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Full range active speaker
Full range active speaker
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Old 21st August 2009, 03:24 PM   #1
zebra100 is offline zebra100  United Kingdom
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Default Full range active speaker

Hi all,

I am thinking of having a go at a pair of full range active speakers based around an Audiosector LM3875 Gainclone kit. Any experience/thoughts would be much appreciated.

18mm MDF cabinets with a steel or aluminium sub chassis for the amp/psu section will be the chosen medium. I haven't settled on a driver yet, but I have a couple of ideas.

For the amps, I intend to use 18-0-18v, 120VA transformers (rail voltage around 25V).

I am just at the design/exploration stage of the project, so I won't be building anything just yet. I may even end up using the LM3875 modules and transformers from my power amp to save on cost (being a cheapskate).

Chris.
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Old 21st August 2009, 04:40 PM   #2
audio-kraut is offline audio-kraut  Canada
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Quote:
I am thinking of having a go at a pair of full range active speakers based around an Audiosector LM3875 Gainclone kit. Any experience/thoughts would be much appreciated.
What is a "active" fullrange speaker?
Active usually means a multi way speaker controlled by an active crossover.
Since a fullrange does not use crossovers - whats the point?
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Old 21st August 2009, 04:40 PM   #3
audiosteve is offline audiosteve  United States
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What a great idea! I have some JX-92's and a couple of ICEpower modules. I think I'll give it a go too. Of course that will be when my other projects are done. Too much on my plate right now :-(
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Old 21st August 2009, 09:36 PM   #4
zebra100 is offline zebra100  United Kingdom
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Quote:
Originally Posted by audio-kraut View Post
What is a "active" fullrange speaker?
Active usually means a multi way speaker controlled by an active crossover.
Since a fullrange does not use crossovers - whats the point?
By active I mean each speaker houses its own monobloc power amp (LM3875 GC, powering a full range driver). This negates the need for a separate power amp, although both speakers will need independent power cables and long interconnects. I also intend to use my passive attenuator for volume control utilising an Alps blue (50K dual log with 47K shunt resistors).

Chris.
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Old 22nd August 2009, 07:42 AM   #5
chris661 is offline chris661  United Kingdom
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Chris's definition of an active speaker is correct. Audio-kraut - you are thinking of an active crossover.

What's the budget for the drivers? You can get some really nice ones, but they do cost...

Chris
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Old 22nd August 2009, 01:13 PM   #6
Dr_EM is offline Dr_EM  United Kingdom
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Since you'll be using longer than usual "interconnect" leads and the signals carried by them will already be attenuated, I'd reccomend fitting the active speakers with XLR connectors and a balanced line reciever inside. You then need a balanced line transmitter at your pre-amp. Using a passive attenuator with high output impedance and long unbalanced cable runs is likely to introduce a lot of noise.
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Old 22nd August 2009, 01:24 PM   #7
Magura is offline Magura  Denmark
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....and a gainclone wouldn't be my first choice for this application.


Magura
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Old 22nd August 2009, 04:29 PM   #8
H3nry is offline H3nry  United States
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Dr Em has a point. Long interconnects' capacitance driven from 10-25K impedance will roll off the top noticeably. You'd want to drive this from a low impedance preamp, or if passive, maybe a transformer-type attenuator. With a chip amp in the box you should get very good electrical damping of the driver. Downside is heat in the box from the power transformer & amp affecting the speaker's characteristics. Should be an interesting experiment.
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Old 23rd August 2009, 01:17 PM   #9
zebra100 is offline zebra100  United Kingdom
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Originally Posted by Magura View Post
....and a gainclone wouldn't be my first choice for this application.


Magura
What would your first choice be?

I like the Gainclone sound. Detailed very detailed in the mid and treble, low distortion an not over blown in the bass department. An ideal candidate for a full range driver. I think it would be a worthwhile experiment.

Chris.
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Old 23rd August 2009, 05:51 PM   #10
Magura is offline Magura  Denmark
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Originally Posted by zebra100 View Post
What would your first choice be?

I like the Gainclone sound. Detailed very detailed in the mid and treble, low distortion an not over blown in the bass department. An ideal candidate for a full range driver. I think it would be a worthwhile experiment.

Chris.
Gainclones and FR drivers has IMHO never been a good combo. A current source amp like the FirstWatt amps would be a much better choice.
An F3 built as current source would offer pretty much the best of both worlds.


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