[Xi-Trum]

Hi Curt, can you comment on the sonic difference between the LLC Purist and the Audiophile?  What are we giving up with the built-in 2-way filter in the Audiophile?  Also, can you comment on the sound with and without using the gain control?  Thanks.

[Marbles]

and um, ah, how are the XO's coming

[Xi-Trum]

Also, I'm guessing that the LLC-Audiophile sounds better than the LLC-Purist + external XO?

Oh yeah, when are we expecting the LLC-P or A to be available?  

[OkRon]

I guess if the Purist and Audiphile are behing schedule the Sabai is not going to make the estimated February release?

[Curt]

opps... wrong answer  

[Brad]

Kind of a cryptic remark, Curt  

Any clarifications for us?
How many have shipped?

[Curt]

Funny, I wrote a long answer to the wrong question before. I have been working on the website all day and forgot to come back to finish this.

Guess I get involved in my work and all else fades away

First lets talk standard systems:

The LLC-P "Purist" has to have the edge, less electronics = better.

The LLC-A "Audiophile" has to give something up to the extra AXO circuit and therefore must pass the trophy (for best signal feed to the amps) to the LLC-P.

Now, both circuits are very similiar so the difference maybe so small it can not be heard and only measured. This is probably a good guess.

Now removing the passive XO and using the LLC-A active:

The LLC-A has an AXO and and when the bi-amps are connected directly to the drivers (passive XOs removed) that is a much, much greater difference than the LLC-P vs. LLC-A standard system test.

Active mode bi-amping the drivers is where most people will listen and say WOW why didn't I do this before.

Don't think it's always this simple though, you do have to match components and play around with speakers just like another high-end system to get the best results.

When you get it right you really can have a great sounding system.

Now let me re-use some of my earlier post  

<snip>
IMO the LLC-P Purist competes with preamps $2K and up, up to any price. I think many will be quite surprised by this product. IRD is known now only for our entry level MB-100 monoblocks but, we are building a product line that includes some very high-end pieces as you shall soon see.

The LLC-P is as close to a straight wire with gain that we have ever heard.

The new E1 Series products were more than a year in R&D and we have also spent many, many dollars to get them right.

I have been working on the IRD website since Thursday and will try to get it up early this coming week. I wanted it up by Monday but, there have been changes that are taking some time.

It has been difficult to answer all the e-mail and stay on top of things and we feel that by keeping the website more up to date we can cut back the e-mails a notch or two. I am trying to answer standard questions and post standard information online for all to read at their leisure.

BTW : The first USA LLC-Ps are shipping Monday and they will continue to be in production, and ship every couple days, from our factory until we finish the first LLC-P run. We will then move to the next E1 Series product. This is all I can safely say at this time.

Thank you all for your extreme patience and interest in these new audio components.
<end snip>

That about says it all for now.

[Curt]

RE: Gain Question

I run the LLCs at 6dB gain, the minimum setting, unless more gain is required. The most common gain used in preamps is 6dB. I could not measure any differences between 0dB and 6dB so made 6dB the standard LLC gain to keep extra components out of the signal path.

Most systems and recordings do benefit from the 6dB (X2) signal boost.

9.5dB and 12dB are available from a front panel selector switch if required. Some older sources and possibly phono preamps may benefit from the "extra" available gain.

6dB pushes MB-100s to the max with a CDP. A realistic listening level for most of our good CDs is position 10-14 of the 24 position switch. Some CDs and lower efficiency loudspeakers need to go as far as position 16 or so confirming the 6dB boost a requirement.

How do they sound?

Well there is really no difference in the actual sound and the only difference seems to be in the added noise. As the gain increases the noise is amplified also. I see the noise floor change in our test equipment. Nothing to worry about but it’s a small change for the worse.

How much difference in the noise?

First let me start by saying that the measured noise floor with a 1k Hz tone at 80% Full power was about –135dB on the SpectraLAB spectrum analyzer. I have never seen a noise floor this low. With a THD+N of 0.00083%, this is with both channels driven. In normal terms this says this is a very, very quiet device.

Now, there is a position on the source selector switch called “Mute” this is where you can leave the switch if you leave your system on all the time or if you need to go somewhere and will be coming back to listen more.

This position really was designed for system noise level testing. It uses all the same input traces and relays that a standard source would go through except where the RCA connectors would go for the source input I put a direct short. The mute position is exactly like putting RCA connectors that are shorted into the LLCs input jacks. What you hear at the speakers is the internal noise from the LLC and the added internal noise of the amps and any noise generated in the cables or loudspeakers. Quite nice for a quick system test at the flip of a switch.

Back to the difference in gain noise… in the mute position you can still turn the gain up and the volume control up. I set the gain at 6 dB and the VC at max, this is well over anything you would encounter listening to music which would never be “all the way up”.

Now putting an ear to drivers nothing can be heard (by myself and several others) and, turning the gain up to 9.5 dB still nothing, then up again to 12 dB and a few people think they might be starting to hear something but they are not sure.

These tests were done using 93dB 1W/1m nOrh 6.6 Prism loudspeakers, our most efficient test speaker. I would like to get a physician’s stethoscope for doing tests like this.

So, noise is not much different and low enough that it seems we can over look it if the 12 dB gain is ever needed. Still we recommend using the 6 dB setting unless the extra gain is really needed. The lower gain does measure better.

Please tell me were not nuts getting in this deep! Sometimes I wonder...

3am, night all. I’ll check this thread in the morning.

[Xi-Trum]

Thank you very much, Curt.  I'm looking to bi-amp the nOrh 9.0 using 4 MB-100.  It looks like the LLC-A is the way to go.  Now, the remaining question is the XO frequency to go with.  Is it a big deal to change XO frequency?

Thanks again.

[Curt]

Now, the remaining question is the XO frequency to go with.  Is it a big deal to change XO frequency?

Sounds like a good plan. The 9s should bi-amp very well.

I think a good choice fo XO is some where between 2500-2800 Hz acording to my calculations but, Michael Barnes of nOrh would be the correct one to ask.

XO points are easily changed with inexpensive plug in modules.

You will probably be changing the XO point every time you make a loudspeaker change. Modules make this very practical.

[OBF]

Curt,

I was wondering something about proper use of active biamping.  Have you found it to always or at least usually offer an improvement, or does it depend on the speaker system?  The reason I ask is I was just reading about the Northcreek Rythm DIY speakers and they have a detailed description of the crossover design.  I think the Rythm Unlimited uses an approx $1k passive external crossover that they put a lot of effort into taming the Scan Speak Revelator tweeter and optimizing frequency response, power response, on and off axis performance, phase, etc..... I don't know enough to really understand the nuances of crossover design, but it made me wonder if you can just swap an active crossover into a system like that and get the expected results?  Or do you have to pick your poison so-to-speak and look at speakers with superior drivers and inferior crossovers?

[nathanm]

Curt:  Can you give any details about the crossover modules; what they look like, what's involved with installing them, price etc.?  Is there are reason they are separate 'things' as opposed to say a knob that adjusts the XO point?  Just curious.

[Curt]

Curt:  Can you give any details about the crossover modules; what they look like, what's involved with installing them, price etc.?  Is there are reason they are separate 'things' as opposed to say a knob that adjusts the XO point?  Just curious.

The frequency modules are small and simply plug-in. They cost about $10 each.

The reason they are separate things is because we match the channels and we like exact values. We use all precision hand matched components.

We offer standard frequencies (shown on our website) but, also can make any fc you may require.

There are so many frequencies to choose from it's impractical to use an adjustment switch unless it is an infinitely variable control then we would have the same issues that pots vs. step attenuators for volume controls have.

The filter topology we use works best with fixed frequency modules and all outputs are “truly” kept in phase.

IMO adjustable active filters, not channel matched are just not good enough for IRDs high standards.

Our modules may be a little harder to set up but our AXO performance is worth it.

[Curt]

Curt,

I was wondering something about proper use of active biamping.  Have you found it to always or at least usually offer an improvement, or does it depend on the speaker system?

This is a big and hot subject. Here are my most basic thoughts about passive vs. active XOs.

All passive crossovers suffer bad phase shift problems, loose control of the signal at the fc knee, can smear the signal, they suffer from a substantial signal loss (as much as 2-3dB SPL @ speaker in some cases), the filter cutoff frequencies can vary (this one is really not nice) as the load impedance changes (with frequency like we all know it does) and it is very difficult to get both channels closely matched due to the component tolerances available.

A passive crossover is difficult, to say the least, to design correctly. Most companies don't get them as good as possible. When it is designed correctly it still has most of the problems that come with all passive filter designs.

BTW : If a passive crossover costs $1,000 someone is making a lot of money and like I said you will still have most of the problems that come with passive crossovers, it's the nature of the beast.

The place to correctly separate the frequencies is at line level, in an active circuit that is simply much more accurate and much more controllable. Separate amplifiers for separate frequencies works great and requires less power.

Using an active crossover and bi(tri)-amping the drivers 95% of the time (IMO) will make a very noticeable improvement. You need to pick the correct crossover point, match the driver SPL levels and hope the speaker box has no resonance problems that was being fixed with gobbed-on extra fixit circuits (not too common due to the extra costs) in the original passive XO.

A note about high-end well designed loudspeakers:

There are many very good loudspeaker companies in the world.

These companies spend a lot of time voicing there loudspeakers. Yes, they test many XO circuits and components until they get just the sound they want.

These are special and normally more expensive loudspeakers, usually very expensive.

My rule of thumb is if the loudspeakers have unusual drivers, ribbons, built-in adjustments, unusual shaped cabinets, and/or cost over $4,000 per pair give it some extra thought. You may not want to go active with these well designed and well voiced loudspeakers.

But, you can always test them by connecting a few wires, leaving the passive in place, then if there is no improvement it is quite easy to go back.

Bottom line is that with most of the loudspeakers out there today there will be an very noticeable improvement heard going active. Probably most noticeable with loudspeakers < 4$K per pair.

[MaxCast]

I sure would be nice to see these crossovers in action at the Midwest Audiofest    
A pair of speakers with a passive and a pair active

[OBF]

Curt,

Thanks for the crossover explanation.  That helps.  I don't know why the Northcreek crossover I referenced costs so much, but it does sound pretty complex, from their site:

"The Rhythm Revelator Signature Project features 8-gauge inductors, fully cascade-bypassed Crescendo and NOS Military capacitors in both the woofer and tweeter sections, crossover components hand selected and matched to ±0.25%, drivers broken in "perfect pairs" (hand matched to ±0.5dB), supplied for bi-wiring."

"Initially, we begin with an impedance-compensated, overdamped forth order topology, including damping resistors in series with all shunt capacitors and the first inductor being about twice that expected from formulae. While this is extremely complex, it provides a suitable starting point. With five optimizable reactive components plus what amounts to three optimizable damping resistors in the woofer circuit, and six optimizable components in the tweeter circuit, a filter with the correct electrical characteristics may be quickly obtained."

"Analysis of the sum, power, and anti-phase curves of early simulations with a 3kHz target crossover frequency, revealed that even with reasonably flat frequency response, both the power and antiphase curves were asymmetric. We then began to massage the acoustic crossover frequency while adjusting for relative driver offset, and eventually developed several physically realizable possibilities of varying complexity that were worth popping together in the listening lab."

........I suspect that may be one speaker to not mess with but I don't own them, just curious  Wouldn't a good active crossover make DIY 2 way speaker building a lot easier?

[MaxCast]

 Wouldn't a good active crossover make DIY 2 way speaker building a lot easier?

That's what I was thinking.  Finding a pair of drivers which have friendly impedence and FR curves and placing them in a box for biamping.