Mod 14 Refurb

[Allen Crawford]

Hello, I am obviously new to this forum and delighted to be among experts and enthusiasts alike. Being previously persuaded by the likes of pioneer, bose,
mission, kenwood, etc...I have decided to go back to my desires of the 80's and refurb a recently acquired pair of ragged out mod 14's. Let me begin by stating that I am a retired member of the military and I have travelled abroad extensively and that is where I have gotten exposure to all the trinket novelty audio gear that I mentioned above. When shopping for a new stereo set in the 80's, I remember the audio dealer trying to introduce me to a pair of Santana two's but I snubbed the for a pair of Pioneer HPM 100's and a complete pioneer system. Wow! many years go by and I still pine for the old school! I have a pair of
jbl towers, bose am7 and am 9's, Adcom GFA 555, a POS kenwood preamp, two son minidisc
decks and 3 Nakamichi cassette decks. That is what I listen to in my den and where I relax the most after work. Now to the cruxt of why I posted and thus the heaing. I would like to restore my two model 14'a that I am using for nightstands and have been for the last 6 years:-). The driver facings are against the wall and the rear is facing outward. (What real abuse these poor speakers are taking!) Anyway, I am missing one of the mantaray horns and I am expecting one to arrive here any day. The crossovers seem to function correctly as far as the EQ"s are concerned but I haven't put the protection circuit to test. Both cast frame woofers are in dire need of reconing and I believe this form has been instrumental in pointing me in the right direction. My budget will allow for one woofer a month and the is after recovering from the expense of
the mantaray purchase. I guess the reconstruction of the cabinets (minor gash from a subwoofer drop on the top with a
little refinishing should round out the completion of the project. The grille covers are total **** and that can wait till July or so! My question is, Should I take my wife's advice and set a granite or slate slab on top the cabinets? Would this affect
the cabinet's resonance or take away from it's original tonality? Oh yeah,secondly,
is the cut-out porting sufficient for bass venting? Is there a formula used to improve the bas response by placing tubes or is all
this tubing business just voo-doo? Just some thoughts and any other help in the restoration phase would be most helpful. Again, glad to be here and I promise future posts would be less winded!:-)

Allen

[Jim Easley]

Allen,
The LF drivers can be re-foamed with kits that are available from Parts Express for around twenty bucks. Replacement grille cloth can be purchased from them as well. If you are very careful you can even re-use the original dustcaps with the help of a sharp exacto knife and a steady hand. I suggest using the original caps to avoid changing the driven mass of the cone assembly.
If the DIY route isn't appealing, there are many speaker repair shops that can do the job. If you suspect they need reconing, I would send them to Bill at Great Plains for a rebuild.
The crossover protection circuit on the 14's is powered from your amplifier output. The test button will not function until it is has sufficient input level from the amp. Basically the circuit is a relay that switches in a dropping resistor when it is trigered.
I don't think the "granite slab" would cause any problem but, the original oak finish looks pretty good on these cabinets and unless you have the granite handy, the cost could be much higher than a decent patch and refinish.
The bass port is correct for the cabinet. A change here would most likely result in lessened performance.

[GM]

>Should I take my wife's advice and set a granite or slate slab on top the cabinets? Would this affect the cabinet's resonance or take away from it's original tonality?
====
Yes, but that's a good thing if you're more interested in quality sound than 'vintage', IOW whatever tradeoffs Altec chose to sell speakers to the masses. The driver needs bracing/damping, the cab needs more bracing/damping, the horns need damping....... IMO, once reconed and broken in, get the driver specs and design/build a new cab.
====
>Oh yeah,secondly,
is the cut-out porting sufficient for bass venting? Is there a formula used to improve the bas response by placing tubes or is all
this tubing business just voo-doo?
====
Yes, if it yields the desired alignment at a low vent mach, then it works no different than a tube vent. Indeed, the shorter the vent the better since the longer the tube, the more its self generated harmonics affect the FR unless heavily damped, which can overdamp the cab's alignment/FR (may/may not be a good thing depending on the overall design).

No, no voodoo. Think of it this way, the BR cutout is a baffle thick tube of whatever equivalent diameter of its cross sectional area. You can use a box program to find a tube design that has the same alignment as the BR cutout.

GM