Flush Mounting Focal Shape 65 (passive radiators on sides)

[beachvibes]

First poster here so please bear with me. I’m in the process of designing a RFZ CR in a new space. I had never considered the benefits of RFZ and flush mounted speakers until stumbling onto this forum. I have a pair of Focal Shape 65’s which have passive radiators on the sides and I was wondering if it was even possible to flush mount these? I’ve read here on this forum of people getting good results with rear ported speakers by adding extra space in the rear of the box. Would this apply to the sides of the box in my circumstance? My room is 15ftx10’4”x8’ (lxwxh).

Thanks!

Brent

[Soundman2020]

Hi Brent, and Welcome!

I have a pair of Focal Shape 65’s which have passive radiators on the sides and I was wondering if it was even possible to flush mount these?

That's a very interesting question, actually! Hmmmm... My first guess would be "Yes, you can soffit mount them", but I'd have to think about it a bit more, and look at how they work, to be certain.

Since those are passive radiators, not drivers, I can't think of any good reason off-hand why they could not be treated in the same fashion as a rear passive radiator, and in that case, it should be possible.

So my answer would be a guarded "I think it should work, especially if you will be using those with a sub, to fill in the low end".

Probably the biggest issue would be shaping the front baffle of the soffit to match the curved shape of the speaker itself, but apart from that, I don't see any great problems with it. The soffit would need to be designed properly to deal with the side-firing passive radiators, which will need some unusual mounting, but in general, I think it would work. As long as you design the soffit to deal with those issues, then I can't see why there would be a problem.

I had never considered the benefits of RFZ and flush mounted speakers until stumbling onto this forum.

You are really lucky that you did find us! Because RFZ is (in my opinion at least), the best concept out there for control room design. Pretty much all of the rooms I design these days are RFZ based, and the benefits are spectacular, when done properly. So far, I've never had a customer saying that he hated his room and wanted to take it apart and re-build it: on the contrary, people tend to love their RFZ rooms, and would never consider any other style, after experiencing them.

Here's some links to threads of RFZ style rooms that I gave designed and are current in various stages of completion, with comments by the owners:

the corner control room thread

thread about Steve's high-end control room in New Orleans

thread about Studio Three Productions' studio

You can see that they are pretty pleased with the outcome.

My room is 15ftx10’4”x8’

Your room is about the same size as the corner control room, so you should be able to get similar results. If you post more information about your room design, folks here on the forum can probably comment on that, and suggest improvements.

- Stuart -

[beachvibes]

Thanks for such a speedy response. This all sounds great! Those links were very helpful.

I’ve done some drawings to scale and ray traced to make sure there were no reflections from the side walls. I’ve yet to decide what to do with the ceiling. From what I can tell everyone here prefers Sketchup drawings? I don’t know if there is a way to export files through the free version. I would be happy to provide some hand drawn scale drawings though. That would be extremely helpful.

I know very little about the actual construction of soffit mounting speakers other than the diagrams I’ve seen here.

How snug would the top of the box need to fit the curved profile of the top of my speakers? Could I fill the curved space with some kind of dense foam? I think we are talking about less than an inch to make up for the curved profile.

How “permanent” is a soffit design? Is it something I could salvage and move 2 years down the road if I want to move to a new room? This is a 2 year long commercial lease and I may or may not want to move at the end of the lease.

If I do not end up going for a flush mounted system, what alternatives do I have for a good RFZ CR? I’ve heard the Shape 65’s perform well directly in front of walls due to the passive radiators on the sides.

I’ll post some of my plans tomorrow when I have some free time.

Thanks!

[Soundman2020]

From what I can tell everyone here prefers Sketchup drawings? I don’t know if there is a way to export files through the free version.

Don't use SketchUp Free! It is a really lousy attempt to create a web-based version of the actual program. You can still down-load the REAL thing, which is called SkecthUp Make 2017. It is actually usable, and you can export files from it. SketchUp Free is a bad joke. Don't waste your time. As you noticed, they make you jump through hoops top export a file...

How snug would the top of the box need to fit the curved profile of the top of my speakers?

It would need to follow the curve within a couple of mm (maybe about 1/16"). You need a fairly tight fit (small gap), and the gap should really be sealed. Some people just caulk the gap, others put soft rubber strips in there, but not foam: the typical "foam in a can" that you buy in hardware stores is very light weight: no mass at all, and dries hard and brittle. You need something soft and flexible for that gap.

How “permanent” is a soffit design? Is it something I could salvage and move 2 years down the road if I want to move to a new room?

You can if you build it that way! It could be designed as a group of several parts that are bolted together, and could then be taken apart and carried away.

This is a 2 year long commercial lease and I may or may not want to move at the end of the lease.

Realistically, it will take you many, many months to design and build your place.... I would be surprised if it is finished inside two years, so you might want to get an extension on that lease right now! Realistically, it takes about 3 to 6 months for the average first-time studio builder to learn the basics of acoustics well enough that he can design his own place, then another three to six months to actually design it, then another six months to a year to build it. Those are very typical timings from forum members. If you wanted it built faster than that, you'd need to hire a studio designer to design it for you, then a contractor to build it for you, and even then it likely would not be done in less than six months.

If I do not end up going for a flush mounted system, what alternatives do I have for a good RFZ CR?

If you don't soffit-mount your speakers, then it isn't an RFZ design! The actual RFZ spec has the speakers flush-mounted as part of the design concept. Having said that, you could build a room with angled front wall sections that mimic the shape of an RFZ room, then just mount your speakers on stands directly in front of those angled sections, but it would not be RFZ, since you would still have all of the artifacts that flush-mounting eliminates. It would work, but with caveats... it would not be as good as an RFZ style room.

I’ve heard the Shape 65’s perform well directly in front of walls due to the passive radiators on the sides.

I've heard NS10's "perform well" on meter bridges! But I would never use that setup as my main monitoring.

What flush mounting gets you is this:

1) It eliminates the power imbalance problem (or "baffle step response" issue)
2) It eliminates the major SBIR artifact caused by the front wall
3) It eliminates the edge diffraction problem
4) It eliminates several other reflection and comb filtering problems
5) It extends the low-end response of your speakers
6) It tightens the bass very much
7) It looks cool!

... and a few others too. If you don't flush mount your speakers, then you WILL have all of those issues still, simply because the speaker is in the room! Just having the speaker in the room causes all of those. By flush-mounting the speaker, you have effectively removed it from the room: it is no longer "in" the room, so it is physically impossible for it to cause any of those artifacts associated with the speaker being in the room.

I’ll post some of my plans tomorrow when I have some free time.

Cool! Looking forward to seeing that!


- Stuart -