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Thread: Altec A7-500 cabinet: Questions

  1. #1
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    Altec A7-500 cabinet: Questions

    I did a search and was not able to find the info, so please excuse me if this is re-hashing old stuff.

    I picked up a single Altec A7-500 cabinet. The woofer is a 416-8B (it may have been re-coned at some point) and the top section is a 511 horn with a 802-8T driver. The network is a N501-8A and appears untouched. The cabinet is the 28 (?) model and appears to be factory built with the 5/8 stock material (definitely needs some bracing).

    My questions.

    1) I can't find what the specified DCR reading for the 802 driver should be?

    2) The "horn" for the woofer seems short (I am used to folded horn designs). I can't imagine that it is providing much loading, certainly not at the lower end of the spectrum. Are there any graphs comparing the freq response of the stock "horn loaded" cabinet relative to a non-horn cabinet (comparable volume and venting)? IOW, how much is the horn loading contributing?

    3) I suspect that the vent size (about 200 sq inches) is too large. By this, I mean that a smaller vent would give better and deeper lows (which were probably not a concern for movie theaters back in the day). I am guessing a vent about 1/3 to 1/2 as large as the stock vent. I am guessing since I don't know the computation for vent size when the driver is also horn loaded.

    4) I notice that the cabinet could actually accomodate a much larger vent (up to 14 x 25 in). In other words, the cut out up front is much larger and a 5.5 inch board is slapped into place to leave about a 8.3 x 25 inch vent. Why was this done? Was it to allow for the cabinet to be tuned in the field, or to accomodate other drivers?

    Forgive all my questions, but this is becoming an interesting project.

    BTW, I do enjoy the dynamic sound of the cabinet. It could use a subwoofer (never my first choice), but I may first experiment with a smaller vent.

    Thanks,
    -Tom
    Last edited by withTarragon; 08-16-2010 at 07:42 AM. Reason: ...

  2. #2
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    Here is a link that has your Woofer and Dividing Network specs. http://www.altecpro.com/products/vin...x.htm#cabinets

    David

  3. #3
    Senior Member Sootshe's Avatar
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    1. 802's came in 8 & 16 ohm versions....presume yours would be 8 ohms.
    2. The horn loads from approx 200 Hz....the port loads to approx 50Hz.
    3. The vent is too large for home use & will benefit from being reduced. ( Search & you will find the required dimensions or just experiment with different sizes - do you have any test equipment?)
    4. The removable vent board was also designed to accommodate the HF horn. The horn could be placed in here & the cabinet then inverted.

    I'm not an expert on the finer points, but I'm sure others will chime in.
    Good listening.

  4. #4
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    - Panomaniac(s) thread called ;"My A7-500s, A Journey" offers great ( IMO ) documentation ( with observation ) to those who want to bring these theatre
    speakers into an acceptable HiFi mode .

    - You might want to post your questions into that thread at Hostboard ( since Pano doesn't post here at LHF ).

    <. cheers

    ps ; ( the dcr of the 802-8T will depend on the diaphragm that you find in the driver / you should have a 23744 or 34647 fram if it is still 8 ohms and OEM ) .
    - You could take it out ( if you're confident that you're experienced enough ) & then post a picture of the bottom-side .

  5. #5
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    Thanks guys!

    I am heistant to pull the diaphragm out, since I am not sure if there is some special proceedure about getting it back in register. I would hate to learn the hard way. Besides, I may not keep this cabinet (there was only one).

    I wanted to play around a bit with it, but there are too many speaker cabinets in my house already. If I start modifying the beast, then a potential buyer may not want a cabinet that has been "improved". I know that I would not.

    That is interesting about fitting the 511 horn into the vent.

    Thanks again,
    -Tom

  6. #6
    Senior Member Altec Best's Avatar
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    Thumbs up Earl Beat me too it AGAIN !!

    Quote Originally Posted by Earl K View Post
    - Panomaniac(s) thread called ;"My A7-500s, A Journey" offers great ( IMO ) documentation ( with observation ) to those who want to bring these theatre
    speakers into an acceptable HiFi mode .

    - You might want to post your questions into that thread at Hostboard ( since Pano doesn't post here at LHF ).

    <. cheers

    ps ; ( the dcr of the 802-8T will depend on the diaphragm that you find in the driver / you should have a 23744 or 34647 fram if it is still 8 ohms and OEM ) .
    - You could take it out ( if you're confident that you're experienced enough ) & then post a picture of the bottom-side .
    I was going to suggest the same, but Earl beat me to it.If I may add one other thing as far as I know the only difference that I know of between a 802-8T and an 802-8G is that the T stands for Theater and the "T" model uses a loading cap where the "G" just uses thick felt in the back cover cap.So if you find specs on the "G' or 033952,I think they should be very similar if not the same.And as you already surmised the vent needs to be reduced I think Panomaniac got his cabinet down to near 30 Hz.Posting at the Altec board or even sending him a PM should answer all your questions Nice score on the speaker.Regards ~ John
    "James B. Lansing" = Lansing Manufacturing ~ Altec Lansing ~ JBL

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