Speaker

[ScottC.]

Hi Trevor, I just got my speaker and amp and will be using Visual Analizer as my tone generator. In the design book page AI-4 Fig AI 2-1 it states the speaker is loaded in a piece of PVC and capped on the far end, my questions are:
1. How is the speaker mounted in the PVC?
2. Is the cap on the end opposite the speaker?
3. Is the cap cut out any to allow air to move out?
Thanks, Scott C

[Trevor Gore]

1) The speaker is mounted in a MDF "baffle plate". This is just a circle of MDF, same OD as the PVC pipe, with a rebate about three quarters the thickness of the MDF cut the same depth as the pipe is thick, so that the MDF sits in the pipe like a lid, edges flush. Then the middle of the MDF is cut out the right diameter for the speaker that you are using. I used my rosette cutting jig (shown in the book) to cut all the circles. The baffle plate is held in using some small countersunk screws through the side of the pipe into the edge of the MDF. Can be glued in, too if you like. You will always have access to the inside through the hole for the speaker.

2) The cap on the back end is the same as above, but without the speaker cut-out.

3) This arrangement is called an infinite baffle, in speaker terminology; so no open cut-outs or ports etc.

[ScottC.]

Thanks Trevor, would you be able to post a few pics of your speaker tube?
Scott C.

[kiwigeo]

Heres my set up. The speaker is a 50 watt unit I got from Jaycar running off a 50watt Bradley signal generator. I had the speaker taped to an old plastic bucket at the start but found I was getting quite acceptable results without the plastic bucket and now do testing with just the naked speaker.

[ScottC.]

Thanks, I have been just foolin around with the speaker naked on a braced top, I see you have to get the speaker position just right for each mode. I would wonder if Trevor gets more output with his setup.

Heres my set up. The speaker is a 50 watt unit I got from Jaycar running off a 50watt Bradley signal generator. I had the speaker taped to an old plastic bucket at the start but found I was getting quite acceptable results without the plastic bucket and now do testing with just the naked speaker.

[Trevor Gore]

Pics of speaker as requested. I use a 15 watt amp.

Top.jpg (155.62 KiB) Viewed 15231 times

Bottom.jpg (158.19 KiB) Viewed 15231 times

Top side.jpg (156.22 KiB) Viewed 15231 times

[kiwigeo]

Thanks, I have been just foolin around with the speaker naked on a braced top, I see you have to get the speaker position just right for each mode. I would wonder if Trevor gets more output with his setup.

Heres my set up. The speaker is a 50 watt unit I got from Jaycar running off a 50watt Bradley signal generator. I had the speaker taped to an old plastic bucket at the start but found I was getting quite acceptable results without the plastic bucket and now do testing with just the naked speaker.

I find it doesn't take much time to find the "sweet spot" for each mode. The monopoles and dipoles are easy, some of the more complex modes in the higher frequencies can require moving the speaker over the top and exciting several areas of same. After a couple of sessions "playing around" you soon get the hang of it. By then the neighbour will be knocking on your workshop door wanting to see the alien spaceship

[ScottC.]

Thanks for the pics, pics help me a lot! Do you find it to work better than an open speaker?
Scott C.

Pics of speaker as requested. I use a 15 watt amp.

Top.jpg

Bottom.jpg

Top side.jpg

[ScottC.]

Yeah, I'm gonna fool around some with it today, I am lucky enough to not have neighbors close, but it does scare my beagle.

Thanks, I have been just foolin around with the speaker naked on a braced top, I see you have to get the speaker position just right for each mode. I would wonder if Trevor gets more output with his setup.

Heres my set up. The speaker is a 50 watt unit I got from Jaycar running off a 50watt Bradley signal generator. I had the speaker taped to an old plastic bucket at the start but found I was getting quite acceptable results without the plastic bucket and now do testing with just the naked speaker.

I find it doesn't take much time to find the "sweet spot" for each mode. The monopoles and dipoles are easy, some of the more complex modes in the higher frequencies can require moving the speaker over the top and exciting several areas of same. After a couple of sessions "playing around" you soon get the hang of it. By then the neighbour will be knocking on your workshop door wanting to see the alien spaceship

[Trevor Gore]

Do you find it to work better than an open speaker?

I've always used this arrangement, so I have no extensive comparison. I've always been able to get good patterns using a fraction of my 15 watts. I think you get less ambient noise with the enclosed back, but as I said, not much comparative experience. I've always been concerned about all the sharp edges of an unenclosed speaker chassis, giving a high risk of dings etc. That reason alone is sufficient for me to use some sort of enclosure.

[ScottC.]

That makes sense to me. I am gonna look at Lowes tomorrow for the right size PVC and cap. I would wonder about putting some kind of handle on it so I only have to use one hand to hold it.
Thanks, Scott C.

Do you find it to work better than an open speaker?

I've always used this arrangement, so I have no extensive comparison. I've always been able to get good patterns using a fraction of my 15 watts. I think you get less ambient noise with the enclosed back, but as I said, not much comparative experience. I've always been concerned about all the sharp edges of an unenclosed speaker chassis, giving a high risk of dings etc. That reason alone is sufficient for me to use some sort of enclosure.