[panky12345]

Originally Posted by jkdas

Sarkar! used magnifying glass?

Exactly I was wondering.... Kept staring at the pic, forget JBL, couldn't see any logo.

[low_bass_makker]

Originally Posted by vid6639

Lol. Those are JBL tweeters from the GT-5range of component spekers. These pods come with the box so you can either go for in door mounting or this pod on teh dash.

Yaar these are GT-5 components...



Could not find any logo there on the tweeter.

[gunbir]

Originally Posted by jkdas

Sarkar! used magnifying glass?

Originally Posted by panky12345

Exactly I was wondering.... Kept staring at the pic, forget JBL, couldn't see any logo.

Guys, there's a logo there and it looked like a JBL logo... like I said I could be wrong

[Vid6639]

Originally Posted by low_bass_makker

Yaar these are GT-5 components...

Attachment 45350

Could not find any logo there on the tweeter.

L_B_M the pic you have is of the other mounting in the box.

Can you do me a favour. Check out any pics on the forum from the JBL swifts. You can clearly see 2 pods on both sides of the dash.

I am dead sure these are the GT-5 pods. I got the same fitted in my friends car.

ps: If i find the pic I'll post it up.

[Vid6639]

Okay this is the best I could do:

Originally Posted by gunbir

Guys, there's a logo there and it looked like a JBL logo... like I said I could be wrong

There's no JBL logo but I'm sure the tweeters must have looked familiar to you since you guys had installed them in the twins.

[Bass&Trouble]

Originally Posted by gunbir

Guys, there's a logo there and it looked like a JBL logo... like I said I could be wrong

Thats the hole in the center of the phase plug.

[navin]

Originally Posted by Bass&Trouble

Thats the hole in the center of the phase plug.

now i'd really like to understand the physics of a hole in the center of a phase plug. It might work similarly as the old time lenses used on their compression horns. I'm sure Sam could provide some AES paper on this.

Lenard Audio - Education - Horns and Large Systems and Line Arrays.
http://www.jblpro.com/pub/technote/tn_v3n01.pdf

[Bass&Trouble]

Originally Posted by navin

now i'd really like to understand the physics of a hole in the center of a phase plug.

To be honest, me too.

Should pick up one of these tweets and measure them with and without the horn, with and without the opening etc. on MLSSA and see what the results are.

I would not be surprised if a lot of lesser reputed brands just throw one over the tweeter without any considerations.

[navin]

Originally Posted by Bass&Trouble

I would not be surprised if a lot of lesser reputed brands just throw one over the tweeter without any considerations.

The original time lens (the fin looking version) was approxmiated (the details are there in the AES papers of the late 70s and early 80s) to a little cover for a tweeter that coved about 50% of the tweeter's dome.

I saw them used widely when I was active and the last time a major speaker used is was the JBL 250Ti/260 SE. Today JBL's Control 1 (The 21st century's Pro III) still has the time lens. I could be wrong but I remember that JBL had some trouble compensating for the hair trigger ringing on their Ti dome (used in these speakers) and used the time lens to "mute" these effects.

They also tried to emboss various patterns on the Ti dome to stiffen it (the original dome material was so light that it flexed and had all sorts of IM distortion) as using a thicker material would have reduced Bl/Mms ratio even lower (it was low enough - for a tweeter- as it is). The advanced in materails technologies since have made all of this redundant - that is why I wonder why the Control 1 still carries it.

note: I was an active enthusiast in the 70s and 80s and maybe the early 90s. So my information is dated and given the state of what's left of my memory, not very reliable.

[greenhorn]

Originally Posted by Bass&Trouble

I would not be surprised if a lot of lesser reputed brands just throw one over the tweeter without any considerations.

I think most of the cheaper manufacturers put them there more for protection than anything else

[navin]

I think I got it!

The reason for the hole is that JBL does not need the time lens's acoustical properties any more. The phase plug/time lens on the GT5 tweeters is nothing more than a dome protector. the hole is to allow better radiation of the highs. Also since directivity is controlled by this "short horn" the GT5 tweeter would sound less bight than their previous verisons (with no hole).

B&T, Gunbir, Sam, guys you think my assumptions make any sense? Sam get back here! Stop fooling around in Berlin.

[low_bass_makker]

Originally Posted by vid6639

Okay this is the best I could do:

Who is this guy ? I think I have meet him before.

Like Navin Ji said that some one in Berlin.

[gunbir]

Originally Posted by vid6639

There's no JBL logo but I'm sure the tweeters must have looked familiar to you since you guys had installed them in the twins.

Ahh that's where I've seen them... I knew they looked familiar.

[navin]

Originally Posted by gunbir

Ahh that's where I've seen them... I knew they looked familiar.

Gunbir since you seen them upclose did you ascertain the reason behind them holes. I cant sleep. I need to know!

[iraghava]

Navin, does this pic help? Best I could find as of now.