JBL 2426 help
Ghost23
cd drivers. They are rated at 16Ohm each. I want to make a pair of top
boxes with them. I want to make a set of 8 ohm top boxes. I was told
that I could could put 8 ohm bullets in line with one of the JBL's to
achieve this. Is this right ? If so what sort of bullets would you
reccomend, what sort of x over should I use and is the 2426 cd driver
any good ?
Thank you.
Peter Larsen
> Hi, I hope someone here can help me. I have just found
> 2 x JBL2426J 1" cd drivers. They are rated at 16Ohm each.
Fine.
> I want to make a pair of top boxes with them. I want to
> make a set of 8 ohm top boxes.
You do not want to do this. Repeat until it sinks in.
> I was told that I could could put 8 ohm bullets in
> line with one of the JBL's to achieve this.
It was wise to verify a suggestion from that source. Always do that.
> Is this right ? If so what sort of bullets would you
> reccomend,
None whatsoever. First of all adding a cross-over and a supertweeter
will not change the impedance of them. Next putting a 16 Ohm
supertweeter - 2405 or whatever - in parallel with them will give you an
impedance of 8 ohms for a few seconds, until it is destroyed.
> what sort of x over should I use
First question is what horn to use, 2370A seems like a good bet. This
because JBL manufactures one compression driver for a 1 inch horn entry
and one horn with a 1 inch horn entry. Usually when a catalog looks like
that it will constitute A hint. Also all application note measurements
of the 2370 are made when fitted with that horn (and a cross-over, but
they don't say that, it is however obviuos from the curves!) and all
application note measurements of that horn are made when fitted with
that driver.
In the context of this newsgroup the lowest permissible cross-over
frequency is 1200 Hz, and it had better be no less than 18 dB pr.
octave. What is nice about that horn driver and horn combination is that
it actually goes all the way to 14 kHz and beyond. It may be a great
advantage to have a pre-set EQ for them, and it may be possible to
simply rely on the manufacturers data for the "midrange honk" around 3
kHz, about some 4 dB, enough to be offensive when combined with stage
microphones and their probable midrange enhancement. Do not fully
linearize them, they have a gentle downward slope, leave that be, just
do something to mimize the camel hump between 2 and 4 kHz.
> and is the 2426 cd driver any good?
Yes, they are probably very good, I haven't heard them, but they come
from a line of very good compressioon drivers. And be happy that they
are 16 Ohms, it makes matching levels to a low midrange loudspeaker a
lot easier in case of a passive cross-over and in case of an active
cross-over it reduces the overload risk. It also makes the in line
protection capacitor cheaper, polypropylene strongly recommeded. Shaun
and André may have additional comments.
Oh, be careful when you start playing with midrange drivers. Do not
listen without a bass unit being present and active. Otherwise you may
fail to realize just how loud it gets. That would be a grave error, horn
drivers can get plenty loud.
> Thank you.
Oh, jbl has a website, it is at http://www.jblpro.com. Their search
engine is screwy, but there is a page with "components".
--
*************************************************************
* This posting handcrafted by Peter Larsen, MCSE *
* My site is at: http://www.muyiovatki.dk *
* I subscribe to http://www.spamcop.net *
*************************************************************
Shaun
> Ghost23 wrote:
>
>> Hi, I hope someone here can help me. I have just found 2 x JBL2426J 1" cd
>> drivers. They are rated at 16Ohm each. I want to make a pair of top boxes
>> with them. I want to make a set of 8 ohm top boxes.
> Shaun and André may have additional comments.
You can design your own passive crossover for the 16 ohm HF + 8 ohm LF
drivers, which will effectively appear as an 8 ohm nominal load to your
power amp. There are many online sites and various speaker design software
applications which can assist you with the crossover design.
--
Shaun Wexler,
Hellsgate Sound
http://www.hellsgate-sound.com
mailto:sh...@hellsgate-sound.com
Ghost23
Peter Larsen wrote:
> Ghost23 wrote:
>
> > I want to make a pair of top boxes with them. I want to
> > make a set of 8 ohm top boxes.
>
> You do not want to do this. Repeat until it sinks in.
OK. I done that and understand.
>
> > I was told that I could could put 8 ohm bullets in
> > line with one of the JBL's to achieve this.
>
> It was wise to verify a suggestion from that source. Always do that.
>
> > Is this right ? If so what sort of bullets would you
> > reccomend,
>
> None whatsoever. First of all adding a cross-over and a supertweeter
> will not change the impedance of them. Next putting a 16 Ohm
> supertweeter - 2405 or whatever - in parallel with them will give you an
> impedance of 8 ohms for a few seconds, until it is destroyed.
!!! right not going to be doing that then.
> > what sort of x over should I use
>
> First question is what horn to use, 2370A seems like a good bet. This
> because JBL manufactures one compression driver for a 1 inch horn entry
> and one horn with a 1 inch horn entry. Usually when a catalog looks like
> that it will constitute A hint. Also all application note measurements
> of the 2370 are made when fitted with that horn (and a cross-over, but
> they don't say that, it is however obviuos from the curves!) and all
> application note measurements of that horn are made when fitted with
> that driver.
The 2370 horn flare is already fitted to them.
>
>
> In the context of this newsgroup the lowest permissible cross-over
> frequency is 1200 Hz, and it had better be no less than 18 dB pr.
> octave.
At the moment I am using a single Gauss HF4000. I get the best results
setting the x over freq at 3k. The mid sounds fairly limp if the x is set
lower. The Gauss has a strange metal front to it that looks like a heat sink
instead of a horn.
> What is nice about that horn driver and horn combination is that
> it actually goes all the way to 14 kHz and beyond. It may be a great
> advantage to have a pre-set EQ for them, and it may be possible to
> simply rely on the manufacturers data for the "midrange honk" around 3
> kHz, about some 4 dB, enough to be offensive when combined with stage
> microphones and their probable midrange enhancement. Do not fully
> linearize them, they have a gentle downward slope, leave that be, just
> do something to mimize the camel hump between 2 and 4 kHz.
> Oh, be careful when you start playing with midrange drivers. Do not
> listen without a bass unit being present and active. Otherwise you may
> fail to realize just how loud it gets. That would be a grave error, horn
> drivers can get plenty loud.
Thanks very much for your advice it's well apreciated. Youve set a few
things straight in my head and given me a bunch of other things to think
over.
The problem I have at the moment is the system is mono (becuase I only have
one top). I have a pair of folded bass horns each loaded with two 600w Beyma
15's. The mids have two Delta Pro 12's in each cabinet and I want to add the
JBL's so I can run in stereo. The bass bins and the mids boxes are all 4ohm.
I have read that if you are running more than 500w into a cabinet then you
shouldn't use a passive crossover, is this true ? if so this causes a
problem because the mids are 600w per box. I want to try and get all the
boxes running at the same ohmage. Any advice ?
Again thanks for your help.
Peter Larsen
[lotsa stuff snipp'd]
> At the moment I am using a single Gauss HF4000. I get the best
> results setting the x over freq at 3k. The mid sounds fairly
> limp if the x is set lower.
This one is under documented on the web, perhaps I should scan my old
1978 Gauss brochure and put it on my site. Anybody know if there are
anybody out there who will mind that? - from the lack of documentation
of any kind on the web it appears that the Gauss stuff is "abandonware"!
Anyway, if you have a midrange problem with this driver, then you have a
phasing problem. It has the rare property of actually being a usable
"upper unit" in a two-way when on the Gauss 4140 horn. This problem
makes excellent sense if you use it in some system in place of a JBL
driver, because JBL have never dared change the way the put color coding
on the driver terminals. If you plug and play another unit where a JBL
was, then you should wire it "the opposite polarity" unless of course
the JBL was wired correctly: red on amp to black on unit ....
This because JBL used "positive voltage moves voice coil towards the
magnet" from day one, and just about every other manufacturer known uses
"positive voltage moves voice coil away from the magnet, i. e. out of
the gap." It is important to remember that the standard refers to the
movement of the voice coil ALSO when the voice coil is on the rear side
of the magnet as it is in a compression driver.
Actual driver polarity in a multiway required testing, if all else
fails: listen for what sounds right and for what gives the smoothest
response when you move up and down in front of the speaker. Modest level
white noise is very useful for this. If in doubt measure, MLSSA can
provide a large amount of information, including just how far behind the
driver the apparent origin of sound is.
> The Gauss has a strange metal front to it that looks like
> a heat sink instead of a horn.
That must be some kind of acoustic lens and horn combination, is there
any identifying markings on it? - it might not be an alltogether bad
idea to use that pair - I assume that "single" refers to "single each
side" - as treble units above 3000 Hz for two reasons: they have a nice
dispersion and their horn may have insufficient length and mouth area to
really do a lot of work below say 2 kHz, many acoustic lense horns have
a mouth no larger than a coffee mug.
You might want to check the JBL Heritage site(s) recently referred to
here and try to see if you can find that horn lens combination in an old
catalog, 197x is a good guess. It might not be a JBL, but then it might
something that was - erm - strongly inspired by their designs.
If it is a squarish horn with a fairly large lens, kindy like a chevy
grille, then you have struck paydirt, those horns will do some 800 to
1200 Hz and they have a wonderful dispersion and airy softness to their
sound that works very well for short throw applications.
Acoustic lenses also have a few problems, it could be that it was not
just designer whims that did them in, perhaps time domain meausurement
of all the reflections and fuzzyness they must cause had something to do
with it. But they can be useful in getting sound almost around corners.
> The problem I have at the moment is the system is mono (becuase
> I only have one top).
AHA! .... a central cluster is not a bad approach, this new thing stereo
is much overrated as is the advantages of actually reducing the cutting
speed from 78 rmp, something that causes a massive loss of treble
headroom (Those that also read rec.audio.pro will understand this
digression ....). But it not always optimum to hang a single midrange
horn above the stage, even though some of the Montreux E-V setups I
recall seeing pictures of was not dissimilar.
> I have a pair of folded bass horns each loaded with two 600w Beyma
> 15's.
45 to 150 Hz; possibly to 250 if midrange has a front horn.
> The mids have two Delta Pro 12's in each cabinet
Is there a front horn? - if so 250 to 1200, if not 150 to 1500, they
will be fairly directional in the vertical plane in the upper range of
this, so you may want to make do with taking them to 1200. Powerhandling
probably says 1500, read on, more about that concern below.
> and I want to add the JBL's so I can run in stereo.
This makes good sense, SPL capability of the bands is reasonably well
matched, bass units must have 35 Hz 18 dB pr. octave highpass filter or
better to protect the rear suspension of the units from getting too
loose. If you have a 300 and a 500 watts amp, then the 500 watts amp
goes on the 12" units, not on the bass units, because the largest peak
power will be in the 12" units.
Clipping the amp that drives the midrange drivers is not a good idea,
they should have protection caps in series, something like some 30 to 15
microfarad polypropylene in series, smaller end of the range is better
protection, larger end of the range is less phase issues at cross-over.
This applies for a 16 Ohm unit, use half values for 8 Ohm. If you want
to listen for capacitor coloration then putting the capacitor in series
with a midrange or treble horn driver will teach you a lot about it.
Purpose of capacitors: to protect against the DC component of turn-off
turn-on thumps. Actually including them in the cross-over math allows
the use of 10 microfarad.
Note: according to Tom Brennans horn loudspeaker page the 2470 does not
really like too much LF, he had them making sounds of agony when trying
to cross them over with a 6 dB pr. octave filter. Mind you, that is home
hifi .... some things altec do not mind first order cross-overs when
used in the home, but we do not use first order crossovers in this
newsgroup.
> The bass bins and the mids boxes are all 4ohm.
OK, this means they have two units of 8 Ohm each. Something like say a
Yamaha P2200 on each box may do just fine, one loudspeaker unit on each
channel. Or a "big un" each band with one channel running each side.
> I have read that if you are running more than 500w into
> a cabinet then you shouldn't use a passive crossover,
> is this true?
No. If you run more than 5 watts average into a cabinet, then you
shouldn't use a passive crossover.
> if so this causes a problem because the mids are
> 600w per box. I want to try and get all the
> boxes running at the same ohmage. Any advice ?
Forget Ohms as a primary concern, ohms are not your problem, they are
just a spec to consider when selecting amplifiers. Mostly, but not
totally, you should also forget about passive cross-overs. This because
a high power passive cross-over with low insertion loss requires a lot
of copper, and copper is costly, and it also requires a fair amount of
polypropylene caps, those are also costly. An electronic crossover is
likely to be cheaper than a properly built passive high power
cross-over. That simple. An active cross-over also allows you to get by
with somewhat smaller amps, you may need more of them, but someone elses
second hand "too small for them" may do just fine, dual 300 watt amps
like the P2200 are likely to be "too small for them" nowadays, so they -
or similar - may be payable.
Other people here know more about what electronics that are de la mode
today. Specwise the Behringer CX3400 apppear to make good sense for your
use, in spite of it using what I consider to be crap opamps, this
because crap opamps actually matter a bit less in a cross-over. But 4580
is the kind of stuff that made me not even use my SV3800 until they were
replaced, so sorry was the sound. I suggest it because it just could
have a nice price and because it has the flexibility you need. There
might be points agains it in terms of "high end audio quality", but from
a totality viewpoint it and some amps that I likewise would not use for
home hifi may be a tremendous improvement at a modest cost.
To adjust an active cross-over by ear: start with the range that
contains 320 Hz. Add lower range if any until enough, add higher range
until enough, add highest range until enough. Start will all turned down
and then turn off and listen for continuity of cross-over.
> Again thanks for your help.
Don't just take my word for it, other people may have thought of things
that I have overlooked or noticed something I got wrong or
misunderstood. You might want to take a look at the bookstore on the AES
website ....
Kind regards
Peter Larsen