Need Help with Dr. K's MTM RS 180/RS28

[bobraus]

I purchased a pair of RS 180's and RS 28's and ran that configuration in a two way and found great promise with performance of both drivers. I was able to obtain a level of detailing/transparency/musical realism and dynamic realism that was truly impressive. Late night listening was a bit reminiscent of low level listening sessions years ago on a pair of original Quad electrostats I once owned.

I decided to build Darrens MTM version with two RS 180's and matching RS tweeter. I strictly followed crossover component design and values and baffle width instructions. My construction of the DR. K's is correct. I wanted to use these speakers on a secondary home theater system. I have several "Commercial Reference" speakers in house and have a good selection of hi-end electronics etc. I think I have a pretty good handle on what respectable playback should sound like and that is the problem.

My Dr.K MTM's after more than two weeks play lack the "magic" I heard in my inital 2 way RS180/RS28. The ability to see into the music and follow minute inner detail is reduced. While the drivers retain some of the overall character found in the 2 way design the basic sound is un-involving. Cymbal crashes and high frequency instruments sound slightly muted and the ability to precisely locate instruments and see into the soundstage are lacking- the sound stage is difuse- (I know the drivers are capable of executing these things). Drums and percussion also lack snap and intonation/pitch- they sound a bit muted and overall dynamics are uninvolving. The sound is vieled and sounds as though a layer of gauze has been impossed upon the overal musical presentation. The word opaque characterizes the basic sound I now hear from these first class drivers.

Q??? The speakers are used in a modest sized room so I do not have the luxury of placing the cabinets 3 or 4 feet out in the room. The speakers are at most 6 to 12" from the rear wall. I suspect the baffel step built into the crossover may be playing havoc with the performance of this speaker. I have inserted an equalizer into a tape loop and found that by inverting the baffle step compensation that the speakers begin to take on some of the virtues I originally found with my first encounter with these drivers. Transparency, bass pitch, detail and image placement all improved with the equalizer. I am a bit of an audio purist and would prefer not to use the eqaulizer (which has very limited band selection to begin with).

Q?Is there any way to reduce the baffle step amount designed into the Dr. K's? I realize that the efficiency of the tweeter may not allow for complete removal of baffle step- but is it possible to operate the Dr. K's with only 2 or 3 db of baffle step? I really like the promise of the Dr. K design. Can anyone help me? Is there any RS180/Rs28 MTM design available without baffle step? In my present room set up I am limited in speaker placement. Any feedback would be greatly appreciated.

[thomasw]

Provided Link: JonMarsh Modula MTM


Others have said same. Take a look at the design in the link. It's very good. The XO is more complicated than those in the Dr.K

[thomasw]

[bobraus]

Dear Tom, Thank you for your suggestion. I a aware of the Modula design. Jon's latest revision gives it a full 6 db of baffle step. A previous Modula version was only 5 db. These drivers offer too high a level of performance to endure the medicority I hear with the Dr. K's MTM. I have an electronic crossover 24 db LR that I may be forced to turn to. I had hoped to keep the RS 180/RS 28 mtm simple and singularly amplified. From the moment I fired this system up the speakers sounded lacking in refinement- high frequencies seemed truncated- percussion instruments and voices just did not float nor did the highs have extension/air (I know the tweeter is not the airiest- I have Fountek Ribbons and electrostats in house as well as one one behemouth Infinity Planar/Ribbon speaker with 72 tweeters). I like the resolving power and dynamic palette offered by the RS tweeter- it is truly first rate- but not as employed in my Dr. K's placed near a wall surface. I see incredible potential in the PE Reference drivers but remain frustrated over the level of performance the DR. K's have in my room with limited placement options. I also enjoy near field listening. The Modula would seem to one up the Dr. K's using a lower crossover point. My inital 2 way with the RS 180/RS28 was electronically crossed-over at 1425 hz. and offered superb resolution and integration.

Others have said same. Take a look at the
> design in the link. It's very good. The XO
> is more complicated than those in the Dr.K

[Jim Holtz]

Have you tried them away from the walls to verify that BSC is in fact the issue? Most designers use around 4 DB BSC as a starting point. I would think that to much BSC with a close wall placement might create a bloat in upper bass with some chestyness in male vocals but not all of the issues you speak of.

Perhaps, you prefer a different voicing than Darren?

Jim

> Dear Tom, Thank you for your suggestion. I a
> aware of the Modula design. Jon's latest
> revision gives it a full 6 db of baffle
> step. A previous Modula version was only 5
> db. These drivers offer too high a level of
> performance to endure the medicority I hear
> with the Dr. K's MTM. I have an electronic
> crossover 24 db LR that I may be forced to
> turn to. I had hoped to keep the RS 180/RS
> 28 mtm simple and singularly amplified. From
> the moment I fired this system up the
> speakers sounded lacking in refinement- high
> frequencies seemed truncated- percussion
> instruments and voices just did not float
> nor did the highs have extension/air (I know
> the tweeter is not the airiest- I have
> Fountek Ribbons and electrostats in house as
> well as one one behemouth Infinity
> Planar/Ribbon speaker with 72 tweeters). I
> like the resolving power and dynamic palette
> offered by the RS tweeter- it is truly first
> rate- but not as employed in my Dr. K's
> placed near a wall surface. I see incredible
> potential in the PE Reference drivers but
> remain frustrated over the level of
> performance the DR. K's have in my room with
> limited placement options. I also enjoy near
> field listening. The Modula would seem to
> one up the Dr. K's using a lower crossover
> point. My inital 2 way with the RS 180/RS28
> was electronically crossed-over at 1425 hz.
> and offered superb resolution and
> integration.

> Others have said same. Take a look at the

[bobraus]

Dear Jim,
I respect Darrens abilities which far exceed anything I will probably be able to approach with my design attempts. His design work on the RS series is impeccable. I have just had major open heart surgery and cannot lift more thabn 5lbs for the next 6 weeks. I cannot move my Dr. K's into another room until that time. My use of an equalizer to drop the baffle step boost in the 400 to 1000 hz range by about 4 db seems to have a major effect at opening the sound up. The high frequencies seem more open, instruments seem to begin to float again on good recordings and image focus also seems improved. I am amazed at how much the mid bass and lower mid range influence the tonal balance of various speakers. Even crazier- I am amazed at how the proper placement and level matching of sub-woofer and midrange tweeter panels brings about a more natural musical balance to the sound of tweeters. My musical preference is not for overly etched and emasculated bass foundations. I do value articulation and the ability to peer into the musical scoring. One of my hobbies is playing bass in a blues band- I appreciate accurate bass reproduction. Standing next to a drum set playing live- I think I have a good handle on what a live drum set sounds like and how far most speakers are from even approaching the sound and dynmaics I hear playing out. I know the RS 180's are capable of more articulation and snap than what I am presently hearing. I think the wall placement is just strangeling the sound of my Dr. K's. With almost universal acclaim for Darren's design I am simply hoping that a minor baffle step revision might allow my speakers to yield a higher level of performance in my near wall placement. I know speakers sound better typically away from walls- in this small system I simply do not have that option. Thanks for your feedback.

Have you tried them away from the walls to
> verify that BSC is in fact the issue? Most
> designers use around 4 DB BSC as a starting
> point. I would think that to much BSC with a
> close wall placement might create a bloat in
> upper bass with some chestyness in male
> vocals but not all of the issues you speak
> of.

> Perhaps, you prefer a different voicing than
> Darren?

> Jim

[thomasw]

We think along siimilar lines.

Each of my mains consists of a pair of Acoustat 1+1's separated by a R&G RD75, and a line array of 16 Technics 400D leaf tweeters. These are quad-amped with a 12 driver IB sub... ;^)

[Jim Holtz]

Hi Bob,

I hope you didn't think I was questioning your ears or wisdom, I was not. Speakers are very objective in the design and construction phase but become totally subjective in the voicing and listening portion. Different strokes for different folks so to speak. Personally I'm an analytical listener and want as close as the speakers are capable of, to producing the original performance. I don’t subscribe to the audiophile group that wants to hear what sounds pleasing to them at a particular moment in time. I want real! :-)

I haven’t heard Darren’s version of the MTM’s and am currently building Jon’s Natalie P. crossover version of this speaker for my Daughter. I should have them at the Chicago DIY event in a couple weeks if everything goes right. I have heard Darren’s work before and it was very good but everyone has different goals when they create a speaker design. I wanted a higher crossover point which is why I chose the Natalie P. variation. These speakers will get cranked up and I felt the 1.8K crossover might handle it better than the lower ones used in the Dr. K. and Modula designs.

I hope you recover quickly. I’ve enjoyed red meat for many years and am not looking forward to the day that it catches up with me.

Best regards,

Jim

> Dear Jim,
> I respect Darrens abilities which far exceed
> anything I will probably be able to approach
> with my design attempts. His design work on
> the RS series is impeccable. I have just had
> major open heart surgery and cannot lift
> more thabn 5lbs for the next 6 weeks. I
> cannot move my Dr. K's into another room
> until that time. My use of an equalizer to
> drop the baffle step boost in the 400 to
> 1000 hz range by about 4 db seems to have a
> major effect at opening the sound up. The
> high frequencies seem more open, instruments
> seem to begin to float again on good
> recordings and image focus also seems
> improved. I am amazed at how much the mid
> bass and lower mid range influence the tonal
> balance of various speakers. Even crazier- I
> am amazed at how the proper placement and
> level matching of sub-woofer and midrange
> tweeter panels brings about a more natural
> musical balance to the sound of tweeters. My
> musical preference is not for overly etched
> and emasculated bass foundations. I do value
> articulation and the ability to peer into
> the musical scoring. One of my hobbies is
> playing bass in a blues band- I appreciate
> accurate bass reproduction. Standing next to
> a drum set playing live- I think I have a
> good handle on what a live drum set sounds
> like and how far most speakers are from even
> approaching the sound and dynmaics I hear
> playing out. I know the RS 180's are capable
> of more articulation and snap than what I am
> presently hearing. I think the wall
> placement is just strangeling the sound of
> my Dr. K's. With almost universal acclaim
> for Darren's design I am simply hoping that
> a minor baffle step revision might allow my
> speakers to yield a higher level of
> performance in my near wall placement. I
> know speakers sound better typically away
> from walls- in this small system I simply do
> not have that option. Thanks for your
> feedback.

> Have you tried them away from the walls to

[bobraus]

Dear Jim, I prefer analytical/ real voicing and find it much preferable to euphonic. I would rather hear the recording warts and all. A truly high resolving speaker still draws me in to even less than stellar recordings. Thank you for your well wishes- the strange thing after open heart surgery- for the first few weeks- there are no dietary restrictions- they just want you to conusme protien to promote healing. I have the parts in house to construct the Natalie P crossover. Perhaps it is a matter of voicing preference. I would hate to abandon these drivers when they offer such promise for such a modest investment. I am an RS driver advocate and just helped a friend put together before I had my emergency surgery a 6- 10 RS hi-fi sub system that is performing well in his hi-end system.
Hi Bob,

> I hope you didn't think I was questioning
> your ears or wisdom, I was not. Speakers are
> very objective in the design and
> construction phase but become totally
> subjective in the voicing and listening
> portion. Different strokes for different
> folks so to speak. Personally I'm an
> analytical listener and want as close as the
> speakers are capable of, to producing the
> original performance. I don’t subscribe to
> the audiophile group that wants to hear what
> sounds pleasing to them at a particular
> moment in time. I want real! :-)

> I haven’t heard Darren’s version of the
> MTM’s and am currently building Jon’s
> Natalie P. crossover version of this speaker
> for my Daughter. I should have them at the
> Chicago DIY event in a couple weeks if
> everything goes right. I have heard Darren’s
> work before and it was very good but
> everyone has different goals when they
> create a speaker design. I wanted a higher
> crossover point which is why I chose the
> Natalie P. variation. These speakers will
> get cranked up and I felt the 1.8K crossover
> might handle it better than the lower ones
> used in the Dr. K. and Modula designs.

> I hope you recover quickly. I’ve enjoyed red
> meat for many years and am not looking
> forward to the day that it catches up with
> me.

> Best regards,

> Jim

[Paul K.]

Darren told me he built in 4-4.5 dB of BSC for his Dr. K's, so it appears your removal of it via your equalizer indicates that's what you need to do to allow the speakers to really sing. I, too, have to place my speakers near the walls, probably in a "worse" scenario than you, so no BSC for me, either. I hope your recovery process is good and short.
Paul K.

> Dear Jim,
> I respect Darrens abilities which far exceed
> anything I will probably be able to approach
> with my design attempts. His design work on
> the RS series is impeccable. I have just had
> major open heart surgery and cannot lift
> more thabn 5lbs for the next 6 weeks. I
> cannot move my Dr. K's into another room
> until that time. My use of an equalizer to
> drop the baffle step boost in the 400 to
> 1000 hz range by about 4 db seems to have a
> major effect at opening the sound up. The
> high frequencies seem more open, instruments
> seem to begin to float again on good
> recordings and image focus also seems
> improved. I am amazed at how much the mid
> bass and lower mid range influence the tonal
> balance of various speakers. Even crazier- I
> am amazed at how the proper placement and
> level matching of sub-woofer and midrange
> tweeter panels brings about a more natural
> musical balance to the sound of tweeters. My
> musical preference is not for overly etched
> and emasculated bass foundations. I do value
> articulation and the ability to peer into
> the musical scoring. One of my hobbies is
> playing bass in a blues band- I appreciate
> accurate bass reproduction. Standing next to
> a drum set playing live- I think I have a
> good handle on what a live drum set sounds
> like and how far most speakers are from even
> approaching the sound and dynmaics I hear
> playing out. I know the RS 180's are capable
> of more articulation and snap than what I am
> presently hearing. I think the wall
> placement is just strangeling the sound of
> my Dr. K's. With almost universal acclaim
> for Darren's design I am simply hoping that
> a minor baffle step revision might allow my
> speakers to yield a higher level of
> performance in my near wall placement. I
> know speakers sound better typically away
> from walls- in this small system I simply do
> not have that option. Thanks for your
> feedback.

> Have you tried them away from the walls to