NSB project

[bmd]

My high school manufactruing class is working on it's annual prototypes for the thanksgiving market survey, and I am trying to pitch loudspeakers instead of the usual magazine rack or shelf. The goal is to produce a pair costing as little as possible, and that's why I chose on the NSB's.

I was hoping someone could give me some good advice about box volumes for single (full range) and MTM designs, or whatever design is best.

We're hoping to produce between 15 and 30 pairs.

Any advice would be great!

[bill]

I made a pair of MTMs using the NSBs and the 87 cent Onkyo automotive tweeters (no longer available, unfortunately.) My boxes were a bit over 10 liters, which is way undersized, with a 2" diameter by 4" long port. The design is similar to the ultra-scrooge HT MTMs on the NSB project page. If I were to do it over again, I'd use the box volume of Dan's UBHTs. Also, I'd seriously consider using one of the $4 PE neo tweeters. The Onkyo tweeters are diamond-shaped, and I had to make a template to be able to route recesses for them.

Instead of trying to squelch the notorious NSB 7 kHz breakup by doping the cones, I used a conjugate filter, in this case a parallel trap in series with the woofer filter. I might have been better off with a series trap shunted across the drivers.

My design follows the USHTs in that it puts the NSBs in series. This makes it very amplifier-friendly, despite the 4 ohm tweeter.

Total cost for the pair was just under $30, including $8 for a can of spray-on truck bed liner. That includes two Jantzen inductors in each crossover. The caps are non-polar electrolytics, and I saved a few cents on the resistors by buying 10-packs of 1-watt flameproof resistors, each five times the value I needed, and paralleling five to get the correct resistance value and five watts of power handling.

I have no place to post pictures or schematics, but I'll be happy to e-mail them to you. I did the cabinet layouts in BoxyCad, so I even have cutlists. The baffles are 3/4" MDF; the rest of the boxes are 1/2" MDF. If you don't have BoxyCad, you should download it. You will need Excel to run it.

I have not measured the response on these speakers, but they sound quite decent for what they are, and my son is happy with them. They do need a sub, which in his case is a Quatro 15 :-) Again, they'd be much better with a bigger box, but I was working with some fairly tight space constraints (they had to fit on his desk.) WinISD says optimal for a single NSB is 28 liters tuned to about 53 Hz. I think 12 liters at 58 Hz is more like it. Double these for an MTM. You can't really get an optimal sealed box; the closest you can get is about 11 liters for a single driver, but that's 3 dB down at 100 Hz.

HTH,
Bill

> My high school manufactruing class is
> working on it's annual prototypes for the
> thanksgiving market survey, and I am trying
> to pitch loudspeakers instead of the usual
> magazine rack or shelf. The goal is to
> produce a pair costing as little as
> possible, and that's why I chose on the
> NSB's.

> I was hoping someone could give me some good
> advice about box volumes for single (full
> range) and MTM designs, or whatever design
> is best.

> We're hoping to produce between 15 and 30
> pairs.

> Any advice would be great!

[jimt]

> My high school manufactruing class is
> working on it's annual prototypes for the
> thanksgiving market survey, and I am trying
> to pitch loudspeakers instead of the usual
> magazine rack or shelf. The goal is to
> produce a pair costing as little as
> possible, and that's why I chose on the
> NSB's.

> I was hoping someone could give me some good
> advice about box volumes for single (full
> range) and MTM designs, or whatever design
> is best.

> We're hoping to produce between 15 and 30
> pairs.

> Any advice would be great!

I've built a couple of pairs and I prefer an open baffle. They have to be kept at least a few feet from a wall, but they still sound good. I've used the Dayton Neo tweeter with good success, it seemed to be a natural choice.

[kduggan]

> Your not going to get gret bass out of the NSB's but a pair of them is respectable. I have used four Nsb's with a single Dayton Neo with surprising results. Using 4 drivers allows you to keep 8 ohms and raises the Spl into a reasonable range for the Dayton Neo tweeter. If you are interested I let me know and I will dig up the box dimensions and porting as well as crossover. My high school manufactruing class is
> working on it's annual prototypes for the
> thanksgiving market survey, and I am trying
> to pitch loudspeakers instead of the usual
> magazine rack or shelf. The goal is to
> produce a pair costing as little as
> possible, and that's why I chose on the
> NSB's.

> I was hoping someone could give me some good
> advice about box volumes for single (full
> range) and MTM designs, or whatever design
> is best.

> We're hoping to produce between 15 and 30
> pairs.

> Any advice would be great!

[cptomes]

>Your not going to get gret bass out of the NSB's but a pair of them is respectable. I have used four Nsb's with a single Dayton Neo with surprising results. Using 4 drivers allows you to keep 8 ohms and raises the Spl into a reasonable range for the Dayton Neo tweeter. If you are interested I let me know and I will dig up the box dimensions and porting as well as crossover.

I am going to be building 4*NSB/Dayton Neo in the immediate future! I am very interested in crossover specs... I am totally inexperienced at passive crossover design and would love to start with a known working design and experiment from there. I know I need more medrange/midbass than two NSB can put out for my living room. I may need to add a shielded 8"-12" on each side after I do some testing. I've found that crossing over to the sub higher than ~100Hz just doesn't sound good to me, and the NSB has essentially nothing below ~125Hz.

I have the three NSB MTM xovers I have found in various projects pages, and all the various different tweeters and crossover components to build all three. I have 10 each of the Onkyo -702 and -776 tweeters, and a pair of the Dayton Neo front-mount for testing. I am currently finishing up a 8*NSB/Dayton Neo project using "shot in the dark" 2nd order crossovers. It will probably suck, but the inductors are common to another project I may try so they won't go to waste. That one also has a 2nd order l/h pass for a separate woofer box, which may also turn out to suck. But hey, if I never start this kind of experimenting I'll never learn.

[cjd]

Unless you go open baffle (imagine bass roll-off starting ~150Hz) they want BIG boxes. I have MMTMM's in my HT and IIRC the mains are like 14" deep, 6.5" wide, 36" tall, or somewhere in that realm. Been a long time since I modeled things up.

I have stuff worked out with both versions of the Dayton Neo as well as the diamond-shaped Onkyo tweeter. Also somewhere versions with one of the smaller T-B tweets, but the price on that makes it unsuitable compared to the current options (at the time, it was the best priced option for me).

I've shared it all at various times before, but the easiest thing at this point is to e-mail me with specifics.

C

[unknownuser]

> I am going to be building 4*NSB/Dayton Neo
> in the immediate future! I am very
> interested in crossover specs... I am
> totally inexperienced at passive crossover
> design and would love to start with a known
> working design and experiment from there. I
> know I need more medrange/midbass than two
> NSB can put out for my living room. I may
> need to add a shielded 8"-12" on
> each side after I do some testing. I've
> found that crossing over to the sub higher
> than ~100Hz just doesn't sound good to me,
> and the NSB has essentially nothing below
> ~125Hz.

> I have the three NSB MTM xovers I have found
> in various projects pages, and all the
> various different tweeters and crossover
> components to build all three. I have 10
> each of the Onkyo -702 and -776 tweeters,
> and a pair of the Dayton Neo front-mount for
> testing. I am currently finishing up a
> 8*NSB/Dayton Neo project using "shot in
> the dark" 2nd order crossovers. It will
> probably suck, but the inductors are common
> to another project I may try so they won't
> go to waste. That one also has a 2nd order
> l/h pass for a separate woofer box, which
> may also turn out to suck. But hey, if I
> never start this kind of experimenting I'll
> never learn.

Actually, the best, and the cheapest way to learn is to get yourself a good book, calibrated microphone, microphone amp, crossover software with built-in measurement utility software. It will set you back around $300-$400, but in the long run, you'll save tons on crossover parts and frustration.

If you have a cheap speaker that you can kick around, you can use them as you test setup. Use your crossover design software to see how different crossover topology will affect the output. Blindly trying different design is NOT the way to go. Plus, you won't understand why some design sounds good, while others (using the same drivers) sound horrible.


(Originally posted by: kyle)

[cptomes]

> Actually, the best, and the cheapest way to
> learn is to get yourself a good book,
> calibrated microphone, microphone amp,
> crossover software with built-in measurement
> utility software. It will set you back
> around $300-$400, but in the long run,
> you'll save tons on crossover parts and
> frustration.

> If you have a cheap speaker that you can
> kick around, you can use them as you test
> setup. Use your crossover design software to
> see how different crossover topology will
> affect the output. Blindly trying different
> design is NOT the way to go. Plus, you won't
> understand why some design sounds good,
> while others (using the same drivers) sound
> horrible.

I really do understand the physics. That's why my designs to date have all been active crossover and the passbands have been ~1 octave within the published specs for the drivers used. That way I can just ignore passive crossovers and their interactions with the drivers. I have avoided getting into passive designs to date because I didn't want to buy the equipment and software needed to do the job. I think I'm going to just have to bite the bullet and get the standard setup now.