TNT-Audio Readers' Corner
Monthly section devoted to your letters, positive and negative feedback about everything related to Audio and HiFi.

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September 2014

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DIY speakers
Hi Mark,
Stumbled on your website quite by accident, but boy I'm so glad I did! I have been 'tampering' in the art of speaker construction since my teens and I am now 59 years old! As you can imagine, many of my designs (especially in the early years of my 'experimentation') can best be described as hit-and-miss. There have been instances however where my so-called 'enclosure design' have actually performed extremely well - hence the continued perseverance in my continued quest to produce the 'perfect' Hi Fi speaker. Your insight into just how the 'jigsaw' of bits and pieces can affect the overall sound has been highly enlightening - even though I have read nearly every relevant publication available!
Thank you so much.
Geoff - E-mail: geoffcrawford1 (at) hotmail.co.uk

MW
Hi Geoff,
Thank you for these kind words.
We would love to hear more about your experiments and your experiences. 'Amateurs' builders, that is, true lovers of the craft, have limited resources to conduct a wide range of experiments. Many anecdotes make data. I am busy with other projects at the moment, but I do intend to write more in future about energy paths, stands, bracing, bass loading, crossover slopes and treble units. I also intend writing about how to improve the loudspeakers we already have. Readers' experiences will add weight to the findings from every experiment.
Happy sawing, drilling, glueing and listening,
Mark Wheeler

Power amplifier choice
I've just bought a pair of used Kef Reference 205 and I realized that my preamp, a Krell HTS 7.1, is good enough for them (I think so...), but my amplifier, an Adcom 7807, has 300W of Home Theater power but not the quality to drive these KEF's.
Reading your amplifier reviews I found the entusiastic one of the Vincent SP-331MK by Maarten van Casteren and I would like to know if his opinion about this amp is still the same after so many years and the arrival of the Hypex NCore NC4000 Class D.
Thanks for the patience.
Best Regards,
Lorenzo - E-mail: arturo.kiwi (at) gmail.com

MvC
Hi Lorenzo,
I haven't heard the Vincent in years, but I'm sure it's still a very good amp. The Hypex NCore NC400 modules are even better. Go for Hypex, if you can. You will not regret it. They're great.
Hope this helps,
Maarten van Casteren

Optimizing moving coil transformers's transient response
I found the articles by Hartmut Quaschik very informative. DIY readers should be aware of the need to properly compensate for optimum transient response and load the secondary.
See the attached photos which clearly show the need to correctly optimize the MC transformer. One shows the ringing that occurs without proper secondary compensation and the final -- not perfect but considerably better -- avoids excessively loading the secondary by just using the phono preamp's input impedance (47K) and an R-C series network across the secondary and a cartridge load resistor of 150 ohms on the primary.
I am currently using Jensen JT-346 AX(T) transformers in the 1:12 configuration and two RC networks on the secondary using 560pf and 4.7K (parts I had on hand). Prior to this change I was using a 6.8K secondary load resistor and one RC network consisting of 560pf and 4.7K (Jensen shows 680pf and 4.12K) on the data sheet. The result of the change is dramatically better instrument placement, depth, and highs -- a more natural sound with less harshness.
I haven't found much on this other than the excellent article on Rothwell's site "moving coil transformer setup explained" which doesn't explain how to correct the transient response but mentions that it is essential for optimum performance. It would be informative if someone could explain the steps and perhaps the reason for an RC network or if other networks are needed. The hump I still have in the final photo would only increase with additional RC networks and larger capacitors would round too much. The secondary resistor may help this at the expense of reducing output amplitude and, from my experience, less open and dynamic sound.
Steven - E-mail: steven_w_97055 (at) yahoo.com
[Jensen preamp frequency response]
[Jensen preamp frequency response]

HQ
Dear Steven,
Thank you for showing us the results of your experiences. Yes, some moving coil transformers show a peak in frequency response, when not loaded with a Zobel, which is a series combination of a resistor with a capacitor. Please note, that you use real world cartridges with those transformers, so for your listening situation, you always have to see the combination of your catridge in use together with the chosen transformer. Many MC carts show a peak even when using a JFET or bipolar input of a phono stage, like some older Lyra cartridges, which have +10dB peaks usually.
In other words, if you want to compensate the transformer frequency range, you always have to compensate the combined frequency of transformer with the moving coil cartridge. Loading the MC transformer also loads the MC cartridge itself, because the MC cartridge also sees the tranformer load, though transformed down.
Cartridge loading is a very complicated matter in itself. Usually, audiophiles use cartridge loading as a means of fine tuning the sound balance of the whole system. So no wonder they use different loadings in different audio setups for the same cartridge. My take on this is, that you may or may not compensate. If you compensate, and you get positive subjective results, then this is great for you.
Best regards,
Hartmut Quaschik

Laspada loudspeakers
I recently came across a new budget speaker for $359.00 + $50.00 shipping. The BL-a speaker is a 6 1/2 woofer by 1 1/8 dome tweeter rated at 89db with a 38hz to 20,000hx frequency response. This speaker is handcrafted in the USA which is almost unheard of at it's price point and manufactured in the USA. Prices of everything being what they are I have to say after listening to this speaker even before break in the sound is incredible. I thought with so many TNT readers looking for budget sound this can not be ignored.
Good Listening,
Thank you,
Richard - E-mail: babydock (at) bellsouth.net

LC
Hi Richard,
thanks for bringing this product to our attention. Indeed, it seems extremely interesting and the "made in USA" thing makes it even more intriguing. As a result, we've aready asked a pair for review, let's see if we succeed...
Thanks for the feedback!
Lucio Cadeddu

VertexAQ Kinabalu platform
[VertexAQ Super Kinabalu equipment platform]
Hello TNT-Audio,
I was trying to understand what has happened to Kinabalu platforms as it seems not to be found any longer on the market. Has Vertex stopped making it altogether?
I am so thrilled about the outstanding performance this platform gives to my CD player (bought both a Audio Emotions) and yet it is not in the market any longer.
Thanks for the attention,
Ernesto - E-mail: ernesto (at) heavenearth.co.uk

LC
Dear Ernesto,
it seems the Kinabalu platform is no longer made but Vertex is working on a new series of such accessories, within the new LeadingEdge series, most of which will be introduced this Autumn, check the LeadingEdge page for updates. Anyway, Kinabalu platforms are quite easy to find on the second hand market, see for example Hifiwigwam or Pinkfishmedia S/H forums.
Hope this helped somehow,
Lucio Cadeddu

Acuhorn speakers
Hey Andy,
I read your review of the Acuhorn speakers. Being a fan of full range set ups (like older Fostex Jericho horn with FE208Sigma...) I am wondering how these compare. Would you have a tip for an alternative given that Acuhorn is now selling considerably cheaper than 1-2 years ago?
Thank you,
Philipp - E-mail: 00klemm (at) gmail.com

AN
Hi Philipp,
I haven't heard the Fostex so can't compare. I did like the Acuhorns - they imaged superbly in the way that only single drivers can - but I thought them extortionate at the "list" price, which the manufacturer told me was 3300 euros. He was, nevertheless, selling some stock at that time for far less money and it seemed to me good value at those sort of sums, around 650-700 UK pounds. This appears to be the price on eBay today, so I think it worth considering.
Regards,
Andy Norman

Silverline Audio Prelude Plus
Hi! I saw in one of your reviews (for the Origin Live Aurora Mk II) that you used the Silverline Audio Prelude Plus speakers. How do/did you like them? Do you ever hear the original Preludes or had a chance to compare them?
Thanks,
Adam - E-mail: acschell (at) gmail.com

TB
Hi Adam,
The Prelude Pluses are excellent. They have 4 drivers per speaker versus 2 in the original. They are fast, transparent and a very nice speaker. I will have a full review ready in a month or so.
Happy listening!
Todd Bromgard

Class D amps
Hi Nick.
I took a look at the Clones Audio amps, and they seem to be an excellent option - but, as you stated, a lot more expensive. But, as you also stated "you get what you pay for". Do you know other brands that make these amps based on the LM3875 (or the LM3886 like Clones Audio also do)? I could only find DIY companies.
Well, at this point I have a few doubts about the performance of these small amps. I always compared the "full discrete" amps and the amps with IC - and the discrete ones sound much better. As I wrote in my previous email, my 40+ years old Kenwood stereo receiver, with only 18 w/ch (full discrete) sounds much better than my 2 years old 5.1 Marantz AV receiver (with 50 w/ch and with IC on its circuits). The old (60's - 70's) vintage amps/receivers, in general, sounds better than the AV multi-channel receivers. For my surprise, in the past 10 days, I've read all these reviews about small amps, all based in some IC (class T, D...), and they seem to sound like tube or transistor old amps. Many reviewers saying that T-Amp, Dayton, Dayens, TBI amps sounds equal or better than famous (and VERY expensive) hi-ends. Is it right? Can we get, with these small amps, the same sound quality of the old vintages Sansui, Pioneer, Kenwood, Marantz... ?
By the way, are the Dayton APA-150 and the serbian Dayens amps class T or D? I am not sure about that. Based on what Ive read all these days, I conclude:

I haven't listened to any of them but, I think all of them can sound fine - despite the price, if we consider a not big room and a good and high sensitivity speakers.
Now I see that I've written a lot - sorry. Small amps are "news" to me, so I am very curious about them. Your opinion and answers are always welcome.
Thanks, again, for your attention.
Marcelo - E-mail: marceloduro (at) hotmail.com

NW
Hi Marcelo,
Oddly, because they are so good, there are very few commercial Gainclone amps on the market. The best way to own one is to have it built for you.
It is so difficult to recommend one amplifier over another, as so much depends on personal taste and the rest of the system. If you are used to the sound of vintage amplifiers, you may be better off staying with them, but perhaps having them recapped. I certainly don't think that the class T/D amps sound like the stuff I heard 40 years ago! The beauty of the smaller amp is when you need a compact system, or perhaps something for your computer desk.
If an amp uses a Tripath chip it is class T.
Regards,
Nick Whetstone

Music from YouTube
Greetings from Adelaide, South Australia! I have been using various PC's and OS to improve my music collection and improve the listening sessions. YouTube has been a great source of new music (type in "horn loudspeakers" or "diy loudspeakers" or 'hifi systems".... ), all this music I have not heard before, everyone has contributed!
Windows7, rip the YouTube clip to usb using Freemake Video Downloader as Flac file, then burn using dbPoweramp CD Writer to disc. Very enjoyable from 12" open baffle drivers in lounge, away at our shack, and in car. Mint Linux, rip cd with Banshee.
Regards,
Tony - E-mail: cmhabich (at) bigpond.com

LC
Dear Tony,
thanks for the feedback but do not forget that the 100% of th music you rip this way (from YouTube or other online sources) is highly compressed (i.e. MP3 or similar algorhythm) so, even if you make a CD out of it...it will still sound as it did originally in the video (i.e. compressed!). When musical information is lost it can't be recovered! Anyway, I agree with you when you say YouTube is a smart way to enjoy new music...provided you are happy with highly compressed MP3's!
Happy listening!
Lucio Cadeddu

Real Father of Real Stereo...
[Theatrophone]
Alan Dower Blumlein did not invent stereo. It was Clement Ader, patented in 1881.
Amazing information for "true stereo", isn't it?
Best regards,
Bruno - E-mail: casier.bruno (at) online.fr

LC
Dear Bruno,
thanks for pointing this out! Actually, Ader invented the Theatrophone, a kind of stereophonic transmission system for broadcasting live opera events via telephonic lines. His intent was that of making listeners aware of the reciprocal singers' position on the stage. Yes, it can be considered the first stereophonic reproduction! Blumlein's works and patents aimed both at improving sound quality (which wasn't one of Ader's intent) and setting up a way to record and reproduce binaural sound on/from discs on loudspeakers. This is the reason why our Real Stereo page refers to him. Actually, if you read CAREFULLY what we write on that page ("The concept of stereo sound recording and playback was invented by Alan Dower Blumlein") it should be clear we do not claim he invented stereo!!!
Thanks for the feedback!
Lucio Cadeddu

Nuforce DDA-100
Hello Andy,
I read your review at TNT which I consider the only objective hifi review web site standing. I wonder if you could tell me if you had heard the NAD 7050 and how it compared to the Nuforce DDA 100? I have heard the NAD 7050 but not the Nu force DDA 100. Very few retailers carry this unit. There is a big price difference between these units.
I have a pair of vintage Electrovoice Sentry 100A studio monitors they are 92 dB efficient, 6 Ohm nominal. I have refurbished them with new drivers from Electrovoice. I am parting with a vingtage Kenwood KR-6030 and would like to downsize my system substantially but would like to stick to hifi 2 channel as opposed to 2.1. Class D seems to be the way for me to go. I have heard great reviews about the NAD 3020 hybrid digital amp, but it lacks power at 30 watts and seems best suited to pair with a 2.1 speaker system, wheres as the 7050 and Nuforce are about 50 watts at 8 ohms and would be much better suited for 2 full range speakers.
Any advice would be welcomed.
Thank You,
Rick - E-mail: rgtk10 (at) gmail.com

AN
Thanks for your letter Rick. We do pride ourselves on our objectivity here at TNT-Audio! To your question - I've not heard the NAD so can't comment on its sound or suitability. It uses similar technology to the NuForce so I'd be surprised if sounded very different. Given the sensitivity of your speakers I don't think you should have much to worry about from the point of view of power unless you have a large room or plan to listen at very high levels constantly.
In any event, the real world difference in dB output between 30 watts and 50 watts is probably little greater than the difference between two designs of 30 or 50 watt amps (or the measurement method used). In your position I'd also investigate separate DACs and low power amps as this will give you more flexibility if you want to change further down the line. The DDA100 is great if you want a neat, classy and convenient desktop solution but I wonder if you could beat it for sound at the price with separates (especially if you can forgo remote control). Why not look at a T-amp of some description (I liked the little Lym Audio amp and there are plenty of others)?
As ever, I'd recommend using suppliers who have enough confidence in their products to offer a trial as it's the only way to tell if something is right is to listen to it.
Hope that helps,
Andy Norman

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