Effect of Enclosure Size on Sound

[jdcolombo]

Hi folks.

Since I was playing around with my 8x12mm speakers anyway, I decided to do another comparison - this time on how enclosure size affects sound.  Streamlined Backshop now provides two different-sized enclosures for their speakers: a standard enclosure and a "double deep" enclosure.  The standard enclosure is about 3mm high and when the speaker is installed, the overall height is 5mm.  The "double deep" enclosure is 6mm high, and the overall height with speaker is 8mm (which is actually a bit too high for installation in a narrow-hood diesel, but you can easily sand off 1mm of the enclosure top to reduce the height). 

So, I took 4 speakers I had lying around: an SBS speaker in the standard enclosure and one in the "double deep" enclosure, a Star Micronics 8x12mm in an enclosure built with .040 x .250-high styrene strip sides and an .020 styrene bottom for a total height of about 6.8mm and a Star Micronics in an enclosure built from .040 x .188-high sides (about 5mm) for a total height of 5.5mm with the same .020 styrene bottom.

As the video shows (I think), the smaller enclosures produce a sound that is noticeably "thinner" without as much lower-midrange.  As a result, the throttle-up sounds and the overall "beat" of the EMD 567C prime mover aren't as "impactful" as with the larger enclosure.  The bell and horn sounds, being higher in pitch, are pretty much the same, although I seem to detect a slightly lower overall loudness with the smaller enclosure.

Once again, this comparison was done using an ESU LokSound Select Micro with the #73436 sound file (EMD 567C V-16 non-turbo).  I think the test demonstrates that my practice of using the largest enclosure I can is a good rule of thumb.  For most hood diesels, that's something a tad under 7mm if you mill the frame down as far as possible.  But you can't always get away with a larger enclosure, and even the smaller ones sound "OK" I think - just not as good as the larger ones.

Here's the video:

John C.

[Cajonpassfan]

John, again, thank you. I agree with your assessment; in this case bigger does seem better!
Please don't think of me as ungrateful (I'm not) but here's an idea for your consideration: the comparos (between speakers or enclosures) might be more effective if one could toggle back and forth between each two. This way we have to "remember" the sound...and my 66 year old ears are not as good as they used to be either. And memory, forget it
Otto K.

[Santa Fe Guy]

Your a youngin Otto, god damn it I'm already 73 and have had hearing aids for the past two years.
The new sound decoders that keep being released along with these speakers are still music to these old ears.
Regards
Rod.

[Cajonpassfan]

Lol Rod, agreed on the "music"; we've never had it so good
Otto

[carlso]

John C. -
thank you for sharing your expertise and talents with all of us, it is very much appreciated. I think TRW should set up a special "sound" section for yours and others posting regarding sound only.

Rod -
gotcha youngin, I am 76+ and am extremely fortunate to not have hearing problems. I worked for Chevron Pipe Line and was around 800hp,and some higher, electric motors. I learned quite early to wear hearing protection. My problem seems to be that I don't always think before speaking. I would certainly second yours and Otto's comment about "music" to our ears. As you both know  sometimes it can be overwhelming. I will not give up on sound installs, just waiting for the new small size ESU decoders.

Carl

[robert3985]

Hahaha!  Carl and Rod, you ol' creepers give me hope of at least another decade enjoying the hobby!  Hopefully maybe two decades???

Cheerio!
Bob Gilmore at 67

[milw156]

What about increasing the volume by increasing the length or width of the speaker enclosure instead of the height? Seems there are a number of installs that would alow for more length than just the length of the speaker (cab area or fueltank).
Rick

[peteski]

What about increasing the volume by increasing the length or width of the speaker enclosure instead of the height? Seems there are a number of installs that would alow for more length than just the length of the speaker (cab area or fueltank).
Rick

That should be fine. What matters is the volume of the enclosure - the shape is not very critical (in our application).  As long as the enclosure is air-tight and has stiff walls (which do not vibrate) it will improve the sound quality.  That is why I really like the idea of making the enclosure out of sheet lead.  One of the guys here mentioned that in the past.

If you ever had a small laptop computer apart you would probably notice that its internal speakers often have very long and thin enclosure (just like what you suggest).

[jdcolombo]

Ditto.  The shape of the enclosure doesn't matter, just internal volume.  A long, thin enclosure with the speaker set off to one side is perfectly fine, and I have used these designs myself.

John C.

[milw156]

Thanx!
Rick