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In my latest Model 19-like enclosure, I'm mounting a pair of reconed drivers with a Q of 0.45. VAS is 23 cubic ft. The FS is 21.5 Simulations show really nice response in 10 cubic feet sealed. My guess is that lining the enclosure walls is sufficient; no additional fill. Any input would be appreciated.
thanks
Les
Hi Les- if they aren't Altec speakers you'd be better off in a general audio forum. I wouldn't call those 416 clones based on just what you provided. Have you exercised them? The cones will break in and the specs change. You need to work with what the speakers are after break in, not what they are right after reconing.
I would just add that in my recent experience there is something to be said for firmly and uniformly attaching the damping material to the cabinet walls.Quote:
My guess is that lining the enclosure walls is sufficient
Hi Old Guy. These used to be 421's. I reconed them into 416. Did your brother not provide me with a 421 frame?
Hi Bowtie. Attaching the fiber glass firmly was where I was heading.
Quote:
Originally Posted by les winter
Hi Les,
- How are you measuring the TS parameters of these hybrids ?
- Who made those recone kits ?
cheers <> EarlK
Hi Earl.
I used the DATS system from Parts Express to make the measurements. I used the test box method for the Vas.
The recone kit came from the Speaker Exchange in Tampa.
My two cents. In my experience, if the woofer is being used up into the midrange, filling the box with absorbent material (I use Acousta-Stuf) helps eliminate any "boxy" sound. I also use acoustic foam (the 2" wedge sort) glued to the walls.
So they used the GPA kit listed on their website? Speaker Exchange | Altec 416-8A DIY Recone Kit
Full DATS specs please?
FWIW, I calculated the M-19?s net Vb as ~8.353487847 ft^3 using 416A/802.
Using the Margolis-Small T/S design routine, these specs equate to a ~0.8 Qtc using a minimal lining of 1? acoustic fiberglass insulation [AKA duct board], i.e. bottom, one side and back of the bass cab, though for the M19, mounting it at the top to isolate the horn cab as well as all sides inside it is what I?d try.
This is a slightly under-damped alignment though, which more often than not is acceptable to most, but I recommend experimenting with heavy stuffing to theoretically lower it down to as low as 0.7 Qtc and for folks like me that are willing to potentially trade some mid-bass ?slam? for a ?heart attack fast?/critically damped 0.5 Qtc [higher F3], experimenting with a ~aperiodic alignment [heavily stuffed/vented] may be worth the effort.
Note that the latter theoretically has much better power handling down below driver Fs, so the best option overall if pipe organ symphonies and/or movie LFE playback is desired.
GM
Quote:
Originally Posted by les winter
Sorry that wasn't clear from your post. They should be "similar" to 416's. The magnet difference will have an effect.
I think GM is on the right track. Go for best LF not best efficiency, as the back vented assembly should handle more power. Just crank them up.
HI GM.
I made the cabinet a little deeper to get close to 10 cubic feet. Here are the DATS t/s:
re 7.638
fs 21.5
qts .459
qes .496
qms 6.197
le .448
mms 151.9
vas 23.19
I measured the vas in a 3 cubic ft test box.
I do not know if the kit was sourced to Speaker Exchange from GPA or not.
Old Guy: I taped off the back vent; the recone kit came with a vented dust cover.
I wonder if you could find an expandable rubber plug at the hardwares store? I would think that tape would give and move a bit like a cone.Quote:
Originally Posted by les winter
That's very cool that you can buy all the stuff to put real cones in your self. With the spider pre attached. Anyone done this? I had all the parts from GPA, but sold them to one of our members some time ago. Along with the baskets. MattVandyke, not sure if he ever had them done or not.Quote:
Originally Posted by GM
ron
Ah- then forget what I said. My only experience with one set reconed this way, a solid cap was substituted.Quote:
Originally Posted by les winter
Maybe I'll put a piece of masonite. I'll report back. It will take some time. I'm tracking down a leak that's giving me a double hump impedance curve.
Thanks Les ,Quote:
Originally Posted by les winter
<> EarlK
Yes, I took the GPA speaker cones to a local speaker shop (JMAC) and had them done. They turned out well.Quote:
Originally Posted by RonSSS
Good deal. I did the same with my 8c's. JMAC has done Altecs since I was a kid, Ron's father owned the shop then.
Ron
OK, so I got one of these monsters put together. Stuffed pretty well, the Q comes in at 0.75. Sounds pretty good in my shop.
The GPA 902 is a little hot. I need to pad it down a bit. I figure an lpad at the tweeter to be 4 ohms in series and 8 ohms across to give me a 6 db loss. Any other suggestions?
thanks.
I'd go for a small amount of adjustment by using a variable resistor for the 4 ohms, or a fixed resistor in series with a variable resistor so you can tweak the horn level easily.
Quote:
Originally Posted by les winter
Normally a bypass cap around it is required to tonally balance it out in the extreme HF, though may be a waste in a shop app.
GM
Thanks, GM. These are destined to go to my living room. Any guidance on cap size?
Too many variables: attenuation amount, driver, diaphragm model/condition, how much capacitance in series, room conditions and last, but not least, personal preference; though 0.1-1.0 uF is where all but a few seem to wind up with and I've read where a few needed as high as 2.0 uF.
GM
Well, I'll give it a try. thanks again GM.
Les
Well this is the first of two. Still needs grills.
Looks nice. Have you fired it up?
Thank you.
Yes I have fired it up, but in my shop, with its concrete floors and other hard surfaces. So you cannot tell much. On the other hand, I've had these drivers and the crossovers in a smaller enclosure in my listening room and the results were pretty good.
I checked the cones. They are indeed marked "GPA"
In their new homes. I'm working on adjusting the controls. So far, they sound pretty fair.
looks like your already knocking the pictures off the wall.