Definitive Technology D7 User manual

Preventing
Speaker Damage
In order to make sure your speakers are properly protected, you must see to all four fields:
1) channel levels 2) bass management 3) equalizer, and of course 4) overall system volume.
I. Channel Levels
1. Check the channel levels so that no channel level is boosted very much over the others.
In order to do this you will need to use the manual test tone option through your AVR
receiver’s set up menu.
2. If your system requires a difference of more than a couple of dB in order to be balanced,
try lowering most of the channels instead of raising up the level of only one (in other
words in a 5.1 if you raise the level of only one speaker you get the same effect as if you
lowered the level of the other four speakers).
3. Each 3dB boost will cause that channel to require double the amount of power.
a. So at a 0dB channel level a given speaker gets as much power as every other
speaker in the theater.
b. At +3 dB that one speaker gets twice the power as the other channels.
c. At +6 dB that power requirement is doubled again.
d. And so on, with each additional +3 dB requiring double the power.
4. So if your system is humming along at 75 watts with one speaker set to +3dB then that
one speaker require 150 watts while the others require only 75. If the channel is set to
+6dB then that one speaker will require 300 watts! What then happens is the AVR tries
to provide enough power and instead ends up producing lots of dirty distorted and
clipped power, which in turn becomes excess heat in the speaker. And leads to damage.
II. Bass Management
1. If using ProCinema or Demand bookshelves, your speakers must be set to “small” in
your AVR.
a. You must also set the crossover. See appendix at the end of this document for
the recommended crossover levels for many DT speakers. If your model is not
there you may contact us for a specific recommendation.
b. Contact the manufacturer of your AVR for advice on how to access the crossover
settings in the AVRs set up menu.
i. Some manufacturers will not ask for small or large. Instead they will ask
for either “full bandwidth” (large) or for a specific frequency (small).

Preventing
Speaker Damage
III. Equalizer
1. The EQ may be selectively boosting certain frequencies beyond the capacity of the
AVR to cleanly play or the speaker to clearly resolve.
2. Increasing EQ at requires more power at the frequencies addressed. This can cause
the amp to clip at a lower volume. This can be true for higher frequencies.
3. ProCinema, Demand Books, are not capable of replaying low bass frequencies, so
boosting low frequencies to “improve” the sound quality may be dangerous for the
speaker.
4. Generally speaking we have found that a flat EQ is best!
IV. Overall System Volume
1. Every combination of speakers and amp or AVR has a maximum volume beyond
which that combination is unable to safely play.
2. Use Logarhytmic Volume Control if possible. This style of volume indicator starts at a
very low number [-80] and goes up beyond zero to a small positive number such as
[+15]. If your AVR does not display volume this way contact your AVR manufacturer
to determine how to change it.
3. It is essential that the volume always remain on the quieter side of zero.
4. For instance my amp at home starts -65 and goes up to +10. For most sources my
maximum comfortable volume is between -15 and -10 dB; any closer to zero and the
AVR runs out of power on most sources.
5. Logarythmic volume controls are helpful as they indicate a maximum saturation
point beyind which the AVR should never be pushed: 0 dB. However with many
sources the saturation point will be before 0 dB, usually between -15 dB and -10 dB.
Appendix I: Crossover Settings
Speaker
Crossover
Speaker
Crossover
Speaker
Crossver
ProMonitor 6D
Small; 120 Hz
ProMon. 1000
Small; 80 Hz
Demand D7
Small; 80 Hz
ProCenter 6D
Small; 120 Hz
ProCenter1000
Small; 80 Hz
Demand D9
Small; 80 Hz
ProMon. 800
Small; 100 Hz
ProCenter2000
Small; 60 Hz
Demand D11
Small; 60 Hz