Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Darren Brister]

Hey all,

Long time listener, first time caller. Glad to be here.

I own 14 EV SxA250 and they are end of life.  I figured instead of spending gobs of money on new monitors, or repairing amp modules, I would convert them to passive and then to bi-amp.

I just finished the prototype and of course it does not sound the same as the OEM Sx250 crossover.  EV lists their xover point as Butterworth 18db/octave at 1.6k.  Eminence lists theirs as Butterworth 12db/octave lo-pass with Butterworth 18db/octave hi-pass.

I want to modify the Eminence PXB2 1K6 to get rid of any non-OEM phasing issues and make it sound EV OEM.  What do I need to do to accomplish this?  The xovers look entirely different from each other.

Am I better off just bi-amping them?

Thank you.

[Paul G. OBrien]

Am I better off just bi-amping them?

Yes... at least to figure out what additional mods are needed to make the speakers sound decent.

I used the PxB-1k6 in a 12+1 project but I had to add an L pad with constant directivity EQ on the compression driver and a zobel on the woofer.
The exact component values used for this are very much dependant on the drivers in question so no point listing what I used, and I have a test system to measure the actual speaker response too which is something that isn't really optional if you want good results, this will help with developing a DSP preset as well which will take the speakers to the next level.

I just found a picture of an SX250 crossover and it doesn't look like there is much to it besides the basic crossover and an L-pad to balance the drivers. If that is the case it won't sound exactly like the active version without additional EQ.

[Riley Casey]

Do you still have any working amp modules? If so connect a set of leads to the speaker driver terminals and measure with Smaart or REW or your measurement platform of choice to get the factory curves. Then use your DSP to match those curves. If you really want to use the boxes with passive crossovers you'll then have a starting place to start designing the passive networks.

[Darren Brister]

So I gather that turning a 12db/oct Butterworth on the woofer into 18db/oct Butterworth is not as simple as swapping components on the Eminence xover?

I really would like the option of a passive monitor.  I'm moving and don't have a workshop set up yet, so the easiest route would be to duplicate the Sx250 crossover.  On that note, the only Sx250 (or xover) I can find is on GC at $747.  I'd rather eat a Tide pod than pay $750 for a passive crossover network from 2011.  I will look into recreating this.

Yes, I do still have 14 amp modules.  I may start another thread on a DIY repair of those.  They all seem to have the same problem.

My research tells me that the SxA250 and Sx250 are almost identical in terms of phase and eq. 

[Riley Casey]

So these boxes already have passive crossovers?

[Darren Brister]

They were produced in two forms: active and passive.  If I could get my hands on the passive crossover network in the Sx250, I would duplicate it immediately.  I already have some Eminence PXB2 1K6 laying around and figured since they are close to spec, I could modify them.

[Darren Brister]

So these boxes already have passive crossovers?

This is the part number: F.01U.109.651.

[Darren Brister]

If I cannot modify the Eminence PXB2 1K6 to hit the spec I want, then I am interested in recreating the Sx250 crossover and Lpad circuitry which Mr. Obrien mentioned. I am very interested in having the PCB made.

[Paul G. OBrien]

Here is the passive crossover I found for these online... https://reconingspeakers.com/product/ev-electro-voice-sx250-crossover/
That actually looks a bit too simple to be an 18db 2-way so I wonder if there are other componends on the backside that aren't visible or if it's just a cheap chinese knockoff that doesn't match the factory spec.

The pic below shows how I added the extra parts needed for the Lpad and zobel.

[Doug Fowler]

Hey all,

Long time listener, first time caller. Glad to be here.

I own 14 EV SxA250 and they are end of life.  I figured instead of spending gobs of money on new monitors, or repairing amp modules, I would convert them to passive and then to bi-amp.

I just finished the prototype and of course it does not sound the same as the OEM Sx250 crossover.  EV lists their xover point as Butterworth 18db/octave at 1.6k.  Eminence lists theirs as Butterworth 12db/octave lo-pass with Butterworth 18db/octave hi-pass.

I want to modify the Eminence PXB2 1K6 to get rid of any non-OEM phasing issues and make it sound EV OEM.  What do I need to do to accomplish this?  The xovers look entirely different from each other.

Am I better off just bi-amping them?

Thank you.

I have used both the active and passive versions.  The passive boxes I used (monitors) sounded pretty not so good.

The active versions were pretty good.  And the price point was nice.

[Darren Brister]

My search for Lpad wiring diagram on google yielded a few different results.  Mr. OBrien, would you mind pointing out to me the proper diagram? 

I see what you are saying about missing/unseen components.  Looks like the OEM is sans a coil.

I'll call EV and see if they can produce a diagram of the OEM xover. 

[Paul G. OBrien]

This is the correct L pad diagram below, do a search for an L-pad calculator and you will find lots of examples. Those same sites will often have a bunch more crossover calculators available as well.
The second thing you will need is CD horn correction. The output of a horn mounted compresion driver tends to fall off at the topend so an EQ boost is needed to bring it back up. But in this case that can be done with a slight mod to the Lpad above to gradually remove some of it's attenuation at higher frequencies, and that can be accomplished with a bypass capacitor on the series R1 resistor.

[Paul G. OBrien]

Double post

[Scott Hofmann]

If I cannot modify the Eminence PXB2 1K6 to hit the spec I want, then I am interested in recreating the Sx250 crossover and Lpad circuitry which Mr. Obrien mentioned. I am very interested in having the PCB made.

It looks like Madisound will build passive crossovers from a schematic diagram, so if you can come up with that, you can send it to them for a price quote.
https://www.madisoundspeakerstore.com/xover-design

[Darren Brister]

Excellent.  Thank you for your contributions. Hopefully, I will know the direction I will take tomorrow.

[Douglas R. Allen]

  Not sure if this link has anything in it that can help you. I may have made another post or 2 about them as well so it may be worth a search. The Passive and Active did sound close to each other. I'll ask the person I sold them too if they are still around and if they are I'll take a look at the passive crossovers in them.

Douglas R. Allen

   https://forums.prosoundweb.com/index.php/topic,152713.msg1400552.html#msg1400552

[Chris Grimshaw]

Darren,

If you have somewhere to take half-decent acoustic measurements, you can design your own crossovers. The equipment required would cost less than $100.

Here's the step-by-step:
- Download REW and XSim (assuming a Windows computer)
- Buy a USB audio interface with 2x mic inputs. I use a Behringer UMC202HD. Others are available.
- Buy a measurement mic. Even the cheap ones are fine in the range we're looking at. I use a Beyer MM1, but others are available.
- Once you're familiar with performing acoustic measurements with REW, take the following measurements: woofer only (wired direct to the amp), tweeter only (again, direct to the amp. Start at 500Hz, keep the levels sensible), and then both the woofer and tweeter wired in parallel. It's worth taking those measurements over a range of mic positions, but that will cause repetitions of later steps. Do not change any levels between sweeps.
- Next, make up an impedance jig. I used a pair of cheap guitar cables cut in half, and a 100ohm resistor. The wiring diagram is in REW's Help file.
- Measure the impedance of the woofer and tweeter.
- Import (as frd and zma files) the woofer, tweeter and woofer+tweeter curves into XSim
- Onscreen, wire the woofer & tweeter in parallel to the amp, and then use the drop-down to also show the woofer+tweeter curve
- Use the "mod delay" on the woofer or tweeter to get the summed curve (usually blue) to match the woofer+tweeter curve as best you can. This is an important step: REW will null out any acoustic offsets between the drivers, but those acoustic offsets are important in crossover design.
- With your delays found, you can use XSim to simulate passive crossovers. I can't tell you from the outset what's going to work, because these things vary a lot. Once you've got a circuit you like, try replacing the FRD files with the off-axis measurements (NB - you'll need to adjust the relative delays again) and see how things hold up.

If you get stuck, let me know. If you drop the FRD and ZMA files in an attachment here, I'll probably do the crossover for you.

Chris

[Jeremy Young]

Hi Darren, I own four SX250 cabinets and four SXA250 cabinets.  I’ll be pulling them out a week from now for scheduled maintenance.  I’ll try to get some photos of the crossover inside the SX250 for you if that will help. 

[Jim McKeveny]

Why are the amp modules failing and what is the "gob" of money to repair them. 14 factory-matched self powered monitors is a good start. Any DIY "solution" will introduce numerous fresh problems.

[Jeremy Young]

Here are some photos as promised, of the passive crossover network in a stock EV SX250.  Due to attachment size limits, these aren't incredible resolution but if nothing else it will answer the question of whether or not there are components on both sides of the PCB or not (there are). 

[Darren Brister]

So I was able to finally pick up a pair of SX250s. Any questions, let me know. They sound almost as good as the SxA250s.

[ProSoundWeb Community]