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Hi from Italy! Quest for Rectilinear XIa/XIb proper replacement


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Dear Friends,

I've been doing a lot of research about a pair of speakers I got from mom, a pair of Rectilinear Research XIb. While doing so I stumbled upon Mr. Kent Xla restoration project on this forum's section and I thought it would be useful to ask about my speakers as well.

While inspecting my set, after removing the front grille I realized that the tweeters were replaced with a pair of Philips AD 0160 T8 Mylar dome super tweeters. I was shocked to say the least. My purpose here is to find a proper replacement for these speakers and restore them to the original factory settings.

I still have the original documents of the speakers, Warranty cards from Rectilinear and product guide, but I couldn't find the exact part number and manufacturer of the tweeters. However, I was able to recover information about the technical specs of the drivers as follows:

  • Original replacement part name: T-II (used only on XIa and XIb)
  • 3.5" paper cone tweeter
  • 8 Ohm impedance ferrite driver
  • Large 0,5625 inches voice coil
  • Approx. weight 0.5 Kg
  • Range from 2000 Hz to 20,000 Hz
  • Crossover Filter Frequency: 2000 Hz
  • Total flux density: 11,000 gauss or better

What I cannot be sure about is if it's supposed do be made by Peerless, and if its power absorption should be 40W or 50W.

Would you mind me to ask you, from your experience, what could be the best replacement for the tweeters or point me towards a good place to look for it? I think I found something that matches the right characteristics, but I can't be sure about that or how do they sound compared to the originals, that would be the Goldwood GT-25, 3.5" paper cone tweeter ( https://www.goldwood.com/goldwood-sound-gt-25-black-3-5-kapton-tweeter-80-watt-8ohm-replacement-tweeter/ ). Of course my first pick would be to find the original tweeters, leaving the Goldwood options only as last resource.

Another technical question: The XIb is supposed to be a bass reflex design, as you can see there is still the original wool material inside the bass conduct, but I am not sure that is the right placement, should it be pushed far back in the cabinet to allow a better air flow?

Really hope you could help with this project, all the bests!










Edited by jacobhall
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  • 2 weeks later...

You might think twice before replacing your Philips tweeter. It's a better-sounding unit than the Peerless it replaced. You have a tweeter level control which should enable you to tone it down if need be. The original Peerless units are not hard to find as they were used in many different speaker systems from different brands.  Many Rectilinear models used them, but many are severely mangled because of the tenacious adhesive that Rectilinear used to install them.  

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Hi Martin,

Thank you for your precious info. Is it possible the tweeters you are talking about are the phenolic type? The ones installed on the XIa and XIb were one of a kind and different from all the other tweeters that were installed in other Rectilinear models, probably because of the very low cross over frequency (1800 and 2000 Hz respectively). The tweeters matching all the characteristics of the original T-IIs are the Goldwood GT-25 (3.5') (link above), do you have any idea about how they sound or compare to the original or the Philips actually installed?


Thank you very much for your feedback!


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I have owned multiple pairs of XI & XIa & XIb in the past and I agree, the XI line were surprisingly high quality speaker systems, very competive with KLH 17 & AR 4x.

The original cone tweeters were fine and perfectly adequate, but truly, they were nothing special and IMO, the Philips replacements you already have are superior to what was in there originally.  They are also superior to the common, modern, cheap, paper cone tweeters available now.  Rectilinear used several different tweeters, including the phenolic type, in the XI, XIa & XIb. Most of them used a simple, black paper cone, not the phenolic--I can't remember which model used which tweeter. 

Your Philips are a very versatile tweeter that was widely used in many 2- and 3-way speakers from the early 1970s, most of which were rather higher-end than the XIa & b. I can recall several models from B&O, Avid, Philips & others that used the 0160 to good effect. They were also popular as a DIY tweeter for speaker builders and that is how I became familiar with them at first.  I remember buying a new pair of them for around $25 in the mid-'70s.  Their ability to reproduce & handle 2000 Hz should equal the capability of the originals, so non ti preoccupare!  There is no problem. 

Do you have XIa or XIb? I'm not sure that your pictures match your comments about which model you have. Keep in mind that Rectiliinear's crossover point supposedly did vary from 1000 Hz to 2000 Hz, depending upon the specific XI model. So 1000 Hz is probably a bit low for the 0160, 1800 or 2000 Hz is of no concern at all, but in the end, my past experience tells me it doesn't matter as it is a fairly heavy-duty unit. 

So, if you're not too concerned about preserving originality and care only about how good they sound, I think you can leave them in place. Your tweeter level control will allow you to adjust them to your liking.  If you insist on changing the tweeters,  I think several of us can help you pick a replacement. 

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  • 2 weeks later...

Dear Martin,


Thank you so much for your thorough explanation! I am absolutely positive that I have XIb (even though the plate on the back of the cabinet says otherwise), since I have the original purchase documents and also the receipt from the NATO repair shop that repaired them once in 1976.

As far as for the sound, I think they already sounds fabulous as they are, I managed to restore one of the front grille (left) and enjoying them a lot, I power them with a SAMSON Servo 120a, the signal feed comes from an analog mixer (in the picture YAMAHA MX12/4 to be replaced with Allen&Heath Zed R16 once the desk is ready).

Thank you again for the time and advice, Ibwill share a pic of the studio when ready!





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