Troels ATR

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has anyone had anything to do with this kit? i can find no reviews but would like to hear if anyone thinks it's worth the amazing price. zaph's tests didn't make it sound like a much better choice than the usher 8945p or the scan revelator but maybe listening test will reveal something.
Being "worth the amazing price" is largely a matter of affordability - if it's comfortable for your budget it may indeed be; if it's a stretch you may want to consider alternatives.

Being of the most-bang-for-the-buck crowd, I'd look at Jay_WJs 8945P designs or perhaps Zaph's ZD5.
i agree, softdome. i am preparing to build a set of the 8945's myself. as far as affordability, i don't mind paying more to get more, but nobody can tell me if these drivers actually provide more than an usher or revelator and i don't feel like paying more just because they cost more. i could buy retail to do that. somone mentioned one time that it would be great if a supplier would have a demo program, buy three sets of drivers- build three desings-and send back the two you didn't like. oh to dream!
diyAudio Member
Joined 2004
When you get into drivers such as the Revelator, Usher and AT then there's nothing bad about the performance, instead its usually average at worst up to class leading depending on the performance aspect your looking at.

I think what it would come down to more than anything is the work done in the crossover and how good the tonal balance and mating between drivers is. Its easy to isolate the individual units to assess performance but the real test is a run out with the loudspeaker system as a whole so you can see how they present the music and if that agrees with you. I think all competent implementations using any of these drivers would offer something agreeable but with their own unique colourations.

BTW As far as value goes, I don't see much in the way of a clear winner without hearing them first. But since its unlikely you'll get these designs side by side in your listening room then the Usher would be a good safe bet if your value for money conscious.
I hope I am not steering too far off topic with my question.

Reading through the two designs by Troels (ATR25) and John's (ZRT 2.5-way) there are similarities and differences that stand out.

Their crossover topologies are similar but Troels decided to go with a TL cabinet and John chose dual ports. Can someone please outline the pros and cons of each approach?

Immediately, I would prefer the TL arrangement. It seems John always has the end user in mind and realizes adding ports to pre-made cabinets is easier than modifying the inside.

To get the optimum bass extension from the ZRT 2.5-way design the builder would need to build their own cabinet. Would you guys suggest building a TL cabinet (if one wanted to redesign from ground up) or is there little to gain with the TL addition?

Lastly, John's measurements always look great! Could someone please explain differences in measurement methodology between John and Troels that might explain why Troels FR for his ATR25 has more ripple?

Thank you

The short answer regarding TL's and vented :

An optimised TL is usually bigger than a vented cabinet.
TL's can have ripple and extend deeper then vented.
Given that vented can be tuned low for overdamped.
TL's damped to reduce ripple can end up with less bass.

Most designs can be TL'd or MLTL'd if you are so inclined.
It is a trivial task to build the ATR 2.5 way in a vented box.

Box type choice is not inherent in most designs.
Vented, sealed, TL are all possible.

What sort of TL complicates the ZRT 2.5way question.
see :

Differences among these designs are not only in different drivers. Crossover design plays a bigger role in making their differences in tonal balance. These midbass drivers (AT, SS & Usher) all have very nice, low-distortion motors. But the designers have different voicing preferences. Zaph prefers to use full BSC if the midbass has low enough bass distortions. Troels' preference is the opposite. He rarely uses full BSC. My preferred tonal balance is in-between. Here's an interesting comparison of the three designs. Below are these designs' low-pass transfer functions:

An externally hosted image should be here but it was not working when we last tested it.

Considering the fact that any of these three drivers don't exhibit a unique shelving response in the 100 Hz to 1 kHz range, the use of each crossover's electrical transfer function makes a valid comparison possible.

As you can see, no doubt zaph's crossover uses full BSC. Mine has about 5 dB BSC. Troels' uses at most 3.5 to 4 dB BSC.

This means that Zaph's design will sound very different from Troels'. Not because of the use of different drivers but mainly because of the designers' choice of BSC. Zaph's reduced BSC option will make its midrange tonal balance somewhat between mine and Troels'.

All these designs are top notch, high-end 2-ways based on a 7" midbass driver, if your biggest decision factor is performance. All should have very low system nonlinear distortions. But you also need to consider your preferred tonal. If your decision also depends on the price, one thing I can say is that my Usher 2-way design can achieve this at less than half the costs of the others. ;)


P.S. A person at PE TT board is finishing a 2.5-way version of my Usher design in a TL tower cabinet (yet to be published at my website).

One thing is certain IMO in the VFM stakes :
1) Jay's Usher, 2) Zaph's ZRT, 3) Troel's ATR.

As Jay has pointed out there are tonal differences in the designs.
Another way of looking at them is e.g. the ATR's treble range is
elevated by 2.5dB compared to the ZRT via a tilt in the midrange.

1) Has nearly the best drivers available at reasonable cost
2) Has the best drivers available
3) Has expensive drivers

All of them could be balanced to be more like the others.
Balance is the most immediately obvious difference between
similar good speakers, if 3) suits you and your system you
may be not so happy with 2) or 3). Conversely ....

Great responses Jay and Sreten, thank you.

A major difference between Troels' design and the other two is that he is not using a dome tweeter. If Troels added 6 dB of BSC would he not have problems with the integration between the woofer and the tweeter? I'm not quite sure how low that Raidho tweeter can play.

Jay, how far along is the 2.5-way TL Usher design?

It depends on the overall balance of the system, speaker placement
and personal preference. Many budget speakers do not have it and
the owners are non the wiser.

Fine tuning the level of BSC is alsop related to the drivers distortion
profile affecting its apparent "tonality". When you get to this point
though IMO you are tuning something you can easily live with.

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