Some qualifications is in purchase. Applying a big-diameter woofer endows a traditional two-way speaker with potentially large sensitivity and extended very low frequencies. Nonetheless, the big woofer’s radiation pattern narrows at the top rated of its passband, whilst that of a tweeter mounted on a flat baffle is at its widest at the bottom of its passband. Even if the push units’ outputs are very well-matched in the speaker’s on-axis response, this discontinuity in the speaker’s off-axis conduct outcomes in an in-space stability that will audio brilliant. This is why favorably reviewed two-way patterns tend to use a woofer with a 6.5″ or even scaled-down diameter.
The SourcePoint 10 was developed by Andrew Jones, a properly-highly regarded veteran loudspeaker engineer with remarkably regarded designs from KEF, Infinity, Pioneer, TAD, and ELAC in his resumé (footnote 1). Andrew, who is now celebrating two a long time with MoFi, has certainly carried out a little something various with his initial design for the organization.
The SourcePoint 10
The very first matter you see about this speaker is that the sculpted, 2″-thick entrance baffle has a solitary, centrally positioned generate device with a 1.25″ soft-dome tweeter mounted concentrically at the middle of the 10″ woofer’s paper-pulp cone. The second factor you discover is that in its place of a typical half-roll rubber encompass for the cone, the woofer, which is reflex loaded with twin ports on the rear panel, works by using an previous-fashioned corrugated encompass. The 3rd issue you detect is that this is a substantial, large structure for a standmount it measures 22.5″ × 14.5″ × 16″ with an inside quantity of 50lthat’s 13.2 gallonsand weighs just around 46lb.
Andrew Jones and MoFi’s Jon Derda frequented the day right after I unboxed the SourcePoint 10s. As they organized to established up the speakers in my home, I asked Andrew why he experienced settled on a two-way concentric design rather than a a few-way and why, thinking about that, he had decided to use these types of a massive woofer (footnote 2).
“Very considerably 100% of the layouts I have accomplished with concentric motorists have been 3-way. And that is because with a concentric driver, you will not want the cone relocating way too significantly. The much more motion you allow it to have, the more compromises you’re getting, mainly because you get amplitude modulation. … You also need a greater surround, [which] disrupts the wavefront from the tweeter, [and the] delayed reflection off the cone will cause differences in the frequency reaction.
“The trouble [with a three-way] is the complication, the additional cost, … and hoping to decide the frequency where by you should cross more than” from the woofer to the midrange. “Must it be as lower as 80Hz? That would be quite, extremely high priced to do in conditions of components charges for a passive crossover. And how significantly down do I want to acquire that midrange, specifically offered its measurement and all the things I need to do to management how very well it works as a waveguide for the tweeter? So, could I do a two-way concentric? Since if I am concerned about minimizing motion of the cone in a concentric, you can find only two strategies to do it. A person is to restrict the frequency ranges, which is what you do when you change it into a three-way. Or you make the woofer so significant that most of the time it would not have to move rarely at all. Going from a regular 4.5″ or 5″ driver to a 10″, I have got practically 4 moments the region and a quarter of the motion, which is substantial.
“Because 1 of the briefs from MoFi was to have excellent, impactful, and extended bass. As well, as it’s having again into style to have large woofers, it would be pleasurable to get the job done with a massive woofer. That could be awesome, but I would under no circumstances finished just one before.”
I asked how, in a two-way design with a 10″ decrease-frequency driver, which will start out beaming at a rather very low frequency, does he match it to the wider dispersion of a tweeter?
“When you put the tweeter in a waveguide, it truly is not that it can be narrowing the directivity in all places. It is really narrowing it at the decreased frequencies, which is exactly where you have the dilemma in matching the directivity to the woofer. So now you happen to be heading to slim it progressively as you go down in frequency, correlating with how considerably sensitivity you achieve owing to the waveguide loading at the lower frequencies. With a fantastic waveguide, you can arrive at about +10dB of on-axis output compared to no waveguide. And that’s a massive gain for doing the job the tweeter mainly because 10dB is a 10th of the energy enter you have to have in a essential variety the place you can find even now a lot of power in the music. The waveguide … minimizes the strength enter, the thermal compression, and the tour need [of the tweeter].
“So if you can engineer a small resonantfrequency tweeter, you can run it down to a decreased frequency”it’s 1.6kHz in the SourcePoint 10”since it is jogging at a reduced tour as opposed to not possessing a waveguide, which extra than can make up for the excess extension that you want to cross in excess of the tweeter decreased. And with a 10″ waveguide, the improvement in effectiveness or sensitivity and the reduction in tour much more than make up for the simple fact that you are crossing about at 1.6k. It permits you to get a pretty excellent, progressive, dependable off-axis overall performance.
“When the waveguide also needs to be a woofer or midrange cone, you have acquired to make a decision what is the ideal shape for it to act as a waveguide and what is the most effective condition for it to act as a cone, with controlled cone resonances. You hope that it is the exact form. So there’s a selection of sizes and materials and anything else to optimize each the shapes concurrently. So I commenced designing waveguides and obtaining them 3D-printed to see, what ended up the directivity traits? I arrived up with a form that seemed to get the job done quite very well. So the subsequent thing was, alright, so now I have a cone which is likely to operate and need to have a encompass. I knew I couldn’t have a fifty percent-roll encompass simply because that would disrupt the [tweeter’s] wavefront. So it is got to be a single of these corrugated surrounds like they use on professional speakers.”
I questioned Andrew why he experienced picked out a paper cone for the woofer. Would not a 10″ paper cone break up at a low frequency?
“About 3kHz. It’s extremely easy up to that frequency if you have the suitable curvature and the ideal pulp. So I tooled up some cones, tooled up some surrounds, bought a sample crafted, which seems easier than it essentially was. … It took a long although in advance of I experienced nearly anything that I could start listening to.”
We discussed the MoFi’s gentle-dome tweeter, which, as very well as getting larger than standard for a two-way style, has a rather significant surround. Andrew defined that the encompass acts as a ring radiator, emitting sound. He mentioned that with a traditional tweeter, the surround’s output at quite substantial frequencies may nicely be in the opposite polarity to that of the dome, resulting in a decline of output. “I knew I preferred a a bit more substantial diameter, 1.25″ instead than 1″, with a large roll surround, since that presents you excess functionality at the reduce frequencies. Counterintuitively, if you place a broader roll encompass on the tweeter, you essentially strengthen HF response. You imagine it would interfere and reduce off previously, but it will not it in fact extends it. … [T]he phases will be additive up to a increased frequency.” Andrew mentioned the SourcePoint 10’s tweeter goes out to beyond 30kHz.
Footnote 1: See my video clip interview with Andrew Jones right here.
Footnote 2: A white paper on the style of the SourcePoint 10 can be downloaded right here.