Thoughts on external crossovers.

[anto86]

Hi all.

 

I was wondering if anyone would like to share their thoughts on external crossovers.

 

I'm about to build a Trohet R kit by The Speaker Project and I'm considering external crossovers for a few reasons.

 

Being my first DIY build, I would like to play with/tweak the crossovers myself, purely as a learning exercise.  I feel this would be significantly easier if they're not mounted inside the speaker cabinets.

 

Also, at some stage in the future, I'm interested in going to active crossovers and/or dsp for room correction and integration with a sub.

 

The downsides I see are potential driver damage (particularly the tweeter) due to user error, if they were plugged in incorrectly.  To counter this, I was considering going to a 4 pole speakon connector and Canare 4S11 or Mogami W3104 4 core speaker cable.

 

Is there an issue with having both high and low frequencies in the same cable?  Like I imagine there would be if it was a line level signal.  Should I separate the high and low frequencies in two separate cables and colour code to avoid getting it wrong?

 

Thanks in advance for any thoughts.

 

Anthony.

[mwhouston]

Best way to go with Xovers external.

[rantan]

@andyr

[andyr]

10 minutes ago, rantan said:

@andyr

 

Thanks, r.    (I always like pushing my religion on others.   )

 

2 hours ago, anto86 said:

Hi all.

 

I was wondering if anyone would like to share their thoughts on external crossovers.

 

I'm about to build a Trohet R kit by The Speaker Project and I'm considering external crossovers for a few reasons.

 

Being my first DIY build, I would like to play with/tweak the crossovers myself, purely as a learning exercise.  I feel this would be significantly easier if they're not mounted inside the speaker cabinets.

 

Absoloootely!    In addition I suspect the spkrs will sound better when the XO components are not being bombarded by sound waves inside the box!  (Linn proved this in the 80s with their 'Isobariks'.)

 

The only downside is that you need some additional spkr cables - ie:

• cables from the amp to the XO box
• then cables from the XO box to the spkrs.

 

2 hours ago, anto86 said:

Also, at some stage in the future, I'm interested in going to active crossovers and/or dsp for room correction and integration with a sub.

 

In which case ... you just bypass the external passive XO box.  But of course ... you will need a second power amp, in an active setup.

 

2 hours ago, anto86 said:

The downsides I see are potential driver damage (particularly the tweeter) due to user error, if they were plugged in incorrectly.

 

True.  But at low levels ... it shouldn't hurt the drivers - merely sound weird.

 

2 hours ago, anto86 said:

To counter this, I was considering going to a 4 pole speakon connector and Canare 4S11 or Mogami W3104 4 core speaker cable.

 

If you're not thinking straight ... you could wire them up wrongly from the start - and have that same problem!  

 

I suggest it's no more likely that you wrong-connect when you have 2 pairs of binding posts and separate wires - as long as you take your time and think clearly.

 

2 hours ago, anto86 said:

Is there an issue with having both high and low frequencies in the same cable?  Like I imagine there would be if it was a line level signal.  Should I separate the high and low frequencies in two separate cables and colour code to avoid getting it wrong?

 

As spkr wires carry current (whereas line level cables (interconnects) carry voltage) ... I would think that there are greater issues using 4-wire spkr cables, than 4-wire interconnects.

 

You could identify the tweeter & woofer spkr cables by, say, making the woofer cables thicker than the tweeter cables; I do this in my systems - and I could make up some suitable spkr cables for you, if you'd like.

 

[Keith_W]

Why don't you run the internal cables to binding posts at the back of the speaker? Label the binding posts WOOFER and TWEETER and there will be no confusion. I have an 8 channel active speaker (modified commercial speaker). Keeping track of all the cables is confusing, so I put masking tape on both ends and label it clearly with a permanent marker. 

[colinm1]

As above ,binding post on back of speaker ,clearly labeled 

then at any time you run dsp,you just go in to the appropriate driver ,

wilson speakers epoxy their x overs to avoid interference ,and no doubt secrets stuff  going on 

with external x over you achieve that ,plus able to change values easily,

always check and double check ,and don’t rush ,

will minimise mistakes 

[cheekyboy]

Hello Anthony @anto86 I made several 2 way standmounts similar to the current Trohet design that I've seen here and I built these around 15 years ago and still use a pair in my second system today [see pics below]. I would stongly advise you to place the crossover network boards external of a small enclosure like the Trohet. At the time I built my first pair, I was experimenting with different crossover components, so it was far easier not to have the crossover network inside the enclosure, but I would have also struggled to easily fit the crossovers inside the enclosures anyway.

 

I carefully differentiate between the mid woofer and tweeter inputs, but you should be careful not to deliver the woofer signal to the tweeter. In the pictures below, the crossover network is housed in the stand base at floor level and the output is at the top of the metal hollow section at the rear of the stand.

 

Cheers,

 

Keith

 

 

 

 

 

Edited July 1, 2024 by cheekyboy

[oukouk]

A sample of what I did to my speakers.. removed the internal crossover to external rebuilt and wired the individual drivers to the rear...  rear connectors arranged as per driver arrangements, i.e. tweeter at top, mids in the middle and woofer bottom - thus minimising mistakes in connecting crossover to drivers.  tagging and colour codes also help.  tweeters are on 1.5mm2 cable, mids and woofer on 2.5mm2.  if you build them you'll know which would go where..

good luck with the project.

rgds

V

 

 

[Auracle]

Can't go wrong with external.

• The pressures generated inside a cabinet are enough to fracture connections on leaded XO components if not secured properly.
• Inductive components will have their values altered should they be placed anywhere near a speaker magnet, throwing out the calculated response curves.
• My favorite;  -ease of maintenance.

Wiring suggestions thus far are more than adequate so long a you take your time and pay attention in areas you are not familiar with. Doesn't cost to ask.

 

Another little tip you can use (depending on how pedantic you may be), is to fasten/secure the internal cables going from the binding posts to the driver terminals, (using adhesive, cable-clamps, etc). Flapping cables will cause issues in time.

 

Have fun!

Edited July 1, 2024 by Auracle
details omitted

[surprisetech]

Attached pic shows my approach when I put together my main speakers about 7-8 years ago.

Needless to say, while this worked well in my 130 Litre towers, it might not be as practical in bookshelf/standmount designs.

 

I built the crossovers into weatherproof electrical junction boxes, then embedded them in the rear panel of the speaker boxes using polyurethane glue.

The wires coming into the bottom of the junction box (from the input terminals and the speakers) pass through a weatherproof cable gland to provide a seal.

The junction box is quite solid and rigid.  Nevertheless, inside the speaker box, the rear of the junction box and area around it, is covered in an adhesive bitumen deadener and then a layer of thick felt so that the integrity of the speaker box is not compromised.

 

This approach avoids having a separate external box, but still provides easy access to the entire crossover and was great when doing the testing and tweaking once the speakers were up and running.

 

The box is 55mm deep, but being embedded, it only protrudes 20mm with the cover fitted.

 

Edited July 2, 2024 by surprisetech

[anto86]

Thank you all, I'm blown away by the number of responses here.

 

I definitely have no hesitation to go external now.

 

I've attached a pic of the crossover components for both channels laid out on my coffee table.  Approximately an A4 sheet per channel, usually split in half and mounted on each side of the speaker cabinet.

 

As for my speaker cable question, I'm still leaning towards speakon connectors.  I don't know if it's my industrial electrical background or not, but locking and insulated connections are appealing.  I'm thinking I'll go a 2 pole connector for each driver and just colour code and label to prevent mistakes.

 

And while it seems like a good idea to make the connections idiot proof (particularly in my line of work), odds are, it will only ever be me making said connection.  Hopefully I'm not the idiot...

 

As far as the construction and wiring go, I'm not concerned.  I'm well versed in terms of complex circuitry, multi core cables and testing and verification etc.

 

Where I'll struggle with the build will be the speaker cabinets themselves, but I'm hoping they're manageable too.  I'll do my best to make a build thread and document what I can.

 

Anthony.

[andyr]

2 minutes ago, anto86 said:

Thank you all, I'm blown away by the number of responses here.

 

I definitely have no hesitation to go external now.

 

I've attached a pic of the crossover components for both channels laid out on my coffee table.  Approximately an A4 sheet per channel, usually split in half and mounted on each side of the speaker cabinet.

 

 

Look like good quality components!  

 

Only one issue - there are lots of inductors ... and when they are close, they need to be oriented in different directions, so as to minimise interaction.

 

So:

1. there are 3x medium-sized inductors on the RHS of each XO.  The middle one of these should be mounted vertically ... facing side-to-side (so parallel with the inductor in the top left).
2. I would also suggest the inductor at the bottom should be rotated 90 deg.

 

[anto86]

5 minutes ago, andyr said:

 

Look like good quality components!  

 

Only one issue - there are lots of inductors ... and when they are close, they need to be oriented in different directions, so as to minimise interaction.

 

So:

1. there are 3x medium-sized inductors on the RHS of each XO.  The middle one of these should be mounted vertically ... facing side-to-side (so parallel with the inductor in the top left).
2. I would also suggest the inductor at the bottom should be rotated 90 deg.

 

I'll take that on board. 

 

How it's laid out in that picture is per the kits instructions.

 

I've ordered some fibreglass perf board, approximately A4 sized.  When it arrives I'll lay out the components and likely ask for some feedback.

 

Thanks again.

 

Anthony.

[duderduderini]

Hey When I build speakers i mess with inductor values and often change out caps to refine sound- I also will place resistors is series with tweeter/mid to reduce their output level if they are too bright. This process often takes weeks till I am happy, So why on earth would i have anything but an external crossover?

[Keith_W]

I once visited an audiophile who DIY'ed his own speakers. He was still developing his crossover - it was an unholy contraption held together with crocodile clamps and duct tape. Not a single solder joint in sight. 

After listening for a while (and him saying "it sounds soooo gooooood!!") I said "I think the tweeter on your left is not connected". Sure enough, the crocodile clamp had slipped and the tweeter was not connected. Oops. 

[BioBrian]

There's some good and amusing advice above. A very interesting topic for me, thanks everyone.

 

I've been using external XOs for quite a few years now, since going it alone with box and XO design. They can look as good or messy as you like. One advantage that hasn't been mentioned so far is that the speakers are much less likely to get knocked off by the the casual burglar!

 

They are of course great for tweaking - I have spent many hours measuring with Dayton's Omnimic on the computer, doing a sweep then dashing over with a hot soldering iron to make adjustments, comparing graphs with each change, and wondering about it all until the next session.

 

I've come to like the Speakon connectors, after finding better quality ones than those that initially put me off. I've spent about 15 years using Anderson connectors (low mass, high current capability, self-cleaning contacts etc), so the changeover is quite expensive, but both these and the 'push, twist-and-click' of Speakon are so much better than the retarded design of binding posts!

 

I also like the Canare 4S11 cable, but I use it as 'star-quad', where you wire the 2 reds together, and the 2 whites together. These are opposite in the cable layout, so there's a benefit with low inductance. There's no problem mixing highs and lows in the same cable; that's what the amplifier delivers anyway, and all you need to watch is that the cable is of adequate gauge to carry the current with lots of headroom.

 

You can have the XO at the amp end, or the speaker end; I've done both. I've tried to use direct wiring where possible - taking the cables through glands in the XO box rather than use yet another set of those awful binding posts. The only problem with having the XO box at the amp end is that you need double the amount of speaker cable from there to the speakers.

 

With the XOs themselves, I do what Troels Gravesen does: build them on Baltic Birch ply bases. I use 12 mm thick, as it's really stiff at this size, and not big enough an area to foster vibrations. I use Fuller Ultra Clear tubed 'glue' to fix components. It's a semi-flexible acrylic that comes out white and dries clear, and holds your component solidly, but damping vibration and allowing small movement so stresses can't build up. There are other glues around - Sika make a good one, but I haven't tested it on the very slippery surfaces like caps.

 

I personally find cable-ties a bit tacky, both to look at, and I've seen them deteriorate to the point of failure. You do need an adhesive. I've personally found that hot-melt glue is prone to failure and is very messy to use; you never really know if it's stuck properly or not.

 

You have a nice collection of coils, some of which are quite heavy. I recommend drilling a hole in your board and gluing in a dowel (PVA), and using the soft glue to place the heaviest coils horizontally around that. Then they won't fall off, even with the most demanding music...

 

I'll post this pic of some of my efforts in development, showing both types of connectors and a temporary XO for a Centre woofer box. (All 3 of these have 15" woofers, with 3-ways above. That Centre baffle now has a box behind it and makes proper music!).

 

 

All the best with progress on your build.

 

[Stepping3D]

@andyr the Trohet R seems like a great speaker. I’m considering building one myself. Have you had a chance to build the crossovers and did you end up playing around with orientation of the inductors or strictly per the diagram? I’ll be keen to hear what you think about the upgrade if you have any thoughts…

Edited July 30, 2024 by Stepping3D

[andyr]

28 minutes ago, Stepping3D said:

@andyr the Trohet R seems like a great speaker. I’m considering building one myself. Have you had a chance to build the crossovers and did you end up playing around with orientation of the inductors or strictly per the diagram? I’ll be keen to hear what you think about the upgrade if you have any thoughts…

 

No, Jimmy - I haven't built the 'Trohet R' XO ... but I have built other XOs.

 

My suggestions re. inductor orientation are simply "best practice" ... to avoid interaction between different inductors.

 

[Stepping3D]

20 minutes ago, andyr said:

 

No, Jimmy - I haven't built the 'Trohet R' XO ... but I have built other XOs.

 

My suggestions re. inductor orientation are simply "best practice" ... to avoid interaction between different inductors.

 

That’s great to know! I’m about to embark on my first build, so any info is appreciated.  I’ll have to do some more research to understand this a bit better.

[anto86]

@Stepping3D im the one about to build the Trohets R's.  I'm also located on the Gold Coast, so if you'd like to have a look at the kit, reach out.

 

I've delayed starting construction a little.  I've got my first child arriving in about 3 weeks, hopefully I'll find a little time soon.

[andyr]

1 hour ago, anto86 said:

I've delayed starting construction a little.  I've got my first child arriving in about 3 weeks, hopefully I'll find a little time soon.

 

Take it from me ... you'd better find time now - before that baby comes along!  

 

[BioBrian]

 

1 hour ago, anto86 said:

I've got my first child arriving in about 3 weeks, hopefully I'll find a little time soon.

 

Classic! All the best with that; I'm sure we'll all be keen to hear how the two adventures can find harmony.

 

With apologies to all:

 

Anto had an urge

A surge was ready 

There was a bulge

The bulge was heady

[Allan]

[Allan]

here's a test showing coils coupling and how it effects their value

the excellent rule of thumb.. we should not be able to see one coil through the centre hole of another

 

 

[almikel]

Anyone interested in passive crossover design or implementation should read Rod Elliot's article: 

https://sound-au.com/lr-passive.htm

 

On 01/07/2024 at 2:03 PM, anto86 said:

Also, at some stage in the future, I'm interested in going to active crossovers and/or dsp for room correction and integration with a sub.

Anyone interested in active crossovers should also read Rod's article on bi-amping:

https://sound-au.com/bi-amp.htm

It's "old school" now - no-one uses analog active filters these days - but the LR4 active Xover ruled in the pro world for decades.

 

I ran fully active for a long time, but introduced an external passive crossover on my Redspade PSE144's to reduce complexity.

 

Mike