Full range OB: some simple questions

[Roushon]

I am planing a very simple project. A 12inches full range speaker
placed on a 18inches x 18inches baffle and mounted on the
wall at 18inches distance from the wall. Does it make any sense? Will
it reproduce a reasonable good sound? Do I need some custom
made speaker for this project?

Sorry for any stupid question. I have almost no idea in speaker building
but need to build one in the simplest possible way. So thought
of full range and OB type.


Thanks and regards
Roushon.

[T101]

You don't need custom speaker! And IMHO custom speakers are not for beginners like you and me!

You will definitely need that program tho: Home of the Edge

Download it, select OB in the main window, turn all all options in the supplemental window for compensating circuits.

Then use it to see what the SPL of an ideal speaker will be with your OB.

The predicted response should look something like the attached picture.

As for the sound it is possible that you might like the light and precise midrange of such OB with relatively small dimensions compared to the speaker size.

18 inches is IMHO the minimal distance between the OB and the wall behind it. There are some opinions that on such or smaller distance the OB is no more an OB which I don't share. My experience is that the OB should not be parallel to the wall behind it.

From the picture it's obvious that you will not have any bass or at least for sure you will not have deep bass. It is possible somewhere in the room deep bass to emerge tho, but that is not something to rely on!

I think that on greater volumes some inter-modulation between the reflected low frequencies and the ones from the front side might occur - that means distortion and it's a very unpleasant kind of distortion - it occurs when OB is too close to a wall and the volume is higher.

There are very simple ways to build OB, it's true that a board with a hole in it is the simplest, but the other designs are not much more complicated.

I suggest you to read as much as possible if not all of that site Quarter Wavelength Loudspeaker Design - especially the OB articles. - it's not necessary to understand all but your general knowledge on the matter will increase dramatically!

Best Regards!

[brookbh]

When using a a fullrange by itself on an open baffle, you will need a considerably large baffle (think JE labs or the big betsy baffle with hinges).

What 12" driver are using?

If you are not going to use a sub with this, then I would suggest placing the 18 x 18 inch baffle on the floor and tilt the FR up to the listening position (15 degrees or so IIRC). This should give you more low end out of the FR, and you won't have to worry about mounting anything on the wall.

[preiter]

OB is very easy to experiment with. You can make baffles out of cardboard even. Mock it up and see how it sounds. See how things change with the baffle size.

Simulations are great, too, but nothing beats just trying it out for yourself.

[TerryO]

Originally Posted by preiter

OB is very easy to experiment with. You can make baffles out of cardboard even. Mock it up and see how it sounds. See how things change with the baffle size.

Simulations are great, too, but nothing beats just trying it out for yourself.

I agree, with duct tape and extra cardboard, you can try out different baffle sizes to your heart's content! It's instructive, especially along with modeling software and just a lot fun.

Best Regards,
TerryO

[hitsware]

Originally Posted by TerryO

I agree, with duct tape and extra cardboard, you can try out different baffle sizes to your heart's content! It's instructive, especially along with modeling software and just a lot fun.

Best Regards,
TerryO

A true subtlety of OB is that you can mount the baffle
to the driver, rather than the usual mount the driver to
the baffle.

[Roushon]

Sorry for being late in acknowledgement.

Thanks to all for your informative replies. I did download the software pointed out by
T101 and tried different possibilities. It is almost impossible to get the low frequencies. Also
suggested by Brookbh, that I need a very big baffle and some more searches give me a good
baffle size is about 3feet x 2 1/2 feet. My purpose is lost. I do not have enough space to
keep such large baffles. Definitely I will experiment with this in the future when I move to a
large apartment. It is a great learning experience.

For the time being can someone please suggest a closed box type
design with a full range speaker which is also easy to build and wall-mountable size for my
100wRMS per channel amplifier. By small I mean each box is 1 1/2 to 2 cubic feet in
size.

Regards
Roushon.

[T101]

Is it possible for you to make two sealed small/medium size enclosures and put in them car audio woofers... they can stay on the floor and there is no necessity for an exact placing...
And you can make your OB's with the full range...

It would be best if you have an A/V receiver 99% of them have variable built in crossover which at leats gives full signal range to the main speakers and only high pass variable 50-200 hz to the satelytes

I have a Pioneer VSX series receiver which I very successfully use for experiments before designing passive crossover, additionally it has separate level control for each chanel...

In that case you can only focus on baffle step compensation and low pass filter for the subs...

If you are OK with subs I am sure that here threre are enough people who can aid you in designing the enclosures and filters

You also can go with any big and cheap pro driver 15-18 inch with RL compensation and enjoy lots of bass...

[preiter]

Originally Posted by Roushon

Sorry for being late in acknowledgement.

Thanks to all for your informative replies. I did download the software pointed out by
T101 and tried different possibilities. It is almost impossible to get the low frequencies. Also
suggested by Brookbh, that I need a very big baffle and some more searches give me a good
baffle size is about 3feet x 2 1/2 feet. My purpose is lost. I do not have enough space to
keep such large baffles.

Open baffles do require space, both in the size of the baffle, and the requirement to have lots of space all around the speaker.

Plenty of other fun designs out there, though.

[brookbh]

I did not mean to deter you from building an OB, actually quite the opposite. Take a look at this site to give you some idea of how you could build a larger baffle on a smaller standing footprint.

Wild Burro Audio Labs - Fullrange Speaker Projects - Basic Open Baffle Design