JBL 4 Way Build Questions

[NeverSatisfied]

I will throw an observation in here. When it come to loudspeakers, I have seen and heard creations that thumbs their noses at conventional wisdom and sounded really good. I have heard a speakers bass improve simply by removing 1/4 of the stuffing, conversely I have a friend, Bill who really stressed on all the details for driver specs, cabinet volumes, high quality crossover components , blah blah blah.
Sadly he built a beautiful pair of speakers that to my ears sounded lifeless and worse, fatiguing.
It took my buddy a year before he could finally admit they sounded like shit. He sold his very expensive Seas ( I think) drivers and gave the cabinets to another friend who threw a bunch of mismatched pioneer and JBL drivers in it and went active on the crossover. Holy shit, they sound great, took him a little while playing with the crossover but in his room with his equipment, they sound excellent.
Bill still hates the sight of those speakers but admits they sound fantastic.

 

[NeverSatisfied]

My quandary is with the box volume... To share or not to share... That is the question !

You have the drivers, the crossover and the amps….. I say build 3 boxes, one divided, one shared and one half the recommended volume but shared.
MDF is relatively cheap so your not out much and you might be surprised at which one sounds the best. Trust your ears because their your speakers.

 

[George S.]

Well, my mistake, JBL Lancers have a resonator, thought they had two big drivers.
Gut says they need a port if they share the same volume, or, their own dedicated volume if sealed.
I say run them sealed. Tune them if needed with poly fill.

 

[Mohawk]

I sent an email off to JBL .. Ill post what their tech dept has to say ....

On another note, does anyone have a PL200 or 300 series 2 amp in good shape that they would part with ?

 

[Gepetto]

I might have to disagree with Lee and Mark on this one. Since both drivers are being fed the exact same frequency range and are presumably wired together and fed by the same channel of the amp, then effectively they are one single driver. Sharing the same cabinet will allow them to couple together, thus evening out any small variances between the two speakers.

Shared, sealed enclosure is the way I do it if you have 2 identical drivers sharing the same frequency band and being driven by the same amp. The volume behind the drivers is the same on a per driver basis regardless if you subdivide the chamber or not. I have 2 - 15" drivers working in that mode. It works effectively.

 

[Mohawk]

Thanks Joe !
I was hoping you would read this thread !

 

[Gepetto]

Thanks Joe !
I was hoping you would read this thread !

I have been following along Matt, I enjoy the chatter on this forum.

I feel that there are many ways to a solution but wanted you to know that there is pretty much equivalence whether you join or do not join the cavities. Shared only works if you have identical drivers, driven by an identical source which seems to be your case.

 

[pennysdad]

That is pretty cool. I have never seen a 10" speaker with a sealed back like that. Nothing even similar.

It's actually 'vented'.

UPDATE: Correction. It's not. Sorry.



Some of the early JBL's had no vents. That's why they were so low power.
Once they stuck a hole in the back, handling went up considerably because air could get in to cool the voicecoil.

 

[pennysdad]

I think the two drivers in the Lancers shared the volume.

One was a Passive Radiator tho' wasn't it?

 

[pennysdad]

Re: using two 10"
As far as 43xx JBL Studio Monitors went, I don't think any had dual low mids.
The 4350 used a single 2123. The models below that [434x] used 2121.
These things were considered over the top loud with just one 10". Didn't need any more.
The 2123 is rated at 250 WRMS. Pro'ly 600 Watts Peak.
I hope you got a REALLY BIG room if you're seriously thinking of running TWO full stick.
That's a sh*tload of bass you're gonna need to catch up.
.... and HORNS to match that?????? OMG!!!!
Are you going to be wearing earplugs while you're listening to this? LOL.....
[don't get me wrong. I luv it and wish I was there....]

 

[AngrySailor]

Shared, sealed enclosure is the way I do it if you have 2 identical drivers sharing the same frequency band and being driven by the same amp. The volume behind the drivers is the same on a per driver basis regardless if you subdivide the chamber or not. I have 2 - 15" drivers working in that mode. It works effectively.

That’s how most of my cabinets are, shop subs included, 2 identical drivers in a shared cabinet. Here’s the house 3 ways, 2x15” shared volume, 6” sealed mid and a compression horn.

It's actually 'vented'.

View attachment 57847

Some of the early JBL's had no vents. That's why they were so low power.
Once they stuck a hole in the back, handling went up considerably because air could get in to cool the voicecoil.

Not sure if you’re thinking the “grille” on the back is a vent? It’s just the graphics on the sticker, there is no VC vent on these. They’re designed to be placed in a cabinet with other drivers (woofers) and be self isolated from that cabinets volume. Here’s a pic of an extra 6” from the house system, it’s totally sealed from the back.

 

[AngrySailor]

Well, my mistake, JBL Lancers have a resonator, thought they had two big drivers.
Gut says they need a port if they share the same volume, or, their own dedicated volume if sealed.
I say run them sealed. Tune them if needed with poly fill.

Tuning is really only effective around the resonant frequency, a ported cabinet will give you +3dB at/near the resonant frequency but fall off at a steeper rate BELOW its resonant frequency compared to a sealed cabinet. It also loses control of cone movement below resonance which can be a problem for subs in high power situations. Run a steep high pass filter set near resonance. For mids running 300 or 500hz and up, porting is not required and the box will have little effect on those higher frequencies. The speaker itself (T/S parameters) will have more effect in that the speaker is designed for midrange frequencies. I believe the JBL’s he’s using had a free air resonance of ~80hz, clearly not a suitable speaker designed for bass.

 

[pennysdad]

That’s how most of my cabinets are, shop subs included, 2 identical drivers in a shared cabinet. Here’s the house 3 ways, 2x15” shared volume, 6” sealed mid and a compression horn.



Not sure if you’re thinking the “grille” on the back is a vent? It’s just the graphics on the sticker, there is no VC vent on these. They’re designed to be placed in a cabinet with other drivers (woofers) and be self isolated from that cabinets volume. Here’s a pic of an extra 6” from the house system, it’s totally sealed from the back.

Yes, I got sucked in by the first pic. My mistake.
Your pic shows it much better.

 

[Mohawk]

Ok, So this is where I'm at this morning....

Redid a couple of box volume models and am going with a shared common volume..
Specs on the driver list .25 to .5 ft3

With the sim & 2 drivers it looks to me that around .3 ft3 is what I want the response to be.... (ish)



The box layout is just about done except for the wiring, poly fill and the top panel..

Btw... The reason for the extra big box is so it fits the exact dimensions of bass cabinets and the horns will rest on top !




Veneer and all the finish work is a little ways off yet !

 

[laatsch55]

Not your first wood project!!! Lookin good Matt!

 

[Mohawk]

Getting big sheets of veneer to do what you want takes a bit of practice !

 

[AngrySailor]

Ok, So this is where I'm at this morning....

Redid a couple of box volume models and am going with a shared common volume..
Specs on the driver list .25 to .5 ft3

With the sim & 2 drivers it looks to me that around .3 ft3 is what I want the response to be.... (ish)

View attachment 57890 View attachment 57882 View attachment 57883 View attachment 57889

The box layout is just about done except for the wiring, poly fill and the top panel..

Btw... The reason for the extra big box is so it fits the exact dimensions of bass cabinets and the horns will rest on top !


View attachment 57886 View attachment 57887 View attachment 57888

Veneer and all the finish work is a little ways off yet !

Nice! Just keep in mind that you’re only looking at 300hz and up maybe 500hz and up depending f on your crossover and also remember that all things the same, each additional driver adds ~3dB to you’re theoretically up 6dB left and right just by adding 2 drivers each side (sensitivity being the same).

 

[Mohawk]

That's one thought that takes me to lean towards series connection instead of wiring them in parallel.
My horns and tweeters are of the 16 ohm variety .....

 

[Gepetto]

Ok, So this is where I'm at this morning....

Redid a couple of box volume models and am going with a shared common volume..
Specs on the driver list .25 to .5 ft3

With the sim & 2 drivers it looks to me that around .3 ft3 is what I want the response to be.... (ish)

View attachment 57890 View attachment 57882 View attachment 57883 View attachment 57889

The box layout is just about done except for the wiring, poly fill and the top panel..

Btw... The reason for the extra big box is so it fits the exact dimensions of bass cabinets and the horns will rest on top !


View attachment 57886 View attachment 57887 View attachment 57888

Veneer and all the finish work is a little ways off yet !

Pretty work there Matt.

 

[NeverSatisfied]

Ok, So this is where I'm at this morning....

Redid a couple of box volume models and am going with a shared common volume..
Specs on the driver list .25 to .5 ft3

With the sim & 2 drivers it looks to me that around .3 ft3 is what I want the response to be.... (ish)

View attachment 57890 View attachment 57882 View attachment 57883 View attachment 57889

The box layout is just about done except for the wiring, poly fill and the top panel..

Btw... The reason for the extra big box is so it fits the exact dimensions of bass cabinets and the horns will rest on top !


View attachment 57886 View attachment 57887 View attachment 57888

Veneer and all the finish work is a little ways off yet !

Before adding the Polyfill I like to glue a piece of sound absorbing material like the stuff you find under automotive carpet (we used to call it Jute) in the center of every parallel wall. Even pieces of old pile carpet, anything that will adsorb sound that is a different density than the Polyfill.
I can't remember the exact science behind it, something to do with varying the speed of the reflecting waves between two parallel walls.
I can say from my own experience that it does have a positive affect and that the overall sound will be cleaner and more detailed.