Last week I had a very special experience. Multi-site speaker development! Bruno Putzeys borrowed some Altec speakers from a friend. It contains an Altec 421-8H woofer in a cabinet, and the horn on top is an RCF N481 unit inside an Altec 511 horn enclosure. The goal of the speaker development was to do a one-day attempt to make a speaker for the Triode Festival, together with Guido Tent and Peter van Vegchel. The constraints of the owner were summarized by the sentence "surprise me".

Unfortunately I was recovering from a cold, and as Buno lives 1.5 hours driving from my place I couldn't join the team. Therefore we've decided to send measurements to my place via e-mail, and I would develop the speaker off-site, trusting the observations of the people on the spot! First, the speaker was heavily mechanically modified, as there were a lot of prominent panel vibrations. After that, Peter performed some measurements, and sent me the files, and I tried to develop a filter (based on 2nd-order acoustic Linkwitz-Riley response). After 3 hours of iteration, the speakers were transported to Eindhoven, to Guido's place.

The next day I was able to re-measured the units, and found some difference in phase. I re-did the design. For those who are interested, the filter and the characteristics are shown below. The circuit is a simple 2nd-order crossover, with some attenuation to align the efficiency of the units.



The response shows a lot of peaks and dips, which is part of the intrinsic characteristics of the units. The horn and cabinet have a lot of panels, which reflect and diffract, causing these peaks and dips. The first 12 dB, the response follows a Linkwitz-Riley characteristic, and after that the units are filtered very steep, meaning they hardly have acoustic overlap outside their crossover region (at about 600-700Hz). I suspect this to be a good idea with units that have such a different off-axis response due to their enclosures. As the horn is a bit prominent, we've attenuated it a bit more than flat on-axis.



The acoustic phase response shows the Linkwitz-Riley characteristic of the filter even better.



The impedance is tube-amplifier friendly, which is a necessity for a Triode Festival.



The measured response:



The high-end built of the prototype:



I must say I'm pleasantly surprised about the final result. Where in the beginning the whole sounded thin, the overall result is very live-like and homogeneous. It doesn't have the transparency and imaging capabilities of a high-end speaker, and treble is not "airy", but its timbre is very musical and enjoyable, and makes the music very involving. I could happily live with this type of sound at home (but not with the form factor!). All 'n' all this was a very funny project to do, with a surprising outcome. I'm curious about the reaction of the owner.

I've applied better components, some minor tweaks, and tried to describe the sonic properties. (read more...)

A new filter has been made with a higher order filter between the midrange and tweeter. This is getting very close to the end result I want! (read more...)

Finally! After months of time, me and Korneel had sufficient time to construct and listen to Jon Marh's filter. How does it sound? (read more...)

Last week, I moved around the speakers in the room, with some interesting observations (read more...).

A rainy week, some inspiration, and some crocodile clamps brought a new idea. Flat response, phase aligned, and the timbre I was looking for! (read more...)

Due to a small simulation error, I tweaked a little bit more. (read more...)

Some tweaking to Okke's filter has resulted in more authority! (read more...)

A new Okke filter has been constructed. Impressive results! (read more...)

I just received back my Ayre CX-7 and AX-7, that have been fixed (skipping CD player, buzzing transformer in the amplifier) and upgraded with the so-called evolution version. Reports from Ayre, but also from Stereophile (see their AX-7 and CX-7 review) report significant improvements. So I gave it a try.

The price reported by Ayre is US$300 for the CD player, and US$250 for the amplifier (including labour costs). Because the upgrade needs to take place at the Dutch distributor Audiac, shipment costs and taxes are added (550 euros), but subsequently additional labour costs are accounted for. I understand that each party wants to earn some money, people have to make a living out of this, but each party asking for the full-range price brings the total to about 1000 euros (or 1250 dollars), which is more than twice as expensive!!! Luckily the dealer, Remkes, who was the intermediate for shipment didn't charge me anything additionally, besides some marginal shipping costs of 18 euros (good service)! I think Ayre should consider to offer the upgrade for a similar price in Europe, the difference with the US is just too high.

From a technical point of view, Charles Hansen (the founder of Ayre) says the following on the Audio Asylum forum: "The main change is a new power supply technology we call Dynamic Power that includes newly developed circuitry to increase instantaneous current delivery, reduce mains-born RF interference, and eliminate residual switching noise from the rectifiers themselves." In the same forum, Charles describes the improvements as: "In audiophile terms: increased resolution, lowered apparent "noise" level (blacker background), improved high frequency extension and "sweetness", more articulate low frequencies. In musical enjoyment: more realistic, more compelling, more involving".

My own observations are in line with Charles' description. There is indeed quite more involvement. It is difficult to pin-point exactly where this involvement originates from, but many things seem to have changed. Sound sources are better separated, the spatial image is more holographic, treble is a bit more silky (though certainly not soft), bass is more punchy and direct, and there is a better sense of texture. The sound comes closer to what I appreciate from a good tube amplifier. It seems to share a significant amount of involvement, drama, speed, and transparency, combined with a big sense of authority. It is capable of communicating the introvert character of music very well, by means of something I often call "silence between the notes". A tone normally has a decay to full silence, there should be no stress that eliminates the floor of silence underneath the musical performance. I guess this is what Charles calls a "blacker background".

Normally, this phenomenon is only apparent with good tube amplifiers. These tube amplifiers are capable of combining a black background without sacrificing transparency and texture, something I rarely hear with solid-state based amplifiers, and thumbs up for Ayre in this case. One point where a good tube amplifier seems to outperform the Ayre is texture. With treble intensive material, the Ayre has a slight veil of treble with for instance voices, making the sound a bit "zizzy", affecting the texture or small-scale dynamics. But this is a phenomenon that all solid-state amplifiers seem to suffer from, and here the Ayre is on the positive side of the edge. Concluding, this is the first amp that combines the airy sound of tubes with the speed and push of solid state. It has my clear preference, and direct comparison with a 300B SE showed superior performance of the Ayre.

I'm very satisfied with the quality of the upgrade! I very much appreciate that Ayre offers their upgrades to their existing customer base. In my opinion, the upgrade needs some price compensation for European customers though. Nevertheless, strongly recommended! This is a killer product, with an incredible value/price ratio!

"Filterdrops keep falling on my head". Many filters designed by various people are waiting for construction and evaluation! There is a lot of interesting stuff coming in the next few weeks. Stay tuned! (read more...)

Based on the anechoic curves, Okke Ouweltjes constructed a new filter. A big step forward! (read more...)

Anechoic measurements of the Milestones speakers have been made! This allows us to design filter with better accuracy (read more...)

Paul Vancluysen constructed a parallel filter with nice sound characteristics (read more...)

In the past weeks, I've developed some new Milestones filters. The main target was to get a flat response from the midrange unit from say 300Hz to 3kHz. Compared to the previous versions, this filter has a huge spatial image, more drive in the bass, more body in the fundamentals, and a very dynamic life-like sound. A big step forward!!! I'm pretty satisfied now, and will lower the pace on filter design in the coming weeks. (read more...)

Since the 10th of February, the Milestones are playing in our living room! First impressions are great! The challenge of designing a crossover filter starts. (read more...)

On May the 20th in 2004, the Milestones project has started! (read more...)