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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: stuartwgibson on July 07, 2013, 09:12:26 pm

Title: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: stuartwgibson on July 07, 2013, 09:12:26 pm
Simple (and possibly horrifying question to you pros), but I'm wondering if it is ok to link additional high frequency drivers (horns) to my system.
I am bi-amping, and the signal passes through a cross-over and a limiter before it gets to the amp.  The cross-over is set to the same frequency limit (on the low end) as the horn (1.6KHz).  To clarify, there is no additional crossover between the amp and the horn in this configuration.  My main concern is over-driving these extra horns, of course. 
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: John Roberts {JR} on July 07, 2013, 09:13:26 pm
Depends on the drivers but LF energy can damage HF drivers.

JR
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: stuartwgibson on July 07, 2013, 09:23:37 pm
Thanks, yes.  So if my board crossover is limiting the signal to 1.6 KHz and above, will that protect the driver from damaging low frequencies? 

Depends on the drivers but LF energy can damage HF drivers.

JR
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Ivan Beaver on July 07, 2013, 09:24:46 pm
Simple (and possibly horrifying question to you pros), but I'm wondering if it is ok to link additional high frequency drivers (horns) to my system.
I am bi-amping, and the signal passes through a cross-over and a limiter before it gets to the amp.  The cross-over is set to the same frequency limit (on the low end) as the horn (1.6KHz).  To clarify, there is no additional crossover between the amp and the horn in this configuration.  My main concern is over-driving these extra horns, of course.
There are several concerns.  First is the impedance of the drivers on the amplifier.  Next is your statement "The crossover is set to the same frequency limit of the horn"

What exactly does that mean?  Is that the horn? or the driver on the horn"?

Are the new drivers the same model/impedance as the other ones?

You do not need any additional crossover-but you will also not have any protection against low freq "accidents" getting into the drivers.

How is the limiter set?  How were the settings determined?

So as usual-there are a lot of "it depends".  But basically-yes-no problem

OF course actual model numbers of all the pieces would help a lot-to give an idea of what is actually going on.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: stuartwgibson on July 07, 2013, 09:34:57 pm
Well, you zeroed right in on the weakness in my knowledge here..:-)  The high frequency driver is 8 Ohms / 125W ( I guess I was using "horn" improperly).  The amp can drive 2-8 Ohms.  All the other elements in my high end chain are 8 Ohms as well, but the others have built in crossovers in the cabinets.

There are several concerns.  First is the impedance of the drivers on the amplifier.  Next is your statement "The crossover is set to the same frequency limit of the horn"

What exactly does that mean?  Is that the horn? or the driver on the horn"?

Are the new drivers the same model/impedance as the other ones?

You do not need any additional crossover-but you will also not have any protection against low freq "accidents" getting into the drivers.

How is the limiter set?  How were the settings determined?

So as usual-there are a lot of "it depends".  But basically-yes-no problem

OF course actual model numbers of all the pieces would help a lot-to give an idea of what is actually going on.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: stuartwgibson on July 07, 2013, 09:47:40 pm
Following up:  These are B-52 Comp-3300 compression drivers.  The amps are QSC 3400W.  I've been using the limiter to keep the amps from clipping, but admittedly, that won't protect the high end of my output chain from being over-driven, since it uses far less power than the low end.


How is the limiter set?  How were the settings determined?

So as usual-there are a lot of "it depends".  But basically-yes-no problem

OF course actual model numbers of all the pieces would help a lot-to give an idea of what is actually going on.
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Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Tim Perry on July 08, 2013, 12:20:19 am
Following up:  These are B-52 Comp-3300 compression drivers.  The amps are QSC 3400W.  I've been using the limiter to keep the amps from clipping, but admittedly, that won't protect the high end of my output chain from being over-driven, since it uses far less power than the low end.


How is the limiter set?  How were the settings determined?

So as usual-there are a lot of "it depends".  But basically-yes-no problem

OF course actual model numbers of all the pieces would help a lot-to give an idea of what is actually going on.

Stuart, more is not necessarily better especially when dealing with the HF part of the speaker.

 If you are using a 3400W amp on the HF section I suspect a lot of it's capability is being wasted, or at least not being utilized.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: stuartwgibson on July 08, 2013, 12:55:58 am
For sure, I am not fully utilizing the amp for the highs.  But I'm maxing out the low amp, and kept blowing diapraghms in the HFDs trying to keep the highs and lows matched.  So I'm hoping to reinforce the highs, thereby using more of the available amp power without jeopardizing my array of HFDs. 


Stuart, more is not necessarily better especially when dealing with the HF part of the speaker.

 If you are using a 3400W amp on the HF section I suspect a lot of it's capability is being wasted, or at least not being utilized.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Tim Perry on July 08, 2013, 01:16:45 am
For sure, I am not fully utilizing the amp for the highs.  But I'm maxing out the low amp, and kept blowing diapraghms in the HFDs trying to keep the highs and lows matched.  So I'm hoping to reinforce the highs, thereby using more of the available amp power without jeopardizing my array of HFDs.

Add one or 2 tail lamps in series with the driver.

Am I safe in assuming this in for DJ service?
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Ivan Beaver on July 08, 2013, 07:43:26 am
For sure, I am not fully utilizing the amp for the highs.  But I'm maxing out the low amp, and kept blowing diapraghms in the HFDs trying to keep the highs and lows matched.  So I'm hoping to reinforce the highs, thereby using more of the available amp power without jeopardizing my array of HFDs.
Simply adding more HF drivers will make it louder-but it WILL ALSO make it sound WORSE.

Your best bet is to use FEWER-BETTER QUALITY HF drivers.  This way you can get louder and sound better.  Of course it will cost more.

Adding more subs is one thing-adding more highs is a totally different matter and MUCH hrader (to get them to sound good).  It is real easy electrically-but ACOUSTICALLY is where the challenge is.  It is one of the hardest things to do in audio-at least to do RIGHT.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: stuartwgibson on July 08, 2013, 09:26:41 am
Well, now that you mention it, that's kind of what I am trying to do.  The Comp-3300s are quite nice.... more crisp and defined, definitely not muddy.  I already had 2 as built into my PA15x (B-52 2-ways) pair.  I was hoping to buy just the HFD raw components (2 more) and add those into the chain (with or without the lamer Yamaha tops). 


Simply adding more HF drivers will make it louder-but it WILL ALSO make it sound WORSE.

Your best bet is to use FEWER-BETTER QUALITY HF drivers.  This way you can get louder and sound better.  Of course it will cost more.

Adding more subs is one thing-adding more highs is a totally different matter and MUCH hrader (to get them to sound good).  It is real easy electrically-but ACOUSTICALLY is where the challenge is.  It is one of the hardest things to do in audio-at least to do RIGHT.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: stuartwgibson on July 08, 2013, 09:46:20 am
Don't know what tail lamps are..:-)  Yes, DJ, but large outdoor venue. 

Add one or 2 tail lamps in series with the driver.

Am I safe in assuming this in for DJ service?
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: sam saponaro on July 08, 2013, 10:53:19 am
I run my RCF N482 drivers/H3709 bells(8ohm 90W) in my EAW cabs direct off one side of a Crown CE1000 with nothing inbetween but a 2A fuse.So far so good and it sounds great. I run each side(1 cab per side) of my top end on its own CE1000 split in stereo.Each amp runs CH1 for mid/bass and CH2 for HF crossed at 1.5K befor the amps with a DBX crossover.
I heard wiring a capacitor in series with the HF driver helps limit the LF that the drivers can see but I have not tried that.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Art Welter on July 08, 2013, 12:49:48 pm
I heard wiring a capacitor in series with the HF driver helps limit the LF that the drivers can see but I have not tried that.
A capacitor can protect the HF diaphragm from DC output from a catastrophic amp failure or 60 Hz damage from a huge ground loop.
Back in the 1970s  both of those problems were frequent, with current technology series capacitors are not generally needed, and cause other sonic problems.

Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Art Welter on July 08, 2013, 12:58:55 pm
Don't know what tail lamps are..:-)  Yes, DJ, but large outdoor venue.
Series light bulbs (commonly tail lights or cabin dome lights) illuminate at high drive levels, reducing level to the driver and visually indicating you are near the thermal limit of the driver if properly sized for the application.

Before the bulb sees enough power to light up, it acts like a series resistor.
The only speakers I ever owned with series bulbs I found them to be an annoyance, as high volume transient peaks would make the bulbs burn out like a fuse, we replaced them with  resistors of the same DC resistance as they were part of the passive crossover.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: stuartwgibson on July 08, 2013, 01:23:26 pm
So I could put a DC resistor between the amp and the HFD to protect it?  I like that idea, but I don't know how to figure out what resistor to use.

The HFDs in question are rated at 125 watts
800-20K Hz
16 Ohms

not sure what to make of the fact that the driver is clearly marked 8 ohms, but the b-52 web site says it has an impedance of 16ohms.


Series light bulbs (commonly tail lights or cabin dome lights) illuminate at high drive levels, reducing level to the driver and visually indicating you are near the thermal limit of the driver if properly sized for the application.

Before the bulb sees enough power to light up, it acts like a series resistor.
The only speakers I ever owned with series bulbs I found them to be an annoyance, as high volume transient peaks would make the bulbs burn out like a fuse, we replaced them with  resistors of the same DC resistance as they were part of the passive crossover.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Patrick Tracy on July 08, 2013, 01:45:27 pm
So I could put a DC resistor between the amp and the HFD to protect it?  I like that idea, but I don't know how to figure out what resistor to use.

No, he said he had speakers with protective light bulbs incorporated into the passive crossover and that it was inconvenient when they burned out so he replaced them with resistors so they wouldn't burn out, losing the protection.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Tim Perry on July 09, 2013, 05:10:23 am
So I could put a DC resistor between the amp and the HFD to protect it?  I like that idea, but I don't know how to figure out what resistor to use.

The HFDs in question are rated at 125 watts
800-20K Hz
16 Ohms

not sure what to make of the fact that the driver is clearly marked 8 ohms, but the b-52 web site says it has an impedance of 16ohms.

The "resistor" would actually be a thermistor. That is a resistor that changes value as its temperature goes up.

In the case of these light bulb protectors, a low resistance is presented when cold which rapidly increases when the filament gets hot.

It can be annoying when these burn out or open up due to mechanical shock, however it a easier and lower cost fix then replacing the voice coils or drivers.

If you are blowing 125W drivers you must be running these screaming loud of have some other issue with you setup.   
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Ivan Beaver on July 09, 2013, 07:22:08 am

If you are blowing 125W drivers you must be running these screaming loud of have some other issue with you setup.   
Or they aren't really 125wat drivers.  The less expensive drivers often come will sorts of "inflated" wattage ratings to make them "appear" to be stronger than they really are.

Is that continuous-program-peak-peak to peak power or something else?

My car can get 100 miles per gallon-as long as I only measure it coasting down a mountain while in neutral--------  But int he real world-much less.  So it is not the number that is suspect-but rather the test condition/measurement.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Tim Perry on July 09, 2013, 09:35:11 am
Or they aren't really 125wat drivers.  The less expensive drivers often come will sorts of "inflated" wattage ratings to make them "appear" to be stronger than they really are.


Curses, fooled by the phony marketing specs again!

Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: stuartwgibson on July 09, 2013, 09:50:39 am
They really are 125w.  But you can see with a QSC 3400 running the highs, how I could easily overdrive these.  Still hoping to add 2 more, which would definitely solve the problem. 
Disconnected one HFD from the right and added it in parallell on the left.  So then with two identical HFDs on the left (one bi-amped through the cabinet crossover and one essentially running directly off the amp), the direct connected one was noticeablly louder.  Still waiting to hear from B-52 about the discrepency between their website specs and the specs on the comp3300 itself (16 ohms vs. 8 ohms)

Curses, fooled by the phony marketing specs again!
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Mark McFarlane on July 09, 2013, 03:35:24 pm
Simply adding more HF drivers will make it louder-but it WILL ALSO make it sound WORSE.

Your best bet is to use FEWER-BETTER QUALITY HF drivers.  This way you can get louder and sound better.  Of course it will cost more.

Adding more subs is one thing-adding more highs is a totally different matter and MUCH hrader (to get them to sound good).  It is real easy electrically-but ACOUSTICALLY is where the challenge is.  It is one of the hardest things to do in audio-at least to do RIGHT.

Stuart, please take heed to this advice before you get carried away on technically how to do something that isn't a good idea in the first place.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Ivan Beaver on July 09, 2013, 09:22:25 pm
They really are 125w. 
Once again- is that 125 continuous watts- or 125 program watts or 125 peak watts or something else?

How do you know?  So you have any specs or model numbers?  What is the voice coils size? etc.

All "watts" are not created equal.  There are real watts-marketing watts-power compression watts and so forth.

Just sayin' ------------------------------------------------------
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: stuartwgibson on July 10, 2013, 06:30:48 pm
Appreciate all the feedback.  I can see that my choice is between running these straight out of my board cross-over/amp or building new cabs with a dedicated passive crossover (almost certainly the preferred choice, since it would add a good measure of protection).
I just have to make sure about the whole 16 ohms / 8 ohms thing. 
Can anyone think why the HFD itself would be marked 8 ohms on the back, while the b-52 specs call it a 16 ohms driver? 
FWIW, the selenium diapraghm inside the driver is 16 ohms.



Once again- is that 125 continuous watts- or 125 program watts or 125 peak watts or something else?

How do you know?  So you have any specs or model numbers?  What is the voice coils size? etc.

All "watts" are not created equal.  There are real watts-marketing watts-power compression watts and so forth.

Just sayin' ------------------------------------------------------
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Ivan Beaver on July 10, 2013, 07:57:09 pm
Appreciate all the feedback.  I can see that my choice is between running these straight out of my board cross-over/amp or building new cabs with a dedicated passive crossover (almost certainly the preferred choice, since it would add a good measure of protection).
I just have to make sure about the whole 16 ohms / 8 ohms thing. 
Can anyone think why the HFD itself would be marked 8 ohms on the back, while the b-52 specs call it a 16 ohms driver? 
FWIW, the selenium diapraghm inside the driver is 16 ohms.
Probably because the load presented to the amp by the driver crossover COMBINATION is actually 8 ohms-even though the driver may be 16 ohms.

This is not uncommon.

Of course without an actual measurement (impedance- NOT resistance) there is no way to really say exactly what it is.

At least we have a manufacturer now-how about a model number?

COMPLETE INFORMATION REALLY HELPS!!!!!!!!!!!!  Instead of making people guess what you have--------------

Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: David Morison on July 11, 2013, 08:08:08 am
At least we have a manufacturer now-how about a model number?

COMPLETE INFORMATION REALLY HELPS!!!!!!!!!!!!  Instead of making people guess what you have--------------

To be fair, he did give that in both reply #5 and reply #20.

However, the manufacturer's page gives no more useful info than we have already (ie nominal impedance without a Z curve and only the single, undefined wattage number).
Regards,
David.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: Brad Weber on July 11, 2013, 08:17:54 am
They really are 125w.  But you can see with a QSC 3400 running the highs, how I could easily overdrive these.  Still hoping to add 2 more, which would definitely solve the problem. 
Disconnected one HFD from the right and added it in parallell on the left.  So then with two identical HFDs on the left (one bi-amped through the cabinet crossover and one essentially running directly off the amp), the direct connected one was noticeablly louder.  Still waiting to hear from B-52 about the discrepency between their website specs and the specs on the comp3300 itself (16 ohms vs. 8 ohms)
Can you clarify what you did and how you plan to wire these?  You need a crossover in there somewhere, either passive after the amp or active before it.  So are you saying you compared a horn and driver driven by an active crossover and then an amp with an identical horn and driver driven by the same amp but with no crossover before the amp and through the passive crossover of the speaker after the amp?  Or did the one go through an external crossover and the other through both that external active crossover and the internal passive crossover?  Or was one essentially run full range and the other through the internal passive crossover?
 
What you observed might be exoplained by the fact that chances are good that the passive crossover in the amp intentionally pads down the HF as typically the HF driver and horn are capable of greater output than the LF driver.  However, the fact that you say you are blowing HF drivers trying to keep up with the LF indicates that either that is not the case here or there may be something wrong in your setup.
 
Unfortunately, B-52 does not seem to offer the information needed to tell much of anything about the speakers or the components.  For example, the speaker info says it can be run bi-amped but the only data provided is for the full range mode.  The power handling ratings do not say what they represent or how they were determined, based on the Peak SPL and Sensitivity claimed the speaker rating appears to be a Program power rating while the driver ratings are claimed to be "R.M.S.".  The frequency responses are specified with no limits and no additional data offered.  And there is apparently no manual for the speaker or drivers.  Basically, B-52 does not provide the information necessary to make any informed responses or decisions regarding bi-amping your speakers.
 
But I think we may be getting away from the main point and that is exactly what you believe you are going to accomplish from all of this effort?  What change do you think a second HF driver and horn per side will cause?  You are not going to get the two HF drivers close enough for coupling over any of their bandwidth so the best possible result is +3dB overall, but probably with some negative affects on the response.  Is that really worth all of this?  Why not just keep it simple and either operate the sysyetm full range within its limits or if you absolutely need more output, get some better speakers to start with?
 
By the way, B-52 does say the crossover on the PA15x is 1.4kHz rather than 1.6kHz, but they don't provide any other information such as the filter types or slopes used.
Title: Re: Sound reinforcementCan I run signal directly from amp to high frequency drivers?
Post by: stuartwgibson on July 11, 2013, 10:03:19 am
Thanks for the detailed response..:-)  Yes, while b-52's high-end speakers (PA15x and the like) are nice pieces of equipment with great sound....... B-52's support and documentation are definitely lacking.  I'm using this system in an outdoor venue with about 1500-2000 watts output.  So I do need to reinforce the highs a little.  I think I'm going to replace my Yamaha S115vs (which are inferior and muddy) with b-52 PA-215s.  These have the same COMP 3300 HFDs we've been discussing, and will accomplish my goals without all the hassle.

Can you clarify what you did and how you plan to wire these?  You need a crossover in there somewhere, either passive after the amp or active before it.  So are you saying you compared a horn and driver driven by an active crossover and then an amp with an identical horn and driver driven by the same amp but with no crossover before the amp and through the passive crossover of the speaker after the amp?  Or did the one go through an external crossover and the other through both that external active crossover and the internal passive crossover?  Or was one essentially run full range and the other through the internal passive crossover?
 
What you observed might be exoplained by the fact that chances are good that the passive crossover in the amp intentionally pads down the HF as typically the HF driver and horn are capable of greater output than the LF driver.  However, the fact that you say you are blowing HF drivers trying to keep up with the LF indicates that either that is not the case here or there may be something wrong in your setup.
 
Unfortunately, B-52 does not seem to offer the information needed to tell much of anything about the speakers or the components.  For example, the speaker info says it can be run bi-amped but the only data provided is for the full range mode.  The power handling ratings do not say what they represent or how they were determined, based on the Peak SPL and Sensitivity claimed the speaker rating appears to be a Program power rating while the driver ratings are claimed to be "R.M.S.".  The frequency responses are specified with no limits and no additional data offered.  And there is apparently no manual for the speaker or drivers.  Basically, B-52 does not provide the information necessary to make any informed responses or decisions regarding bi-amping your speakers.
 
But I think we may be getting away from the main point and that is exactly what you believe you are going to accomplish from all of this effort?  What change do you think a second HF driver and horn per side will cause?  You are not going to get the two HF drivers close enough for coupling over any of their bandwidth so the best possible result is +3dB overall, but probably with some negative affects on the response.  Is that really worth all of this?  Why not just keep it simple and either operate the sysyetm full range within its limits or if you absolutely need more output, get some better speakers to start with?
 
By the way, B-52 does say the crossover on the PA15x is 1.4kHz rather than 1.6kHz, but they don't provide any other information such as the filter types or slopes used.