FR125S in TL?

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robertG

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Joined 2005
gemmeaudio.com
#1
OK, these were great on OB, but my room is simply too small. Did anyone tried a TL with these?

I started to read Martin King excellent material on TLs, and got an equally excellent headache... I mean these things are harder to figure out than horns...

So, out of laziness, I'm trying to find something fast, easy and proven.

From what I understand, a properly designed TL will be nicer than any BR, but a badly designed TL will be worse than a bad BR...
 
#2
From a previous post by GM on this driver.....

Greets!

A basic end loaded (Alpha) TL, nice midbass, ~75 Hz aneochoic F3, ergo requires a corner for ~decent bass:

L = 32.03"
CSA = 47.047"^2
stuffing density = ~1.75 lb/ft^3

45 Hz ML-TL, smoothest sim (~+/- 1 dB), but requires either a stand or a mass loading cavity to get the driver to ear height:

L = 39.56"
CSA = 43.68"^2
driver down 14"
vent = 3" dia. x 3" near/at the bottom
stuffing density = ~0.3 lbs/ft^3 from top down ~30"

45 Hz ML-TL, driver at ~ear height (~+/- 2 dB):

L = 39.56"
CSA = 43.68"^2
driver down ~3.3"
vent = 3" dia. x 3" near/at the bottom
stuffing density = ~0.3 lbs/ft^3 from top down ~30"

All dims inside and use stuffing in the bottom portion of the ML-TLs to 'tighen up' the bass to get a better blend in-room if desired.

Anybody builds any of these, please report back.

GM
 
#5
Just on Saturday we got to listen to a number of ML-TLs with FR & WR125s.

A GM ML-TL (driver down 14"), 3 variations on the bipole i designed based on Tim Formans WR TMM, and a shorter Tim Forman bi-pole.

If you are going to port the FR or WR125 (and not make them aperiodic) i suggest a high pass filter to keep any signal from getting to them in the area where they are unloaded -- otherwise they will "fart" when that signal causes them to bottom out.

Our feeling after the event is that one should avoid tuning these too low (ie the GM pipes are going under the saw to become shorter, and the tuning will be raised.

dave
 
#7
planet10 said:
3 variations on the bipole
Click to expand...

Has anyone tried a WR125ST (16-ohm) as the rear driver in a bipole? I'm thinking it might give some of the benefits of a bipole and lessen the bipole effect (not as focused as a front-firing system?).

I just took delivery of a pair of FR125S's yesterday and plopped them in my RAW-1F in place of the WR125S's. Wow! Quite the improvement. I also played around with my Marchand XM44 crossover for the first time in comparison to no crossover (FR125 running full range in a 7L aperiodic cab, with dual subs at 100HZ). In the past I've only compared the Marchand to passive crossovers, and it always won easily. But compared to no crossover, it's clearly compromising my Meitner amps. So I've suddenly become highly interested in this bipole idea.
 
#8
tcpip said:
Where does one find some specs of these drivers? I went to the page for the WR125 on the Creative Sound site but there were no specs at all. Are these metal-cone?
Click to expand...

They're paper cones. The specs are on the CSS site, but I couldn't find them, even though I knew they were there. I had to Google for them. (Are you listening, Bob Reimer?) 🙂

http://www.creativesound.ca/pdf/wr125-dimensions.pdf

tcpip said:
And these WR drivers should be very good as wide-range mids in 3-ways, shouldn't they?
Click to expand...

Oh yeah! They have very good resolution, they allow you to use shallow slopes and wide XO points, and they don't need a notch filter. All good things IMO.
 
#10
audiobomber said:
Has anyone tried a WR125ST (16-ohm) as the rear driver in a bipole? I'm thinking it might give some of the benefits of a bipole and lessen the bipole effect (not as focused as a front-firing system?).
Click to expand...

Bob suggested that really early on to me. I don't know that anyone has tried it yet. It should work to decrease the amount of baffle step compensation. One could go a step further and make a triangle (or pentangon or hexagon) shaped column and load 2 STs on the back.

dave

PS: the spec sheet is also on my planet10-hifi site
 
#12
planet10 said:
If you are going to port the FR or WR125 (and not make them aperiodic) i suggest a high pass filter to keep any signal from getting to them in the area where they are unloaded -- otherwise they will "fart" when that signal causes them to bottom out.

Our feeling after the event is that one should avoid tuning these too low (ie the GM pipes are going under the saw to become shorter, and the tuning will be raised.

dave
Click to expand...

Greets!

Not surprised since they apparently don't have a typical FR's rising rate suspension and low enough efficiency to tend to overdrive them, but I fail to see why shortening them/tuning them higher helps since all this does is unload them higher up, forcing XOing to a sub instead of just a 'rumble' filter to roll them off below Fb.

Also, this raises them into an underdamped alignment unless they are made aperiodic, which FWIW I prefer to sealed to keep thermal power compression low while negating the need for a high pass XO, so I'd rather damp the vent of the full size ML-TL than put it in a smaller cab.

GM
 
#13
GM said:
Also, this raises them into an underdamped alignment unless they are made aperiodic, which FWIW I prefer to sealed to keep thermal power compression low while negating the need for a high pass XO, so I'd rather damp the vent of the full size ML-TL than put it in a smaller cab.
Click to expand...

We ended up stuffing the ports of all the WR/FR boxes to push them toward aperiodic. The shorter lines seemed to work better even after.

I'm going to be concentrating on aperiodic designs as we move forward -- i will also rig up a high pass filter & see how that works out.

dave
 
#15
planet10 said:


We ended up stuffing the ports of all the WR/FR boxes to push them toward aperiodic. The shorter lines seemed to work better even after.

I'm going to be concentrating on aperiodic designs as we move forward -- i will also rig up a high pass filter & see how that works out.

dave
Click to expand...

Greets!

That's surprising! I guess it's a consequence of a relatively 'stiff' suspension (small Vas) since I didn't find this to be true with what we now call 'vintage' drivers.

Alpha TL tuned to 1.4142*Fs then?

GM
 
#18
audiobomber said:
They're paper cones. The specs are on the CSS site, but I couldn't find them, even though I knew they were there. I had to Google for them. (Are you listening, Bob Reimer?) 🙂
Click to expand...
Thanks. 🙂 But guess what? I'd already found the specs (at least some specs) on Dave's site (Planet10) before I saw your posting. I said "some" because those specs only contained drawings, dimensions, and T/S parameters. Not a single line on the construction, technologies, distortion-reducing measures, nothing. For drivers this good, I'd have thought lots of such details would be justified.

Oh yeah! They have very good resolution, they allow you to use shallow slopes and wide XO points, and they don't need a notch filter. All good things IMO.
Click to expand...
Yes, those are very tempting qualities. Two more questions:
  • Will they be as detailed as good hard-cone drivers, assuming that careful notch filtering is done to remove peaks for the hard-cones? I'm thinking of SS carbon-fibre cones or Seas Excels.
  • How do these compare with 6-8" sized Fostex drivers?
Mind you, I'm interested only in using both as wide-range mids in boxed or OB 3-ways, not as FR drivers. Hence, HF distortion in one or other of these above, say, 8K, doesn't concern me if I can get things clean from about 200Hz till 5-6KHz.

I've been toying with using some good FRs as mids for a long time, and I'd have happily used JX92S all the way for such roles if I could afford them. So I'm now looking around for alternatives.

Bob Reimer said:
Apologies, I have added the links with the item. A redesign of the website is planned.
Click to expand...
Can I make a suggestion for your otherwise excellent site? Please can you link each product from their details page to a spec-sheet? At least can you do this for each of your kits and drivers? Currently the detailed pages which come if I traverse after a search just contain one small photo, a one-line description and the price. A link to the detailed specs from here would be really useful.

Just a suggestion, feel free to completely ignore. 😀
 
#19
tcpip said:
Not a single line on the construction, technologies, distortion-reducing measures, nothing. For drivers this good, I'd have thought lots of such details would be justified.
Click to expand...

See the bottom of this page for a couple of papers on Adire's XBL technology: http://adireaudio.com/TechInfo.htm

Will they be as detailed as good hard-cone drivers, assuming that careful notch filtering is done to remove peaks for the hard-cones? I'm thinking of SS carbon-fibre cones or Seas Excels.

I don't have experience with the drivers you mention. I know that some people prefer paper cones and some prefer hard cones, so I guess it depends on your preference. I know that I've used notch filters with my Marchand crossover and IME they mess the sound up. I also dislike 4th-order crossovers, so I would not use a hard cone. YMMV.

How do these compare with 6-8" sized Fostex drivers?

You'll get very poor dispersion from a 6 or 8" cone at 5-6K. The WR125S will be very good from 200 Hz to 5K.

PS I think the SS carbon-fiber cones you reference are actually carbon-impregnated paper cones.
 
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