2445/2380 + 2405 xover...HELP!

[SMKSoundPro]

Dear LH,

I am currently finishing my SR4733 or 4873 style of boxes for the club, and have run into a conundrum.

The box is two 2225's upto 800hz. Then 2445-16ohm on 2380 horn and into one 2402 bullet with 2405 diaphrams from 6k upto daylight.

Question: Am I correct in using the 3105 schematic?

Do I need to add bypass caps to the 3105?

Can anyone please advise me as to what passive crossover I need between this horn and tweet combo?

I am trying to order the parts and started to overthink the project, again.

Scott.

[subwoof]

the high pass part of the 3105 has your "cap" already so the bullets are safe.

If you are using old amplifiers or unstable processing / operators then adding a large cap on the splashers ( 2445's ) is recommended. Figure 30uf or better.

Don't overthink this too much...it's a club and all you need is hiss hiss boom boom..



sub

[SMKSoundPro]

Thanks for the reply.

I prefer the term: bump and sizzle.

I was really trying to make something similar to the 4873a box and take them with me when I leave this nightclub for SR uses.

Any other advice is welcome!

Scott.

[subwoof]

Some advice: when you put these baltic birch / ferrite magnets on the road you will soon need a third gonad.

Ebay is littered with Nd drivers ( 2452SL is the best ) and the occasional cone so you can easily take off 50lbs with the components that are in the newer SRX series....

The age of ferrite is over.

sub

[Baron030]

Hi Scott

In looking at the SR4733a network, JBL uses 0.01uF bypass caps.
So, if it were me, I would use some cheap Dayton Foil & Film loudspeaker bypass caps. For a night club system, going with really expensive audiophile grade bypass caps would most likely be just a waste of money. Just not enough bang for the buck.

And if I fully understand the physics of charge coupled caps, the real benefits are at lower volume levels, where the caps can create a significant amount of notch distortion. So, the benefits of going with charge coupled caps just does not out weigh the enormous additional cost in a night club system.

I am assuming that you’re bi-amplifying this system, and a protection cap for the 2445J is a must. But since you are highly experienced pro sound man, you already knew that. But, I can share one thing from my own limited experience. I found that if the protection cap value is too small it seems to de-couple the driver’s diaphragm from the amplifier. The high series reactance acts just like a series resistor greatly reducing the amplifier’s damping factor upon the driver. And it also seems to exaggerate the resonances in the horn. After reading a thread about damping resistors, I tried adding a 47 ohm resistor across my 2446H driver’s voice coil and I noticed an improvement in the sound. It sounded a lot less horny. But, I still felt that my choice of protection cap value was way too small at 25.8uF.

So, I next tried hard wiring my drivers directly to the amplifier’s outputs. Admittedly this is extremely dangerous to the life of a high frequency diaphragm. But the quality sound was absolutely phenomenal, talk about a night and day difference.
I have since gone back to using a protection cap now and it’s a lot safer to my diaphragms. But, I now use a much larger capacitance value and the sound quality is very nearly as good as the hard wiring method.

Since, you’re using a 16-ohm “J” diaphragm, I would recommend going with something around a 40uF value and also try adding one or two 47 ohm damping resistors across voice coil. The addition of damping resistors really seems to help.

Baron030

[SMKSoundPro]

Dear Baron,

Thank you for the reply and advise!

Yes, I am biamping these boxes and have protection caps. I am using 25uf. In my shop rig upstairs, I am not using protection caps and have noticed the difference.

In researching options yesterday, before replying, I "found" this:
http://www.audioheritage.org/vbullet...ead.php?t=6897

and this:
http://www.jblproservice.com/pdf/Sou...ries/4770A.pdf

I believe the 4770a crossover on the bottom of the first page is what I am looking for.

Can anyone please verify that I am correct here?
The only question i see is what is the value of some of the components?

Scott.

[SMKSoundPro]

[and this:
http://www.jblproservice.com/pdf/Sou...ries/4770A.pdf

I believe the 4770a crossover on the bottom of the first page is what I am looking for.

Can anyone please verify that I am correct here?
The only question i see is what is the value of some of the components?

Scott.[/quote]

Shameless Bump!

Scotty.

[Zilch]

I'm guessing that's 1.5 uF and 0.6 mH on the tweeters.

There's a rudimentary compensation filter (R1, C3) on the mid, but it's allowed to run full range; there's no lowpass. The tweeters are "supplemental."

Looks like R2 is 12 Ohms.

The two 2226H's are running full range.

These be "Rude" speakers....

[Baron030]

Hi Scott

Sorry, I did not get back to you sooner. Since, the printing on the JBL4770A Technical Manual was so hard to read. I tried down loading the JBL4750A Technical Manual which had printing that was a little more legible. Both products use the same HF components, so the crossover networks are interchangeable. The high pass section for the each of the 2404H drivers uses the same values as a bypassed 3105 network. (1.51uF series and 0.6mH shunt). The low pass section for the 2445J driver is very interesting. I am very surprised to see only a 20uF value for C2, which is the high pass protection cap. It would seem to me that a 40uF would have worked better.

R1, R2, and C3 make up an L-Pad that has some HF equalization boost.
R1 is 4.7 ohms, R2 is 12 ohms, and C3 is 4.7uF. Both resistors have a 20 watt rating.
An online L-Pad calculator shows that R1 and R2 resistors form a 4.5db attenuator and if my math is right C2 sees an impedance of 11.56 ohms. Since the 2445J/2380A sensitivity is 112db and the 2404 is only 105 db adding an L-Pad does make sense. At this point, I am not sure where the 4.7uF starts kicking in with its EQ.

Using an online Crossover network calculator, C2 acts like a 684Hz 6db/octive high pass filter on an 11.56 ohm load. And that does seem very odd to me, if the active crossover was set at 800Hz.

In researching the JBL/UREI 5235 active crossover, I could not find any information on 53-5334 crossover cards. But, I did turn up some information about the 51-5334 cards. It would appear that the JBL4770A uses a 1200Hz active crossover with Flat Front Bi-Radial EQ (FFBREQ). So, the C2 value may not be so weird after all. With active crossover adding some FFBREQ, I am surprised that C3 is being used to add even more EQ.

In any case, if you were to use an active crossover network with the N4770A passive crossover schematic. The 2445J driver would be used all the way out to 20 KHz. To lower the total harmonic distortion even further have you considered tri-amplifying your project? All you would need is a Crown D75a to power the bullets and you know it would sound so sweet…

Baron030

[Zilch]

In active biamp mode, 4770A calls for 40 uF and 3 uF protection caps for mid and tweet, respectively.

The FFBREQ cards are spec'd in one of the 523x manuals. I'd guess the 800 Hz one is correct, since that's the XO frequency on the 4770A tech sheet. That's what I'd use, in any case, until somebody showed me a credible rationale for doing otherwise.

Yes, you'll need L-pads on the tweets.

[Or free earplugs at the door.... ]

[SMKSoundPro]

HI guys,

In evaluating this speaker system's duties, I have taken Baron's advice and will triamp the box.

I will start with a dbx 234 and crown 1200 on the 2225's, crown mac 600 on the 2445/2380 somewhere around 800hz, and I have the choice of a crown D60 for the tweet or a bgw model 75. Both of these are 1 space small amps. I just don't have a d75 handy, yet.

I will use the 40uf cap and 3uf caps as protection. I will pink noise and adjust the xover up here in the shop beore they go downstairs for install.

(PS. We ALWAYS have free earplugs at the door!!)

I will use the dbx 120xp first to get to the crown mac 2400's for the 8 2241 subs, abd then into the dbx 234 for the triamp 4770a.

I did not have an 8 pin speakon, so I added another 4 pin. One for the lows(2225s) the other for the hi-mids.

I am getting closer! Thanks.

Gotta go home, now! pix to follow.

Scotty.

[Baron030]

Hi Scotty

Wow, this sounds like a really kick-butt system. And if I am reading this right, when you are finished with the 4770a boxes, you are going to be running a quad amplified system with the following in your night club:
8 - 2241 ULF drivers, 4 - 2225 LF drivers, 2 – 2445J/2380a HF drivers, and 2 - 2402 UHF drivers.

It’s a damn shame that Alaska is so far away from Chicago. I would love to hear the results.
And it really makes me wish I had the room for sub-woofers in my own apartment.
Wow, 8 – 2241s has got to have some serious “PUMP-IT-TUED” to it, no wimpy “GIRLY-MAN” bass here.

In looking at the specs on the 2380 horn and comparing it with my own experience using a 2446/2382 driver combination. I think you may find that 2445/2380 will sound better with the crossover set a little higher then 800Hz, say 1KHz. instead. And the reason why I say this is because of the impedance peak at about 750Hz. It suggests that the 2380 horn has a resonance at about 750Hz.
At one time, I tried using a 1KHz. crossover point with my 2382 horns and I had to switch to something higher crossover point or two reasons. One was the extreme roll-off that the 2382 has below 1KHz. It created a hole in the response that I could not correct for. And the second reason was that I could swear I could hear the 680Hz impedance peak that is found in the 2382 horn. I know these impedance peaks don’t show up in published frequency response curves as SPL peaks. But, I swear there is something going on at these impedance peak resonance frequencies.
And it was also about this same time, when I tried adding a 47ohm -12 watt damping resistor and I noticed an improvement. Seriously, try a 47ohm -12 watt damping resistor across your 2445 drivers voice coil. It will cut the size of that 750Hz. impedance peak down in half. And with the crossover set at 800Hz. you really should be able to hear the difference that the damping resistor makes.

And the only other advice I can suggest is to try using a larger protection cap value for the bullets. The N2400 crossover network uses a 6uF value, so I would think that a 6uF value would provide a high level of protection to the bullets and at the same time sound better then the smaller 3uF value.

I am looking forward to seeing lots of pictures. And please take some pictures of the night club where these boxes are going to be installed, as it is not likely that I will be going to Alaska anytime soon.

Baron030

[SMKSoundPro]

Actually,

2-2240, 2-2241 subs from 120hz down
4-2225 lowmids from 120 - 800hz
2- 2445/ 2380 horns from 800 - 7k
2 or 4 2402 w/2405 diaphrams from 7k up to daylight


per side.

These are the stacks I am building for each side of the stage in the big ballroom for the drag/variety show on Friday, and hiphop current dance music after and on Saturday night.

After learning so much here, I was determined to build a rig that the djs can't break so easily.

Scott.

[macaroonie]

You will be needing a peak limiter coz them boys are normally A Deaf and B stupid and C are behind the speakers and therefore cannot hear what is going on anyway.
Also in my very humble opinion you are way short in HF capacity.
Never underestimate the ability of drunk or chemically enhanced individuals to attempt to find 11 on the volume control.
As an example have a look at the HF provision in all the various Array and Vertec ( plus Nexo / Meyer etc etc. )
A humble Behringer Autocom for less than $100 will save your ass baby.
Speak to Scott Fitlin if you want the real deal here but you have been warned.
Speaking as one who learned by experience ---- Mac

[Baron030]

Hi Scott

Considering the size of your stacks, you better go with 4 instead of 2 bullets per side.
Rationalize it this way, what's another 5 lbs. tacked on to each of those already ball busting heavy 4770a boxes.
So, if you already have the bullets, then go head and use them.
And forget about my suggestion of using a crown D-75 amp.
In your case, you need something that has more juice.
Just go with an amplifier that can pump out about 40 watts of clean power into each one of those bullets and you will be one happy camper.
For a big ballroom like you are describing, there is no such thing as having too many drivers or too much power.

As Martha Steward says, "Max Headroom, it a good thing." or was it Matt Frewer that used to say that?

Baron030