[Kim Schultz]

Hi.

First I would like to introduce myself as this is my first post here.

I have made alot of different speakers from 2way/3way to fullrangers and horns, both big Oris style and small OB waveguides.
I moved to horns and pa woofers when I wanted a HT, but before that I enjoyed Lowther and Coral fullrangers in front and backloaded horns.
Now I want to get some of that single driver magic back, and at the same time eliminate the tone from the cabinet.

In comes the OB, I tried it many years ago with a Philips fullrange and while it had some strong points, it could not compete with the frontloaded Lowthers I had at that time.

Then I read a thread over at diyaudio.com, by Simon who used the Eminence Beta-8a with a APT-50 tweeter, and thought I would try the Beta-8a in an OB as I already had some laying around from another project.

I have made a thread over there, but found this forum afterwards, and it seems like a better place to get help with an OB setup.

you can see the diyaudio.com thread http://www.diyaudio.com/forums/multi-way/178239-my-first-ob-loudspeaker-seeking-advice.html

In short my goal is to use the Beta-8a fullrange with a compression driver on a small OS WG, crossed as high as I can get away with.
For woofer I have a Fostex FW405 with new foam surround which brought the fs and qts up abit (fs=29,6hz, Qts=0,54), making it better for OB duty.

I´m using an Eminence PSD2002S with removed backchamber now, but will try other options too for the tweeter.
The woofer will have it´s own amp and active crossover.

I have a couple of questions:

1. Baffle size. I thought about 40cm wide for the mid and tweeter, and a h-baffle for the woofer, but it might be better with a u-baffle and then use the Alpha 15 driver instead of the Fostex.

2. Driver placement. Should the mid be on top or bottom, should the drivers be in line vertically or offset ?

Thanks in advance.

[Kim Schultz]

Just did a bit of tweaking and took some new measurements.

2nd order HP on tweeter, 4,2uF + 0,28mh and 21ohm + 3ohm lpad.
Mid run fullrange.
Measurement done at 1m/15° to the right (near tweeter) 1/3octave smoothing.

[Kim Schultz]

New crossover again 

3rd order, 2,4uF + 0,28mH + 2,8uF and 17,5ohm + 4ohm lpad because I thought there was a bit to much overlap in the 2nd order.
It also has a gradual rolloff which means it sounds great even when played very loud.

[-Richard-]

Hi Kim ~

I have an off-topic question I would like to ask you... if it is too irrelevant just ignore it.

You seem to have built some very sophisticated speakers in the past that ran the gamut of different design approaches... did your explorations into different approaches come from a sense of adventure or were you actually dissatisfied with everything you built in some way?

I am genuinely interested in your thinking here.

With Warmest Regards ~ Richard

[Kim Schultz]

Hi Richard.

I really enjoy learning new things, which also brought me into the world of wood turning, as I think a wood waveguide is more beautiful than an fiberglass one, even if the fiberglass is more accurate.

As so many others I started by building a couple of 2way speakers, with and without woofer modules. Then I bought the plans for the Shamrock SE-1 and SE-2, and later paired them with a AN kit1 300B amp. This setup I enjoyed them for a couple of years.

But having said SE tube amp you must say fullrange drivers, so I found the fullrange driver forum and took my old Philips papercone garage speakers, and build several different cabinets for them.
They convinced me to try more fullrange drivers, and I played around with some cheap car speakers, Coral Beta 8 and Lowther PM6C in Acousta 115 backloaded horns, they had great midrange, but lacked deep bass and HF extension, and I couldn't integrate a sub that could keep up with the speed of the BL horn, they also sounded a bit pressed with complex and loud music.

This led me to sell the SE-2´s as after getting used to the fullrange sound, I could hear the tonal differences between the drivers.

Then I decided to make some tractrix 200hz fiberglass horns and bought a used pair of Lowther PM2A drivers.
The Oris style lowther based speakers paired with 15" pa woofers, had the best midrange and coherency I have ever heard, they also had good bass but lacked hf extension, and again I never could integrate a tweeter in the setup, and as with all old Lowther drivers, the foam disappeared.

I then wanted a projector and had to sell the AN kit1 amp (which I still regret btw).

So I used the Corals in some Fidelio cabinets and later swithed to Monacor SPH-60X in some wall mounted speakers.

It wasn´t until I moved to a bigger house I took up the serious music listening again.
I now have a dedicated room for HT and have build some Pi4 clones with JBL bass and Altec compression drivers. I planned to build some Pi7 clones but couldn´t decide if I should give the Lowther another try, or try something different.

The compression and PA drivers do something right and I wanted to use them again, so I decided to give the OS waveguides a shot after having read about El Geddes speakers.

I build some 2 ways with coral 12" bass and 1" drivers. They where nice but lacked something and I got bored of them after a while. So I pulled out the Coral Beta´s again and put them in bass reflex cabinets, but they sounded boxy and had a shrill top end. Maybe it could have been cured with a tube amp.

I then read about Simon´s OB project with the Eminence Beta 8 mid, and decided to give an OB a try as I had some Eminence Beta 8 drivers already and always thought they had a very nice midrange.

It sounds very promising and I will make another baffle today, and set it up in the HT room.

As you can see my loudspeaker journey is both because I like trying new approaches, and because I´m still looking for the best loudspeaker compromise for me.

Best regards
Kim

[-Richard-]

Thanks Kim... a very thoughtful overview of your audio/music journey... very interesting.

I am extremely interested in what your thoughts are about your latest OB adventure with the Eminence Beta 8 drivers. Thanks for sharing with us.

With Warmest Regards ~ Richard

[Kim Schultz]

I did some more tweaking today and realised I had too much lower midrange, so I put a 10uF cap with a 6,5ohm bypass resistor i parallel with the mid driver.

I also decided that using the subwoofer amp with the Fostex for OB bass, will not work.
The crossover can only be set as high as 150hz, then it sounds boomy and there is still a hole between the woofer and the mid.

I´ll try to use a BR with the fostex until I get a better OB woofer.