'LGT' Construction Diary

[MJL21193]

Hi Ant,
Unfortunately, my Gulfstream G550 is in the shop for a tune-up. Otherwize, I'd be over there to give a hand in the morning.

(yeah, like my ears are good )

[ShinOBIWAN]

Originally posted by sq225917
Ant, i'm just up the road in sheffield and wiling to lend a hand, i do a lot of compartive listening to other peoples rigs and have recently been shopping for a new set of speakers to replace my Kef ref 203's, so have been listening to some 'daddies' in the 3-5k range.

i could even whack the boys in the boot and bring them over to compare, they aren't the most dynamic speaker but they resolve with a beautiful balance and tone and dig out all the detail you could want.

Also i work from home so can bin off a day pretty much whenever i want.

Thanks Simon really appreciate this. With all that listening it sounds like right now your ears are suitably critical too which is just what the speaker needs.

Can you email me z e r o e x _ 1 5 (hat) h o t m a i l . c o m (I tried to make that spam bot proof the spaces need removing.)

We can arrange from there.

[Salas]

May I suggest a little experiment if you feel like trying it?
Make your extended mid the upper one, and take as measurement axis the midway point between it and the RAAL at 2m. Pursue a 2dB/dec slant towards HF from 200Hz for total response @ 2m. See if that helps female vocals.

[Hezz]

Shin,

Thanks for the fantastic write up on your crossover design approach. Sorry to hear that you are still finding a small portion of the reproduction not quite were you want it. I hate to give any advice since your project pretty much over shadows anything else that I have seen. The female voice covers roughly 200-1000 Hz so if that is where you think something is lacking it could be the just the timbre of the midrange is not quite right. Or maybe it's the upper crossover doing things in the vocal overtones.

Maybe a little more tweaking of the crossover values? Question: Since the PC crossover doesn't have the same interaction problems as an analog passive crossover wouldn't it be good to put that lower crossover right down at the bottom of the male voice fundamentals at 80-100 Hz.

I still think you should experiment with an aperiodic mid range enclosure to approximate infinite baffle for that midrange driver. To see if you like the sound that it makes. Even though the driver may not be specifically made for that type of enclosure it effects the musical timbre to a large degree. Something most engineers never take into consideration.

Anyway, getting a second opinion may be good since after a while you kind of adapt to the sound but in the end it is you that have to be happy with it. However, my thinking is that your speaker may have so many positive attributes that at first a new listener may not notice any weaknesses because they will be so bowled over by the good things which are better than they are used to hearing.

One more thing. I know you experimented with damping material on the rear of the driver. If that midrange driver has one weakness it is that the motor structure is so big that it becomes a reflective surface for the cone to bounce back an out of phase signal into the cone. I know you said that a thick layer of sound deadening material made the sound too over damped. But I wonder if you put a thin layer of felt on all the rear reflective surfaces of the basket and motor structure if that would help at all. Make it sound more refined without be over damped.

All I can say is put on Jane Monheit and if she doesn't sound perfect then something is not quite right. Love that girls voice.

[5th element]

W = 8" upto 200hz
M = 5" 200hz - 800hz
T = Ribbon 2500hz+
M = 5" 200hz - 2500hz
W = 8" up to 200hz

Main problems are a thin upper midrange and a treble that can exacerbate this problem. There are other problems but this is the one that immediately sticks out and is particularly noticeable with female vocals which sound thin and horrible at times.

With this setup I find it odd quite frankly that you're experiencing problems with that area.

Obviously the midrange drivers are whats behind this, in one way or another.

For some perspective the lowest note a soprano is normally called on to sing is a C4, also known as middle C and has a frequency of 260hz. For pop and dance this is somewhat 'high' and one could take a G3 as a rough base line. A G3 has a frequency of 195hz.

Top end soprano, highest note, is a C6. Rarely in certain pieces of music, such as Mozart's the magic flute, the soprano is asked to hit notes higher, in this case a F6 corresponding to a frequency of 1396hz. We can assume around an E5 to be roughly the max a pop or dance singer will hit in what is considered to be 'full voice', = 659hz. Occasionally they go higher, but normally these are not sustained notes.

Quite clearly if we ignore harmonics, the fundamental notes are produced by the midrange. The fundamental is, of course, what will supply the weight to the voice, the harmonics changing the flavour of the voice.

All that aside. We could say, is there perhaps not enough reinforcement from the bass drivers? Well not likely, as they will only have any noticeable effect on the lower end of a womans voice. Not to mention, this is three way, and turning the bass up will make it too bass heavy.

Tweeter. By nature this thing is pretty flat, has low distortion and certainly no issues operating at 2500hz. Also has almost zero impact on the fundamental notes. This is not to say it wont excite problems further below mind you, as you have pointed out; the harmonics are still adding to the sound and will put additional stress on a trouble region.

Now to the midrange drivers themselves. Your arrangement of the midrange operating as a 0.5 automatically provides full BSC and could (if both midrange drivers are driven equally) make it sound a little thick, as you'd give it the full 6dB compensation when only 3dB is needed. Quite the opposite of it sounding 'thin', but as this is fully active anythings possible.

I take it you have experimented with increasing the level of the BSC midrange? If anything, this would provide the 'warmth' to help with the thin sound. Thiness in a voice, to me, means it lacks body, which means its harmonic heavy, ie, not enough fundamental in there, of which most will be reinforced with the BSC mid.

Many folk have commented that they do not like a completely flat loudspeaker, that they find it fatiguing, Linkwitz himself makes it no secret that his loudspeakers have a notch dialed in by a few dB around the 1-3khz region to cool them off. Have you tried this? I know completely flat, to me, starts to sound tiring quite quickly, even if it is very engaging in the first few minutes.

As the midrange is quite capable of playing much higher up, you could try it as an experiment. Cross steeply over to the tweeter at say 4-5khz. This will reduce any effect of driver interactions around the important 1-3khz area. If the subjective thiness is still there then we are, safe to say, that its in the midrange and isn't an artifact coming from somewhere else. Of course the only issue with doing this is beaming and the power response. By crossing over higher up you may create a dip, off axis, this would naturally help to combat the 'flat loudspeaker' around this area and may perhaps be desireable if it gives you a pleasing tonal balance.

[ShinOBIWAN]

Thanks for the replies. It is late now but I will reply tomorrow.

Before I go I have a set of FR graphs showing the individual filtered driver responses and the almost perfect summed response. Clearly loudspeakers don't come much more accurate in technical terms so I don't think this is the problem.

Please note: The bass driver measurement isn't included as I find it near impossible to measure accurately in-room. Instead the original filter is shown. The others are all measurement with 1/24th octave smoothing applied.

Extreme zoomed in FR showing +0.5/-1dB FR performance.
You can see some very minor cancellation between the two mids.


Overall picture:


I will try to take distortion measurements tomorrow but such data taken in-room isn't to be trusted wholey.

[tinitus]

The woofers can cause this, and now that you say that you find it difficult to measure them, I would say that they may very well be the cause - also, you may have a phase issue with this "modified" 0.5way mid
Besides, I have also experienced MTM to have too much upper mid energy and less lowend

[wigginjs]

Shin:

How are you protecting the RAAL from your amplifier?

[ShinOBIWAN]

Originally posted by m0tion
Shin:

How are you protecting the RAAL from your amplifier?

A set of spare ribbons

[wigginjs]

HAH!