Re: Altec 902 and 416-8C - X-Over freq?
Quote:
Originally Posted by
bowtie427ss
Well I finally got to measure the units and indeed they are not an inch but 7/8th of an inch.
And here is the other conundrum - the 811 Horns that they mate with are 1inch diameter at the throat - meaning they are a mismatch.
The conundrum being that they were clearly or seemingly clearly factory set like this - the gaskets etc gave me the impression they had not been separated prior to my taking them apart......
So I have a mismatched setup and I am now pretty stumped - this may be the end of the road for the Altecs unless I resort to machining options...
Or can folks confirm the existance of 7/8" 811 sectoral horns?
Hmmmm :(
Winders
Re: Altec 902 and 416-8C - X-Over freq?
Quote:
the 811 Horns that they mate with are 1inch diameter at the throat - meaning they are a mismatch.
This may be the lesser of two evils. I think where you can really have the potential for audible problems is if the driver were 1 inch and the horn 7/8. That would leave a small flat face that could reflect energy back into the driver throat.
In your situation it may be possible to "smooth" that transition by just adding a second gasket and carefully sanding/cutting the gaskets to more or less continue the flare rate of both throats.
Re: Altec 902 and 416-8C - X-Over freq?
Quote:
Originally Posted by
bowtie427ss
This may be the lesser of two evils. I think where you can really have the potential for audible problems is if the driver were 1 inch and the horn 7/8. That would leave a small flat face that could reflect energy back into the driver throat.
In your situation it may be possible to "smooth" that transition by just adding a second gasket and carefully sanding/cutting the gaskets to more or less continue the flare rate of both throats.
I'll look into this - it might be worth machining up a phenolic adaptor say 1/4" thick - the studs seem long enough....
But I have no idea what this means to the FR and its still a cobbled system - has anyone got a pair of 811B Sectoral horns with 7/8 inch throats that they want to sell?
Cheers
Winders
Re: Altec 902 and 416-8C - X-Over freq?
Quote:
Originally Posted by
bowtie427ss
This may be the lesser of two evils. I think where you can really have the potential for audible problems is if the driver were 1 inch and the horn 7/8. That would leave a small flat face that could reflect energy back into the driver throat.
.
Ditto!!! Not only run the risk of audible problems but the reflected energy puts an undo strain on your diaghram from the reverberating sound pressure's back into the diaghram.And will eventually cause the fragile diaghram to fail.
Re: Altec 902 and 416-8C - X-Over freq?
Quote:
Originally Posted by
Altec Best
Ditto!!! Not only run the risk of audible problems but the reflected energy puts an undo strain on your diaghram from the reverberating sound pressure's back into the diaghram.And will eventually cause the fragile diaghram to fail.
Understood... better in that there is no reflected energy going 7/8ths to 1" but still a significant discontinuity and a discontinuity in the throat of any horn is a no no.....
Need to ascertain how many systems are thus afflicted and still yet to see an Altec 7/8ths adaptor or a horn with a 7/8ths throat!
I cannot find any Altec literature referring to such a beast...
Seems I might be in the market for a 1" pair of Ferrite 902-8A's (if they exist) - Diaphragms are not critical as I have a brand new pair from GPA...
Or I am looking for a pair of 811's with 7/8ths throat - again if they exist..would Altec make a horn in two throat sizes with same part number...
Would Altec make two types of 902-8As with same part number - this whole thing makes no sense....
Or I make a proper adaptor out of fibreglass resin .... to mate 7/8ths to 1".
Hmmm... weird that Altec did this....
Winders
Re: Altec 902 and 416-8C - X-Over freq?
Quote:
Need to ascertain how many systems are thus afflicted and still yet to see an Altec 7/8ths adaptor or a horn with a 7/8ths throat!
I cannot find any Altec literature referring to such a beast...
TA DA!!!!!
MR931 HORN
Interestingly, while the GPA website says their current model of this horn is designed for drivers with a 1 inch throat aperture, their data sheet specifies a 7/8 throat on the horn. My guess would be the website gives just a generalization to avoid confusion. Maybe TWW can clarify for us.
FWIW, my 9842 902's/MR931's, and factory gaskets are all precisely mated at 7/8".
Quote:
Would Altec make two types of 902-8As with same part number - this whole thing makes no sense....
I can only guess, but my suspicion is that early 902's were probably 1 inch, but as the Mantaray horns began to replace the 811 and 511 sectorals they were revised to a 7/8 throat while the more industrial aimed 908's and 909's retained a 1 inch opening............ purely a guess on my part. This is another chapter that should be covered in Bill H's book when he writes it.
Re: Altec 902 and 416-8C - X-Over freq?
Quote:
Originally Posted by
bowtie427ss
TA DA!!!!!
MR931 HORN
Interestingly, while the GPA website says their current model of this horn is designed for drivers with a 1 inch throat aperture, their data sheet specifies a 7/8 throat on the horn. My guess would be the website gives just a generalization to avoid confusion. Maybe TWW can clarify for us.
FWIW, my 9842 902's/MR931's, and factory gaskets are all precisely mated at 7/8".
I can only guess, but my suspicion is that early 902's were probably 1 inch, but as the Mantaray horns began to replace the 811 and 511 sectorals they were revised to a 7/8 throat while the more industrial aimed 908's and 909's retained a 1 inch opening............ purely a guess on my part. This is another chapter that should be covered in Bill H's book when he writes it.
Again you provide excellent info thanks - have to admit I was looking in the sectoral horn '511/811 arena' for a 7/8ths interface as I am making an A7 replica...
I guess given that I have expended so much money and time already that I should simply make an adaptor - next will be to try and ascertain the curve.....
Thanks again - most helpful!
Winders
Re: Altec 902 and 416-8C - X-Over freq?
Yes I think all Altec 811B's and 511B's are 1" throat aperature. the 7/8" is for the newer Mantarays and newer 902's to name a couple, Bowtie's right on.:Nodding:
Re: Altec 902 and 416-8C - X-Over freq?
Quote:
Originally Posted by bowtie427ss
I can only guess, but my suspicion is that early 902's were probably 1 inch, but as the Mantaray horns began to replace the 811 and 511 sectorals they were revised to a 7/8 throat while the more industrial aimed 908's and 909's retained a 1 inch opening............ purely a guess on my part.
I have a 908-8A here ( serial # 00915 ) that sports a 7/8" exit .
That supports your contention that you're guessing about the above .
<> cheers
ps ; not that it matters , nobody's going to lose an eye over this 1/8" difference . :p
Re: Altec 902 and 416-8C - X-Over freq?
Quote:
Originally Posted by
Earl K
ps ; not that it matters , nobody's going to lose an eye over this 1/8" difference . :p
On the contrary I think if thats the case then they 'cocked' it up and 1/8th certainly makes a difference especially as a discontinuity at the throat, as we all know, is not good.
They went to great lengths to make adaptors for 1.4" to 1" for this reason.
Now how much it matters well who knows.....
Winders
