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[Helge A Bentsen]

Does anyone here know the port frequency of JBL 4770 and 4748 cabinets?

I bought a stereo setup, looking at retrofitting and playing around with them to fill my spare time. Who knows, might end up with something I can use when we start working again. I got a HF driver and a pair of RCF 15" left over from another project that I'll start with for the tops, but I'd like to run some sims in Winisd to look at suitable drivers for the subs before I invest.

[David Morison]

I don't know, sorry, but generally for older JBL gear the forums at Lansing Heritage are often very good - if you haven't checked already it might be worth signing up there too.

http://audioheritage.org/vbulletin/

HTH,
David.

[Art Welter]

Does anyone here know the port frequency of JBL 4770 and 4748 cabinets?

Easiest way to find out is sweep a sine wave, excursion will be at minimum at Fb (tuning frequency).
Painting on a white dot, or a dot with a silver Sharpie makes it easier to see the cone movement.

[Riley Casey]

40hz if I remember correctly from the clones I built back in the day.

Does anyone here know the port frequency of JBL 4770 and 4748 cabinets?

I bought a stereo setup, looking at retrofitting and playing around with them to fill my spare time. Who knows, might end up with something I can use when we start working again. I got a HF driver and a pair of RCF 15" left over from another project that I'll start with for the tops, but I'd like to run some sims in Winisd to look at suitable drivers for the subs before I invest.

[Riley Casey]

BTW, booting the bottom octave in favor of subs and running 2220s instead of 2226s made for much better sounding boxes with a crossover at 1k into the HF driver.

[Helge A Bentsen]

BTW, booting the bottom octave in favor of subs and running 2220s instead of 2226s made for much better sounding boxes with a crossover at 1k into the HF driver.

Thanks.
I have a pair of BMS 4590 around that should fit on the 2380 horn.
Aiming for a crossover around 5-700hz, need to do some measurements and see what's possible.

[Helge A Bentsen]

Ok, so today I got around to do some measuring and playing around with them.

New 15" from RCF
BMS 4590 mid/hi
The last new in box JBL 2380A horn in Norway. (Me and the distributor hat to dig through his warehouse to find it).

Spent most of today measuring and testing them, initial results are pretty good. They sound a bit "old school", but they certainly have a character you don't find in smaller speakers. Listening to snare drums with a lot of low end in them are fun, they're suddenly hitting you in the chest again.

[Riley Casey]

Looks like you're gonna hafta fill those tweeter cut outs 

Be interesting to see the crossover output curves with the EQ

[Helge A Bentsen]

Looks like you're gonna hafta fill those tweeter cut outs 

Be interesting to see the crossover output curves with the EQ

Here you go

[Riley Casey]

Interesting... I see you have a tweeter band above 8k set up in the Lake but I don't see tweeters installed on the box. Whats up with that?

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