Speaker Asylum: REVIEW: Green Mountain Audio Continuum C1.5i Speakers by Bombaywalla

Model:	Continuum C1.5i
Category:	Speakers
Suggested Retail Price:	$4995
Description:	3-way minimum baffle, time-coherent, minimum phase floor standing speakers
Manufacturer URL:	Green Mountain Audio
Manufacturer URL:	Green Mountain Audio

Review by Bombaywalla ( A ) on December 08, 2003 at 11:50:12
IP Address: 63.166.216.16

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for the Continuum C1.5i

Review of the Green Mountain Audio Continuum 1.5i speakers(Long!!)
I have owned these speakers since July this year. The previous owner had these speakers made this February (Roy informs me that he made them personally) but he could not get them to work in his setup/room (my thanks to him for putting these speakers up for sale!). When I bought them, they had maybe 50 hrs on them & I have added another 100 hrs. (having little children in the house restricts the time I can spend on listening).
Synopsis:
I am very pleased indeed with these speakers & cannot say enough good things about them. They have, so far, lived up to the expectations that I had personally set for my next pair. Details in the review.
Speaker Position in Room:
I am fortunate to have a “coffered” ceiling in my listening room. Final position of the speakers is 50.5” from the side wall (distance measured to side of woofer cabinet closest to wall & *not* to center of woofer driver) & 60.5” from wall behind speaker to the *front* baffle. Toe-in is slightly less than Roy’s recommendation: the midrange fires slightly beyond the shoulders. In my particular case the speakers are 9’ apart & my listening chair is also 9’ away on the perpendicular, which is the equal-legged T Roy talks about in the user’s manual.
Specifications as in User’s Manual:
The numbers in the user’s manual & on the website are not in total agreement (I don’t know why) but I’ll tell you what the user manual states:
Drivers: 10” woofer, 4.5” mid, 28mm tweeter
Type: Sealed box design with minimum baffle (to minimize reflections)
Response: less than +/- 1.5dB across spectrum @ listening position
-3dB at 38Hz & 23KHz in med. room
-3dB at 42Hz & 23KHz in large room
Horizontal Dispersion: > 120 degrees through 7KHz (-3dB)
Dist: < 0.3% THD & IMD at 80Hz @ 95dB SPL
< 0.5% below 80Hz
Rise/Fall Time: < 0.015mS each
Phase Shift: +10 degrees @ 150Hz
-10 degrees @ 8KHz
+/- 1 degree 250Hz – 6KHz
Sens: 89dB/1m/1W
Matching : +/- 0.25dB 140Hz – 10KHz
Impedance: 8 Ohms
Dynamic Range: > 110dB/pair @ 2m
Woofer compression: 105dB SPL
Xover Type: single-element, 1st order (6dB/oct) parallel Butterworth electrical & acoustical
Xover Freq: 350Hz & 3KHz
Polarity: Non-inverting
Power Requirements: 12-250W. Peaks to be held < 130W
Weight: approx. 70lbs/unit
Dim: 46.75”H, 12.375” W, 14.375” D
P.S. I think that this more like a 6 Ohms speaker after talking to Roy.
Caution comparing to my previous pair of speakers:
I refer to my previous speaker pair often in the text below because this is the only other speaker that I have lived with long enough to make a meaningful comparison. Transporting my speakers to my friends or vice-versa to make other meaningful comparisons is a royal PITA to say the very least! Lest you should think otherwise, my previous speakers cost 3.3X less than these GMA speakers! Hence the comparison is not entirely fair & you readers must keep this performance-to-price factor ratio in mind as you read. There are other constructional & design differences between my previous speakers & the GMA C1.5i. To state a few differences: the previous are a ported design while the present are a sealed box, the previous are non-time aligned, non-minimal phase while the present are time aligned & minimal phase, the previous are 4th order xover while the present are 1st order electrical & acoustical xover.
My Assessment:
· A very musical speaker that hovers very close to a neutral presentation as I’d like. Slightly on the warm side. If 10 is “syrupy warm” & 1 is “scalpel analytical” then the C1.5i would be 5.5 or 6 at the most. My previous speakers were much warmer, say, 7 on the above scale. Of course, the electronics makes a big difference in this matter. In my particular case, I’m comparing my previous speakers with exactly the same electronics.
· The presentation is very non-fatiguing. The soft dome tweeter nearly sounds a ribbon in that the presentation is very life-like & appears to have excellent high frequency extension. Although I managed to reign in the metal dome tweeter on my previous speaker & never really got fatigued by it, this tweeter is far more natural sounding.
· Very true to the recorded music. The performer-is-in-my-room effect is very, very high in this speaker esp. for male (Frank Sinatra, Muddy Waters, Englebert Humperdinck, etc) & female vocals (Sarah Vaughan, Ella Fritzgerald, Diana Krall, Tierney Sutton, etc). Late at night, when the AC power is of much better quality, this effect is very scary/haunting in a nice & satisfying way.
Perhaps this is the direct benefit of being a time-coherent, minimal phase speaker? This aspect has been the subject of much debate & mud-slinging (& I do not want to touch off another spate of it) & it is very difficult for us end-users to verify time-coherent & minimal phase in our rooms via measurements. However, when you hear an LP or a CD wherein you feel that the performance is just being done for you, perhaps you are reaping the benefits of time-coherency & minimal phase.
· Once “exercised” correctly as recommended by Roy in his user manual, the C1.5i are very responsive at lower listening levels such as 65-70dB SPL. I have had to listen to music at these levels as a defference to other members in the house (such as the boss!). The entire content of music seems to be there at these lower volume levels & I do not feel the need for a “loudness” button on my amp as I did with my previous speakers.
· No “boxy” sound from the woofer cabinet unlike my previous speakers. The woofer cabinet is not made of insanely thick MDF; rather, it is made of practically thick MDF but has very strong joints/corners. I understand that the acoustical damping is also “correctly” done by Roy using his vast experience in this field. As a result the bass is very tight (i.e. has a high initial impact & dissipates quickly never overstaying its welcome), natural & plenty for my room. The speakers go down to just 40Hz but I have never missed the 20Hz-40Hz octave personally. Also, the bass is very fast in that it keeps pace with the rest of the music. What this does is that the sound appears to be integral or cut from the same piece of cloth. There is no separate-tweeter-separate-woofer effect unlike my previous speaker.
· The midrange doesn’t beam unlike my previous speaker. I think that this is due to a smaller diameter mid driver + a much more linear one + a judiciously selected xover frequency for this particular driver. This too adds to the integral sound from the speakers as opposed to the mid vocals being recessed 20” or so with my previous speaker. This recession depended on the frequency spectrum of the artist’s voice with the worst manifestation being with higher pitched voices.
· Speakers are very good at portraying a sense of soundstage depth. It is much easier to tell which instruments are back in the soundstage & which ones are in front. Additionally, it is much, much easier to follow the lyrics of a song. This aspect was a very pleasant surprise to me – all of a sudden I didn’t have to read them off the LP inner sleeve!!
· The C1.5i allow me to play every & I mean every single CD & LP in my collection. Some of these are very poorly recorded & compressed but I can sit through the music for a much longer time than I could with my previous speakers. One particular eg. that comes to mind is U2 “All that You can’t leave behind” CD. I really like the music on this CD but this Dutch pressed CD is sibilance city! With my previous speakers, the window panes would crack when I played this CD but with the C1.5i the listening is much more bearable. The CD still sounds like Hell but to a much lesser extent.
· The imaging of these speakers is excellent & very stable. My head does not need to be held in a vice. I can be bopping my head to the beat of the music or doing a Ray Charles-like head movement & the images stay put. They are not twitchy by any means at all.
· The vertical dispersion of these speakers is very poor. The moment I stand up, much is lost immediately. Roy informs us users to keep our ears 0.5-1” below the mid driver, which implies a low seat. Needless to say, if one stands up (you are well above the tweeter now), the sound is merely hi-fi. Not a major objection for me as I always listen sitting down. Plus, I believe that all 1st-order xover speakers have this trait & this one ain’t any different.
Negatives:
· Aesthetically, they have a very low WAF. However, I’m just fine with their looks.
· For this price, one would expect a wood veneer to be the default woofer cabinet rather than black painted MDF. In my particular case, the paint has cracked where the front woofer baffle joins the rest of the cabinet clearly showing the join in the wood – this is not very flattering to look at!!!
· Again, for this price one would expect metal spikes rather than cheaper looking (albeit very sturdy) plastic feet. Roy told me why this so & the reasons seem genuine so I’m being nit-picky here.
· Woofer grills are an additional expense/option! For this price, they should be default, I feel.
· No Green Mountain Audio logo on the front. Again, nit-picky.
· For many of us who believe in biwiring – these speakers are not biwireable by default. Biwiring is an additional expense/option. Per Roy, the benefits are limited & recommended on a case-by-case basis.
· No tweeter & midrange grill. I feel that one could have been provided. For eg., a simple rectangular frame of the same width & depth as the woofer cabinet with grill cloth on all 4 sides + the top & with rubber feet could have looked pretty good. It’s for use when the speakers are not in use as speakers generally sound the best with all grills off.
Other Speakers Auditioned:
None! I bought these C1.5i sight unseen (except for the images Roy emailed me) & sound unheard! Many might call me crazy or stupid! Fine! The point is I have zero buyer’s remorse of my decision! A major part of Roy’s formal education is EE as is mine, so I had a direct email conversation with Roy in which I asked very pointed questions regarding his speaker design philosophy & speaker design theory in general. I quickly gathered that he knew his stuff inside & out. The discussions were purely technical so there was no hand-waving going on. Each time he asked me to verify something, he cited an AES paper I should refer to. So, the proof & his extraction of knowledge came from printed literature some of which appeared long before he even began his GMA company. Au contraire, Roy has gone out of his way to educate me on speaker design. Again, one EE to another, we never believe each other (maybe they teach this to us in school!!) so I was able to find proof of several (not all) things he mentioned outside of our discussion. Again, this raised my confidence in him & his abilities as a speaker designer. It is my opinion that he is genuinely interested in manufacturing a world-class speaker with the fine attributes cited in my review above. I concluded that Roy’s knowledge was solidly based on physics & acoustics & so his speakers would be built on this solid technical knowledge. It is on this that I based my faith & I, personally, have not been disappointed in the least.

Conclusion:
Is this the best speaker for $5000? Is it the “perfect” – whatever that means – speaker system? Who knows? More importantly, who cares? The point is that it does almost everything I was looking for in my next pair of speakers (as explained in my review). It also overcomes the faults of my previous speakers. The things that it doesn’t do as a speaker system are the things that I haven’t thought of! There will always be something better out there – I have to accept this! – and acquiring those goodies is a bridge I’ll cross when I come to it. Meanwhile, the enjoyment factor/foot-tapping factor of the music is very high with these speakers & they take my mind off my equipment. Mission accomplished, I say!

Product Weakness: see review
Product Strengths: see review

Associated Equipment for this Review:
Amplifier:	see inmate section
Preamplifier (or None if Integrated):	see inmate section
Sources (CDP/Turntable):	see inmate section
Speakers:	subject of this review
Cables/Interconnects:	see inmate section
Music Used (Genre/Selections):	jazz, blues, rock, easy listening
Room Comments/Treatments:	see inmate section
Time Period/Length of Audition:	since July 2003
Other (Power Conditioner etc.):	see inmate section
Type of Audition/Review:	Product Owner

Product Weakness:	see review
Product Strengths:	see review