| ABS |
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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| chrisb |
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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| 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 |
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| Geek |
| 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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| ABS |
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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| chrisb |
| 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 :D ) 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 :eek: )
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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| Cal Weldon |
| quote: | Originally posted by chrisb
Since I'm not a huge fan of big bass |
No? :D
| 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 :censored:
Oh and Chris, :cheers: and Merry Christmas to you and yours. Hope to come over sometime in the spring. |
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| chrisb |
| quote: | Originally posted by Cal Weldon
No? :D |
"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 :censored: |
anything below 100K is too low for my taste (but then my hearing's not totally shot yet)
| quote: |
Oh and Chris, :cheers: 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 :clown: |
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| ABS |
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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| chrisb |
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 :bawling: ) 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/Ext....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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| ABS |
Chris:
I appreciate your detailed response and your perspective on these questions. My response will be somewhat lengthy as well.
I do realize that the design of virtually every piece of audio equipment is one of compromise - (whether it be speaker design, amplifier design, d/a design, turntable/cartridge design, etc.). The example you gave of the comparison between the two amps is a good one since it exemplifies the point well. I also agree with you that what sounds "good" should be the priority and not so much attention applied to acheiving an absolutely flat frequency response. Truth be told, I usually like my speakers to have a slightly forward midrange but an overall balanced sound and I typically don't care for speakers which are too "laid back". But, this is just my taste in how to tune the speaker. Does this imply an absolutely flat on-axis response curve is required, no it doesn't. On the other hand, I do still feel that the goal of having a "relatively" flat speaker response on axis plus a good power distribution off-axis is fairly important to making a speaker sound good. Mind you my design philosophy doesn't require perfection in any area - just good overall sound :).
So now we can have that philosophical discussion around what speaker designs are best and what compromises we can live with. In the WR minimonitor I designed, I had learned that the power handling was an issue for me - using the speakers for home theater (without a sub) or even for music at a moderate to high volume level could easily result in the speaker bottoming out and I am sure causing a farily large quantity of low frequency distortion just prior to reaching the point of bottoming out. I also noted that the upper frequency range was no where near good enough for my taste either on-axis or off axis). I also noted that the mid-range was just too hot and the mid-bass was too recessed as a result of the baffle step I would expect the FR to behave similarly. I am making some assumptions regarding how I expect the FR to perform based on my experience with the WR. I expect that the power handling issue will continue as will the poor upper frequency off-axis performance and the need for BSC.
So now we can really get into the questions of where to compromise the design? Please bear with me here as I don't know much about bipoles but I do find the bipole design to be intriguing. I see how it corrects for baffle step issue as well as improving power handling, but how does that solution address the relatively poor off-axis upper frequency response of the FR? Also, doesn't the bipole design reduce the "point source" benefits of a full range driver by reflecting sound front and rear? And then what about all the phase shifting that occurs at the sound wave interface between the two drivers that must also create some undesirable artifacts, no?
In regard to your second recommendation, bi-amping the FR with an Extremis in each enclosure, this seems like a fairly good idea, but at that point, why wouldn't I just put a single FR in a small sealed cabinet and build a single dedicated sub? Oh, the problems with are that I would still have to deal with the baffle step issue ergo reduced driver efficiency and I still wouldn't be addressing the upper frequency off-axis issues. On the other hand the power handling problem would be largely corrected since the F3 would be around 90hz or so in the sealed box and the sub would handle all the really low stuff . . . Perhaps a sealed FR with a tweeter and BSC plus a sub makes sense?
At the end of the day I am agreeing with you that simpler is better but only when it makes sense within the design criteria/goals. Maybe the issue is my preconceived notions of how to build a full range speaker. Even considering all the things the FR does well it is in itself a series of design compromises. These are the compromises I am trying to address in whatever design I build. I always come back to the idea of my wanting to "solve" for the noted off-axis problems and power handling problems without losing the coherency provided by having a "point source" driver. In a way, you and I are agreeing on the power handling and baffle step questions both of your recommendations address this issue (add a woofer down low or use a bipole configuration). On the other hand, why ignore the upper frequency issues? If the x-over is high enough it should not destroy the overall voicing from FR and should provide significant additional detail and clarity plus much better off-axis response which I think would help the imaging of the overall speaker.
Then when I start to think about how to build a simple x-over, the concept of using low order slopes with drivers that have wide bandwidths always seems appealing to me - it is simple and keeps the parts count low which are good things in my book. The point is it is difficult to find a really good mid-woofer that can come anywhere near the performance of the FR at its price point. So why not shift the perpsective slightly and take advantage of those things the FR does so well, but reduce the impact of all those things it doesn't excel at?
Andrew |
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| tubesguy |
Andrew -
If I can read between the lines, it sounds as if you just really have an urge to do more than throw the FR in a box and listen. Even to the point of disregarding the suggestion to use the FR and Extremis, and then be done with it.
I think what Chris is saying is that, in his experience, the upper octaves of the FR are at least "good enough" if not perfect. My reading of the forum suggests that his experience is, at least relatively speaking, quite sizeable with regard to the FR and WR.
If you are at least convinced that you want to use the FR in some configuration, you could start with taking a pair and putting them in some at least semi-appropriate sealed boxes, and give a listen to the top end, just from the FR. If that's okay, then figure out what you want to do WRT woofers, BSC, and the rest. You can do the simulation, etc, _after_ you give a listen and determine whether you, personally, can live with the speaker in an at least mostly full-range mode.
Have fun with this - Pat |
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| ABS |
Pat - thanks for weighing in on this. Yes, I suppose you are correct, it IS about time I bought at least a pair to play with! Perhaps the top end really is good enough - no way for me to really know without listening and testing first I suppose . . .
Regards,
Andrew |
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| ABS |
| Alright - I just ordered up 4 of them. Will post more once I have broken them in and performed some basic listening tests. |
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| chrisb |
Yep, "a man's gotta know his limits"
Andrew - your point is well made regarding design goals / criteria. As I think I stated in the previous post, it is possible to exceed the performance limits of any audio component, sometimes with financially catastrophic and in the case of loudspeakers, permanent aurally damaging results.
I have succeeded in grossly clipping my low power tubed amplifiers attempting to drive the FR125/bipoles to concert levels - the sound ain't pretty whether it's the amp running out of power or the speaker farting.
If I understand your last post correctly, your experience to date has been with the WR. From my personal experience, there's no question that the FR has better in room high frequency performance than the WR. Since I do my critical listening from a dedicated listening position, and likely at lower levels than you might ( i.e. in my case average of 80dB or less) it's altogether that my results are tailored for on-axis performance, and well below the driver's power compression or the room's overloading characteristics. I can live with that.
But clearly in a different situation the limits of the FR/WR can easily be identified. I don't pretend to have the single right answer for your specific case ( cause first of all, there isn't one ), and it's likely to take a process of trial and error for you to find the best performance/price solution.
The Extremis is a decent enough midwoofer that there are several designs by RAW Acoustics, using it in TM/TMM/ MTM configurations; several in fact with WR & dome or ribbon tweeters. I've heard most of these models, and any one of them is more speaker than I need, particularly in the bottom - I honestly doubt the need for a sub, but Cal would probably argue that one.
So, try the FR's in as simple a sealed box as you want - if you roll them off high enough, you can get away with very small sub-enclosure, and still have more than enough room in the same cabinet footprint for whatever midwoofer you choose. For many reasons, I've never been a fan of either BSC EQ, or single bass drivers- even if the latter is only operating for the single lowest octave, which will definitely not be the case in a home theatre situation. Of course with an adequate midbass driver and baffle dimensions, the "step" will be hard to hear.
I don't have the technical expertise to answer your questions regarding flat frequency response, off axis power distribution, etc. ; there should be other contributors who can. But I can tell you that every time I visit the local audio shop where I did most of my shopping over the past 25years, and listen to their hi-end demo systems, with speakers designed by some pretty smart engineers ( B&W, Linn, Magneplanar, Paradigm, Tannoy, Wharfedale) to meet those criteria , I don't get the same goosebumps as from the prosaic 2-way AudioNotes (warts, sticker shock and all)
As to your remarks regarding issues of bipole vs "point source" radiation patterns, you might want to read the documentation attached to the following DIY project - if you're interested in math and measurements, there's a fair bit therein :
http://www.t-linespeakers.org/projects/tlB/index.html
FWIW, I can remember when first wetting my feet in this hobby in the mid 70's, a lot of discussion in commercial and the early "underground hi-end audio press" ( that evolved into Stereophile / Absolute Sound ) on whether the ideal speaker would replicate the real world by emulating an "omni-directional point source, throughout the entire audible range" - the floating pulsating sphere; or the opposite case of a flat monopole "open window". I've heard and owned many wonderful and not-so commercial and amateur designs from both schools of thought. |
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| planet10 |
| quote: | Originally posted by ABS
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 best place for the 0.5 driver is always on the back of the cabinet where the 90 degree phase roll is in the shawdow of the cabinet and where it can perfectly* compensate for baffle step... a bipole differs from a proper x.5 way system only in the inductor/HP on the back/0.5 driver. There is only 1 reason to put the 0.5 driver on the front -- and that is so it can be shown off.
*assumes a cabinet with front-to-back symmetry.
A 1,5 way FR system should be quite excellent.
If you want the driver to be at its best, you need to relieve it of handling deep bass.... set the crossover at the BS frequency & bi-amp.
Note that no filter solution ever perfectly compensates for baffle step because it doesn't deal with the ripple. The only true fix is to not have any BS... bipole or x.5 with the 0.5 driver on the back have NO bafflestep*
dave
dave |
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| ABS |
Chris:
Yes, I am agreeing with you. Different speakers can provide a different acoustical and emotional experience. Differences in design fundamentals can result in very different outcomes even when using the same drivers. I read that article over at t-linespeakers.org and I'll have to read it again to make sure I got all of it.
At the end of the day, I really like the concept and overall sound of the full range - I just want my cake and to eat it too!
At this point I am going to wait until I get the FR's in house to do some testing with them before I make any decisions about bringing other drivers into the mix . . . Having said that, the Extremis might just be on the short list!
Dave:
Your response is extremely helpful as I am leaning toward some kind of .5 configuration with the FR drivers. Could you please elaborate as to why it isn't good to place the .5 driver on the front baffle? I realize that the low pass filter will likely create some phase shifting - is it this phase shift that you suggest would be compensated for by placing the 0.5 driver on the rear? If so, then what is the impact of the group delay on the low midrange performance? I guess a shallow cabinet would be best to minimize that effect?
I know I have seen a number of 2.5 setups where the .5 driver is on the front baffle. For example, I recently read about this design:
link
And at first glance it seems like it might be good. Note that this is not the speaker I want to build, but the concept could be similar. What are the issues you see/know with this kind of design? In general do you see a problem with a narrow baffle design where both drivers are on the same baffle and the baffle step correction requires a high x-over point on the 0.5 driver? I would guess this could result in a muddying of the low midrange output - am I right? If so, then a wide baffle design with a lower baffle step frequency could be better, no?
I think I just found an article explaining exactly what you are describing - pardon my ignorance here - are you the author of it?
link
Having read the article I am now beginning to "get it" - let's say I put the 0.5 on the rear - does it have to be in the exact opposite position of the 1.0 driver or can I place the driver anywhere I want on the rear baffle and what is the impact of moving that driver up and down the baffle? Also, I would typically want to position the full range driver horizontally off-center to provide an improved baffle diffraction response - how is that dealt with for the .5 driver? Is the .5 also offset and if so is it to the same side or the opposite side?
Thanks in advance.
Andrew |
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| planet10 |
| quote: | Originally posted by ABS
Your response is extremely helpful as I am leaning toward some kind of .5 configuration with the FR drivers. Could you please elaborate as to why it isn't good to place the .5 driver on the front baffle? |
A 0.5 driver on the front only sorta compensates for baffle step and the roll-off due to the inductor mucks up an octave or 2 above its XO point. A 0.5 driver on the back perfectly compensates for baffle step (actually for perfect the box would need to have no depth, but in practice it is not that critical) and the phase roll of the crossover is in the shadow of the cabinet and has to reach the back wall & come back before it can interfere with the front radiation. If that delay is sufficient the Hass effect makes it immaterial.
| quote: | | I just found an article explaining exactly what you are describing - pardon my ignorance here - are you the author of it |
Yes... but it is really a condensation of an old thread here.
| quote: | Also, I would typically want to position the full range driver horizontally off-center to provide an improved baffle diffraction response - how is that dealt with for the .5 driver? Is the .5 also offset and if so is it to the same side or the opposite side?
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One of the advantages of the physical arrangement of the driver on the back is that the drivers can be mounted push-push. Force cancelation means that the drivers stay physically motionless in space, vibrations usually transmitted to the box are cancelled and your downward dynamic range is improved.
dave |
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| ABS |
Okay, I am gradually being persuaded that a bipole design could be the best way for me to proceed. Having mulled this over a bit, here is what I am thinking about doing:
Two FR125's in a bipole configuration both mounted slightly off-axis on their respective baffles and positioned directly in line with one another (front to rear). The rear unit will play only lower frequencies to compensate for baffle step and will probably use a 1st order x-over for rolling off the upper frequency range (this will need to be tested and modeled). The baffle will be as narrow as possible mostly for aesthetic reasons and this will result in a higher cut-off frequency for the rear driver (but that should not be an issue since this is a bipole design).
For enclosure type, I am toying with two ideas:
Option 1 - Using a single sealed enclosure of approximately .25 cu ft for both FR drivers and a second lower chamber of approximately .75 cu ft and ported for a sidefiring subwoofer providing output below 100hz.
Option 2 - Using a 1.0 cu ft ported enclosure for both FR drivers with a downward firing port tuned to around 50 hz.
Option 3 - Add a tweeter to the front FR125 (if needed) in conjunction with 1 and 2.
So here are the questions:
1. For the bipole FR setup, how close can the rear of the enclosure be to a wall and still provide decent sound/imaging? Does the requirement change if the rear driver is just doing BSC versus running full range (also see #2 below)?
2. For the bipole FR setup, what changes in overall system performance should I expect by rolling off the rear firing driver (BSC only) versus running it full range?
3. If I incorporate the sub-woofer into the design would there be any negative impact to its being side fireing? If so, I could possibly consider down firing or front firing but those designs would require a larger front baffle . . .
4. What is the best way to wire the two FR's? Am I correct in thinking that they must be wired in phase to get the push-push/pull-pull operation mode? Do I need to worry about wiring them in parallel versus series - my amps are not 4 ohm stable but I have read that the FR's wired in parallel still have a high enough impedance that amps won't complain?
Thanks.
Andrew |
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| planet10 |
| quote: | Originally posted by ABS
Two FR125's in a bipole configuration both mounted slightly off-axis on their respective baffles and positioned directly in line with one another (front to rear). |
With as narrow a baffle as possible (6") there is no room to offset the driver side-to-side -- see pic.
| quote: | | Option 2 - Using a 1.0 cu ft ported enclosure for both FR drivers with a downward firing port tuned to around 50 hz. |
Be wary trying to get too much bass out of the FR125, you will. When modeling go for a higher F3 with a better F10 and a more gradula roll-off.
Option 3 - Add a tweeter to the front FR125 (if needed) in conjunction with 1 and 2.
| quote: | | 1. For the bipole FR setup, how close can the rear of the enclosure be to a wall and still provide decent sound/imaging? Does the requirement change if the rear driver is just doing BSC versus running full range (also see #2 below)? |
Room dependent... as a bipole (given some toe-in) at least 2 ft out from the wall. If just a 0.5 then it needs to be out at least the width of the cabinet. With no baffle-step, any room gain will be more obvoius.
| quote: | | 2. For the bipole FR setup, what changes in overall system performance should I expect by rolling off the rear firing driver (BSC only) versus running it full range? |
They will throw a different soundstage. (ignoring the issue of how your amp behaves into the different impedances above & below the XO point.
| quote: | | 3. If I incorporate the sub-woofer into the design would there be any negative impact to its being side fireing? |
That is where i'd put it.
| quote: | | Am I correct in thinking that they must be wired in phase to get the push-push/pull-pull operation mode? |
Yes. They both load the box the same way.
| quote: | | Do I need to worry about wiring them in parallel versus series - my amps are not 4 ohm stable but I have read that the FR's wired in parallel still have a high enough impedance that amps won't complain? |
How your amp behaves determines series or parallel wiring... keep in mind that if you series wire you need to use a shunt cap to roll off the back driver for use as a 0.5.
dave |
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| ABS |
Dave:
Thanks for the response - just a few more quick questions.
I am thinking that placing the drivers somewhat off-center will result in possible improvements to the baffle diffraction. Since this is going to be a .5 setup, the dispersion off the baffle from the front firing driver is going to be important in the upper frequencies - do you concur with this logic?
In regard to getting too much bass out of the FR - is it your thought that room effect will effectively increase perceived bass between the F3 and the F10?
What is the shunt cap you mention on the rear driver? I was expecting to run the bottom end of the rear firing driver with the same tuning as the front driver and then to use an inductor to roll-off the upper frequencies creating a 1st order low pass passive filter. Are you suggesting I should go 2nd order instead with both an inductor and a capacitor? Also, I am expecting to need that filter regardless of parallel or serial wiring, no?
Thank you.
Andrew |
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| ABS |
Since my amps aren't 4 ohm stable I am now thinking that I might have some issues running two 8 ohm FR drivers in either parallel or serial since it will result in either a 16 ohm or 4 ohm load.
Would it make more sense for me to go with a rear mounted WR125ST driver which I could wire in parallel with the front mounted FR driver? Of course my concern is whether or not that would that still provide the same baffle step correction or if the two drivers need to be identical to acheive the desired result? |
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| planet10 |
| quote: | Originally posted by ABS
I am thinking that placing the drivers somewhat off-center will result in possible improvements to the baffle diffraction. Since this is going to be a .5 setup, the dispersion off the baffle from the front firing driver is going to be important in the upper frequencies - do you concur with this logic? |
Yes... just keep in mind that the narowist possible baffle means there is no room to offset the driver,
| quote: | | In regard to getting too much bass out of the FR - is it your thought that room effect will effectively increase perceived bass between the F3 and the F10? |
Yes... and it is very easy to get heavy bass out of the FR that is over-the-top.
| quote: | | IWhat is the shunt cap you mention on the rear driver? I was expecting to run the bottom end of the rear firing driver with the same tuning as the front driver and then to use an inductor to roll-off the upper frequencies creating a 1st order low pass passive filter. Are you suggesting I should go 2nd order instead with both an inductor and a capacitor? Also, I am expecting to need that filter regardless of parallel or serial wiring, no? |
If you wire in parallel you use an inductor to roll off the 0.5 woofer, if you wire in series that doesn't work, you have to use a shunt capaitor across the 0.5 driver.
dave |
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| happy.gringo |
| Any suggestions about what value to use for the shunt cap? |
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| planet10 |
| quote: | Originally posted by happy.gringo
Any suggestions about what value to use for the shunt cap? |
A value that has the impedance of the cap down 3 dB at 0.707 times the -3dB of the -3dB of the baffle step frequency is a good place to start
dave |
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| DSP_Geek |
| quote: | Originally posted by planet10
A 0.5 driver on the front only sorta compensates for baffle step and the roll-off due to the inductor mucks up an octave or 2 above its XO point. |
I hadn't heard of that. Could you please elaborate?
Thanks,
Francois. |
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| planet10 |
| quote: | Originally posted by DSP_Geek
I hadn't heard of that. Could you please elaborate? |
Unless on a perfect shaped baffle the baffle loss response has a ripple in it. If the 0.5 driver is on the back it perfectly compensates for this ripple (since the back driver has the same ripple but in the other direction -- assumes a cabinet symmetrical fore & aft), a filter or a front mounted driver can only compensate for the gross levels above & below the baffle-step region.
When you are rolling off a 0.5 woofer you introduce a LP pole at about the baffle-step frequency. With this pole in place the response of the driver rotates thru 90 degrees of phase while the driver going up to meet the tweeter (or midrange) does not, so the 2 drivers are partially out of phase. With the driver mounted on the back, the phase roll is in the shadow of the cabinet (ie the part of its response that only sees 2pi steriradians) so it does not interfere with the main driver's response.
dave |
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| DSP_Geek |
| quote: | Originally posted by planet10
Unless on a perfect shaped baffle the baffle loss response has a ripple in it. If the 0.5 driver is on the back it perfectly compensates for this ripple (since the back driver has the same ripple but in the other direction -- assumes a cabinet symmetrical fore & aft), a filter or a front mounted driver can only compensate for the gross levels above & below the baffle-step region.
When you are rolling off a 0.5 woofer you introduce a LP pole at about the baffle-step frequency. With this pole in place the response of the driver rotates thru 90 degrees of phase while the driver going up to meet the tweeter (or midrange) does not, so the 2 drivers are partially out of phase. With the driver mounted on the back, the phase roll is in the shadow of the cabinet (ie the part of its response that only sees 2pi steriradians) so it does not interfere with the main driver's response.
dave |
I can understand how the back-radiation from the rear driver will be the dual of the front driver's output, but won't there be problems with phase delay due to the depth of the cabinet? For example, assume a 15" wide box, also 15" deep: the baffle step will occur around 300 Hz, but the depth of the box will introduce a 120 degree phase shift from the back speaker at that frequency, and 180 degrees at 450 Hz. Those phase shifts will mess up the vector sum of the outputs something awful, one would think. Mirage seems to get around this by having wide but shallow cabinets for their dipoles, causing the baffle step to occur fairly low down while minimizing back-to-front delay. I looked at placing 0.5 drivers on the back panel for my design, but finally the delay was just too much to deal with and I ended up putting them on the front. It might be you're not seeing nulls as deep as might be predicted since you're also getting reverberant energy in that part of the spectrum. I can see the back driver in your design adding some useful room energy right when the front driver radiates into half-space as opposed to full-space.
As for the LP pole in the 0.5 driver, doesn't that go away since baffle step is a minimum-phase phenomenon, where phase can be predicted from the shape of the response curve? In that case flattening the amplitude response will also clean up the baffle step phase response. Even if we accept the LP phase argument (which I think is open to question), baffle steps tend to occur from 250 to 400 Hz, thus placing the LP corner frequency at about 175 to 285 Hz. Most mid-tweeter crossover frequencies are about 10 times that, so the 1st order function is about 20 dB down at that point and thus its contribution doesn't much affect the phase of the dominant driver being crossed out.
Cheers,
Francois. |
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| planet10 |
| quote: | Originally posted by DSP_Geek
I can understand how the back-radiation from the rear driver will be the dual of the front driver's output, but won't there be problems with phase delay due to the depth of the cabinet? For example, assume a 15" wide box, also 15" deep: the baffle step will occur around 300 Hz, but the depth of the box will introduce a 120 degree phase shift from the back speaker at that frequency, and 180 degrees at 450 Hz. Those phase shifts will mess up the vector sum of the outputs something awful, one would think. |
at 450 Hz the output of the back driver should be pretty much invisible to the front driver... the delay at the BS is theorectically an issue unless the box is wide & shallow.
Now i don't really build x.5 way system, but true bipoles, and in pratical use the benefits seem to outweigh the drawbacks (cabs we do are usually 1 unit across & 1.6 units deep -- a worse case than what you have described)
I've seen quite a few people converted from discarding bipoles on an intellectual basis, to being fans after living with them for a while (me included).
| quote: | | As for the LP pole in the 0.5 driver, doesn't that go away since baffle step is a minimum-phase phenomenon, where phase can be predicted from the shape of the response curve? |
I don't think so, because we are talking about response above the BS frequency.
dave |
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| DSP_Geek |
| quote: | Originally posted by planet10
at 450 Hz the output of the back driver should be pretty much invisible to the front driver... the delay at the BS is theorectically an issue unless the box is wide & shallow. |
Turns out it's not quite so simple as that. If the baffle step is 2 dB down from maximum, that's about 0.8 in amplitude (as opposed to power), which means that 0.2 of the amplitude is diffracting around the cabinet (simplistic analysis, but bear with me). That 0.2 will return to the front, which is the point of the exercise of having a 0.5 driver on the back, but instead of supplementing the 0.8 amplitude of the front driver the summation is destructive and the sum becomes 0.6, or about -4 dB instead of 0 dB. The time delay will cause a series of ripples between the range where the path length adds minimal phase shift, and the point where the back driver radiates into half-space (and even then reflections from the back wall may hold a surprise or two).
| quote: | Now i don't really build x.5 way system, but true bipoles, and in pratical use the benefits seem to outweigh the drawbacks (cabs we do are usually 1 unit across & 1.6 units deep -- a worse case than what you have described)
I've seen quite a few people converted from discarding bipoles on an intellectual basis, to being fans after living with them for a while (me included). |
Bipoles, or dipoles?
In any event, bipoles have a number of useful advantages if one has the room to let the back wave develop properly. Chief among them is flatter room power response than standard closed cabinets, which in my opinion mitigates against "boxy" sound by virtue of the increased reverberant field above the baffle step frequency.
Cheers,
Francois. |
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| planet10 |
| quote: | Originally posted by DSP_Geek
Turns out it's not quite so simple as that. |
Here is the measured response of a Vifa P13W bipole vrs monopole
| quote: | | Bipoles or dipoles? |
Bipoles.
dave |
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| Scottmoose |
Ad that, Dave, is the lowest and flattest response I've ever seen from those wonderful Vifa drivers. Beats Lynn Olson's Ariels hands down. Very, very good indeed. What cabinet were they in?
Cheers
Scott |
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| Mark25 |
| quote: | Originally posted by planet10
...| quote: | | Bipoles or dipoles? |
Bipoles.
dave |
Yes, it's got a nice flat F response. But what does it sound like?
I've listened to a CCS FR125 (on its own, sealed box) and i can only imagine any sort of BSC/other drivers "here and there" taking away the slice of hi-end it gives on its own... |
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| planet10 |
| quote: | Originally posted by Mark25
es, it's got a nice flat F response. But what does it sound like?
I've listened to a CCS FR125 (on its own, sealed box) and i can only imagine any sort of BSC/other drivers "here and there" taking away the slice of hi-end it gives on its own... |
I've not heard TLbs, but the FR125 bipoles we've built outdo any of the monopoles....
dave |
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| Mark25 |
Is that just the bass that's better Planet10, or the whole musical spectrum; timing, seamlessness, etc?
Sorry to be so pedantic!
I'll be trying some tommorow evening with the bottom 300Hz rolled off with an electronic 24dB/oct L-R X-over to a monacor sph-135 basss unit. It should be interesting to see (hear) how much that ruins things...
We may even get round to adding a tweeter, a bit more off axis treble response would be welcome IMO, but that will probably ruin the sound too, we'll see... |
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| Scottmoose |
Cheers for that Dave.
Mark -knowing Dave, I'm 99.99% certain he means the whole frequency range. Bipoles usually are superior to monopoles; however, there are very few people, if any, who can design this sort of enclosure / system as well as Dave can. If he says they are special, then they will be very special indeed. I'm going to try a set of his Bipolar Bipoles with twin FR125s myself when funds and time permit. Which is a vote of confidence, if you like. |
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| planet10 |
| quote: | Originally posted by Mark25
or the whole musical spectrum; timing, seamlessness, etc? |
that...
They also throw a bigger image -- ie you lose a bit of the super-tight, super-focused (some would say unrealistic) image you get with some speakers.
And you room plays a bigger role (my room is very good)
dave |
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| mantisory |
i noticed that the bipoles you've built were in a sealed 25l cab...would it be possible(advisable) to build the same outer cabinet, but split it into two, and port both the top and bottom. keeping the same config in the top, but a eside firing extremis in the bottom tuned to 30Hz, say? I mocked up this...
Thanx,
Mantisory |
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| Bas Horneman |
| Could do...I think.....but how does one then handle the difference in efficiency between the Extremis and the CSS drivers? |
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| mantisory |
| possibly an active XO? |
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| Bas Horneman |
| And active amplification as well..for the Extremis..this has been mentioned earlier in the thread...but I wonder how Raw Acoustics solved this. |
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| mantisory |
| actually i was thinking to drive the fr's with a GC (which i have not yet completed!), and the extremis with a brytson 3bst...think that'll work out alright? |
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| Bas Horneman |
| quote: | | actually i was thinking to drive the fr's with a GC (which i have not yet completed!), and the extremis with a brytson 3bst...think that'll work out alright |
That should work fine. Whatever sounds best...you could try the other way around as well.. |
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| planet10 |
| quote: | Originally posted by Bas Horneman
...but I wonder how Raw Acoustics solved this. |
More than once i've suggested to Al a plate amp in the HT3. The passive has some R in series with the WR125.
dave |
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| Bas Horneman |
| quote: | | The passive has some R in series with the WR125 |
Well... whatever works...works ofcourse..but I suppose one needs a pretty powerful amp to drive the HT3?
But I thought WR125 was less efficient than the Extremis? So why was the resistor in series with the WR? |
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| planet10 |
| quote: | Originally posted by Bas Horneman
But I thought WR125 was less efficient than the Extremis? So why was the resistor in series with the WR? [/B] |
rated 86 vrs 85.6 -- pretty close actually,
Dan Wiggins designed the XO....
dave |
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| TerryO |
| quote: | | Dan Wiggins designed the XO.... |
..........and yours truely has listened to it. Best design to come out of Raw so far, IMHO. Al has a real winner!
Best Regards,
TerryO |
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| Mark25 |
We had a listen to a single FR125: on its own it's very good at showing the difference between amplifiers and the faults in speakers that have more than 1 driver. A good reviewing tool.
We couldn't get it to work with an active X-over at 300 Hz, not sure why yet, but we did add a super tweeter, i thought the extra top end and extra dispersion at the top was wellcome.
A *stiff* transistor amp did well at contolling the bottom end (more enjoyable IMO) and demonstrated very good timing, at the expense of all soundstage and depth. With a small amount of harshness creeping in.
SE Valve amps gave a really natural soundstage and depth, and the *relative* lack of timing could have been down to the fact that the valve setup had less top end treble. A more natural sound, with less of the hifi impressive...
I guess you can't have the best of both worlds...
More experimentation time needed, I'm a BIG single driver fan now tho ! |
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| ABS |
Well, I finally got around to routing my baffles and installing the drivers. I pulled together a quick and dirty crossover which is delivering suprisingly good results for just a few hours of playful "tweaking" by ear. The tweeter is the excellent Seas 27TDFC and the mid-woofers are both FR125s.
I ended up going with a TMM 2.5 configuration in a .75 cu ft ported enclosure from Parts Express. The port is 3.0" in length which should give a tuning frequency of approximately 50 hz. This yields between .5 and 1.0 db bump centered around 100 hz and a -3dB point of around 50hz.
So far the cross-over is a series cascaded 1st order low pass on the two woofers and a single cap with attenuation resistor on the tweeter circuit. Effectively first order x-overs all around :)! My intended goal of using two woofers to improve the power handling and efficiency of the speakers has worked well. It is still possible to bottom out the woofers but it really takes a lot more to do that now and at much greater volume.
I like these FR drivers much better than the WR. The bass response curve is much more smooth and therefore more natural sounding. The WR tended to have a big bump in low output compared to these FR drivers. It also seems that the top end of the FR is not just more extended but also smoother than that of the WR. I know the published frequency response shows improvements in the mid-band with the FR.
Compared to an FR playing on its own, I very much prefer the sound with the tweeter crossed in up top.
So far I don't have a single measurement, but I am really enjoying this basic x-over setup. Hopefully I'll have time to do the full SpeakerWorkshop battery of tests and simulations to share back with all of you what these speakers are actually doing and to tweak these x-overs.
Here are a few pics for your viewing pleasure for the time being:
Andrew |
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| planet10 |
Andrew... can you post some pics that haven't been posterized?
Did you add some bracing to the PE cabinet? The one i've seen was pretty, but not a great box...
dave |
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| ABS |
Dave:
Sorry about the photos. I will attach some new ones. I didn't realize how bad they were until just now.
The PE enclosures have an integrated vertical brace made of MDF. This is the second set of PE boxes I have purchased, the first being the .25 cu. ft. enclosures which I used for a pair of minimonitors with the WR and DX19 drivers. The overall fit and finish of the boxes is quite good. Compared to a custom purpose built enclosure they may not compare, but for a ready made and relatively inexpensive solution they are quite good for the money.
Andrew |
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| ABS |
| Here are the updated images - sorry about the problems with the others. |
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| planet10 |
| quote: | Originally posted by ABS
the first being the .25 cu. ft. enclosures |
Those are the ones i had experience with... i'd recommend that they get extra bracing before use otherwise they will colour (pun intended) your opinion of the drivers you install in them.
dave |
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| audiobomber |
| quote: | Originally posted by ABS
So far the cross-over is a series cascaded 1st order low pass on the two woofers and a single cap with attenuation resistor on the tweeter circuit. Effectively first order x-overs all around |
What crossover frequency to the tweeter? |
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| The Saint |
So what are your listening impressions of these speakers?
I have just built a dipole version MT-TL here is a photo.
Still experimenting, so cabinets not finished yet.
Dave is is advisable to add an inductor in series with the rear
speaker so as to only reproduce mid to low bass only. |
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| The Saint |
| Here is the rear of the speaker... |
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| planet10 |
| quote: | Originally posted by The Saint
just built a dipole version MT-TL |
You mean bipole...
| quote: | Dave is is advisable to add an inductor in series with the rear
speaker so as to only reproduce mid to low bass only. |
Depends on your room & your tastes...
dave |
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| ABS |
In regard to the PE enclosure, I think it is good enough. I put my ear up to the walls of the cabinet and didn't hear any strange noises/vibrations. Sure, there are better enclosures but these suit me just fine . . . As a side note, I don't see any reason why additional braces couldn't be glued into the enclosure. Also, for another option, I noticed that Madisound is now selling an enclosure, the M2 I think, which has three horizontal shelf braces and the configuration of those braces (solid or open style) can be selected by the designer. I think those enclosures are around 1.3 cu.ft. and might be good for a big MTM or a TM with integrated sub woofer . . . Lots of options with that one.
I think the tweeter now has around 5uF total. The 1.0 woofer is running a .1mH inductor and, if memory serves me, the .5 woofer is running a .15 inductor. The two inductors are wired in series with the 1.0 woofer tapped off the connection between the two inductors with the .5 woofer tapped off the end of the .15 inductor. This means that the .5 sees the combined inductance of L1 + L2 or .25mH. Please note that I have only performed listening tests on these and I still need to take some actual measurements with Speaker Workshop and follow my standard process for cross over design.
The speakers sound surprisingly good in this configuration. Decent imaging, very good sound stage - surprisingly deep and fairly wide. They are not as good off-axis as the straight TM minimonitor I had previously built. The tweeter sounds really excellent. They can play very nice and loud with generally low bass distortion. However, on some tracks with significant output below the tuning frequency I was able to get the woofers to bottom out at high volume. I will plan to handle this issue with a dedicated sub-woofer.
Andrew |
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| ABS |
Just completed some additional tweaking by ear. I am now running the tweeters with 8.9uF 1st order x-over and a single bleed resistor of 2.4 ohms going to ground. I changed the wiring to the woofers, no more series inductors. The 1.0 woofer now has a 1.0mH inductor. The .5 woofer is now running with a single .56mH inductor. The woofers are still wired in parallel. I'm really liking this tweeter. Very natural sounding! It's performance just continues to impress me.
I may need to boost the tweeter output slightly and attenuate the midrange a littler earlier because, even though the 3-6k range sounds "right", I can tell that from around 10k on up the output is a little too low . . .
In summary, these changes have resulted in a much cleaner midrange and improved overall balance. Listening to one of my test CDs, a high quality live Dave Mathew's disc, the performance of the speakers was really great. The overall cohesiveness of the sound, the depth of the sound stage, the imaging, the tonal balance, etc. all fell into place. I closed my eyes, got lost in the music and for a moment felt like I was at the show. I also heard details on this CD I have never heard before and I know this "Live At Red Rocks" disc quite well. The speakers are not at all "boomy". To the contrary, the bass response is nicely controlled with surprisingly good extension! I can already tell that these speakers are going to be something really special once finalized! |
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| ABS |
Latest update - I changed the 1.0 woofer's inductor to a .25mH. Everything else is still the same. This reduced the bump in the upper midrange quite nicely. There is still room for tweaking, but all in all, I am quite happy with the overall sound. A nicely detailed midrange with a clean top end and reasonable bass performance with good extension. Power handling with the woofers is still the issue, but that only becomes a problem when the system is really cranked to a volume much louder than typical listening levels in my room.
I should also add that I used 4" fiberglass insulation in the enclosure. One large peice cut to the width and height of the enclosure in the rear section and two vertical strips going from top to bottom and on either side of the woofers/port in the front section of the enclosure. The front and rear of the enclosure are separated by the vertical brace. In addition, I used some foam/vinyl combo damping material on the center brace itself to help reduce an resonances in that shelf brace. I applied the material to the top and center of the vertical brace. The combined effect of this damping material has been to greatly reduce unwanted HF reflections within the cabinet and from coming out the port. A noticable improvement in midrange clarity occurred by adding the damping material.
Andrew |
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| jleaman |
| I'm going to follow this thread as dave just gave it to me. Im looking at building these bipoles too but witha ribbon tweeter. Id like tobuild this Do i really need a sub ? I plan to use these speakers with my 4 mini a's, to bi-amp. |
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| ABS |
To be honest, the low end is fairly satisfying even without a sub when listening to music. I would think that for video you might want the added impact a sub can provide. These speakers are what is commonly referred to as a 2.5 design where one woofer runs more or less "full range" and the second .5 woofer is used to provide low end reinforcement and baffle step correction. I have managed to acheive very good results so far without doing much of anything special. The FR125 drivers are easy to work with since they have such a wide usable range. The tweeter I selected is also very easy to work with and all of the drivers are performing well with 1st order x-overs. I think the speaker will only get better as I tweak it more and begin actual frequency/impedance testing. I may also try some higher order x-overs to reduce interaction between the drivers and thereby improve resolution (it is quite good already).
Andrew |
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| chrisb |
| quote: | Originally posted by jleaman
I'm going to follow this thread as dave just gave it to me. Im looking at building these bipoles too but witha ribbon tweeter. Id like tobuild this Do i really need a sub ? I plan to use these speakers with my 4 mini a's, to bi-amp. |
Jason, a quick listen to the bipoles at Dave's place with the single stereo mini A should answer your question regarding "to sub or not to sub". A pair of WR125ST (16ohm) and Aurum Cantus G2Si would be a killer system, and require a far less complex XO than the Danish family of products. |
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| jleaman |
| quote: | Originally posted by chrisb
Jason, a quick listen to the bipoles at Dave's place with the single stereo mini A should answer your question regarding "to sub or not to sub". A pair of WR125ST (16ohm) and Aurum Cantus G2Si would be a killer system, and require a far less complex XO than the Danish family of products. |
What i think i will look and try to get a gasp of is, what dave and i were talking about.. Since i have 4 channels of 15 watt's of class a...
Ill go a pair of Bipoles. Speaker in the rear and a ribbon and drive in the front. I dont know the FR/Wr goes front or back but i think 600$ My budget will get me what i need. Now to get the boxes Ported and built might be the next challange.. My idea was to give the money to dave and let him get them done..
My goals ribbon tweeter and bi-amp able. Terminal cups ill buy and provide.
I just looked around my house for all my parts that i bought for these mini a's and i have no fet's left over due to the *recent Break in* ill have to now go buy more.
Jase |
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| ABS |
| I am not sure if 15 watts will give you the output you want. Even with parallel wiring on the woofers, these are not very efficient drivers. If I were you I would consider using four WR or FR drivers per side in some type of array to boost the efficiency . . . |
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| jleaman |
| quote: | Originally posted by ABS
I am not sure if 15 watts will give you the output you want. Even with parallel wiring on the woofers, these are not very efficient drivers. If I were you I would consider using four WR or FR drivers per side in some type of array to boost the efficiency . . . |
I think you should listen to a pair of mini a's and 15watts i PLENTY of power.. If a pair of mini a's for one tower of mine with 2 6.5" drivers and a tweeter can be cranked up really really REALLY loud and not sound ditorted I would have to say that mini a's @ 15watts class a is OVER KILL. |
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| ABS |
I have never head the mini A's, but I do know that the CSS drivers are not efficient. Perhaps 15 watts from the mini A's would be sufficient to meet your needs. I don't know how big your room is, how many speakers you plan to build, if you are planning to bi-amp or not, etc.
I think it was Chris B who recommended you try out the mini A's with a single WR dual driver configuration to see if it will meet your needs. I would agree with this. The fact that the FR drivers, and even the WR drivers, have such a good HF exension should mean a simpler x-over. I didn't really find that to be true with the WR driver due to poor off-axis response and some strange peaks in its output in the top octaves, but the FR seems to be doing quite well with just the 1st order x-over so far.
I would think that there might also be some smaller Danish audio drivers which could perform well such as those 5" Vifa drivers used by Lynn Olsen in the Ariel design or the Seas coincident drivers.
There are also a few B&C coincident drivers which look intriguing for the money. These are also high efficiency. |
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| planet10 |
| quote: | Originally posted by ABS
I am not sure if 15 watts will give you the output you want. Even with parallel wiring on the woofers, these are not very efficient drivers. |
Even pn my room -- much larger than Jason's -- my 25 W chipamp drives the bipolars to levels beyond my needs. Jason will have 2 (or 3 -- be nice to do a special purpose tweeter amp) x 15 W which he can configure as 1 drives FR/WRs, 1 on tweeter, or 1 drives back FR/WR, other FR/WR + tweeter.
dave |
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| jleaman |
| quote: | Originally posted by planet10
Even pn my room -- much larger than Jason's -- my 25 W chipamp drives the bipolars to levels beyond my needs. Jason will have 2 (or 3 -- be nice to do a special purpose tweeter amp) x 15 W which he can configure as 1 drives FR/WRs, 1 on tweeter, or 1 drives back FR/WR, other FR/WR + tweeter.
dave |
If this is the desire for these amp's I'll bring home another set :) |
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| westend |
| I ran a pair of CSS FR125's with the original SI (pushes what, 6 w.?) in aperiodic boxes and they moved real good. Anything more than 20w. w/low program info. and they will be bottoming out. |
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| stretchsje |
I know I'm digging up an old thread here, but ABS- what are your long term impressions?
I searched for more recent posts on this forum from you, and found you have built (and even modified) the Zaph Audio L18/27TBFCG design. Which do you prefer?
I am contemplating building one or the other: a CSS 2.5 way or the Zaph design, and I'm happy to have found a person that has built both!
Do you have schematics for your final CSS 2.5 way design? On paper, that's the direction I'm leaning. |
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| stretchsje |
| No thanks. I admire what you've done there, but I'm targeting good off-axis response in a bookshelf speaker. I am aiming for 14" tall with a little wiggle room. (I plan to build three for a front, center, and right for my home theater and want them all oriented vertically.) |
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