Percieved Volume of 11x15 w/ Larger Chamber vs 13x18 with Smaller

[mbrodnax]

Hopefully in the next few weeks I will be getting the BLI stealth Mikado but unfortunately I did not read the fine print and ordered(and received) an ESU micro which apparently can't fit the stock partially due to the speaker. While I could exchange for a Nano, returns are a pain, and the stock speaker is mediocre at best anyway. My Bachmann connie has an esu 11x15 with the full baffle so about 9.5mm high total. However, I'm not sure if I'll be able to fit that in the BLI. I was wondering if a smaller baffled 13x18 would produce similar or better volume than the 11x15 with a bigger baffle. Or ideally, if anyone has experience installing a larger baffle in a BLI mike. Right now I'm looking at the CRude engineering 13x18 medium baffle which would be  7.65mm total or the medium large which would be 10.65mm total.

[jdcolombo]

FWIW, I used an 11x15 in my BLI Mike.  My recollection is that the speaker enclosure height was 9mm total, but now I can't remember.  It might have been 8mm.  I also used a TCS KA-3 keep alive, although if I were re-doing this today, I'd use a KA-1 instead and save a bit of space.  My install used an older Loksound Select Micro, but a V.5 micro will fit fine, particularly if you ditch the KA-3 for a KA-1.  I strongly recommend a keep alive even though the BLI's electrical pickup is pretty good.  Pretty good isn't perfect; hence the KA.

https://www.therailwire.net/forum/index.php?topic=48510.0

John C.

[jdcolombo]

I should add that my general experience is that an 11x15 in an enclosure with at least 1000 cu.mm of internal space will sound just as good as an 13x18 with the same 1000 cu.mm. internal air volume.  An 11x15x8mm enclosure made out of .030 styrene means that the internal volume of the enclosure is roughly 11x15x7.25 = 1196 cu.mm  (the 7.25 comes from subtracting the thickness of the .030 styrene bottom, roughly .75mm, from the 8mm total height).  You might be able to eek out a bit more "bass" from a 13x18, particularly with the V.5 micro's ability to increase bass output, but I doubt it is enough to be worth worrying about.

John C.

[mbrodnax]

I should add that my general experience is that an 11x15 in an enclosure with at least 1000 cu.mm of internal space will sound just as good as an 13x18 with the same 1000 cu.mm. internal air volume.  An 11x15x8mm enclosure made out of .030 styrene means that the internal volume of the enclosure is roughly 11x15x7.25 = 1196 cu.mm  (the 7.25 comes from subtracting the thickness of the .030 styrene bottom, roughly .75mm, from the 8mm total height).  You might be able to eek out a bit more "bass" from a 13x18, particularly with the V.5 micro's ability to increase bass output, but I doubt it is enough to be worth worrying about.

John C.

Thanks John. So as long as the enclosure sizes are similar, you didn't find there was much volume/frequency response difference between the two speakers? Also are you saying the enclosure was 8 mm or the enclosure plus speaker was 8 mm?

[jdcolombo]

As long as the enclosure sizes have at least 1000 cu.mm of internal space, I perceive no difference in loudness between the 11x15 and the 13x18.  If you use the ESU V5's bass boost feature, then the 13x18 will give you a bit "richer" sound on the chuffs, but the bell and whistle will sound basically the same.

To reach the 1000 cu.mm internal volume, you need an enclosure that is at least 7mm high ON THE INSIDE.  If possible, I build my enclosures with .030 or .040 styrene, which means the bottom of the enclosure is about 1mm thick.  So I use a minimum of 7mm-high sides, and then glue on an .030 (.75mm) or .040 (1mm) bottom, for an overall height of about 8mm.  In general, a bigger enclosure is better - if you can use 9mm or 10mm of overall height (including the bottom), you'll get slightly (but only slighty) better sound.  1000 cu.mm is the sort of "break point" - below this and the sound will get noticeably worse the smaller the enclosure is.  Above this, the sound will only get marginally better, and at some point you can actually get an enclosure that's too large.  But 9 or 10mm is good if you can fit it in.

I use the 11x15 a lot in my steam installations, mostly because I want to mount the speaker transversely (like the photo in my install thread) to save space for adding a keep alive.  I don't tolerate any stalling by engines on my layout, and without a keep alive, even the cleanest track and wheels will still result in occasional sound dropouts or momentary "glitches," particularly with slow speed switching moves.  With a keep alive, these issues completely disappear.  N scale engines are simply too light overall to maintain perfect electrical contact even in the best of conditions.  So for me, a keep alive is mandatory in a sound install.

John C.