Project Finally under way

[4313B]

You might want to go with the newer LE14H-4 instead.

[timc]

How is price and availability for the Le14-h4 ?


-Tim

[4313B]

I'll send you a PM.

[pos]

Hi Tim,

Could it be due to small differences between the Clones i got from Matsj and the original H9800 Zilch did the measurements with?

I think that is a major part of the problem (maybe also having the horn sitting on top of an enclosure instead of mounted on a baffle?...)

I think our clones are different than the real H9800 in the throat.

I have attached a picture of the throat of my clone, and you can clearly see the difference with the picture of Widget's clone in from the project may blog:


Widget has integrated the metal plate inside the horn, whereas in our clones the mounting plate is simply added, with an additional cylindrical wooden throat. It is more like we are having a 3mm tube between the driver and the throat of the horn.
I think this is a problem when considering that the 2435 has a very short phase plug that was perfecly matched with the H9800 as can be seen here:
http://www.jbl.com/home/k2_story/k2_...draw_large.gif
as well as on a picture Rob posted of one of his 2435 without the mesh (I did not find the thread).

The second attached picture shows the situation we have on our mounting plates, compared to the correct approach that Widget used for Project May

I am thinking of removing this wooden part of the throat, and clamp the driver directly using speaker clamps (I am not really a fan of the metal mounting plate anyway, as it always needs adjustments to perfectly fit the aperture.

[timc]

Hi Pos. This clarified quite a lot.

Consering the Wooden tap you mount the driver to. Wont you loose low end response when shortening the length of the horn?

How will you center the driver without it?


-Tim

[pos]

Wont you loose low end response when shortening the length of the horn?

I hope that beside this wooden tap the rest of the horn geometry is correct. So if we remove it and find a way to correctly mount the driver we should have a correct H9800 clone, with the correct length.

How will you center the driver without it?

This is already quite difficult with the mounting plate (at least in my version), as the plate is quite loose around the driver.

Using speaker clamps the adjustment could at least be done directly with the driver mounted on the horn, by looking down the throat from the mouth of the horn.
And there is enough room to fix the clamps around the driver (this would be more difficult on a 435Be, but it also has 4 indentations for the screws that could be used to attach the clamp).

Another solution would be to use a very thin metal mounting plate and to reduce the length of the wooden tap, to minimize the problem.

The best solution would be to do as Widget did for project may:
http://www.audioheritage.org/html/pr...og/2004-05.htm
(21 may)
But this is quite difficult and risky...

What do you think?

[timc]

The thing Giskard did looks great, but i dare not try it without a spare horn.

If you remove the taps on your horn, let me know what you find. For now i dare not do anything more too them.


-Tim

[pos]

I will start a new thread to ask for advices on this issue

[timc]

Here is a graph of my measurements. I have no idea what happens above 10KHz. Could be just because i didn't use a proper setup for the Mic.

Note that the smoothening is only 1/12

And please have in mind that this is my first real project, ever. So I'm kind of a noob really.......

[Robh3606]

Do you have a measurement on the horn with no compensation, an impedance run on the horn and a schematic??

Rob

[timc]

I didn't take a measurement without the compensation. and nor did i do an impedance plot.

I have the schematics but not on the computer, i will post it tomorrow.

I used the filter zilch made for the H9800 and just altered some of the values. The layout is identical.


-Tim

[Robh3606]

I used the filter zilch made for the H9800 and just altered some of the values. The layout is identical.

Are you crossed over with an active crossover?? Did you measure both drivers?? How do they match up??

Rob

[timc]

Hi.

No. i use a 2. order passive butterworth.

15uf in series and 1mH in paralell if i recall corectly. The filter placed before the compensation network.

I might have to change the values, but i just tried a few combinations and it gave a nice higpass rolloff.

I did not measure both drivers this time around. I have done measurments on both with a Copland Drc205 at home earlier, and they look quite similar.


-Tim

[Earl K]

I used the filter zilch made for the H9800 and just altered some of the values. The layout is identical.

Tim ,

- Its best to avoid insulting those who have actually done the "heavy-lifting" work of making this driver/horn combo perform up to its potential .

- In my best recollection , Zilch merely implemented the compensation filter that Giskard gave to him ( & as originally presented by Greg Timbers ) .

- Giskard has done a lot of work making the combo work down to a 800 hz crossover point ( maybe even lower ) . He's posted those results ( as 4313B ) with response comparisons to the 476Be ( on the same horn ) . I believe he even posted schematics with these comparisons .

- Zilch ( by contrast ) is seemingly still enamoured with higher crossover points for these drivers ( @ 1.6 Khz ) and has ( as yet ) not grasped the necessary mechanics in forcing this horn/driver combo to perform below its' natural cutoff .
- ( Not to pick on Zilch since he has done a lot of good & public design work / but he's presently travelling a different road, compared to what you need to follow here ) .

<> cheers

[timc]

I see your point Earl, but remember that I am using the 2435hpl and not the 435Be. As i understand the 2435 don't like to be used as low as the 435, due to higher Fs. I do want the crossoverpoint as low as possible, but from what i have read it should be at minimum 1KHz for the 2435.

The filter posted by 4313B was also designed to work with active crossover, and he suggested that some tweaking would be needed with a passive system.

If you read Pos's post about the difference in the throat of the horn, you'll see that i have the same problem. I might remove this bit of the throat at a later point to see if i can get the same results as Widget and 4313B.

For now however ill just try to get them working decently.

Thanks for your input

-Tim


Edit: Now i see what you meant by insulting. The reason i mentionend Zilch in this sentence, was that he implemented an extra paralell notch, wich my horn really needed. I'm fully aware that this is GT's design and would of course not rob him of the honors. Nor 4313B that took the time to explain and post it.