Around 1980 a couple of things happened:
1. Toby Speakers in Fort Worth gave away plans to their Toby 2.4 sort-of transmission line speakers and I've been moderately obsessed with t-lines ever since. Nearly everyone in woodshop class built a pair and I built a set at home.
2. I heard my first pair of Time Window 1's. I wasn't really paying attention to them until we (the audio engineering club at Texas A&M) hosted a seminar in a good-sized conference room. I was setting up a display when I noticed the amazing imaging. I looked up and saw that I was pretty far left of the left speaker!
All these years later I'm thinking of buying a used pair, just to see how they did it. I can't find a schematic for the crossover and there aren't any pictures of how the transmission line's set up. I found a schematic to a Time Frame speaker and have some idea about the crossover.
So here's my question, and an attempt to provide some comic relief these days. Try not to laugh to hard, but..
Have any DIYer's tried to build something that mimics what these did, but a completely new build with modern components? 6.5" woofers can reach further down than they did before, so a t-line may not be necessary. Metal domes didn't come around for another 15 years or so, and ribbons...OK, maybe I'm in over my head! This is pretty ambitious, to be sure.
1. Toby Speakers in Fort Worth gave away plans to their Toby 2.4 sort-of transmission line speakers and I've been moderately obsessed with t-lines ever since. Nearly everyone in woodshop class built a pair and I built a set at home.
2. I heard my first pair of Time Window 1's. I wasn't really paying attention to them until we (the audio engineering club at Texas A&M) hosted a seminar in a good-sized conference room. I was setting up a display when I noticed the amazing imaging. I looked up and saw that I was pretty far left of the left speaker!
All these years later I'm thinking of buying a used pair, just to see how they did it. I can't find a schematic for the crossover and there aren't any pictures of how the transmission line's set up. I found a schematic to a Time Frame speaker and have some idea about the crossover.
So here's my question, and an attempt to provide some comic relief these days. Try not to laugh to hard, but..
Have any DIYer's tried to build something that mimics what these did, but a completely new build with modern components? 6.5" woofers can reach further down than they did before, so a t-line may not be necessary. Metal domes didn't come around for another 15 years or so, and ribbons...OK, maybe I'm in over my head! This is pretty ambitious, to be sure.
I own a pair of Windows, and have another pair to refoam for a friend. I have worked on a lot of DCM speakers over the years, and the Time Frame is a very different animal. It doesn't matter anyway, with new drivers you will need a completely new crossover.
You will need to restore the originals and measure , to see what was happening at various angles(this is what would make them different).
One of the best things about the Windows is the half-tube fiberboard rear of the enclosures, very dead, very light. Twin ports at differing heights have a theoretical advantage in what we now would call a mass loaded transmission line.
Basically, when your ported enclosure gets long enough to have quarter wave resonance, you tune it differently(or stuff the heck out of the bottom third of the enclosure to damp the resonance).
As for baffle step correction, the Windows have a good bit. They are meant to be out in the room, you can adjust to needs and taste. They do fill the room a bit like Allison Ones, as you might expect from the driver layout. But more flexible as to placement.
If you restore an original pair, be sure to change the ferrofluid in the tweeters first, those old Philips tweeters will commit suicide trying to move with thick or seized fluid.
A fun project, see how reasonably you can get a pair for reference. Enough people love these old things that you would have no trouble selling them when you are happy with the new version.
You will need to restore the originals and measure , to see what was happening at various angles(this is what would make them different).
One of the best things about the Windows is the half-tube fiberboard rear of the enclosures, very dead, very light. Twin ports at differing heights have a theoretical advantage in what we now would call a mass loaded transmission line.
Basically, when your ported enclosure gets long enough to have quarter wave resonance, you tune it differently(or stuff the heck out of the bottom third of the enclosure to damp the resonance).
As for baffle step correction, the Windows have a good bit. They are meant to be out in the room, you can adjust to needs and taste. They do fill the room a bit like Allison Ones, as you might expect from the driver layout. But more flexible as to placement.
If you restore an original pair, be sure to change the ferrofluid in the tweeters first, those old Philips tweeters will commit suicide trying to move with thick or seized fluid.
A fun project, see how reasonably you can get a pair for reference. Enough people love these old things that you would have no trouble selling them when you are happy with the new version.
Thank you! I have a pair I'm looking a that apparently have been for sale for at least a month. Clearly, no one knows our little secret!
Speaking of secrets, how do you remove the foot? Is it just glued on, and I have to pry it off?
As I said, I'm somewhat obsessed with t-lines. But these seem too small for a t-line, especially for 2 woofers and 35Hz low end. Could it be just a baffle to kill any resonant frequencies between the top and bottom?
Speaking of secrets, how do you remove the foot? Is it just glued on, and I have to pry it off?
As I said, I'm somewhat obsessed with t-lines. But these seem too small for a t-line, especially for 2 woofers and 35Hz low end. Could it be just a baffle to kill any resonant frequencies between the top and bottom?
FWIW, while there may be “nothing new under sun” since those halcyon days of the early 80’s, thanks to folks like Martin King, there are newer tools available now widely available to commercial designers and enthusiasts to assist in the understanding, modeling and design of MLTL enclosures -rather than what might have seemed serendipitous, our unintentional back in the day.
The TimeWindows were certainly an almost giant killer, but even back then there were folks more comfortable with the rectilinear monkey-coffins by brands such as Boston, Advent, EPI, etc. It was probably the long term fatigue from the Phillips tweeter, and the fact that they tended to be demoed at 11” on Nigel’s scale that got to me. I much preferred the A150 for louder classic rock, and the Spica SC50 for serious listening, with some help in the bottom end.
The TimeWindows were certainly an almost giant killer, but even back then there were folks more comfortable with the rectilinear monkey-coffins by brands such as Boston, Advent, EPI, etc. It was probably the long term fatigue from the Phillips tweeter, and the fact that they tended to be demoed at 11” on Nigel’s scale that got to me. I much preferred the A150 for louder classic rock, and the Spica SC50 for serious listening, with some help in the bottom end.
I've looked over Martin J. King's site and tried to go through the derivations but it was a little over my head at the time. I can't afford MathCAD (and the demo version doesn't seem to be available anymore). I was a big fan of Boston Acoustics at that time and had friends with the A100's and A150's, as well as BIC when they had the venturi (and did actual engineering).
Experimenting to get the transmission line right must have been a pain back then!
I'm still waiting for ribbon- and other kinds of tweeters to mature or go down in price.
Experimenting to get the transmission line right must have been a pain back then!
I'm still waiting for ribbon- and other kinds of tweeters to mature or go down in price.
Well, this morning the light hit the one I have open in the living room, and it's upside down, so it's the bottom that comes off. It's in the corner out of the way, and the crossover hides the hole in the plate. When I lifted the plate I see the lower of the ports.
I guess I should calculate the effect of the different port heights, if any. They already had the 'no parallel walls' thing going.
I guess I should calculate the effect of the different port heights, if any. They already had the 'no parallel walls' thing going.
Not as such. Three different drivers were used in the dozen or so pairs I have seen (as woofers).
One Philips polygonal shaped, two round. For tweeters, I have seen three Philips and one that looked like a Peerless.
So. You will have to get them out and identify them, or resign yourself to a new crossover(the crossovers changed with the drivers in significant ways).
The woofers can be refoamed in place, if that is your problem. Removing them can be difficult. A halogen work light,300-500 watts will soften the glue, and machine screws whose threads engage the holes in the woofer frame can be pulled on.
I can measure the TS parameters on mine if you need to see what works in that 'box' with similar tuning, but we will be starting from scratch on a crossover.
It's not easy even over here where they were made. Sorry.
The tweeters should be easier, there are lots of them around, they(and yours) probably need new ferrofluid, though.
One Philips polygonal shaped, two round. For tweeters, I have seen three Philips and one that looked like a Peerless.
So. You will have to get them out and identify them, or resign yourself to a new crossover(the crossovers changed with the drivers in significant ways).
The woofers can be refoamed in place, if that is your problem. Removing them can be difficult. A halogen work light,300-500 watts will soften the glue, and machine screws whose threads engage the holes in the woofer frame can be pulled on.
I can measure the TS parameters on mine if you need to see what works in that 'box' with similar tuning, but we will be starting from scratch on a crossover.
It's not easy even over here where they were made. Sorry.
The tweeters should be easier, there are lots of them around, they(and yours) probably need new ferrofluid, though.
Last edited:
Thank you for your fast reply. I can see it is not as easy as I had imagined. I will take a look inside and get back as soon as I have a better understanding of what needs to be done. I wasn't aware that the tweeter contains ferrofluid. I thought this was not used back then and not in what after all was relative cheap speakers.
Ferrofluid was arriving about then, Dynaudio was a pioneer, but I don't recall the original Phillips domes claiming to use it. I have a newer cheaper pair with one 6.5 and a 3/4 Vifa. Built out of sturdy 12mm particle board and wrapped in two layers of spandex with genuine oak top and bottom caps, like a flattened Advent.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.