Micro 3-way driver selection - help!

[Gveto]

Greetings all.

Soon I will be embarking on a micro 3-way project that (for the moment at least) will use a downfiring Tang Band W4-992S 4" subwoofer, a Hi-Vi B3S, and a Dayton ND20FA-6 3/4" tweeter.

Right now, I am set on the using the TB sub if only for dimensional reasons. The Hi-Vi drivers seems to be the right choice for my design, but I am wondering about the use of the Dayton tweeter.

The emphasis on this design is firstly size, and secondly on dispersion. The speaker will be used casually in a living room placed on two end tables, or the like. It is being designed as a 'party' speaker to be enjoyed by guests throughout the room, both sitting and standing. (No critical listening here.) The tweeter will be situated on the top of the enclosure and angled towards the front at a yet undetermined angle.

It occurs to me that tweeter will not be able to play low enough to ensure good dispersion. Physical design considerations are in play with the choice of the tweeter. While I have enough baffle space for a larger flanged tweeter, the press fit tweeter appeals to me since using a router to flush mount a tweeter will be difficult. As always, price is a consideration as well. I would like to keep the price of the tweeter under ~$15.

Any advice regarding my driver selection would be greatly appreciated.

Also, I am in need of SPL and phase data for the Hi-Vi B3S. I have digitized the manufacturer's SPL graph, but it lacks phase information. I planned on sending an email to John Krutke about this, but the email link on his site appears to have been removed. Perhaps someone can direct him to this thread.

Also, will I have any issues regarding the TB and Hi-Vi sharing the same airspace?

Thanks,
Dan

PS The attached PDF should give a good idea of the basic design.

DAYTON ND20FA-6 3/4" NEODYMIUM DOME TWEETER:
http://www.partsexpress.com/pe/showd...number=275-030

HI-VI B3S 3" SHIELDED ALUMINUM DRIVER SQUARE FRAME:
http://www.partsexpress.com/pe/pshow...Number=297-427

TANG BAND W4-992S 4" SHIELDED SUBWOOFER:
http://www.partsexpress.com/pe/showd...number=264-824

[sdclc126]

You don't need to cross the tweeter low - cross it high - the B3S is good up to 10k and very accurate - so exploit its merits and use it as a wide midrange - dispersion will be less of an issue.

Since the speakers are not intended for critical listening, I see no need to separate the mid & woofer enclosures; if you do make sure you maintain proper volume for each driver.

As these are party speakers, what sort of SPL levels are these intended for, and what is the room size? The B3S is rather inefficient and cannot handle a lot of power - this design may not be ideal for "loud" parties/dance music etc., but OK for background music at cocktail type parties.

You might want to consider a more efficient design, possibly with 2-way satellites and a larger separate sub, if the room can accomodate.

[Gveto]

Softdome,

Your comment about the high crossover frequency solidifies my original intention for the design. The dispersion issue was a bit of an afterthought; I'd like to avoid high frequency beaming of the 3" so there aren't any "hotspots". The speaker will be used at low volumes to entertain guests in the room - no dance music here!

Keeping the design small and simple is a priority here. The speaker is not for me, but rather my parents so I've got to keep it within they're low profile specs or I lose the fun of designing and building the speakers!

As for the room - It's not a big room but it does have a 'live' quality due to a high ceiling and hardwood floors.

Thanks for the reply.

Dan

[sdclc126]

You're welcome.

Looking at the response graph for the B3S, it doesn't look like it starts to lose much off-axis until about 5k, so you'll probably be fine at least up to there. This should be ok for the Dayton tweet too, considering the speakers will not be run at high SPL.

After you went into more detail regarding the room and use of the speakers, a couple of thoughts occurred to me -

First, the reflectivity of the room may be an asset here - dispersion and perceived efficiency will benefit from surface interactions...

Second, in order to exploit this potential you might want to consider placing the speakers up high - a room full of people will absorb a lot of sound - if the speakers can fire over their heads much of their energy will reach the walls and ceiling first, and reflect back to all those pairs of ears.

One thing for sure - with the B3Ss carrying the lion's share of the sound reproduction, you can expect to get a lot of compliments, and inquiries, about your high fidelity, low cost & size loudspeakers! Please post some pics of the project - I'd like to see them. I'm considering some very compact surrounds for my HT with the same mids & tweets!

[augerpro]

Hi Gveto! These mini systems sure aer popular. My first DIY is going to be very similar to yours with the same drivers. I'm just waiting on a microphone to get started.

Is flush mounting a problem for you? Because that flange on the B3S looks like trouble to seal and keep from vibrating. I chose B3N/M3N because of this.

Choose you XO frequency based on the ctc distance. For example a 3.5" ctc gives a Frequency of 3858 Hz, so you'd want to cross no higher than this, preferably lower. The closest you could get with those is maybe 3", not much less.

I'm going MTM to up the SPL capability of these speakers. But they do get to a reasonable level for background music with just one driver too. Of course mtm will have a smaller sweet spot, maybe too small for your needs. Anyway I don't think wide dispersion is the answer to low sensitivity drivers, in fact just the opposite. More directivity means more power at the listening position. Although that position may be smaller, compromises...

if you just need them as "elevator music" for small groups i don't think you'll have a need for more SPLs though. HT or a house full of people would be different.

I should have my mic soon, so bump this thread a week from now and I could email you my measurements.

[Shaun]

These cost $5.

http://www.apexjr.com/speakerstuff.html

Could be another option for your tweeters.

Edit: see bottom of page

[Gveto]

Originally posted by sdclc126

First, the reflectivity of the room may be an asset here - dispersion and perceived efficiency will benefit from surface interactions...

Second, in order to exploit this potential you might want to consider placing the speakers up high - a room full of people will absorb a lot of sound - if the speakers can fire over their heads much of their energy will reach the walls and ceiling first, and reflect back to all those pairs of ears.

My thoughts exactly regarding the live room helping to fill the sound out.

Unfortunately, the placement of the speakers is non-negotiable. Reffering to the attached PDF in my original post, on the side view you can see the crossover 'shelf' that will be mounted below the TB sub. This shelf will be a shaped piece of 1/8" plexiglass on which the crossover components will be mounted. (External crossover. ) Rubber feet will be screwed to the bottom of the crossover making this a tabletop - only design.

Originally posted by augerpro

Is flush mounting a problem for you? Because that flange on the B3S looks like trouble to seal and keep from vibrating. I chose B3N/M3N because of this.

Choose you XO frequency based on the ctc distance. For example a 3.5" ctc gives a Frequency of 3858 Hz, so you'd want to cross no higher than this, preferably lower. The closest you could get with those is maybe 3", not much less.

...

I should have my mic soon, so bump this thread a week from now and I could email you my measurements.

Thanks for the heads-up on the B3S frame issue. I agree with you and after some thought (but not much...) I'm going to change my driver selection to the B3N as well. Originally, the square frame driver was picked because of baffle size limitations, but since then the design has ballooned in size, and the B3N will work just fine now.

As far as flush mounting is concerned, if you look at the blueprints, you can see that flush mounting a tweeter would be a PITA because of the angled baffle. Using a holesaw or drillbit to make the hole for the Dayton tweeter seems to be the way to go in terms of ease of construction.

I'm not going flush mount the B3N for a couple reasons, one of which being that I intend to use a thin baffle on the front and there would simply not be enough material to countersink into well. Also, from some reading I've done, flush mounting drivers like the B3N is far less critical than, say, a dome tweeter with a large flange. If anyone has data to refute or back that claim up, I would be interested in seeing it, though.

Asthetically, the B3N will be behind grill cloth so the flush mounting would not be seen.

As far as the measurements go, I've decided to do this the right way and build the enclosure first, measure the drivers in cabinet, and then design the crossover from that. I too will be a novice at measuring speakers this way, so perhaps we can trade data to ensure that I'm doing everything right!

Thanks for the comments!

When the design is finalized (nearly so right now) and the components are purchased, I will start a design/construction thread with lots of pics.