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-   -   Needles with 2 FRS8 drivers (http://www.diyaudio.com/forums/full-range/86242-needles-2-frs8-drivers.html)

TDLofCC 10th September 2006 10:41 AM

Needles with 2 FRS8 drivers
 
Hi ... I recently made two needles with the Visaton FRS8 drivers.

I really love the sound these $10 drivers produce.
Now I wanted to make 4, for the 4.1 (sub is almost ready too ;)), but I found that my little daughter isn't that carefull ...

So I have 2 bookshelf speakers as rears, which will do for now.

I now have 2 FRS8 drivers left. And since I'm not really happy with the finish on the first Needles, I'd like to remake them.

Would it be possible to use 2 FRS8 drivers in 1 needle speaker ?
If so, what would I need to change ?

Any help would be greatly appreciated.

Cheers,
TDL.

Henkjan 10th September 2006 10:47 AM

my 1st respons would be double the depth of the speaker (so double cross section with same baffle) and filter the 2nd unit with a coil to make it a 1 way speaker.

TDLofCC 10th September 2006 11:02 AM

Ok ... thats out of the question I guess.

They're already 20cm long. Then they'd have to be 40cm long.

I've been searching some more, and I found some pictures of needles with two drivers, one in the front and one in the back. At the same heights ... but ... come to think of it ... they were twice the original height.

So, correct me if I'm wrong, but adding another driver means doubling something of the original design ... height, depth or lenght.

Is it possible to just make all the dimensions a bit bigger ?

On a sidenote ... would it be worth the effort ?

sreten 10th September 2006 11:17 AM

Hi,

You can mount them front and back as bipoles to use away from walls.

Theorectically you should double the internal cross sectional area, but
this depends on the CSA to driver CSA ratio you are already using, if
you are definetely rebuilding the cabs you can try 2 in your old cabs.

There is no reason why a bipole cannot be folded.
You could increase internal width to say 13cm and depth to say 30cm.

Effort ? 6dB more maximum output, 6dB more bass when used as
a bipole or 1.5way compared to the mid/treble level, 4 ohm load.

:)/sreten.

TDLofCC 10th September 2006 02:16 PM

Alright ... only problem is ... they are close to a wall next to the TV.

I'll just have to test them with the needles I got ;)

Nice new project ... and not that hard to make.

Just make another hole in the back and wire the driver to the existing terminal ... I think :rolleyes:

I'll keep you posted.

Henkjan 10th September 2006 02:23 PM

do you have the 4 or 8ohm version of the FRS8?

TDLofCC 10th September 2006 08:22 PM

8 ohm version. why ?

Henkjan 10th September 2006 08:30 PM

with 2 4ohm in paralel (so 2ohm load) your amp would probably not enjoy it....

Jim Griffin 10th September 2006 10:12 PM

Let me add to one of the statements that Sreten made. The statement was:

"Effort ? 6dB more maximum output, 6dB more bass when used as a bipole or 1.5way compared to the mid/treble level, 4 ohm load."

He is assuming two 8 ohms drivers which are connected in parallel in either a bipole or 1.5 way configuration. In the bass to mid region (typically from the baffle step compensation point and downward), you will have up to 6 dB more output vs. the mid/treble level as he says. Now 3 db of that 6 dB comes from the added acoustical efficiency (dual cones and sound field overlap) and 3 dB which comes from impedance sensitivity improvement (8 ohms to 4 ohms). Now above the BSC point any sensitivity improvement is solely due to impedance sensitivity increase. This results in 3 dB more sensitivity than a single driver monopulse raidator. In this case (above the BSC point) the sound fields radiated by the drivers on the front and rear of the bipole pair don't have any acoustical overlap so no acoustical efficiency increase results. Essentially, you get the same thing for the 1.5 way configuration you have the same output above the BSC point as the bipole assuming that you account for the baffle step with the 0.5 way driver.

TDLofCC 11th September 2006 08:43 AM

Wow ... that kinda of went OVER my head there ...

English is nog my first language ... so thats making it even harder ;)

So, if Henkjan would care to translate it to dutch ... I might be able to understand it ... ;)


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