High SPL @ 60hz

[colinbg]

Hello all,

I thought I would get some feedback as I am looking to build a HIgh SPL application that is far away from the norm. Basically I am building a test application to test indutrial equipment by using sound. Specifically, I need to move air, quick bursts of air that will trigger sensors to be exact. My current plan is to use car 10" subs since they seem to have good cone travel to actually "move" the air at 60hz (best guess at what gives the most punch). I realize that 60hz is low and may not give as much punch as say 120hz, but I can always change that later. I figure since car stereo SPL competitions are popular they would have the best range of products for my appilcation. Anybody want to chime in about what would work best? I am sure this is a bit diffrent from the normal "help me" question... I thought you guys might be intrigued and lend me your expertise in choosing what would work best.

[MaVo]

you could tune a resonant system, so that its most efficient point is your 60hz. tapped horns for example have a few frequencies, where the driver excursion is so minimal, that a lot of spl could be produced, but those points are small in bandwidth, sine tones with long envelopes could be fine. short tone bursts on the other hand will have a broad spectrum.

[Peter M.]

Hi,
Are you using just a sine wave?

A BR box tuned to 60hz can get you maximum powerhandling at that fequency.

At my previous job we used a Cerwin Vega stroker 18" in BR box tuned to 50hz, and connected it straight to the wall.
240V 50 hz Great fun and it survived

[phase_accurate]

Since 60 Hz is not SUB bass you might be better off using 15" PA drivers than 10" cas subs.

Regards

Charles

[simon5]

Originally posted by Peter M.
At my previous job we used a Cerwin Vega stroker 18" in BR box tuned to 50hz, and connected it straight to the wall.
240V 50 hz Great fun and it survived

You have a 30 Amps line at your job ? That means 7200W to me !

[AndrewT]

Hi,
a vented box tuned to the desired frequency resonates at that frequency and the driver excursion is very low, allowing enormous SPL over a tiny bandwidth.

Look up WINisd and try some numbers.

But, you must monitor cone movement to check you don't overstroke your driver!!!!!!

Alternatively, build a bass horn for High SPL.

[Peter M.]

Originally posted by simon5


You have a 30 Amps line at your job ? That means 7200W to me !

We paralelled two 16A lines to be sure.
At the tuning frequency of a BR box you get an impedance peak, we didnt measure how high the peak was, so how much power it really was I don`t know.

We started first with four boxes in series- then three, then two, then one. Three was louder than four, two was about the same as three but a bit more distorted. One was less loud, but still crazy loud

[moray james]

http://www.cowanaudio.com/

[Eva]

At the tuning frequency you get an impedance DIP and the thermal power handling is the lowest among all frequencies, while the excursion limited power handling is the highest. It's quite easy to burn voice coils by applying a continuous tone near port resonance, not only due to the low impedance but because null cone displacement results in no air movement inside the pole piece and no voice coil cooling.

On the other hand, a high-Qts high-cone-excursion big driver in a small enclosure will result in gentle impedance and SPL peaks around 60Hz and plenty of cone displacement to cool the voice coil. In these circumstances, direct connection to mains is not a problem at all, impedance at 50/60Hz may be 50 ohms if the system is tuned properly. Four series/parallel drivers may be used for 230V.

BTW: Wow, now the formula to win car SPL contests is public domain

[Peter M.]

Originally posted by Eva
At the tuning frequency you get an impedance DIP and the thermal power handling is the lowest among all frequencies, while the excursion limited power handling is the highest.

Eva, you are off course right.