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Author
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Topic: That old saw: A7 port size
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Audio_by_Goodwill
Senior Hostboard Member
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posted May 04, 2008 01:44 PM
quote:
Originally posted by aeyb701:
In reading many old threads, as well as 40-plus year-old Altec literature on the topic there seems concensus that 75 square inches is an optimal port size for the 825 or 828 cabinet
for tuning at about 45 Hz.
Hmm, I wasn't aware that Altec literature specified a 75 square inch port. Can you post a link to what your reading? quote:
Why then did Altec make their ports on the order of 200 sq. inches?
Until I measured my port, I didn't realise how much bigger than 75, the factory ports are. I just calculated over 211.-------------------- Audio_by_Goodwill
Michigan, USA
Posts: 311 | From: Southwest Michigan | Registered: Nov 2004 | IP: Logged | Problem w/ Post?
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aeyb701
Senior Hostboard Member
Rate Member
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posted May 04, 2008 02:09 PM
Not that Altec directly specified 75 sq in for the A7-but I infer that from the graph in:http://www.lansingheritage.org/images/altec/plans/1968-enclosure/page04.jpg using 10 cu ft to be a ROUGH volume for the A7. I have a similar graph from ca. 1964 Altec speaker brochure copy I got on eBay-but no link. Meantime I covered half the port area from behind the cloth and am listening-initial impression is there's lower bass but maybe more peaky at other frequencies...I'll listen with it like that for a few days. Jon
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GM
Senior Hostboard Member
Member Rated:
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posted May 04, 2008 02:18 PM
Greets!75"^2 vents was chosen by various forum members based on their in-room listening experiences, though FWIW me and a few others prefer much lower tunings for HIFI apps. Altec OTOH tuned them for PA and/or cinema apps, which have a considerably different performance criteria that dictates a higher tuning, though it's preferable for a HIFI app if a sub system is used. GM -------------------- Loud Is Beautiful, If It's Clean
Posts: 1599 | From: Chamblee, Ga. | Registered: Dec 2002 | IP: Logged | Problem w/ Post?
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Richard C.
Senior Hostboard Member
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posted May 04, 2008 11:19 PM
Someday I am going to have to listen to some REAL VOT (A7 at least!) in a small room; say 15" x 20".I built a copy 30 years ago, and I didn't like it at all! It was fun to power it with a tiny transistor radio (9V), so loud that we couldn't hardly talk over it. The problem is I had to be 20' away to really appreciate it. I read that many people have them in "normal" sized rooms, but I just don't see how. I love both my 14's & my 19's, and I don't see how I could improve on them. BUT..., like I said, I would someday like to hear what you guys hear. I didn't play with the port size of my A7 copy at all, because the Altec plans didn't mention it. Richard C. [ May 04, 2008 11:25 PM: Message edited by: Richard C. ]
[ May 04, 2008 11:28 PM: Message edited by: Richard C. ]
-------------------- "In theory, there is no difference between theory and practice. But, in practice, there is."
Posts: 218 | From: Atlanta, GA | Registered: Dec 2002 | IP: Logged | Problem w/ Post?
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gamalot
Senior Hostboard Member
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posted May 06, 2008 08:44 PM
I'm with Richard and Altec Fan on this.My room is 15 X 18 and the A7 sounds horrible while the 19s and 15s work very nice either one at a time or both together. I do like some power going to the woofers so there is some flex and just never appreciated the A7s boxed in a small room with no room to breath. I can't explain why but when listening at lower volumes I like to have the 15s switched in but when I get cranking the 19s sound great alone. I always blamed my lack of appreciation of the A7s on the 511B horn and felt like I needed to be about 10 feet further away from it. Gary
Posts: 531 | From: Forestburgh, NY | Registered: Aug 2006 | IP: Logged | Problem w/ Post?
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posted May 04, 2008 12:13 PM
