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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March 2016

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Re: Maverick audio speakers
Thank you for the response. This is going to be essentially a desktop system. I'm now looking at the Cambridge audio s20s. As I understand it they have less bass than the bs22s. I'm curious to know how they stack up otherwise? Fact of the matter is the Maverick Audio is pretty thin bass wise anyway so a small sub is likely in my future anyway.
Thank you again,
Steve - E-mail: sbenton.benton3 (at)

Dear Steve,
the Cambridge Audio S20's are good speakers for the money. Probably they do not sound as well as the Pioneer BS22's but you won't be disappointed, that's for sure!
Adding a subwoofer might be a good idea, as micro-speakers can't reproduce proper, deep and powerful bass. For example, the S20's are claimed to reproduce bass frequencies starting from 80 Hz while the BS22's are claimed to reproduce even 55 Hz (a bit optimistic, maybe!).
Keep me updated,
Lucio Cadeddu

Maverick audio speakers
I was just reading your review of the Maverick Audio A1 and had a question in regards to speaker selection. I was considering the 4 ohm Micca mb42x or the Pioneer 6 ohm bs22. Which would serve the amp better?
Thank you for any feedback.
Steve - E-mail: sbenton.benton3 (at)

Dear Steve,
in my opinion you should consider 8 Ohm speakers instead, since the National chipset that equips the Maverick doesn't seem to welcome low impedances. A 4 Ohm loudspeaker can be a rather difficult load, since nominal impedance doesn't mean the 4 Ohms remain constant. There might be portions of the audio spectrum where the impedance is much, much lower! Hence, choose 8 Ohm loudspeakers and, if you need some extra sound pressure, choose high sensitivity speakers (e.g. Klipsch).
In any case, since you seems to prefer extra-small speakers like the ones you mention, I'd choose the Pioneer BS22's, as their impedance is a bit more friendly.
Hope this helped somehow,
Lucio Cadeddu

Congratulations (belatedly) on 20 years of the site, I have been reading for most of those. TNT still manages to get the balance right between top end and affordable encouraging others not only to begin but become involved in this hobby. That's worth commendation alone.
Here's to the next twenty years.
Tony - E-mail: t_mcilwee (at)

Dear Tony,
thanks for your kind words of appreciation and encouragement, we always need your support! The perspective of two other decades of continuous efforts to keep this mag going is sometimes frightening, but passion and enthusiasm seem here to stay, despite all the difficulties and the last 20 years of devotion. We're hiring new reviewers who, hopefully, will bring new ideas and viewpoints.
Stay with us, we'll do our best!
Lucio Cadeddu

Audio dither page
I recently discovered your helpful page on audio dither.
I was curious if you remember what program you used to convert to 4-bit and to apply the dither?
Thank you for your help,
Paul - E-mail: paulscourtney1 (at)

Dear Paul,
that article was written by our Werner Ogiers, so you should try to contact him directly. It's been a long time since the last time I heard from him. I'm not 100% sure he still reads his TNT-Audio mail on a regular basis, you can try reaching him via Linkedin or other media.
Hope this helped somehow,
Lucio Cadeddu

Hammer Dynamics evolution experiments
Dear Mark,
I just read once more, an old review of yours of the bullet tweeter and horn loaded compression driver from B&C.
I have a pair of Hammer Dynamics loudspeakers and being fed up with the driver beaming at medium-high frequencies, I am thinking of discarding the Audax tweeter, buying a 1" compression driver with horn, probably Beyma or B&C, and cut off the Hammer driver at about 2 or 2.5KHz, connecting the compression driver from there upwards (First order crossover filter).

Since you have made some experiments yourself with the Hammers, from what I read, I kindly ask your opinion on this. I would also appreciate if you would give me any other advice based on your experiments.

I drive the Hammers with a Border Patrol 300B Single Ended amp.
I shall look forward to hearing from you and I thank you in advance for your kind help.
Best Regards,
Vagelis - E-mail: vpanagiotakos (at)

Hi Vagelis,
It is good to hear from you and I imagine you have been hearing some fine sounds from the combination of the Border Patrol 300B SET amplifier and Hammer loudspeakers. The Border Patrol power supply raises the performance of directly heated triodes (DHT) like the 300B and 2A3.

The Hammer Dynamics loudspeakers were designed by the late John Wycroft as a system. Every single aspect of their performance relates to every other specification. Thus, the rather complicated crossover (for a device that claims to have the transparency of a full-range single driver loudspeaker), interacts with the dimensions of the sharp edged cabinet (and the diffraction effects this produces). The very strange bass loading and tuning arrangement, that relies on energy being converted to heat by bubble-wrap instead of acetate fibre stuffing, also interacts with the internal and external dimensions of the cabinet. As it states on the Hammer website, any deviations from the standard design on construction becomes your design and not his.

You have decided that the Audax tweeter needs to be replaced. Many have made a similar choice before you and there are numerous suggestions on web forums, with crossover modifications. I made the same decision to replace the soft-dome as soon as I was sure that the system had properly bedded in.

However, you also mention dispersion and beaming being a problem. The Audax tweeter has much wider dispersion at the crossover point than the big Hammer 305mm driver with its 250mm cone and 125mm whizzer parasitic inner cone. Using a horn loaded driver will control the high-frequency dispersion more accurately. This will enable you to match the dispersion in the crossover region. This will help you achieve a more even in-room power response than before, because the different dispersion of the big driver and the small tweeter results in more early reflections above 7kHz (the hammer nominal crossover frequency, although there is more overlap than usual) than below 7kHz. In my review I noted that the DE35-8 bullet tweeter had tighter controlled dispersion than the DE400TN-8 compression driver and matched the dispersion of the Hammer bass-midrange driver better. The bullet tweeter was also coarser sounding than the DE400N compression driver, but neither were as inaccurate as the series of controlled resonances that make up the response of all soft-dome direct radiators. The bullet tweeter dispersion was consistently narrower than the DE400N and would therefore contradict your desire for wider dispersion. Wide dispersion usually requires multi-way loudspeakers with small cones and narrow cabinets, especially in the mid-range. If you need wide dispersion in the mid-range you might be better building a complete new system with smaller drivers in a D'Appolito M-T-M configuration. These use one of the serendipitous qualities of third order (18dB/8ve) filters to create the most even sound-field possible with direct radiator drivers.

One way of thinking about avoiding hot spots in the listening room is by loudspeaker placement and orientation. Establish the zones of neutrality using well-known procedures like WASP described in these pages almost 20 years ago. Position the loudspeakers there, but not yet spiked into the floor. Then use the theories of Ted Jordan, described in the early 70's by John Atkinson in a HiFi News & Record Review artcle 'Broadenning the Stereo Seat'. Choose a recording with an excellent sound-stage that you can tolerate hearing many times.

Begin with the loudspeakers' axes crossing in front of you about 1/3 of the distance between your seat and the baseline between the loudspeakers. If there is a hole in the middle of the sound-stage move the speakers nearer to each other. If there is a big block of mono, move the loudspeakers further apart.Move yourself to the left and to the right until the sound changes and the stereo image distorts. If the image seems to shift toward the further loudspeaker, change the loudspeaker axes crossing to be nearer your seat but still in fron of it and repeat the exercise.

If the image seems to move towards the nearer loudspeaker as you move, try crossing the axes closer to the baseline. This technique expands the number of positions where a reasonable stereo image is possible, but at the expense of the best sound-stage. The best sound-stage is always sitting at the apex of an eqilateral triangle between the loudspeakers. Once the best loudspeaker angle has been established, experiment again with the distance apart, within the zone of neutrality.

If it is not possible to achieve what you desire with your Hammer loudspeakers using this technique, consider either changing your loudspeakers or accepting that the hot seat is always going to be the best. In that case we must consider new tweeters (those Audax are horrible). Either the DE400N-8 or the DE35-8 are good enough for me, even though I actually prefer the vintage ESS Heil Air Motion Transformer and 'active crossovers' between two triode amplifiers. With the passive crossovers that Hammer specify, the B&C are so much more sensitive than the Audax the the series resistors needed to compensate also render the load impedence mostly resistive.

If you are going to lower the crossover point to 1.8kHz, a steeper crossover slope is needed. Also you are now defeating the object of the Hammer's extended (for a 305mm driver) high frequency response and you might as well find other more accurate bass drivers. With other more accurate bass drivers (with cast aluminium frames rather than ringing steel chassis) you can build a more conventional cabinet with less cabinet resonance and better bracing. In other words, if you like the sound of the Hammer dynamics keep them and upgrade the tweeters and rebuild the crossovers with litz inductors. If you want to change the crossover frequency, it would be better to start again with a new high-sensitivity design. With the Border Patrol amplifiers, and well controlled dispersion required, pairs of BIG bass-midrange drivers (B&C make these too) on open baffles might be the best solution.

This is probably not what you wanted to read, but we pride ourselves on being independent and impartial. You now have some big decisions to make,
Happy building,
Mark Wheeler

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