2451H with dual bolt patterns??

[sebackman]

Hi,

I’m using both 2451H and 2450SL on 233 horns in different speakers and they have different bolt patterns. However, I stumbled on these pictures and they seem to indicate that the 2451H does indeed have dual bolt patterns under the cover on the front.

Please note that the two pictures are from 2 pairs of 2451H drivers and one is using the large bolt pattern and the other picture the small pattern.

Can anybody share some light on this? How does the cover come off? Is it needed or can the drivers be safely used as on the picture?

This is of value to me as I’m investigating replacing my 2332 horns (dual bolt pattern drilled) with the more modern PT-F95HF waveguide which uses the smaller bolt pattern. It does normally not fit on the 2451h drivers.

Kind regards
//RoB

[Allanvh5150]

Hi Rob,

Not that I have seen these drivers in the flesh, but I think the outer holes are for the adapter to bolt onto. The 2450 and 2451 I think are the same driver but the 2451 has an adapter bolted on the front to make it 1.5" throat.

http://www.auduo-1.com/newgoods/I-J/...50J/2450J.html

Allan.

[subwoof]

that picture is of a 2450 ( 2" driver ) with the "snout" removed. NONE OF THE HOLES align with any horns..SOMEBODY has drilled extra holes on the inside diameter and tapped them..very very BRAVE indeed..

The outside holes are used for the 2450 ONLY.

I have had every possible combination of drivers here from that gen and I have done some re-drilling and tapping to make horns fit BUT used adapter plates...


btw the horn number is 2333 - always a 4 digit.


sub

BTW (II) the raised surface does NOT exist on the 2450SL, 2451, etc - ONLY the 2450..

[Allanvh5150]

Here is another driver that has 2 sets of extra holes.

http://www.audioheritage.org/vbullet...ID-2451-Driver

[subwoof]

There were a number of SR and specalized audio companies that took the snout off the 2450 driver to allow custom horns AND for them to fit into stage monitors..depth was the most critical issue back then and still is. At the time JBL didn't have a 1.5 variant into production ( that we could buy anyways )

DDS made a variant of their fiberglas 2-65 with a routed inside that the magnet fit nicely into - that round horn might of been from another company and it looks like there were 2 sets of holes for that configuration.

One version of a MEYER cabinet used a composite disk also routed and machined for the 2450 magnet but it changed to the 2451 as soon as they were released.

I have removed the gasket from the 2450 and there aren't any holes for mounting..

But there are another 4 of them in storage from a different deal SO maybe another look-see is in order.

sub

[Allanvh5150]

So are the 2450 and 2451 the same driver?

[subwoof]

of course not - one is 2" and the other 1.5" exit - if you look at other posts I have put up over the years you can see the differences but in this particular thread the discussion is about the top plate which is different for EACH of this magnet structure...

sub

[ivica]

of course not - one is 2" and the other 1.5" exit - if you look at other posts I have put up over the years you can see the differences but in this particular thread the discussion is about the top plate which is different for EACH of this magnet structure... sub

It seems to me that 2450-1.5 [usually 2450SL notation] looks very similar to the 2451 (neglecting the horn-screws holes position).
May be there are some internal differences in the construction, or may be phase-plug has different dome curvature......
On My experience, if the same diaphragm and the same horn is applied, both drivers have almost the same F/R response, and THD.
It would be interesting to find out why JBL has two almost identical drivers ( 2450-1.5 and 2451 ).

Regards
Ivica

[Allanvh5150]

I always thought both drivers were identical but the 2450 had an bolt on adapter to make it a 2"throat.

Allan.

[subwoof]

http://www.audioheritage.org/vbullet...hlight=drivers

[ivica]

http://www.audioheritage.org/vbullet...hlight=drivers

Hi subwoof,

Yes and nice figures You have presented here:

http://www.audioheritage.org/vbullet...l=1#post354706

and especially Your words:
....

And finally the nagging number FIASCO that JBL created with the 2450:

2450 = 2" exit driver with ribbed diaphram
2450SL = 1.5" driver with COATED, SMOOTH ( 2445 ) diaphram
2450SL-a = 1.5" driver with COATED, RIBBED ( 2450 ) diaphram

in the:
http://www.audioheritage.org/vbullet...l=1#post354709


Regards
Ivica

[more10]

However, I stumbled on these pictures and they seem to indicate that the 2451H does indeed have dual bolt patterns under the cover on the front.

I bought these drivers :-). Seller is Starlight. They have been selling a lot of Meyer ST412N lately:



, so these drivers might come from a Meyer cab.

[subwoof]

well your pictures seem to show cones..not drivers...??

[more10]

I was just trying to explain that the JBL drivers probably came from Meyer cabinets since the same company are selling Meyer cones as well.

[sebackman]

Thank you everyone for good and enlightened answers as always.

It was a friend of mine who bought them and when they were delivered it turned out that only one had dual bolt patterns and the other was plain 2451…but without the front cover plate

It appears that they came from some dismantled Mayer cab’s so they are most probably custom. -At least one of them.

MORE10, they came from the same place as your 10”’s.

He’s going back to the seller to at least get a pair that are the same. I will post if any additional info surfaces.

Kind regards
//RoB