modifications on a H9800 clone

[pos]

Hi,

I need some advice on an issue I have with a H9800 clone :
http://audioheritage.org/vbulletin/showpost.php?p=227331&postcount=34
So, what would you do?

[Hoerninger]

Hi,
... an issue I have with a H9800 clone

Is it an issue with shape or with frequency response?

Anyway I would not add unnecessary volume in front of the compression driver. The shorter the initial part of the horn the less influence on the frequency response in the highs.

Btw. the beginning part of the Everest II horn is shaped differently, just my observation.
____________
Peter

[pos]

Is it an issue with shape or with frequency response?Hi Peter,
For now it is a theoretical issue with the shape, as I don't have any precise frequency measurements.
But timc did try Zilch's network that worked properly on a real H9800 and Widget's clone, as well as on John W's "hand made" clones, and he has to do many modifications to that network to get a +-2.5db frequency response:
http://audioheritage.org/vbulletin/showpost.php?p=227321&postcount=30

According to Earl Geddes the throat is the most important part of the horn (he even removes the mesh and apply some modeling clay to smooth the transition between the driver and the horn).
And as the 2435 is quite special with regard to its phase plug I though it could be a real problem.

[Hoerninger]

Pos,
smooth transitions would be of benefit.

1. Recently I saw a comparison between an original JBL horn and another horn with a far more gentle transition at the throat. The up most frequency response was gentler too.

2. The "ring" at Mats horn gives extra volume but is of no other acoustical function. This deteriorates the frequency response.
Dr. Bruce Edgar made some thoughts about it:
http://www.volvotreter.de/downloads/Edgar-Monolith-Horn-02.jpg
which might be corresponding.

Hope this helps.
___________
Peter

[Guido]

Remove the tap and use a 1,5mm V2A plate for Driver mounting and you are done.
Do not worry too much about this. I did comparisons between an original JBL horn and a clone. I do not have them available for posting though. Don't think original JBL horns have perfect throats ;)

What becomes an issue is when you want to use an 1.4" driver on an 1.5" horn. Yes, this 0.1" really makes a difference!!
I realized this when testing NSD1480N drivers (1.4") and 2435 drivers (1.5").

[pos]

Thanks a lot for this advice Guido.

[pos]

Thanks Peter

I don't understand that picture tho :blink:
Could you please describe it?

[Hoerninger]

PM sent.
___________
Peter