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Joined 2003
Jussi,
Here is the devil's opinion...
Even assuming a trap, a 2nd order LP at 2k will attenuate the W18 breakup at 5k less than 20db. That will not sound as good as you are trying to achieve no matter what the power response. I believe your original WG approach, maybe with a different tweeter or WG, is superior to using the W18's to control directivity in the lower treble.
Paul
Here is the devil's opinion...
Even assuming a trap, a 2nd order LP at 2k will attenuate the W18 breakup at 5k less than 20db. That will not sound as good as you are trying to achieve no matter what the power response. I believe your original WG approach, maybe with a different tweeter or WG, is superior to using the W18's to control directivity in the lower treble.
Paul
Paul W said:
Devils indeed. 😉
I know the problem. Personally I'd use 4th order cross 1600-1800Hz with waveguide without any gadgets or tricks for the radiation pattern. No-WG option also messes up my speakercloth idea. Dome is higher than flange surface so speakercloth along the panel causes the cloth to touch the dome. And I haven't found a operational solution for it.
You know anyone in EU area that needs a pair of Esotars? Personally I can't afford to have a closet full of top notch drivers. Accuton C2-12 looks very promissing for the WG option. Stiff diaphgram so it can handle the stress, good responses, small suspension, right shape flange and most importantly inverted dome structure which is pretty much ideal compared to high profile soft dome.
Shame there isn't that much objective data of those drivers. Efficiency isn't as high as Esotar but the waveguide sure helps so at least up to 5Khz it would have the same or more on axis output than no-WG Esotar. And like mensioned before, most music materials intensity is below 3500Hz so it should be fine.
Jussi
Member
Joined 2003
Jussi,
Those Esotars should be quite valuable if you want to sell them!
There is a very knowledgeable guy (Jon Marsh) working with Accuton tweeters and waveguides over on the HTguide forum. I don't remember which models though...maybe newer versions than you mention. Jon has better results with the grills removed to reduce diffraction on flat baffles and as I recall has, or intends to, leave the grills off with waveguides to avoid cavity resonances behind the grill.
The Accuton factory graphs on Madisound show significant distortion from 1-2k for the 13-6 versions. 23-6 looks good, though the top end may roll off significantly off-axis.
It still may be worth trying the recessed Esotars with a foam or felt "WG" before you sell them. If you are seeing actual diffraction, the material may be too dense and/or not optimally shaped.
Paul
Those Esotars should be quite valuable if you want to sell them!
There is a very knowledgeable guy (Jon Marsh) working with Accuton tweeters and waveguides over on the HTguide forum. I don't remember which models though...maybe newer versions than you mention. Jon has better results with the grills removed to reduce diffraction on flat baffles and as I recall has, or intends to, leave the grills off with waveguides to avoid cavity resonances behind the grill.
The Accuton factory graphs on Madisound show significant distortion from 1-2k for the 13-6 versions. 23-6 looks good, though the top end may roll off significantly off-axis.
It still may be worth trying the recessed Esotars with a foam or felt "WG" before you sell them. If you are seeing actual diffraction, the material may be too dense and/or not optimally shaped.
Paul
Paul W said:
Accutons grill is much bigger problem in waveguide than for example Seas aluminiums since its that large and there is some space behind it. Naturally it has to come off in WG application.
Yes and C2-13 had a pretty large 2nd harmonic peak around 8Khz. Propably not that bad in listening but it would be intresting to know what causes that.
Actually whole thing is pretty endless. I have the Esotars now but I can't afford to invest a pile of other HQ tweeters in the same time. I can try them without the guide and with felt absorbers. Such solution might give good performance and most importantly sound good. Should I stop there or sell the Esotars, invest something else and start the hunt all over again.
Same with everything. I'd love to buy a pile of everything, have unlimited timetable, good R&D equipment and other resources to play with. I can take these to a proper measurements but since the structure still is pretty large (34x130cm panel) and more importantly heavy (+50kg) it's not that easy with a standard car. Of cource I'll do this once the system pleases me and project is very close to finish. But as a R&D operation every once and a while... 🙂
2Khz 2nd order filter has exactly -20dB attenuation at the prime resonance of the W18. I've read about systems with even higher cross with same order. If I don't remember wrong Ellis 1801 is 2500Hz 2nd order...? But that's not really the point. Is -20dB enough, how can I verify it? Distorsion measurements? Extensive listening? Here are the on axis response in that earlier simulation. W18 distribution to overall sound continues up to 5-6Khz, some additional damping might be in order against those 7Khz and 8,5Khz peaks. Phasing matches nicely.
Perhaps the cross could be lower. But with 2nd order it starts to push the Esotars to their limits. Dynaudios present C1 model uses Esotar2 with 1,8Khz 1st order filter but the unit is new and the system 2-way monitor which is propably not even meant for high power system.
Jussi
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This looks very good ... In general though I'd say this: while measurements are certainly a good way to check for aberrations and confirm major design goals, the number of parameters that influence the result is just too great in audio to rely just on measurements, not to mention simulations which don't seem to really work even in circuit design. Perfection in one parameter may be offset by the resulting compromise in another area, possibly one not measured (distortion performance? "average recording" characteristics? etc).
I'd say, select a few possible implementations, confirm acceptable performance by measurements, and then live with it for a while, play program material and all that, then change it and see / hear whichever sounds best to you. I have been surprised at times when I made major changes that should affect my system's characteristics a lot (say, change the mid from a vintage paper fullrange desing to a modern high x-max poly cone), and found surprisingly little difference in the end result once implemented properly. There is the famous "art" part in engineering which depends on developing a feel for stuff ...
I'd say, select a few possible implementations, confirm acceptable performance by measurements, and then live with it for a while, play program material and all that, then change it and see / hear whichever sounds best to you. I have been surprised at times when I made major changes that should affect my system's characteristics a lot (say, change the mid from a vintage paper fullrange desing to a modern high x-max poly cone), and found surprisingly little difference in the end result once implemented properly. There is the famous "art" part in engineering which depends on developing a feel for stuff ...
Member
Joined 2003
Yes, but that is part of the fun!
This off-axis result looks much more consistent, what did you do to WG? What happened to 9k dip?
The little off-axis rise around 1.2k is interesting. I suppose it is tweeter flare at low-end of range. 1.2k is somewhat insensitive band for ear so it may not be as objectionable as higher frequency flare.
Things are looking up! 😎
MBK said:
Yep. I've been honest with myself. I call my "needs" as "perversions". Low loss suspensions, idea of a subwoofer, high output, high efficiency and so on. Some of them have a real point behind it and some are just things that I like to have. Some, like the idea of monosubwoofer, is propably just picking my nose until it bleeds if you know the saying.
Paul W said:
This is modified waveguide. Throat was machined in new shape. Now it fits almost perfectly to the Esotars flange and I used some mouldingwax (don't know is this the right word, you know, stuff that kids play with, shape things) to clear the rest. Tweeter isn't well intact so I don't worry about a bit poor CSD just yet. Packing tape and a single screw isn't exactly high end fastening. 😉
The off axis notch at tweeters range is very minor. Is it 1,5dB or so. Just looks more dramatical as it is. But the off axis rise at 1,2-1,4Khz is just the dipole null that is expected in this size baffle. This is one subject I knew all the time and I wrote something about it earlier in this thread. Without any baffles there wouldn't be that null but that just eats away system efficiency.
Fortunately there is an automatic cure for this when it comes to power response. I used two mids in MTM configuration and MTM has its vertical null between 1Khz and 2Khz range so I don't worry about it. Like you see the null starts to give up at 60 degree off axis response so I expect to have decent directivity to 80 degrees or so where my sidewalls send their first reflection towards the listening spot.
Here is another a bit more optimized response with the tweeters 90 degree off axis response on it. It's about 11-12dB down, not a perfect null like a "dipole front radiation matched" tweeter should be. However responses up to 60 degree off axis behave very well like a dipole front radiation. Off axis roll off is also very smooth and beaming isn't as big problem as it is with non-waveguided 1" tweeters.
Crossover is 1800Hz 4th order. At the crossoverpoint crossovers electrical response is about 5,5dB down and it starts to drop above 10Khz staying more than 4dB down under 4,5Khz. Now that's efficiency. Esotars specs indicate that they are about 92dB effiecient but roll off a bit from upper treble. Waveguide is the cure. Response rises and I have to eq it in the crossover but it also means more efficiency, less distorsion, more dynamics. And I suspect Esotar is pretty dynamic tweeter as it is.. Compared to 10Khz range (where Dynaudio published on axis response is at 92dB level) tweeter is about 96dB efficient below 4500Hz (since electrical loop goes down in the crossover). Nice. Midranges are pretty much a match for them and with a 300Hz (or so) 2nd order crossover all that efficiency is in business since no eq isn't required.
Jussi
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Accuton tweeter on WG
Jussi,
FYI...here is link to early measurements of Accuton tweeter on WG. It seems Jon is using C13-6.
Jussi,
FYI...here is link to early measurements of Accuton tweeter on WG. It seems Jon is using C13-6.
Paul W said:
Thanks. I started to consider Seas 27mm aluminiums. Especially 27TBFC/G looks promissing. Krutke measured pretty good performance from one and it fits straight away into my waveguides. Seas tweeters also have the grills that don't have to come off in a WG so domes are protected. Small children running in the house...
The actual cause of the 9Khz dip is driver failure. I measured both Esotars in flat baffle where WG artifacts naturally don't appear. Other has the notch, other doesn't. I'll send the failed one to a friend of mine who can rebuild it but I'm not that optimistic about it. Shame, I just got the guides and all working...
Jussi
I haven't posted my C25N-6-13 measurements yet- there is some irregularity in the 10 kHz region, but in 10-25 degrees off axis things look pretty manageable once the crossover is applied. I also think that it is an internal throat reflection, and managing the throat shape right at the tweeter is critical.
In all likelihood, John Krutke got a little lucky...
OTOH, after the measurements of this baffle, compared with my other test baffles and the U baffle Arvo's, I'm completely sold on the idea of flat baffles for the woofer system.
Expected crossover frequencies are 350 Hz and 2 kHz.
Still a lot of work to do, and may take another go at the waveguide- I bought half a dozen... 😉 Assembly precision is an issue.
OTOH, the pertubations in SPL in the 10 kHz region don't seem very audible with sweeps or pinknoise, and the tweeter dynamics are quite good. The waveguide loading further helps the underhung motor by reducing excursion at higher SPL levels; I'm seeing about 8-10 dB gain at 2 kHz.
Much work still to do...
In all likelihood, John Krutke got a little lucky...
OTOH, after the measurements of this baffle, compared with my other test baffles and the U baffle Arvo's, I'm completely sold on the idea of flat baffles for the woofer system.
Expected crossover frequencies are 350 Hz and 2 kHz.
Still a lot of work to do, and may take another go at the waveguide- I bought half a dozen... 😉 Assembly precision is an issue.
OTOH, the pertubations in SPL in the 10 kHz region don't seem very audible with sweeps or pinknoise, and the tweeter dynamics are quite good. The waveguide loading further helps the underhung motor by reducing excursion at higher SPL levels; I'm seeing about 8-10 dB gain at 2 kHz.
Much work still to do...
JonMarsh said:
Could you be a bit more specific? Better than H- or W-baffles?
I have considered few different approaches to my woofersetup in this project. Twin 25W doesn't play that well deep bass. They are more like lowmids. W-baffles have crossed my mind but they grow pretty large. Monopolewoofers with different crossover and positioning setups are one option. And then is the idea of flat baffles, four 12" on each side. Pretty much identical size as these mainpanels, placed just along the sidewalls. Flat baffle would allow gentler crossoverslope, for example 100Hz 2nd order would be fine...
But first this tweetermess. Bugger.
Jussi
Let me qualify/explain that- with a U baffle or H-baffle, I've always observed a tendency as you move up in frequency towards peaking followed immediately by a moderately deep notch. The notch can be ameliorated by not elimanated by damping the region in the U (stuffed U baffle, AKA cardiod diople.
OTOH, with the flat baffle and careful panel shape and driver positioning choices, it's possible to get a fairly smooth response to the panel cut-off without a following notch (in the 200-300 Hz area)(except at a much higher frequency due to dual driver path length differences and close measuring (1 meter) as I show here).
Possible practical advantage? better integration between "woofer" and midwoofer/midrange, and I think feasibility of a fairly good three way system as opposed to pretty mandatory 4 way system (or very low crossover point for midrange/midwoofer, as in Orion).
Notch at 1.1 kHz is due to measuring at 1 meter slightly above the axis of the upper woofer; path arrival time difference causes cancellation. Not of practical consequence in actual design, where vertical off axis will not occur in pass band at this angle (i.e., listening distance typically 2-4 meters, range of woofers nominally up to 250-300 Hz.)
OTOH, with the flat baffle and careful panel shape and driver positioning choices, it's possible to get a fairly smooth response to the panel cut-off without a following notch (in the 200-300 Hz area)(except at a much higher frequency due to dual driver path length differences and close measuring (1 meter) as I show here).
Possible practical advantage? better integration between "woofer" and midwoofer/midrange, and I think feasibility of a fairly good three way system as opposed to pretty mandatory 4 way system (or very low crossover point for midrange/midwoofer, as in Orion).
Notch at 1.1 kHz is due to measuring at 1 meter slightly above the axis of the upper woofer; path arrival time difference causes cancellation. Not of practical consequence in actual design, where vertical off axis will not occur in pass band at this angle (i.e., listening distance typically 2-4 meters, range of woofers nominally up to 250-300 Hz.)
Jussi,
What waveguides are you using for the 27BFCG? The ones that John Krutke use fit the 27TDFC but hit the grill of the 27BFCG.
-Brent
What waveguides are you using for the 27BFCG? The ones that John Krutke use fit the 27TDFC but hit the grill of the 27BFCG.
-Brent
JonMarsh said:
Ok. I got your point. Still flat baffle has its disadvantages with poorer deep bass efficiency and potential shaking problems. But naturally these aren't always an issue.
Hara said:
I'm using the same Hifitalo waveguide that someone on that htguide forum is using. Guy from Estonia?
It's made for Hifitalos own kits and commercial speakers and can hold Seas Prestige 25mm aluminiums straight away. With small modification the 27mm model fits.
Accuton C2-12 and C2-13 would fit as well but not that perfectly, they would have to be stripped from their grill which makes them vulnerable and I'm not that convinced of Accuton absolute quality. They are pretty pricy stuff as well.
Jussi
Jussi,
The Hifitalos waveguides seem difficult to purchase from given that their website is not english. I am experimenting with trying to get John's (MCM sourced) waveguide to work well with the Seas BFCG. The BFCG has the grill and blocks proper placement of the waveguide. This offsets the position of the BFCG tweeter dome. Since the BFCG and the TDFC have similar designs and dimensions, I made some rough estimates (using trig) of where the TDFC tweeter dome is relative to the baffle and waveguide so that by trimming the waveguide further, the BFCG tweeter dome would be in the correct relative position. The waveguide is touching the grill but there is also a gap between the waveguide and the tweeter baffle. I was thinking maybe putting foam insulation. I am not an expert in waveguide or tweeter designs and I am worried about stored energy problems (or anything else that could go wrong). Any comments on this particular modification design?
The Hifitalos waveguides seem difficult to purchase from given that their website is not english. I am experimenting with trying to get John's (MCM sourced) waveguide to work well with the Seas BFCG. The BFCG has the grill and blocks proper placement of the waveguide. This offsets the position of the BFCG tweeter dome. Since the BFCG and the TDFC have similar designs and dimensions, I made some rough estimates (using trig) of where the TDFC tweeter dome is relative to the baffle and waveguide so that by trimming the waveguide further, the BFCG tweeter dome would be in the correct relative position. The waveguide is touching the grill but there is also a gap between the waveguide and the tweeter baffle. I was thinking maybe putting foam insulation. I am not an expert in waveguide or tweeter designs and I am worried about stored energy problems (or anything else that could go wrong). Any comments on this particular modification design?
Brent,
You can send Hifitalo some email if I want to ask them about the waveguides: info@hifitalo.fi. Waveguide model is AWSM-140. They also has AWSM-120 for 19mm Seas aluminiums. 140 and 120 are diameters in millimetres.
Most kits have their tweeters glued behind the waveguide and with a perfect match they work pretty well. Waveguide (and following directivity) reduces baffle diffractions and distorsion while increasing efficiency and maximum output. Pretty good deal if well implemented.
The primary problem is the tweeter-waveguide connection. Transition should be very smooth and even. After that tweeter should be well connected with the waveguide to avoid stored energy problems. In my case those Esotar CSD graphs aren't that perfect but I don't even wonder it. I used packingtape to attach the drivers behind the guide. Just tested the response.
Strangely waveguides and controlled directivity is pretty unknown subject over the world. Most systems are normal box speakers with no-waveguided tweeter. Seems like flat on axis response is enough.
With the Seas you should propably modify your waveguide that the whole grid fits in the guides throat. AWSM-140 is made for 25mm models and while 27mm Seas models have same size dome the grill is bigger so the throat has to be treated a bit. But you need to get that waveguide to start right where drivers suspension or grid stops, no gaps between guide and tweeter flange.
Jussi
You can send Hifitalo some email if I want to ask them about the waveguides: info@hifitalo.fi. Waveguide model is AWSM-140. They also has AWSM-120 for 19mm Seas aluminiums. 140 and 120 are diameters in millimetres.
Most kits have their tweeters glued behind the waveguide and with a perfect match they work pretty well. Waveguide (and following directivity) reduces baffle diffractions and distorsion while increasing efficiency and maximum output. Pretty good deal if well implemented.
The primary problem is the tweeter-waveguide connection. Transition should be very smooth and even. After that tweeter should be well connected with the waveguide to avoid stored energy problems. In my case those Esotar CSD graphs aren't that perfect but I don't even wonder it. I used packingtape to attach the drivers behind the guide. Just tested the response.
Strangely waveguides and controlled directivity is pretty unknown subject over the world. Most systems are normal box speakers with no-waveguided tweeter. Seems like flat on axis response is enough.
With the Seas you should propably modify your waveguide that the whole grid fits in the guides throat. AWSM-140 is made for 25mm models and while 27mm Seas models have same size dome the grill is bigger so the throat has to be treated a bit. But you need to get that waveguide to start right where drivers suspension or grid stops, no gaps between guide and tweeter flange.
Jussi
Jussi,
Thanks for the advice. I figured that was probably the weakest part of my design was the gap. I'll try emailing hifitalo.fi. For treating the waveguide, you just sanded it down a bit? There are a lot of ways of making it fit.
-Brent
Thanks for the advice. I figured that was probably the weakest part of my design was the gap. I'll try emailing hifitalo.fi. For treating the waveguide, you just sanded it down a bit? There are a lot of ways of making it fit.
-Brent
Hara said:
Unfortunately I don't have my measurements from the original AWSM-140 with the Esotar without filling the gap. But it wasn't pretty. Few severe notches and peaks. Waveguides throat is very critical point, mess up there and there is much more harm from the guide than use.
Depends how much you need to fix it. AWSM-140 has 39,5mm throat as a standard. I needed to get it up to 44mm or so. It was fixed with a lathe. Just cutted some material off the depth so waveguides throat opened up to needed diameter. It's also possible to sand or cut it from the throat but not advicable. It makes a flat cut to the throat and that way change whole waveguides profile. The curved shape has to start right from the tweeters flange.
In my case tweeter is more complicated to implement since Esotar has flange with 45 cut on its own and it can't be removed without putting whole thing into pieces. Therefore I needed to fix the waveguide to continue Esotars own flange. It still doesn't fit perfectly but the little corner there is easy to fix with mouldingwax. I actually might use that stuff all they way to finish and it's very good stuff to experiment things. You can actually make a whole waveguide from it if you want to but naturally just for modelling.
Edit: Actually here is a closeup from the setup. Modified AWSM-140, Esotar and some wax. Results the latests responses.
Jussi
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I had read that the TBFC grid comes off fairly easily. Have you tried removing it to help with mounting to the WG?
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