fiberglass turned out to be, the entire project might be scrapped???? Don't know yet.

Regarding the sound, I watched the second have of a movie with the driver installed in the baffle before the glass went on. No music. So I don't really have much of a listening impression yet.

Have you seen the thread that started this all?
http://www.audiocircle.com/index.php?topic=36862.0
The build starts on about page nine.

Bob

[SamL]

Hi Andy,

What is the best option of wiring 2 midbass in the MTM for series crossover? In series or parallel?
Will it be eaiser for the amp to drive a series crossover MTM if I am using 2 x 4 Ohm midbass drive and a 4 Ohm tweeter. Comparing to 2 x 8 Ohm midbass and a 8 Ohm tweeter?

TIA,
Sam

 

[rabbitz]

Andy was moving house so I'm not sure if he's up and running again.

Normally with 8R drivers you run them in parallel and 4R drivers in series so you get 4R and 8R respectively. You just have to be aware of any major dips in the impedance as these can drop very low when run in parallel. The tweeter doesn't matter and 4R or 8R with either is no problem. I wouldn't think there would be too many 8R tweeters around as most seem to be 4R-6R.

[SamL]

Hi Rabbitz,

Thanks for your reply. It make perfect sense. Your open baffle TM with series crossover partner with a close bass driver driven by another amp has open up many option for me.  Well, since you are using passive crossover for the TM, how high do you need to turn your volume knob to have a decent listening level? I believe you are using GK1 and it has 6db gain. I wonder if it is possible to use a passive preamp with 0 gain in such setup? I currently have a working AKSA100N and a AKSA55N+ kit that yet to be build.

Oh yes! Using the same series crossover, how low would you cross the SS9700? Well... I somehow prefer the sound when tweeter is cross low.

[rabbitz]

Hi Sam

The volume is mostly set below 10 o'clock or 11 o'clock if I feel the need to blast.

The gain of the AKSA is around 32dB if I remember right and the pre has 6dB (which is a tad too much for my system). Even with 0dB gain in the pre, the AKSA would provide ample gain and have the pot around 12 o'clock for good listening volume. I've never had success with passive pre's on the AKSA 55N+ and am currently using an SKpre modified with a gain a 6dB instead of 12dB.

My tweeter is crossed over at about 2800Hz (2nd order electrical) to work in with the mid woofer hump but I have had it running when crossed over around 2400Hz (1st order electrical) without problems. The S2905 is sort of like a tweeter-mid as it doesn't roll off until just above 1000Hz.

[SamL]

Hi Rabbitz,

How do you connect the pre amp to the Aksa power amp and 2 sub amp? Do you connect them in series or parallel? Or your pre amp have 2 line out?

[rabbitz]

Preamp has 2 lines out. Otherwise just use a splitter or adaptor with 2 sockets.

[HiFiNutNut]

Hi,

I live in northwest part of Sydney and Newcastle is 1.5 hour away?

I will actually be getting my new open baffle speakers built by a guy in Newcastle and will go to the Home Show there to meet the guy this weekend.

It would be good if we could listen to each other's stuff. I am particularly interested in well-designed, full range single driver speaker because I have not heard them before. In Sydney, there is the Sydney Audio Club I am yet to join.

Regards,
Bill

[rabbitz]

Bill

That wouldn't be Nigel building them? B200?