JBL 2435HPL's

[Earl K]

Do you agree that an L94 lens would not be appropriately applied in front of a constant directivity horn?

Yes I agree.

- JBLs' series of lens already does the HF spread within the horizontal plane ( somewhat like a CD horn does ). One wouldn't want to double up the 6db per octave ? lowpass that these things impose .

FWIW :

- JBLs' original series of drivers when mated to these throats had a bit more HF builtin ( not UHF ) before it was flattened out by the horizontal redistribution the lens imposed .

- A 2440 on a 2311 has quite a bit more measurable HF for the 2308 ( up to 9.5K ) to "flatten & distribute" when compared against the 2441/2311 combo.

[Ian Mackenzie]

Its been a long time since a studied wave guide and horn theory BUT I distinctly recall Dr Edgar and others advising against using a horn down to its wave length (or what ever) cut off and preferably 1 1/2 ~ 2 x for best performance. That might be acceptable for PA work but not HiFi.

Ian

[Earl K]

Its been a long time since a studied wave guide and horn theory BUT I distinctly recall Dr Edgar and others advising against using a horn down to its wave length (or what ever) cut off and preferably 1 1/2 ~ 2 x for best performance. That might be acceptable for PA work but not HiFi.

- Yeh that makes sonic sense excepting that part about PA vs HiFi - since power handling is quite compromised ( due to diaphragm unloading ) at the lower limits of a horns' loading capabilities ..

- That old rule of thumb that you are referring to certainly has its' applications. OTOH; In HiFi - RL impedance equalizers can be used to mitigate some of the deletrious effects caused by (classically defined) improper horn loading . JBLs' passive circuit designers are masters at seemingly bending these iconoclastic "rules" .

[speakerdave]

I don't think we can assume that 2435 (Be) and 2430 (Al) will play down to the same crossover point because the moving mass is probably different and will not have the same resonance point in the same volume. The Be 435 that is used down to 800 Hz in the 9800 has the larger back cavity, and I believe that is the reason.

David

[Mr. Widget]

Hello,
I won some brand new JBL 2435HPL's today!. I want some suggestions for a horn that will be suitable for an 800hz crossover point....

I suppose that the horn needs to work within the scale of the L220 also? If not there are several possibilities. If you are after great sound first and fitting it into the L220 second, I'd look at the Edgar salad bowls or perhaps even Johnny's thread on 1" Smith horns... You could certainly make a 1.5" version.

Widget

[Zilch]

24 dB filter at 500 Hz only:

[Zilch]

Giskard's earlier post on this subject:

http://audioheritage.org/vbulletin/s...age=13&p=44426

[Steve Gonzales]

I spyed these waveguides, they look more to my liking, I wonder if they could be lengthened to go down to 800hz. As you can see, I want the darn things to work in the L220's behind the L94, and you already KNOW I don't care if it sticks out the back!. According to another spec sheet, the 2435HPL is crossed at 1k in the Vertec array's they are installed in.

[Earl K]

Hi Zilch

- Nice RTA pics of the 2435 on your waveguides.

- FWIW ; I don't see anything that would lead me to believe those 2, 2435(s) are "off-spec" . Given the vertical scale you are using they are really quite linear between 1K and 8K . The @ 10 db per octave roll-off after 8K might be dissappointing - but even that slope is quite consistant between both units.

- I agree that the 2435 on your waveguides / with your crossover set to a 500 hz hipass / doesn't support much of anything below 1000hz.

- Now the question is really, why ? Here are a few suggestions for testing to narrow down the variables ;

(a) The 2435 needs to be tested on a horn that handily supports at least 600 hz to give the driver half a chance of loading the lower frequencies ( given the tight backcaps ) .

(b) The waveguides should also be tested/calibrated with a driver that is known to have significant reproduction down to 500 or 600 hz . That'll help determine where those waveguides' loading limits are .

(c) And last but not least ;

- The choice of a 500 hz hipass point for your pink noise test .

- This part of the test needs to be calibrated so that it's not a contributing variable . So :

(i) Plug a pink noise source into your electronic crossover .
(ii) Plug the hipass output of the utilyzed channel directly into one of the input chnls on your Behringer RTA/EQ .
(iii) Select this chnl as the "input source" while that EQ is in the RTA mode .
(iv) Get a working level of some observable pink noise .
(v) Assuming your crossover is variable in frequency , turn the frequency select knob to lower the frequency until 800 hz is about only .25 db lower than a similar measurement taken 1 octave above it . This is the point where the selected hipass point is starting to show a visable effect. ( ie some slope is manifesting itself ).

- I just did a calibration ( on a Behringer 2300 ) and found that a 250 hz point was about the highest acceptable point to test for 800 hz loading . Choosing any crossover point higher, was noticably attenuating 800 hz within the "stop-band" ( as seen on the RTAs' line input ) .


All the above variables can be contributing factors in the roll-off below 1000 hz. Each can "skew" conclusions about the 2435s ability to handle lower frequencies than 1000hz .

[Alex Lancaster]

I´ve never seen 2435's, except on photos, is it possible to make a spacer to increase the back chamber volume?

[Robh3606]

You are going to have a difficult time finding a horn to fit it the same space as the H94 that supports an 800Hz crossover point. They are only 5X10 maybe a bit larger. To support and 800Hz crossover point the horn has to load a good bit lower. As Earl points out the 2307 supports the wave length at 800Hz. That is 1.2K horn. You would be better off cutting a 2312 if you decide to go that way. I also would not do a reverse adaptor. Have it 1.5 at the flange the way the driver was designed to work. It makes no sense except to do it right or you won't get the benefits of your investment. Take a look at any of the 1k horns like the 2344 and the new PT with the same 100X100 coverage and they are almost the same size 12X12. There is no free lunch and size is going to limit your choices unless you drop it on top of are willing to do some extensize mods to the cabinets.


Rob

[4313B]

You'll need a complete network redesign as well. That part should actually be the most fun.

I'll leave "letting the cat out of the bag" with respect to the L220/L222 to others if they so choose. For better or for worse, I think things are going to start getting a wee bit more "diplomatic" around here though.

[Mr. Widget]

Well said Rob... unfortunately true 800Hz capable horns are not small. Look at the H9800 from the K2-S9800. It is 8" by 17" and is about as compact as is really possible. The 2312 is a compromise design that is really an anomaly. It does work, using the baffle to make it's mouth appear larger and is probably the only horn that will work with your aesthetic design. The new waveguides that Zilch and others have been looking at will fit in your cabinet depth wise, certainly wouldn't benefit from the lens and probably won't fit your baffle area... they also won't blend as well with the LE14A.

I know this is heresy coming from a horn advocate, but how about losing the horn and lens and using the large dome midrange from the XPL series? I bet it would be a dramatic improvement over the stock cone mid with lens setup. I am suggesting this not knowing the range that the dome works in or it's sensitivity, but Rob could chime in... he is very familiar with it.

Widget

[Zilch]

I'll leave "letting the cat out of the bag" with respect to the L220/L222 to others if they so choose.

What, that they're generally regarded as a "horror?"

Aready posted that.

[They make nice subs, tho....]

[Earl K]

Alex

I´ve never seen 2435's, except on photos, is it possible to make a spacer to increase the back chamber volume?

- It might be possible , though I don't have any of those drivers to check out that concept .
- I seem to remember someone saying that the backcap seemed to tightly house the diaphragm as if it was a one piece unit ( somewhat like the 2416 ) . Though maybe I hallucinated all that.

I think things are going to start getting a wee bit more "diplomatic" around here though.

- Any more diplomatic than it presently is and this place will turn into a shrine.