Multimedia Satellites, Open Baffle?, Full Range? Driver Selection Help Required

[johninCR]

If you don't have an amp already lined up, you'll need something because the soundcard is a low level line out. I'd recommend a $100 Powerwave. It's got a bunch of serious audiophiles talking about it on some other forums. It has some kind of new chip amp and it's made for computers. Mine won't be in for about a week, but I trust the people I've seen say good things about it.

[ozynigma]

JohninCR,

Thanks for those tips, interestingly I have kind of started down the path you suggested today.

I went and bought 4 of the cheapest 4" shielded drivers I could find, figuring if it doesn't work I haven' t wasted any money and if I want to improve the speakers in the future I can always upgrade the drivers. (cost about US$3 each)

I also bought a couple of budget shielded dome tweeters which I may also upgrade in the future.

I can build a tower up to about 500mm tall to fit beside my 21" CRT monitor. So I can easyily fit 2 x 4" drivers and a tweeter in the tower. Maybe I should buy another two drivers?

I will definitely try the open baffle now, its only a few pieces of MDF and if it doesn't work I can just build a sealed box.

As far as amping goes I am considering a number of possibilities
1) buying a second hand integrated stereo amp and sitting it on the sub, under the desk.
2) building monoblock power amps into the base of each tower so the speakers become self powered. The soundcard could control volume and balance etc.
3) building a DIY stereo amplifier.

Building an amp would be a first for me, so I will finish the speakers first.

Howard

[Timn8ter]

Originally posted by moving_electron



Approximately how wide and deep would such a speaker be?

I was pretty close in my recollection. Internal height of 16" and internal cross-section of 22 sq in., 1.5" port tube, 2" in length.

[johninCR]

Build test baffles first with cardboard or that strong posterboard used for building architect models. You can be listening within 5 minutes, it's adjustable, cuts with a steak knike easily, etc. Experiment before cutting any wood or MDF.

Maybe you got lucky with the cheapest, but I had to do alot of hunting and listening. Listen at the store. Many are junk. Visually it's hard to pick out the junk, but one thing I've noticed in many of the junk shielded drivers I've seen is that when you push on the cone the surround doesn't bend evenly. It's a dead giveaway for being junk.

I'd hate for your first OB to not work because they really are different in good ways.

[ozynigma]

Originally posted by 5th element
I would do a box, either sealed or ported which ever is required to get suitable bass extension to meet the sub. Id choose sealed if possible but ported would be fine also.

5th,

Thanks for the advice.

I am going for a small sealed box Qtc of about 0.9

The box will be very similar to that described by Tim. About 125mm W x 500mm H x 125 - 250mm D (note slanted front baffle).

Using some cheap drivers first and if the box looks good and sounds reasonable I will upgrade to some higher spec drivers.

Going to go MTM 2.5 way, rolling the lower driver off for BSC.

So I will have a lot to learn as I build my first crossovers etc.

Will post some pics as it progresses.

Howard

[johninCR]

Leave the back off of one of the speakers until everything is ready. Once 1 box is ready, tape a 3" cardboard extension at the back on one side and 4" on the other and tape the vent for the open back box. If the open one doesn't sound better, I'll eat my hat. It may not have much bass, but what is there will be better.

If you already test an OB with those drivers and didn't like how they sounded, go swap them out for some different drivers because you won't like them in a box either and listen before you buy.

[ozynigma]

John,

I am going to make the speaker back panels removable, ie screwed and caulked, not glued.

So I can certainly try these open and sealed to hear the differences.

I am still interested in doing an OB project but maybe in a full size, full range speaker. To do it properly I think I need to learn a lot more about baffle losses and equalisation.

Howard

[Timn8ter]

I tested the W3-871S in open baffle and at moderate volumes it sounded wonderful. I bet it would be great for near field listening. You may not even want a top on it. I thought they were better on a flat baffle or possibly with tapered sides. No bass of course.

[johninCR]

Those TB's look nice for OB...Small baffle...I could put a pair of my little 6" TV drivers in a W baffle at the bottom to help with the bass and get some nice bookshelf sized dipoles.

[ozynigma]

I am now planning to use 2 x 4" drivers and a tweeter. Front baffle will be slanted back 15 degrees.

I am thinking of going 2.5 way with both drivers at the front in an MTM configuration and roll the bottom driver off for BSC.

If I was to make the second driver rear facing instead for BSC then for a rear facing driver how important is symmetry with the front driver?

If I rearface the second driver will it matter that the rear baffle is vertical and the front is slanted?

Does the rear facing driver have to be at the same height as the front driver?

Or what if I slanted the rear baffle mirror image to make a triangular bi - pole configuration?

Howard