This is a review, listening tests and detailed measurements of the vintage Miller & Kreisel (M&K) S-150THX Home Theater Speaker. It is on kind loan from a member and costs US $1,500 for a pair back in mid 1990s.
I don't know how many of you were in home theater back then but the M&K speakers were cat's meow due to their use in film sound mastering. Folks would point to the pictures of them soffit mounted there and stand back and say, "this is why I bought it!" It was a sign of having arrived in home theater. I didn't own these bookshelves but did have their massive subs for my theater. I always envisioned these to be a large speaker but they are quite tiny at just a foot high. The face slanted so if the back is against the wall, it toes in automatically toward the center.
Back panel harkens back to days where companies put their address on the back of their products!
And those were also the day when having THX logo carried the water for you, hence the designation here. Despite strong fan support company went bankrupt and then came back a while later. I looked at they have replaced foams around the tweeters with waveguides. But otherwise they look similar.
Was the reputation well deserved? Let's measure and listen to see if that is so.
M&K S-150THX Measurements
Let's start with our Klippel NFS anechoic measurements:
Color me surprised with that flat on axis response! Five drivers working together and they still produced a flat response. Quite remarkable. Alas, physics is hard to avoid and the drivers interfere with each other causing beam forming/narrowing of the response. We see that in the off-axis response having less energy above 800 Hz. We can see that clearly in the vertical axis:
In an interview the designer said this was actually a THX requirement that you have to sit precisely on axis with zero deviation from that! That's cool but this uneven off-axis bounces around the room still and creates an uneven response:
I tried to draw a straight line but that is not really possible. Still not too bad. We can drill more into the directivity:
Since the speaker has non-symmetrical, you get rough response going to the right of the speaker:
The issue as mentioned is much more severe in vertical axis:
Multiple drivers mess up the directivity but do wonders for power ability:
Again, keep in mind that this is a small bookshelf size/studio monitor speaker.
Impedance is rated at 4 ohm but as usual, that is a bit of wishful thinking:
There is a distinct resonance around 5 kHz in the waterfall plot but I don't see it elsewhere which is kind of odd:
Finally, here is the step response:
M&K S-150THX Listening Tests and Equalization
This is the kind of speaker that stomps a subjective reviewer. It at the same time sounds right and wrong. While I could not find much fault with it, I also didn't enjoy anything I played on it either! One thing I did notice was that the sound was coming from the small footprint of the speaker likely due to narrow vertical dispersion. There was nothing to EQ as far as on-axis so I resorted to using the predicted in-room response as a guide to boost the lower treble:
That made the sound more open but also somewhat bright. So I put in a bass boost as if this was a ported speaker. The combination made a dramatic difference. The sound was now much more open and "high-fi" for the lack of a better term. We had good bass and the sound became more diffused, enlarging the halo of the speaker. I detected no sign of stress in the speaker despite that bass boost. Power handling remained very good.
Conclusions
Nice to go and really evaluate products that had a strong buzz around them in a different era. The S-150 shows some of the characteristics that made it famous as far as low distortion and flat on-axis response. But physics of sound caught up to it causing uneven off-axis response. The tonality we hear is the combination of those two which was not to my liking. Some EQ fixed that though. And I should note that in real application this speaker would be crossed to a sub and have some sort of EQ applied to it. Overall not bad!
----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
I don't know how many of you were in home theater back then but the M&K speakers were cat's meow due to their use in film sound mastering. Folks would point to the pictures of them soffit mounted there and stand back and say, "this is why I bought it!" It was a sign of having arrived in home theater. I didn't own these bookshelves but did have their massive subs for my theater. I always envisioned these to be a large speaker but they are quite tiny at just a foot high. The face slanted so if the back is against the wall, it toes in automatically toward the center.
Back panel harkens back to days where companies put their address on the back of their products!
And those were also the day when having THX logo carried the water for you, hence the designation here. Despite strong fan support company went bankrupt and then came back a while later. I looked at they have replaced foams around the tweeters with waveguides. But otherwise they look similar.
Was the reputation well deserved? Let's measure and listen to see if that is so.
M&K S-150THX Measurements
Let's start with our Klippel NFS anechoic measurements:
Color me surprised with that flat on axis response! Five drivers working together and they still produced a flat response. Quite remarkable. Alas, physics is hard to avoid and the drivers interfere with each other causing beam forming/narrowing of the response. We see that in the off-axis response having less energy above 800 Hz. We can see that clearly in the vertical axis:
In an interview the designer said this was actually a THX requirement that you have to sit precisely on axis with zero deviation from that! That's cool but this uneven off-axis bounces around the room still and creates an uneven response:
I tried to draw a straight line but that is not really possible. Still not too bad. We can drill more into the directivity:
Since the speaker has non-symmetrical, you get rough response going to the right of the speaker:
The issue as mentioned is much more severe in vertical axis:
Multiple drivers mess up the directivity but do wonders for power ability:
Again, keep in mind that this is a small bookshelf size/studio monitor speaker.
Impedance is rated at 4 ohm but as usual, that is a bit of wishful thinking:
There is a distinct resonance around 5 kHz in the waterfall plot but I don't see it elsewhere which is kind of odd:
Finally, here is the step response:
M&K S-150THX Listening Tests and Equalization
This is the kind of speaker that stomps a subjective reviewer. It at the same time sounds right and wrong. While I could not find much fault with it, I also didn't enjoy anything I played on it either! One thing I did notice was that the sound was coming from the small footprint of the speaker likely due to narrow vertical dispersion. There was nothing to EQ as far as on-axis so I resorted to using the predicted in-room response as a guide to boost the lower treble:
That made the sound more open but also somewhat bright. So I put in a bass boost as if this was a ported speaker. The combination made a dramatic difference. The sound was now much more open and "high-fi" for the lack of a better term. We had good bass and the sound became more diffused, enlarging the halo of the speaker. I detected no sign of stress in the speaker despite that bass boost. Power handling remained very good.
Conclusions
Nice to go and really evaluate products that had a strong buzz around them in a different era. The S-150 shows some of the characteristics that made it famous as far as low distortion and flat on-axis response. But physics of sound caught up to it causing uneven off-axis response. The tonality we hear is the combination of those two which was not to my liking. Some EQ fixed that though. And I should note that in real application this speaker would be crossed to a sub and have some sort of EQ applied to it. Overall not bad!
----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
