Concrete Improvement? (Concrete FE168 EZ)

[Kwast]

Hello everyone. This is my first post.
Normally i read only.

But now I think it's time to ask some of you to give your opinion on one of my building projects. In a couple of weeks it's gone to my brother and I can't test anything there.
How it is started is a long story. Has something to do with alcohol ....
But i/we decided to build a set of concrete speakers. The pictures below show the rest.

[Kwast]

The pictures are from 10 months ago. In the meantime the gaps are filled and some things are polished.
To give an idea of size. They are 136 cm high, 32 cm witdh and 54 cm deep. Estimated weigth is 200 Kg. They are horn loaded. You can see that on the next picture.

[Urchinn]

Wow, we were talking about doing this a couple weeks ago. Please keep us updated with your project. Verrrrrrrrrrrrrrrrrrrrrrrrrrrrry cool.

[Kwast]

Heś a photo of the horn design inside it. It has the same size as the standaard fostex cabinet drawing. There are only les bends and the horn mouth is a little bigger.

[Kwast]

The photo's in previous post where from half way trough the project.
They are already playing in the livingroom. The next photo's show them in there current state.

[rjbond3rd]

Hi Kwast, wow, incredible. How do they sound? Do they need a lot of damping material? Is the "hole" there for structural reasons?

[trd1587]

Hey Kwast,
Can you put Hi-res Photos please so we can see more in details.....
Nice Work......HF must be very "shinny"

Marc

[Kwast]

The sound is quite difficult to descripe.
I had a lot of trouble to mate the rest of the audio system to the speakers.
That's becouse my electronics are realy bad. But recently I did some soldering work on my CD player.

The sound has specific charateristics. Fist of all it has no resonances from the low bas to the upper mids. It sound rather clear. I can not really speak for the high tones of the speakers becouse my amplifier kills a lot of detail.
Second thing that i heard was the placement of singers and instruments.
if you close you're eyes you think they're in the room.
That experience is getting better with every tweak and update on the rest of the system.

Best music for the speakers is acoustic instuments and/or voices.

The placement of the speakers is rather critical. You can hear clearly big differences by moving them to different locations in the room.
That is not my favorite thing to do becouse i can hardly handle them on my own. The couch between the speakers is a realy bad place to sit in the room becouse the horns do things with the room and base tones especially between the speakers.

They heve a little trouble with giving adequate bas for the room. If i place them close to walls it's not a problem but then they have a gap in the stereo sound image. The gap is also a problem of bad sources and amplifier.
Placing them to close to wall's wil also give strange stereo effects becouse of the sidewall reflections.
Concerning low tunes i think it will reach down to about 40 or 50 Hz properly.
You can see the cone really moving. Poor fostex.

Concering damping i've done nearly lothing. The horn is not polished. only in the mouth for estetics. The chamber needed quite a lot of tweaking. There are a lot of socks with stones inside the chamber directly behind the speaker.
Otherwise there was not enough loading into the horn

In the first 40 cm of the horn lay's a little layer of wool or something for dampening. That was enough.

For filtering i use a resistor of 2 ohm and a cap paralel over the speaker.
Becouse it doesn't realy deal with the +3db from 5000Hz or so i added a resistor of 2 ohm in series with the filter and speaker. That give a reasonable flat response to my ears but the fine details in the high tones are negatively affected by that "tweak".

Compared to my other speakers the are a big improvement.

I know that a proper filter design would tacle a lot of issue's
I put both speakers also on woden bloks with gives cleaner base response.

[pathdoc2]

Cool idea. I have no idea how you did this. Maybe you've come up with the next hot trend in audio.

[InclinedPlane]

That's alot of hard work right there.