Home made field coil speakers.

dcathro

Well-Known Member
Sep 16, 2016
94
60
83
Melbourne, Australia
#1
9 years ago, I started a speaker project that, for various reasons, never got finished.

If anyone is interested, I started a thread on the Hifi Critic forum here.

Anyway due to being in a complete lockdown in Melbourne, Australia, I decided to use the time to complete these.

They were originally intended to be high efficiency ported bass matched to an open baffle mid and soft dome tweeter, however part way through, I decided I preferred the bass, sealed, and sacrificed some efficiency. One criteria for the project that the drivers should be alnico, but this then changed into 2 of the drivers being field coil.

The drivers are:

The Seas Exotic T35 alnico tweeter (94 db eff)



The Supravox 215 exc field coil widebander (99 db eff)


The Wolf Von Langa A150 Bass driver (97 db eff)



A friend in the Melbourne Audio Club built my 130 litre bass boxes for me out of ply with an outer layer of mdf. With help of a another friend I made the upper open baffle sections. They are also made out of layers of ply and mdf.

Some pics:











The crossover is external. I had originally wanted to run the Supravox's full range without a high or low pass, but found in practice that it was interfering with the tweeter and causing an excess of midbass energy.

The current crossover circuit modelled in XSim is:



The driver responses (1/3rd octave) :



The on axis summed response:



As I have a sealed bass alignment, the efficiency has dropped to about 91db, and the bass response is good only down to about 30hz in the room.

I am still working on fine tuning the crossover, and then have a number of other tasks to do.

The quality of the power supply has an impact on the sound of the field coils. For the bass I have massively overrated HP Agilent linear DC power supplies. On the Supravoxes, I have little 5A Mastech power supplies. Although people report that batteries work well, I would like to construct some Tunger power supplies.

The open baffle sections are crudely made, so I also intend to make some much nicer looking units.

Hope people enjoy the thread, and I would welcome any suggestions or criticism.

Thanks

David
 
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bonzo75

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Feb 26, 2014
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#2

dcathro

Well-Known Member
Sep 16, 2016
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60
83
Melbourne, Australia
#3
Thanks Ked.

Did you ever manage to listen to the line magnetic Tungar power supplies?
I don't know of anyone that has one. I did enquire about buying some, but plan to build my own. A friend picked up a box of NOS tungars for $5

Thanks, I will have a look at that.

Wolf mainly used Altec woofers to make his field coil before, so he also used the JBL 150?
Wolf made quite a few different drivers back in 2010. I think he stopped making the JBLs due to the lack of available cones. The Altecs were available from GPA

Since you are into OB, did you consider the Nelson Pass SLOB?
I did read Nelson's thoughts on the DIY forum when I started, but my inspiration was to build a better version of a speaker I had previously used:



These were sealed bass, with everything above OB and all drivers alnico
 

Robh3606

Well-Known Member
Aug 25, 2010
1,107
127
485
Destiny
#4
Hello David

Nice speakers! You can see the JBL heritage in the woofer frame. I use a pair of E-145's in one of my set-ups and love them. Must be fun experimenting with a field coil magnet where you can vary the field intensity. Lots of iron in the woofer crossover!

I did the exact same thing I had drivers for about 5 years and finally used my "covid time" to bring it together. I ended up with a 15" 2 way using 2216nd an M2 horn and a 476Mg driver. Went passive.

Enjoy them!

Rob :)
 
Apr 1, 2018
38
17
13
Ohio
#5
All--

Super cool thread.

I have two stereo pairs and a mono (5 total speakers) based off of full-range field coils. All of my main drivers are Rullits (3 different levels), and on my primary pair of speakers I also have field coil woofers from Supravox. So I guess I have 7 field coil drivers currently in active systems. I consider myself a field-coil fan, but I probably need to qualify that as the speaker design is, at least, equally important to top sound, in my experience. I have heard field coils sound just ok...they don't guaranty phenomenal sound by themselves, and some may never sound better than just ok. The power supplies are also super important to top sound, as previous comments suggest--IMHO.

I am currently running all my field-coils in a fully open-baffle manner, including the woofers. I considered the sealed box approach for the woofers, but I'm happy with even the woofers having an OB approach with the known trade-offs, at least in my main room (more on that below).

As for a little background on my journey to field coil, I started out first with horns and high-efficiency Altec speakers in both 16-ohm Valencias and then Model 14s (I still own both, but they are not in use currently). i modded (gasp) both models through cabinet re-inforcement and then eventual cross-over replacements for both sets of speakers. With the model 14s I was also experimenting with bi-amping (having successfully tri-amped some more traditional speakers previously), and correspondingly experimented with external and even active crossovers. All my mods sounded like improvements to me (eventually, anyway!), so it became clear to me that even tried-and-true and well-deserved "classic" speakers could have their sound improved with better parts and perhaps more complicated/expensive designs. My love of high-efficiency speakers started there, and I haven't lost it, and don't think I will.

I fell in love with field coils when I was able to spend a half-day at the home of the owner of Classic Audio Loudspeakers in Michigan. I went to hear his high-efficiency horn designs. His Hartsfields blew my mind, and I still rank them as one of the top speakers I have ever heard, anywhere, at any cost. The pair I heard had both the midrange and the woofer drivers as his field coils. I didn't hear any of his speakers without field coils, but I did also hear his same-priced T1.5s with the identical field coil drivers, and while they sounded fantastic in their own right, they were not even close to how phenomenal the Hartsfields sounded. I mention that for a simple reason--all things equal, I believe the field coil approach to drivers CAN improve the sound over non-field coils, but field-coil ALONE is not a guaranty...hence my point above about the design of the enclosure itself.

Fast forward a few years, I moved through 4 sets of Zus, abandoning horns, but keeping to the high-efficiency play. I still own a couple sets of Zu speakers and they are great for what they are, especially at used price points. But I think in spite of all their work to perfect the full-range, high-efficiency drivers they use in their various models (even with their custom mods), they have limits. I like their design principle A LOT, however--run a good, high-efficiency full-range driver with NO CROSSOVER, then augment the top with a super tweeter and the bottom with a powered sub.

In researching a number of other speaker designs in hopes of finding something that would convince me I didn't need to spend the $35K to get the sound of the Classic Audio Hartsfields, various data points re-inforced my beliefs in the Zu full-range approach. Companies like Avant Garde and Voxativ were seemingly designing some of their top models that way, the later with field coils at the top price points.

I met a fellow former-Zu owner, and we began to research this overlapping venn circle of field-coil plus high-efficiency driver together. He introduced me to the open baffle concept, and we found Rullit field-coils among other brands that we wanted to try. And we tried them, and liked what we heard. Then we researched and augmented the tops and bottoms, with appropriate crossovers (and in some cases DSP), and we liked those improvements. We have kept the full-range cross-over free, which we still feel is the right decision for us.

And that's how I ended up building two different sets of stereo open baffles. I love the first pair, and I subsequently built a second pair, basically "maxing out" the learnings of the first build in order to attempt an end-game build. I'm SUPER happy with the results.

I am not claiming to be right, or more right, than any other speaker designs out there. I'm also not a speaker builder trying to sell speakers, so I don't really care to convince anyone that what I have commissioned being built are the ultimate speaker. However, having heard a few other field coil speakers at significant price points, and a number of speakers at much higher price points with similar high-efficiency designs, I'm extremely happy with the design choices made and executed for me, in my main room. I will continue to seek out and listen to other very top-end horn and open-baffle designs as well as other field-coil brands, but I feel very confident that what I had built is very much on the high-end of these commercial offerings, and probably a much more reasonable price point (still super expensive!). Having said that, again, it won't be right for everyone.

Open baffle is an entirely different conversation, I realize. I have heard one of my 2 pairs in 3 different rooms and two different houses...they didn't work as well in 2 rooms as they did in my main listening room, so I fully admit that the open baffle isn't a universal winning speaker design. Having the bass open baffle may require a DSP set of corrections--in my case, I actually have to run one of mine with an inverted phase as to not cancel itself out, and it could probably benefit further from some further equalization (currently running that DSP, cross-over and equalization with REW-generated measurements and MiniDSP doing the, well, DSP). Downsides of this? Perhaps, but I'm hearing phenomenal bass right now, properly set up and amplified.

One final bias for me which I've already mentioned...high-efficiency beats low-efficiency, all else equal. The ease of which high-efficiency speakers can present a soundstage, live sound, dynamics and pace, combined with the ability to run very low WPC amps (with all the detail and musicality) keeps my interested in these high-efficiency speaker designs over harder-to-drive speakers and drivers. Again, that's my bias.

Thanks for starting such a great thread. I look forward to meeting others who are going down this slightly non-mainstream path! Phenomenal sound awaits us!

Jay
 

spiritofmusic

Well-Known Member
Jun 13, 2013
11,694
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E. England
#6
Parsons, well I'm on my second pair of Zus (Defs 2 2008-2013, Defs 4 to present day, latter modded w Duelunds and Lundahls). I've augmented my 4s with Townshend supertweeters and soon to be installed new amps to onboard subs. I'm soon gonna audition a fascinating tweeter/supertweeter option with the advantages of higher efficiency (95dB to match my Zus 101dB, compared to the Townshend 87dB), and variable xover settings.
The new Definitions 7 and Dominances 2 will dispense w the Radian 850 tweeters, run to three full range drivers with three concentric supertweeters R and L, 11kHz to 30kHz.
My guess is this will create a much more seamless and energetic high end, lending more snap and urgency to SQ.
Obviously not field coils, but maybe addressing some historical shortcomings of Zu that you felt the need to move on from.
 
Last edited:
Apr 1, 2018
38
17
13
Ohio
#7
I still love the Zu sound, btw, and I think they are moving toward a really great, even higher-end set of models to keep a bigger set of customers into high-efficiency options. It's exciting to see, and I'm a big fan of what they are doing for all ends of the cost spectrum. I most recently bought the Druid 6s...I used them for about 18 months and they were a nice step forward in many ways over my Soul Supremes (which I may never sell, btw, as I love them). Ultimately the first set of OBs worked a little better for me over the Druid 6s, in spite of a large number of amps I tried, and as such I moved on from those Zus. I know the new Defs and Doms will be an even bigger step up over what I had, particularly for larger rooms. I hope no one read what I wrote as a dis on Zu. I just personally didn't have a lot of hope that they were going to be able to beat the Hartsfields sound I heard--which is a VERY tall request.

Please keep us up to date on the super-tweeter findings. I am a big believer in the ultra top-end augmentation as well.
 

spiritofmusic

Well-Known Member
Jun 13, 2013
11,694
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#8
Parsons, I'm running my Zus 8' from front wall and 4' from side walls in a dedicated 18x48x9 loft space, and after a lot of finagling I really have them singing, especially on genres they struggled with in my old room, namely jazz and classical.
The supertweeters have definitely helped with upper end sparkle and air, and the crazily overengineered alternative to those looks very promising.
Sean Casey has tremendously high hopes for the new range, the move to multiple supertweeters looks fascinating.
 
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Apr 1, 2018
38
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13
Ohio
#9
My Druid 6s definitely enjoyed some distance from the walls in the 3 rooms I had them in as well. I ultimately had them 6.5' off the back wall and about 12' from either side wall in the end, and that's how they sounded the best. My first set of open baffles ended up in about the same spot, and my new larger ones are currently just a little bit wider out than that, but I'm still working on the perfect placement for them so we'll see.

I like the idea of multiple super tweeters...very interesting indeed.
 

spiritofmusic

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Jun 13, 2013
11,694
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E. England
#10
Well, he's going three full range drivers per side as well, supertweeters concentric within each.
 
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dcathro

Well-Known Member
Sep 16, 2016
94
60
83
Melbourne, Australia
#11
All--

Super cool thread.

I have two stereo pairs and a mono (5 total speakers) based off of full-range field coils. All of my main drivers are Rullits (3 different levels), and on my primary pair of speakers I also have field coil woofers from Supravox. So I guess I have 7 field coil drivers currently in active systems. I consider myself a field-coil fan, but I probably need to qualify that as the speaker design is, at least, equally important to top sound, in my experience. I have heard field coils sound just ok...they don't guaranty phenomenal sound by themselves, and some may never sound better than just ok. The power supplies are also super important to top sound, as previous comments suggest--IMHO.

I am currently running all my field-coils in a fully open-baffle manner, including the woofers. I considered the sealed box approach for the woofers, but I'm happy with even the woofers having an OB approach with the known trade-offs, at least in my main room (more on that below).

As for a little background on my journey to field coil, I started out first with horns and high-efficiency Altec speakers in both 16-ohm Valencias and then Model 14s (I still own both, but they are not in use currently). i modded (gasp) both models through cabinet re-inforcement and then eventual cross-over replacements for both sets of speakers. With the model 14s I was also experimenting with bi-amping (having successfully tri-amped some more traditional speakers previously), and correspondingly experimented with external and even active crossovers. All my mods sounded like improvements to me (eventually, anyway!), so it became clear to me that even tried-and-true and well-deserved "classic" speakers could have their sound improved with better parts and perhaps more complicated/expensive designs. My love of high-efficiency speakers started there, and I haven't lost it, and don't think I will.

I fell in love with field coils when I was able to spend a half-day at the home of the owner of Classic Audio Loudspeakers in Michigan. I went to hear his high-efficiency horn designs. His Hartsfields blew my mind, and I still rank them as one of the top speakers I have ever heard, anywhere, at any cost. The pair I heard had both the midrange and the woofer drivers as his field coils. I didn't hear any of his speakers without field coils, but I did also hear his same-priced T1.5s with the identical field coil drivers, and while they sounded fantastic in their own right, they were not even close to how phenomenal the Hartsfields sounded. I mention that for a simple reason--all things equal, I believe the field coil approach to drivers CAN improve the sound over non-field coils, but field-coil ALONE is not a guaranty...hence my point above about the design of the enclosure itself.

Fast forward a few years, I moved through 4 sets of Zus, abandoning horns, but keeping to the high-efficiency play. I still own a couple sets of Zu speakers and they are great for what they are, especially at used price points. But I think in spite of all their work to perfect the full-range, high-efficiency drivers they use in their various models (even with their custom mods), they have limits. I like their design principle A LOT, however--run a good, high-efficiency full-range driver with NO CROSSOVER, then augment the top with a super tweeter and the bottom with a powered sub.

In researching a number of other speaker designs in hopes of finding something that would convince me I didn't need to spend the $35K to get the sound of the Classic Audio Hartsfields, various data points re-inforced my beliefs in the Zu full-range approach. Companies like Avant Garde and Voxativ were seemingly designing some of their top models that way, the later with field coils at the top price points.

I met a fellow former-Zu owner, and we began to research this overlapping venn circle of field-coil plus high-efficiency driver together. He introduced me to the open baffle concept, and we found Rullit field-coils among other brands that we wanted to try. And we tried them, and liked what we heard. Then we researched and augmented the tops and bottoms, with appropriate crossovers (and in some cases DSP), and we liked those improvements. We have kept the full-range cross-over free, which we still feel is the right decision for us.

And that's how I ended up building two different sets of stereo open baffles. I love the first pair, and I subsequently built a second pair, basically "maxing out" the learnings of the first build in order to attempt an end-game build. I'm SUPER happy with the results.

I am not claiming to be right, or more right, than any other speaker designs out there. I'm also not a speaker builder trying to sell speakers, so I don't really care to convince anyone that what I have commissioned being built are the ultimate speaker. However, having heard a few other field coil speakers at significant price points, and a number of speakers at much higher price points with similar high-efficiency designs, I'm extremely happy with the design choices made and executed for me, in my main room. I will continue to seek out and listen to other very top-end horn and open-baffle designs as well as other field-coil brands, but I feel very confident that what I had built is very much on the high-end of these commercial offerings, and probably a much more reasonable price point (still super expensive!). Having said that, again, it won't be right for everyone.

Open baffle is an entirely different conversation, I realize. I have heard one of my 2 pairs in 3 different rooms and two different houses...they didn't work as well in 2 rooms as they did in my main listening room, so I fully admit that the open baffle isn't a universal winning speaker design. Having the bass open baffle may require a DSP set of corrections--in my case, I actually have to run one of mine with an inverted phase as to not cancel itself out, and it could probably benefit further from some further equalization (currently running that DSP, cross-over and equalization with REW-generated measurements and MiniDSP doing the, well, DSP). Downsides of this? Perhaps, but I'm hearing phenomenal bass right now, properly set up and amplified.

One final bias for me which I've already mentioned...high-efficiency beats low-efficiency, all else equal. The ease of which high-efficiency speakers can present a soundstage, live sound, dynamics and pace, combined with the ability to run very low WPC amps (with all the detail and musicality) keeps my interested in these high-efficiency speaker designs over harder-to-drive speakers and drivers. Again, that's my bias.

Thanks for starting such a great thread. I look forward to meeting others who are going down this slightly non-mainstream path! Phenomenal sound awaits us!

Jay
Hi Jay,

I think you are right that field coils are not necessarily better, but have the potential to be so.

Many years ago I owned Alon V mk2 speakers which had Alnico open baffle mids with a sealed tweeter and bass. I later upgraded to the Circes which were basically the same but everything was Alnico. It was obvious that the Alnico was way more musical, with more tonal colour, and micro dynamics than the ferrite. Later I read an article by Paul Messenger talking about the superiority of Alnico, only being surpassed by field coils.

I like the idea of having no crossover on the full range, and have tried that myself, unfortunately, so far, I have found that I get better results when I get the supravox out of the way of the tweeter above 6K, and also padd down it's resonance peak in the midbass.

The Supravox 215 is called a full range, but it is not! it does not have much bass below 60hz, and the treble is lacking above 6k. I chose it because I didn't want a whizzer, and wanted to integrate a tweeter.

A typical 3 way speaker will have a sensitivity of 87db and crossover points around 400hz and 3Khz. My aim was to get wore sensitivity 90+ and have the crossover around 150 to 200 hz and 6Khz, while at the same time achieving a flat frequency response.

I have a way to go yet before I have finished the crossover, and I am yet to really experiment with the power supplies. I had also ultimately intended to go semi active with a four channel amp, so that I don't need to lose so much of the efficiency of the mid and tweeter.

Cheers

David
 
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dcathro

Well-Known Member
Sep 16, 2016
94
60
83
Melbourne, Australia
#12
Hello David

Nice speakers! You can see the JBL heritage in the woofer frame. I use a pair of E-145's in one of my set-ups and love them. Must be fun experimenting with a field coil magnet where you can vary the field intensity. Lots of iron in the woofer crossover!

I did the exact same thing I had drivers for about 5 years and finally used my "covid time" to bring it together. I ended up with a 15" 2 way using 2216nd an M2 horn and a 476Mg driver. Went passive.

Enjoy them!

Rob :)
Hi Rob,

Thanks for your kind comment.

They are not much to look at, but I am hoping to improve the asthetics when I get them sounding good.

The K145s were the predecessor of the E145. They don't go super low, but are very punchy.

Being able to vary the BL and Q is very handy as part of the crossover experimentation.

What is the 2216 like, and were you happy with your final result.

Cheers

David
 
Apr 1, 2018
38
17
13
Ohio
#13
Hi Jay,

I think you are right that field coils are not necessarily better, but have the potential to be so.

Many years ago I owned Alon V mk2 speakers which had Alnico open baffle mids with a sealed tweeter and bass. I later upgraded to the Circes which were basically the same but everything was Alnico. It was obvious that the Alnico was way more musical, with more tonal colour, and micro dynamics than the ferrite. Later I read an article by Paul Messenger talking about the superiority of Alnico, only being surpassed by field coils.

I like the idea of having no crossover on the full range, and have tried that myself, unfortunately, so far, I have found that I get better results when I get the supravox out of the way of the tweeter above 6K, and also padd down it's resonance peak in the midbass.

The Supravox 215 is called a full range, but it is not! it does not have much bass below 60hz, and the treble is lacking above 6k. I chose it because I didn't want a whizzer, and wanted to integrate a tweeter.

A typical 3 way speaker will have a sensitivity of 87db and crossover points around 400hz and 3Khz. My aim was to get wore sensitivity 90+ and have the crossover around 150 to 200 hz and 6Khz, while at the same time achieving a flat frequency response.

I have a way to go yet before I have finished the crossover, and I am yet to really experiment with the power supplies. I had also ultimately intended to go semi active with a four channel amp, so that I don't need to lose so much of the efficiency of the mid and tweeter.

Cheers

David
We are in agreement. There are Alnico speakers that I am sure sound better than more poorly implemented field coils, for sure. I'm also a big Alnico fan! Love my 604Es! But I think somewhere someone has converted 604s to field-coil!

I feel your pain on the full-range driver dilemmas and how to best integrate the top and bottom speakers around them. I have been fortunate with my two sets of full-range (that we settled on) in that the top end, with proper amplification, was clean, and integrated well with the super tweeters we chose. My speaker builder used a passive crossover for the super tweeter on both builds and nothing on the main full-range. We built in attenuation into the super tweeter as well for ultimate tweaking with both the room, the power supply settings for the field coil full range, and the amplifier used (which will all impact the top end of the full-range). I even made him (reluctantly) put in the ability for me to effectively tri-amp the super tweeters separately (although I'm not currently--just jumpering them from the full-ranges).

I insisted on high-efficiency, and made no compromises there. Accordingly, because I want to use very low WPC amps, we set a clear design direction of ending with a super efficient speaker (>100db), without cross-overs on the full-range to help ensure that. In my case, had I reached the point you are at in my build (maybe we did? we bailed on our Supravox full-range drivers, but I don't remember all the reasons why), I moved to choose a different full-range driver. The Rullits we chose met the design requirements better in my cases.

In your case, I assume you first experimented with different amplification of the mains? Picking an amp that had some natural roll-off might have made the transition more smooth?

Please don't take any of this as criticism, but merely an alternate approach. I simply had a very clear direction to base a speaker around the unfiltered high-efficiency full-range, and so for me starting with a very good full-range in the beginning that met those goals with no major drawbacks (recognizing they will not go as deep nor as high, and would benefit from both bottom- and top-end augmentation).
 
Apr 1, 2018
38
17
13
Ohio
#14
I should add:

The Classic Audio Loudspeaker Hartsfields were the most emotionally engaging speaker I had ever personally heard. While very expensive in their own right, I have heard much more expensive speakers and systems and been always much less impressed. My aural memory of the half-day I got to spend listening to the Hartsfields is still emotionally vivid in my mind to this day. It was the most emotional I can remember feeling listening to recorded music, by a fair amount, up until owning the speakers I own and built in my listening space now. I have raised my expectations a fair bit since hearing those Hartsfields (largely because of them!), and I am very pleased to feel my current open baffles are in the same league. Others may or may not agree, that's ok.

My point is that the Hartsfields, with field coils in the mids and lows, and a version of my super tweeters--HAD crossovers in the mids, highs, and lows, as you are building yours. So I am also SURE that the design you are currently working can be amazing TOO. It's just a slightly different "recipe" than I chose with no cross-overs in the mids.
 

Robh3606

Well-Known Member
Aug 25, 2010
1,107
127
485
Destiny
#15
The K145s were the predecessor of the E145. They don't go super low, but are very punchy.

Hello Dave

Yes they don't but they are dynamic and linear as hell with the underhung coils and low moving mass. I have subs under mine and use them as mid-woofers cross them at 300Hz to 10" 2123's and the pair is really lively for lack of a better description! I have Be compression drivers up top.

What is the 2216 like, and were you happy with your final result.
I really like them! They can go a full octave lower with a bit of EQ. I have mine in a cabinet tuned to 26Hz with a 26Hz Q2 alignment so 6 db to flatten out the response. I get usable extension to 20Hz in room and cross them over at 700Hz to the compression driver M2 horn combo. They are also very dynamic and pitch perfect.These may be my last build but I have said that before!

Rob:)
 

dcathro

Well-Known Member
Sep 16, 2016
94
60
83
Melbourne, Australia
#16
We are in agreement. There are Alnico speakers that I am sure sound better than more poorly implemented field coils, for sure. I'm also a big Alnico fan! Love my 604Es! But I think somewhere someone has converted 604s to field-coil!
Wolf Von Langa did some 604 field coils. There was a pair on ebay about 5 years ago for a pittance. I was tempted to buy them.

I feel your pain on the full-range driver dilemmas and how to best integrate the top and bottom speakers around them. I have been fortunate with my two sets of full-range (that we settled on) in that the top end, with proper amplification, was clean, and integrated well with the super tweeters we chose. My speaker builder used a passive crossover for the super tweeter on both builds and nothing on the main full-range. We built in attenuation into the super tweeter as well for ultimate tweaking with both the room, the power supply settings for the field coil full range, and the amplifier used (which will all impact the top end of the full-range). I even made him (reluctantly) put in the ability for me to effectively tri-amp the super tweeters separately (although I'm not currently--just jumpering them from the full-ranges).
The Rullits with the whizzer obviously go a lot higher up than the Supravoxs, which I need to cross over at 6K. This is actually a lot easier than the bass, which is far trickier, as I tend to get more overlap.

I insisted on high-efficiency, and made no compromises there. Accordingly, because I want to use very low WPC amps, we set a clear design direction of ending with a super efficient speaker (>100db), without cross-overs on the full-range to help ensure that. In my case, had I reached the point you are at in my build (maybe we did? we bailed on our Supravox full-range drivers, but I don't remember all the reasons why), I moved to choose a different full-range driver. The Rullits we chose met the design requirements better in my cases.
I agree that the more efficiency the better. but to do this you need active bass, something I will look at later. I will still be limited to the efficiency of the tweeter at around 94 - 95 db.

In your case, I assume you first experimented with different amplification of the mains? Picking an amp that had some natural roll-off might have made the transition more smooth?
I am using an amp designed by a friend, solid state around 150W. It is not typical SS sound, but is both warm and fast. When I go active I will use that on the bass and another better sounding 20W amp on the top.

Please don't take any of this as criticism, but merely an alternate approach. I simply had a very clear direction to base a speaker around the unfiltered high-efficiency full-range, and so for me starting with a very good full-range in the beginning that met those goals with no major drawbacks (recognizing they will not go as deep nor as high, and would benefit from both bottom- and top-end augmentation).
I love your approach, but I know I can get these to sound very good. Their biggest limitation will be low bass being limited to about 35hz.
 
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dcathro

Well-Known Member
Sep 16, 2016
94
60
83
Melbourne, Australia
#17
I should add:

The Classic Audio Loudspeaker Hartsfields were the most emotionally engaging speaker I had ever personally heard. While very expensive in their own right, I have heard much more expensive speakers and systems and been always much less impressed. My aural memory of the half-day I got to spend listening to the Hartsfields is still emotionally vivid in my mind to this day. It was the most emotional I can remember feeling listening to recorded music, by a fair amount, up until owning the speakers I own and built in my listening space now. I have raised my expectations a fair bit since hearing those Hartsfields (largely because of them!), and I am very pleased to feel my current open baffles are in the same league. Others may or may not agree, that's ok.

My point is that the Hartsfields, with field coils in the mids and lows, and a version of my super tweeters--HAD crossovers in the mids, highs, and lows, as you are building yours. So I am also SURE that the design you are currently working can be amazing TOO. It's just a slightly different "recipe" than I chose with no cross-overs in the mids.
I would love to hear those Hartsfields!

it is the emotional side that drives my choice. I selected the t35 tweeter because I could not stop listening to it. The matching Seas midwoofer left me cold. The Supravox again had me hooked.

I am not a fan of most hi end audio, which tends to focus on detail rather than coherence and fluidity. That said, I have, on the rare occasion, heard Multi driver speakers with complicated crossovers sound very good.

I don't like high order crossovers, and have a preference for 1st order. That said, it is sometimes necessary to make the filters a little bit more complex to get a flatter response.
 

dcathro

Well-Known Member
Sep 16, 2016
94
60
83
Melbourne, Australia
#18
Hello Dave

Yes they don't but they are dynamic and linear as hell with the underhung coils and low moving mass. I have subs under mine and use them as mid-woofers cross them at 300Hz to 10" 2123's and the pair is really lively for lack of a better description! I have Be compression drivers up top.
I think the K145 might go a bit lower, but not by much. As I am running mine sealed, I really sacrifice some efficiency to get bass down to 35hz. Don't really want to run subs, as I feel the down sides outweigh the benefits.

I really like them! They can go a full octave lower with a bit of EQ. I have mine in a cabinet tuned to 26Hz with a 26Hz Q2 alignment so 6 db to flatten out the response. I get usable extension to 20Hz in room and cross them over at 700Hz to the compression driver M2 horn combo. They are also very dynamic and pitch perfect.These may be my last build but I have said that before!

Rob:)
26hz sounds fine to me, especially if you are getting efficiency and dynamics!
 
Likes: Robh3606

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