My turn...A7 restore...

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Originally Posted by analog addict

One of the things I'm trying to keep in mind is the amount of "unsprung" weight I'm adding to these boxes. I still have some structural additions to make....

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Your cabinets have a suspension?

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Originally Posted by analog addict

As far as the port boards, I have them, and need to finish them up, along with the backs. I was also thinking of making some sort of sliding door for the port as to have a variable tuning device for them. Anyone ever try that approach?

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I've got one of mine mocked up (sp?) that way presently. Just my existing ~3" full width slot port (inside cab) and a form-fitting piece of MDF/melamine (whatever it is). I started a little large, then slimmed it kerf by kerf until it press-fit and stayed put pretty well. A run of ele tape around the perimeter helps it be just wide enough to stay put, but still adjust.

As GM mentioned, this is just temporary for tuning. I got down to 35hz or so with 1" full width. I plan to post pics and results, but life is in the way of play, as usual.

* I did post measurements of the original ~3" full width, but I'll be ***** if I can find the post now.

Next I am moving onto sealing it, and using ~3" length (to be adjustable during testing) of 3" dia PVC.
The impedance graph suggests to me that this is the next logical step (for me).
(i.e. the lower freq impedance bump is larger than the higher hump... )

Hmm ~28"^2 vent area x 5/8", so you need to start with a 6" dia. pipe..........

GM

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Originally Posted by Audio_by_Goodwill

Your cabinets have a suspension?

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Heh, right now they're on 4 wheels. Suspension is pretty rudimentary though....

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Originally Posted by GM

Hmm ~28"^2 vent area x 5/8", so you need to start with a 6" dia. pipe..........GM

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Yup, noted - and you'd suggested similar in a previous thread, thanks.
Alas, the hardware for the larger diameters was not as easy to come by, so I was going to start with 1 longer 3" dia and adjust the length to see how it goes.
Also intending to see how low it can be pushed. MFR if that's the applicable term.

AA, you are doing a fine job.

I used two 4 inch diameter. The pipe is a close fit in the flange. I wrapped a piece of masking tape around the joint on the inner side of the flange to make the tube easy to remove in order to trial different tube lengths.

Unfortunately my project stalled at the pictured stage late last year but I am now looking to getting my old amps fit for service so the project can be completed.

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Originally Posted by gearfreak

Yup, noted - and you'd suggested similar in a previous thread, thanks.
Alas, the hardware for the larger diameters was not as easy to come by, so I was going to start with 1 longer 3" dia and adjust the length to see how it goes.
Also intending to see how low it can be pushed. MFR if that's the applicable term.

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If you are getting only 3" pipes, then instead of using only one piece, it will be better to use four pcs of 3" dia pipes. It will do the job far better as the overall x-sectional area will be closer to the LF driver piston area. My sim-ing with bassboxpro puts the length at 2.45" for each pipe for 32Hz, while taking the internal volume at 11.50 cu-ft. It can be fine tuned a bit though in length.

Good luck to your A7 journey.

Aditya

I love the pipe flanges, they look great.:Thumbs up:

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Originally Posted by Panomaniac

I love the pipe flanges, they look great.:Thumbs up:

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Ditto, looks better than what I picked up. Will have to look again. Let us know where you got them if you recall.

I found them at a local plumbing supplier. I am in Australia so I don't know what is avalable in the States. It is worth looking around at various outlets because there are usually several styles of flange available.