Wanting to mount 811's inside A7 cabinets

[gakere]

Hello all,

I really want to place the horns inside the A7 cabs (a size consideration, as per my wife...) but not sure how to go about it. By doing this it will surely affect what looks to be a purposefully designed port, so the horn inside will mess with the tuning, thus affecting (lower) bass response.

Any and all thoughts and opinions welcome.

Best regards,
Pat

[taudo]

If you search some of the earlier threads (e.g., "Bass deficiency anemia" and "Re-porting 825/828 cabinets") you'll find that most of the folks here feel that the "best-sized" port for these cabinets is about 75 sq in. (Before going the internal subwoofer route, I tuned mine a little higher - 100 sq in - and liked the result better)

Therefore, the factory "port" is _much_ too big to be optimal. I've wondered if this might be to allow mounting the horn inside the cabinet - but nobody seems to know for sure.

In any event, IMHO there is plenty of room to mount either an 811 or a 511 inside the cabinet. Exactly _how_ to do it remains an open question as far as I'm concerned. Altec just hung them inside, but I wonder if actually closing off the huge factory "port" and making cutouts for the horn and an appropriately tuned port might not be a superior solution.

As long as you're going the "inside route" have you considered copying the old "Magnificent" cab and _really_ increasing the SAF?

HTH!

taudo

[jmarkwart]

Pat,

The old 825 cabinets had two port boards, one at the top and one at the bottom of the port. Altec recommended that if the 811/511 HF horn was mounted inside the port that only the wider of the two port boards should be reattached. This effectively increased the port area from approximately 220 to 375in^2.

Jeff

[Fitts]

I suggest there are two considerations that you might want to make here. First, you should try to get the voice coils to line up and second try to get the horn as close to the woofer as possible. If you can do it, mount the horn on brackets attached to the sloped panel of the cabinet to keep it close to the woofer and in such a way as to get the voice coils lined up when viewed from the sides. If closing down the port to maintain low bass resonse is desired you might try making wings to extend from the cabinet sides to the sides of the horn forming a port of the desired size.

Regards,

[David R. Pankoski]

In the 4 - A7 cabinets I use,I have tried various port sizes in side-by-side comparisons. BTW, the 511 horns are mounted inside the 'port' area - i just made different size baffle / mounting boards for them to adjust the effective port size. In my subjective opinion, they sound best with just the horns hanging in there with no mounting board. I should mention that I lined the entire interior of the cabinets with 1/2" thick foam insulation (actually carpet underlay material). That changes the internal volume of the cabinet and will tend to dampen any rampant bass frequencies that bounce around in an uninsulated cabinet. My next project / experiment will be to add even thicker insulation to further reduce the internal cabinet dimensions and see what happens, as some users say that the internal dimensions are too large, and I generally agree.