The Anatomy of the Acapella Violon - shocking find

For quite a while now I have been having trouble with the bass on my Acapella High Violon Suboktav 2001. With the help of a friend, we have dismantled this speaker and studied the internal construction and measured the crossover points. I am hoping that my findings will be helpful to all of you Acapella owners.

The bass problem is this: bass can not keep up with the speed of the midrange and top end. On some recordings, the bottom end becomes disconnected - you can hear music from the midrange and the top, followed by the bass response a microsecond later. Furthermore, the bass is poorly controlled and flabby. From my other Audiogon threads, you can see that I have been wondering whether the damping factor of my Cary CAD-211AE amps is sufficient to control the wild bottom end, and whether a solid state amp will cure this problem.

The current iteration of the Violon is Mk. IV. I am not sure what a "Violon 2001" is, I am guessing either Mk. I or Mk. II. Acapella's own website does not reveal any secrets, all it says is that the High version of the Violon has an additional driver inside.

Anyway, this is what we found.

PLASMA TWEETER: 4th order high pass crossover (24dB/oct) at 5000Hz. Measures very flat all the way to the limit of measuring equipment. Incidentally, Acapella marks the recommended tweeter level with a pencil mark on the tweeter volume pot. At the minimum recommended range, the tweeter comes in 12dB ABOVE the reference SPL. I had to wind the tweeter almost all the way down to get a flat response.

MIDRANGE HORN: First order high pass crossover (6dB/oct) at 450Hz, with a very gentle taper between 3dB/oct - 6dB/oct from 5000Hz and up. Goes all the way up to 10,000Hz. The shallowness of the low pass section of the band pass crossover makes me suspect that it is relying driver rolloff.

This is a surprisingly wide band of frequencies (4 1/2 octaves) to ask a horn to handle. As you know, horns are tuned to work over a fairly narrow frequency range and the response drops off at either extreme of this range. Wavelengths which are too long for the horn do not couple with the horn. Wavelengths which are too short will bounce around chaotically. That is only the theory however, because the horn measures very flat between 450Hz - 5kHz.

The integration between the tweeter and midrange horn is very good.

BASS UNIT. As advertised, there are two 10" drivers in the unit, and both appear to be SEAS drivers. The external driver is run through a passive crossover from the binding posts, with a low-pass first order crossover at 450Hz.

And now, the surprise. The internal driver is run directly from the binding post with no crossover in between. In other words, it is run full range, relying on driver rolloff only.

I can think of no advantages for a setup like this, only disadvantages.

Firstly, the drivers are wired in parallel. This will drop the impedance, making it difficult to drive them with valve amps (Acapella supposedly voice the speaker with the Einstein OTL).

Secondly, a configuration like this will result in destructive interference between the two drivers, ESPECIALLY if the crossover introduces phase problems in one of the woofers. Given the other woofer is crossover-less, any difference in phase will definitely cause interference.

Thirdly, running a woofer full range will cause cone breakup at the top, which will muddy the lower midrange (exactly what I have been hearing).

Possible solutions:
- wire both drivers to the crossover, maybe in serial configuration to increase the input impedance (Zin),
- disconnect and remove the internal driver, i.e. convert the speaker from the "High Suboktav" version to normal Violon,
- remove the passive crossover entirely and use a preamp-level crossover (active crossover).

Now, I am no speaker designer. I am just an enthusiast struggling to understand these things. But this just makes no sense to me. I am hoping that someone with more experience will be able to explain why Acapella made these design choices, and what you think of the possible solutions.
Let me see if I understand: The woofer that faces the outside world has a 450 Hz first order crossover, but the inner woofer has no crossover. Is this correct?

Are these woofers identical?

The crossover on the outer woofer - what does it consist of? Just an inductor? Inductor and capacitor? Inductor, capacitor, and resistor?

Are there in effect two internal chambers, one behind the inner woofer and the other between the outer woofer and the inner one?

Are either of these chambers ported?

Are they 8-ohm woofers, or do you know?

Just trying to envision the situation at this point.


Duke, thanks for your response.

Correct - the woofer that faces outside has the 450Hz crossover, and the internal one is full range.

Yes, the woofers are identical.

The woofer crossover has about a dozen parts. 3 inductors. Across each inductor is a capacitor. And there are a few resistors around. I will be getting a circuit schematic so that I can better understand what the designers had in mind, however my friend (who has my speaker at the moment) said that they look like notch filters.

The chambers are not ported, and in effect there are two internal chambers.

I do not "officially" know if they are 8 Ohm woofers or not, but my guess is that they ARE. This is because the "standard" Violon (which only has one woofer) is nominally 8 Ohm. The "high" version which I have is 4 Ohm. Given that I now know that the woofers are wired in parallel, it would make sense that it is an 8 Ohm woofer.



Thanks for the information. I think the woofer system you have is what would be called a "sealed isobaric".

It has been twentysomething years since I worked on an isobaric system. Basically, the inner woofer dances in sync with the outer woofer in an attempt to keep the pressure constant in that chamber between the two. "Isobaric" means "constant pressure". I did some measurements of an isobaric system years ago and my findings contradicted the conventional wisdom of how to model an isobaric system, but I won't bore you with the details.

Okay, in my opinion the inner woofer of an isobaric system should be rolled or else it mucks up the midrange. I do not know what order the rolloff should be, but either first order or fourth order make the most intuitive sense to me. In my homebrews, I used a first order rolloff on the inner woofer because that was much simpler to do.

There's a good chance that the discontinuity you hear is due to the inner woofer blaring away into the back of the main woofer. In my opinion, it would be a good idea to roll off the inner woofer above 80 Hz or so, and we'll try a first order network because that's probably the safest bet.

If you can by any chance come up with the model number of the woofer, that would be very valuable. Even just a physical description of the woofer would help.

If not, then we can "wing it" and use a 16 millihenry iron core inductor in series with the woofer (like a Madisound Sledgehammer), stabilizing the impedance with a SWAG zobel consisting of a 30 microfarad cap and a high-power 10 ohm resistor.

If you can come up with any identifying information on the woofer, or even just a physical description (cone material, phase plug, surround description, magnet description, frame description) I can hopefully make a more educated guess on the component values for the inner woofer's crossover.


Dear Amfibius,

Before you start modifying your speakers I would suggest trying other amplifiers.

Consider this, Acapella has been building speakers for over 30 years, and the Violon's have been around for at least 10 years. Many pair of Violon's have been sold around the world, and I don't know of any owners that have thought about modifying their speakers. Unless you are an expert speaker manufacturer and can completely understand the design theory then you are probably going to make things worse.

As with many of the higher end speakers on the market, the designer of Acapella speakers has many proprietary things inside these speakers that can't be understood by you or me. They have tuned the speaker to perform a certain way. If we try to change this then we end up with something else that the designer didn't intend.

I used to own Cary amplifiers and they don't drive all speakers well. My experience with Cary amps is that they are better suited to 2 way designs with simple crossovers, which are an easy load. And even then they still have that Cary sound. Which on the right speaker's is very pleasing, but on the wrong speaker is a disaster.

Something that's important to know about Acapella speakers in general is that they need very good to excellent electronics, otherwise you won't get their true performance. Remember that you own one of the few true reference speakers in the world, so now you need to use equal electronics because these speakers will basically tell you what your system is made of.

Think of your High Violon's as a perfect measuring device for testing electronics, cables ect... At this point the problem is not the speaker, but the system you are driving the speaker with. The speaker is simply showing you what your system sounds like. Many other speakers may sound great with your current system, but that's because they are not capable of this level of fidelity.

Best Regards, Brian
Given that I now know that the woofers are wired in parallel, it would make sense that it is an 8 Ohm woofer.
I'm not a speaker designer but doesn't this mean the internal woofer is operating at the same frequency as the other and not full range?
Duke, my understanding of an isobaric woofer is that BOTH woofers receive the same signal. In this case, the outer woofer is receiving a signal from the crossover, and the inner woofer is receiving a full range signal from the amplifier. All crossovers introduce phase issues, particularly a crossover as complex as this one. If there were ANY phase differences between the two drivers (in the same enclosure!) they would interact and produce peaks and dips in the frequency response.

I think that Acapella themselves have realized this, which is why there are notch filters built-in in the crossover.

If you want to see pictures of the dissected speaker, take a look here:

One of the pictures shows the back of the woofer (notice the flimsy looking spider?) with what appears to be a model number - SEAS CA25ACA. There is also a picture of the front of the woofer. A google search fails to bring up the driver. A pity, I was hoping to find the T-S parameters.

Brian, thank you for your suggestion however I do not believe a replacement amplifier will solve the problem. A solid state amp will only improve the damping factor, and it looks as if Acapella have "set in wood" the problem with the bass.

Having said that, I can easily borrow some amps from my dealer and see whether 600W of solid state Class A/B would be enough to drive the speaker. I realize that an amp like this will probably ruin the top end, but it should immediately answer the question of whether it can make the woofers move.

In another thread, I asked you if the updates to the Mk.IV version of the Violon can be retrofitted to mine (Violon 2001). The answer you gave was "no". My option at present is to sell the speaker or to modify it.
So many horn designers wimp out on the bass for only bass horns integrate proper and do justice to front horn systems. These are large costly why you dont see them. And who would want a 91db horn:) One of the benifits of horns is hi-eff and massive dynamic range seems this design would lose much of this. Its all about the tweeter thats how I feel about Acapella. The isobaric driver in cabinet wouldnt need a crossover sure most frequincy range gets filtered by cabinet not hard to set it up phase correct dont see a problem with that just the whole bass system, cool tweeter though;) I needed 8-15in hi-eff woofers mounted 4 in ea. in front horns to match my comp mid horn and comp tweeter the amazing fostex t500amk2. Now seemless integration all 1st order all levels match. Can run on one small amp no biamping. Like a seemless whole and once one hears proper horn bass nothing else is close. So much bass detail is lost to conventional designs.
Amfibius, thanks for the link to the photos. I can't tell much more about the woofer from the photos, unfortunately - I was hoping it would be identical to something in the Madisound catalor.

Eyeballing the crossover I see two notch filters and a contour filter, along with some impedance equalization. Looks like some high quality parts, by the way. The absence of an unbypassed inductor makes me think the voice coil inductance is on the high side, so I now propose a zobel consisting of 45 microfarads in series with 10 ohms, along with a 10 millihenry series inductor, to roll off the signal going to the inner woofer.

Isobaric doesn't mean both woofers get the same signal across the spectrum - in fact, in my opinion they shouldn't. If the inner woofer is allowed to play up into the midrange, in effect you have twice as much unwanted midrange energy bouncing around inside the box and re-radiating through the woofer cone. Isobaric loading is only beneficial in the deep bass region.


Have you contacted the manufacturer?? I am sure they will have idea's and be able to help.

Dear Amfibius,

I have dealers driving the Acapella speakers with Einstein, FM Acoustics, Jadis, Audio Note and Lindemann. These are all among some of the finest electronics that can bring out the qualities of Acapella speakers.

As with any high end speakers, you have to find the right synergy with your amplifier. I remember speaking with many Avantgard owners who went though several amplifiers until they found the right one. Many were just to noisy for these high efficiency speakers, and others made these speakers sound hard and forward.

I do suggest that you borrow other amplifiers from your dealer before trying to modify your speakers. If this doesn't take you into the right direction you would be better off selling your speakers rather than modifying them since this will kill the resale value.

I did speaker with Acapella and they did tell me that no upgrades will be offered from the previous Violon model to the latest MK4.

Dear Johnk,

Something that is unique with Acapella Horn speakers is that they have the performance of a horn midrange, without sounding like a horn. This is one of the reasons why they are not super high efficient like other horn speakers.

Best Regards, Brian
I used to own Dynaudio Confidence 5 which uses isobaric woofer design. Other speakers I can think of are Eggleston Andra and Totem Mani-2. As far as I know, isobaric design needs both woofer, internal and external, to receive the same signal so they can work in tandem and produce that perfect 0.5 Q that is the ideal setting for speakers.

It doesn't hurt to try a different amp, but I don't think that will transform the sound to the degree you are looking for. My vote will be moving on to a different speaker that suits your taste instead of trial and error on modifying the speakers not to mention zero resale value afterward.
Duke, the woofers are NOT in isobaric configuration. Isobaric (as I understand it) means: two woofers, fed the same signal and wired in parallel, located very close together. At bass frequencies, the distance between the two woofers is much less than a bass wavelength - meaning no standing waves.

The woofers are about 50cm apart, with the lower woofer firing into an enclosure which is stuffed full of ... umm, stuffing. My friend (who is a speaker engineer) commented that placing them 50cm apart and running up to 450Hz between them would surely cause standing waves. I mean - the wavelength of a 450Hz wave is 76cm. You only need 1/2 a wavelength to set up a standing wave. I calculate that standing waves between 343Hz to the crossover point could potentially be supported.

He also commented that the intention of the stuffing (for want of a better word) may be for acoustic filtering. The High Suboktav is marketed as having an additional woofer allowing for deeper extension. Perhaps this was the intention.

I was unable to find the SEAS CA25ACA by google search, so I can not tell you what the T-S parameters are. However, there are some other SEAS drivers which are almost similar so the T-S parameters are probably very close.

My friend noted that the cone suspension is not very rigid, and it is very easy to make it reach maximum excursion (Xmax).

I am starting to wonder if the non-Suboktav version of the Violon may have cleaner bass. What do you think, Brian? Thank you for your suggestion of trying different amplifiers, but like I said - if the problem has been "set in wood" then it won't go away no matter how many Watts I feed it.

And BTW I am not too worried about resale value. I am a very slow upgrader and I tend to hang on to my goodies until they die. I have NO INTENTION of selling this speaker, because the mids and the top end are sensational. If I could fix the weakness, I would be very happy.
And Shane ... I have not contacted the manufacturer. Not too sure if they speak English (they make this lautsprecher in Deutschland).

I should also say: I realize that I have probably come across as being pretty negative about this speaker so far. Maybe I have been a little unfair, because in all honesty the bass does not bother me that much with 80% of my recordings.

I do know that the construction is very good. It is fully lead-lined and extremely heavy. The finish is close to flawless. And as Duke mentioned, the parts used in the crossover are of high quality.

The midrange and top end, where most of my music lives, is of supreme quality. Nothing else sings with the same delicacy and speed. That horn does not sound like a horn at all. Some other horns sound a bit quacky but not this one.

However, on some recordings the speaker is brought to its knees. Once I notice the problem, I focus on it and stop listening to music. That's not a good thing.
Amfibius, I have a simple idea that you might try, since it appears that you have access to people that are speaker savvy. See if you can arrange to put the woofers in series and readjust the crossover to support the same notch frequencies.

Tube amplifiers, unless endowed with a lot of feedback (which makes them sound more solid state) are not be happy with an 8 ohm midrange and tweeter, along with a 4 ohm bass unit. The bass will be loose and flabby sounding, owing to the increased distortion of the amplifier (NOT as popular mythology has it, lessened 'damping factor').

Setting the woofers at 16 ohms will make the speaker much easier to drive with almost any tube amp. The result will be improved detail and a greater sense of authority; this will be a load a tube amp can handle. It will also take care of the rear woofer not being crossed over.

BTW they may voice the speaker with the Einstein, but if they had done that with the woofers in series, the result would have been even better. Sixteen ohms is an easy way to get smoother sound and more detail out of any amplifier.

Keith aka Amfibius, "isobaric" means constant-pressure. It can be accomplished by many different internal geometries, and does not require that the internal woofer be fed the same signal as the outer woofer. I used to build 'em. The very-close-coupled format you describe sounds like what we used to call a "compound woofer" (often configured with the woofers mounted face-to-face), which was only used in the bass region. For operation up into the midrange, a larger inter-driver spacing was used to allow the use of stuffing between the drivers.

Ralph aka Atmasphere, one of the issues with running isobaric woofers in series is that the two woofers will have dissimilar impedance curves because they will have significantly different resonant frequencies. The inner woofer may well have a resonance an octave higher than the outer woofer. Since it's the outer woofer that we're listening to, in most cases it would be detrimental to have in effect a very high resistance in series with it in the octave above its resonant frequency. The impedance peak of the inner woofer would approximate a series notch filter.

Ralph - sounds like a great idea! I'll ask him what he thinks of it. Would the caps and inductors need to be changed as well, or only the resistors on the notch filter? Could be a good temporary solution.

Duke, very interesting and helpful comments, thank you. It appears that my understanding of isobaric enclosures is incomplete and there is a different type of isobaric as you have just described. I will have to do more reading on this - there may be a method in the madness after all.
Amfibius, Duke's comment sounds like one to be paid attention to. So if you proceed, keep his comments in mind!

The crossover parts would change as the impedance would be different and you would have to set up for the same notch frequencies, and if Duke is right, probably a notch for the unwanted secondary impedance peak.

I'm glad I make amps and not speakers!! :)
Now If that would have been on expensive speakers, I would have been seriously worried!
I thought I would weigh in here. I have a 3 year-old pair of High Violins with the single woofer and drive them with a very powerful Essence solid-state amp, actually monoblocks. Each one has 230K of filter capacitance and a 2 KVA transformer. I tried a lot of SS and tube amps on Wilson speakers I had previously and the Essence amps produced the most prodigious bass I found on the Wilsons, who are known for bass. It has been my experience that the Violins with the single woofer have a tighter, faster, more tuneful bass than the Wilsons I had. The bass is not as prominent nor as dynamic, but better integrated with the rest of the sonic spectrum. And this is with them sitting on a carpet with no spikes. I just acquired a set of spikes and will be spiking the speakers to my carpeted cement floor. I have experienced none of the discontinuity problems you describe with the twin woofers, as each instrument appears coherently in space. So whether your issues are the isobaric woofer arrangement or low damping factor of your tube amp, I am not sure. My suggestion would be to try a boat-anchor sized SS amp before I would resort to changing crossovers and woofer hookups.
Sorry for not responding for a few days. I went and did some research on this type of woofer so that I can better understand the designers intentions.

However, all my reading indicates that the inner woofer should be rolled off lower than the external one. I can not find any reference that says that running the internal driver full range, and the external driver crossed over, is a good idea.

I think I have hit the limit of my knowledge - either the Acapella designers made a mistake with the design, or there is something about this configuration which I am not aware of.
Amfibius. I was thinking that I would loan you my Gryphon Encore if you were in southern calif. but I see you're in Australia. As Rose-Ann Rosana Dana used to say, "never mind". Seriously, why don't you try a high power amp before you start chopping up your speakers. If that dosen't work then start hacking away. :-)

Borrow a pair of CAD 500MB's from your mate at audiophile or better still borrow a boulder amp from Sensis where you bought the speakers.

One thing for sure, I recently tried a Gyrphon Encore, Levinson 436's and 33h's. They certainly have more control than any tube amp. the bass control and added perceived octave the 33h's gave to my speakers were incredible compared to my tube amps. Midrange and treble were another not so clear storey :-)

Considering you can still run tubes on top, you may them have the best of both worlds.
Rlawry, The speaker you have has only a single woofer and is an 8 ohm load. The way an amplifier handles that is quite different from how it reacts when the woofer load is 4 and the rest of the speaker is 8, especially if the amp is question is a tube amplifier. Your speaker is an easier load for tubes (and transistors for that matter) so your results will be a bit different!
Hi, Ralph, thanks, yes, I would imagine my single woofer version to be an easier load, even for my big SS amp. It will be interesting to hear what Amfibus finds when he tries driving his suboktav version with a SS amp. I must admit the indicated woofer alignment seems a little strange, but I would be hesitant to alter the driver arrangement prior to trying a possible easier fix such as an amp with a much higher damping factor.
Hi all, thanks for your suggestion of trying to bi-amp with a SS amp at the bottom. If I am going to go active, I will need two more channels of amplification anyway so a beefy SS amp is on the cards.

NOW ... given that I only need to run these from 30Hz-450Hz, and I have my Cary CAD-211AE on top ... what amplifiers would you guys recommend? I was thinking of the Cary CAD-200 - inexpensive and should be "enough".
I have had BAT SS amps, the VK500 and VK600, and the bass was pretty darned good. The only thing I didn't like was the lack of soundstage size, but for bass, they are great. You might be able to pick up a used VK500 cheap. I would think just about any SS amp with a big power supply would work pretty well for bass and lower midrange, like one of the big Conrad-Johnsons, Krell, Mark Levinson, Classe, etc. The Cary would probably work, although I am unfamiliar with their new SS amps. I have had a couple of their tube jobs and they are great.
Try a loaner first to see how responsive the woofers are to SS power.
make your mind up from then. personally I don't think the CAD-200 will have enough power and control.

bel canto ref1000's are quite good and not that expensive
I thought very seriously about buying this speaker (the high version) but after extensive listening, chose not to proceed.
The Violon is somewhat of a paradox, at once offering such a level of performance in one area that other designs cannot attain, but then falling short on performance in other areas. I've found the upper midrange and HF to be stunning. I've not heard such purity in any loudspeaker before and yet, the lower mids, mid bass and bass, detract from the standard of performance set by the upper-mid and high-freq.
Your findings make sense to me, judging from what I heard for myself. Its certainly not a great idea to run drivers in full range if it can be avoided. The only reason I can think of as to why the designers implemented a crossover-less design for the bass drivers, is to re-inforce the lower midrange and mid-bass regions. strange. If you can bring the performance level of the bottom half of the speakers frequency range on par with the upper half you will have something very special indeed.
I agree with you, Oshag. The midrange and treble on this speaker are stunning. Detail in these areas is the best I have heard, bar none. Soundstaging, dynamics are state of the art. Unfortunately the bass is just ordinary. Extension is OK, speed and pitch definition are good, but the bass doesn't have the weight or dynamics of other speakers, especially the Wilson Watt Pupp 7's and Sophias I had. I spent a really long time getting my JL Audio subwoofer to integrate with the High Violins, and now the bass is liveable. BTW, I just assume my speakers have the single bass driver. On the back there is an emblem stating "High Violin 2001 Bass." Maybe someone knows which bass driver version they are. Thanks.
Well i've got in my living room a Cary CAD-200 solid state amplifier which I just borrowed from the dealer. I will unpack it later and see how well it controls the wayward woofer.

Rlawry, mine says "High Violon 2001 Suboktav". Weird - I would think that you and I have the same model being the "High" version. In any case, it is quite easy to dismantle the speaker to have a look - undo all the Allen bolts you can see on the front and top panel, then push the woofer out from the inside.

The CAD-200 is a great amplifier and definitely one of the best kept secrets in audio. Absolutely an amazing value! It has a beautiful midrange and top end reminiscent of Cary tube amplifiers. Internally it is almost identical to the CAD-500 monoblock and soundwise it is virtually indistinguishable from the monos. Just like the monos it has this really nice signature Cary midrange, but to some extent it also has a signature Cary bass. It should have better control than your CAD 211s but I don't think it will make your problem disappear. What you really need is an amp with a high damping factor that could take an iron grip of these woofers. I would look into something like the Spectron Musician III or Belles 350A Reference. I own the Belles right now and honestly, I have never heard an amplifier that can do bass better that this little beast.
Thanks for your input Jacek. I have been listening to the CAD-200 for the past few hours.

Result: it HAS removed most of the muddiness and the bass has better definition - but it still does not go very low, and the woofer is still noticably slower than the mid and the top end.

As a negative - it sounds lifeless. Not unexpected I suppose, given that it is less than 1/4 the price of the CAD-211AE, and that it is solid state not tube.

I would like to try bi-amping, but for some reason it does not like my 10m long speaker cable (!?!?!?!?) and refuses to drive it. Weird.
Amfibus, you have 10 meter speaker cables??! OK- in order to get the most out of the speakers, you will want to shorten those up- over 5 feet and most speaker cables chomp into the impact and definition in a big way! If I had known that earlier, I would have recommended getting that sorted out *before* even taking the speaker apart.

Four ohm speakers tend to be very critical of speaker cables (16 ohms OTOH *almost* don't care). IOW you won't get away with a 10 meter run, regardless of your amplifier.

So I would try an experiment wherein you temporarily use a short run of cable that is only a meter or meter and a half (so you will have to move your preamp and front end to do this), do this with your Cary 211s running full range on the four ohm tap, and see how it sounds then (and report back of course).

I understand that you may need to have your preamp and the rest of the system much further away, but there are preamps that are in fact intended for that (and that are also all tube and zero feedback, so you won't corrupt the sound of the Violins). We'll solve *that* problem *after* you establish the effect of the cable!
Ralph, I do not normally use my 10m speaker cables! The 10m speaker cables are left over from when I used to run my rear speakers from the HT and are normally in storage. In normal use - preamp-power amp cable is 5m, and the power amps are right next to the speakers with 1m speaker cable.

I only got out the long speaker cable so that I could experiment with bi-amping ... it was all that I had. I don't want to cut it either, because it is nicely terminated.

Hello Amfibius: I didn't read any of the responses, so forgive me if any of this is redundant. Your first thought about connecting the woofers in series- You'd be doubling the impedence seen by the crossover and totally changing the filter frequency. If you haven't reconciled your problem: Look into finding a Dahlquist DQ-LP1 passive high-pass/active low-pass filter(usually available used on eBay or on this site). I employed one with wonderful results, bi-amping my system since 1981('til just 3 yrs ago when I sold it for it's original purchase price). You won't need any time-domain correction with your system, so the piece will be perfect for your app. It will allow you to drive your woofers with a SS amp(I use a Hafler TransNova 9505 for my subs)and enjoy the high damping factors and fast transient response attendant, and to bypass any internal crossover to the woofers. The high-pass consists of one cap(I used 2% matched polystyrenes from Michael Percy) and perhaps one resistor(use Vishay 2% bulk foil, if needed) in parallel with the input of your amp to adjust the impedence/crossover frequency. This makes it completely invisible sonically(believe me- I'm picky)! The piece is still supported by it's designers(call themselves, "Regnar" now) and a number of upgrades are available for it. I installed gold WBT RCAs at the ins and outs very easily.
Here's a bit more support for the solution I've recommended. Read this article:( There's a DQLP-1 at auction on this site right now. None on eBay. A nice thing about the piece: If for any reason you don't want it, they are VERY easy to resell.
Amfibius, 5 meters is still *really* long. Many 4 ohm speakers will simply not allow lengths like that- Magnaplanar (otherwise a fairly easy load) is a good example- with them its beneficial to turn the amps around backwards and run 6-inch speaker 'jumpers' from the amp to the speaker (the biggest improvement by doing this is in the bass BTW, although the mids and highs get better too. This is one of the arguments for monoblock amplifiers). Seriously, 3 feet or so is about the maximum for many 4 ohm speakers.
Thanks Rodman and Ralph. Rodman, I do not think that equalization would help because (1) the rolloff at 60Hz can not be fixed with equalization and (2) the problem is with system Q, which equalization can not fix.

Ralph, I said that the interconnects are 5m long, and the speaker cable is 1m long in normal use :)
Oops! never mind... :)
Atmasphere, what exactly is it that the longer wires cause? The resistance would seem negligible. Is it C or L or something else? I'm thinking about buy a tube amp as a second system and would be interested in hearing more about how speaker wire length affecting performance.

regards, David
Hi David, When you are dealing with 4 ohm speakers and you are running a long cable, first off the resistance of the cable actually becomes part of the total impedance driving the speaker.

The second thing to understand is that all speaker cables have a property known as 'Characteristic Impedance'. This is not the resistance or impedance of the cable, rather it is the property of the cable such that it will have its best performance when terminated by a specific impedance. For example, a cable with a characteristic impedance of 8 ohms will perform best when terminated by an 8 ohm load. Its actual DC resistance will likely be quite low as will its AC impedance, however.

Even if we were talking about a cable with a 4 ohm characteristic impedance, there are no speakers that are exactly 4 ohms over their entire range, so there would be termination errors. Most cables have a characteristic impedance that is much higher than 4 or even 8 ohms so there is a greater error that results.

The error is in the form of reflected energy which smears the waveform. This increases as the cable length is increased; a simple way to reduce the error is to shorten the cable- hence a good argument for monoblock amplifiers.
Amfibius- I believe you misunderstood the purpose of the DQLP-1. It's not an EQ, it's a high-pass/low-pass filter that will allow you to drive your woofers with a separate amp. This will free your main amp of the burden of reproducing bass freqs, which cleans things up dramatically. It does have an EQ knob that enables the user to enhance the bass below about 40hz, if desired.
Couple of months down the track, and I have had the opportunity to try a number of different tweaks on this speaker. To cut a long story short: none of them have fixed the bass problem. Anyway, this is what I have tried:

- PAUL SPELTZ AUTOFORMER. Impedance multiplying device to improve damping factor. Very slight effect in the bass but detrimental to mids and highs.

- CARY CAD-200 AMPLIFIER. Enough power to poll the woofers and gave much better bass definition - but still muddy and still lacking in low bass. As a minus, substantially inferior to the CAD-211AE in the mid and top.

- JEFF ROWLAND AMPLIFIER. This is the 150W Class A/B model, before they switched to Class D. Like the Cary, this amp had enough guts to poll the woofers. Mid and top end almost comparable to the Cary CAD-211AE - cleaner, sweet instead of warm, but the CAD-211AE had more detail and better soundstaging.

- AUDIOANALYSE AMPLIFIER. This is an ancient 20 year old 75W Class A power amp. Again, much improved bass but dry in the midrange and top.

- AKSA SORAYA / AKSA GLASS HARMONY AMPLIFIERS. Beautiful amps. The Soraya was too SS sounding for my taste. The Glass Harmony was closer to the 211AE in sound but not quite there.

I think I have satisfactorily proven to myself that I can feed this speaker with enough power to poll the woofer AND still suffer from muddy bass. The next step will be to modify the woofer. Planning to remove both woofers, replace the external one with a custom woofer, bypass the crossover, and run the woofer section active.
Amfibius, based on the results that you posted, it looks like the woofers are in parallel, and so are 4 ohms while the rest of the system is 8 ohms.

If this is so there will not be a tube amplifier made that will play the bass at the right level. Transistors will do OK, but then the highs will be dry as you experienced.

I would consider putting the woofers in series if you want to use tubes. This will get the bass working right, so long as the crossover for the two drivers is the same. If not, it might be a long road ahead for you to get this sorted. Good Luck!
I have Acapella Violon 1, the predecessor to Violon 2001 which was later renamed Violon Mk. III. The difference is that Violon 1 is a bas reflex design and Mk III is a closed 3 way-system as you can read on

I bought my speakers in 2000 and at that time it did not exist an option for a version "with a 25 cm bass device (suboctave), which itself is hidden in the enlarged total volume" to use the wording of Acapella.

I heard recently for the very first time Acapella High Violon Suboktav Mk. III and it was driven by ASR Emitter II Exclusive and it had a severe bassproblem there the bass couldn't keep up with the speed of the midrange and top end rendering it unlistenable to my ears. I was told that it did sound fantastic a day earlier driven by Boulder 2060.

My integration is very good but I only have one 10" driver. As a matter of fact I often get compliments for my bassperformance.

I talked to my dealer in Switzerland and he said that there is nothing wrong with the integration of the bass with midrange and plasmatweeter in your version and that amplifiers from Cary are fast (not slow like ASR). He was convinced that you would get rid of the problem by moving the speakers and finding better positions in the room.

A friend helped me measure up my system with a microphone and by only moving my speakers 6cm further away from the backwall I got a much better integration of the bass.

I hope this helps,

I have the same speaker. I would like to look inside but the front seems to be tight were the bass is.
How to get this off?

Ragards Kladimi
Hi want to check if this thread is still active or I should start a new one.. I just got the new High Violon MKVI and after breakin period I am so happy that would like to share my experience and my findings in the past 2 months.. So I will see if this is the right place to talk about it..
the italian sound (Check for former system)
Hi Marco,
I have the High Violon Mk IV too. They are driven by Soulution pre and power amp. Like Amfibius, I found the bass is weak and muddy. I don't know if it is a problem of my amp or I still haven't broken in the speakers. I bought them for 1.5 year but hardly use them as my son is same age as the speakers.
Hi gents, I maintain the Acapella Violon mailing list. If you would like to join, send me an email. Also - there is an Acapella owners group on Facebook. To find it, search for "Acapella" on FB. See you there.
i find this very strange. As I said I did not find yet the perfect match but driven woith Levinson 333 the bass is at least very good.. Coinsidering that the speakers are ver close to the rear wall, It is probably the best I ever had.
In the next days I am getting the Einstein Preamp and will keep you posted with the results over the arc ref 3.