Jump to content
la bam

PA 4ohm linkage

Recommended Posts

Hi all, not sure where to put this as theres no real PA section, so this seemed closest.

I've just bought a second hand pa. 2 tops and 2 subs.

The cabs are 4 ohm each, but have 2 connections on each cab (a + and -). Well in truth they have 4 - 2 speakons and 2 of those old 3 pin connectors.

Question - if I was to link these (top to sub etc) are they designed to stay at 4ohm load, or do they drop to 2?

Also, the tops work fine on usual 2fc speakons, but the subs only work on the 3 pin. Could it be the subs are powered using the 4fc speakons? (or whatever variant it is).

If it helps it's an old model, a hk linear L24 and L30.

Any help appreciated.

Share this post


Link to post
Share on other sites

Are these powered? I assume not, as powered don't specify impedance. If that's the case you can't link the tops and subs, you have to separately power them, using an electronic crossover to send the lows to the subs amp, the rest to the tops amp. Also, be aware the the way you see 99 out of 100 bands set up their PA, with the mains above the subs. is incorrect. The mains should be pole mounted to the front left and front right, the subs placed together, preferably next to a wall to one side.  

  • Like 3

Share this post


Link to post
Share on other sites

Thanks bill.

These have an IN and OUT on them though?

I remember years ago, I had some cerwin Vega subs that were similar.

I've no idea on whether or not the subs or tops have a built in crossover like some cabs do. Theres no info on them. I know they're probably 20 years old and from a time when HK Audio (Harmon Kardon) and Hughes & Kettner where the same company in the same building.

I've been out of the passive pa game for a while. I agree powering the tops and subs separately with a crossover and 2 amps is probably the way to go unless I can find any info.

Share this post


Link to post
Share on other sites

Ok, thanks.

I'll take the back of the subs and see what's in there.

Edited by la bam

Share this post


Link to post
Share on other sites

It sounds like the old Peavey system we used to have in an old band. Passive subs with a crossover, linked to passive tops. 4Ohm each side, total load 2Ohm with everything plugged in.

When you say 3-pin connectors, do you mean XLRs? These are not power connectors, neither are speakons. If they were powered there would most likely be a female IEC connector. Some pictures might help.

Share this post


Link to post
Share on other sites

I remember having a peavey UL system linked like this.

No, the 3 pin look like xlrs but are also the same cables you find on old bass cabs and amps, like older trace elliot's.

I'll try and get some photos, thanks.

  • Like 1

Share this post


Link to post
Share on other sites
11 minutes ago, la bam said:

I remember having a peavey UL system linked like this.

No, the 3 pin look like xlrs but are also the same cables you find on old bass cabs and amps, like older trace elliot's.

I'll try and get some photos, thanks.

Maybe post a pic of the connections at the back of the speakers & subs?

 

Share this post


Link to post
Share on other sites

Photos of the back of one of the subs.

The x2 on the left of the inside shot are the 3 pin xlr type. The 2 on the right are the Speakon.

20200210_093000.jpg

20200210_092933.jpg

  • Thanks 1

Share this post


Link to post
Share on other sites

Ahhh, looking at this below, the subs connections - the wires to the speakers only go from the 3 pin connectors. 

 

20200210_095547.jpg

Share this post


Link to post
Share on other sites

I tried to find the user manual online, but no joy, am afraid. :(

I'd guess that you'd need to power the tops separately from the subs, either via a powered crossover, or a power amp/s.

Bill is the man though.

Share this post


Link to post
Share on other sites

Thanks, I couldnt find anything either. Problem is the sub speakons dont seem to work as they are wired at the moment.

Share this post


Link to post
Share on other sites

They're all parallel, no crossover. If the speakons don't work you may not have the right connection on the cable plug. Those are four pole. According to the diagram 2+2- are connected to the driver, 1+1- are pass through, so you can use a four conductor cable to send both the low and high frequency signals from a breakout panel on the amp rack to the subs and then just a two conductor cable from there to the mains.

Share this post


Link to post
Share on other sites

Thanks Bill, someone in an hk group, suggested the tops are connected +1 and -1 and the subs +2 and -2.

I've just tried 4 core cable (had one lying around) and it works fine into the top from the amp, then works fine from the top into the sub via the link, but not the amp direct to the sub.

 

Share this post


Link to post
Share on other sites
21 hours ago, Bill Fitzmaurice said:

 Also, be aware the the way you see 99 out of 100 bands set up their PA, with the mains above the subs. is incorrect. The mains should be pole mounted to the front left and front right, the subs placed together, preferably next to a wall to one side.  

This comment got me interested in why subs shouldn't go under tops, and I found this SOS article on sub placement.

https://www.soundonsound.com/techniques/bass-place

 

Share this post


Link to post
Share on other sites

I would recommend you contact John Hornby Skewes who are UK distributor for HK, and get a copy of the documentation for the cabs in question - I have recent experience of using their(HK) active PA cabs, and the correct wiring scheme is somewhat counterintuitive and doesn't fall in line with standard convention or the labelling on the plate amps.

Edited by SubsonicSimpleton

Share this post


Link to post
Share on other sites

Yes, it took some working out.

However, I think weve worked it out now.

Tops run on +1 -1.

Link is +1 -1 +2 -2.

Subs are +2 -2.

My only thing left to work out is how to power them now.

Do I use:

1. x4 amps (1 for each cab) will it be ok running one channel at 4ohm?

2. x2 amps capable of running down to 2 ohm (1 for x2tops and 1 for x2 subs).

3. Are there any other ways? Could I use x2 amps put power them daisy chained? Ie 1 top and sub per amp, but one one channel.

4. Any other ideas?

Share this post


Link to post
Share on other sites

Whilst I am sure someone will either correct me, or better still a diagram, here's my 10 penneth. As PA Amps are usually 2 channel, ie: Left and Right You can use 2 amps that will run down to 4 Ohms on each channel and connect them up as below using a Crossover to split the frequencies.

I Amp to power the tops, (Left and Right) and 1 amp to power the Subs, (Left and Right). It doesn't matter that the subs should be placed together, this is just to explain the linking up.

So you would come out of your mixer, Left and Right, into an electronic crossover, and then Lows to one amp and Subs,  highs to a second amp and Tops.

Edit: Found a diagram I did a while ago which hopefully will explain.

PA Basic Diagram.pdf

Edited by BassBunny

Share this post


Link to post
Share on other sites
11 minutes ago, BassBunny said:

Whilst I am sure someone will either correct me, or better still a diagram, here's my 10 penneth. As PA Amps are usually 2 channel, ie: Left and Right You can use 2 amps that will run down to 4 Ohms on each channel and connect them up as below using a Crossover to split the frequencies.

I Amp to power the tops, (Left and Right) and 1 amp to power the Subs, (Left and Right). It doesn't matter that the subs should be placed together, this is just to explain the linking up.

So you would come out of your mixer, Left and Right, into an electronic crossover, and then Lows to one amp and Subs,  highs to a second amp and Tops.

Edit: Found a diagram I did a while ago which hopefully will explain.

PA Basic Diagram.pdf 5.22 kB · 0 downloads

Yes, that's what I was thinking.

Just weird that they build in the links to connect the tops to the subs but that then makes this system 2 ohm per side per one input from the amp which is unusable for any amp (combined 1ohm).

Share this post


Link to post
Share on other sites
1 hour ago, la bam said:

Yes, that's what I was thinking.

Just weird that they build in the links to connect the tops to the subs but that then makes this system 2 ohm per side per one input from the amp which is unusable for any amp (combined 1ohm).

It might be that the "links" are there so you can use more than one sub/top per side. We had an HK sysyem that had 3 subs/mids and 1 top per side.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.



×
×
  • Create New...