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Old 12th November 2005, 01:41 AM   #1
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Talking My FR125S project is finally done!

And what a PITA is was!

Nothing electrical problems, but I got a crash-course in what *does not* finish well on MDF - almost everything my local hardware store carries!

After reading a lot of forums and talking to a lot of people on the strengths/shortcomings of this driver, I tried to be creative, while keeping rather conservative (since it's a prototype for a possible commercial design).

After much fooling around on the computer, I decided on a bass reflex (for size, I have a **very** small house) with twin ports to keep the wind velocity < 16M/s at full power. I did this because I put the ports on the front instead of rear, so they could be backed against a wall or act as a set of bookends on an enclosed shelf.

The ports were dampened at the front with low density foam. This is an attempt to tame the outrageous (an understatement) bass cabability of these drivers. Without some dampening, they'll run out of Xmax long before the power rating is reached, if cabinet design isn't careful.

The window screen on the front of the ports serves two purposes - 1) keep the foam plug in and 2) keeps crayons and toys out!

Sound:

I have done a lot of listening tests, but this is the first set of fullranges I have owned. Three things struck me immediately:

1) I thought I had my headphones on for the presence of mids that sounded "live"
2) So, this is that imaging everyone has been talking about!
3) Where the heck is the volume?

About the last one... While the speakers they replaced were a set of Clarion car speakers shoved in a little K3 box, they must have been 16dB+ more efficient, because if my power meter on my not-so-cheap Sony amp is accurate, I have to put about 50x more power into them for the same volume.

The bass is LOUD, but not boomy or loose. It's nearly as tight as with the ports plugged completely and MUCH tighter than any speaker I used to sell during my stint with RS.

I plan on doing a lot more testing with these and will let you all know
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Old 12th November 2005, 01:44 AM   #2
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If anyone is interested, here's the design I used.
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Old 12th November 2005, 02:47 AM   #3
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I forgot to put in my original post, the fourth thing I discovered right away about these drivers - volume balance.

Doesn't matter what level of audio you're listenting to the programming at, it sounds the same. No dropoff in bass or treble (remember those evil little "loudness" buttons on cheap equipment? Well, not needed).

Another discovery is the power vs. Frequency and Xmax curves of WinISD is bang bloomin' on!
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Old 12th November 2005, 04:44 AM   #4
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Nice finish on those speakers. Why did you use the R6/polyfill in that configuration?
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Old 12th November 2005, 07:07 AM   #5
westend is offline westend  United States
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Thanks for posting the plan attachment. I'm thinking about the FR125 in an easy to build box so this might fit the bill. About how much power do you think you are pushing to the speakers?
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Old 12th November 2005, 08:57 AM   #6
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Quote:
Originally posted by RockerII
Nice finish on those speakers. Why did you use the R6/polyfill in that configuration?
Thanks!

The finish is Krylon latex enamel in gloss black applied with a foam roller. Last time I'll be using it though, as it's actually a vinyl finish and about as durable as rice paper


I've used polyfill, acousti-stuff and plain fibreglass house insulation in the past - I prefer the fibreglass, but the polyfill suited the purpose better on the top/bottom because of it's ability to stuff well on the round shape of the ports.

Also of note, is I "fluffed up" the glass before putting it in by tearing it along the cleave - doubling the volume.

Quote:
Originally posted by westend
Thanks for posting the plan attachment. I'm thinking about the FR125 in an easy to build box so this might fit the bill. About how much power do you think you are pushing to the speakers?
You're welcome!

Did some measuring...

Above 100Hz, you can put the full 25 watts into it no problem. Below that, it linearly rolls of until just above Fs (~61Hz), where you run out of Xmax at 6-8 watts, just as the program predicted.

This is not a problem for me, since she's designed to be attached to a SE boosted-triode amp capable of 9WRMS full tilt.

If you do not need the kid-proof screen on the front, to simplify things just use any 2" port from PE or CreativeSound and silicone the foam on the rear of the port instead of the front. Position of the foam in the port is moot. If you're financially handicapped, just route-out the flare like I did and use 2" ABS pipe into a small rebate behind the flare.
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Old 12th November 2005, 12:21 PM   #7
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Interesting design I might have to stuff some polyfill into my spirals once I'm done with it.

I thought FR125S is supposed to sound broken with SET amps?
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Old 12th November 2005, 12:35 PM   #8
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Quote:
Originally posted by eVITAERC
I thought FR125S is supposed to sound broken with SET amps?
I have no information on what amps were used, so I can't say if it was the speaker or amp.

I did try them with an EL36 tied as a triode and used zero NFB and it sounded fine. Currently I have a higher power design using CV4060/S11E12 with modest NFB I have to test.
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Old 12th November 2005, 05:25 PM   #9
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Quote:
Originally posted by eVITAERC
I thought FR125S is supposed to sound broken with SET amps?
The amps we had problems with were RH84 & RH34 style amps... it is interesting that with the latest sealed bipoles the RH84 does not exhibit this problem (a little shy on power thou)

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Old 12th November 2005, 10:37 PM   #10
morbo is offline morbo  Canada
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Nice work! Love the finish, too bad its not durable.
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