Zaph|Audio

Measurements

Frequency Response - Combined Anechoic

This is merged from several plots to get an accurate representation of the full range. Basically, it's far field merged with a nearfield plus diffraction sim, then summed with the port response. Pain in the *** to do but generally pretty accurate. The response is similar to many cheap Asian drivers, with a cliff in the midrange. For cheaper drivers, less R&D is invested to find cone geometry and materials that give smooth response through the upper midrange. I would call the stock response curve "not very good". The hole in the lower treble is clearly audible as missing music information, just as the peak at 800hz makes female vocals edgy. Bass tuning is on the warm side, as this is a higher Qts driver that would probably be better used in a sealed enclosure than vented. Still, this is a $20 speaker, and for that it's not bad at all. I've seen worse at a few times the price. Sensitivity is relatively low for this system.

Frequency Response - @ 70, 80, 90 and 100dB

The is the frequency response from an MLS impulse at multiple levels. Things don't really change until around 100dB, when there's a few minor differences here and there.

Frequency Response - Off axis: 0, 15, 30, 45, 60 deg

These off axis plots are horizontal, not that it matters much with a coaxial. I would declare the crossover point to be higher than optimum for the woofer, considering a broad null begins to show up centered around 3kHz where the woofer's power response rolls off. Of course, crossing the tweeter much lower would probably result in gross distortion, so I'd generally take poor power response over a distorted lower treble.

Harmonic Distortion - Sample 1

These harmonic distortion plots are taken under the same conditions as my 5.5" driver test group although in this case it's a system plot including the crossover and the tweeter. It looks relatively decent for a driver in this price range. The flat 3rd order through the midbass makes this speaker sound a little thicker and muddier than many better designs, but it's not too bad. Note the drop in HD as the tuning frequency nears. Obviously, this speaker's real isssues are in it's frequency response. A note about the enclosure rattle problem - I thought this was interesting so I posted it. I had taken the binding posts off and set them on top of the enclosure. They seriously rattled at 800 hz and this image shows what that looks like on the HD plot. It appears this enclosure's weak spot is the top and bottom.

Cumulative Spectrum Decay

Nothing unexpected here based on the frequency response, but I grabbed one anyway because I like all the pretty colors. :)

Modifications

Insignia NS-B2111 add-on dual notch filter

Schematic, transfer function, frequency response and impedance are shown above. This is just a set of notches I threw together. This can be hooked up externally in series with the positive terminal, or it can be mounted inside on the bottom, spliced into the positive wire.

In general, the notches favor dips over peaks because dips are less noticable, and power response does play a factor. A mild rise in the 3kHz area and a peak at 15kHz flatten out slightly off axis. This puts the design axis around 5 degrees or so.

The notches are designed to go before the crossover. A quick splice into the wire connected to the positive terminal should do it. That's certainly not the only way to improve this system, but I chose the way that allowed the stock crossover to remain in place and unmodified.

In case it's not obvious, tube amps should stay away from this due to it's wild swinging impedance.

Maybe in the future I'll get individual response curves and individual distortion plots so I can completely rework the crossover, but for now this set of notches might help someone who doesn't want to even open the box up. There was some talk on another forum about using this speaker as the system for a DIY crossover design contest. That might be fun.

This box was sealed to help reduce a little boom due to the tuning of the port. This comes at the expense of a little power handling and extension in the 60hz area. The system is best used with a sub anyway. Oh yeah, black socks work best for stuffing the port - you can push them in a ways so you can't see them. If you need your socks, you might want to just glue a disc onto the back of the port.

Additional stuff that could be done: There could be some stiffening added to the top and the bottom. Better damping could be used also, and given the thin walls, preferably something with a mass loaded layer such as whispermat or sonic barrier. I could toss the driver, peel the plastic veneer off, add a 1/4" layer of MDF all the way around, veneer it and use the enclosure as a great base for something else. The entire crossover could be yanked and redone rather than the add-on notches I have shown. I'll leave these modification ideas to other people.

The Craze

Words fail to describe the feeding frenzy and massive number of forum postings regarding these speakers. The "normal" selling price was $50 per pair, making these generally regarded as a "good deal". Of course, the meaning of "good deal" is subjective. But when they went on sale for $35, the feeding frenzy only got worse. Every audio forum had a post (or several) with a hundred replies underneath it. Audio Asylum had the largest quantity of postings, most of which were moronic. In other words, normal for Audio Asylum.

Opinions on these speakers ranged from "My god, These sound incredible and I'll never DIY again!" to "These are nothing more than white van crap and even for $50 you got screwed". IMHO, niether are right.

Here's a few bits of my opinion - For $50 per pair you can't get anything better. On the other hand, only spending $50 on your speakers is setting your sights pretty low. If this is your primary speaker of choice, the chances are that you just don't care about high fidelity, you can't tell the difference between good and bad sound, or you don't have much money to blow on speakers. This speaker seems to be marketed specifically to folks who fall into at least one of those categories, or more likely all three categories.

The DIY'ers created a couple more categories - Those who are curious exactly what $50 can get you from a high production Chinese manufacturer, and those who want to turn cheap garbage into something listenable for a few bucks worth of mods. I think I personally fall into the curious group, though I did give an add-on filter a shot. As an engineer with some background in manufacturing, I'd love to see what the production line looks like.

Links

There's more but this is all I care to post. Danny Richie's crossover mod is a little on the expensive side. I wouldn't use a foil inductor in any project, much less a $25 Best Buy speaker, but that's just my personal preference and opinion. But I'd advise you to take a look at his cabinet mod using water putty. That should stiffen the walls nicely. DLR's driver mods appear to be a step in the right direction. (note that it's not compatible with my add-on filter) AJ's got the best pictures of the insides that I've seen, and he tends to be a big fan of coaxials.

Well that's a wrap for this page. The Insignia frenzy has subsided a little bit.