DavidP-at-Bose
Member
  • 0
  • 69
  • 0
Registered since

Nov 19, 2008

PM Limiter settings for 70V versions of speakers

If you use the factory loudspeaker eq, in PowerMatch, for a speaker that can be set for lowZ or highZ operation (e.g. DS16, DS40, DS100, etc), the limiter settings are not correct when in 70V operation. The factory preset limiter settings are for that loudspeaker in lowZ operation. So in highZ operation, if you use the factory loudspeaker eq, you will never get the full rated output on the line because the voltage will never reach 70/100V.

So it would seem that we need to have HighZ eq versions for any loudspeaker that has, or can have, a Bose supplied transformer.

Thanks-
D.
13 REPLIES 13
RobB-at-Bose
Collaborator
  • 10
  • 1056
  • 0
Registered since

Oct 6, 2008

Re: PM Limiter settings for 70V versions of speakers

Hi David,

That is correct the 'factory presets' are pre-configured for low Z operation. We could easily produce additional files for high Z operation, but we were reluctant to do so because it would mean separate files for 70V and 100V in addition to the low Z files and it seemed a lot of files to manage/wade through when you want to load a preset.

We also considered the option of overiding the limiter settings in the file when you change to 70V or 100V modes by forcing them to 70V or 100V respectively, but it was felt that sometimes changing settings automatically behind the scenes can be counter-intuitive for the user.

Given the choice, what would be the preference? Add lots of additional preset files, leave people to manually override the limiter values when they are using 70/100V (as it is now), or have the limiter values locked to 70V/100V respectively when in 70/100V modes?

As ever all feedback is greatly valued..

Best regards
Rob
Bruce-at-Bose
Bose Employee
  • 9
  • 353
  • 0
Registered since

Oct 3, 2008

Re: PM Limiter settings for 70V versions of speakers

quote:
We could easily produce additional files for high Z operation, but we were reluctant to do so because it would mean separate files for 70V and 100V in addition to the low Z files and it seemed a lot of files to manage/wade through when you want to load a preset.

We also considered the option of overiding the limiter settings in the file when you change to 70V or 100V modes by forcing them to 70V or 100V respectively, but it was felt that sometimes changing settings automatically behind the scenes can be counter-intuitive for the user.



Rob,

I find it interesting that for a product designed primarily for distributed audio using built in transformers that the development team would have chosen to set the threshold using the 8 ohm settings. That seems counter-intuitive to me <smile>. Does the rest of the world (outside of the US, Canada and Mexico) use these products primarily in the direct coupled mode?

I would vote for either having them automatically "reset" when 70 or 100 Volt mode is selected or having separate files for each mode. The current settings abviously don't work and would have the installer wondering why the system won't play as loud as he thought it would. And thinking that 1) the installer would remember to change them and 2) would set them correctly when using the 70 or 100 volt mode is being optimistic.

I will agree that opening the existing Loudspeaker EQ files and scrolling thru the list seems a bit daunting at times. Would there be a problem with breaking the product families down into Subfolders (similar to the way that we select speaker files in Modeler) to make it easier to find and select the appropriate .seq files? We could break out the FreeSpace 8 ohm, 70 volt and 100 volt speakers that way.

Also, don't forget that we would need separate files for the transformer option MA12 and MA12EX installs as well.

Interested to hear other people's thoughts on this subject.

Best Regards,

Bruce
RobB-at-Bose
Collaborator
  • 10
  • 1056
  • 0
Registered since

Oct 6, 2008

Re: PM Limiter settings for 70V versions of speakers

Hi Bruce,

We simply provided all the 'factory presets' configured for low z operation to be consistent, rather than having some low z and some high z. In reality, putting low z limiter settings in the files, probably has more value since they change per product. Whereas when you're running in 70V mode the limiters will always be 71V RMS/100V Peak, and for 100V mode they will always be 100V RMS/141V Peak.

We could consider folders for CSD (Low Z, 70V and 100V), but it will also impact on the front panel selection on PowerMatch Eeker

Best regards
Rob
DavidP-at-Bose
Member
  • 0
  • 69
  • 0
Registered since

Nov 19, 2008

Re: PM Limiter settings for 70V versions of speakers

Rob et al-

Yeah, now that I think about it I see the dilemma with multiple versions of the same eq file. That would make the list a royal pain to search through, and though Bruce's sub-folder idea is a good one, it doesn't work for the PM front panel... unless we make a significant change to how that works.

So I would definitely vote for the "auto-limiter setup" whenever a Hi-Z configuration is selected in the PM properties. The question then becomes whether to:
1. Force/override at all times in a Hi-Z mode (essentially a locked block)

or

2. Have the limiter default to Hi-Z settings but still allow changes. It does this already when you make the initial configuration change. But when recalling a loudspeaker eq this would mean some sort of "configuration-check" coding. I imagine this is probably a little harder to implement coding wise.

That's a tough one, I see good arguments for either option. I think to keep things simple and as dummy proof as possible (sorry I couldn't come up with a better way to say that Wink that we should just lock the limiter block in a Hi-Z mode. Why would you ever change a limiter setting in a Hi-Z configuration? There is no need to "protect" the loudspeaker, it is made to handle those voltages. If you want to "limit" the level, then just attenuate in the output block or adjust somewhere else in the file.

Either way, I definitely believe it has to change from the current configuration. It is not at all intuitive to a designer/installer to go and double check the limiter block after recalling a factory eq, especially when that block comes up "locked" after recalling the spkr eq. Everything you are taught says these settings are what the manufacturer recommends so only change "at your own risk".

Agree/disagree?

Thanks!
D.
DavidP-at-Bose
Member
  • 0
  • 69
  • 0
Registered since

Nov 19, 2008

Re: PM Limiter settings for 70V versions of speakers

Two quick follow-ups after talking with Bruce yesterday and looking at the user guide-

1. It appears from the user guide that on the front panel LCD the preset eq's are already split up by folder (Freespace, RoomMatch, Custom, etc) on the first selector button, is this right? (sorry, neither Bruce or I has an amp at the moment to check). If so, then it would seem rather simple Wink to just add folders for Hi-Z files. E.g. Freespace 8ohm, Freespace 70V, Freespace 100V. And then in CSP software we can either just have a grand list of all files, like we have currently, of split up into folders like it is shown on PM. The latter being the preference, there's nothing stopping that as it is a simple storage folder. Assuming all of the above is true, I would change my prior post and go back to the request for individual eq files.

2. If you select a factory eq on the front panel of the PM, does it lock out the limiter settings? (again apologies for not being able to test this myself) This is not clear in the user guide. Obviously this is the default in the computer software, but it would be problematic if this is the case on the front panel currently as there would be no way to adjust for Hi-Z operation.
Kyle
Contributor
  • 3
  • 1138
  • 0
Registered since

Feb 13, 2017

Re: PM Limiter settings for 70V versions of speakers

Gents,

I guess some things can just slip through the cracks - the limiting function was just one of those things.

Last I can remember (I can verify back in the lab on Monday), there is no lockout of front-panel parameters based on loudspeaker setting. In other words, you can set a loudspeaker from the front panel and immediately modify the limiter. This may however have to change at least for 70/100V modes.


There is some good conversation here. On the hardware side (ignoring CSD for now), in working on some products with long preset lists now, I'm not so inclined to create more presets. The amplifier can already derive the limiter needs from the output configuration. I would prefer the following scenario:

1) User sets the output channels to say "CH1+2 V-Bridge(70V)"
2) The limiter setting for that channel pair gets forced to 70V limiting.
3) Subsequent loudspeaker selections have no effect on the limiter for that channel.

This however doesn't solve the derated use case of driving 70/100V loads in MONO mode but at least you can set the limiter manually. I believe this would be appropriate since the use case itself is a bit of a workaround.

So, I propose the following front-panel rules and throw it out to the community for further comments:

  • 70V or 100V output modes lock the limiter to respective limit voltages.
  • Low-Z output modes allow the limiter parameters to be inherited from user selection of a loudspeaker. The limiter can be adjusted further by the user.


Regarding implementation in ControlSpace Designer, I defer to the Robs.
EricWarner
Contributor
  • 3
  • 122
  • 0
Registered since

Oct 8, 2008

Re: PM Limiter settings for 70V versions of speakers

After thinking through the options, I think that Kyle's proposal is the best combination of options.

Eric
DavidP-at-Bose
Member
  • 0
  • 69
  • 0
Registered since

Nov 19, 2008

Re: PM Limiter settings for 70V versions of speakers

I agree, I think Kyle's proposal makes the most sense from all perspectives (manufacturer, programmer, technician). I especially like how it would keep things as dummy proof as possible for HiZ configurations- and by dummy proof, I mean me.

I don't think we worry about the derated use case in Mono mode, seeing as it is not officially rated that way it would be a special use case anyway and the designer/tech should set as appropriate for their particular case.

Of course this does mean a new CSD software scenario, but hopefully the pre-existence of locked blocks makes it a little easier on "The Robs" Wink
David_from_Bose
Member
  • 0
  • 57
  • 0
Registered since

Oct 18, 2006

Re: PM Limiter settings for 70V versions of speakers

I'll put in a vote for the Kyle Solution as well.

I am assuming that even if this becomes the plan, it will still take a little while to be implemented in a future release of CS Designer.

Can I suggest that in the interim, we produce and release an application note explaining the need to change the limiter settings in Bose EQ's for 70/100v line use and the procedure to do so?

It would make our life easier in the field if we could refer people to an official document.

Early indications in our part of the World are that a significant percentage of PM8500's will be used to drive constant voltage speaker loads, and we want to avoid any confusion or unclear messages getting out there.