Our Thoughts about:

Hi-efficiency, No Crossover, NO Feedback, TWO WAY SYSTEMS, BI-WIRING, Bi-AMP, Horn SUBWoofers in Bricks, 10 Hz full power, cables and others

(this section is a simple approach to our philosophy towards speaker manufacturing and to the choices made to build the AUDIO ROOM shown in the web , it doesn't introduce maths concepts and is intended for not hi-skilled people and for the DIY people, however can maybe of help to anyone, we recognize that due to the complexity of the subjects considered, it is not possible to completely detail them all thruout without enter deeply in maths concepts and relationships between one topic and the other)

The following paragraphs explain the approaches to reach "real live play" music out from an Audio System for indoor use, where the sound pressure levels can reach up to 105 - 110 dBs (depending on conditions (type of music), listening distance and room absorption) and where distortion can be considered not significant to human ears.

A "Good Audio System" (GAS) should have the following features:

(we do not consider an audio system as a mean of reproduction of music [you can use a cassette player for this and it's OK for us too - we still also use cassette players in cars or walkmans] but as the "live music itself" where any kind of people at the end can say: "here is better than live play").

  1. Hi sound pressure levels (without earable distortion on peaks)

  2. No ear annoying. This should be not only for one minute listening but starting suddenly and up to two hours listening (as live play - for any kind of instrument or type of orchestra or human voice)

  3. Hi velocity response (as live play - for any kind of instrument or type of orchestra or human voice)

  4. Very Hi Dynamic (as live play - for any kind of instrument or type of orchestra or human voice)

  5. Capability to understand not only if a piano or electric piano is playing but the brand of the piano (the type of a piano can be understand also in a portable cassette player, the brand it's a little bit more difficult).

  6. Capability to avoid the introduction of INTERMODULATION distortion (TIM) and SOUND COMPRESSION

  7. Large audio stage (as live play - for any type of orchestra)

  8. Perfect central focusing (as live play - for any type of orchestra with singers also or central instruments)

  9. No coloration. Use of materials that do not introduce resonances that modify sound quality

  10. Capability to avoid the introduction of Harmonic distortion (THD). Try to have flat frequency response

  11. Wide frequency response for human ears

We consider the aboves as important as we have numberd. So hereby we will explain our thoughts for the reason why we need:

HI-EFFICIENCY, NO FEEDBACK AMPS, NO CROSSOVER filtering into the 50-5000 Hz, ONLY TWO WAY SYSTEMS, NO MONOVIA, NO Horns for MIDRANGE Frequencies (from 500 to 4000 Hz), BI-WIRING or BETTER BI-AMP or MULTI-AMP to get:

  1. Hi sound pressure levels. This can be obtained only with HI-Efficiency. This does not consequentely mean the full use of horns.

  2. No ear annoying. This can be obtained ONLY with the use of AMP WITHOUT FEED-BACK and Bi-WIRING or BETTER BI-AMP

  3. Hi velocity response ( ). This can be obtained ONLY with the use of AMP WITHOUT FEED-BACK and speakers that do not use compression (closed boxes for low and mid ranges and horn on the mid ranges)

  4. Very Hi Dynamic ( ). This can be obtained ONLY with the use of AMP WITHOUT FEED-BACK plus choices on the type of speaker.

  5. Capability to understand the type of brand of a piano is playing (or else a brand of electric guitar with its type of amplifier connected to it). This feature is related not ONLY to the very flat frequency response of the system but to the capability of the audio system to AVOID TO introduce any compression on the sound and substantial modifications to it. This can be obtained ONLY with speakers WITHOUT CROSSOVER.

  6. Capability to avoid the introduction of INTERMODULATION distortion (TIM) and SOUND COMPRESSION.This involves the use of all the followings: AMP WITHOUT FEED-BACK, NO-CROSSOVER, BI-WIRING or BI-AMP and the right speaker cables.

  7. Large audio stage: cannot be reproduced without a central channel. This can be easyly obtained by the stereo system we already have [it does not matter the type of source: CD, vinil, DAT or else). The central channel of an audio DVD or SACD will be of course WORST. We will talk later how to do it (not with a MONO central channel)

  8. Perfect central focusing: as above - you can get focusing without a central chennel but you won't get large audio stage for classic orchestra or even for a live rock pop/jazz or blues group)

  9. NO coloration. This topic need not to use HORNS in the Midrange, driver frontal loading by means of materials as metal, plastic or similars.

  10. Capability to avoid the introduction of Harmonic distortion (THD). No coloration. Trying to have flat frequency to reduce at minimum big differences on the response. If to obtain these reductions it needs to intervene in an electronic way, we do not consider it as a GAS (the reasons will be explained later)

  11. Wide frequency response for human ears and not for dogs (do not need to have 1 MHz or 50 KHz flat frequency response on amplifiers).

Hereby we give somemore detailed explanations of the above points. (As the web is continuously updated, the points not already explained will be in the next future. Keep in touch or e-mail to us)

1 - Hi sound pressure levels

To get HI sound pressure levels without considerable distortion it is not possible to use ISODYNAMIC or ELECTROSTATIC speakers. These normally have:

The same is for a MONOVIA speaker that have the following:

The choice then to obtain:

is to use a TWO WAY SYSTEM where the low range will have to rise up to at least 6 Khz (here we have all the voice and the most important part of the sound of near all instruments) using a customed WOOFER and the high range integrated by a HI-HORN up to 20,000 Hz that does not use of a frontal phaser.

A system as this can reach up to 95-98 dBs sensitivity.

To get more we need to use multiple drivers

2 - No ear annoying

To avoid this we msut avoid to use:

3 - Hi velocity response

To get HI velocity response it is not possible to use speakers with crossover and amplifiers that use feed-back:

In a system with NO-CROSSOVER and NO FEED-BACK these problems can be considered of minor worth or at least not even considerable on very Hi efficient systems. Moreover:

There are several physical reasons for this and the results depends a lot on the type of system used. The interconnecting cable between amp and speaker plays also a very important role.

To understand how much a speaker cable can affect sound quality we will have observe some simple rules. These can totally apply to systems WITHOUT FEEDBACK (Feedback Systems in fact have many more problems affected by the type of cable connection and type of speaker chosen and the following rules apply only in part):

3.1 PROBLEMS of FEED-BACK amplifiers

1 - Any Hi-fi Amp does not feed a single resistor nor single capacitive or inductive load (as normally measures are done during AMP tests).

2 - A woofer (out of his simplified equivalent circuit) when fed by an electric signal becomes an AC motor that produces energy (electric power). This energy is considerably high (bigger is the woofer more is the energy) and is sent back to the AMP and to other drivers in the speaker (tweeters and so on). Woofer is not a resistor nor single inductance or capacitor. [The considerations made for woofers can be applied to other drivers into the speaker towards to woofer and amp output].

3 - Woofer moves very very slowly in respect to the signal fed by the amp (amp is an electronic device while woofer and other drivers are electro-mechanic). This situation, plus the reasons explained in #2 above produce sound compression.

- FIRST CAUSE OF SOUND COMPRESSION: AMP velocity too HIGH

The best audio system that can be set up with the uptodate tecnology could be the one where the AMP velocity (this is is normally very high because proportional to its frequency response) is roughly the same of the drivers used into the speaker (this is normally very slow because electro-mechanical devices), so nearly impossible to obtain. Any Amp is still is too quick (hi-velocity) and the drivers still to slow. Even if many of you won't believe this, to achieve a system that we can say works good in audio environments, we should have an AMP that let the speaker working by itself without bother him too much. To understand this concept let's consider that the Amp starts to feed a first VERY FAST signal (a sine single wave burst) to the speaker and the speaker (later on because is slow) will release it to the air (The concept is that the two things do not exactly run at the same time so not in real time). Here is where the problems arise due to "compression of sound". If for istance the amp will try to feed a new second different burst signal to the speaker will force the speaker drivers to reproduce it. This of course means that the drivers into the speaker will try to correct the old situation (while they were still releasing the first signal to the air) into a new situation. The result is that the drivers will not finish to do their first job (they have not reproduced completely the first burst sound) trying to start the second one (riproducing the second burst sound). The result is that the driver into the speaker has not been able to reach the maximum escursion (forward and back) to reproduce the first sound fed. So it will be for the rest over on.Of course this is a very flat explanation of the concept but at the end this is the first type of sound compression introduced.

The woofer moreover produce energy that is sent back to the amp. This is of course completely out of phase (it depends on woofer velocity that in any case is tenth of times slower than Amp velocity). Tweeter moves faster and its out of phase signal is summed to the out of phase signal of the woofer and to the signal present on the speaker input at that time fed by the amp. Finally during any music program reproduction there are (in a two way speaker system) at least 3 main signals on the speaker connectors produced by different sources (woofer, tweeter and amp) all out of phase one to the other and with different amplitudes.

4 - It is not right to say that the output resistance of an amp is ZERO. This is only theory. Even if you have a lot of feedback the output resistance has a real value, could be low but a value. This means that the energy sent back to the amp by the woofer and tweeter is not really all short circuited. This small amount creates a lot of problems to feedback Amps. It really does not do to very good NO FEEDBACK AMPs.

- SECOND CAUSE OF SOUND COMPRESSION: AMP FEED-BACK

5 - The AMP feedback (finding a different output signal in respect to the one fed) will (try to) correct the situation sending back to the amp input the feedback signal from the modified output. Here the mess is then made. Here it is where the higher sound compression start to come from and distortion arise. This distortion is never measured but definitively heard by human ears as high annoying material. Rising feedback it does not reduce the problem because: even if it is true that higher the feedback is, more these out of phase signals will be reduced it is ALSO true that more correcting signal will be sent to amp input. Then distortion still will rise. The input signal will then be modified and re-amplified.

6 - It is true that a speaker with crossover will reduce the amount of energy sent back by the woofer. A coil in series to the woofer has a minimum of resistance. This helps reducing the problem, but crossover kills sounds quality in terms of music attacks and decays and modifies the signal itself.

- HOW A CROSSOVER MODIFIES SOUND QUALITY

To understand this concept let's take as an example a simple crossover at 6 dB/slope with a coil in series to the woofer and capacitor in series to the tweeter designed for a certain crossover frequency (ex: 3 Khz).

NOTE: There is no speaker with crossover in the world that reproduces music attack and decays as real live play does. No crossover speakers are normally the ones that most often reach this task near reality. [Electrostatic speakers even if have a good approach to the topic overmentioned do not have sufficient dynamic to reproduce live play (orchestras or drums sound pressures). There is no speaker of this kind that can reproduce 110dB/1W/1m. The same is for very low bass response (below 30 Hz)]. MONOVIA speakers have normally have lack of highs and lows and normally have to be Backloaded a lot to reach a slight bass response increase and front loaded to try to reduce peaks or else and in any case integrated by a tweeter on the high end. A monovia also have only medium efficiency].

7 - Sound compression can be completely avoided by feeding drivers (tweeters and woofers) with different Amps.

SOME RULES ON SPEAKER CABLES and AMPLIFIER INTERFACE

8 - Higher is the resistance of the cable, less the amp will have problems concerning energy sent back. This is GOOD for the AMP. This point does not introduce distortion but it reduces instead distortion produced by the amp.

9 - Higher is the resistance of the cable, higher will be the power loss. This is BAD for the speakers if is too much. This point does not introduce distortion but it reduces instead.

10 - Higher is the resistance of the cable, higher is normally the serial inductance (and parallel capacitance) and this will cut hi-frequency. BAD if it is too much. This point does not introduce distortion but affects frequency response in terms of hi-frequency roll-off.

11 - Higher is the resistance of the cable, less it will be the capability for the amp to force the woofer to follow the amp signal (damping). This is both GOOD and BAD. Good because the woofer MUST do its own electromechanical cycle. BAD because it reduces the woofer damping factor. In this case a good damping of the woofer can be achieved either rising driver B*L factor and not using only amp output resistance by itself towards 0 ohms). Woofer MUST then be accurately designed for flat frequency response and to control break-ups.

12 - Lower is the resistance of the cable, worst it will be the sound because the amp will have problems. This is VERY-VERY BAD for FEED-BACK AMPs. This point introduces a lot of distortion normally not measured by any set of instrument (nobody does measure amplifier THD and TID with the speakers of the customer connected to it but with a dummy load). Normally audiophiles listen to music with their speakers and without dummy loads. These problems are considerably avoided with NO feedback Amplifiers.

13 - Flatness on the frequency response can have a minor importance if it is not considered together with the room environment where the audio system works. Flat frequency response of speakers measured on axis at 1 meter normally fools the FINAL AUDIO system response. As an example Perfect Bass-reflex response designs of speakers many times do not sound good into a in-house environment (frequently people have to reduce bass response due to internal room resonance (standing waves normally below 200 Hz) by using some dumping materials into the reflex hole. An in-house frequency response measured in the listening point normally have amplitude range that varies from +/-15 dBs in the range up to 500-800 Hz. It is foolish to look at measures to correct even one or two dBs if room environment is not set for best results. In the medium frequency range it's a different story. In the High end of the frequency range there can be a lot of differences in terms of audio energy produced into the room if drivers are horn loaded or not.

Normally many speaker manufacturers use crossovers and correcting RLC cells to flat drivers response killing attack and decay music response. A good speaker MUST have both good flat response plus perfect attack (extreme velocity) and decay response. This cannot be achieved with Crossover.

A start can be to try to reduce the problems where distortion is generated by interfacing the audio systems chosen. This can also be made by designing the right speaker cable knowing the type of amplifier used.

CABLES

14 - It is not true that the best cable is the shorter cable or NO cable. Speakers are designed to use cables for connection and the best cable at least is the one used to design and fine tune the speaker by the manufacturer.

The cable is a media that MUST do 2 things and not only 1 as normally thought.

14.1 - INTERCONNECTING two completely different world: The AMP and the Speakers ( Motors that produce energy)

14.2 - DIVIDING two completely different world. More are divided the best it is.

The best speaker cable is not the one that gives more good bass response or more high response to the audio system but is the one that can perfectly interface the speaker and the amp chosen in terms of trying to reduce at its best all the overmentioned problems. It is clear that this will be a BIG overall compromise between:

14.3 - Type of amp

- feedback or not

- transformerless or not

- other factors

14.4 - Type of speaker

- crossover or not

- MONO or multiple way

- MONO, Bi-wiring or Multiple Wiring

- type of woofer involved (B*L factor)

- Type of woofer loading

- Velocity of drivers

- others factors

15 - Shielded cables help a lot to reduce electromagnetic influence between tweeter and woofer signals if a BI-Wiring system is used. It is very important at least to connect the amplifier in this modality as to obtain the maximum from the speaker in terms of sound reproduction.

HORN SUBWOOFERS MADE IN BRICKS

In Italy all the houses are made in bricks and not in wood as normally made in other countries so it is easier to do and sometimes cheaper. But out of this the very big problem is the compression chamber of the horn. The pressures here are very high and the compression chamber itself will resonate and the same is for the back volume of the SUB Woofers. This will give big problems. You could surely ear a BOOM BOOM coming out there instead of coming from the mouths (with its own coloration) and this is not controllable unless you are able to hold and fix steady everything. With very very big SUB horn this is quitly impossible.

Where we did put wood (the closures of the compression chambers) 2" thick multilayers reversed one to the others and 2 " anti seronance material fixed on the wood itself plus everything fixed on the 6 mm metal borders also fixed into the concrete borders with N.16 X 8 mm screws per each closures ( 4 closures) plus a fixing in the in the center of each closure towards the underneath floor, well we had problems. To make the closures not moving ( nearly at all or let's say no more earable) and remove resonances we had to put 700 Kg staff on it, it is the pink pavement you see in the photos with a carpet on the top.

Remember this and be careful in building big sub horns.

10 Hz FULL POWER

An error normally made is to consider the speaker by itself (or the amp or the cable). There is people that do not sleep at night because still is not satisfied of what he has made or bought. The final result of an audio system is proportional not to the money spent to make it, but to the amount of thinking and search one it does considering from the start the ALL lot of components he must at the end stuck together. As normally HI-END Audio manufactures do not provide everything, and as people likes to put "this" connected to "that" because " have read here and there" or "heard somewhere else" still the problem to get a very good final result is far away to achieve.

Many times to build bass horns everybody follows manual and books (and thats good to do, theory always teaches, experience is something else), we also have books but experience is much more worth and in this case the horn MUST not be seen by itself.

Talking about a BIG HORN SUBWOOFER there is something that I think people normally forget or do not take into consideration (and maybe on books you don't find) that is the dimension of the room and the position of the horn mouths toward the listening point plus the shape of the room. The second thing is that the bass or sub horn calculations are normally valid (as usual) in open air and that the room itself, if correctly used and shaped, can be considered part of the total horn below frequencies as 20 Hz.

Due to these factors a sub-horn that is designed on paper to have the low frequency cutoff at 30 Hz could reproduce also 10 Hz as well even better than 30 Hz ( I mean in amplitude) if the mouth of the horns are placed in a correct way (we are talking of sub horn not bass horn - a bass horn is normally designed to be placed where the loudspeaker is, reproduces all the bass frequency range and is cut in the range of 350 - 600 Hz, a sub horn instead will reproduce starting from "as low as possible" up to 50- 80 Hz only and can be placed where you like (if you can of course) and the room dimensions are effectively important in the very low range, so it is for the mouth positioning. If you try to calculate (for our Audio Room) the lenght of the wave starting from the throat of the SUB horn to the listening point you will understand what I mean. If you have been looking seriously at the final photos of the Audio room, maybe you will have also noticed that the frontal exponential panels of the frontal speakers are placed where the horn mouths are. These panels effectively continue the horns after sound comes out from the floor at frequencies below 25 Hz. On the ceiling (on the top of the mouths) there is another folding too. On the listening position there is the last folding on the top of the sofa (maybe this is not visible on the photos). Other foldings are in the back corners.

It is important to get the maximum from the room. In our room, when you play Jurassic park cinema track, when there is the dynosaurous coming, you orribly feel all the walls crashing down (many people got scared, now I normally ask if they are ready to be scared) is something that you cannot even get in a cinema show, this is because all the frequencies (low bass also) are focused all to the listening point, while in any cinema show you normally are not able to do it. The full 10 Hz frequency response depends on this. 5 Hz we cannot measure, but you can feel them easyly on your body. 30 Hz is lower in amplitude because of the phase of the emission made by the frontal speakers bass horn. Nothing in this Audio room has been done by a case and this is one of the topics that has been well thought before building it.

If you have a look to the room again you will notice that it looks like that horns are continuing after the sub horn mouths for 10-20 Hz frequency range.

The room itself as it has been shaped is a horn below 20 Hz, then actually the holes in the floor are not really the final mouths below this frequency and the length from the throat to the listening position is half of a wavelength of 10 Hz. That is why we are getting response down to 10Hz better than 30 Hz.

Aliante s.r.l.

Viale dell’Industria 19

21052 Busto Arsizio (VA), ITALY.

Tel. +39 0331 354070

Fax. +39 0331 342445

e-mail: aliante@royaldevice.com