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 Post subject: Inexpensive 2.1
PostPosted: 05 Sep 2012, 16:24 
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Joined: 05 Sep 2012, 16:07
Posts: 1
Hello.

I'm doing a small speaker project for my outdoor porch on my cottage and need some help.

The porch measures 28' wide, 7' deep, open along one long side and one short end. The ceiling slopes up from app 7" at the open front to 8' at the back. I'm wanting to do a simple and inexpensive 2.1, the full range sat boxes will be mounted up near the ceiling at the back wall and spaced about 24" apart, a sub is planned for either as a end table base measuring app. 16" cube or as a box "inside" the legs of a bench located at the closed end of the porch, space available there is 16" x 12" x 48".

So far I've decided that I'll be using a 12v head unit since I have one sitting around plus it has am/fm/cd and has usb inputs for ipod, iphone, etc. I'll also be using a 12v amp since I get some nice prices or find good 2nd hand units. Also decided is using some CV horn tweeters from their old "D" series that I also have gathering dust.

What I need are driver suggestions to go with the tweeters on hand as well as a nice sub. Specs on the CV's are roughly 4000-19000, mid-hi 90's w/m and 8 ohm.

The sats need to be as small as possible to meet the "significant other" requirements, produce decent but not critical sound and should be as efficient as possible.

Box wise I can produce anything as simple or complicated as you through at me, technical wise I best leave to others.

So maybe someone has some ideas?

Thanks!


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 Post subject: Re: Inexpensive 2.1
PostPosted: 08 Sep 2012, 21:21 
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Joined: 04 Jun 2008, 20:59
Posts: 4098
Location: Arizona, USA
Hi, Welcome to the forums. First to get any sort of stereo effect I would suggest the sats be at least twice the distance apart that you indicate. 4 -5 feet would likely be a good separation. Space them equally aways from the sides if you can. Having one closed side and one open side will alter the sound distribution a good deal in any case. Angle them inward a bit to compensate for it, perhaps 20-30 degrees would be sufficient. To be spouse friendly size is clearly an issue. Since you are going to use a sub you can get away with a crossover from it as high as about 200hz without serious sonic problems. This would be excessive in a serious stereo application, but for what you seem to intend ought to be fine. With that high of a crossover you can probably use a 4 inch mid-woofer. Check out sources like Parts Express on the web for ones that are available. There are several. I would look for one with an F3 of about 125-150HZ (no higher for sure) and similar sensitivity to the tweeters you already have. A simple 12 db/oct symmetrical crossover at around 6500HZ to 8000HZ would seem best between the mid-woofer and tweeter. That should be high enough to keep either driver from going tilt. The crossover to the sub can probably be best handled by your receiver if it has suitable outputs. If not then another 12 db/oct symmetrical one would likely be the best next choice. BTW there are design equations on the PE site as well as others (just google crossover networks). With a potential volume as large as you indicate for the sub you can really do wonders. I probably would go for some in the 12 inch size. Often cheap and can reach rather low in that size box. My preference is for vented systems as they will go as much as an octave lower than similar closed boxes and typically have higher efficiency. Considering cost... I would look for something with an F3 of about 35 HZ and efficiency in the mid 90 db/w range. You will probably have to pad down the sats to match it in any case. There are box tuning formula on the web to help you figure out the best low end response. I suggest you select the box first and then hunt for the sub. I find it easier that way.

I am surprised that your CV horns are not more efficient. Many are well over 100db/w.

Sound like a fun project

Good listening
Bruce

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