Air leaks in horns

[xcortes]

Just finished the cabinets for the Fostex Fe103E recommended back loaded horn enclosure. These are my firts horns after building a couple of minimonitors projects. I won't have the drivers until one week from today so no way of testing.

I'm concerned that, due to the nature of the box there might be some air leaks. I sealed everything before placing the last side panel but I´m sure this one didn´t seal 100% with all the internal walls. I can seal the junctions in the outside but obviously not those on the inside.

What effect will this have on the sound?

Thanks,

xavier.

ps. I don't know how will they sound bou boy they look soooo cool!

[BillFitzmaurice]

Any leakage anywhere in the horn will be detrimental to performance, most especially any leaks between different horn segments.

One way to ensure a good seal is to use polyurethane based adhesives; I prefer construction type adhesives, applied with a caulking gun. Polyurethane adhesives expand as they cure to fill any voids.

www.billfitzmaurice.com.

[xcortes]

Thanks Bill. That's exactly what I feared. Two questions:

Exactly in what sense will the effect be detrimental?
How much?

I'm trying to determine whether I should put them apart (at least try to) and then back together with a different adhesive or sealant or just wait 'till I get the drivers and try them.

Thanks,

xavier

[BillFitzmaurice]

What will happen is a loss of bass response, as air leakage from one section of the horn to another will allow passage of sound waves as well, and there will be phase induced disruption of the primary wave passing the length of the horn, The effect could be quite benign if the leaks are small, and very serious if the leakage is pronounced. But tearing the boxes apart could be a waste if the leakage isn't there. I'd mount the drivers and test the boxes to see if their response is within tolerance before going back to square one.

[xcortes]

thanks again bill.

i will have the drivers one week from today. will post my results.

[xcortes]

I mounted the drivers. Bass extension seems fine reaching to around 60 hz (and then dropping dramatically). However it is a little boomy. Maybe they're designed that way? A crude measuring shows a 3/4 dB peak from 70 to 90 hz (adjusted for room resonances).

Midrange needs clearing. I guess the lack of filling material is causing internal refractions. I will try polyester filling during theweekend. This should take care of the midrange issue.

Will post more results and pictures in the next days.

Thanks

xavier

[BillFitzmaurice]

Make sure that there are no unlined surfaces within the chamber behind the driver; they need a good inch of polyfill to suppress midrange reflections.