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Can you tell me what the metal insert / Plate is on the late model Ceramic magnet fame 414?
What is it's function, & how does it effect / impact the cone sound?
Why does the 414 have the large Dust / VC cover w/ the mesh screen?
The Ceramic loaded frames have the vent hole in them, which the Alnico's did not.
Jeff
If I have a 417, with a 414 Open mesh paper dome on it and the back or bottom of the Ceramic frame; magnet also has a the round Vent Hole...If both top and bottom of the pseaker are open, will that adversely effect the sound and low end frequencies?
If I have a 417, with a 414 Open mesh paper dome on it and the back or bottom of the Ceramic frame; magnet also has a the round Vent Hole...If both top and bottom of the speaker are open, will that adversely effect the sound and low end frequencies?Quote:
Originally Posted by 417 - Alnico
Can't comment about the metal plate, but the 414's VC is vented through the DC while the 417's vented out the rear, so if a vented DC is used on a 417, this then creates a semi-aperiodic vent that should affect both its 'tone' and LF performance, so would require a sealed cab of 'x' net Vb that would have to be arrived at empirically for best reflex performance. If used in an open back MI cab, then you'd just have to try it to see if it sounded 'good enough' to you.
Bottom line, it's probably best to plug up the rear vent when using a vented DC.
GM
Thanks!!!
Not to disagree at all, just a question...Quote:
Originally Posted by GM
Are you thinking 421? The 417 has the same mag as 414 AFAIK. The 417 has no vent in back and the aluminum dome....
But yes, as you say, vent one or the other way but not both.
Truth be told, I don't remember, just responded to what he wrote, so if he's wrong, I'm wrong. Don't recall having any hands on experience with ceramic 414s and the vast majority of my MI experience is with the 421 series, so what he wrote seemed reasonable...........
I'm surprised that any MI driver would be ventless though. I wouldn't think an aluminum DC would be enough.
GM
Actually I should expand since what I said was only true of Alnico, but AFAIK all 417 are Alnico.
The late 414 was ceramic, and had a metal plate inside to block the rear vent. That way it could use the standard 414 kit. Must be what he is referring to.
http://www.lansingheritage.org/image...-mi/page04.jpg
Don't think the 418 had a rear vent either. Was also Alnico/aluminum dome
Please pardon my ignorance but was there a functional reason in using an aluminum dust cap?Quote:
Originally Posted by GM
Did it significantly enhance heat dissipation?
I kind of thought some marketing guy requested them just to draw attention to the drivers on stage.
414 open dome, on a 417 kit, in a 12'' vented frame.Quote:
Originally Posted by 417 - Alnico
Thanks OG.
Some later 12"Creamics had vent Holes in the bottom;
maybe not older ones.
I have two sets, that are not white framed, 1987ish.
917 frames that came with 414's.
I have mentioned this many times without any confirmation, that the later, dark Gray framed Ferrite frames were used for the remaining available 12' spaeker made.
http://www.lansingheritage.org/image...hort/page4.jpg
Now it makes sense...a 414 ceramic with a 417 kit in it.
Not really gonna sound like a 417 since ceramic instead of Alnico. But prolly close.
This is very Un-Scientific...but, I have had about 9 Post 1972 White
Framed 417 frames reconed by Bill, and they all had tight Gaps...that is
if you gently checked with your hand .. thru-out the whole diamater
of the outer edge of the cone...I always found an area that sounded
like the cone would rub. Sometimes just a inch or less in one spot,
some times like a clock, @ the 3, 6, 9 o'clock positions. This never rubbed when used.
It is my opinion is that the Alnico Frames had tighter gaps than the later 917's. Tighter manufacturing tolerances on the old frames?
Maybe due to the Higher Gauss of the Ferrite magnet.
I also had a NOS OEM 417-D with Aluminum VC support
that was really tight, that Ted Weber was certain it was not a 417 Kit..It is.
No rub anywhere without a little extra movement.
I have had one set of light Black Ceramic frames re coned by Bill with his cones' and another set with 1 OEM NOS H kit and the other was a H-II kit.
None of these 4 kits show any sign of rubbing when pressure is exerted on them.
The 917, 1983 spec show that the SPL is 97...but the stats say 1W @ 5 cu'.
As always, I may be wrong but the 417's were tested @ 1 W @ 3 ft or
1 watt @ 1 Meter...quite a bit of difference.
So the 412, 414, 601 and all small Alnico driver 12'' frame, I believe could have 417's put in them and the 417 frame with it's larger mag could take the afforementioned models. Of course,
The aforementioned does not speak of under, over hung VC's, nor Gauss of smaller / larger Mags.
Now, if there were both, vented and unvented Dark Gray Framed 12'' Ceramic frames, I think they were of One VC Gap and one Ferrite sized magnet.
Sorry for my musing, postulating, rambling opinion.
As Always IMBW.
Jeff
I think I have read in Altec as well as JBL's literature, that he Alum DomeQuote:
Originally Posted by Altec19
besides being a type of heat sink...It also attached to the VC with Hard
adhesive to help extend the HF.
The aluminum dome will contribute some overtones. Altec did it early on some extended range speakers, by the 60's it had fallen out of favor except for MI speakers.