New member, 1st project, bipole NS3-4ohm wired in series for 8ohm output, need help!

[josbroder]

I've been reading this site "religiously" for all of my questions on how to build my own speakers. Most of my questions have been answered just by searching and reading threads, but I just decided to take the plunge and get some first hand advice if anyone is willing to help.

I want to build some bipoles, and I just bought some https://www.madisound.com/store/prod...oducts_id=1372 (NS3 4ohm) speakers from madisound and, though they haven't arrived yet, I'm realizing I was naive, to say the least, on how this build would work.

I read through squib's build Need advice for 1st project (Aura NS3) , as well as several others, and it was very helpful. I want to build something similar, but I think I want to keep it sealed. Also, he used 8 ohm and wired them in parallel and I bought the 4ohm model and want to wire them in series for 8ohm.

I would be willing to try placing both speakers on the front baffle, but I'm more intrigued by bipole.

I was thinking of a dual sealed enclosure, (2.6 liters each) isolating one speaker from the other. Would this still require a filter on the back speaker?

Any filter design I would need help with. I am very new to this and still don't understand how wiring it would work exactly.

After reading about problems with using hardwood, I think I'll stick to MDF, or something easy, and then wrap it with something pretty.

Any help would be much appreciated, and I apologize for my lack of knowledge on the subject. I've just recently gotten interested in building my own speaker. I had no idea what I was getting myself into. But, having dipped my feet in the water, I want to jump in and not get out to buy factory speakers again.

[picowallspeaker]

Hello ...well ,the best thing to do when the speakers arrive is to mount them in a box
So ,if you figure out how to connect two speakers in series , there won't be any problems in making any notch filter for them...Wait ! If they are connected in series (as in parallel..)
they have to be considered as one speaker (electrically ) , so you can't apply a filter to one leaving the other 'alone' . One thing you can do -of course I'm thinking you are using a subwoofer with them- is to mount them on the front baffle , wired in series ,with a capacitor across one speakers terminals . In this way ,only one would emit the trebles .
If you decide to do a bipole , you can make the two chambers with a diagonal panel ,so the internal reflections are minimized . Or you can omit the dividing panel and try a dipole , with drivers wired as in push-pull . Once you have the speakers....

[josbroder]

Thanks for the quick response.

I'm perfectly willing to add the second speaker to the front baffle, and yes I will be adding a sub, but not yet. So, if I put the filter https://www.madisound.com/store/prod...roducts_id=486 (just a possible filter I could use I assume) between the terminals on one speaker, while in series, it would omit high freq. in that one alone?

If I did this, I would make it one sealed enclosure (5.2 lit. found by Winisd).

[Saturnus]

I would go with one sealed cabinet to avoid the 2 drivers being unequally loaded. And having them in one enclosure would also make sure that any mechanical differences, as there always will be because of production tolerances, are cancelled out, and they will behave like one driver with the average parameters of both drivers. In effect it means that the pair will probably be closer to the exact manufacturer specification than any random single driver of the same production run ever will be.

The most significant advantage of a bipolar speaker is that it does not need a bafflestep compensation as long as the box seen from above is a rectangle* the back driver will always start to augment the front driver at precisely the same frequency as the baffle step would normally occur. This is a physical necessity that works as long as the back driver is allowed to produce up to SQRT(PI)*Fbf.

The second advantage is that above this frequency it behaves in much the same way as regular dipole but with a much larger "sweet spot" because it's practically omnipolar, and therefore in theory will create diffuse field response any place in the room. Some don't like this effect though, or at least likes to tame it, and here you can do as suggested above and low pass filter the back driver as long as you maintain the minimum working frequency as described above. Note that doing this will necessitate making provisions for internal reflection which are inherently impossible with a true bipole.

*actually, any convex quadrilateral shape is fine. Rectangles are just the most common.

[borispm]

Hi guys,
I have built something like that. IMHO sealed is the way to go.
My Bipole Aurasound NS3
The bass reflex makes the puppies sound disorganized, and it's hard to recommend.
4L is perfectly fine IMO.

[planet10]

2 points.

1/ to roll off the back driver, when they are wired in series you need to shunt that driver with a capacitor. If you use an inductor across the driver terminals it will roll off the lows

2/ the perfect bafflestep compensation is only when the speakers are on the sides. To approach this ideal, it is best to have the cabinet wider than deep and you need to listen with a toe-in. Listening on axis will cause a dip (the higher the depth to width ratio the deepr the dip) just below the baffle step (ref: Svante)

dave

[Saturnus]

Just to expand on the above point 2 from planet10.

Experiment with off-center driver placement. Only for a true square speaker is the optimum placement equal to the center, optimum in this case is also equal to worst possible but it will depend heavily on drivers. The wider the front/backs are compared to the sides, the more the drivers needs to be off-set from center.

[planet10]

One can download Svante's Edge software to work out optimum driver offset, but it being Windoes only (i don't do windows) i usually just use the golen ratio to determine offset.

Make sure you make mirror imaged pairs.

dave

[chrisb]

probably a good idea to use a combination of GR / irrational number ratios for offset in both directions on any baffle close to equal H/W aspect.

[josbroder]

Wow thanks a lot for all the advice. I've been at work all day thinking about every possible solution to this little speaker. I used the GR for offset in the vertical direction in my design, but not the horizontal. If I use the GR for all dimensions achieving 4 liters total I get 6.25" W X 10 1/8" H X 3 7/8" D (interior dimensions). I'll call it my GR build . Then I offset the driver 6 1/4" up and 3 7/8" over. Then should I line the rear driver with the front?

For the cap, what kind should I get? This is where my knowledge on the subject close-lines. I still haven't figured out how to model crossover designs in winisd. Should I just buy several, since they're cheap, and experiment?

You guys are awesome, by the way. I try to explain to my friends why building your own speaker is so exciting, but I don't think they get it.