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16 Aug 02:  The Hiquphon tweeters have a very good reputation, and most of the general characteristics of these tweeters are well known.  I have, however, sent one of each of these tweeters to Jeff Bagby for evaluation.  Jeff has performed very good evaluations of tweeters in the past.  He has decent equipment, and very good ears.  Jeff is very optimistic about having a good evaluation completed in 6 months.   I do realize this seems like a long time, but Jeff is a hobbyist too.  I also believe that rushing a project in any fashion leads to incomplete/unsatisfactory results.  Upon completion I will post Jeff's comments about general application here.

Until then, I can offer some insight into the OW1-FS.  The OW1-FS has Ferro fluid added.  Ferro fluid has 2 effects on ALL tweeters.  One effect is increased power handling.  The other effect is increased distortion due to the added viscous mass on the former.  Eventually I will be able to post more thorough information regarding this issue.  Some followers of Bud Fried may be interested to know that he used a older 3/4" Hiquphon Tweeter with Ferro fluid added.  I received the following from Oskar concerning the impact.

"As for curves of OWI before and after (OWI-FS) adding magnetic oil to the air gap please find below the actual curve bundles from the measurements taken of the 10 pair you are about to receive.


As you can see, impedance curves shows the biggest visible difference.
Lower Fs-peak and Fs moving a bit upwards in frequency. 
But also SPL curves change slightly. Sensitivity is a bit lower."

Something that really impressed me about these graphs is that they are a grouped plot from 20 different tweeters.  Anyone who has measured drivers in quantity will attest that this is uncanny unit to unit consistency. 



A Review of The Hiquphon Series of Tweeters

by Jeff Bagby.

A while back Dave Ellis asked if I would be willing to evaluate and write a review on the Hiquphon tweeters that he was now authorized to sell. Having not yet heard any of these tweeters I, of course, jumped at the chance, but I told Dave it would take me some time to get around to doing it right. He said, no problem, take your time. Well, itís still long overdue, but here is my review of the Hiquphon tweeter. I know a lot of you are already familiar with these drivers, so I will write this review more for the person who is not as familiar, but may be very curious about trying one out. Hopefully, the information I provide will assist this person in making their decision, one way or the other, on whether one of these tweeters is right for their application.

I have a toddler at home (no, this is not a horror story of dome tweeters and little probing fingers), and I still have a clear concept of the phrase "hiccup on". Whatís this have to do with a tweeter review? Well, the first question anyone has about these tweeters is how to pronounce the name, and as I understand it sounds like hiccup-on with an "f" sound in the middle. Now you no longer have to deal with fear of trying to order something not knowing what to call it and wondering if the person on the other end of the phone is quietly snickering at your ignorance. Say "hiccup-phon" quickly. Now youíve got it.

Hiquphon is the name of a small loudspeaker parts company in Pandrup, Denmark. It is owned and managed by one man Ė Oscar Wroending, whose initials are the OW that you see on each of the model numbers. In fact, it is my understanding that Oscar does everything from own the company, to assembling and testing the tweeters, to sweeping the floor and turning the lights out.

Hiquphon makes four models of their tweeters, each based on the same basic platform Ė a 20mm soft dome tweeter recessed into a semi-horn designed face plate, and each using the same motor and cup assembly. The tweeters are aperiodically damped to a rear chamber. Each has a 94mm diameter flange with 3 mounting holes. The rear of the driver is completely enclosed in a plastic housing with terminals that consist of two clearly marked holes of 2.5mm diameter on the back of the cup.

This brings me to my only two negative comments regarding these tweeters. First, Iím not big on plastic faceplates. Theyíre just too easy to ding up. Look at the Seas Excel T25-001 tweeter, which is in the same price range. Now thatís a faceplate and cup assembly to be proud of, other manufacturers should take note. DIYers often change out tweeters or move them to other enclosures. We like designs that are durable. I know someone will say that the plastic is well damped or something like that, but Iím talking toughness here. The second thing I am whining about are those holes they call terminals in the back of the tweeter. A good connection is almost impossible short of soldering. Since I did not want to deface these tweeters during a review I had to resort to cramming twisted wire leads into the holes, and sometimes holding them in place with tape. This makes me think back to those Usher tweeters with the big ľ" blade terminals. These are the kinda terminals I like to see on a tweeter. I understand that Hiquphon's terminal holes are the result of the way the rear chamber is sealed, but stillÖ..

OK, Iím done whining. Because there are a number of perks when you get a pair of these tweeters that you do not get with most drivers. Did I say pair? Yes, I did. When you buy these they come as a matched pair packaged together in a single box. These tweeters have been matched to within +/- Ĺ dB from 2Khz to 20kHz (according to the literature). However, in addition to the assurance that they have been matched, each box comes with an actual SPL and Impedance plot of each of the tweeters in the box, each signed personally by Oscar Wroending. Also included is a small pamphlet giving all of the mechanical, electrical, and acoustical specifications for the tweeter model, and each tweeter has a nice sticker on it showing the model and serial number along with some of the specifications. Plus, the data on the pamphlet is very extensive, even to the point of giving the THD%, the acoustic center of the tweeter, and the X-max, among other things. These are all very nice touches that go well beyond what you will normally receive when you purchase all but the very finest of drivers, and sometimes not even then. My kudos to Oscar for such excellent and informative packaging.

The general specifications of these tweeters are as follows; they have a recommended frequency range of 2.5Khz and above using a specified 12 dB/oct. or higher electrical crossover. Fs for the different models runs between 850 and 900 Hz. The Re is typically 5.8 Ohms with a voice coil inductance of 0.03mH, the minimum impedance is about 6.5 Ohms at around 3.5kHz, and this is generally considered an 8 Ohm tweeter. The rated power is 100 Watts (using the recommended crossover slopes). The THD is listed as less than 0.15% at one Watt, above 2.5 kHz. Dome and voice coil diameter are both 20mm, with a one-way X-max of 0.9mm (a heck of lot for a tweeter), and the acoustic center is listed as 11.3mm behind the front of the tweeter (or 7.6mm from the mounting face of the flange).

As I mentioned there are four models and here are their basic distinctions from one another: The OWI, which is the most heavily coated and damped of the group. Because of this it also has the lowest sensitivity at 87 dB/W/M and flattest response of the bunch as well. The OWII, is the same tweeter as the OWI but with a lighter coating on the dome. It has a higher sensitivity at 90 dB/WM, but also begins to roll off a little higher in frequency than the OWI. Next is the OWIII, which is similar to the OWII, but has a different coating on the dome. Living here in Northcentral Indiana there has always been something special in any reference to the "Golden Dome", especially in November (Notre Dame football, sorry). But in this case the golden dome is the one on the OWIII. I am not familiar with the story behind the gold coating and I assume that it is primarily for cosmetic reasons, but it does change the response slightly as well as the sensitivity. The OWIII is a little lower than the OWII, coming in at 89 dB/W/M. The literature calls this one the "high end" tweeter, though, so I am not sure if it is only cosmetic. Finally, the fourth tweeter in the line is the OWI-fs. Unlike the other three tweeters, which do not have ferrofluid in the gap (did I leave that out?), this tweeter is the same as the OWI, but with ferrofluid in the coil gap. The basic difference between it and the OWI is a broader flatter impedance peak at resonance; otherwise the response curves and sensitivity are almost identical above 2kHz.

The choice of tweeter that would be best for your application will more than likely be based on the different sensitivities, the use of ferrofluid, and the color of the dome, but what about the sound? Is there a difference in the way these tweeters sound that distinguishes them from one another? Before I answer that question I would first like to compare the tweeters to some of the other tweeters that I had on hand.

When I performed the comparison of the Usher 9950 tweeter to the Dynaudio D260, and Seas Excel T25-001, I also included the OWII (which matched up well in terms of sensitivity). Later I compared the OWII to an Infinity EMIT tweeter listening to the upper register resolution. Here are my thoughts on these listening tests.

I spent most of my time listening to the following CD's:

"Bonnie Portmore" from the "Highlander Endgame" soundtrack

"Trumpet Spectacular" with Doc Severinsen and Erich Kunzel (CPO) on Telarc

"Jazz At The Pawnshop" on Proprius

"Ariel Boundaries" by Michael Hedges on Windham Hill

"Erkiology" by Steve Erquiaga on Windham Hill

In each case I tended to find the D260 to be the airiest of the group, almost to a fault. This came out the strongest on Bonny Portmore whose female vocal (Jennifer McNeil) is recorded a little "hissy" anyway (which is why I selected this CD for the test). A quick response check indicated that the Dynaudio has peak in response in the 10kHz region. This made D260 sound unnatural to my ears. The Seas had the strongest projection of her voice, and sounded the least "hissy", probably due to the slightly rolled off top octave of the T25, which measure very smooth otherwise. It sounded much more natural than the D260 did. The Usher was very clean in the upper vocals and tended to sound more natural than the other two tweeters. It had a little more air than the T25, but not quite as airy as the Dynaudio. Overall the Usher seemed a little more neutral than the other two, and this is mostly due to the top octave differences between the three tweeters.

However, when I played the OWII I was surprised how much it sounded like the Usher, which is a much larger tweeter. Of course, the lower registers were not as strong with the OWII, but overall the tonal balance through the rest of the treble and into the highest octave was similar between these two tweeters. The OWII actually sounding the most neutral of the bunch in terms of top octave balance to the rest of the treble. This is a hard thing for a most tweeters to get right, but the OWII nailed it hands down. The OWII measures almost dead-flat above 3kHz and sounds so natural and open that itís a little uncanny.

It is amazing how much difference there is in appearance between a 28mm dome and 20mm dome, and you would swear that the 20mm had to be even smaller than that just by looking at it. Therefore, it was certainly not surprising that the OWII did not have the brawn to keep up with the other tweeters much below 3kHz. Crossing over much below this point is almost too much to ask from such a small dome. I would limit it to 2.5kHz to 3kHz depending upon the crossover slope chosen. As I reported in the earlier review, the Usher and the Excel tweeter were excellent in the region around 2kHz in terms of power and dynamics. However, on the other end of the spectrum itís a different story. Although the Usher measures flat to 20kHz the size of itís dome means that as you move off-axis the response in the top octave drops off quickly. The OWII, on the other hand, due to itís small dome had much better dispersion of sound in the top octave. So, even though both tweeters measured flat to 20kHz on axis the OWII sounded much more open with a much smoother power response in the top octave. The highs on this tweeter are not only very natural and balanced, but seem to fill the room with a more open, natural balance than the larger tweeters were able to do.

I spent some time listening to Trumpet Spectacular and at times I was having a very difficult time pin-pointing the differences between tweeters. Each tweeter had it's own sound but these differences were subtle and at times hard to define. The easiest thing to pick out was always the extra sibilance from the D260. The OWII was always a little different sounding in the way it spreads the "air" out into the room. After a while I began to feel that this was "right" and I missed it whenever I listened to the other tweeters, which started to sound more closed in. To my ear the other tweeters sounded less like "natural sound" than when I played the OWII. I have heard this effect before because I lived with a Dynaudio D21/2 for a number of years, which was similarly open sounding. I wish I still had them so I could make a comparison with the OWII, but I had given them away a couple months before hearing from Dave. From my memory though, it seems that the OWII has a flatter, more natural balance than the D21 had, but I am working only from memory here. I have not heard the smaller Scanspeak tweeter myself, so I am not able to comment on it for comparison, but others have compared it favorably.

While listening closely to the brush strokes and hi-hat on the Jazz at the Pawnshop CD It was easy to tell that the OWII seemed to be a little more detailed and honest than any of the larger tweeters. It had the best resolution of detail and was very balanced in the top octave. In this area I felt it was best of these tweeters. (Having said this, I will add that with a crossover that lifts the top octave of the Seas Excel a little it really comes alive and sounds remarkable on this passage too, but the Hiquphon seemed neutral enough that it would not need any contour. It is very natural over its entire spectrum). The OWII is the hands down winner among these domes in resolution of detail and openness in the top two octaves.

It was here that I tried a head to head with the OWII and an Infinity EMIT tweeter. This did not work out well as a test. The two tweeters sound very different and require very different crossovers to sound right, making comparisons difficult. The EMIT has a rising response in the top octave which exaggerates the detail that the planar already reproduces. The OWII, on the other hand, is very flat and balanced. I have said it before, and I will say it again, planars resolve tons of detail, but I find them difficult to integrate with other drivers. The OWII resolves detail better than any of the other domes that I had on hand, but itís smooth response and excellent dispersion make it very easy to integrate. Because of this I would personally select the Hiquphon over a planar tweeter in an effort to build a balanced and integrated "musical" sounding speaker.

My final test involved listening for differences between the four models of the Hiquphon tweeters. This proved to be the most difficult test of all. By the time I was done I wished that Dave had only sent me one sample instead of four different tweeters. Wow, what a headache! However, I did discern some subtle differences and I will attempt to describe them the best than I can. I used the same CD for this entire test, kinda "listening into" the music over and over as I switched out the tweeters and set the levels. The CD was Steve Erquiagaís "Erkiology" on Windham Hill which is a nice Jazz CD with some really nicely recorded treble.

Using the OWI as a baseline here are my impressions of the differences between the models. The OWI is the flattest and smoothest sounding of the group. It is very neutral and well-behaved, and based on the response curve looks like it will extend a little lower in frequency than the other models, as it is flat down to 2kHz. The OWII is more sensitive by 3 dB, but most of this sensitivity is at the expense of response below 3kHz. The response of the OWII is gently rising up to 3kHz, levels off, then selves up a couple of dB at about 4kHz where it is flat out to 20kHz. Sonically though, this is not the only difference between these two tweeters. It seemed to me that the OWII has a bit more resolution of detail than the OWI had, possibly due to the extra coatings on the dome of the OWI adding mass-damping to the diaphragm. The gold domed OWIII had a response shape that was similar to the OWII except that it had a little more emphasis in the octave between 5kHz and 10Khz, and was not quite as flat in the top octave as the other two versions were. Because of this emphasis, the OWIII seemed to have a little more "bite" or "snap" to itís sound. It did not seem as neutral as the OWI, but it did seem to be a tiny bit more dynamic sounding because of the mentioned slight rise in response around 8kHz. Keep in mind that these differences are very subtle. I donít want to give the impression that one version is excellent and another is not. That is not the case. Each of these definitely sound like they are in the same family of tweeters, and they sound more alike than they sound like other tweeters, itís just that there are small, subtle differences that distinguish them from each other.

The fourth version is the newest one of the bunch. It is the OWI-fs, which is a ferrofluid version of the OWI. The only real difference that I can tell from this tweeter is that the ferrofluid produces a broad plateau rather than a peak at the resonance. The normal OWI peaks at about 16 ohms at resonance and the OWI-fs has a broader peak at about 10 ohms. This may make the OWI-fs easier to work with with some crossover topologies. Sonically, try as I might, I was unable to hear any difference between the sound of the OWI and the OWI-fs. They sounded exactly the same to me.

In conclusion, the tweeters from Hiquphon represent an extremely high level of performance for small dome tweeters. They excel in flatness of response, resolution of detail, and open, wide dispersion. If you are planning to build a speaker that has a tweeter crossover around 3khz or so, then I can not think of a tweeter I would recommend more highly. Above this frequency they do almost everything right. Personally, I love an open sounding tweeter that allows you to move around some without loosing the sweetspot. These tweeters give you that and more.

Because of itís 90db sensitivity, high resolution of detail, and flat extended response with a nice smooth roll-off on the low end, I really liked the OWII, and I am thinking of using it with some Dynaudio D76AF midranges that I have. This may be a match made in Heaven, or maybe just Denmark, but you get my drift.

If you would like to know more about these tweeters contact Dave Ellis at Ellis Audio and I am sure Dave would be glad to answer any questions you may have and even sell you a tweeter if you are in dire need of one or two.

Jeff Bagby

Kokomo, IN

Re: Hiquphon vs Seas

Posted By: Ken Perkins <ken@speakerbuilder.net> (
Date: 11/26 7:49a.m.

In Response To: Hiquphon vs Seas (Sutton)

The Millenium tweeter in the Thors was the best sounding tweeter I had ever heard and it apparently works well crossed over low. But I was told by an attendee (can't remember his name...Chris something from Florida) suggested the Hiqs were better and I told him I had planned to try them. He was right, but the OW1's cannot play as low as the SEAS. They do everything else as good or better for much less money.

Ken also commented: "I've also determined they eat the Vifa XT25 for lunch.  I would consider these to be close competitors and the OW1 clearly beats it in every way, especially in dispersion and overall transparency."


There are other designs published using Hiquphon tweeters that I am very comfortable recommending.  Dennis Murphy and has worked very successfully with them.

Murphy Blaster




Cold Weather Testing

Lately there has been a trend towards using Hiquphon tweeters in car audio applications.  While I am not a car audio enthusiast, I can easily understand the difficult environment presented to the tweeter.  This is true in the acoustic realm and the climate realm.  One gentlemen from Canada prompted me to ask Oskar about how cold weather might impact the OW1.  Following this question, Oskar performed a fairly rigorous test.  His commentary follows:

Hi Dave,

Sorry it took a couple of days more than I expected to come up with a reliable answer to the cold tweeter question.

I had to check it several times with different units and also several times with the same unit to make sure that the results would be of some value.

Now I feel I have a (non scientific) conclusion for the behavior of the OW1 being frozen down (several times) to at least -21 deg Celsius and back again to normal temperature.

Freezing an OW1 to -21 deg Celsius (I can't go lower with the in-house freezers) seems to be harmless. Or it is at least almost harmless, as I am not 100% sure yet if sensitivity (maybe the magnet change a bit?) may after all suffer a tiny bit.
I found in a couple of tests that a small drop in sensitivity (up to 0,5 dB) seemed to have happened.

Especially to be seen a short time after having settled back to normal temp 20 deg C.
Then again after yet another 24 hours at 20 deg C I could hardly see any difference from the original condition and the new response (sensitivity and curve shapes exactly the same as before cooling down).

I also tried to re-magnetize 2 days later and then found that maybe a tiny drop in sensitivity was brought back to fully normal, so I suspect there might be a small problem with the magnet system, but I am still not sure that this was because of cooling down or because of other reasons (magnetizing twice may add a bit without any other reason - have to check that as well).
I guess I have to do some more tests to be absolutely certain what really happens here.

Anyway, the output from a frozen OW1 (minus 21 deg C) is really bad! This much I can say with certainty!
See attached curves.

So we may conclude in general that OW1 does not function properly at very low temperatures! I doubt any soft dome will (or for that matter any tweeter with a kind of rubber/fabric surround).

RECOVERY - coming back to life again:
But, when it reaches normal 20 deg C again, it works (almost) perfectly normal again.

This seems to be correct after having repeated the warm - cold - warm procedure several times.

I also forced the OW1 to respond to heavy power at low freq (0 - 1000 Hz) while frozen to minus 21 deg C. I did this simply to see if any part of the moving system would crack or otherwise be damaged (after all the surround and coating get very stiff and might not be able to handle high peak-peak movements. But that went well.

Recovery temperature inside however is a slow process, and I would not expect the tweeter to play normal just because the car-cabin temperature reaches, say 20 deg C.
One should expect a delay of quite some time for the temperature inside the OW1 to adjust to cabin temperature and thus until playing at its best again.

Well, this issue may not be completely clarified/solved, but after all dealt with and in my opinion one can conclude whether to use an OW1 or not under very cold conditions in a car.

Can I recommend to use OW1 in cars that are often used under very cold conditions?
- If played cold: NO!
- If played at normal temperature most of the time, and only occasionally frozen: Yes!
- Will the OW1 survive such a hostile environment and treatment?: To the best of my    knowledge, Yes!

Best regards
Oskar WrÝnding
to music with love...


I have spoken with Oskar regarding the design and construction of his tweeters.  I am more than happy to convey this knowledge and welcome telephone calls on the subject.