FR125S in TL?

[audiobomber]

Originally posted by planet10
One could go a step further and make a triangle (or pentangon or hexagon) shaped column and load 2 STs on the back.

Wouldn't two ST's be (3dB?) more sensitive than a single Wr125?

[planet10]

Originally posted by audiobomber
Wouldn't two ST's be (3dB?) more sensitive than a single Wr125?

But -- all wired in parallel -- they only get 1/2 the voltage of the WR. But, i'm guessing someone is just going to have to try it....

dave

[GM]

Originally posted by zobsky



I tried that (though I folded the line) , .. wasn't happy with the bass I was getting (though it is possible that I goofed up )

I was happier with a MLTL (similar to Tim Forman's Rosa) using two WR125s drivers per cabinet.

Thanks GM, for your help

Greets!

You're welcome! No, even with only relatively modest stuffing the sim says it's dying fast below 100 Hz, so strictly a midbass alignment unless corner loaded, somewhat wasting all that Xmax.

Yeah, with such a low efficiency, for sure two drivers are required for all but the most 'intimate' (background and/or nearfield) apps IMO. That, or some sort of horn...........

GM

[Jim Griffin]

Earlier in this thread Dave (and perhaps others) reported issues with ML-TL designs that use the FR125S. I have taken a series of measurements on my version of GM's bipole ML-TL design. A complete disclosure of this design is located at:

http://homepage.mac.com/tlinespeaker...LDesignPak.pdf

I have listened to my speakers for a few weeks now and I've tried material with fairly heavy bass (for example, Keb Mo's recording and others) at levels in the 90-100 dB SPL range. I have not heard the speaker bottom out nor a discernable port noise. I decided to take some data to report on the performance of my speakers.

The attached plot is a measurements of the performance of my speaker taken in room (my garage) at a 1 meter distance. This plot shows room effects and likely a bipole dip in the below 600 Hz area. Hence, I would say that you shouldn't assume that this plot represents the true performance of the speaker below 600 Hz. I'll post a near field measurement in the next posting (Part 2) on this site.

This plot does show that the speaker has a flat frequency response (within +/- 3 dB from 600 Hz to 20,000 Hz).

I'll continue in Part 2.

Jim

[Jim Griffin]

I next measured the frequency response at a distance of 3 inches. At this distance what is plotted is the bipole performance of the speaker but without the any room effects/reflections. This plot has a practical upper limit for accuracy of about 900 Hz so you can ignore data beyond that point. But within the window below 900 Hz, observe that the performance is outstanding--very flat.

In both plots in Parts 1 and 2 the low end of the band does not include output from the port. You can observed in the near field plot that a small dip (the port and driver outputs are 180 out of phase at this dip) occurs in the lower end rolloff skirt near 40 Hz. The dip in the far field plot occurs just above 30 Hz. The acoustical addition of the port measurement to the near and far field plots would fill this dip and extend the low end 3 dB rolloff lower in frequency than observed in these plots. Note that the phase between the port and driver output varies so they don't necessary add dB wise at all frequencies. For instance, the near field plot rolls off 3 dB or so at 65 Hz but in reality the low end would extend below that point if output from the port was included in the plot. My listening would indicate that these speakers approach GM's calculated 3 dB at 45 Hz.

Once you integrate the data between the far and near field plots as I suggested, the performance of my speakers shows to be very flat over the entire frequency band. I don't see issues in their bass response response with their current length of 40 inches. While others have suggested that the ML-TL line length should be shortened or the port stuffed, I'm not in that camp. I think that this design is near optimum with the current parameters. While room effects and stuffing can be changed and these changes would influence their in-room performance.

Jim

[chrisb]

Jim, my experience differs as far as bottoming these drivers out is concerned: on both the bipole MLTL and Dave's mini-Onken, and with every amp I've tried, there's one track that does it every time at any volume level above 80db.

Patricia Barber: Modern Cool "Post Modern Blues" (the "Bill Gates" lyric is just Ms B being, well, Ms B) AFAIK, this track was not intentionally designed at a torture test, but has certainly proven to be.


This recording does not have the same effect on Fostex FE127 in very similar bipole MLTL configuration. While up to the overload point, the FR125 maintains a clear superiority in terms of low end weight and extension, it never quite catches up to the midrange of the FE127 ; and don't get me started about the FE108E Sigma - but that's another story,


We've somewhat tamed this by stuffing the ports in both the Onkens and MLTLs - I'm not sure that Dave has yet graphed the results, but I'm sure that some fiddling could optimize the aperiodic loading.

[Jim Griffin]

Chris,

We do need to keep in mind that the WR125S and FR125S are 4.5 inch diameter drivers. Hence, they are not be capable of delivering subwoofer level output for low bass material. They do have significantly greater Xmax than the Fostex drivers. But the CSS drivers have lower SPL sensitivity than the Fostex units. Now given the CSS units' excursion and power handling capabilities, they run rings around the Fostex drivers for bass. Bottom line is that each brand of drivers have positive and negative issues to consider for the specific application.

The bipole ML-TL configuration helps to prevent low end bottoming by it use of two drivers versus just one. You get 3 dB more acoustic output. But, I would recommend that the user who wants chest pounding bass should expect to use a subwoofer crossed in the 50-70 Hz area. This frequency range will help relieve these small and blend with the FR125S and WR125S midrange output. Realize that the Fostex drivers would need significantly higher crossover frequencies because of their limited excursion.

Jim

[robertG]

Chrisb,

My experience with the FR125S in a TL is very close to what Jim describe. I have absolutely no bottoming out at very high levels, and the bass is strong (too strong?) and accurate all the way down.
I listened to the Patricia Barber Track you refer to (as well as the Autumn Leaves track on the nightclub album), without any stress, and at realistic levels.
I noticed that on my Pionner 15 watts vintage amp, the amp simply could not pump out enough power, so it stumbled and coughed a few times, while when using the heavy muscle of my small (60W) Bryston amp, things were very well controlled up untill clipping (which happens at around 100W).
Could what you experienced by caused by a mechanical problem with your units? or a leak in the enclosure that would unload the driver?

[planet10]

Originally posted by robertG
Could what you experienced by caused by a mechanical problem with your units? or a leak in the enclosure that would unload the driver?

So far it happens on every instance of a sample set of 6 different pair speakers (WR or FR) half of which were bipoles. This is a problem that was 1st mentioned to me by Tim Forman & Al Wooley before i ever saw a WR or FR. It may well be tied in with clipping of the amplifier -- the biggest amp we have used is a 25W BGT NIGC (it is unfortunate that there seems to be an inverse relationship between power & potential amplifier quality).

From my point of view it is not unexpected & is life trying to get max bass out of a 125mm speaker. The bass on these drivers is tremendous (as you say -- even too much in the "right" box), i just think it important that people know that they may experience this problem with ported enclosures (or big sealed as well) -- it is quite dramatic when it happens. It does not subtract from my belief that this is a fantastic driver for the price.

Knowing about this, and that it is easy to get too much bottom out of the driver, means that one can consider boxes that one would normally discard because they restrict the bass output.

As i have said for the last 25 years, every good speaker deserves an active woofer (with a high pass for the drivers above) because the biggest benefit is improved midrange -- this little driver just gives way more in the LF than anyone has a right to expect, meaning lower XOs (if you add woofers), easier integration, and the option of living without happily. IMHO one of the very best set of compromises to get a FR driver with extension on both ends in a package that doesn't cost an arm & a leg, Bob & Dan get applause from me for their efforts.

I hope that this driver sees huge success, as i can only guess what the FR125 Special Edition (wholly a fantasy in my mind) might achieve.

dave

[robertG]

I dream of a driver with the bass extension of a 125 with the mids and highs of a Fostex FE108ES...

Perhaps four 125 in a twin-staggered TL arrangement, crossed at 200Hz or 300Hz to a FE108EZ in a closed box... Hum... I guess it's time to cut some wood...