PURIFI finally did a fully purified passive speaker design! The SPK 16 prototype is here - with a PTT tweeter

[Salt]

Isn't it time for a new thread called '3 D Printing: Best Material Choice' ??

 

[Paul7777x]

Isn't it time for a new thread called '3 D Printing: Best Material Choice' ??

I think so. Very interesting, but more than a little tangential to the thread topic.

 

[JanRSmit]

I think so. Very interesting, but more than a little tangential to the thread topic.

Interesting, How would you establish the best?

 

[Paul7777x]

Interesting, How would you establish the best?

Not sure I understand your meaning? The best what?

 

[Salt]

Interesting, How would you establish the best?

?

 

[kyuu]

You're missing the obvious.
1. Plate amp is enclosed in a speaker. Worse heat wise than in an amp enclosure. Depending on how hard the speaker is being driven, much hotter.

Plate amps are typically designed with heatsinks (at the very least the components are thermally coupled to the plate itself) and can reject a lot of heat outside the enclosure. Plus, if the enclosure is ported, there's going to be airflow pushing heat out of the enclosure as well.

2. Pistonic vibrations within the enclosure especially with the Purifi drivers. It's part of the secret sauce. These affect not only the capacitors but all solder joints.

"Goop" is often used to protect components on the board against vibrations.

There's nothing wrong with external amps. However, plate amps are quite popular for what should be quite obvious reasons. I think you're overstating both the potential for issues with plate amps as well as the difficulty of replacing them. And particularly if someone is constructing their own speaker, what is the point of arguing vociferously with their choice of a plate amp for their own speaker? Separate amps are hardly immune to thermal issues anyway.

 

[Luvchampagne]

Plate amps are typically designed with heatsinks (at the very least the components are thermally coupled to the plate itself) and can reject a lot of heat outside the enclosure. Plus, if the enclosure is ported, there's going to be airflow pushing heat out of the enclosure as well.

Not sure where you get the ported situation. The use case is SPK16. There's passive radiators. No port. Where's the airflow?
Also let's be honest about the typical use case of the Spk16. Who's going to be buying speakers with purifi high excursion extra low distortion drivers?
Most people will be utilizing the Purifi drivers where they show the most advantage. Higher excursion. Not to say you or anyone else won't. But if a person is a typical 50 to 60db listener, the Purifi driver advantages significantly diminish so why would they intentionally pay the premium for this great technology?
So take that use case - higher spl user. Now we've got more heat and more vibrations. Again, maybe not you. But a good percentage will be that user.

"Goop" is often used to protect components on the board against vibrations.

There's nothing wrong with external amps. However, plate amps are quite popular for what should be quite obvious reasons. I think you're overstating both the potential for issues with plate amps as well as the difficulty of replacing them. And particularly if someone is constructing their own speaker, what is the point of arguing vociferously with their choice of a plate amp for their own speaker?

I don't care what other people do. However I would want an open design so that people have a choice between plate amps or external dsp and external amps. General crossover, delay, phase, polarity and filter information. Enough that an active system could be built without undue burden on the Purifi team. It would definitely be do it at your own risk - sharing information. Not a separate kit.

Unfortunately, I've owned over 10 plate amps speakers. All except 1 has failed. How many are replaceable in the same dimension and capabilities? Zero. Only solution is to remove plate amp, connect external wires, drill a hole through the plate amp for the wires, reseal the hole and run it externally.

 

[Kaladin]

You're missing the obvious.
1. Plate amp is enclosed in a speaker. Worse heat wise than in an amp enclosure. Depending on how hard the speaker is being driven, much hotter.
2. Pistonic vibrations within the enclosure especially with the Purifi drivers. It's part of the secret sauce. These affect not only the capacitors but all solder joints.
Add those to your calculations and it's far worse.
Do you disagree? If so, have you looked at the calculations including excess heat and vibrations?

Yes. I’ve designed high-rel electronics for much worse conditions than a plate amp will ever experience.

 

[Salt]

I've owned over 10. All except 1 has failed.

Exceptional.
What amp under what condition?

 

[bmc0]

You're missing the obvious.

Neither point is particularly relevant to what I stated, which was simply that rated life must be qualified with rated temperature.

 

[kemmler3D]

I'll just say that if I were going to add a space for a plate amp using 3D printing, you could easily optimize airflow. Since adding separate chambers and whatnot does not really increase difficulty of manufacture or assembly, you can actually have as much airflow as you want for the plate amp if you are going to do it that way. The rest of the cabinet behind the amp would remain fully sealed.

As for starting another thread for the 3D printing stuff, I think that would be a good idea. I'll kick one off once I have a worthwhile update from my end.

 

[Luvchampagne]

Neither point is particularly relevant to what I stated, which was simply that rated life must be qualified with rated temperature.

Ok. So what do you do when you use your system 8+ hours a day and your rated life is 4 years? Keep in mind no hypex fusion plate amp has nichicon or rubycon components.
By the way, I completely agree with your statements theoretically.
But practically I don't want to be wondering 4 to 6 years from now how I deal with a plate amp that doesn't work and no dsp information. Open to your wisdom on best path forward at that point.

 

[Luvchampagne]

Yes. I’ve designed high-rel electronics for much worse conditions than a plate amp will ever experience.

????. Please tell me how that is relevant to an off the shelf hypex fusion plate amp? What are you designing?

Last thing I want to do is burden Purifi. The fact they released the SPK16 kit is amazing. Instead of asking for a modified plate amp cabinet, I would ask Purifi to please share some data so we can build an active version.

If you or anybody else wants build your active system with a plate amp then great.

 

[Roland68]

You're missing the obvious.
1. Plate amp is enclosed in a speaker. Worse heat wise than in an amp enclosure. Depending on how hard the speaker is being driven, much hotter.
2. Pistonic vibrations within the enclosure especially with the Purifi drivers. It's part of the secret sauce. These affect not only the capacitors but all solder joints.
Add those to your calculations and it's far worse.
Do you disagree? If so, have you looked at the calculations including excess heat and vibrations?

In addition to the potential lack of bond with the plastic, one other concern I have with a mostly closed, fillable shell is simply getting rid of the free water in a reasonable amount of time. Gypsum plaster isn't highly alkaline like portland cement and will tend to support mold growth if not dried completely and in a timely manner.

There's actually a very simple and practical solution for this.
You build proper stands for the speakers and use them as mounts for plate amplifiers, for DSPs with other amplifiers (stereo or mono), or for the passive crossover, optionally with an amplifier mount.

You don't have to decide between active and passive speakers, and you don't need to make any modifications later. Simply connect the tweeter and mid-woofer to the back of the speaker.

The cables can be neatly hidden in the stands, and a chimney effect can be integrated for silent cooling of the amplifier(s).
A win-win-win situation.

The hour ratings aren't very useful without temperature ratings. If I'm not remembering wrong, expected life approximately doubles for every 10C decrease in operating temperature. So a cap rated for 8k hours at 85C and one rated for 2k hours at 105C will have a similar expected life if both are operated at, say, 65C.

You're barking up the wrong tree regarding capacitors.

With conventional Class A, A/B, etc. amplifiers using standard transformer power supplies, temperature is indeed an important factor, but up to about 50°C, you don't need to worry.
The lifespan halves approximately every 6°C. Experience shows that for Class A amplifiers operating at just over 60°C, this means replacing the capacitors roughly every 6-8 years. At 50°C, you're looking at 20 years or more.

With switching power supplies and Class D amplifiers, the frequency load on the capacitors is, in most cases, the decisive factor for their lifespan. As long as temperatures don't significantly exceed 50°C, temperature is of secondary importance for aging.
Just because a capacitor has a specified temperature rating of 105°C, 125°C, or more doesn't automatically mean it will last even a day longer in that application.

 

[Luvchampagne]

Exceptional.
What amp under what condition?

All high excursion subs. Something that is relevant to the Purifi drivers.

 

[Kaladin]

????. Please tell me how that is relevant to an off the shelf hypex fusion plate amp? What are you designing?

Last thing I want to do is burden Purifi. The fact they released the SPK16 kit is amazing. Instead of asking for a modified plate amp cabinet, I would ask Purifi to please share some data so we can build an active version.

If you or anybody else wants build your active system with a plate amp then great.

Scroll up and you can find pictures I posted of a cabinet for a Hypex plate amp that’s close to finished.

Nobody is burdening anyone from Purifi.

 

[Salt]

I'll just say that if I were going to add a space for a plate amp using 3D printing, you could easily optimize airflow. Since adding separate chambers and whatnot does not really increase difficulty of manufacture or assembly, you can actually have as much airflow as you want for the plate amp if you are going to do it that way. The rest of the cabinet behind the amp would remain fully sealed.

As for starting another thread for the 3D printing stuff, I think that would be a good idea. I'll kick one off once I have a worthwhile update from my end.

Hypex Plateamps do have slots for ventilation ...

 

[Luvchampagne]

Scroll up and you can find pictures I posted of a cabinet for a Hypex plate amp that’s close to finished.

Nobody is burdening anyone from Purifi.

Awesome work. How are you dealing with the differences in interior volume and other variables the plate amp is introducing to the spk16 design? Lots of work and I commend you for doing so.

 

[Salt]

All high excursion subs. Something that is relevant to the Purifi drivers.

The amplifier?

All high excursion subs. Something that is relevant to the Purifi drivers.

The amplifier?

 

[Luvchampagne]

The amplifier?

The amplifier?

Whatever amp the sub manufacturer used.
Have you ever seen a separate manufacturer for a subwoofer plate amp?