Golden Ratio speakers?!

LeifB60

Member
2015-05-18 5:50 pm
Sweden
It's not Nostromo then so best not described as such.

Duct length in itself will have zero influence on anything in the 7KHz - 12KHz band; nominal tuning is < 100Hz & any 1/2 wave modes should be heavily suppressed and far below that region; if you have problems it's from a different cause. Very large, shallow chamfers may reduce a small amount of edge diffraction at the lower end of that range but primary influence will likely be in the ~1KHz - 3KHz region. You don't specify how you're identifying these issues, but I suspect some methodological variation may be at work.

Re the box, 16mm MDF will have audible colourations from panel resonance unless heavily braced and / or strategically damped with bitumen a la BBC type designs (albeit is a bit thick for those). The foam appears to be the type I recommend not using for this construction. Forgive me, but I don't recall what the driving amplifier is, but if it is not a high output impedance SET, then you may also have a mismatch, as that box was designed for those conditions.
Yes it can be due to several things.
Right now I am listening to a KlassD amplifier with ICEpower output stage. 2x500w. Of course, it may have affected the sound in the wrong direction.
Do not know if it has high or low output impedance.
When I used my tube amplifier, I did not experience the same disturbance in the 7khz-12khz range.
Certainly affects the amplifier.
KlassD has more controlled bass and is completely balanced from the CD player to the speakers but not as good treble.
 
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OK, so assuming it's the largest of the Nostromo boxes, which from your description is what appears to be the case, then low output impedance class D amplifiers are exactly the type of amplifier I said in the plans that cabinet is not designed for, which partly explains why you are having some issues, aside from departing from the damping, construction materials &c. Note on the front page where it says:

Standard and larger size enclosures suitable for use with high output impedance amplifiers.
Smaller enclosure optimised for low output impedance amplifier designs
and
Large:
for SETs with output impedance <~4.0Ω
(or other high output impedance amplifiers)

With a class D amplifier it's hovering between maximally flat (rarely a good alignment) and a very shallow EBS. While the amplifier will have plenty of electrical damping, the acoustic alignment is unlikely to suit many spaces unless pulled well out from room boundaries, and having a moderately sharp tuning the effect may be audible. Note this is not the designed alignment, just the result. With a SET or equivalent of about 2.5ohms output impedance (placing in a crucible for averaging purposes), the alignment is as designed, with a slight ~ 1/2dB rise through the upper & midbass, a relatively well-damped rolloff & broader box output through the effectively elevated Q. That was the target alignment and voicing for the design. If you require something different, you need a different design.
 
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OK, so assuming it's the largest of the Nostromo boxes, which from your description is what appears to be the case, then low output impedance class D amplifiers are exactly the type of amplifier I said in the plans that cabinet is not designed for, which partly explains why you are having some issues, aside from departing from the damping, construction materials &c. Note on the front page where it says:


and


With a class D amplifier it's hovering between maximally flat (rarely a good alignment) and a very shallow EBS. While the amplifier will have plenty of electrical damping, the acoustic alignment is unlikely to suit many spaces unless pulled well out from room boundaries, and having a moderately sharp tuning the effect may be audible. Note this is not the designed alignment, just the result. With a SET or equivalent of about 2.5ohms output impedance (placing in a crucible for averaging purposes), the alignment is as designed, with a slight ~ 1/2dB rise through the upper & midbass, a relatively well-damped rolloff & broader box output through the effectively elevated Q. That was the target alignment and voicing for the design. If you require something different, you need a different design.
Well that is why it didn't match KlassD.
But I built them to the tubeamp and they were awesome. No problems.
Thank for explaining.
 

LeifB60

Member
2015-05-18 5:50 pm
Sweden
Now I have been listening to my modified Nostromo speakers for a 20 hours. It is the length 10cm (4 inches) on the bass reflex tube and 40 ° edges that make these something special to listen to. Love that they place the different instruments and voices in an exact place in the soundscape.
It is a pure pleasure to listen. 16 liter big box is the right one for me.

The bass goes deep and is dry and detailed.

When I increase the volume, the bass gets more power and it is difficult not to stomp the beat. You get caught up in the music. It sounds a lot like high end at a price that must be seen as a robbery. Thanks.
 
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