Polk LS Series, Active Crossovers

soiset

I want to mod my range of LS speakers (5 pair of LS50's, and two CS350LS to bi-amp with electronic/active crossovers. To do this, I imagine I need what Polk calls "proprietary info," but I figure there isn't much harm in asking:

For a two-way crossover on the LS50, and for the CS350LS, what crossover point should I use (I know it's something like 3500-4000 Hz per the sales lit)?
What crossover slope should be used (really need this, b/c it isn't adjustable on the active xovers)?
What are the nominal impedances of the individual drivers, or barring that, can this info be found with a multi-meter?

I figure I'll end up getting a slew of pro-audio electronic crossovers (aka Furman, or Rane) to get the job done. I'll also have to get new speaker terminals to replace the original crossovers/terminals. Below 80 Hz, the bass management of my receiver will send all the sound to my pair of PSW1200's, effectively making a neato tri-amped system.

Thank you

Systems

If you are going active I would use 4th order linkwitz- riley slopes and try to crossover closer to 2-2500hz if possible.
Also You do not really need to know the impedance of the drivers because an active crossover only sees the input impedance of the amplifiers not drive units.
btw. It may be worth taking a look at the Behringer CX2310 .It is a decent performing unit with LR4 slopes ,is inexpensive and has front panel adjustable crossover points. http://www.behringer.com/CX2310/index.cfm?lang=ENG

soiset

Thank you. That is a really low price for an electronic crossover (except for some car audio models). I will look into it. What I wonder, though, is if the tweeter can handle the lower freqs that you suggest.

phoneisbusy

I think the crossover schematics are available in the troubleshooting section. You might be able to get more insight from them.

Good luck.

Dave

soiset

phoneisbusy wrote:

I think the crossover schematics are available in the troubleshooting section. You might be able to get more insight from them.

Good luck.

Dave

Holy flirking schnit! Where did he get all of those? Thanks for the pointer; I did not know that those had been posted.

Systems

soiset wrote:

Thank you. That is a really low price for an electronic crossover (except for some car audio models). I will look into it. What I wonder, though, is if the tweeter can handle the lower freqs that you suggest.

With the steep 24 db cutoff you can cross the tweeter over quite a bit lower but 2k might not be a good idea .It really depends on the resonant frequency of the tweeter you are using.
Using a lower crossover point improves the speakers off axis dispersion and reduces vertical lobing problems,but it also makes tweeter work much harder.It is a trade off.

ben62670

I am going to be getting these in by Friday. They are in line passive 12db crossovers. They require no power, and create no ground loop problems. I am currently using an active crossover. I just don't like the idea of another piece of equipment in line with amplification.
Ben
http://www.partsexpress.com/webpage.cfm?WebPage_ID=3

soiset

Hello again, Ben. I just talked with Steve Macatee director of new product development at Rane, about multi-channel active crossovers. If I go the route of the common stereo active crossovers, I'll end up buying 6 metal boxes. Looks like they can be had on ebay for about $50, so I'd end up spending $300-400 to get enough to biamp my whole theater.

Steve at Rane said that they only make DSP multi-channel crossovers that are intended for pro installation, and are set up by PC (no knobs). He said DBX makes one with knobs (can't remember if it is analog or not) that I am now going to look for.

Systems

Im currently running a 4way(yes 4way)active system for my main left and right channels and will soon have a 3way active centre channel up and running.The active approach certainly add's to the complexity of the system but the performance advantages are well worth it.

soiset

I don't think it adds much complexity, just one more box between preamp and amp that you set once and leave. When you consider that you remove the passive crossovers, I think it's a wash.

I have really begun discovering how much pro gear can add to a system, and how little it costs compared to so much snake-oil enriched regular home audio gear.

Systems

soiset wrote:

I don't think it adds much complexity, just one more box between preamp and amp that you set once and leave. When you consider that you remove the passive crossovers, I think it's a wash.

I have really begun discovering how much pro gear can add to a system, and how little it costs compared to so much snake-oil enriched regular home audio gear.

Don't forget that each driver will need its own channel of amplification.You will have to add at least another stereo amp for a two way active speaker ,a single stereo amp is not enough.
I need 7 amplifier channels to run my mains only.That to me is comlexity.:)

soiset

Update:
I am collecting Rane crossovers, and will soon remove the crossovers from my LS50's and wire directly to the drivers. I just grabbed a Rane MA-6 for six channels of amplification at a very modestly rated 100 WPC x 6. That, with an Adcom GFA-5400 (from Ben62670, right here in River City), an Adcom GFA 545, and a Yammy m-45, round out 12 channels of mid-bass to mids, plus two Adcom GFA 2535's and two GFA 535's for 12 channels at 60 watts makes for 12 bi-amped channels. Toss in a Hafler P7000 driving two Polk PSW-1200's, and well, that is what it takes for some serious HT sound.

I guess I'll be unloading the PSW-1200 plate amps soon.

joeparaski

GV#27 wrote:

Im currently running a 4way(yes 4way)active system for my main left and right channels and will soon have a 3way active centre channel up and running.The active approach certainly add's to the complexity of the system but the performance advantages are well worth it.

Hey GV, what speakers are you using to go 4-way?

Joe

Systems

Hi Joe in la belle province.It is a DIY design and if you check out my DIY center channel thread in the Diy,Tweaks area I list the drivers I use.My Idea was to build something similar to the Aurum Acoustics
speaker if you are familiar with them.

Btw I think you need more SAE pieces.Back in the early 80's I really wanted a rack full of their stuff but finances didn't allow. I cant remember the exact model numbers but they looked real hi tech.And I bet those ESS's are probably very rare these days.

soiset

I'm going to be running the SL6000 tweeters in the LS50's with the little Yamaha M35/MX35 4x20 amps. What is the rated impedance of this tweeter?

The pairs of MW6000(?) 6.5" woofers will be run by Rane MA6 6x100 amps. I would anticipate better results running at an 8 ohm config than a 4. If these are two 4 ohm drivers, I'm set. Anybody know what they are?

soiset

I'm up to 3 Rane AC-22's now, so I just need one more. I just discovered, though, the BBE DS48, which allows four inputs leading to 8 out, which would do the same job as 4 Ranes. It would also let me set the crossover slopes, if I needed to. It also allows control of "attack, release, and threshold parameters," but I really have no idea what all that means (any help?)

My only concern about the BBE over the Rane units is that if one thing goes wrong in its circuitry, my whole system is out.

I've been looking into speaker connections to replace the input/crossover on the back of the LS50. No biamp terminal cups will fit into the same hole, and I am not going to cut the hole larger. However, I could make a plate, drill four holes in it, and put the binding posts through the holes. The plate would be larger than the original hole, and could be attached with wood screws to the cabinet.

More on that later. It's time to walk the dogs.

soiset

I have actively bi-amped a pair of LS50's now. I used the Rane AC-22 2-way, and I have a Rotel RB-971 on the highs, and a 981 on the low/mids. 80Hz and below is taken out before the Rane by the outboard amp/crossover of my Velodyne ULD-15.

I used aluminum plates from Wellborne Labs for my binding posts, which are WBT knock-offs (Exodus Audio from DIY Audio). The bottom pair of drivers runs at lower impedance than the single top tweeter, but this doesn't seem to be an issue.

My room is not nearly ideal, but listening so far, I would say that the clarity and detail of the highs is the most noticeable difference. Tori Amos on "Under the Pink" sounds magnificent, especially the piano. I've though that maybe male voices sounded a little "canned" though (maybe). But that could be the room.