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Schaef 23rd October 2001 01:10 PM

I've been contemplating the construction of a set of MTM speakers now, and have some questions regarding the design of the enclosure. (Keep in mind when reading this, I'm also a woodworker with some experience in building cabinets) My first question would be how much does the shape of the box affect the sound? Is the volume the key thing and then to a much lesser extent the shape? I'm asking, because I'm thinking of going with an existing design somewhere (don't know yet what I'm going to use) but make the box much more visually appealing. (Helps with the SAF) I know parallel walls cause lots of problems, so I'm thinking of units with several smaller walls at different angles. Is this going to have an affect on the sound at all?

Also, on a related note, does the shape of the port do anything to affect the sound? What about placement? (I did see the thread about port placement, and it answered some questions, but thought I would include it here as well)

Might as well add, any suggestions on a nice design that won't break the bank? (I'll hopefully end up with about $500 total to work with, including cabinets, etc.) They'll probably end up spending part of their life in my HT system until I can save up enough money again to build a separate stereo-only system for vinyl and CD.

Thanks for the help!

Schaef 23rd October 2001 01:17 PM

additional question I forgot
 
Okay, I forgot one other question. How much does the shape of the baffle affect the sound? The designs floating around in my head have either a very fluid look to the outside, (read no corners, all curves) or have a art deco/sleek look to them. Some of the ideas would not have a baffle of a constant width, what are the problems possible with this? Is this a bad idea? Should I just go home and build that table the wife wants?

Again, thanks for the help/info!

29th October 2001 08:18 AM

Nobody replied yet?
 
You asked a very general and open question. Probably the best baffle would be an infinate baffle. But in real practice you have to keep it reasonable. Everything affects the sound in one way or another. Do a search on baffle diffraction or diffraction loss. Several different sites out there with lots of information. Port shape is not too critical as long as the port size is correct. It should be large enough to minimize compression and or wind noise/turbulance. A round flared port probably works best. I prefer my ports mounted on the back side because that way any leaked midrange or other spurious noise is lessened.

Per 29th October 2001 03:08 PM

Try building a combo between transmissionline and inf. baffel. Ive made several using this method: use the calculated Vb, then make a maze, in wich the sound will travel, and make the maze end in 1, 2 or 3 acoustic vents, depending on the size of Vb. This type of cabinet will take advantage of inf. baffel and to some ecstend a vented cabinet, but without the vented's disadvantages: large faseshifts and a more loose bass, than inf. baffel.

Super 29th October 2001 07:48 PM

Just giving you two primary things to go off of. First, there is a general belief that speaker with a narrow baffle have better imaging, though I've seen exceptions. Second, you should try to eliminate parallel walls. If you don't, standing waves will become a greater factor.

I would not suggest a tapered baffle for an mtm design, because the two midwoofers would be out of phase.

Rounding the corners is an excellent idea, and is common practice nowadays. It helps eliminate edge diffraction.

Schaef 30th October 2001 01:43 PM

Another question
 
Sorry if these are pretty basic questions, but I'm just trying to figure out what I can and can't get away with. Here's another question, with the previous disclaimer in effect, does the port have to go into the speaker? Is there a problem with having it sticking out of the back? (Or does this become more of a transmission line?) Also, would most of these questions be answered by the Loudspeaker Design Cookbook? (How basic does it start out, and does it explain WHY things are done the way they are?)

As to the tapered baffle, why does the width of the baffle affect the phase? (I wasn't thinking of having the woofers on different planes on the baffle, just having the edges of the baffle taper)


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