Category: Technics

Buying a garment online is easy: you see the look, you know what material it's made of and you know your size. But buying an audio system? You can't know how it sounds. Even if we were to offer you sound samples to download, you wouldn't get any better listening than what your computer's speakers allow in terms of sound quality.

The purpose of this short article is to give you a visual idea of the sound of the devices leaving our workshop.

• Response curve of an audio system
• Two elements for comparison
• The quality of the speakers and their installation
• The digital filtering
• The High-Fidelity line
• Other factors

Response curve of an audio system

The response curve of an audio system is a graph representing the sound level achieved as a function of the frequency of the sound to be reproduced. It can be obtained by sending a signal of equal energy at all frequencies to the loudspeaker and analyzing its reproduction.

For example, for the Monacor loudspeaker studied in this article :

As you can see, reproduction is not perfect over the 20Hz-20kHz audible range. Low frequencies are cut off (here around 100 Hz), as are high frequencies (here around 8 kHz). The central part is uneven instead of strictly flat (pronounced dip at 1 kHz and oscillations after 3 kHz).

When a loudspeaker is mounted in a cabinet to form a closed speaker, other phenomena come into play and modify the response curve. As the model of the closed cabinet detailed in this article shows, the bass is cut off at higher frequencies and the diffraction phenomenon causes new accidents:

This is a far cry from a flat response over the entire audible range (20 Hz to almost 20 kHz)!

Two elements for comparison

All the response curves published below were produced under the same conditions. They are the result of a combination of several measurements and mathematical processing designed to eliminate the effects of environmental reverberation.

Let's take as a starting point a low-end loudspeaker mounted without any particular care on a radio from the 50s:

We note that the bass cut arrives very early (around 200 Hz) and that the treble is uneven and very attenuated (-10 dB around 1500 Hz and even worse beyond 5 kHz). The sound is only well balanced between 200 and 800 Hz! However, this curve is representative of devices sold by some of our competitors...

Let's now consider the more desirable sound of a connected loudspeaker of comparable size to our radios: the Harman Kardon Onyx Studio 8. Measured under the same conditions as above, its response curve looks much better:

It's clear from this graph that listening sensations are better: bass is cut at a much lower frequency (around 50 Hz), and treble around 8 kHz, without being totally crushed at high frequencies. The midrange is also noticeably flatter.

However, the bass bump is significant (+6 dB) and may be disturbing for some listeners or musical styles, and the drop in sound level at high frequencies occurs very early.

The quality of the speakers and their installation

Since 2016, we've been constantly striving to improve the systems leaving our workshop. The first step is to select speakers that are both of good quality and suitable for the atypical cabinets we use. Then we have to find a way of integrating them neatly into the cabinet, to avoid the parasitic vibrations that will spoil the sound.

Here's what we come up with for a medium-sized radio set Ducretet-Thomson L325 :

The bass cutoff is a little high and the high frequencies are not yet top-notch, but we have a good base to work with.

The digital filtering

Knowing the response of the loudspeaker mounted in its vintage cabinet, we can now seek to improve it. To do this, we use an electronic board on which we program a series of filters to correct the system's response. In the example above, we'll need for instance to create a combination of filters to raise the sound level between 2 and 7 kHz. The signal sent to the amplifier will thus be increased in this frequency range to compensate for the weakness of the loudspeaker.

We finally get for the Ducretet-Thomson L325 :

This corrects the midrange dip and extends the bass and treble response. If you're thinking of turning to the competitors, ask them for the response curve of their products!

The High-Fidelity line

Our sets in the "High-Fidelity" range are upgraded to two-way speakers (bass-midrange + treble), or equipped with a high-end, large-diameter full-range driver. The aim is to achieve the broadest possible response, from deep bass to extreme treble. These loudspeakers are selected after digital modeling of the cabinet to predict their optimal characteristics.

We then measure the woofer and tweeter responses separately. Specific digital filters are optimized to blend the two signals harmoniously (frequency crossover).

This is followed by the digital filtering process described above, but with a larger number of filters. The result for cathedral radio Trialmo 520 HiFi :

The corrected response curve is very flat from 60Hz to 18kHz, so the device has nothing to envy the Harman-Kardon loudspeaker!

Sometimes you want a deeper, fuller bass. The switch on the rear panel activates the Superbass mode:

In this way, it is possible on systems with this function to obtain heavy bass (which in this case goes down to 45 Hz). But unlike the Harman-Kardon loudspeaker, it's not compulsory!

Other factors

The aim of this article is to give an idea of the sound quality of our devices, without getting too technical. There are, of course, other parameters that we take into account to optimize the sound quality of our devices. These include :

• The phase of the sound, which should not vary too much across all frequencies.
• The choice of amplifier also plays an important role, particularly with regard to distortion.
• The system's damping time at different frequencies, which must not be too long to obtain a clear rendering of the sound track.
• Or the maximum sound level the loudspeaker can deliver.

More and more wireless speaker manufacturers are turning to WIFI solutions for music streaming, while the standard has long remained Bluetooth. At tsfVintageRadios, the vast majority of our radios, record-players and turntables also have a WIFI connection. I will summarize in this article the main advantages of this mode of audio broadcasting controlled by a phone or a tablet.

Oceanic Record-Player Surcouf RP WIFI

TSF Radio Minerva 557 WIFI

Philips AG2140 turtable WIFI

Art-deco Speaker WIFI

1. WIFI and Bluetooth: a common point
2. Bluetooth: limited range and speed, busy phone
3. WIFI: three-way conversation
4. Audio over WIFI: the advantages
5. Supported music platforms
6. Multiroom !
7. WIFI versions

WIFI and Bluetooth: a common point

Regardless of the technology you use, your phone will talk to the wireless speaker using 2.4 gigahertz radio waves. These waves are the same type as light waves, but their frequency (the speed at which the electric field oscillates) is much too low to trigger a reaction in the cells of our retina.

Bluetooth: limited range and speed, busy phone

When you connect to a speaker via Bluetooth, the phone establishes a direct connection with it. This is an advantage for a roaming solution, if you want to be able to use your speaker without access to a WIFI network, at the beach for example. It is less so for the devices in our collection: who would have the crazy idea of taking a several kilograms 65-year-old radio in excellent condition on a picnic?

However, this direct link implies that the two connected devices, each equipped with a small antenna, must remain close to each other to be able to exchange data. The range of a Bluetooth connection is therefore rather limited, about ten meters, or even less if the environment is cluttered with obstacles (walls, radiators ...). Everyone can see this by noticing the degradation of sound quality when moving the phone away from the wireless speaker.

The direct link also means that the phone is responsible for transmitting the data to the Bluetooth speaker. It is therefore up to the phone to read or download the music file, then encode it and send it.

In fact, your phone is under a lot of stress when you use it to play music:

• With the number of operations it performs every second and the energy it uses for transmission, the battery will run down quickly
• If it is not powerful, it will have to transmit a less detailed sound. This will result in a loss of sound quality even if the loudspeaker is equipped with a good amp and quality speakers.

Finally, the data rate (number of zeros and ones transmitted per second) of a Bluetooth transmission is limited. Although it has been approaching the speed necessary to obtain CD quality in recent years, it is still well below that of a WIFI connection.

WIFI: three-way conversation

To establish a WIFI connection between them, two devices must be on the same local network. The smartphone and the wireless speaker must have been configured beforehand to recognize the router and provide it with the right password. There is therefore no direct connection: the router is the intermediary for all exchanges between the two devices. In other words, by opting for WIFI, we give up having a mobile device.

Audio over WIFI: the advantages

Now that the phone and the wireless speaker have access to the box, we can imagine other ways to listen to music. To stream an album from a music platform such as Spotify or Deezer, the smartphone can tell the router to send the music to the wireless speaker.

The router can then download the streaming music from Spotify and feed the wireless speaker directly: the phone is no longer in the loop! As a result, the major drawbacks of a Bluetooth transfer disappear:

On one hand, the phone no longer downloads or transmits music: its battery does not run down! It only serves as a remote control and therefore only intervenes briefly to give orders. More or less volume, play a song, change the artist ...

Moreover, no more range problems. As long as your WIFI speaker remains connected to the box, the music continues, even if you turn it off or leave the house.

The same goes for the connection speed: your box is able to send much more information per second than your phone, allowing you to use music platforms offering very high quality.

This is also an opportunity to highlight another advantage that WIFI audio has over Bluetooth. During a Bluetooth listening session, all the sounds from the phone are transmitted to the speaker. Your music is decorated with the beeps of SMS notifications, new WhatsApp conversations or likes of your latest Instagram post. If these noises interfere with the music, the worst thing is to receive a call! The music gives way to a ringtone and your choices are reduced to cutting off the Bluetooth connection and the music, or worse, having everyone listen to your conversation.

If you have digested how WIFI audio works, you have already understood that all these nuisances disappear. As your phone has given the order to the box to play a certain song on the speaker, the music is independent of your use of the phone. You can receive calls without ruining the sound environment!

Supported music platforms

The vast majority of our devices have in addition to Bluetooth a WIFI connection compatible with Airplay, SpotifyConnect, and DLNA and supporting iTunes, Spotify, Deezer, Tidal, Napster, Qobuz, Amazon Music, Pandora.

The dedicated application also allows you to listen to any radio or web radio station via WIFI.

Multiroom !

Last but not least, WIFI streaming opens the possibility of synchronous wireless broadcasting on several devices (multiroom). And that includes your vinyl records! Place them wherever you want, connect them to your home network, and enjoy your synchronized music throughout the house.

This technology is the subject of another article: Multiroom - An explanation in pictures.

WIFI versions

We have recently made the choice to change the WIFI system. From now on :

• our record players can play vinyl records in multiroom, a world first for vintage devices!
• we provide WIFI adapters we offer boxes that allow you to convert your old audio devices and Hi-Fi systems into WIFI speakers compatible with the new versions of our radios and record players. Any audio device you have at home is suitable: it just needs to have an auxiliary plug. A practical and economical way to modernize your installation!

Check the Frequently Asked Questions for more details. Please contact us to help you in your choice.