Some notes on the "Pink" Cafe Sound Speakers with Design by Eylin

After moving into Reno Listening Room last year, I decided to build a larger system based on 300hz horns and dual woofers. My original intention was to use the cabinets which we eventually installed at Shibuya HiFi in Seattle.

I’ve been experimenting with 300hz Altec horns for over a year with reasonably good results. I felt the presence the larger horn provided could be beneficial in larger, more active rooms. Also by using a 300hz horn, a lower crossover point to the mid-woofers could be used, keeping more of the critical mid-range in the horn itself. The drawback is that using a tweeter or supertweeter isn’t optional.

300hz horns also requires a compression driver capable of lower frequencies. The traditional Altec choice is the 291 (which rolls off above 10khz), but there are modern alternatives which can be used as well, which is the route we went in this design. We used a custom throat to adapt the 300hz Altec horn to a 4 bolt driver.

Matching modern woofers to horn speakers is a challenge as there are few drivers on the market which meet the original 416/515 specifications. Also the horns tend to have far high output than woofers, with multiple ways to remedy this. Including:

  • Horn loading the woofers
  • Using multiple woofers
  • Attenuating the horn with a l-pad, transformer, or resistor

In this case we used a mostly traditional Altec cabinet design of new construction which uses 2 woofers per cabinet in a horn loaded enclosure. We combined this with modern, hand-made, high efficiency woofers which are a relatively close match to the 416.

Surprisingly by using two 8 ohm woofers in parallel with a 16ohm compression driver we were able to get a close match with very little horn attenuation. This is the best performance we’ve seen from a modern driver, but unfortunately these drivers a difficult to source, so the hunt for a standard woofer for our designs continues.

Overall the system delivers as expected including a high degree of efficiency. The crossover design is fairly simple and takes advantage of the acoustic rolloff of the drivers. We’ve found with high efficiency horn designs that simpler crossovers tend to sound better than more complex design – for instance 3rd order crossovers with notch filters, etc. We’ve tried a bunch of designs over the past year, but keep coming back to the less is more philosophy.

In the current configuration we use the super woofer at a very low frequency, filtering it at a surprisingly low 35hz. In this configuration the system has excellent bass performance with a bit of mid-bass kick which I think is expected from larger commercial systems.

In listening tests, I and others noted a wide and near holographic sound stage from the vintage Altec horns. This experience is nearly impossible to replicate with a typical direct radiating speakers. While the crossover points could benefit from a bit more tweaking, overall we feel this system attains its goal of filling a large room with high quality output at potentially higher SPL levels.