846A port modification question

[kwingylee]

Last weekend I went to a local audio meeting and the host demonstrated a highly modify pair of 846As to improve its bass response.

1. A 1.25" by 14" slot was cut in the bottom of the cabinet as close to the cabinet front as possible.
2. The port area surrounding the 811B horn was sealed.
3. The speaker was put over a riser that is approximately 50% of the total height of the Valencia
4. The riser has a build in folded horn, such that the waves out of the bottom slot is traveling approximately 2X the depth of the cabinets.

The results were a pleasant surprise to me. The bass sounded subjective deeper and more define. I probably need to optimize the horn flare and the slot size (the builder could not give a good technical reason for the size he chose), but has anyone in the forum tried this? I can include photos later.

Kwing Lee

[Old Guy]

You are probably hearing a peak in the response, any such folded horn would be too tiny to add deep bass.

[kwingylee]

You are probably hearing a peak in the response, any such folded horn would be too tiny to add deep bass.

Hi Old guy.
You are probably right. As the horn is too short and the mouth too small. On the other hand, this would be a good way to increase the internal volume of the cabinet and redo the port, perhaps making it a pseudo M19...?

[Old Guy]

Hi Old guy.
You are probably right. As the horn is too short and the mouth too small. On the other hand, this would be a good way to increase the internal volume of the cabinet and redo the port, perhaps making it a pseudo M19...?

I would maybe like GM to chime in. But yes, you could I think build a riser and open the bottom of the Valencia. Everything would need to be sealed well.
I would just make the riser a box. I think you should be able to add the two volumes and tune the port accordingly.

[GM]

Done right, the vent becomes a type of broadband radiator [AKA double bass reflex] instead of a ~ 'one note' resonant pipe, so can fill in above box tuning where the driver runs out of Xmax.

The trade-off is more vent harmonic output comb filtering with the driver's output up into the mid bass and some of the 'full range' driver aficionados will make them more like mini-BLHs with blending up into the lower mids, but this is getting up into our acute hearing BW, so to be avoided with HE systems IME.

GM

[kwingylee]

Done right, the vent becomes a type of broadband radiator [AKA double bass reflex] instead of a ~ 'one note' resonant pipe, so can fill in above box tuning where the driver runs out of Xmax.

The trade-off is more vent harmonic output comb filtering with the driver's output up into the mid bass and some of the 'full range' driver aficionados will make them more like mini-BLHs with blending up into the lower mids, but this is getting up into our acute hearing BW, so to be avoided with HE systems IME.

GM

GM, Old Guy, getting it right is always the challenging part :-) ... I have walked away from this idea as I was able to pick up a set of M19 cabinets with N1201 crossovers plus a set of blown 416-8Bs. I might just move the components from the Flamenco to the M19 cabinets, once I repair the water damage on the bottom of one of the M19 cabinets :-(