FR125 New Design Options - Feedback Requested - diyAudio
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Old 21st December 2005, 01:22 AM   #1
ABS is offline ABS  United States
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Default FR125 New Design Options - Feedback Requested

Having "cut my teeth" designing a fairly simple 2-way with the WR125 and the DX19 tweeter, I am now evaluating options for the FR125. So, I am opening up the discussion to the experts here to help me decide what makes sense.

I want to improve upon my older WR125S design in at least two key areas: efficiency/power handling and upper frequency performance (as good as it is for the money, the DX19 still has a nasty resonance at 4K which can be heard even with the 2nd order x-over).

The designs I am considering are:

1. 1.5 configuration using one FR125 running full range and a second FR on the same baffle running only in the lower bandwidth to provide baffle step correction. I expect that this would improve efficiency by about 6db (if wired in parallel) and avoid the need to apply baffle step correction the x-over. My modeling suggests that these two drivers in a tuned ported enclosure should play flat down to 50 hz. My concern is whether or not the mid-bass/mid-range will get muddied with the second driver playing on the same baffle?

2a. TMM configuration using a smoother/better tweeter than the DX19 - probably a 1" textile dome tweeter - with the same 1.5 configuration listed in #1 this then becomes a more conventional 2.5 configuration. Concern here is whether adding a tweeter would help or hurt the overall system performance (assuming a properly designed x-over)?

2b. One other twist on this idea in 2a is to use the FR125s as a dedicated mid/tweeter (if it's HF performance is that good) and then to use one or two larger woofers - perhaps 2x8" or 2x10" drivers in a TWW configuration where the woofers provide really solid bass and mid-bass performance. The concerns here are whether or not the FR125 can really replace a tweeter and how much sound coherence would be lost by integrating the woofers with the FR125 in the mid-bass below 1k. I suspect that this would defeat the purpose of using the FR125 in the first place since coherency is one of the key benefits of going full range.

3. MTM configuration using two FRs and a 1" tweeter. Concern is that for the MTM to work properly the x-over has to be low - let's say around 2k - I suspect that this defeats the purpose of using the FR125s and some other driver might be better suited to the application - perhaps a larger 6.5" or 7" driver. My guess is that this setup just doesn't make good sense.

I do realize that, when compared to the WR125s, the FR125S has better upper frequency extension, has a smoothed mid-band around 1k and plays the top octave better off axis than the WR as shown here:

Link

On the other hand not having one to listen to yet but knowing that I prefer both detail and excellent off-axis response in the upper two octaves, I am not sure if I will be happy with the high frequency performance of the FR compared with a good dome tweeter? This question is critical as its answer will play a pivotal role in determing the configuration for my next design.

There is also the new question of sealed vs. ported. In my opinion the Qts of the WR was too high to reasonably consider a sealed design and my listening tests of the WR in a sealed .25 ft^3 also confirmed that suspicion. However, the FR with its lower Qts represents an opportunity to explore the sealed design. As much as I like low end, I would bet that removing the group delay introduced by the ported configuration and using a sealed tuning with an F3 of around 90 hz might be quite nice when paired with a dedicated sub in a sub-sat configuration.

So there is my current thinking - any feedback or input on these ideas would be appreciated.

A couple of design constraints include no open baffle solutions and no dipole solutions - we can save those debates for another day.

Thanks in advance.

Andrew
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Old 21st December 2005, 06:51 AM   #2
chrisb is offline chrisb  Canada
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Default sounding like a broken record, but

can you say bipole?

try this:

http://www.planet10-hifi.com/sealed.html

This was initially an experiment to see how a WR & cheap tweeter could compare to the FR. Frankly, I prefer the former as the direct radiating set. Using a pair of WR per side could save enough to afford any one of a half a dozen or so cheap tweets, since they can be simply rolled in where the WR starts to fall. Of course you could always get spendy - Aurum Cantus ribbons etc.


Since I'm not a huge fan of big bass, I'm not missing not the extra cost of crossover and additional drivers. However, if you think you need your bass super-sized, the Adire Extremis utilizing the same motor technology would be a logical, if not inexpensive choice. Amazing bass from such a small cone area, but with the same efficiency trade-off as the CSS XBL drivers.
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Old 21st December 2005, 04:31 PM   #3
ABS is offline ABS  United States
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Chris:

Thanks for the feedback. I was trying hard to avoid sending this thread into the debate over bipoles vs. monopoles but I have never really cared for the sound of any I've ever heard. Perhaps the FR would be an exception?

On the other hand, I am really thinking seriously about a 1.5 or 2.5 configuration and was hoping to get some thoughts on those ideas specifically . . .

The closest design I could find on-line to what I am describing is here (note this is more like a mini line array than a 2.5 and is using the WR not the FR):

link

Some feedback on the quality of the top two octaves of output from the FR and thoughts on the impact of "blending" a second FR for low frequency baffle step correction would be greatly appreciated.

Regards,

Andrew
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Old 21st December 2005, 05:26 PM   #4
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Default Re: FR125 New Design Options - Feedback Requested

Quote:
Originally posted by ABS
2b. One other twist on this idea in 2a is to use the FR125s as a dedicated mid/tweeter (if it's HF performance is that good) and then to use one or two larger woofers - perhaps 2x8" or 2x10" drivers in a TWW configuration where the woofers provide really solid bass and mid-bass performance. The concerns here are whether or not the FR125 can really replace a tweeter and how much sound coherence would be lost by integrating the woofers with the FR125 in the mid-bass below 1k. I suspect that this would defeat the purpose of using the FR125 in the first place since coherency is one of the key benefits of going full range.

One thing I want to try in the new year is a pair of sealed FR's and an Extremis in a 2.1 config.

The FR's have a natural sounding mid/high and really great bass for smaller rooms, but for a larger system, say HT or large rooms, they need to be augmented in the bottom for SPL without bottoming out.
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Old 21st December 2005, 05:44 PM   #5
ABS is offline ABS  United States
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Yes, if the efficiency of the FR is anything like the WR (and I believe they are VERY similar), then the FR won't be able to take too much power or play all that loud when it is being asked to play low frequency material.

I do like your sub/sat idea but even a single FR in a sealed box would still require baffle step correction, no?

But try modeling 2 FR's in a bass reflex 1.0 cu ft. cabinet tuned to 50 hz and tell me if you still think a subwoofer would be mandatory?


Andrew
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Old 21st December 2005, 06:15 PM   #6
chrisb is offline chrisb  Canada
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Quote:
Originally posted by ABS
Chris:

Thanks for the feedback. I was trying hard to avoid sending this thread into the debate over bipoles vs. monopoles but I have never really cared for the sound of any I've ever heard. Perhaps the FR would be an exception?

On the other hand, I am really thinking seriously about a 1.5 or 2.5 configuration and was hoping to get some thoughts on those ideas specifically . . .

The closest design I could find on-line to what I am describing is here (note this is more like a mini line array than a 2.5 and is using the WR not the FR):

link

Some feedback on the quality of the top two octaves of output from the FR and thoughts on the impact of "blending" a second FR for low frequency baffle step correction would be greatly appreciated.

Regards,

Andrew

Andrew:

I guess my bias towards the bipole could cloud my judgement, but during the past 3 years, I haven't built one (with the design assistance of Dave Dlugos ) that I and others didn't like. Many of those preceded the CSS drivers, and used mostly Fostex 103( & variants) as well as FE127, and even some "no-names"

Be that as it may - to answer your question regarding the top-end performance of the FR125. In the few pair that I've heard in direct comparison ( at Bob & Al's "houseparties" ), it simply does not have quite the shimmering air and absolute speed of a ribbon such as the Aurum Cantus etc., but compared to a more mainstream fabric or plastic dome, it's a much closer horserace. (and don't even talk to me about metal domes)

But the premium paid with the ribbon is the very complex network required to protect the tweeter if crossed over any lower than 4-6K.

I can't remember if you mentioned whether enclosure size was an issue, or if you're considering 1.5 or 2.5ways with the FR/WR due to existing driver stock.

Crossovers can start to get very complicated once you start dealing with the additional issues of BSC, impedance compensation, and comb-filtering/lobing artifacts that MTM /TMM on small baffles can create, and have destroyed the midrange transparency and coherency of many a good combination of drivers of any make.


Depending on application, and acceptable enclosure size, my guess is that a simple 2-way with a single FR125 and Extremis would be more than sufficient SPL and bass output, while eliminating the need for any crossover in the critical midrange & up band. If you think the CSS drivers have amazing bass for their size, you need to hear the Adire Extremis. ( just one per channel though )


There's a decent compilation of DIY tested enclosures for many combinations of the CSS driver at:

http://www.planet10-hifi.com/boxes.html

I've built several of them myself, but you already know what my preferences are.
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Old 21st December 2005, 07:42 PM   #7
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Default Re: sounding like a broken record, but

Quote:
Originally posted by chrisb
Since I'm not a huge fan of big bass
No?

Quote:
Originally posted by chrisb
(and don't even talk to me about metal domes)
Well quit crossing them over so low. No wonder you think they sound like

Oh and Chris, and Merry Christmas to you and yours. Hope to come over sometime in the spring.
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Old 22nd December 2005, 06:50 AM   #8
chrisb is offline chrisb  Canada
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Default Re: Re: sounding like a broken record, but

Quote:
Originally posted by Cal Weldon


No?


"big" as in fat, sloppy, inarticulate - you know Home Theatre


Quote:


Well quit crossing them over so low. No wonder you think they sound like

anything below 100K is too low for my taste (but then my hearing's not totally shot yet)


Quote:

Oh and Chris, and Merry Christmas to you and yours. Hope to come over sometime in the spring.
thanks, maybe BBQ & beer season - gotta be stag nite tho - my wife has heard above Dave's place - I don't dare try to describe casa Weldon
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Old 22nd December 2005, 09:54 PM   #9
ABS is offline ABS  United States
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Chris - In regard to your idea of using 1 FR125 and a single large woofer (Extremis was the one you mentioned), am I correct to assume that you would then be correcting for the FR125 baffle step with the woofer as part of a modified 1.5 configuration? Or would you propose correcting for the baffle step with the x-over (thereby losing efficiency) and run the large woofer effectively as a subwoofer? If you are suggesting using the large woofer to correct for the baffle step, wouldn't I be better off just using another FR125 since the wouldn't be any difference in tonality and/or frequency response thereby resulting in (hopefully) a smoother transition between the two drivers?

Please realize that, although I don't have nearly the same experience as you, I am using simulation software and I do understand the basics of speaker and x-over design.

I don't have any stock of the WR drivers although I conceivably use one WR with one FR in a 1.5 setup. This could result in a smaller enclosure. I do like the tuning options for the FR much better than the WR even though the ported configuration does require that larger enclosure to get the most out of them.

I wouldn't consider using a ribbon due to the poor vertical response they usually exhibit - more likely I would go with a high quality low distortion 1" fabric tweeter - these can usually be crossed much lower than the ribbons - but by using the FR I don't think I'd need to cross so low anyway !

The biggest issue I am facing with any of the multi-woofer designs is the queston of $ value. By the time I add a decent tweeter and two FR's I am up to at least $175 in drivers. At that price point there are many other options I could consider which might provide equal or better performance in a straight 2-way configuration . . . If we accept that statement then it becomes a question of whether or not an FR based 1.5 or 2.5 system would be at least as good as a competing 2-way at that same price point.
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Old 23rd December 2005, 05:01 AM   #10
chrisb is offline chrisb  Canada
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Warning; having taken a final preview of this post, I realize it's run rather long - I tend to do that sometimes, sorry.

Oh yeah, like all posts on these types of forums, the free advice contained herein is based on my personal experience and preferences, and is worth exactly what you paid for it.


Andrew; to paraphrase Dave Dlugos, quite possibly the greatest thing about drivers like the FR125 ( actually, there are arguably very few with all the performance characteristics of the FR125 at that size and price) is their ability to allow an adventurous DIYer to open the door and step outside of the "Madisound/ Danish hi-fi" school of over-engineered* loudspeaker design

*italics mine - referring to the sometimes painstaking measurement and computer modelling efforts taken to achieve objectively "flat" frequency response, and excessive cabinet bracing / damping employed in attempts to eliminate enclosure resonances.

In many cases the complexity of passive circuitry to achieve the former, and cabinet dimensions and weights required for the latter, can take away far more from the emotional impact of the music than any "problems" they solve. Been, there - done that.

So, like many other FullRangers, I'm currently at the place where I'll more than happily accept an audio system with a certain amount of "personality", rather than none at all. Compromise is fine, and each to their own taste.

For example, just yesterday evening I spent several very enjoyable hours listening to a newly completed pair of Bottlehead Paramount 300B amps, in a system (not mine ) that normally runs a considerably lower powered amp ( Welborne DRD 45s) , with Cain/Cain Abby loudspeakers. Of course, the initially reaction on plugging in the higher powered amps ( 8W vs >2w) is "holy snappin arshows, these speakers do so have bass, and certainly more dynamics. Then after 3 or so hours, you plug the 45's back in and there are subtleties of texture, detail and emotional connection that I defy anyone to objectively measure or at the same time ignore.
Yes the large scale obvious differences remain - the 300B amp has more "balls", no question about it; but the "lesser" amp does many things that I prefer. What is the best compromise between the 2 amps? Perhaps a 2A3? OK then, which circuit, etc etc.

Back to the question of the FR125 speakers. As mentioned previously, I've built a few different speaker designs with combinations of the FR & WR, with and without tweeters. I'll also repeat myself regarding bipole - to oversimplify - I've found it to be almost a free lunch (except of course for the cost of the extra drivers). Compared to issues encountered in MM / MTM / TMM configurations, you can kiss the BSC and/or .5 way crossover issues goodbye. If you're concerned that your application will exceed the performance limits of the FR or WR125, then it would seem logical to me to mate with a woofer with similiar technology, materials and sensitivity. The Extremis takes the performance capabilities of the XBL motor technology to a new level - in a word they ****** rock.

In the case under discussion, my approach would probably be to use a single FR 125 and Extremis per side, and biamp, using PLLXO for the hipass . They can easily be built into separate plug-in module hobby cases, or even at the amp's input jacks.

Since the amp driving the FR125 is already hi-pass filtered, it's safe to operate it without any passive crossover. It is designed as a full range driver after all, and while it is possible to exceed the mechanical excursion and voice coil power handling limits of any driver ever made, it'll get reaaaallly loud first.

Depending on the frequency at which you want to cross over to the woofer, you can get away with a very small enclosure volume for the FR (for example the recommended 7 litres ported, or Dave Dlugos' excellent sounding 13 litre mini-onken design are designed for full range), leaving plenty of room in the same floor standing enclosure for the woofer. The recommended volumes for the Extremis are pretty tiny as well; 9.5 litres sealed/100% fill, or 21 liters, tuned to 33Hz ( is that low enough for you?) While I'm not really a big fan, any of the inexpensive sub plate amps would make for an easy experiment in bi-amping; some have reasonably flexible (if not sonically transparent) crossovers, and it wouldn't be too difficult to adjust the enclosure dimensions to accomodate the amp.



Extremis data sheet:
http://www.creativesound.ca/pdf/Extr...8Datasheet.pdf

I haven't played around with this driver yet, although I've heard systems of Al Wooley's and Tim Foreman's. It's scary good, but just not really my cup of tea.

And in closing, while probably only an issue for the flea-power/SET amp systems, the outstanding performance of the Adire XBL motor technology comes with an additional price to the cost of the drivers - their moderate sensitivity compared to traditional FR drivers. I can easily clip my RH84 SEP monoblocks and even (at much louder levels ) an EL84 PP triode amp, on either the MLTL or sealed (both bipoles) .
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