Lowther Opus One Model B Build Thread

[CLS]

Hi Peter,

It's very interesting as I read the Jordon MLTL project in your blog. You mentioned that the Jordan is generally smoother and more realistic than Lowther (in Acousta, IIRC).

Now this Opus One is much larger than the Acousta, and also a compound horn with front loaded section, so I'd guess it's several steps ahead -- as you said, it's much more enjoyable than the (once beloved) Jordan MLTL! 😀

I also feel speakers with high sensitivity usually have the edge in dynamics, details... etc., especially in head to head comparisons. Like a picture with wider range and higher contrast in gray scale and color is always grabbing people's attention.

I'd bet your Opus One sounds wonderfully vivid and blooming. I've had a short period of experience with PM4 in a 150Hz tractrix front horn (Oris 150) and I liked the sound very much. It's not harsh at all, only slightly forward but warm balanced. Under certain SPL, I think its details and dynamics are in the same level of a high quality compression driver in a proper horn.

Horn is a beast. You have to make it big (enough) to perform well. For bass it's a real challenge. Congratulations, again!


ps. Don't get me wrong, I'm not saying Jordan is bad. I own and use a pair of Jordan every day. I also like them very much. Just another different but also good flavor.

 

[Peter Huang]

Congratulations Peter,

I do not know how long you have had them playing but do you think that the end result or all of that hard labour and effort were worth it?

Are they that much better than the other Lowther horns you had before?

Andrew

Hi, Andrew,

This project is absolutely worthy of hard-working, but the precondition is that you have two strong corners.
The Opus one B with PM4A is more detailed, clear, clean and dynamic than Acousta 115 with DX3 and Academy with PM6A and PM6C. The bass of Opus one B is not stronger, but more natural and clearer, even placed into the corner. The bass of Acousta 115 is not clear which reflects resonant in the cabinet and mouth. The Academy which has two drivers each cabinet has its own characteristics: the bass is not strong but the atmosphere is great. The sound stage of Opus one B is the best of them.

Although I don't put any damping material into the compression chamber of Opus one, I can't hear high frequency and resonant coming from its mouth. However, I can hear some HF and resonant from the mouth of Acousta 115; and I have to test and add some fiber into its compression chamber. The parallels of Acousta 115’s mouth let them hard to put into the corner to enhance tits bass. I couldn’t put the driver PM4A into Acousta 115 or Academy to test, because their design of throat and compression chamber is not suitable for PM4A. The performance of middle and high frequency of PM4A is much much better than the ones of PM6A and DX3.

I would like to state that the above statement is my own subjective feeling. The performance may be quite different in different audio rooms and connected gears.

Thanks a lot for your interesting and question.

Regards,

 

[Peter Huang]

Hi Peter,

Horn is a beast. You have to make it big (enough) to perform well. For bass it's a real challenge.

I agree with you!

I listened to a pair of Dynaudio Contour 4.0 drived by 350W amplifier at my friend's place before, almost no bass. My friend uses a push-pull subwoofer with two peerless drivers to enhance the bass.

Using horn to enhance the bass seems to be one of the easier and simpler ways.

I think that the bass performance of a horn has been determined in the design stage. I calculated the necessary mouth size of Opus one, which shows Opus one is still not big enough, still compromising. I don't want to challenge Opus one's bass now, but maybe add a subwoofer latter.

Thanks for your response. Cheers!

 

[Peter Huang]

Very impressive. I have a hard enough time trying to glue up 6 panels....

Josh

It also should be a very skilful work! You may wish to have more hands and eyes.

Thanks for your interest.

Regards,

 

[head1962]

It also should be a very skilful work! You may wish to have more hands and eyes.

Thanks for your interest.

Regards,

Hi Peter,
Job well done!!
this is what I meant when I said, you need 5 hands!
It looks absolutely great!

Gerrit

 

[Peter Huang]

Hi Peter,
Job well done!!
this is what I meant when I said, you need 5 hands!
It looks absolutely great!

Gerrit

Thank you, Gerrit.

When we have only two hands, we brainstorm how to do the difficult job which needs five hands.
If we would have 5 hands, our brain might have the difficulty to manage so many hands.

Would you please give me a link to your difficult work?
I am curious. Thank you.

Regards,

 

[head1962]

Hello Peter,

this is what I do in my free time and with 2 hands only.
TIME MACHINES AND TUBE AMPS
on the right hand side you can click on different "sub" links.
The Klipsch eckhorn is not on it because the internet did not exist when I made it ;-))

best regards,
Gerrit

 

[soongsc]

I agree with you!

I listened to a pair of Dynaudio Contour 4.0 drived by 350W amplifier at my friend's place before, almost no bass. My friend uses a push-pull subwoofer with two peerless drivers to enhance the bass.

Using horn to enhance the bass seems to be one of the easier and simpler ways.

I think that the bass performance of a horn has been determined in the design stage. I calculated the necessary mouth size of Opus one, which shows Opus one is still not big enough, still compromising. I don't want to challenge Opus one's bass now, but maybe add a subwoofer latter.

Thanks for your response. Cheers!

Many speaker of the configuration similar to Dynaudio Contour 4.0 have similar problems. The issue is using the wrong amplifier.

 

[Peter Huang]

Hello Peter,

this is what I do in my free time and with 2 hands only.
TIME MACHINES AND TUBE AMPS
on the right hand side you can click on different "sub" links.
The Klipsch eckhorn is not on it because the internet did not exist when I made it ;-))

best regards,
Gerrit

Hello, Gerrit

Those are your masterpieces. How inspired works!
You have been making something different.
Swiss always is an expert of making the time.

Best Regards,
Peter

 

[Peter Huang]

The Opus One now gets into the corner standing with their elder brothers.
I am surprised; up to now I just noticed that the Opus one looks so large compared with Acousta 115 and Academy.

I just listen W. A. Mozart's Konzert fur Klarinette played by Prinz.
Every note became different!

 

[Rick J. B.]

Wow, Peter, very impressive!

 

[Zen Mod]

I just hope that your enjoyment was (and is) equal to look of it , and that sound isn't much below that

 

[Peter Huang]

Lowther Opus One model B

Hi, Rick and Zen Mod

Thanks for your interest.
The build work is difficult and exciting. The sound is wonderful.
The looks are just so so.

Test equipment:
Preamplifier: Pass BOSOZ(Bride of Son of Zen)
Power Amplifier #1: Pass x-SOZ(Son of Zen) with IRFP250, about 7W output
Power Amplifier #2: Pass Zen V9/FirstWatt F3, 15W output
CD Player: DPA Enlightenment
DAC #1: DPA Enlightenment DAC
DAC #2: DAC4395 platium (Diy kit)

Dear Zen Mod, you may strongly covet to listen this big horn driven by Nelson Pass's design. 1W is enough. 3W will be too loudy.

Cheers!

 

[Peter Huang]

SPL measurement for Lowther opus one model B

I just measured the SPL response for lowther Opus one model B. The measurement may be not quite accurate, but very informative!

The sound lever meter used here is Radio shack (realistic) model 33-2025(older type). The measured distance is above 4m, on-axis, and the same height, faced to driver PM4A. The measured data is corrected by using the data from Audiogon for the meter.

Please note that the big peak at 62Hz which should be a room resonance. The distance between the ceiling and base of my listen room is about 2.8m, so that the theoretical resonance frequency should be 345/(2.8x2)=62Hz. The measured resonance is quite matched to the acoustic theory.

Other minor peaks between 60-120Hz may be resonances result from some furnitures, such as the tables, cabinets or chairs. The distances between the ceiling and those furnitures are about 1.5-2m.

After examining the diagram, I think that the LF response of Lowther Opus one B is rolled off from 100/120Hz with a slope of about 24dB/octave.

I would like to highlight that Lowther Opus one model B is really an excellent speaker. I am so surprised that I can hear and feel the sound wave of 30Hz during measuring, although which is about 60dB only. I still agree that the Opus one B really doesn’t need a subwoofer to play the bass, as mentioned before by many audiophiles. However, I crave to use above measurement to design a pair of subwoofers using peerless, 12” model-835017.

I also found that I could hear nothing for the 12.5K and 16 KHz signals, although the meter shows 80 and 70 db respectively. I may have some ear problems. 😡

Any comment or suggestion is appreciated. Thanks a lot.

 

[hm]

Hello,
such big and no bass?
the difference between left and right is too much

 

[Peter Huang]

Hello,
such big and no bass?
the difference between left and right is too much

Please note that the averge SPL of whole spectrum is 80db for both channels.
If I increased the volume to get the averge SPL to 100dB, then the 30Hz level will shift to 80db.

The opus definitely has bass but not strong.
The bass is moderate and enough for classic music.
I think the response difference between left and right channels mainly result from the alignment angle error of the meter toward the driver's center.
The HF response of Lowther PM4A, even with a front horn, is very very directional!
The angle alignment seems to be difficult for the opus-shaped horn.
I may try to measure them again, more accurately.

I think there is no horn is large enough, but the room space is limited.
I admire your horn designs.
I found that the bass response of Fostex drivers is about 10db louder than lowther's.

 

[hm]

Hello Peter,

for our ear brain is the left right not difference more important as the problems of a box itself.
I don´t believe in such a big difference of a Pm4, so better make new measurements,
near field driver 1 cm out of axis, near field horn mouth, fullrange if 1 m does not match to the bass try 2 m, and important make a IMP measurement.

nice project.

 

[Peter Huang]

Hi, Horst Möller, thanks for your very positive suggestion. I measured the near-field responses and combined with previous far-field one to make a comparison, as shown.

There are three measurements, all on-axis, only for left channel. The far-field measurement is located at 4m, the same as the ordinary listen position. The near-field measurement at 2m is used to as a typical comparison base. The third measurement is located at 26cm from the driver’s cone center, almost just in front of the front horn mouth. The measured data are Levelized to the same value of 70db at 1Khz.

By examining the diagram, there are three essential phenomenons which I would like to emphasize. The first one I noticed is that the fare-field response around 8 kHz is attenuated about 12dB compared to the near-field one at 26cm. The front horn seems to have a strong performance to reduce the HF shouts, sometime criticized for Lowther’s stronger drivers.

In addition, the room resonant peak at 60Hz is almost disappeared at near-field responses.

The deep dip at about 1.1Khz of near-field measurement at 26m is quite difficult for me to understand.

Any comment or suggestion will be highly appreciated. Thanks.

 

[Khoigia]

Very Beautiful speakers..... Congratulate your hard work..

 

[hm]

Peter,
"deep dip" because the horn is at that wave length to large, reflexions in the mouth
delete at that mic point with that wave length.

Now i would make measurements at the listening place, and make an individual
notch filter for each box, to make l/r measurements equal as possible,
the area around 300 Hz is to loud, to much front horn performens and rest of
bass horn.

for Also sprach Zarathustra you need a sub.