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Old 14th February 2013, 04:32 AM   #1
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Default Frequency Response Help Needed

A DIY speaker manufactures has built a pair of tower speakers.

He has used two 6.5inch Peerless 830608 drivers, one for mids and one for lows. Along with it he has used a 19mm Silk dome tweeter.

The technical specifications he has provided are as follows :-

Design 3 way ported box
Drive units LF: 165 mm (6 1/2") Peerless® with
HF: 19 mm (3/4") Silk dome
Frequency response at 15° horizontally off axis: ±3 dB 120 Hz - 27 kHz
Crossover frequency 2.8 kHz
Amplifier requirements 15 - 100 W
Sensitivity (2.83V/1m) 90 dB
Maximum output 108 dB
Impedance 8 Ohms
Weight 12.1 kg

I haven't auditioned the speakers yet as he is located in a very distant city.

But I have a question regarding frequency response.
In his specs he has mentioned frequency response to range from ±3 dB " 120hz - 27khz "

Considering the low frequency I want to ask that does this above stated figure means that these towers wont be able to produce low end sounds below 120hz? Normally the tower speakers I see in market usually have a Frequency range as low as 40Hz. I am a little confused with his specs.

Can someone on the forum clear my thoughts on this?

By the specs he has provided, does it means his towers will produce just the mid bass? and No Sub-bass? I dont like to hear the boomy bass at all. Will his towers sound boomy? or has he provided / calculated the Frequency response of his speakers wrongly?

Can someone calculate and tell me What would be the frequency response at ± 6dB?
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Old 14th February 2013, 09:33 AM   #2
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what i suspect is that it refers to the deviation from average level with the range he quotes. I.e. It is flat, plus or minus 3db in the range quoted.
Balancing the things I must do, with the things I'd like to do...This is a skill (or a luxury) I do not possess.
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Old 14th February 2013, 09:46 AM   #3
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Going by the specs mentioned, what conclusion do you make? Will this produce enough tight punchy sub bass?
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Old 14th February 2013, 09:58 AM   #4
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...and there are many more graphs that show how a speaker
behaves, nonetheless the environment must be indicated as reflective, partial-reflective or nearly anechoical, or anechoical; there's the 'decay-in-time' which is the waterfall response, then the impulse response; those are taken with pink noise . All those operations are made available trough the use of a microphone which re-converts air pressure variations (...sound) to electric form. The wave is then analyzed with the aid of the Laplace and Fourier transformation which defines the algorhythms necessary to
change from the time domain to the frequency domain.
So a good ( and possibly certificated for a non-DIY purpose ) measuring setup is needed, IF ......
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Old 14th February 2013, 10:21 AM   #5
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Location: Sydney
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Ask to see the actual frequency response curve that the specs were derived from. This will tell you more. It may in fact have a hump in the bass in that is more than +3db just below 120Hz and then starts to drop off, it may also be -3db and dropping at 120Hz (though if it is using 6.5" drivers this seems extremely unlikely).

See the attached graph for a visual example.

If you take the average point as being 78db then the speaker is +- 2db from approx 150Hz to 18Khz.

Note that this was a gated measurement and below about 250hz is meaningless, the speaker is in reality around 3db down at 80 Hz.

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Old 14th February 2013, 01:00 PM   #6
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i think the info is vague largely as the author does not want to give data below 120hz since it would be misleading, the end users room gain etc being unknown to the author.
Balancing the things I must do, with the things I'd like to do...This is a skill (or a luxury) I do not possess.
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