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Thread: might have lost my mind. thinking of building a7 cabinets

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    might have lost my mind. thinking of building a7 cabinets


    Phil-G's Avatar
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    might have lost my mind. thinking of building a7 cabinets

    I see them on ebay/craigslist from time to time. but fat chance on getting one here in s fla. so i've been looking at a7 plans and i know i could do it. (it might be easier than finishing my boat. maybe cheaper) if i can get a set of horns. it's on. battleship grey, no veneer, no bling, no foo foo. just brute force

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    Senior Hostboard Member cradeldorf's Avatar
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    Re: might have lost my mind. thinking of building a7 cabinet

    I wish you well.

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    Re: might have lost my mind. thinking of building a7 cabinet

    Eh hem...GO FOR IT...and post lots of pics

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    Senior Hostboard Member bowtie427ss's Avatar
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    Re: might have lost my mind. thinking of building a7 cabinet

    My advice is to build them all at the same time. If you're going to build a pair or a dozen, keep them both/all at the same stage of completion at all times.

    Buy extra stock for the curved horn flares, unless you excel at advanced trigonometry and can easily calculate the arc'd cut for the bottom of the flares where it meets the sloped horn bottom panel, you will cut a few before you get an acceptable fit. I used fir, it's much stronger/denser than the typical pine ply factory cabs were built from, i kerf'ed it on 1/2 inch centers to get smooth bends.

    One piece full back panels to give good access for further tweaks. I braced mine internally, i think the exterior braces are unsightly, and they can stand to lose some internal volume.

    Add a 3rd or even 3rd and 4th curved brace behind the flares.

    Make the motorboard/woofer mounting baffle the full width of the cabinet to seal off the horn flare cavities and add strength.

    Add copious amounts of HARDWOOD bracing internally to stiffen large panels.

    You can play with the port size and tuning until the cows come home. However, the reflex portion of the system will never make extended bass that can track the rest of the system in scale or dynamics. Corner loading or specific placement along with a tad of careful EQ can get them acceptable in larger/harder rooms. Proper subs shine a whole new light on them.

    Note the 1/4 ply added to the woofer mounting baffle is not necessary with an Altec woofer. I'm using a non-Altec woofer where the lack of gasket thickness would allow the forward edge of the cone to contact the baffle at the throat constraint on long excursions, hence the spacer.

    forums

    forums

    A7s816

    - - - Updated - - -

    For subs, i've built many of these. Some are still cruising around here in the northeast doing live sound 2 or 3 nights a week. The box is simple with internal volume and porting very similar to JBL 4719. Internal bracing is extensive.

    Originally loaded with 2241's, decided to try the MCM brand 18 inch woofer when they came on sale for 97 bucks each. Found them to be so close to the 2241 in this box that saving 200 bucks per driver was a no-brainer, and i'd consider using them again.

    picforjimcauseheslow
    Last edited by bowtie427ss; March 5th, 2013 at 09:50 AM.
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    might have lost my mind. thinking of building a7 cabinets


    alancohen's Avatar
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    Re: might have lost my mind. thinking of building a7 cabinet

    Quote Originally Posted by Phil-G View Post
    I see them on ebay/craigslist from time to time. but fat chance on getting one here in s fla. so i've been looking at a7 plans and i know i could do it. (it might be easier than finishing my boat. maybe cheaper) if i can get a set of horns. it's on. battleship grey, no veneer, no bling, no foo foo. just brute force
    You'd be surprised what you can find. I found a pair of empty cabs in NY A7 cabinets in NY, NY just after I decided, like you, to build them. For $162 I couldn't have purchased the materials.

    Correction: Audio_by_goodwill found them!! Stick around here. These guys are great at scouring the universe for Altec gear.
    Last edited by alancohen; March 5th, 2013 at 11:36 AM.

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    might have lost my mind. thinking of building a7 cabinets


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    Re: might have lost my mind. thinking of building a7 cabinet

    Last edited by Phil-G; March 7th, 2013 at 10:55 PM.

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    Senior Hostboard Member bowtie427ss's Avatar
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    Re: might have lost my mind. thinking of building a7 cabinet

    Quote Originally Posted by Phil-G View Post
    Actually they don't make them anymore.

    This is the woofer, same catalog number but now it has a smaller magnet and lower power handling. here also is a crappy photo of the catalog page of the ones i actually used, note the 100 0z magnet and 400/800 power handling:
    MCM Audio Select 18'' Die Cast Professional Woofer | 55-1875 (551875) | MCM Audio Select

    mcm18 zps047ef76c
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    might have lost my mind. thinking of building a7 cabinets


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    Re: might have lost my mind. thinking of building a7 cabinet

    i've ordered some stuff from mcm. but i usually just order small stuff, like semiconducters from mouser. so anyway i'm getting a little in the weeds with the altec 15/16s can you clue me in to a set that would work with (the set of horns i might have, if the guy sends them.) 902 811s? and how does the horn in the port thing work out? seems like it would save space.

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    Senior Hostboard Member bowtie427ss's Avatar
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    Re: might have lost my mind. thinking of building a7 cabinet

    If you don't need high power handling, 416-8B would be the woofer of choice whether vintage Altec or new GPA production. They would also play well in a conventional bass reflex box, and they play well high enough to use a 1200 hz XO.

    On a budget, it's still hard to beat the Altec 3156 OG mentioned. They're almost always available on ebay down around the hundred dollar mark, an Altec woofer for little more than a C note! New ones from GPA are 250 on ebay, and they have that wonderful new smell that will last several weeks. I wish i could afford some new cones myself, craving that smell, LOL!
    Not all vegetables make good leaders.

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    might have lost my mind. thinking of building a7 cabinets


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    Re: might have lost my mind. thinking of building a7 cabinet

    i'm not above spending the money on the gpa's. but i do love the vintage sound. so the 3156s might have to do. i know the 416s are rated for lower wattage but realisticaly how much sound do they put out?

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