LOUDSPEAKER INFO

How loud a speaker plays depends on how "sensitive" it is.  "Sensitivity" is measured by determining the decibel (dB) level of a speaker when 1 watt of power is applied, measured from 1 meter away. 

This "sensitivity rating" means that a speaker with a sensitivity rating of 90 dB SPL can create a sound pressure level ("SPL") of 90 decibels with 1 watt of power measured 1 meter from the speaker.  In short hand, "90 dB SPL 1W/1M".

A speaker's sensitivity rating can be found in the owner's manual, sometimes on the back of the speaker, and often on the company's website. The sensitivity of speakers varies greatly, depending on the design and the materials used.

Single Ended Tube Amplifiers like our GLOW Amp One typically produce low power in exchange for high resolution.  To assure adequate volume while using our amplifier, GLOW recommends using speakers rated at 90 dB SPL 1W/1M sensitivity or higher.

The general rule is that, to INCREASE speaker sound output by 3 decibels, the amplifier power must DOUBLE.  Therefor, to play at 93 dB SPL, a speaker rated at 90 dB SPL 1W/1M would need 2 watts of power to play at 93 dB SPL.  And to play at 96 dB SPL, the same speaker would need double the power required to play at 93 dB SPL, or 4 watts.  This means that, with the GLOW Amp One,  using speakers rated at 90 dB SPL, you will achieve maximum volume of about 96 to 98 dB SPL 1W/1M.  This is roughly the volume level you will achieve using GLOW's Voice One small speaker.

If you need higher volume levels, simply choose more sensitive speakers. For instance, if your speaker is rated at 96 dB SPL 1W/1M, it will play as loudly with 1 watt of power as a speaker rated at 90 db SPL would play with 4 watts. With the GLOW Amp One, a speaker with a sensitivity rating of 96 dB SPL will play in excess of 103 dB SPL.

We have one customer who powers his KLIPSCH Heresy III speakers with our diminutive amp, and reports that he has no problems hosting high volume dance parties in a very large room.  How is this possible? Because the KLIPSCH are rated at 99 dB SPL 1W/1M, so with a mere 4 watts, the speakers can pump out 105 dB SPL 1W/1M. 

The importance of sensitivity ratings is sometimes overlooked. Here is how stark the difference can be. If a speaker is rated at 83 dB SPL 1W/1M, then to reach a peak of 104 dB SPL the speakers would need an amplifier capable of producing in excess of 125 watts per channel.  But, if a speaker is rated at 98 dB SPL 1W/1M, to reach the same SPL of 104 dB would require only 4 watts.  

KLIPSCH makes a number of high sensitivity speakers, including the la Scala, which with 1 watt will produce 104 dB SPL at 1W/1M !  WIth 4-5 watts, the la Scala can play at rock concert volumes.  While most speakers are nowhere near as sensitive as these KLIPSCH models, there are other high sensitivity speakers readily available on the market, made by companies such as TANNOY, JBL, CERWIN VEGA, ALTEC LANSING and others, including companies specializing in studio and monitor type speakers, and manufacturers of raw drivers such as FOSTEX and LOWTHER.

What this math means is that, if you match the GLOW Amp One with more sensitive speakers, you will find the GLOW Amp One quite capable of high volume levels, while offering incredible resolution.

There is a quiet revolution going on in the stodgy audio world.... more and more audiophiles are discovering that matching high sensitivity loudspeakers with low power, high resolution  tube amplifiers creates a dynamic combination that sounds head and shoulders above the usual high power amplifier/low sensitivity speaker combinations.  In many cases, these "low power" adherents prefer full range speakers, without crossovers, to avoid the midrange colorations that often result from use of crossovers.  We at GLOW agree that a high quality full range driver matched with a GLOW amplifier creates a stunningly realistic and detailed sound that many high power systems cannot  replicate. 

Below is a partial list of speakers that will work well with our GLOW amplifiers. Our own speakers, to be introduced in North America in 2008,  are specifically designed to match our amplifiers, and although rated at only 89 dB SPL 1W/1M, without using a power sapping crossover can play quite loud enough for most small to medium sized rooms in most circumstances.  Please keep in mind that the sensitivity of a loudspeaker also depends on the crossover type used. Typically, a full range driver will play louder than a 2-way system even when the sensitivity ratings are comparable. This is because the crossover can dissipate some of the power that might have otherwise reached the speaker.

Please note that many horn loaded speakers, such as certain models built by KLIPSCH and CERWIN VEGA,  are rated at 96 dB SPL 1W/1M or higher.  Also note that, while horn loaded speakers have a reputation for sounding harsh, we think this is primarilyy due to transistor "hash" and is not  the fault of the speaker.  In fact we have found, when coupled with a Single Ended tube amplifier like the GLOW Amp One, horn loaded speakers can sound very smooth and silky indeed.  Even high sensitivity speakers typically used in PA and DJ applications sound incredibly smooth with the GLOW Amp One.  

So don't let the relatively low power rating of our little amplifier fool you.... when matched with the right speakers, the GLOW amp will play as loud as you need it!

THE FOLLOWING LIST IS INTENDED TO PROVIDE AN EXAMPLE OF SPEAKER SENSITIVITY RATINGS AND IS NOT AN ENDORSEMENT OF ANY PARTICULAR BRAND OR TYPE OF LOUDSPEAKER.

102 dB and higher SPL with 1 watt input: 

114:    ORIS Horn   www.bd-design.nl

107:     AVANTGARDE ACOUSTIC  www.avantgarde-acoustic.de/

104:     KLIPSCH La Scala www.klipsch.com

102:     PI Speakers rated from 95 - 102 dB SPL  www.pispeakers.com/Prices.htm

 

98-101 dB SPL with 1 watt input:

101:  ZU Loudspeakers  http://www.zucable.com/all_speakers.htm

99:     KLIPSCH Heresy III    www.klipsch.com/products/details/heresy-iii.aspx

          TANNOY loudspeakers. Some models rated up to 99 dB SPL and higher. http://www.tannoy-speakers.com

          ROYAL (Italy) loudspeakers ranging from 93 - 99 dB SPL www.royaldevice.com/donna.htm

98:     BEAUHORN Loudspeakers.  www.beauhorn.com

          LOWTHER - Full range drivers rated at 98 dB SPL and up.   www.lowther-america.com

 

94-97 dB SPL with 1 watt input:

97:     CERWIN VEGA Loudspeakers - Various models rated from 90 to 97 dB SPL http://www.cerwinvega.com/

96:     ACOUSTECH Loudspeakers  HT-63, HT-64 and  HT-75   www.acoustechspeakers.com 

          OMEGA Loudspeakers - Various models rated from 93 to 96 dB SPL  www.omegaloudspeakers.com

94+   FOSTEX full range drivers. http://www.fostexspeakers.com/

 

 90-93 dB SPL with 1 watt input:

There are many loudspeakers that fall within this output range, too many to list here.

TEKTON loudspeakers (various full range models 4.1 etc.)   http://www.tektondesign.com/model41.htm

Below 90 dB SPL with 1 watt input (normally too low for our Amp One, but because these speakers are either full range or present a constant impedance load, they still work well with our amp!) :

87:     ROLE Sampans     http://www.roleaudio.com/sampan.html

           John Blue JB3     http://www.audio-magus.com/product_p/sjb3.htm