Finally built a prototype, dual FRS8 in pentagon-TL

[ßart West-VL.]

It took a very long time to get to this enclosure but I'm glad it's getting back on track now, it floated around in my head for years!

Today I have put in the the two drivers, FRS8 - 8 Ohm and hooked them up in parallel, to a channel of my amplifier. They sound surprisingly good.

If anyone is curious enough to put it in a simulation program, I would be very happy and interested. Let me know what numbers you need.

The thought of a pentagon was preceded by a triangle but the problem here is, that the volume of the TL is reduced by half compared to a rectangular box while a pentagon is larger than a rectangle. I didn't want to use a rectangle because of the parallel sides that support standing waves and it looks nice!
The length is the standard width of a sheet of plywood; 1m22cm.
Pure theoretical this would give a frequency resonance of 70Hz, way lower than the drivers can produce properly.

So, being a prototype and awaiting the build of four definitive boxes for home theatre, all input is greatly appreciated.
At the moment I do not have much time on my hands, working overtime and living alone, only lets me play around half a day at weekends.

My original thread about this:
Simple TL for cheap speaker to use as home cinema...
I had some questions in another thread, if anyone would like to have a look, they are related to this project too:
Extreme basket tricks

Thanks for watching!

[norman bates]

there were the pentachord speakers (2 way crossing to sub and a tall colum also crossing to a sub). Both used dual 50mm bandors per speaker I think.

Ideally, you'd want the line to resonate lower than the drivers to add bass down there.

I have a love/hate relationship with my dual 4" tang bands (see my avatar).
But it's doing better with 8" sealed run with it now.

Good luck with playing with them !!!!!!!!!!!!

Norman

[ßart West-VL.]

Hello Norman,

It seems to me you've changed your avatar since you posted that reply.

Where can I find more about those speakers?

I hope to find some time this week to play around, thanks!

[planet10]

Bart,

I love the shape

How do I put an expanding thumbnail-picture to my posts?!?

You need to use [img] not [image] tags

dave

[norman bates]

you may need a bit more cone area.



Norman

[Squeak]

Why not just use a tube, for the non prototype? It would save you a lot of cutting and assemblage problems, You'd just need a single short angle plate to mount the drivers on.

[ßart West-VL.]

Dave, thanks for the complement.

Norman, This TL needs to have three brothers and a center speaker, total of ten little drivers. But it's my goal to give them a break beneath 80Hz and cross to a decent sub. So this is mostly a HT setup but I know they will sound good for some occasional or background music too, as one box already sounded surprisingly good and nice without any filtering.

Squeak, I can't find a tube nice enough and/or rigid enough to use for this project. The finish would not be so nice because it can only be painted. A wooden box can just be varnished and show the grain. Also a pentagon is a total different thing to look at then a regular tube.
But you're right of course, it would be the same result with the only difficulty, being the baffle plates.

Am I correct to conclude that these five boxes can deliver 102dB if they're fed 100W in total? (efficiency is 82dB/W/m)
That would be 108dB at 300W, right?
These drivers can handle 30W nominal and 50W peak(music).
How much RMS would this be? I guess 15W.
Just trying to put a number on those maximum dB. For HT I think I can go with the music power handling of 50W, so this means they will be more then sufficient for HT I reckon.
A lot of people tell me 82dB/W/m is not enough for HT... I think it ís!

[Squeak]

I just think it's going to be a pain in the butt to get the joints to look good unless you are an excellent woodworker. If you absolutely want to have the wood look you could veneer the tube with very thin slices, otherwise there is plenty of options with wallpaper, paint, or fabric.

[planet10]

Originally Posted by Squeak

unless you are an excellent woodworker

Lots of excellent woodworkers here.

And you don't get good without practise. Nice to see something other than another monkey coffin.

dave

[AEIOU]

Originally Posted by Squeak

I just think it's going to be a pain in the butt to get the joints to look good unless you are an excellent woodworker. If you absolutely want to have the wood look you could veneer the tube with very thin slices, otherwise there is plenty of options with wallpaper, paint, or fabric.

MDF is easy to shape, fill and sand smooth, easier than plywood.