Scare-Box Prop based on AP-16+ output loudness

[jukingeo]

Hello All,

I just received my AP-16+ today and I figured I would share with you my intended project for Halloween 2012 and I have some questions.

What I intend to do is have a Scare-Box prop in which a decorative box with a lid is firmly attached to a table and a rather obvious notice next to it saying "For a GOOD Scare, Open Me."  One would open the box and would be puzzled at first that the box is empty.   Meanwhile beneath the table the AP-16+ is already doing it's dirty work processing a pre-delay (of a couple seconds).  When this delay is up, the victim will be presented with one of three (or more) blaring sounds such as a scream, car horn, submarine Klaxon, buzzer.

The set up is very simple in which a switch that detects the opening of the box triggers the AP-16+.   One of the outputs of the board would be hooked up to a very efficient horn type speaker.  And the choice of speaker is where my question lies.

What I was thinking is hooking up a super efficient speaker that would normally be used on an electronic police siren/pa or home alarm such as this:

http://www.amazon.com/Pyle-PHSP4-6-Inch-Outdoor-Speaker/dp/B002UL0WEQ/ref=sr_1_2?ie=UTF8&qid=1348709911&sr=8-2&keywords=horn+speaker

The speaker specs are 65 watts max power handling.  The load is 8 ohms.  The spl rating is 101db at 1 watt / 1 meter.

Would the built in 20 watt (possibly slightly less in my case since I am using a 12 volt supply) amp be enough to make this speaker loud enough to scare someone (without distorting the amp)?   The speaker will be located under the table the box is on pointing out to the victim.

Has anyone used a horn speaker like this with the AP-16+ and had decent results?

Thank you,

Geo

[IMTim]

I've ran the AP-16+ on some pretty big speakers with great success.  No horn speaker, let me know how that worked. The docs state the AP-16+ will work with 8 ohm speakers.  But if you're running 12v watch your amps available on your power supply.  A one amp power supply won't put out much sound at all, if any.  I used a 12v, 5 amp power supply and I was able get pretty solid and loud sound out of the card.  Don't go cheap on power if you want a good scare.

[JonnyMac]

The critical factor is impedance; the AP-16+ works best with 4-ohm speakers.

[jukingeo]

I've ran the AP-16+ on some pretty big speakers with great success.  No horn speaker, let me know how that worked. The docs state the AP-16+ will work with 8 ohm speakers.  But if you're running 12v watch your amps available on your power supply.  A one amp power supply won't put out much sound at all, if any.  I used a 12v, 5 amp power supply and I was able get pretty solid and loud sound out of the card.  Don't go cheap on power if you want a good scare.

I think I might have a 15 volts supply laying around, but it is a switcher.   I am not sure how that will work right.

The critical factor is impedance; the AP-16+ works best with 4-ohm speakers.

I can only seem to find these horn type speakers in 8 ohms or 70 volt line, but nothing in 4 ohms.   I know two paralleled together would get me the 4 ohms I need.  But since I have the 8 ohm load (it arrived this afternoon), do you suggest I track down an appropriate 18 volt supply?

Thanx, Geo

[jukingeo]

UPDATE:

Hello all,

I had ordered an outdoor PA/Siren horn speaker and received it in the mail on Friday.   I knew that my family would be out of the house today (Sunday) and I proceeded to run some dry tests on my "Scare Box" idea for Halloween.

The setup:

As it stands I don't have the correct 18volt 3A supply as of yet.  I knew I needed something more beefy than the small 1 amp supply that I had used on the AP-8.  In my electronic box I managed to scrounge up two contenders:  The first power supply was a 16volt 2 amp supply, but I was missing the adapter-plug connector and couldn't use that one.  This is a switching type laptop computer power supply which I wasn't sure would work right on the board/amp anyway.  The next biggest supply I had was a 12 volt 3 amp supply.   The DC barrel plug was a direct match for the AP-16+ and was the correct polarity to boot.   So I was good to go with this supply.  I figured it would be at least good enough for my testing.

I had set up a remote switch for testing and I even set up a PIR sensor to see how that would work as well.

I loaded up an SD card with many different 'scary' sounds that were basically very loud or came on suddenly at the start and were very short. Since I was inside, I set the volume control to slightly above the 'off' position.  I set a slight pre-delay of about 2 seconds and a post delay of about 10 seconds.

I started with my old standby, the car horn.   BLAAAAAAAAHHHHHRR!   Success!   I was amazed at the volume I got with the control almost off.   I put the control then in the 9 o clock position and tested it again.   I nearly jumped out of my chair.   I totally wasn't expecting that volume out of the speaker with the volume control that low.  Things were really starting to look good for this speaker,  however, I knew I was testing the setup sitting right on top of the speaker AND I was indoors.  I knew I would have to take the setup outside to see how it would perform.  So I proceeded to edit and load up some more sounds to test.

I next started started with some monster sounds and some other sudden sounds such as gunshots.   These didn't sound too good.   The gunshots were too transient and didn't sound very good.   The monster growls didn't sound good either, even if they did start suddenly.    At first I was thinking that I might need the larger power supply, but then I though that couldn't be it as I was still testing at low volumes.     As it were, the monster sounds were too low in frequency to be accurately reproduced by the horn.  Checking the specs the horn is rated for 500hz to 8000khz.  So anything below 500hz would die a quick death right at the speaker.

Taking a good look at the speaker it dawned on me that the loud sounds that would work best on this speaker would be those that would normally be run on a speaker like this in real life.   So that means sirens, horns, Klaxxon's, loud crashes, and possibly even voice would work on a horn of this size.

So I tried out a buzzer type sound and a home alarm hi/lo siren.  These sounds worked PERFECTLY.   While loud crashes also worked good, I found I had to record them a bit louder than the sirens.   The alarm siren was so efficient that I even had to record this sound LOWER to keep it in line with the rest of the sounds.

I have about four sounds that I really liked:

1) Car Horn
2) Buzzer
3) Loud hit/crash
4) House Alarm

I put these on the SD card.  I took the setup outside and I setup the speaker horn under a picnic table in the backyard.   The mock 'box' was on top.  For outside testing I started with the volume in the 10 o' clock position and I set the AP-16+ to randomly shuffle the 4 sounds.

Results:  WOW WOW WOW!  I ended up scaring myself multiple times.   My family came home around that time and I figured I would have some guinea pigs to test out my contraption.   Boom!  Everyone jumped!   The girl who lives in the apartment upstairs came down with her friends to see what was going on and I ended up getting them too.

Needless to say, it was a successful test even with not having the correct power supply AND the speaker being 8 ohms.  Finally, I didn't even dare to put the volume up past the halfway point.   The speaker was VERY loud in my final testing position of 11 o'clock.   For those being right on top of the scare where the speaker is, I don't think I would need more volume.

The key was that I was using sounds that would normally be heard on a horn such as this.   With no low frequency content, there was nothing there to rob the normally 'small' 20 watt amp of it's power.  Using anything with low frequencies would sound terrible at best given that the speaker cannot reproduce those sounds to begin with, as I proved when trying to use the monster sounds.  All you would be doing is wasting precious power.   Given that I was using sounds that also matched the efficient frequencies of the speaker, it sure made it seem like the speaker was being driven with by far more power than I was putting into it.

That being said, now picture this: I was only using ONE channel of the amp with ONE 8 ohm speaker and volume was up halfway.   Theoretically, you could use TWO speakers on EACH channel to get 4 ohms.   With four speakers, using any siren or horn type sound would be outright deafening.

Being that this has proven to be a successful test, I could make my rig a bit smaller than I intended.   I did purposely design the rig larger than anticipated in the event that I needed to use a real car horn or a real Klaxxon horn.   But with pretty much everything located on the small AP-16+ board I can make everything much smaller.

As of yet, I have not tried human voice screams yet.  I have a funny feeling they probably would work too as human voice does fall into the frequency range of the speaker.   So more testing will ensue.

I have to give my thumbs up to both Jon and John for creating a great product in the AP-16+ in making a totally self contained audio prop controller.

Geo