Protection of the high-frequency speaker when switching from passive crossovers to DSP separate amplification of the bands.

[dualazmak]

Again let me state - you are guessing what the impedance of the tweeter is. Until you actually measure the tweeter without the crossover you can't accurately predict what's going to happen at your chosen crossover point with the capacitor value that you have chosen. Therefore to provide some protection I would go at least 2 octaves down using your guess as to the tweeters impedance.

I fully agree with you.
We need, therefore, careful precise measurements before-and-after the protection capacitors like I have done in my posts #402 and #1,009.

 

[Argentum 05]

Is it necessary to install a 250V 1A fuse in the tweeter circuit?

 

[gene_stl]

When I started quad amping my big DIY spikkers , I put 100 milliamp fuses in series with the beryllium dome difficult to replace tweeters and midranges.

I expected them to blow but even at ocassionally loud levels they never did. That was my protection system for about forty years.
The amps were Pioneer class A amps (M22) on both the midrange and tweeter. I did not use protection on the single LE10 (100 1000 Hz) nor on the four woofers (0-100 Hz)

I intend to add capacitors to the circuits since the tweeters and midranges are even more difficult to replace now. I am very interested in a speaker protection board available from Tom Christiansen at NeuroChrome.

Guardian-86

The Guardian-86 is a high-end solid state speaker protection circuit board module for use in audiophile audio amplifiers. The Guardian-86 uses MOSFETs instead of relays to protect your speakers resulting in better performance and better protection of your speakers.

neurochrome.com

There is also a great deal of content for those that wish to DIY. ESP in australia has a lot of pages. Search " MOSFET relay speaker protection " to get a lot of content to pore over.

 

[levimax]

How long have you been using your configuration?
Perhaps I'm being overly cautious.

I have been playing around with DIY tri-amp speakers for almost 20 years and never used any protection on any of the drivers. While I have had some incidents I have never damaged a driver. I have always used easily replaceable tweeters though which makes a difference. One thing I do is size the amp sensibly for the tweeters. I see people talking about using 200 watt amps for tweeters which is asking for trouble in my opinion. Over the years I have used amps between 25 and 50 watts on the tweeters which is plenty of power but not enough to instantly destroy them (in most cases).

Fuses in my experience are hard to size and give a false sense of security as your driver is just as likely to protect the fuse as the other way around.

 

[sergeauckland]

Does the type of capacitor matter given that it’s in the signal path? And do you put that 1k resistor before or after the cap? I use a circuit that’s supposed to trip a relay if it senses DC ( Rod Elliott’s design) but I’m still faintly paranoid about my B&W 801 tweeters.

No, I just used an ordinary bipolar electrolytic. There's very little voltage across it as the crossover frequency is sufficiently high, so very little added distortion, well below what the driver itself would generate. As to the resistor, it has to be before the capacitor, effectively directly across the amplifier's output, so as to present the amplifier with a DC path.

S

 

[Argentum 05]

I have been playing around with DIY tri-amp speakers for almost 20 years and never used any protection on any of the drivers. While I have had some incidents I have never damaged a driver. I have always used easily replaceable tweeters though which makes a difference. One thing I do is size the amp sensibly for the tweeters. I see people talking about using 200 watt amps for tweeters which is asking for trouble in my opinion. Over the years I have used amps between 25 and 50 watts on the tweeters which is plenty of power but not enough to instantly destroy them (in most cases).

Fuses in my experience are hard to size and give a false sense of security as your driver is just as likely to protect the fuse as the other way around.

What amps did you use for the tweeters?
I'm planning on using my Yamaha ax892 for now, but it's quite powerful. I just already have one.

 

[LiveTek]

I'm curious, how likely is it that a DSP glitch could cause such problems?
I haven't heard of any such cases. My Wiim Pro Plus has never had any glitches related to volume changes.
Maybe I'm being overly cautious?
But as the saying goes, "Just because you're paranoid doesn't mean you're not being watched."

I think tweeters are a bit more robust than people think. Ive put my poor tweeters through just about everything you could imagine as far as dsp whoopsies go and they just keep going. Ive run woofer signals to them, made changes in a sigma studio dsp unit which if anyone knows makes for some awful noises. Ive shorted amps into them. All of it with no protection.

Im not saying one shouldnt toss a cap on, but Ive been running active systems like this for decades now, some were pa rigs, never blown a driver.

 

[dualazmak]

BTW, even though a little bit out of the scope of OP @Argentum 05, I believe metal-horn super-tweeters are much more susceptible for damage by accidental DC-like inputs and over-loads in comparison with dome tweeters.

I could confirm it through my invaluable discussion with engineering people at FOSTEX when I "hospitalized" my pair of T925A to FOSTEX Service Center for overhaul maintenance (ref. #485).

 

[dualazmak]

Just reference for OP @Argentum 05...

At least in my DSP-based multichannel multi-SP-driver multi-amplifier full active setup, I always perform careful "start-up/ignition sequences" and "shutdown sequences", these are part of the protection procedures/measures for my (our) treasure SP drivers; please refer to the bottom portion of my lengthy post #931.

 

[levimax]

What amps did you use for the tweeters?
I'm planning on using my Yamaha ax892 for now, but it's quite powerful. I just already have one.

Nuerochrome Mod 86

 

[Argentum 05]

I think tweeters are a bit more robust than people think. Ive put my poor tweeters through just about everything you could imagine as far as dsp whoopsies go and they just keep going. Ive run woofer signals to them, made changes in a sigma studio dsp unit which if anyone knows makes for some awful noises. Ive shorted amps into them. All of it with no protection.

Im not saying one shouldnt toss a cap on, but Ive been running active systems like this for decades now, some were pa rigs, never blown a driver.

I encountered a problem with damaged tweeters. However, it wasn't related to the DSP.
I had Magnat Monitor Supreme 2000 speakers (they're now sold). I didn't overload them during use. At some point, the left tweeter burned out. It turned out that one of the capacitors in the passive crossover had swelled. I don't remember the rating anymore, but I remember it was 50V.

The technician who repaired the tweeter and crossovers cursed the manufacturer of these speakers.
Perhaps that's why I'm overly cautious.

 

[JaMmy]

No, I just used an ordinary bipolar electrolytic. There's very little voltage across it as the crossover frequency is sufficiently high, so very little added distortion, well below what the driver itself would generate. As to the resistor, it has to be before the capacitor, effectively directly across the amplifier's output, so as to present the amplifier with a DC path.

S

Thanks. I now have a wee project for today!

 

[dualazmak]

I found my own post #901 where I wrote;

At least in my setup, of course I carefully measured and confirmed that the protection capacitors are essentially transparent and "inaudible"; please refer to my posts here #402 and #485 (as well as #258 for subjective comparison).
Edit: And in #1,009!

I use these protection capacitors for protecting my treasure Be-midrange-squawkers, Be-tweeters, and metal horn super-tweeters from possible accidental intrusion of low Fq signal and/or DC.

In the course of intensive DIY of DSP-based multichannel multi-SP-driver multi-amplifier "fully active" audio setup, we have several possibilities of such unexpected "accidents", e.g. mis-configuration/mis-typing in XO/EQ/Group-Delay/Gain settings, mis-connection of line-level and/or SP-high-level cables, unexpected pop due to "excessively buffered" signal intrusion when changed the XLR cables, etc., etc.

I actually experienced a few such cases (even I have been always much careful though) that the protection capacitors actually did their job perfectly protecting my treasure SP drivers. Consequently and fortunately, I never lost/damaged my treasure SP drivers thanks to the protection capacitors.


I also wrote here #313 on the remote thread;

I know that XOs (many parameters), time-alignment, phase tuning, EQ and gain in DSP would be more-or-less interdependent with each other, right?
None of them can be changed/modified completely independently.
On the other hand, analog-level gain controls do not affect the upstream DSP configurations.

One of the other pros of HiFi analog-level relative gain tuning (tonality control) by knobs/dials would be it is very safe on-the-fly compared to on-the-fly DSP gain control.

In case if you would like to do it in DSP, especially on-the-fly, you always have possibility of mis-adjustment of gains, i.e. and e.g. 20 dB boost instead of intended 2.0 dB boost by numerical keyboard mistyping the value (and/or it would happen even using mouse wheel up-and-down in some DSP software tools) which may harm and/or destroy your precious SP drivers.

Consequently, I seldom change DSP parameters (especially relative gains) on-the-fly, while listening to music track ; I always stop playing and set the master volume in digital music player to minimum (minus infinity dB) position when changing the DSP parameter(s), and after the DSP modification and after start playing music, I very carefully and slowly gain-up the master volume (in my case JRiver MC) to check the given change in DSP parameters; in this way, I can avoid possible (but rare) harm/damage to SP drivers.

For further safety purposes, I also use protection capacitors for my treasure Be-midranges, Be-tweeters and metal-horn super-tweeters (summary ref. here).

I use DSP EKIO, and EKIO has very nice gain up-and-down by mouse wheel rotation (0.1 dB granularity); I have been always strongly recommending, therefore, to use mouse wheel rotation (not keyboard numeric typing), if you use EKIO and would like to do on-the-fly relative gain control (e.g. ref. here).

 

[Digital_Thor]

All I know that run active - myself inclusive - has never used some kind of protection on tweeters. Now I run 2x200W on a set of KEF coax for the last 1,5 years... No issue.
It should be said though, that if your in doubt of your setup and experiment a lot, you should definitely take any precaution necessary. I just happen to know the designer of my DSP and amplifiers+ the whole functionality of the system, making it much more safe in use.
So always be careful, but also accept that doing DIY with anything electrical, always has it's possible 'dangers'.

 

[Argentum 05]

I found my own post #901 where I wrote;

At least in my setup, of course I carefully measured and confirmed that the protection capacitors are essentially transparent and "inaudible"; please refer to my posts here #402 and #485 (as well as #258 for subjective comparison).
Edit: And in #1,009!

Thank you very much for your work. Your posts contain a lot of interesting and useful information for me.
True, I'm not that experienced, and some of the graphs look like calculations for a Sputnik ballistic trajectory into orbit to me. But I'll try to figure it all out.

 

[Mike123]

I installed 10 µF capacitors on the 8 ohm/3500 Hz tweeters. After that, I take near-field measurements and adjust the filters, delay, and equalization along with the capacitor. I'm happy with the results. I'm not so much afraid of amplifier failures as I am of my own skillful hands .

 

[Argentum 05]

I installed 10 µF capacitors on the 8 ohm/3500 Hz tweeters. After that, I take near-field measurements and adjust the filters, delay, and equalization along with the capacitor. I'm happy with the results. I'm not so much afraid of amplifier failures as I am of my own skillful hands .

I have had cases when my system could use some protection from my hands))))

 

[gene_stl]

If a person is triamping or quad amping it does become desirable to have smaller amplifiers and really outstanding quality ones have gotten fairly rare. At least at reasonable prices. I like the Neurochrome line and Benchmark are attractive too. But the former has gotten pretty expensive lately. Probably he has to to stay in bidness. I have three Pioneer M22 but they generate like 250 watts of heat each. The LM3886 in Neurochrome amps run pretty warm and need serious heat sinking but I like that setup.

BTW does anybody (Calling you Tom Christiansen!) know what commercial products contain LM3886 amp chips. I happened to run across a Grommes PA amp that has one with a transformer coupled output. Very nice thing that fell into my lap but I only got one channel. (A mono item)

 

[dualazmak]

If a person is triamping or quad amping it does become desirable to have smaller amplifiers and really outstanding quality ones have gotten fairly rare. At least at reasonable prices. I like the Neurochrome line and Benchmark are attractive too. But the former has gotten pretty expensive lately. Probably he has to to stay in bidness.

Fully agree with you.

In my case, I intentionally selected my amplifies from the category of "small-to-medium amplifiers having balanced XLR stereo input, integrated ones preferable, Made in Japan preferable".

Furthermore, it is really important to test and evaluate each amplifier in your home listening setup in your room acoustic environments/conditions.

The summary of my "18-month amplifier exploration journey" including Benchmark AHB2 and Accuphase A-36 , done during the COVID pandemic period, can be found in my post #311; I actually intensively tested/evaluated eleven (11) amplifiers in my listening room, that was the great learning and fun part of multichannel multi-amplifier project.

Edit:
For the latest system setup (with the additional Yamaha A-S301 dedicatedly driving super-tweeters), please refer to #931 and #1,009.

 

[Multiway]

Have compression driver HF.
Nice ones so want to protect them.
15ohm.

The widely accepted way to run this particularly driver was with a 3uF cap. This takes care of a frequency peak around 1500 - 2500Hz, gives a nice 1st order XO of around 1100Hz.

I've ran them for 12 years like that both passive and active DSP.

Now with FIR using REW and rePhase to create.
REW gives a nice fix against target curve etc with the cap in place. No compromise or working against as far as I can measure.
Takes care of the 90° phase shift it causes.
Excellent result and protection.

The DSP maker (Colinear DSP-8C) is very specific in the use of a protection cap on the HF, so all good with that.