Active crossover for Linn Isobariks

[monstermoo]

I'd like to get an active crossover for my Isobariks, but they are like hens teeth and tend to cost at least £500 plus at this age they would probably need servicing :(

So, I was wondering if there is a DIY route I can explore?

Does anyone have a schematic for an active crossover that would do the job well?

Are there any kits on the market - i.e. ready-made PCB's that would need to be populated with components specific to the Isobarik requirements?

I know next to nothing about what components would be needed, but if I had a list of parts and a board I'm sure creating the crossover wouldn't be too difficult.

I guess I'd need a power supply also - but again, spending £££'s on a NAIM power supply or such like sounds like a painful prospect that I would rather avoid if there are suitable and much cheaper alternatives.

Thanks in advance all! :)

[Labarum]

Google

behringer crossover

They produce programmable crossovers very cheaply.

I am no expert, but I guess they could be made to work.

[The Vinyl Adventure]

I'm experimenting with a rane crossover at the mo ...
I'll post how I'm getting on in here http://theartofsound.net/forum/showthread.php?t=8377 a bit later ....
I'm lead to believe that the behringers arent up to much for home use ... At least that is what Stan Beresford says?? That one of the reasons I went for the rane ... That and steve offered it to me at a very attractive price!

[Reid Malenfant]

I'm lead to believe that the behringers arent up to much for home use ... At least that is what Stan Beresford says?? That one of the reasons I went for the rane ... That and steve offered it to me at a very attractive price!
Apologies but that is just cobblers :eyebrows:

If i can make a simple homemade xover using noisy LF353s on veroboard & get good if not jaw dropping results then the Behringers are going to be even better. They use lower noise & lower distortion opamps & they actually happen to have a case around them which mine didn't :rolleyes:

Nuff said :lolsign:

[The Vinyl Adventure]

:lolsign: I knew that would get a comment from you Mark... Take it up with mr Beresford ;)
How you getting on with your behringers?

[DSJR]

Should I? Shouldn't I?

Well, it's like this. i reckon anyone who has ever compared Briks passive to active, would ditch the passives immediately if they could afford to, the difference is that big in terms of control, reduced colouration/grain and sense of "ease."

I take it that the 'briks are the later ones which can be rendered either with a little bit of soldering? That'll help as the later version mid drivers had a smoother response as I recall.

Now, Naim had simple filter slopes with no eq at all, hence the rather bightly lit tones of Naim tri-amped and six-pack active 'Brik systems. The mid driver is inclined to rise in response and naim didn't eq it flat.

Linn, on the other hand, with the Tunebox, did put some eq in IIRC and also the Bingo cards eq'd the low bass up, which could make you seasick on some LP sources.

A Tunebox may be more difficult to obtain, but may be cheaper when you do find one. Otherwise, follow Hamish closely.

[Reid Malenfant]

:lolsign: I knew that would get a comment from you Mark... Take it up with mr Beresford ;)
How you getting on with your behringers?
I'm not using them yet, but as soon as the ARC MP1 gets plumbed in they'll be used to drive the KSA250 on bass duties & the 6 channel Parasound HCA1206 to drive upper bass, mid & tweeters ;)

I have absolutely no doubt that once i set it up (with a function generator & oscilloscope to get xover frequencies bang on) that i'll be having another jaw dropping moment :eyebrows:

The warranty can stuff itself as well, i'll be adding extra circuits to time align the drivers accurately as i did with my veroboard xover. Who cares about a warranty if you can fix it yourself :mental:

[The Vinyl Adventure]

Time alignment ... I have a question here for you http://theartofsound.net/forum/showthread.php?t=8377&page=3
I don't want to steal steves thread when I have my own...

[monstermoo]

Thanks all. I'm not sure that the Rane Xover is the right option for me as it would only give mono sound in 3-way format.

My Briks are very early ones that have had the drivers swapped out for later versions and have been converted to run either active or passive - each speaker has two external crossovers which are plugged in, or it is possible to simply leave these out of the chain when going active.

[DSJR]

In that case, follow the very basic naim filter slopes and you shouldn't go too far wrong.

The Naim crossovers set levels - treble fully up, mid backed off a good bit and the bass backed off a bit more. Setting them all full up makes 'em sound awful.

[Ali Tait]

Check out the Behringer CX3400 on ebay. Not expensive and will do a 3 way.

[The Vinyl Adventure]

the behringer cx3400 that mark has is 3 way stereo if that helps?

[The Vinyl Adventure]

:doh: yeah, what Ali said ..

[Labarum]

This site may be of interest

http://www.behringermods.com/

[The Vinyl Adventure]

He seems a nice bloke that chap, had a long convo with him about modding my behringers dac to be a bit more posh - a long term plan - he was very helpful

[StanleyB]

Apologies but that is just cobblers :eyebrows:

If i can make a simple homemade xover using noisy LF353s on veroboard & get good if not jaw dropping results then the Behringers are going to be even better. They use lower noise & lower distortion opamps & they actually happen to have a case around them which mine didn't :rolleyes:

Nuff said :lolsign:
Jaw dropping results with LF353? :lol:. Fortunately most of us on AoS have a far higher operating standard and expectation :eyebrows:.

[Ikemen]

Monstermoo, Have you considered a PLLXO since you sound like you are not shy of soldering and the like. I am guessing the Linn Isobariks you mention have gentle slopes and a PLLXO is ideal, if not only good for, 6 and 12db slopes.

I too looked at the behringer and Rane xovers but it all became too expensive and complicated mixing pro and home gear for my liking. A few quid in Maplins for caps and a breadboard then a test tone CD and I have huge flexibility to tailor levels, xover points, and slopes. If insertion loss is an issue then you can add a couple of transformers such as the Neutrik NTE-4.

I have attached an Excel file which does the math on ones behalf.

[Reid Malenfant]

Jaw dropping results with LF353? :lol:. Fortunately most of us on AoS have a far higher operating standard and expectation :eyebrows:.
:lolsign: Yeah i do realise they aren't exactly the best op amps in the world Stanley, i just happened to have a hell of a lot of them. In fact they are noisier than TLO72s but they did the job & this was back in the early 90s ;)

Obviously i would use something vastly superior if i was going to tackle the same job again, so please don't get the wrong idea 3031

What i was trying to point out is that the Behringer will be vastly superior to that homemade crossover made back in the day ;)

[monstermoo]

Thanks Sean - that could be another option.

The price of the Behringer CX3400 looks very reasonable to me, but is it likely to sound cr@p out of the box?

[Reid Malenfant]

The price of the Behringer CX3400 looks very reasonable to me, but is it likely to sound cr@p out of the box?
As has been pointed out your Isobariks will likely have slopes of 12Db/octave, maybe 18Db/octave feeding the tweeter ;)

If you plan on using either a Behringer or Rane crossover you'll need to rewire the speaker. Yes, you'll need to do this anyway if removing the crossover, but you'll also need to get the drivers in phase by changing the positive & negative connections over on certain drivers (depending on how they are wired now).

If you don't do this you'll have quite a lot of difficulty setting up the crossover properly & it won't sound at all integrated.

The crossover will simply sound like what you put through it. I'd suggest that like other bits of electronic equipment that a break in period is a good idea, say the usual 100Hrs :)

[monstermoo]

Thanks Mark.

There is abosultely no chance that I will be re-wiring the internals of the isobariks.

The previous owner had enough trouble converting them to be used active or passive (there are 12 banana plugs on the back 4x treble, 4x mid and 4x bass) - and he's an electronics expert - which I'm not :)

So, essentially I would assume that they are ready to go as is.
The passive crossovers (2 per speaker) simply plug in (or are left out when going active).

[Reid Malenfant]

I think you'll need to take a look at the way the drivers are wired up tbh ;)

I'm sure there were commercial crossovers available for the Isobarics & these may well have had similar crossover slopes to the passive crossover. If this is the case you'd need to swap around the positive & negative from the power amps you intend to use on one or more drivers (more than likely) to make good use of a crossover with 24Db/octave slopes.

If you didn't then there will be phase problems between some drivers at the crossover point :(

The thing is we don't know which drivers have reversed polarity right now (if any, but i'd expect some to have), so it'd involve a trip inside the enclosures to find out :doh:

[monstermoo]

I've just heard back from previous owner and he has said they are already set for active use which he did with the original Linn Active Crossover.

Here is the manual - but I doubt if it offers any insight...
http://www.mickandviv.com/pfm/iso_akt_user_manl.pdf

[Reid Malenfant]

Here is the manual - but I doubt if it offers any insight...
http://www.mickandviv.com/pfm/iso_akt_user_manl.pdf
On the contrary, that's just what was needed :eyebrows:

3033

If you click the little thumbnail above you'll see that it gives the crossover frequencies & more importanly the rolloff rate of each section ;)

You can see that from bass to midrange it's 12Db/octave so the midrange will have reversed connections! & you'd need (if using the likes of the Behringer or Rane xovers) to reverse the positive & negative connections to the midrange speaker to get it in phase with a 24Db/octave xover :) As the mid to treble xover is standard at 24Db/octave you'll also need to reverse the connections to the tweeter to keep it in phase with the midrange because as standard they'll be the same as the midrange phase wise & you have just reversed the midrange connections ;)

[monstermoo]

That's great - thanks!

So does that mean I could simply plug positive into negative and vice versa for the mid and treble connections on the back of the speakers?

Would it be easy enough to get the setting right on something like the Behringer C3400? Keeping in mind I have no measing equipment of any kind, how would I know where to set the values? Or would it be a case of adjusting until I was happy with the sound?

Would there be any risk (providing everything was wired correctly in the first place) of frying any of the drivers by having a dial in the wrong position (except volume of course!! ;-) )?

[Reid Malenfant]

That's great - thanks!

So does that mean I could simply plug positive into negative and vice versa for the mid and treble connections on the back of the speakers?
Yes ;)

Would it be easy enough to get the setting right on something like the Behringer C3400? Keeping in mind I have no measing equipment of any kind, how would I know where to set the values? Or would it be a case of adjusting until I was happy with the sound?
This will be much more problematic unfortunately :rolleyes: To accurately set the crossover frequencies i'll be using a function generator & a multimeter. An oscilloscope might help but isn't strictly needed.

You could try setting it up by ear & you should be able to get pretty close to the standard xover frequencies but it'd take time & some patience imo :rolleyes: If you have access to the circuit diagram & component values of the passive crossovers then setting the gain on the active crossover before attempting to dial in the crossover frequencies could get you much nearer straight off from the word go!

Would there be any risk (providing everything was wired correctly in the first place) of frying any of the drivers by having a dial in the wrong position (except volume of course!! ;-) )?
Not really no - that's some good news :lol: