Thanks for that Colin. To be honest, I have in the recent past given some thought to the idea of active crossovers, most specifically because they would (might) allow one to "tune" a speaker. In particular I have tried to make sense of the MiniDSP with the possibility of eventually experimenting with the UMIK-1. However, I haven't really got far and with all the add-ons, I suspect that it would be very significantly more expensive than going the passive route.
The vendor you mentioned offers an assembled & tested Linkwitz-Riley OPA2134 2-way active filter at £30.48 including p&p. To this I would have to add the cost of four amplifiers, a number of PSUs and cases. Somehow, I doubt that I would get away with less than £150 on active crossovers which might -or- might not work and I certainly haven't got the expertise to diagnose any "issues" that might arise. Aside from which, I already have a number of amplifiers lurking about.
In case it's of general interest, a few more links to active kits, the first of which is a bit cheaper.
Audio Amps/Crossovers : Xkitz Electronics, Electronic Kits, Fun Educational Electronic Projects
complete plate amp with amplifiers and crossover built in
PWR-ICE125 | MiniDSP
and a very respected manufacturer doing similar
https://www.hypexshop.com/DetailServlet?detailID=2931
Audio Amps/Crossovers : Xkitz Electronics, Electronic Kits, Fun Educational Electronic Projects
complete plate amp with amplifiers and crossover built in
PWR-ICE125 | MiniDSP
and a very respected manufacturer doing similar
https://www.hypexshop.com/DetailServlet?detailID=2931
Thanks again Colin. On a quick scan of the Xkitz site, the XAMP-M2 2-way active crossover with combined 30 watt amplifier at $46 assembled along with the XAPS-50 50 watt DC PSU at $22 assembled sound interesting.
Would one build one crossover+amp and PSU into each speaker or have two crossovers+amps and a single PSU remotely?
I just wish this was supplied and supported from the UK
Some time ago I saw a design for a basic, cheap(ish) control unit comprising a high quality multi-step volume control, a four-way input selector and ten phono sockets built into a small box. I thought it was on Keith Snook's site but I haven't been able to find it again. This would allow easy connection / selection of a CD player and FM Tuner. Does this ring any bells with anyone?
Would one build one crossover+amp and PSU into each speaker or have two crossovers+amps and a single PSU remotely?
I just wish this was supplied and supported from the UK
Some time ago I saw a design for a basic, cheap(ish) control unit comprising a high quality multi-step volume control, a four-way input selector and ten phono sockets built into a small box. I thought it was on Keith Snook's site but I haven't been able to find it again. This would allow easy connection / selection of a CD player and FM Tuner. Does this ring any bells with anyone?
I prefer a dual amplifier directly driving the dual speaker drivers with VERY SHORT speaker cables.
The amplifier can be placed on a stand behind the speaker box, or attached to the back of the speaker box.
The Source and volume control, with Buffer, drive the longer line level inter connects.
The amplifier can be placed on a stand behind the speaker box, or attached to the back of the speaker box.
The Source and volume control, with Buffer, drive the longer line level inter connects.
What dual amp do you use? I guess that it wouldn't need to be hugely powerful in my case.
Buffer??? Do you mean the active crossover? Are you talking about "longer line level inter connects" from the active crossover to the amplifiers?
What causes me slight concern with this (active crossover + amp) strategy is that you will have additional mains cables all over the shop.
I used a pair of lm3886 with the gains set to +20dB for desktop monitors.
Big bass driver under the desk with another lm3886
i.e. 2.1 using five chipamps fed from three toroids.
The active crossover is effectively a high pass filter for the treble amplifier feeding the treble speaker driver. >2700Hz.
The other half of the crossover is a band pass filter for the middle amplifier feeding upper bass and midrange speaker driver. 140Hz to 2700Hz.
Finally a low pass filter feeding into the bass only amplifier to the 15" bass speaker. <140Hz.
All to LR4 and all without any equalisation. LR4 is two cascaded Butterworth 2pole filters
All the filters are inside the respective amplifier chassis. i.e. the left channel has a bandpass and a high pass filter on the one channel input.
The right channel has a bandpass and a high pass filter on the one channel input.
The bass has a low pass filter. The first stage is an MFB with two channel input to sum the L+R signals.
Big bass driver under the desk with another lm3886
i.e. 2.1 using five chipamps fed from three toroids.
The active crossover is effectively a high pass filter for the treble amplifier feeding the treble speaker driver. >2700Hz.
The other half of the crossover is a band pass filter for the middle amplifier feeding upper bass and midrange speaker driver. 140Hz to 2700Hz.
Finally a low pass filter feeding into the bass only amplifier to the 15" bass speaker. <140Hz.
All to LR4 and all without any equalisation. LR4 is two cascaded Butterworth 2pole filters
All the filters are inside the respective amplifier chassis. i.e. the left channel has a bandpass and a high pass filter on the one channel input.
The right channel has a bandpass and a high pass filter on the one channel input.
The bass has a low pass filter. The first stage is an MFB with two channel input to sum the L+R signals.
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As Andrew says, it's easier to build the amps and crossover in a separate box or boxes. Commercial active speakers usually have the electronics built into the enclosure for ease of use (and a reduction in cost as metalwork is expensive). There's no disadvantage in this but keeping them separate makes them easier to change and modify.
The Hypex and MiniDDSP plate amps are designed for loudspeaker enclosures but could be used remotely.
There was an active design using B110 and T27 drivers published by ETI in the late 70s. I think it was by Jeff McKauley. He didn't use hugely powerful amps, possibly even early chip amps of some sort like IPL. It was a sealed or ported enclosure and relatively straightforward except that he used a second B110 on the back of each enclosure, to balance out the sound - an early and effective method of dealing with baffle step loss.
I haven't been able to find this online and don't think I have a copy of it.
The Hypex and MiniDDSP plate amps are designed for loudspeaker enclosures but could be used remotely.
There was an active design using B110 and T27 drivers published by ETI in the late 70s. I think it was by Jeff McKauley. He didn't use hugely powerful amps, possibly even early chip amps of some sort like IPL. It was a sealed or ported enclosure and relatively straightforward except that he used a second B110 on the back of each enclosure, to balance out the sound - an early and effective method of dealing with baffle step loss.
I haven't been able to find this online and don't think I have a copy of it.
Vibration may have been a problem when electronics were more microphonic but these days it's an audiophile myth. Monitoring speakers wouldn't do it otherwise.
It's a bit like the Linn-promoted idea that having more than one pair of speakers in the listening room is a bad idea. When finally tested on it, even Linn's founder couldn't hear any difference.
It's a bit like the Linn-promoted idea that having more than one pair of speakers in the listening room is a bad idea. When finally tested on it, even Linn's founder couldn't hear any difference.
I wouldn't fancy building an active speaker at all. Too many safety (as in electrocution...) and heat and vibration issues for an amateur.
Certainly the art has moved on since the days of the BBC LS3/5A. Witness this ca. 2001 Spendor S3/5 with the improved bass unit. Spending Time With the Spendor S 3/5 By Herbert Reichert
Or Troels' SEAS CURV: SEAS CURV
Nostalgia ain't what it used to be.
Certainly the art has moved on since the days of the BBC LS3/5A. Witness this ca. 2001 Spendor S3/5 with the improved bass unit. Spending Time With the Spendor S 3/5 By Herbert Reichert
Or Troels' SEAS CURV: SEAS CURV
Nostalgia ain't what it used to be.
I consider it easier to build an active speaker with no exposed conductive parts.
That in my view makes it easier to make it safer for all users and operators.
Certainly vibration and heat dissipation must be design considerations, they cannot be ignored, but they are not about user safety......... heat and vibration issues for an amateur.
Vibration.
Despite what Colin says, components are still microphonic.
Some powered speakers do seperately enclose the amplifier.
dave
Thank God it's Friday
Aren't all of these components powered by 6 to 24V DC? I would have expected this usually to be derived from an enclosed power "Brick" as typically used with laptops?
As a manufacturer of active speaker points out, if modern electronics were microphonic - ie suffered vibration to a sufficient degree to generate a signal audible over a speaker - most electronics in modern military hardware wouldn't work. Obviously some care is needed but it's not an issue to get hung up about. The small, commercial actives I've been using for the last 4 years are among the best speakers of any type I have heard. One of their attractions is the serious amount of headroom they possess. Not much sign of microphonics there and good active speakers have been in use in professional studios for years.
However for DIY it's probably easier to have the electronics elsewhere, as Andrew suggested.
However for DIY it's probably easier to have the electronics elsewhere, as Andrew suggested.
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An argument that means little in this context.
Military kit typically has mil-spec components, choosen forlow microphonics. And there is a difference, sometimes significant between working and hifi.
dave
No way. 100W is a LOT! You're not going to run a serious HiFi amplifier off a little 12V or 24V laptop or phone wall wart.Thank God it's Friday
Aren't all of these components powered by 6 to 24V DC? I would have expected this usually to be derived from an enclosed power "Brick" as typically used with laptops?
Even at 12V, this is 8 Amps. That is a lot of current, comparable to a 2kW electric fire. A low impedance car battery might get near it, but for mains supply you'll need to design with big reservoir capacitors and a serious output transformer of low impedance.
Listening on headphones, and listening on big speakers are entirely diifferent propositions.
Quite what this has to do with BBC mini-monitors, I can't remember.