New Altec speaker boxes Part 2

[bigjunglejim]

Hi all, thanks for the input.

The 3/8" magnets sound cool but, I'm not sure they will hold the grills for the 620's... The 620 grills are going to be big and heavy. Regardless of the manufacturer's claim, I have my doubts.

I'm leaning towards using screws with "T" nuts or the "heavy duty" grill guides shown in the picture below.

As for the wire terminals, I think 5 way binding posts is the ticket. There are two I'm considering. Both are almost identical. They both can be set up for bi-amping or dual wires. See the pictures below.

Any recommendations as to what wires I should use inside the box between the speakers and the terminals? I was thinking of using 12 AWG speaker wire, ~100% oxygen-free with low capacitance. Would this be overkill? Do you think I should use the solid core light gauge wire that Altec used in the Model 19's?

Now for the insulation for the insides of the box. In most cases I've read you only have to line three sides of the box. I was thinking about doing both sides, top, bottom and back leaving only the baffle board without insulation. I'd like to hear from some of the speaker box gurus on this one. Also, what insulation should I use. Home Depot or something a little more trick. Please give me your advice on this and if you would, the reasoning behind your recommendations.

[gamalot]

The Ball & Cup fasteners work fine. I used them on my clone 19s with heavy grills but you will still want to glue both pieces into place.

I ordered some of the magnets and will try them on my next grills and let you know my thoughts on them with heavier grills.

The binding posts also look fine, I prefer the gold ones and all of these are available at PE.

As for insulation, the real 19 cabinets are covered on all interior surfaces except the baffle. They used a matting type that appears to be like fiberglass about 1" thick, pink and used some type of paint to blacken the stuff near the port.
You can quickly go broke with some of the available materials from PE or other suppliers and I am not sold that one is better then another so I can't add much here. I would like to locate a rolled material such as what Altec used that will work and is not fiberglass as I hate that stuff and the resulting itch.
If you have an upholstery shop near by you might find something suitable there at reasonable costs.

Gary

[Ronald Lee]

Originally posted by gamalot:

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As for insulation, the real 19 cabinets are covered on all interior surfaces except the baffle. They used a matting type that appears to be like fiberglass about 1" thick, pink and used some type of paint to blacken the stuff near the port.
You can quickly go broke with some of the available materials from PE or other suppliers and I am not sold that one is better then another so I can't add much here. I would like to locate a rolled material such as what Altec used that will work and is not fiberglass as I hate that stuff and the resulting itch.
If you have an upholstery shop near by you might find something suitable there at reasonable costs.

Gary

<font size="2" face="Verdana, Helvetica, sans-serif">According to my handy dandy Altec publication AL-6030-1 "LOUDSPEAKER ENCLOSUERE-Their Design and Use," pages 15 & 16:

The interior of the enclusure should have a partial or complete lining of acoustic damping material. Probably the most readily available satisfactory material is fiberglass. The Owens-Corning Fiberglass Corp manufactures a type called Aerocore, which is avialbe in many lumber and buidling supply store. Available in roll form, you need to buy only the amount required by your cabinet.

In a bass reflex enclosure the purpose of the damping material is to help break up standing waves, as well as provide proper damping of the low frequency loudspeaker. Altec recommneds that the back of the enclosure and any two adjacent sides be lined with the material. That would be either the top or bottom of the cabinet, one side and the back. Normally, material 1.5 to 2.0 inches thick will be suffice.
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[bfish]

FWIW, my luck with the 'pop-n-lok' plastics above is less than satisfactory, the slightest misalignment or excessive force breaks off the balls (ouch). You're left having to drill/dig out the remains.

The mag option is much better, and they're neo, meaning they never need recharged unless you burn the cabinets off them.

[bfish]

For anything else...

I gave at the office...

[gamalot]

I am just going by whats in them as they came from the factory and EVERY SURFACE IS COVERED, except the baffle in both boxes! It could be 1.5" thick.
There is no bracing at all and no support blocks along any of the seams. Material is particle board and vennered with walnut out and junk wood in. Two 1/4 X 20 carriage bolts hold the top to the bottom box. There might be some additional wood screws I will find as I strip it appart but I somehow doubt it.
The cabinet is well crafted but they stopped short of making it rigid and I suspect there is alot of resonance going on in here.

Gary

[bigjunglejim]

RKLee
Can you send me a copy of the Altec info you spoke of? "Altec publication AL-6030-1 "LOUDSPEAKER ENCLOSURE-Their Design and Use,"

Gary
I look forward to your report on using magnets to hold large grills.

Gary
The fiberglass in Model 19's is covered with a black fabric, not paint.

[Ronald Lee]

Originally posted by Jammin Jungle Jim:
RKLee
Can you send me a copy of the Altec info you spoke of? "Altec publication AL-6030-1 "LOUDSPEAKER ENCLOSURE-Their Design and Use,"

<font size="2" face="Verdana, Helvetica, sans-serif">Okay, let me work on that. I don't have a scanner, but my daughter does. It's a 30 page booklet.

Do we have a library somewhere here on this site. If so, and if this booklet is not there I would like contribute a scanned version. This booklet is pretty old, and the copyright is has probably expired.

[gamalot]

There has been no fabric on any of the 7 I have owned or in any that I have ever seen.
Just this black spray paint and only in the port corner to darken the appearance.


Gary

[endeeinn]

After going to all the trouble of using dense materials and braceing for the walls I would not want to use the plastic termial blocks shown above. The would vibrate like a drum negating all that was done to stiffen the cabinets. If you want to use them, I would recommend boxing them in from the inside with only the wire coming out and filling the cavity with insulating foam so isolate and deaden them. What I use are binding posts witht long studs and through mount them right to the rear panel. Just prior to placing the washer and nut on the inside I gave them a squirt of foam in the through hole to complete fill the gaps.