K2 M9500 purchase

[boputnam]

You and I have a secret "remember?"

Hell, dood, I exposed that some-time back!

Full Disclosure - see post numero Veinte y Cinco

[Ken Pachkowsky]

Ken and Bo? I never would have guessed... and you both have such nice wives too.

Widget

Hmmm... I set myself up for that one!

Ken

[Ken Pachkowsky]

Hell, dood, I exposed that some-time back!

Full Disclosure - see post numero Veinte y Cinco

Hmmmm... Wrong Secret!

= Bo wondering what secret Ken is talking about. By the way, ya have me wanting that damned pre-amp now. Damn you Putnam!

Ken

[boputnam]

By the way, ya have me wanting that damned pre-amp now. Damn you Putnam!

Ha! Me too!!
One here, another on the way...

[Earl K]

Hi Dennis

Should be a fun weekend. I am planning on trying the biamp approach as well.

- Are you thinking of "biamping", this weekend or was that mentioned as future tense ? It would be nice to hear all about your biamping impressions .

- Also, at some future point it would be great to see an RTA "screen capture", done on axis to the horn center , with fullrange pink noise fed into only the two woofers - ie fullrange pinknoise into the woofers , with the internal crossover bypassed .

- That RTA readout would greatly increase the local MTM knowledge base around here. For example ; it would be incredibly instructive to see what sort of midband "rise" a pair of 1400nd woofs possess ( 100 hz to a 1000hz ) within your MTM setup. This "rise" seems to be dealt with passively, by the M9500 lowpass. Since the M9500 filter settings are known - some extrapolated knowledge might be usefully applied to the redesign of the lowpass circuits in the Project May MTM .

regards <. Earl K

[dennis j leisz]

Hi Earl and All,This weekend I intend to begin experimenting with some basic testing. A friend is coming over on Saturday with various test and measurement instruments to assist. So far I have only tried single wire and bi wire setups. Last evening we listened for about a half hour to music we were very familiar with. I then changed out the wire on one speaker for an A/B test. I used Audio Research Litzlink for the subs and Nordost Red Dawn on the hi freq. driver; A biwire setup. There was an audible difference in hi freq. clarity low end punch with better definition. We're not talking quantum leaps here, But enough of a difference that I would keep it hooked up this way. My friends at Audio Research are making Bi wire cables for me and I will pick them up tommorrow . I will try a tri wire setup . I do not have a crossover yet for biamping. Any suggestions? I have a new pair of McIntosh MC275s' I am anxious to use in biamp mode. My digital camera is being returned by junior so photos will shortly follow. As time permits I will provide any technical data I'm capable of. Someone inquired earlier as too which preamp I'm using. I'm playing around with three; Audio Research Ref2 mkII, McIntosh C2200 and a McIntosh MX135 pre/processor. I'm having some fun once again.Regards, Dennis

[Mr. Widget]

I do not have a crossover yet for biamping. Any suggestions?

First choice would be the PassXVR-1 http://www.passlabs.com/preamps/xvr1.htm

Second choice would be from Marchand http://www.marchandelec.com/

I recently heard the DEQX, and while I have not been an advocate of digital, this unit is amazing. It is a three way crossover (or two way), preamp, room correction, and speaker correction. Yes, even the M9500 could be corrected a bit.

http://www.deqx.com/dsp-product/PDC26P-Preamp.html

Keep the reviews coming!

Widget

[Earl K]

Hi Dennis

I do not have a crossover yet for biamping. Any suggestions?

Well, Giskard has posted the necessary RC values for the M9500 "personality card" in the quite workable DX1 ( which is hard to obtain ) - you could look around for one of them. The given RC values will set the "poles" to the designed frequencies .

I would't rush into the purchase of any electronic crossover for a K2 product. I doubt if a typical crossover, having only a single crossover area ( point ) will suffice in your K2 case.

As an example; a typical design "trick", found in the lowpass area, of most K2 stuff, is the implementation of multiple slopes/curves, all executed through quite "creative" pole-spreads ( your low-pass is a 3 pole type ).This is done to essentially "flatten the LF response" before actually implementing the crossover point. I did a low-pass "points" workup from the LC values posted in a M9500 schematic - the results are quite intriguing . Into a 3.6 ohm load ( and if my math/calculator is right ) , the lowpass portion of the M9500 has turnover points set at approx; 136 hz, 790hz and 950 hz ( all for a 650hz lowpass ??? ). Take these frequencies with a grain of salt - since I don't know the actual operating (AC ) impedance of the woofer circuit . The point is to notice the abnormal "pole-spread" .
These ( quite baffling) results are the reason I suggested you run pink noie through the woofers ( bypassing the lowpass ), to begin to get a handle on what passive EQ is actually being applied inside your M9500 network. An RTA curve will give some indication of the "true" response of those woofers and provide a benchmark, to proceed from . "Before & After" comparisons would tell some of the story .

Marchand, do make some crossovers that would allow for the necessary ( creative ) pole spreading.

regards < Earl K

PS , Oh I forgot to mention that the HiPass portion of your network is 2-Pole ( or approx. 12db per octave ). So, when researching specs. on various electronic crossovers for your M9500 - I would make sure any prospective crossover has the capabilities to execute all of these multiple pole ( spreading & number ) capabilities/tasks . Again, Marchand comes to mind .

[Tom Loizeaux]

Earl,
What a great post! I love this forum.

I wonder why JBL hasn't come out with a crossover/ crossover set-up to optimize these K2s? Back in the '70s and '80s JBL made up crossover cards for use in their 5235 crossovers that were optimized for each of their high end studio monitors. If I had worked as an engineer on these, I would certainly have wanted to give the ability to correctly bi-amp these to the K2 customers... (and sell more JBL gear in the process).

Tom

[Don McRitchie]

They did with the DX-1 and specific "personality" cards for the different K2 systems. Search this forum for that term and you should find lots of background. Unfortunately, demand was very low so that they are no longer in production and are exceedingly rare.

[4313B]

Unfortunately, demand was very low so that they are no longer in production and are exceedingly rare.

Yeah, I guess the people who think biamping is hogwash outnumber the people who don't.

Fortunately a person can build their own DX-1 with a bit of effort. Like Earl says though - just send the card information to Marchand and have them build it. The low pass is active and the high pass is passive. Marchand should be able to take the card information and construct the proper voltage drives. The main benefit in biamping the M9500 is that the 1400Nd "doesn't like inductors".

[Don McRitchie]

The following question is asked out of ignorance on my part. I infer that the multi pole approach is a means of effecting EQ in the driver response. If so, why not just apply EQ directly since most electronic cross-overs have his feature? Is it an issue of analog vs digital? I know the feature rich electronic cross-overs are digital due to the ease of implementing signal processing in the digital domain. Is this multi pole approach just a means of doing something similar in the analog domain?

Don

[Earl K]

I infer that the multi pole approach is a means of effecting EQ in the driver response.

- Yes, your understanding ( or some of it ) is correct. It's implementation is somewhat akin to using the broad tonal shapings of the bass and treble sections , as found on a hifi preamp.

- The "poles" in question are already present within any passive crossover. A "pole" is just another name for a passive "element or component". A 6 db crossover has a single "pole" or "component/element".

- If the desired filter is a "lowpass", then the single component ( pole ) is an inductor (L). A 12 db crossover has 2 connected LC components/elements ( or poles ) . An 18 db/octave crossover has 3 poles ( LCL elements ). etc. ("C" is the capacitor )

- These poles must be present to create the desired crossover slope. The creative circuit designer can ( and obviously sometimes does ), use these existing poles to create a bit of broad-band "EQ shaping" before the filter forms the circuit into its final slope/shape , down into the "Stop-Band" .

- Moving the poles about - in relation to each other while trying to maintain a 3 db down point at the chosen point, is definately an art. Move them too close together and they form a resonant circuit / move them far apart and they'll filter independant of each other .

- Once the passive crossover isn't there - then any compensatory (speaker ) EQ needs will have to come from somewhere. At this point, "somewhere" becomes the electronic crossover if it has this capability .

If so, why not just apply EQ directly since most electronic cross-overs have this feature?

- Actually, most electronic cross-overs don't have this type of EQ easily accessible .

Is it an issue of analog vs digital?

No, not really, its more an issue of the basic filter topolgies as implemented in the available, commercial products. Most electronic crossovers just don't have the ability to "cascade" the EQ sections to give these sorts of asymmetrical slopes. Only certain (rare) types of crossovers ( usually using "Sallen-Key" based topolgies ) are setup to afford this flexibility. Typically, crossovers that set the crossover point through plugin cards, might offer this capability of implementing these asymmetrical-slopes ( for example; the PassXVR-1/IanMacs DIY, JBL 5235 , DX-1, Marchands ). Analog crossovers whose filters are contructed via the "State-Variable" circuit topolgy, cannot very easily offer this flexibilty ( for example - newer Ashly(s) use State-Variable filters ) .

I know the feature rich electronic cross-overs are digital due to the ease of implementing signal processing in the digital domain. Is this multi pole approach just a means of doing something similar in the analog domain?

Many DSP based crossovers are just as handcuffed in the actual implementation of their powerfull features . Why ? The DSP "programmer" builds up a concept ( or Macro/Interface ) that is based on an emulation of some analog model. If he/she copies a limited "model" then that is the straight-jacket the user must live with ( DBXs' - DriveRack comes to mind ).

- Since cascading single pole sections is a pretty rare event in the line-level analog world - you can bet that this rarity has been emulated in a large percentage of available DSP devices .

- So, IME, for the casual user, its very hard to shop for a DSP based device. All the glizt and glamour of the "Product Pull-Sheets" usually mask some interface deficiency the user won't discover until its' too late . It's best to download the units manual in pdf form ( if available ) and then study it religiously - and then ask lots of questions before buying .


Does this make any sense ? If not, I'll try and rewrite it to be more succinct .

regards <> Earl K

[dennis j leisz]

The first shots of the M9500s' in place .Dennis

[Ken Pachkowsky]

Dennis

Where do you park the forklift for moving the rack around?

PS: Damned nice!

Ken