Configuring third party subwoofer amp for Pipettes and Subette

[ipetruk]

Hi,

I have a set of Pipettes and a single Subette. I have not yet purchased Sublime, maybe it will happens someday later.

I am trying to use https://fosiaudio.com/products/subwoofer-amplifier-m03-300watts-mono-amp-full-frequency-and-sub-bass-switchable-amplifier with Subette. It has a full monoblock mode and subwoofer mode, where you can tune the cutoff frequency. The problem is that both volume and cutoff knobs are unmarked. They don't have any numbers. I do not know where 70 Hz is that you recommended with Sublime. I do not know how many watts the volume knob gives me. So I have got these:

https://www.amazon.com/dp/B00S8XY2W8

They in theory should have eliminated a single variable out of equation and I would have only have to tune to volume knob. The amp can give 200W with extra power supply, so probably a 160W without it. Plus it is source is my integrated amp pre which is usually operated at 50% of the volume for Pipettes. If power is logarithmic, does it mean that this sub with 50% volume at pre should always operate at less than 30W (roughly), right?

Well, not so simple with those RCA plugs. They have 12dB/Octave slope and it is not documented what slope Sublime has. When I use them via Fosi, Subette barely does anything. If I remove these filter and just rely on Fosi subwoofer knob, I can hear low bass way more in almost all positions, even though it also suppsed to have 12db/Octave slope. But the freequency range is not specified, I could be as well be hearing 500 Hz there. And I am not sure where to put the volume knob because the guide says to keep it easy during the burn in period. That is not very quantifiable.

I have also tried reading the specs of both drivers, from Pipettes (Altair) and Subette (Dayton). Pipette driver seems to drop at 100Hz, and Dayton at roughly 50Hz. Is this a correct reading of the graph? I tried to understand the 70Hz cutoff suggestion. This of course does not take into account the acoustics of the cabinet

I am very inexperiences with subs, so I don't know if it is expected to hear very little form the sub, and mostly have a body feeling from it. Now here are the questions:

1) Should I trust the 70Hz RCA plugs and just get the volume right? Or 70Hz suggestion for Sublime is not universal for other subwoofer amps?

2) How to judge volume levels for Subette? Are there a visual or sonic clues what are "good for initial burn in", "good for long term operation" volumes? I see the speaker moving. Maybe I can play a test track of your suggestion and somehow derive a good listening volume. I can swithc between Pipettes+Subette and Subette-only with one switch on my system. I can also play full range on Subette, tune volume and then switch to sub mode if that helps.

3) Any other suggestions welcome, maybe my approaches are wrong. I plan to get Sublime eventually, but not now, so I wanted to tune what I have at the moment

Other than that the build of both went mostly smooth. Two complications: wire clamps for the Pipette driver were loose and did not hold, had to carefully solder not too melt plastic. Subette did not have this problem, they clicked fine. Subette had very narrow holes in the wood for hexagonal screws for the driver, had to widen them first. Just a feedback, for you to consider improving. Otherwise smooth build, great job overall, I love the speakers!

Thanks,
Igor.

[Paul Birkeland]

Plus it is source is my integrated amp pre which is usually operated at 50% of the volume for Pipettes. If power is logarithmic, does it mean that this sub with 50% volume at pre should always operate at less than 30W (roughly), right?

There isn't any relationship to volume control position and power output, other than turning the volume knob up will result in more output power than you had before (until you clip the amp at least).  The issue is that the source voltage ahead of the amp will have a major influence on power output at a given volume control position, so you can't really make any assumptions.

Well, not so simple with those RCA plugs. They have 12dB/Octave slope and it is not documented what slope Sublime has. When I use them via Fosi, Subette barely does anything. If I remove these filter and just rely on Fosi subwoofer knob, I can hear low bass way more in almost all positions, even though it also suppsed to have 12db/Octave slope.

What's the output impedance of the device driving the Fosi amplifier?  Inline crossover filters like the ones you have are not necessarily the easiest things to drive, and you may be experiencing a lot of insertion loss. 

You should be able to get things set pretty well with an RTA app on your phone.

[ipetruk]

Thank you, I will play a bit with the app. The problem is in the app that phone mic needs to be calibrated against pink noise which will have to be reproduced via some reference system.

I have a other little problem, is this rattle expected?

https://youtube.com/shorts/ROFGV89gqV4?si=odQAZS0XvgrkYwLU

The video is only with sub connected, no speakers. It is normally not very audible in normal music, unless it is very bassy.

It seems to be in the driver. I don't know if I should try to remove it to see if maybe wires are rattling.

[ipetruk]

I might have in fact overtightened the gasket here, not sure if it is possible to recover or put an extra gasket

[Paul Birkeland]

Thank you, I will play a bit with the app. The problem is in the app that phone mic needs to be calibrated against pink noise which will have to be reproduced via some reference system.

There are apps that will be relatively well calibrated if your phone is adequately supported.  I can't help with the rattle, as I'm not yet a Pipette owner.

[ipetruk]

It is a Subette that is rattling.

I was thinking it was gasket, or seal, or something. It does not look like it is a gasket, it seems too seal fine

But I think it is a rubber that is rattling on the driver. Lightly touching it makes it stop rattling. Just trying to understand is it normal or not. Is the driver damaged? If rubber part is damaged, can it be glued, or does the driver need to be replaced?

[ipetruk]

Here it is working slightly pulled out from the cabinet

https://youtube.com/shorts/lbqC8L1MeTY?si=gxmhZoTnKWXzxD7q

I have a feeling it is that yellow cloth making a "sail in the wind" sound. Do you observe this with your units?

I do realize the drivers will not get enough air pressure resistance when the cabinet is opened, but I am only trying to troubleshoot where the sound comes from. Many things can go wrong, for example it could be a defective driver, or the load could be higher than supported, etc.

Again, this is my first subwoofer in my life, so I don't really know how is it supposed to work and if rattle is simply a subwoofer honestly moves at super low frequency