Jbl Sub1500 15" Subwoofer 4 Ohm

[Mr. Widget]

Originally posted by MJC
Now I've just have to find some amps for the 1500 and build or buy the other electronics and I'm done.

You'll never be "done".

[MJC]

Originally posted by Mr. Widget
You'll never be "done".

How true!cool:
But it only took 25 years to move up to mirror imaged speakers-at Gisard's suggestion, about a year or so ago.:

[Frode]

Originally posted by Giskard
Hi MJC,


I'm actually leaning towards a Citation 7.4 - sized enclosure for my 1500 SUB drivers.

I can't find any info on this one, what's the size?

Frode

[Frode]

Originally posted by Giskard


3.4 cubic feet gross physical. Net effective can be adjusted with fiberglass fill.

Thanks! I've designed a box that is 2.6 cu.ft without driver/bracing. I think I'll stick with this.

Frode

[MJC]

Originally posted by Giskard
It often takes months of pondering for me to get around to cutting wood.

I know the feeling, I don't have a problem cutting wood. But I've been pondering for months, actually for about 2 years, what pre/pro I'm going to buy to upgrade my system.
The main L212s, now that they're mirrored, seem to produce a wall of sound like the Paragon. The speakers seem to disappear. Being that Greg's big design after the 212s, the 250s, were mirrored makes me wonder if marketing got their ugly say into how that L212s should be.
I always thought that the L212 was ahead of its time. And in a HT that had a 100" screen the front 3 speakers could be hung on the wall behind the screen. And all the others could also be mounted on the walls. Although I don't know if having the mains on the wall would be better or worse as far as listening to music. I've got the mains 3' away from the front wall and 4' from the side walls. The side channels are on the wall though, upside down with the 066 just above the top of the seat backs.

[maxwedge]

Originally posted by Giskard
Fortunately someone had the fortitude to force offset and mirrored systems such as the 4345 and 250Ti through the process I personally have no problem with building systems offset and mirrored. They sound better and they look just fine to me.

Why do offset drivers sound better? I've always thought it's better to line them up but I guess I thought wrong.

[MJC]

Originally posted by maxwedge
Why do offset drivers sound better? I've always thought it's better to line them up but I guess I thought wrong.

The drivers are lined up vertically. But their centerline is 2 " offset from the center of the baffle. Thus with the 16" wide baffle the "inside edges" are 6" from the center of the drivers and the outside is 10" from the center of the drivers.
So the part of the recording that is common to both channels, usually the singer's voice, rolls off the baffle to form a "center channel", that is seamless with the L/R channels, while still preserving the separation of all the instruments. And the result is instead of the L212s sounding like two separate speakers, it gives a wall of sound, with no holes, simular to the Paragon, which has the curved front that sprays the sound around. Which is what you hear when listening to a live concert.
I wish I could uplink the pics of the new speakers, but at this time I'm having problems with this computer. All of a sudden it won't reconize the digital camera, which has only been connected for 2 years!
I must be a stange duck, as far as speakers. I always like the L65s, but bought the L55s in '73 due to cost. But when I first heard the L1212s in '78, I thought "I've got to get those." So when the money showed itself in Jan. '79 the L1212s appeared in my living room. And I've never been sorry about spending that $1500 since, which was alot more money then than it is now.

[maxwedge]

Originally posted by MJC
And I've never been sorry about spending that $1500 since, which was alot more money then than it is now.

I'll say! Probably double! I guess that is why I've always bought componets and build my own.

Ok I think I got this mirror tech now....correct me if I'm wrong.
It's not really the fact that the mid driver is off center in relationship to the bass spk but more to do with the driver location on the baffel....it's closer to the inside edge of the baffel.

In the case of the Ti250 the spk's are all alined verticaly, on center, but it's the slopeing side edge of the cabinet that accomplishes the same effect. Correct?

[Mr. Widget]

Originally posted by MJC
And the result is instead of the L212s sounding like two separate speakers, it gives a wall of sound, with no holes, simular to the Paragon, which has the curved front that sprays the sound around. Which is what you hear when listening to a live concert.

Sounds like the old BOSE 901 line. Personally I don't like that smeared sound. If the system is set up properly you should only hear instruments and voices coming from the locations in space the engineer put them. Good speakers disappear and allow this to happen. I have a real problem with wide baffles and direct radiators. (with horns it is much less of a problem, but then they have other problems) I would suggest you put some highly absorbent material on both sides of the drivers on the front baffle. 1" fiberglass would work well but you may not want it exposed in your listening room, but just as an experiment if you put some fiberglass or Sonex on the baffle I think you would hear a further improvement.

Originally posted by maxwedge

In the case of the Ti250 the spk's are all alined verticaly, on center, but it's the slopeing side edge of the cabinet that accomplishes the same effect. Correct?

Yes.

Widget

[MJC]

Originally posted by Mr. Widget
Sounds like the old BOSE 901 line. Personally I don't like that smeared sound. If the system is set up properly you should only hear instruments and voices coming from the locations in space the engineer put them. Good speakers disappear and allow this to happen.Widget

I think you mis-read what I was saying. With the center of the drivers aligned with the center of the baffle, I could close my eyes and know right where the speakers were. With the drivers offset 2" from the center of the baffle the speakers disappear. The instruments are coming right from where they should. BUT the sound stage is full, it sounds as it would if you were in the Theater for The Performing Arts in Las Vegas, a place where I saw and heard many concerts in the '70's & 80's. And that theater was loaded with 125 Pro JBLs.
Don't EVER refer to Bose again on this JBL form! I wouldn't put Bose in my toilet!

[DavidF]

Originally posted by maxwedge
Why do offset drivers sound better? I've always thought it's better to line them up but I guess I thought wrong.

Offset of the drivers helps avoid equal path-lengths to the edges of baffle. As the sound waves hit the edges or corners, there is a tendency to bounce, or re-radiate the wave off of the edges and side panels of the enclosure. This can muck up the directional perspective and create peaks or nulls that effect the tonal balance, especially in the higher frequencies. The idea is to change the path length along the baffle so that none of the four paths to the baffle edge (box shape assumed) are equal and therefore avoid a compounding effect in a narrow range of frequencies or phase. As mentioned, other methods can be used to control or mitigate the diffraction problem. No doubt the L212’s wide baffle with a narrow side panels were purposely determined with radiation and diffraction issues in mind. There was no other reason to have the main systems so large for the drivers installed (other than they look impressive).

David F

[Mr. Widget]

Originally posted by MJC
I think you mis-read what I was saying. With the center of the drivers aligned with the center of the baffle, I could close my eyes and know right where the speakers were. With the drivers offset 2" from the center of the baffle the speakers disappear....I wouldn't put Bose in my toilet!...

I guess I did. I still suggest you try treating those baffles as even more magic is likely to occur.

Widget


Bose Not even for the Tidy Bowl man!

[MJC]

[QUOTE]Originally posted by Mr. Widget
[B]I guess I did. I still suggest you try treating those baffles as even more magic is likely to occur.

Widget


The sub-enclosures for the 112a and LE5-9 are stuffed to the max with insulation. That is how the original pair are also, so the drivers are totally encased with stuffing.

But back to the topic of this thread, the 1500 can be put into as small as1.5cuft and a box at 4.0cuft will get to what the old B212 was and then some. I don't have BB pro, but if my numbers are right with the info I have I need to add a filter(Zobel Network) with a 4~5 ohm resistor and a 30uF cap. I was thinking of using the 540w plate amp, but some were saying the 1000w plate amp. Thats only 200w over the rated capacity of the 1500. And those amps also have EQ if I wanted to use it.

[Mr. Widget]

I was talking about covering the front surface, the side you see and listen to, of the baffle with Sonex or fiberglass to make the large baffle acoustically disappear. I would think you could still get the grill over it.

For the Sub, if you are going to use them for HT, the bigger amp would be my choice. I wonder about those plate amps though... have you heard them? Will they take them back if you aren't satisfied?

Widget

[MJC]

Originally posted by Mr. Widget
I was talking about covering the front surface, the side you see and listen to, of the baffle with Sonex or fiberglass to make the large baffle acoustically disappear. I would think you could still get the grill over it.

For the Sub, if you are going to use them for HT, the bigger amp would be my choice. I wonder about those plate amps though... have you heard them? Will they take them back if you aren't satisfied?

Widget

How things have changed over the decades. all speakers had wide baffles and now with HT most towers have smaller, multiple LF drivers set in baffles just barely wide enough.
I haven't built any grills yet for the new L212 towers. I've finished them the way I have always thought the L212s should have been done. I've veneered all the exposed surfaces instead of black paint.
If JBL had contructed the cabinets as I have, square cut all pieces instead of miter cuts, then they could have made the baffles with offset drivers and then there would be no inside or outside to the baffles. So one baffle would work for both L/R. And then the veneer would cover the joints. And considering that the L212s listed @ $2000 in '77 the cabinets should have been veneered to match the bases.
I've never heard those PE plate amps, but they claim that they're class AB output. I have bought speakers from PE and have sent them back. PE does have the 1000w amp in stock, but they're out of the 540w amp until mid April.