[ka7niq]

I could probably be persuaded to loan Brian my DEQX for awhile if he would like to try his hand at coming up with some settings.

I think if you did, you would be forever famous in the VMPS world!
You know, Newform, a Canadien Ribbon speaker manufacturer, sells a version of their ribbon hybrid for use with the little Panasonic digital receiver and the Behringer Active crossover ?
The VMPS drivers are all very good, and I think a direct drive option might take the VMPS speakers to the 'next level'.

And, as you are aware, a crossover or EQ done in the digital domain does not play by the same 'rules' as an analog one does.

This means that perhaps Brian will elect to use steeper slopes, to take the ribbons further down in frequency, and not have to worry about the phase shift and ringing of a high order crossover done in the analog domain ?

Just for the heck of it, I threw an analog eq in my system tonight.
I gave a slight boost to the 125 hz band.
Maybe 2 or 3 db ?

It really fleshed out the sound, but then, my passives are probably not right.

I am really fussy about the region between 125 and 300hz, it has to be just right.
 I prefer that if a speaker designer has a voicing choice, they make it a little thicker, then to have any dip in this region at all.

I also prefer a very  slightly downward sloping "warmth" curve, if you will.

But, that's just MY tastes, and a direct drive VMPS product with an active electronic crossover, should almost give one total control over the speaker voicing.

And, IF a digital active crossover is used, then a digital EQ like a TACT, or even a VMPS modified Behringer can easily voice the speaker like you want.

Of course, the ribbon mids have mechanical limitations, and I a sure Brian will not want to warranty midrange neo panels that have had 13 db of boost at 160 hz thrown their way, with shallow slopes!

But, I think you get the idea ?

I say send him the DEQX !


Maybe Brian could explore the Behringer crossover, and perhaps have Jim Bongiorno come up with some mods for it, and have a VMPS version of the Behringer, etc ?

[ka7niq]

I'm not sure why using a 24db/octave crossover instead of a 6db/octave crossover will let one drive the bass "harder" (the bass/midbass still has to be level matched with the midrange).  Also, why would this reduce distortion?  It might reduce distortion of the midbass driver, but I doubt it would reduce distortion of the bass driver.  The only way it would reduce distortion of the midbass driver (or the bass driver) is if the 6dB slope allows some distortion to occur above the cutoff frequency.  I'm not convinced that the midbass is going to be distorting because the midbass cutoff occurs at a relatively low point.  So, one would hope that the midbass won't distort until frequencies that are well away from the crossover point.  But I've been known to be wrong in the past. 

As for your soldering trick, that should work.  I believe the coil is in series with the bass/midbass, so shorting the coil bypasses the coil (one of the benefits of a first-order network). 

The reason an external crossover with a higher slope will allow you to drive the woofers harder is this.
As good as the VMPS woofers and midranges are, like all drivers, they have their own sound.
One can only drive the woofers so hard, until they become "heard" up into the midrange.
Turning the pots all the way down, and listening to JUST the woofers at a loud level , will acquaint you with the particular sound of this driver.

With a higher order crossover, it should 'shut up' this driver before it has a chance to play up into the midrange, where it just can't match the ribbons transparency.

What cone driver can ?
And the VMPS made woofer does a great job, I just am always looking to get the best sound I can.

I have very little invested in the active crossover, and plenty of amps, and desire.
If it does not work, no harm done, I will just un do it.

Everyone has a sound they are after, and I am no different.
Personally, I like a lot of body in the upper bass, lower mids.
Remember, I have OLD RM 40's w/o woofer upgrade.

So, In order to get the punchy upper bass/lower midrange fullness I happen to like, it means I must drive my woofers harder.
But, when I do, I pay a price for it up into the midrange!
Also remember, I am in a big room, with speakers 5 feet out into the room.

I think at this point, I may try just removing the bass coil, and use the active crossover on the woofers only ?

I can do this by coming out my preamp with a T, and ONLY have the active crossover in the path of the bass amp.
The other amp will get a un messed with signal, and only drive the ribbons.
'
This seems the easiest way to try at first ?

[ekovalsky]

Having been down this road -- partially with the VMPS speakers and now completely with Nolas -- here are my thoughts

1.  Main advantage of digital crossovers is that higher slopes can be used without screwing up phase response.  Drivers can work over a more comfortable and safe range and therefore can handle more power and play with lower distortion.  You can also completely eliminate high frequency ringing that otherwise cripples metal cone woofers.  I do not think the DSP crossovers are otherwise superior to well designed and implemented analog crossovers.  Now with VMPS speakers what I would suggest is blasphemy to the designer -- use steep slopes, like 36dB/octave, and change cross frequencies to 300-400hz (depending on model) and 3khz.  Personally I thought the planar driver left a lot to be desired at the upper and lower ends of its range, and sound was better when more bass was handed off to the woofer and more treble to the tweeter.

2.  Huge benefit of a digital multi-amped system with DSP crossovers is that precise time alignment and proper group delay can be achieved with all drivers wired in phase.  Now doing this takes quite a bit of work (I can go into detail if anyone wants) but I promise the results are worth it.  You will get seamless frequency response around the crossover regions with measurements, more importantly listening reveals big gains in coherency, pace and rhythm, and timbral accuracy. 

3.  Digital correction permits you to address aberrations related to your drivers and your room.  Room modes in the bass range are the easiest to fix.  Frequency response irregularities of planar magnetic panels (which I did find) and ribbon drivers can be addressed.  At higher frequencies correction is less helpful because combing, lobing, and other artefacts related to speaker design dictate the response rather than the room or intrinsic behavior of the drivers and their resonances.  With the very short wavelengths involved, small offsets from the measurement location can produce massive changes.  With the RM/X I would see 8-12dB swings at some high frequencies by moving the mic about an inch!

4.  Digital EQ allows customization of the sound to your liking.   You do this as a part of the correction process, instructing the device to correct to your target curve rather than to a flat response.  Like "warmth" ?  Adjust your target so that it is flat=0dB at 315hz, slowly rising to +3dB at 125hz.  If you like a really solid deep bass foundation (I do) continue the rise to +5dB at 20hz.  Do a google search on "Blauert bands" and you will find some interesting stuff!

5.  You can achieve perfect channel balance at all frequencies with a correction system.  This does wonders for imaging.  L and R speakers may have the same global volume as measured by a SPL meter, but one may have a 6dB more output at some frequency than the other particularly in an asymmetric room or speaker arrangement.  This smears the soundstage.  Get perfectly symmetric output from both channels and the image snaps into focus.

6.  Understand the limits of DSP and correction.  Remember you do not boost anything -- you simulate boost by cutting back all the other frequencies.  This will limit your available dynamic range.  Say you use 12dB maximum correction.  That means at some frequencies only 6% of your amp power is available.  So try to get speakers that have good in-room response to begin with.  Minimizing the amount of correction will maximize your dynamic range and preserve bits.  This is really no different than an analog system with active EQ -- if you use +12dB boost in the bass, you will run out of headroom when your volume control is 12dB below maximum output (of course you can circumvent this in an analog setup by using a much more powerful amp on the bass).  And big room dips cannot be fixed so they must be minimized via speaker and listening chair placement. 


For those like me that have a redbook CD dominated music library, I believe the best system on the market right now is the old TacT 2150 amps.  They go for $1600 new and are respectible, if not stellar, performers out of the box.  They are better (at least when driven with a digital signal) than the SDA2175 reviewed in the digital amp shootout last year.  Sink another $2300 of upgrades into each and use with the free TACS software and you have a very powerful and capable DSP system.  Just pick up a used RCS 2.0S to carry out the measurements, and ideally a mic with a naturally flat response that will work with the TacT.  AudioControl and Earthworks are both great choices, with the AudioControl being much cheaper.  I believe the newer generation TacT & Lyngdorf products, while simpler to learn and use, are a big step backward in many other ways.

I've read a lot about the DEQX and it seems to be a worthy competitor of TacT.  It wouldn't work for me because it can only support a three way system, and I have a four way system.  For the price the Behringer gear is pretty amazing.  The future may be with PC based systems -- don't be surprised in a few years if the ultimate DSP rig is a quiet computer with a high end sound card and a large HDD for music storage!

[ka7niq]

Having been down this road -- partially with the VMPS speakers and now completely with Nolas -- here are my thoughts

1.  Main advantage of digital crossovers is that higher slopes can be used without screwing up phase response.  Drivers can work over a more comfortable and safe range and therefore can handle more power and play with lower distortion.  You can also completely eliminate high frequency ringing that otherwise cripples metal cone woofers.  I do not think the DSP crossovers are otherwise superior to well designed and implemented analog crossovers.  Now with VMPS speakers what I would suggest is blasphemy to the designer -- use steep slopes, like 36dB/octave, and change cross frequencies to 300-400hz (depending on model) and 3khz.  Personally I thought the planar driver left a lot to be desired at the upper and lower ends of its range, and sound was better when more bass was handed off to the woofer and more treble to the tweeter.

2.  Huge benefit of a digital multi-amped system with DSP crossovers is that precise time alignment and proper group delay can be achieved with all drivers wired in phase.  Now doing this takes quite a bit of work (I can go into detail if anyone wants) but I promise the results are worth it.  You will get seamless frequency response around the crossover regions with measurements, more importantly listening reveals big gains in coherency, pace and rhythm, and timbral accuracy. 

3.  Digital correction permits you to address aberrations related to your drivers and your room.  Room modes in the bass range are the easiest to fix.  Frequency response irregularities of planar magnetic panels (which I did find) and ribbon drivers can be addressed.  At higher frequencies correction is less helpful because combing, lobing, and other artefacts related to speaker design dictate the response rather than the room or intrinsic behavior of the drivers and their resonances.  With the very short wavelengths involved, small offsets from the measurement location can produce massive changes.  With the RM/X I would see 8-12dB swings at some high frequencies by moving the mic about an inch!

4.  Digital EQ allows customization of the sound to your liking.   You do this as a part of the correction process, instructing the device to correct to your target curve rather than to a flat response.  Like "warmth" ?  Adjust your target so that it is flat=0dB at 315hz, slowly rising to +3dB at 125hz.  If you like a really solid deep bass foundation (I do) continue the rise to +5dB at 20hz.  Do a google search on "Blauert bands" and you will find some interesting stuff!

5.  You can achieve perfect channel balance at all frequencies with a correction system.  This does wonders for imaging.  L and R speakers may have the same global volume as measured by a SPL meter, but one may have a 6dB more output at some frequency than the other particularly in an asymmetric room or speaker arrangement.  This smears the soundstage.  Get perfectly symmetric output from both channels and the image snaps into focus.

6.  Understand the limits of DSP and correction.  Remember you do not boost anything -- you simulate boost by cutting back all the other frequencies.  This will limit your available dynamic range.  Say you use 12dB maximum correction.  That means at some frequencies only 6% of your amp power is available.  So try to get speakers that have good in-room response to begin with.  Minimizing the amount of correction will maximize your dynamic range and preserve bits.  This is really no different than an analog system with active EQ -- if you use +12dB boost in the bass, you will run out of headroom when your volume control is 12dB below maximum output (of course you can circumvent this in an analog setup by using a much more powerful amp on the bass).  And big room dips cannot be fixed so they must be minimized via speaker and listening chair placement. 


For those like me that have a redbook CD dominated music library, I believe the best system on the market right now is the old TacT 2150 amps.  They go for $1600 new and are respectible, if not stellar, performers out of the box.  They are better (at least when driven with a digital signal) than the SDA2175 reviewed in the digital amp shootout last year.  Sink another $2300 of upgrades into each and use with the free TACS software and you have a very powerful and capable DSP system.  Just pick up a used RCS 2.0S to carry out the measurements, and ideally a mic with a naturally flat response that will work with the TacT.  AudioControl and Earthworks are both great choices, with the AudioControl being much cheaper.  I believe the newer generation TacT & Lyngdorf products, while simpler to learn and use, are a big step backward in many other ways.

I've read a lot about the DEQX and it seems to be a worthy competitor of TacT.  It wouldn't work for me because it can only support a three way system, and I have a four way system.  For the price the Behringer gear is pretty amazing.  The future may be with PC based systems -- don't be surprised in a few years if the ultimate DSP rig is a quiet computer with a high end sound card and a large HDD for music storage!

God Ed, you read my mind!
I would have no problem,or feel the least bit guilty about using higher order slopes, digital or analog.
I have OLD RM 40's w/o FST or Megawoofer upgrades.
My gut instinct tells me that they would perhaps benefit, in MY room at least, and for MY ears, from some changes.

I do not know, and haven't done the math to see how far down I can take the spiral tweeters before lobing, etc, becomes a problem.

Nor have I ever measure a Neo Panel to really see whats going on.

I prefer a fuller sound in the lower mids from 150 to 300hz ..

But I am not sure my passives are rightly tuned either!

I am not totally convinced a BIT of digital EQ in the lower range of the midrange ribbons wouldn't be better, coloration wise, then asking ANY woofer to try and supply that range of frequencys ?

That's why I want to play around with these.

Just for kicks, I hooked up an old graphic EQ, and slightly boosted the range you speak of.

The sound took on a whole new 'authority', and we watched a Movie, and it was stunning.

Like Jim Bongiorno, Peter Walker, and even Richard Vandersteen, I believe in using tone correction, IF necessary.
In fact, in a conversation with Richard Vandersteen, he told me that in his opinion, the stupidest thing ever done was to remove tone controls from high end pre amps!

I wish I still had my old SAE Parametric equalizer, I just need a touch of warmth in the range you speak of, from 125 to 325 hz.

I am HOPING that with a steep slope active crossover, I can drive the woofer hard enough to get this, w/o allowing them to play up into the midrange.
Think it might work ED ?

[woodsyi]

Having been down this road -- partially with the VMPS speakers and now completely with Nolas -- here are my thoughts

1.  Main advantage of digital crossovers is that higher slopes can be used without screwing up phase response.  Drivers can work over a more comfortable and safe range and therefore can handle more power and play with lower distortion.  You can also completely eliminate high frequency ringing that otherwise cripples metal cone woofers.  I do not think the DSP crossovers are otherwise superior to well designed and implemented analog crossovers.  Now with VMPS speakers what I would suggest is blasphemy to the designer -- use steep slopes, like 36dB/octave, and change cross frequencies to 300-400Hz (depending on model) and 3kHz.  Personally I thought the planar driver left a lot to be desired at the upper and lower ends of its range, and sound was better when more bass was handed off to the woofer and more treble to the tweeter.

I know enough about speaker building to know that what I know amounts to nothing.  I have played with the crossover between the woofers and the Neos for going on 2 years now.  This is what I found.  Eric is right and Brian is right but neither is perfect.    More bass to the woofers add meat but the voices out of the woofers are not of the same quality as that out of the Neos.  I like the 4th order lowpass on the woofers because you can drive them fuller without the non-linear upper end coming into play as is the case with 1st order filter.  On the other hand, the original passive filter with 1st or quasi 2nd order slope blends the ribbons and woofers the best which is a compromise on the lower midbass impact from the woofers and midbass tonal purity from the ribbons.  In the end, you have to choose what you like.

Addendum:  What I like changes with different types of music. 

[ka7niq]

Having been down this road -- partially with the VMPS speakers and now completely with Nolas -- here are my thoughts

1.  Main advantage of digital crossovers is that higher slopes can be used without screwing up phase response.  Drivers can work over a more comfortable and safe range and therefore can handle more power and play with lower distortion.  You can also completely eliminate high frequency ringing that otherwise cripples metal cone woofers.  I do not think the DSP crossovers are otherwise superior to well designed and implemented analog crossovers.  Now with VMPS speakers what I would suggest is blasphemy to the designer -- use steep slopes, like 36dB/octave, and change cross frequencies to 300-400Hz (depending on model) and 3kHz.  Personally I thought the planar driver left a lot to be desired at the upper and lower ends of its range, and sound was better when more bass was handed off to the woofer and more treble to the tweeter.

I know enough about speaker building to know that what I know amounts to nothing.  I have played with the crossover between the woofers and the Neos for going on 2 years now.  This is what I found.  Eric is right and Brian is right but neither are perfect.    More bass to the woofers add meat but the voices out of the woofers are not of the same quality as that out of the Neos.  I like the 4th order low pass on the woofers because you can drive them fuller without the non-linear upper end coming into play as is the case with 1st order filter.  On the other hand, the original passive filter with 1st or quasi 2nd order slope blends the ribbons and woofers the best which is a compromise on the lower midbass impact from the woofers and midbass tonal purity from the ribbons.  In the end, you have to choose what you like.

Addendum:  What I like changes with different types of music. 

Yeah, speaker voicing is a compromise that doesn't have to be.
Like Casler said, with a direct drive option, we can voice them like we want.
One thing I have noticed in 30 plus years of this hoby is no two people always hear alike.

Some audiophiles are detail and transparency freaks, some are bass mongers, some want wild and wondrous imaging, and some want to peel paint.

Me, I am into correct musical timbre first.
If it don't sound like music, I don't want it.

I remember a demo years ago of the Plasmatronic speaker at CES.
I walked by the room, and it sounded like band practice clear out into the hallway!
Dr. Alan Hill of Plasmatronics had a master tape machine playing a  recording, and it sounded spookily real!

He also had an Ivie portable spectrum analyzer on a tri pod, and I was surprised at how LITTLE information there was musically above 3 k!

Everything was happening way lower in frequency then I thought.

The range between 150 and 350 hz is critical to musical fundamentals, and that is why Brian is so dedicated to getting it right by putty and level changes ?

I wish you could enlarge the photo you provided.
Brian has been very helpful in his emails, and so have you, and everyone else.
Thank you Woodsyi!
Chris

[PLMONROE]

I have always felt that for active be-amping a really good SS for the bass and a high quality SET for the top would be ideal. One draw back of true SETs is their lower power. Those with 845 tubes can approach 40 watts (my Bel Canto is rated at 37 watts per channel) but most with other tube types are lower. 300B SETs which are among the latter sound especially sweet to me (and yeah I am aware of the 2nd order distortion aspects). With the RM-40's  neos having a sensitivity of about 91 what would be the minimum power needed from a SET to drive just the neos and FST in a moderate sized room? Anyone with any experience or thoughts on this?