ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 2 3 [4] 5 6 ... 9   Go Down

Author Topic: Crossover, L-Pad, Impedence, Resistance question  (Read 10598 times)

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 8911
  • Atlanta GA
Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #30 on: November 21, 2017, 04:18:40 pm »

If you happen to keep the crossover parts connected to the driver(s), interesting things can happen to the impedance curve - you could end up with a near-short at some frequencies. A capacitor across a midbass driver, for instance, would tend towards a short at HF. That's gonna make a lot of amps unhappy.

Chris
Totally agreed.

But with only 1 leg (common) hooked to the crossover, there is no path for any "weirdness" happen.
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 20719
  • Wichita, Kansas USA
Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #31 on: November 21, 2017, 04:35:24 pm »

That will switch the transducers between their 2 sources, but it leaves the input to the crossover in circuit as an additional load on the amplifier when in biamp mode. If this is not a problem a single 4PDT is the way to go. Be sure it has a sufficient AC current rating.

Mac

We added separate NL4 jacks for biamp operation.  While this was for a legacy product I'd do the same thing again.
Logged
"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Jeff Schoonover1

  • Full Member
  • ***
  • Offline Offline
  • Posts: 127
Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #32 on: November 21, 2017, 06:36:29 pm »

Could always do something like this....
Yes, I suppose ganged switches are made.  I'd need another 4-pole double throw with the drawing above.
You're overthinking this, the 4PDT you proposed will work just fine.
The common terminals of the switch go to the transducer; one side of the DT goes to the crossover pass band outputs, the other side of the DT goes to your HI/LOW input jacks.
I *think* I kinda get what you're proposing, but what connects to the inputs of the crossover?  Also, having anything connected to the positive outs of the X-over will put it into the circuit as the others have said?
Shouldn't the minus side of the input to the crossover come from the #1 minus contact on the speakon?
No, when used in Mono mode, a crown amp uses 1+ and 2+ as positive and negative, respectively. The negatives aren't used.
We added separate NL4 jacks for biamp operation.  While this was for a legacy product I'd do the same thing again.
That might be something but in that case, we still need a switch.  I think one 4-pole input and one switch is do-able, I'm just having trouble visualizing.

I think I'll have to add two more poles in order to switch the driver positives out of the circuit in my drawing...
Logged

Mac Kerr

  • Old enough to know better
  • Administrator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 6640
  • Audio Plumber
Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #33 on: November 21, 2017, 08:46:32 pm »

No, when used in Mono mode, a crown amp uses 1+ and 2+ as positive and negative, respectively. The negatives aren't used.

I'm aware of this, but I am totally opposed to running amps in bridged mono mode so I ignored that possibility. The reason most people are impressed by how much louder their system sounds in bridged mode is because with few exceptions bridging the amp gives you 6dB of input gain relative to stereo mode. This does not impact maximum output, it is only input gain. It is the same as turning up the volume. The loss in flexibility in the loads you can drive and the loss of an amp channel for other uses are too high a price to pay.

Mac
Logged

Chris Grimshaw

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1285
  • Sheffield, UK
    • Grimshaw Audio
Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #34 on: November 22, 2017, 03:34:06 am »

I'm aware of this, but I am totally opposed to running amps in bridged mono mode so I ignored that possibility. The reason most people are impressed by how much louder their system sounds in bridged mode is because with few exceptions bridging the amp gives you 6dB of input gain relative to stereo mode. This does not impact maximum output, it is only input gain. It is the same as turning up the volume. The loss in flexibility in the loads you can drive and the loss of an amp channel for other uses are too high a price to pay.

Mac

Mac,
I've no idea where you got that from, but it ain't right.

Bridging an amplifier gives you 6dB more output from the amplifier.
You're effectively putting the two channels of the amplifier in series, doubling the voltage output.

Since P=V*V/R, when you double V (voltage), P (power) quadruples. That's your +6dB.

Sure, there are downsides. Each side of the amplifier effectively sees half the load impedance, so the amp is working harder. Pretty much anything will run bridged into 8ohm, though - each side is seeing 4ohm, which is fine. If you want to bridge into 4ohm, each side is seeing 2ohm, which is a tough life. A lot of amps will do it for "easy" program material, but if it was EDM at the limiters all night I'd have to have something really durable to start the gig bridged into 4ohm (or on 2ohm/ch). MA5k as a minimum.

I'd also argue there's an increase in system flexibility. Bridging amps means you've got spare channels that are currently in use. You can free them up by switching to normal output. You'll lose some output, sure, but you've got your emergency amplifier channels right there.

Chris
Logged
Sheffield-based sound engineering.
www.grimshawaudio.com

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 8911
  • Atlanta GA
Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #35 on: November 22, 2017, 08:51:32 am »

Mac,
I've no idea where you got that from, but it ain't right.

Bridging an amplifier gives you 6dB more output from the amplifier.
You're effectively putting the two channels of the amplifier in series, doubling the voltage output.

Since P=V*V/R, when you double V (voltage), P (power) quadruples. That's your +6dB.




Chris
Not exactly.

The total output capability of the amp DOES NOT CHANGE when you go bridged.

ONLY the ability to deliver greater voltage into certain impedance loads.

It is totally load dependent.

Another good case of "it depends".

Over the years I have seen all kinds of people tearing up gear because they don't understand bridging, how it works, how to hook it up etc.

The most common is when people hook up speakers normally, and then simply flip the "bridge" switch, thinking they are getting more power.

But in reality it is a trip to the recone shop, because they overdrive the speakers due to the cancellation.
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Jeff Schoonover1

  • Full Member
  • ***
  • Offline Offline
  • Posts: 127
Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #36 on: November 22, 2017, 09:35:52 am »

I'm aware of this, but I am totally opposed to running amps in bridged mono mode so I ignored that possibility. The reason most people are impressed by how much louder their system sounds in bridged mode is because with few exceptions bridging the amp gives you 6dB of input gain relative to stereo mode. This does not impact maximum output, it is only input gain. It is the same as turning up the volume. The loss in flexibility in the loads you can drive and the loss of an amp channel for other uses are too high a price to pay.
*from a curious, not condescending perspective :) * I'd like to see the math on that.  AFAIK, with the input signal being equal, if you quad the power you will attain a 6dB gain boost. (most don't quad the power either, it's more like X2 or X3 for 3-4 dB)  This is hardly a reason to use bridging for a volume increase.   But (aside from extra distortion) it is absolutely valuable for driving loads with higher power handling to have more headroom.  I am aware of the input summing feature, and if used, it provides a 6dB boost in the input to the channel.  It won't give more output, it just reduces input headroom, so I understand what you're saying there, but it can be useful in attaining more gain on a lower level signal to get the most out of the amp.

I also agree with you that, in this instance, it is far better to Bi-amp, (using an active X-over) rather than using a mono input with passive.  Very noticeably, actually, as I just did both.  BUT - you may have missed that I'm trying to gain flexibility out of my system.  When I can use my whole rig, there is one amp for lows (2x18, bridged into 4-ohms) and this amp for highs, which will be bi-amped at 16-ohms into the highs, and 4-ohms (maybe 16, haven't totally decided) into the lows, as you say.  Other times though, I will only use one amp.  One side will drive a single 15", and the other will drive this box, hence the passive x-over.  Sacrificing volume and cutting the physical size of the rig by 2/3. No, it won't sound as good, but in those instances, a drop in clarity is acceptable if I'm working on a small club stage or in low volume.
The total output capability of the amp DOES NOT CHANGE when you go bridged.  ONLY the ability to deliver greater voltage into certain impedance loads.
Over one channel - but if you're adding another channel, don't you also increase the *available* voltage for the load?  I get that the overall power availability from the whole amp doesn't change, but each channel divides to half of the input potential from the wall in stereo mode, doesn't it?
I have seen all kinds of people tearing up gear because they don't understand bridging ... ... when people hook up speakers normally, and then simply flip the "bridge" switch, But in reality it is a trip to the recone shop, because they overdrive the speakers due to the cancellation.
I have never once done this.  I don't even know what you're talking about [wink]
Logged

Mac Kerr

  • Old enough to know better
  • Administrator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 6640
  • Audio Plumber
Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #37 on: November 22, 2017, 09:36:28 am »

I'd also argue there's an increase in system flexibility. Bridging amps means you've got spare channels that are currently in use. You can free them up by switching to normal output. You'll lose some output, sure, but you've got your emergency amplifier channels right there.

Chris

Except your racks and speakers are wired in a way that means you can't use those channels.

Mac
Logged

Jeff Schoonover1

  • Full Member
  • ***
  • Offline Offline
  • Posts: 127
Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #38 on: November 22, 2017, 10:37:25 am »

The new drawing.  The only 6-pole double-throw switches I can find are on Mouser for some obscene amount, like $500 or something.
It looks like I'm stuck using two switches - a 4-pole, and a 2-pole unless someone knows a better way while still using one 4-pole Speakon input...
The good news is that it can be wired so that if some goofball (me) forgets to flip BOTH switches, nothing bad will happen, there just won't be sound.
Logged

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 20719
  • Wichita, Kansas USA
Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #39 on: November 22, 2017, 11:00:43 am »

I'm aware of this, but I am totally opposed to running amps in bridged mono mode so I ignored that possibility. The reason most people are impressed by how much louder their system sounds in bridged mode is because with few exceptions bridging the amp gives you 6dB of input gain relative to stereo mode. This does not impact maximum output, it is only input gain. It is the same as turning up the volume. The loss in flexibility in the loads you can drive and the loss of an amp channel for other uses are too high a price to pay.

Mac

^THIS ^^RIGHT ^^^HERE

Staying in 2 channel mode also makes for fewer "hey, why isn't this working" interruptions to the work day.
Logged
"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

ProSoundWeb Community

Re: Crossover, L-Pad, Impedence, Resistance question
« Reply #39 on: November 22, 2017, 11:00:43 am »


Pages: 1 2 3 [4] 5 6 ... 9   Go Up
 



Page created in 0.108 seconds with 26 queries.