First DIY Single-Full-Range-Driver Help Needed

[GregGC]

After building a GC (thanks to this forum) and being very happy with the results, decided to build efficient speakers based on the same philosophy (less is more). No crossovers, the simpler (to a reasonable degree) the better.

So after exchanging info with some of you guys (Ron, thanks a lot for your input) I decided to go with single full range driver design with the potential (if I need extra HF) to add a supper tweeter. So I decided to go with the Fostex FE207E DBR box as proposed in the Fostex's recommendation for a speaker box for this specific speaker. If I have to add the Supper Tweeter where would you suggest I should locate it? I don't mind if it sits on top of the box in a nice enclosure either.

I have never build a cabinet for a speaker, so I expect to have a lot of questions and also I'd like to explore the possibility of having the speaker boxes build by someone that has experience in wood-working. I'm located in Toronto/Canada. Do any of you guys know of a company/individual that would do something like that or maybe a shop that would have the tools needed or maybe other alternative that I don't know exists. I'd really appreciate any type of information.

I don't want to spend $$$ on exotic type of wood, so what would be the most reasonable type of material I should use for that project. I don't mind having the cabinets painted but if there is a reasonable alternative for wood-like look I'm open minded. MDF, Plywood....?

Looking at the plans for the DBR configuration I wondered if it'll be easier (and I don’t mind the look of it too) to use a round BR opening for the one inside and the outside instead of the square ones. Any +/-. I know it'll be much easier to tune if it's made out of plastic tube. I'm not sure exactly how to calculate the equivalent config. but I'm downloading dif. kinds of software and learning as much as I can.

Suggested Free software for helping me with some of the calculations, though it looks like there wont be any if I decide to stick to the recommended by Fostex design.

Any kind of advise is appreciated!

Thanks in advance and apologies for the boring tread I started.

/Greg

[Timn8ter]

If you can afford it, go with a good quality void free plywood. You will probably have to go to a lumber yard, not a chain "home improvement" store. Otherwise, use MDF with a nice veneer. People complain about MDF (with good reason) however, MDF doesn't warp or cup like solid wood does, and if the veneer is done right who'd know? Fostex puts their ST on top, Terry Cain put his close to the main driver. I'm not sure about the effects of placement at these frequencies. I suspect it's not as critical as it would be in the upper mid-range.

[GregGC]

Originally posted by Timn8ter
If you can afford it, go with a good quality void free plywood. You will probably have to go to a lumber yard, not a chain "home improvement" store. Otherwise, use MDF with a nice veneer. People complain about MDF (with good reason) however, MDF doesn't warp or cup like solid wood does, and if the veneer is done right who'd know? Fostex puts their ST on top, Terry Cain put his close to the main driver. I'm not sure about the effects of placement at these frequencies. I suspect it's not as critical as it would be in the upper mid-range.

Wow I can't dream of anything like that.

Thanks for the suggestion. I'll check the area around for lumber yard.

Regarding the ST, some put it even at the back of the box. I don't think that'll be an option for me. I've seen it placed (similar to your picture) closer to the inner edge of the speaker. Id did some experimenting with my existing speakers by adding some fome weatherstrips next to the HF driver and found that the imiging improved alot compare to no-fome-strips version. Also I heard some speackers with a simmilar placement (offset to the inner side) that really had a good imiging, but as you said at those ST high frequencies may be less important.

Thanks again!

/Greg

[Timn8ter]

Hmmm...your picture makes me wonder about offset tweeters rather than in-line.

[GregGC]

Originally posted by Timn8ter
Hmmm...your picture makes me wonder about offset tweeters rather than in-line.

I'm sorry, but I'm not sure what you mean. On the picture you see the speackers that I use right now and I don't plan on touching them. The rubber strips yu see really changed the soundstage. Actually the latest position on those is : single strip around the left right and bottom part of the tweeter (so not exactly as shown). The biggest efect I got from the inner strips (single one only).

I'll put together a drawing if you want.

Thanks
/Greg

[Timn8ter]

Just thinking out loud. I was contemplating your treatment in relation to mounting tweeters offset on the baffle rather than in-line as your current speakers are. It wasn't meant to be a suggestion.

[454Casull]

Might wanna go dipole. Inexpensive.

[x. onasis]

Hi Greg, Shoot me an email: xonasis2000 at yahoo.com

Do any of you guys know of a company/individual that would do something like that or maybe a shop that would have the tools needed or maybe other alternative that I don't know exists.

Perhaps we can trade something.

[GregGC]

OK,

Wich one of those graphs looks the best. Sound is probably a diferent story, but as a start wich one would you go with?

1. FX200 , my tweek
3. FX200 , recomended

4. FE207E , my tweek
2. FE207E , recommended


Sugestions on changing the volume/Tun Freq. welcomed.

Thanks for the help.

/Greg

[MarkMcK]

Just thinking out loud. I was contemplating your treatment in relation to mounting tweeters offset on the baffle rather than in-line as your current speakers are

I hope no one will mind if I do some of my own thinking out loud.

Even two-way designs are pitfalls of complications. Any multi-way loudspeaker will produce uneven or "lobed" off-axis response. One reason most two-ways are aligned vertically is to place the lobing above and below the listening plane. People are more likely to move horizontally between the loudspeakers than move up and down.

The placement decision is made even more complicated by something known as air mass loading. This is something different than baffle step and mainly effects small diaphragm drivers. The size and shape of the baffle effects some tweeters more than others.

Tweeters with flat mounting plates and diaphragms mounted proud of that plate are most effected. The KEF T27 tweeter would be an example. Tweeters that are semi-horn loaded or recessed behind the front plane of their own mounting plates are less effected. The Vifa T27 is an example of a tweeter pretty much independent of mounting baffle influence. The cause of this phenomena is known as surface effect. The same physics phenomena important in air flow induced lift when flying at very low altitudes and downforce in race cars, speed boats, and so on. In the micro world of small diameter diaphragms this phenomenom can be very important. Indeed, the rubber strips mentioned in the vertical arrangement are most likely changing the air mass loading on the tweeter diaphragm and significantly changing its response.

Just thinking,

Mark