We seem to have broken open a hornet’s nest. Hardly had the Wall 150 and 300 been introduced when we started getting inquiries about whether something similar could be built for the Blues Class. Not that, too! was our first thought, but it doesn’t mean what you think. “Not that, too!” would be a nice name for an occasional series in which we introduce assembly suggestions that are not new inventions, but are modified for a new application or installation site. We quickly gave up on the idea when we realized there was much more potential in the wall units than just modifying the occasional assembly kit to be installed very close to a wall. If you look around the assembly-kit and readymade scene, it’s hard to find a speaker like that. This was confirmed by responses from our readers, who encouraged us to come up with more applications for the wall series. These flatfish seem to fill a gap in the product range when people start planning a home theater where they want everything to blend in nicely, from the armoire to the cozy conversation corner to the genuine Picasso hanging over it. The idea that the box takes up less space on the wall than a floor-standing box is also a strong argument, at least for the rear or center speakers. With the available gradient chassis, the Elips, or even one of the other wide-range speakers, it should be possible to create an almost infinitely long street of loudspeaker assembly suggestions with a flat structure, in any sound category. That’s how we came up with the name: Wallstreet.

Right at the start of the new speaker series, we encountered an unexpected problem; we should have used the name Wallstreet 1 for the first two wall-mounted speakers. So we quickly and retroactively added the titles Wallstreet 1 and 2 to the Wall 150 and 300 as well. Now we’re back on track, and we can simply keep on with the numbering. Wallstreet 3 and 4.

Equipment 

We have already gone over the Blues Class and home theater at length in a previous issue, so here we can afford to skip talking about our previous prejudices and focus on what’s important – namely the choice of chassis. It probably won’t surprise you to hear that we couldn’t think of anything better for the Wallstreet Blues than the tried and true SB Acoustics #15, which also breathes life into the home-theater Blues. Still, we didn’t like the idea of putting a copy of the SB 15 or SB 30 into a different cabinet, since its concept includes two subwoofers built into the fronts. Attaching them to a wall would be very difficult. To avoid any unnecessary explanations, we decided on a basic structure using the blueSBox 15 PC, where the SB15NRXC30-4 reproduces the deeper octaves and the SB26STC-C4 is responsible for the upper octaves, with a perfect interplay for quiet and loud notes alike.

That made choosing the tweeter very easy, but we still had some preliminary decisions to make. As we learned from our experience with the Wall 150, there would absolutely be demand for a model of the Wallstreet 3 with higher volume; so we went ahead and included it. Now, the SB15NRXC30-4 owes its last impedance number to its voice coil, which only allows a second chassis to be used when it is connected serially. But that doesn’t achieve the goal of a higher volume with the same amplifier settings; it only reduces the lift. Counter to the principle that every box in a home theater should use the same chassis, we went with its 8-ohm brother; the difference from the 4-ohm type is fairly insignificant in terms of the name, sound and technology. Nonetheless, we included a picture of it next to the text so that we could subtly point out the outstanding construction of the chassis one more time. You can also see the prices for the SB chassis: basses are just under 50 euros, tweeters under 28 euros per piece.

Cabinet

Certainly it is no coincidence that #15 bass mid-range speakers are almost always happy with 10 liters of volume at their backs, even if the construction data differs. That has more to do with the fact that an enclosed space of this size fits onto any shelf. The two SBAcoustics are no exception to this practical rule, and we used them for our wall boxes. Still, it’s a happy coincidence that even the exterior bass-midrange speaker dimensions of the first Wallstreets also work perfectly for the Danish Indonesians. Unfortunately that’s not true for the tweeter, which has a 2-mm difference all the way around. No problem, says our lazy alter ego, we’ll just use the cabinets from the wall applications for our wall-mounted Blues. Of course it’s a shame that we can’t show you any new pictures of the box assembly to fill up the page. Presenting them as allegedly new photographs wouldn’t exactly reinforce our credibility. So we’ll leave it at adjusting the tweeter dimensions in SketchUp, and quickly wrap up the cabinet chapter with the assembly plans for the Wallstreet 3 and 4.



We have summarized the SketchUp files as Wallstreet 3_4-Zip.

Crossover

With good reason, loudspeakers are set up far away from reflective surfaces so that the ear can separate the direct sound from the reflections. It’s also normal to avoid making the baffle board too wide so that the boxes aren’t rejected by most of your family due to their rough bulkiness. It’s not possible to do both for flat wall mounts, since even 10 liters are fairly wide when there’s no real depth available. Moving this type of box away from the reflective surface also contradicts the declared goal of getting them out of the way. So our wallflower gives us two automatic problem areas that can’t simply be glossed over. To demonstrate the effects on the frequency curve, we compared two measurements of the Wallstreet 3 with the blueSBox 15 PC, which has the same equipment but a slightly different crossover.

In the first diagram we see the changes due to the front widths of 36 cm (blue) and 20 cm (red). While the volume increases on the wide baffle board below 1 kHz, the narrower baffle board manifests itself through the shift in the decay on the edge at 3 kHz, which is almost an octave lower for the wall-mounted box. In addition to these changes, the second diagram shows the bass reinforcement through the wall, but also the hook at just under 400 Hz, caused by overlapping the sound waves with the early reflections; this in turn leads to a slight subtraction in this area and an addition directly above it. Thus we will not be bothered by the waviness of the amplitude here; under 30 degrees, the almost natural listening angle for the Wallstreets, the hills and valleys practically disappear (Diagram 3). The tweeter was given plenty of volume so that it wouldn’t sound too quiet under the angle.

The crossover structure of the two Wallstreets is identical, curbing excess volume through the wall and the front using an upstream anti-resonant circuit. Both use the same connection for the mid-range speaker and tweeter, which make the same impedance of 4 ohms and almost identical frequency curves possible without a circuit. Only an additional resistor was needed for the Wallstreet 3 in order to balance out the 3-dB lower sound pressure caused by the halved membrane surface in the centers. For the sake of completeness, here are the branches and total curves for the Wallstreet 3 and 4.

Depending on the room size and volume requirements, various combinations of the Wallstreet 3 and 4 are appropriate. Five Wallstreet 3s, together with a subwoofer, make up a high-quality home theater for the “normal user.” In order to get the maximum volume out of the system, five Wallstreet 4s are naturally better; but the combination of 3 WS4s in front and 2 WS 3s in back isn’t too bad either. In order to allow for every conceivable combination, the phasing was taken into account when developing the crossover. The diagram compares WS 3 (red) and 4 (blue). The deviations in the curves are minimal, and they are not audible.


Since we don’t have any of the usual gluing photos this time, we quickly grabbed the unused camera and extensively documented the crossover assembly, which is not normally captured. In order to avoid taking up too much space with the pictures, we have provided them in small format here. You can also click on them to enlarge.

Sound

One big problem in evaluating home theater sets, admittedly, is our previously stubborn attitude toward modern entertainment with moving images, and our resulting refusal to allow corresponding all-around signal providers into the house. This not entirely unprejudiced view will probably need to be revised soon, since eventually there will be many more people who can be reached through a home theater than through a homage to our ancestral stereo technology. Today’s world can no longer be defined by dualities, even if pure music listening can be a lot of fun with the right boxes.

For now, though, the excuse still stands that we were so surprised by the success of the Wallies we forgot to get a multi-channel amp. Thus we were sincerely sorry that we could only evaluate the constructions using conventional amplifiers. Still, we did move our listening spot to a place where there was wall space available, and we made sure to compare them to adequate compact boxes without any wall influence.

Naturally, the results were not very surprising; regardless of where we stood, our SB boxes were able to represent quiet and loud sounds alike without any tonal changes; they produced the instruments’ attack and decay patterns with the right intensity, as well as the width and depth of the stage in a plausible way. The bass was reinforced by hanging the speaker on the wall, something that was appropriately balanced out by the louder tweeter. That made the effects sound a bit more powerful than with the free-standing compact speakers. The slight dip at 3 kHz was very pleasantly noticeable and there was no annoying hiss in the voice reproduction, even with the kind of loud ambient noise that is often found in movies. At the same time, there was nothing missing in the definition and details when music came out of the Wallstreet 3 or 4.

In this area, we preferred the SB 15 or SB 30 right after switching over because they had to make fewer compromises in terms of early reflections.But two minutes of listening was plenty of time to get used to the different sound, and we almost forgot how it had sounded before. That’s a good sign, because gross discolorations are not minimized by listening longer. On the contrary – once you’ve noticed them, they become even more obvious. It was hard to compare the Wallstreet 3 and 4 with their sisters. Lacking extra cabinets, we were forced to unscrew everything, which correspondingly increased our forgetfulness (in this case, it wasn’t age-related). Still, we believe it is fair to say that the Wallstreet 1 and 2 do their job well, though not quite with the same precision and dynamics as their compatriots. The differences really became clear when we played very well-recorded CDs, which produce the subtlest sounds even without today’s common excessive compression – while the musicians successfully worked to dominate each other. Only the Blues Class can do that.

Technology

Wallstreet 3

Wallstreet 4

The loudspeakers "Wallstreet 3 and 4" are complete and exclusively available from

Intertechnik

Wallstreet 3

Wallstreet 4