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Multi-Way Conventional loudspeakers with crossovers

NaO Completed - First Impression
NaO Completed - First Impression
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Old 5th July 2006, 12:10 AM   #1
HiFiNutNut is offline HiFiNutNut  Australia
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Default NaO Completed - First Impression

Last night I managed to use some electrical wire to wire up my NaO. It was based on an early NaO plan before John K’s commercial release (http://www.geocities.com/kreskovs/NaO.html and http://www.musicanddesign.com/).

First of all, the whole system includes my own modifications to the NAD542 that is at an entrance level of high-end sound which I am considering it better than any CD players up to $3,500, a 12B4A preamp based on Brett’s circuit that killed a $4,000 Audio Research preamp, Randy Slone’s flagship Optimos power amps – 135W mono blocks for the main panels and 400W mono blocks for the woofers. All used high quality components. All drivers were straight from the boxes. All capacitors in the passive XO are ICW SA Clarity caps. OPA2134s and MKPs are used in the active XO.


What about the sound!

First, what was it compared to? – my own WWMTMWW hybrid (passive and active) speaker I tweaked for nearly 2 years! It has the Dynaudio Esotar T330D tweeter, the most expensive tweeter by Dynaudio. The midrange drivers are Peerless HDS 5’ that many people rate very highly. The woofers are Peerless HDS 8’ that nobody says it is good for bass. Indeed, after 2 years of fine-tuning I found these woofers so hopeless in bass reproduction that it was impossible to get the WWMTMWW sound right so I decided to dump the project (anyone interested in buying the drivers for lower mid frequency range at cheap prices please drop me an email, these drivers are probably fine from 100Hz to 1k). Nevertheless, after zillions of revisions I have made the passive XO between the T330D and the 5’ HDS to sound so good that from 400Hz up it can compare to the very best.


The NaO U-frame woofer.

In an experiment I connected the MTM part of my WWMTMWW to the NaO U-frame woofer. I expected things had to go wrong because I used the existing active XO with no equalization on the U-frame and I crossed high at 200Hz (the first resonance of the U-frame is just above 150Hz from my memory). Much to my surprise, although the response was not ideal, the single 12’ Peerless XLS in the U-frame outperformed 4 x Peerless HDS 8’ in ported enclosures by far, very far. Now I found the solution for my WWMTMWW – get rid of the WWWW (HDS 8’) and replace it with the NaO U-frame with a proper EQ! The My-MTM-plus-NaO-U-frame, I am sure, beats the B&W 801, the JMLab Grand Utopia, etc., in my personal opinion. So I have got a new future project to do.


Now the NaO.

I turned on the system and was initially disappointed – the sound was just DRY! Not much life in the music. Comparing to the My-MTM-plus-NaO-U-frame, there was no comparison. But I totally forgot that all new drivers straight from boxes sound like that!

Slowly, the sound became better and better. 1.5 hour later, the sound was opened up a lot more. Probably the 18W8545 (paper cone) needed a bit of stretches before they could perform.

The NaO sound was quite different from the My-MTM-plus-NaO-U-frame, as the presentations were different. But after the 1.5 hour burn-in, they were at about the same level of performance despite some rather big differences. In some areas, the My-MTM-plus-NaO-U-frame may be better, but in other areas the NaO may be better.

Let me find some words to describe the NaO sound – accurate, low distortion, micro details, no booms, clean, clean and clean from top to bottom.

I played past midnight and I got too excited and turned it louder and louder until the music woke up my 3-year-old kid on the next floor. He was crying and my wife came out of her bed to complain. So after 2 hours listening I had to turn it off.

This morning I listened to it for another 30 minutes before heading to work. I played the Debussy 12 Etudes (Decca the Original) and to be honest, that was the best solo piano music I had ever heard from a Hi-Fi system. The NaO did it superbly. Note that piano sound is possibly the hardest to reproduce due to its rich harmonics. I have never heard a boxed speaker that can reproduce piano music as real as the NaO. I heard the MBL (certainly not a boxed speaker but that one has a boxed woofer and the price tag is 5 digit) previously at a dealer’s room with 5-to-6-digit-price-tag-per-piece equipment driving it and I was quite impressed by its ability to reproduce piano music. There was no A/B comparison, but my impression was that NaO driven by my equipment is just as good, if not better than that particular MBL (not the highest model as I have never heard that one), when playing the piano music.

Wait until my NaO runs in more and after I correct a number of problems I presently have...

I will hopefully upload a photo tomorrow and provide a bit more details.

I am sure that there are many good speaker projects out there. However, given that NaO is this good, I think it should be given a lot more press. I am happy to share here.

More information will be coming in the coming days.

Regards,
Bill
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Old 5th July 2006, 10:33 AM   #2
Nuuk is offline Nuuk  United Kingdom
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Thanks Bill. We can read as much as we want about a particular design but there is nothing like a first-hand report of somebody who has actually built it (apart from the designer of course).

I agree, OB has a lot of advantages over boxed speakers, and piano reproduction is one of them! I look forward to your next report!
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Old 5th July 2006, 12:49 PM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
well, I had to go and have a look, now I know what Na0 is

So ALL the speakers are effectively open backed.

Does the bass go deep? Are there SPL limitations that are worse than boxed bass drivers?
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Old 5th July 2006, 02:12 PM   #4
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by AndrewT
Are there SPL limitations that are worse than boxed bass drivers?

Hi,

By definition the open baffle loss causes reduction in SPL capability
for a driver with a given excursion capability, boxes go a lot louder.

The baffle loss increases 6dB per octave as you go lower, so high
levels of very low bass are impractical, requiring huge excursion.

/sreten.
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Old 5th July 2006, 03:06 PM   #5
Nuuk is offline Nuuk  United Kingdom
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Quote:
By definition the open baffle loss causes reduction in SPL capability
for a driver with a given excursion capability, boxes go a lot louder.

The baffle loss increases 6dB per octave as you go lower, so high
levels of very low bass are impractical, requiring huge excursion.
Absolutely correct of course but with some sort of woofer to support the baffle, this is really not much of a problem for domestic hi-fi unless you live in a warehouse! I certainly don't feel that my system lacks bass!
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Old 5th July 2006, 11:31 PM   #6
HiFiNutNut is offline HiFiNutNut  Australia
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Here is a photo I look last night. My WWMTMWW is put aside.

I have to say I prefer the look of the WWMTMWW but the sound of the NaO.

When I built it, I wasn't sure about its performance especially its SPL on my large room so I did not invest much in the cabinates. I paid a few hundred dollars for a handyman to make them. Now I regrett that.

I will get a furniture making to make a nice pair of cabinates for the NaO as at this stage I think I will keep the NaO for a very long time if not life time.

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I have just arrived at work and will give you my second impression of the NaO when I can spare a few moments.

Most of you guys are on the other side of the globe (or I am on the other side) so while you guys are active in the forums I am probably in bed and while I can write in the forums you guys are possibly in bed.

Regards,
Bill
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Old 6th July 2006, 12:43 AM   #7
tktran303 is offline tktran303  Australia
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Hi Bill,

The NaO is probably one of those "evergreen" speakers that will last a lifetime. It uses classic tried and trusted drive elements, and the amount of engineering behind the design is far beyond what most DIYers will ever be capable, or even thought of.

You should definitely build some pretty cabinets for it.

I'm looking forward to hearing more about your NaO after you've had the chance to run in the drive units (typically loosens up the suspension and spider) and found the optimal speaker placement in your room.


....
Anyway, regarding your own DIY attempt at the WWMTMWW- do you have much in the way of measuring equipment?

The "old text-book passive crossover" or "active crossovers purchased over the shelf" will not allow the speaker to reach anywhere near it's potential. Designing a complex multiway speakers such as a WWMTMWW will invariably need measurement tools. And after being armed with all these tools, we need to do further research and build up experience level with designing crossovers.

A lot of DIYers dive into the deep end, and don't bother too much with measurements ("Trust our ears" we cry!) but if we can't pinpoint the exact problem, how are we going to fix it? We can try tweak after tweak after tweak, and sometimes we go forward other times it takes us a step backwards. But the best we're doing is shooting in the dark.
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Old 6th July 2006, 05:23 AM   #8
HiFiNutNut is offline HiFiNutNut  Australia
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You guys are spot on! everything you said is right!

Now, the second impression.

I have now played it 2.5 hours more and the sound is opened up more and more. The Seas Excel Millennium tweeter and the ScanSpeak’s 18W5845 mid woofers have now a total run-in time of 5 hours. I guess they should be about 85% run-in. The rest may take another a few weeks.

Remember I said the NaO was very different from the MyMTM-plus-NaO-U-Frame? I should start calling it myMTM now to make the word shorter. Amusingly, after the run-in, the gap between the two has narrowed considerably.

This is because myMTM, also open back (I won’t call it a dipole though), was no lesser than a reference type of speaker from 300-400Hz up and can compare to most of anything else out there. It was run-in and tweaked for 2 years and is close to perfection. It throws out such an accurate, very deep, very wide and tall 3-D image and the sound is very smooth and musical, thanks for the great Esotar T330D and the HDS 5’ doing a good job.

Previously, myMTM was better than the NaO in the openness of the sound / the disappearing act (it may still be the case until the NaO is fully run-in), but the NaO is closing up, as for now, which speaker is better depending on what types of music I play:


NaO (after 5 hours run-in) vs myMTM

Noah Jones’ debut album – hard to say which is better, only small differences.
John Martin Solid Air - hard to say which is better.

Eden of North – Sum of Us – myMTM killed the NaO.
Jennifer Warm – myMTM betters the NaO by a small margin?
Johnny Cash - myMTM betters the NaO by a small margin.
Mozart Violin Concerto – myMTM betters the NaO by a small margin.
Miles Davis – A Kind of Blue – myMTM betters the NaO by a small margin.

Church Organ and Choral – NaO killed myMTM.
Solo piano music – NaO killed myMTM.
Britten’s Stage show – NaO killed myMTM.
William Tell by Telarc – NaO killed myMTM.


Where myMTM is better -

The NaO is limited in SPL of the Excel tweeter. myMTM is significantly better when high SPL is required. It has 94 dB sensitivity and in my 9 metre wide x 13 metre long x high ceiling relatively large and dead room, when live music level is required with high impacts, the myMTM can deliver the power in an awesome, spectacular way without letting you feel fatigue whatsoever. The XO between the T330D and the HDS was nearly perfected. Female voices are super smooth. I can say I prefer the T330D tweeter (from my memory it has the power handing capability of around 200-300W RMS continues and peak over 1000W) over the Seas Excel Millennium tweeter T25CF-002. It seems the sound of T330D is more natural. That is why when it comes to Mozart’s Violin Concerto (Decca Legend) when playing loud David Oistrakh’s violin sounds better from the T330D than from the T25CF-002. I played violin when I was a boy and am familiar with life classical music instrument sound.

In contrast, there is a small hint of grain or edge from 1k up somewhere in the NaO which affects the violin sound as well as human voice reproduction. Does this make me believe the T330D is better than the T25CF-002? Possibly. That is the area where myMTM wins over the NaO by a small margin in Eden of North, Jennifer Warm and Johnny Cash. Another problem with the NaO is that I found somewhere from 80Hz to 150Hz the sound is lacking which gives myMTM a ticket to win. The result is that the myMTM has more impacts for certain music with a fuller sound while the NaO sounds a bit thin. That is why for Eden of North and A Kind of Blue myMTM won. But I have to confess this is not John K’s fault – I was one of the earliest guys who got the free NaO plan and I only had the NaO EQ and the Peerless XLS 12’ EQ schematics hand-drawn by John K. John K at the time recommended using the standard LR4 while I used the 3rd order Bessel for the NaO and probably that ruined the frequency response between 80Hz to 150Hz. I have to say my NaO was not implemented exactly according to John’s plan because I had not had enough time. I simply quickly put them together to test the sound. I hope I have not done the active XO incorrectly. Note that my NaO is not the later, more tested and matured NaO II in John’s commercial release.


Where the NaO wins:

Where details are required the NaO blows the myMTM away. The T330D probably has the details of the T25CF-002 but the 18W5845 kills the HDS 5’ instantly. There was no contest. The HDS 5’ gives a more rounded (i.e. coloured) sound that is quite natural and musical but do not have the details of the 18W5845. If you ask me which one I prefer I say I prefer the 18W5845 without a doubt. The clean sound of dipole also plays a role here. This gives a lot more realism to the music.

In the dynamic department again the NaO killed the myMTM. Is this because of the 18W5848? I don’t know. The myMTM is already a very dynamic speaker but the NaO is still more dynamic.

Transient is excellent with the NaO. So it won on solo piano music, William Tell by Telarc, Britten’s stage show and many other CDs I have.

The 3-D effect is getting better along run-in. Voices sound real (dispite the above mentioned slight problem). Drums were hit fast with might. There are no booms-booms-booms. No bass hung-over.



After 5 hours run-in, if you ask me which speaker is better, I’d say the NaO. I am sure once I corrected a number of problems with my implementation of the NaO, it may sound faultless.

In the coming weekend, I will do some changes to my NaO. When I wired up the passive XO for all the switches I simply chose the mean value and had no time to study what they do. I will experiment with various values to get the best sound. John K said the stuffing material for the U-frame must be either fibreglass or wool. I didn’t know where I could get wool so I temporarily use Polyfill that John had already said useless. There are others, too.

More to come…

Regards,
Bill
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Old 6th July 2006, 07:06 AM   #9
HiFiNutNut is offline HiFiNutNut  Australia
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Andrew T - "Does the bass go deep?"

Yes the NaO bass goes VERY DEEP. Funny though, one would expect that the NaO U-frame would be bottomed first. I have not found that to be a problem yet or perhaps I was ignorant. I played the famous Cantata Domino CD by Proprius and that church organ did not bottom the NaO U-frame. Neither did the Particia Barber's Cafe Blue. I played it quite loud in my fairly large room.

Seriously, I have a new problem. When the NaO goes deep down a lot of vibration noises came from everywhere in my room - the glasses in the wine bar, windows, and who knows where they come from. The noise are loud and very annoying. When I have time I have to debug the problem and remove those items. I can't remove the windows though.


Andrew T - "Are there SPL limitations that are worse than boxed bass drivers?"

After I got the plan from John K, I had some email exchanges with him. It was a long time ago. I remember John said the SPL was limited to the Excel Tweeter.

As said, the U-frame with a 12' XLS may be fine. I did find limitation on the main panel. With my 9 x 13 metre fairly large and dead room, I wish the NaO could play a bit louder. It is generally loud enough for 80% of my music, but just, or I am pushing it to its limit. If I want to play very loud, the NaO main panel would struggle.

I have to mention one thing - I often play music very loud to live level with myMTM. I stay upstairs most of the time and I just let myMTM downstairs to play loud. That is very loud. If you are not as crazy as me or if you have a smaller room then the NaO may be loud enough for you.

Why Dynaudio stopped making the Esotar T330D? I could image if John K started his NaO design with the Esotar... the NaO would be the ultimate speaker!!!
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Old 6th July 2006, 07:59 AM   #10
HiFiNutNut is offline HiFiNutNut  Australia
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tktran303,

You are absolutely right. For my WWMTMWW I did the XO in the hardest, most stupid way without measuring equipment. I love to have the measuring equipment but I don't know what microphone to get and all the microphones mentioned in the forum seem to be only available overseas but not in OZ. I really want to have it now.

However, from very early on I had abandoned the text book XO formulaes. I entered the FRD and ZMA files manually according to the manufacturers' data sheets into Speaker Workshop and other software provided in the Frequency Response Consortium website. I have to say the data sheets seem to be quite accurate.

All the XOs I tried were first modelled in Speaker Workshop, and I have tried textbook like 1st order, 2nd order, 3rd order and 4th order and more.

I have tried series XO as well and found for the T330D and the HDS 5' the Real Accoustic's series XO sounds very good - of course I don't use their recommended values but SW's. But it was not perfect and there was one problem I could not rectify - that is with series XOs - not easy to alter the FR near the XO. So it was abandoned.

I have tried various XO points from 2k to 9k in parallel networks. Eventually, I got this:


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The small dip between 2k to 5k is deliberate as it sounds better (still a lot smaller than the BBC dip). I prefer the HF not too dominant so don't mind the 1dB lower towards HF. Baffle step is at 410Hz and that can be compensated by boosting the woofer by up to 3 dB. Diffraction was not considered.

Note that from 200Hz to 10kHz the variation from SW is only +-1.5dB.

If you see the graph carefully, the XO point is just about 3.1kHz. At about 1.65k it was 24dB down. At about 6.2k it was 24dB down (the HDS should be seen as 6dB higher as the 2 HDS are connected in parallel). At XO point it is close to 6dB down. This is a LR4 network.

I achieved this by this very simple schematic, the result of two years efforts:


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Before the final schematic was fixed, I tuned the resistors by increasing / decreasing 0.05 ohms and wind / unwind inductors by 1/3 turn at a time to get the optimal sound. It was extraordinary tedius and I swear I won't do it again in the same way.

For the active XO, I used 3rd order Bessel. I used only 2 opamps for the HF and 2 opamps in the LF. This includes attenuation as well as input buffer.
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