Need advice - Desk with built in 3" drivers & amp

[lersince1991]

Hi, I've designed a desk a couple of year ago and now at the stage of making the second and final prototype. The first prototype I used an old PC speaker setup, ripped the 2.5" drivers out of the satellites and used the sub to power them as they were sold. I'm now looking for something a lot more professional as I will be exhibiting the design at furniture exhibitions and awards in London, Stockholm and milan. The desk is made from an MDF core then fully clad in Corian and brushed stainless steel legs and details.

Link: LR Design Ltd
Note: I'm in the UK

I have decided (I think) to use x2 monacor SPH-30x 3" full range drivers and need to build in the amp this time and link it to the power supply which is built in too. Its complicated so ask questions if you don't get it, I could make some images for you

I need advice on which amp to get, not to expensive but decent and able to drive the sph-30x drivers. I also want a subwoofer output for an optional subwoofer (the input and sub output will be on a connection plate underneath the worktop). And also 8ohm or 4ohm 3" drivers?

so summary of questions:
1- Which ohm for the 3" full range drivers, 4ohm or 8ohm
2- What amp can I get to power the audio system
3- How can I add the option of a sub? does the amp have a sub output?
4- How can I link it to the power, basically, in the desk there is a 3 pin mains electricity which powers 4x uk plugs. I was hoping to run the amp from this.

Thanks a lot for your help
Luke.

edit: Link to the 3" drivers

[richie00boy]

I would go for the 8 ohm version as it has a little higher Qts and Vas which should give a little more bass, and the higher BL a bit more tightness and slam to the sound. What volume are you putting them into?

As for the amps, you'd need a pair of amps, then some line level circuitry and another amp for the sub. I guess it would be best to add this into the sub as an integrated unit and just feed it left, right and mains power.

[lersince1991]

Originally Posted by richie00boy

I would go for the 8 ohm version as it has a little higher Qts and Vas which should give a little more bass, and the higher BL a bit more tightness and slam to the sound. What volume are you putting them into?

As for the amps, you'd need a pair of amps, then some line level circuitry and another amp for the sub. I guess it would be best to add this into the sub as an integrated unit and just feed it left, right and mains power.

Thanks for the reply, I will go for the 8ohm version of the 3" monacor drivers then.

Don't most subs have a built in amp? i.e. active
What about crossover? - is it needed?
I will more likely source a finished external subwoofer and recommend it for people who want the extra.
So I would just want the output for the sub in the connection plate.
As for the built in drivers these need to be fully powered and driven from inside as a stand alone system with the option for sub.

Any chance you could explain a bit better please? I'm not that savvy with amp tech.
So your saying I need an amp for each driver to make it stereo? how can I power them from mains electricity? then link a mono signal to each amp from the input?

The volume can be altered to whatever is good, i have attached an image to show the interior configuration.
The width of the channel for each speaker is 79mm and height is also 79mm.
The block of wood behind the speaker can be moved, it is there for no other reason than to isolate the driver, is this even needed?
In the images below, green is moisture resistant MDF, white is 6mm corian.
I have hidden the driver behind the corian cladding but looking into how I can still make it removable, saw my b&W 685's and saw how clean they looked

Thanks a lot for your reply mate!
Cheers!!!!
Luke

[richie00boy]

Sorry I thought you meant to build your own sub. You seem to be new to audio DIY so maybe it would be best for you to look for an off the shelf small stereo amp that you could hide away?

You want to be looking at about 0.83 litres volume for each driver. I suggest you also use some wadding to tame the reflections due to the square and small box.

[lersince1991]

Originally Posted by richie00boy

Sorry I thought you meant to build your own sub. You seem to be new to audio DIY so maybe it would be best for you to look for an off the shelf small stereo amp that you could hide away?

You want to be looking at about 0.83 litres volume for each driver. I suggest you also use some wadding to tame the reflections due to the square and small box.

No problem made it clearer now
Yeh not really made much audio systems myself before.
An off the shelf stereo amp would be perfect, but I need a really small one that can power my drivers and have a sub output too. I run my b&w 685's from a kenwood amp which is massive, I'm looking for one which can fit in the passage behind the speaker pretty much! Possible? ... And fairly cheap, thought I would be able to just get a little component from somewhere? This desk might go into mass production so I also want to research and do it how I would if mass produced. And what about the power supply? how can it be hooked to mains elec.

So for the volume, would it be best to put the block of wood separating the speaker 133mm away from the driver? this would equal .83 litres in volume, does it matter if its in a rectangle shape?

Yup put wool in the last prototype, will do the same here and stuff it with a good amount.

Thanks again!
Luke

[lersince1991]

This sort of thing with a bit more power and quality for the monacors.

will be using QED cabling because it sounds good and thats good for marketing, plus I use it with my b&w 685's.

2 Channel Mini hi-fi Amplifier Stereo Amp | Virtual Village - UK

Luke.

[picowallspeaker]

Absolutely NO! Don't matter which cable you'll use .The sound will depend on 1st : quality of the PSU ;1st(bis):connection between PSU and amp must be very short ; 2nd: quality of the amp .1 good watt is better than 20 ugly claimed watts;3rd :speaker quality.Even a good speaker if placed incorrectly sounds awful.
How does the desk sound ? nearfield listening will reveal everything . I prefer sats suspended under the ceiling...however free to be positioned ,not constrained .

[planet10]

Speaker position in the desk as pictured is very poor. Placement of these is about right, but in actual use would likely need some proping up at the front. On my personal pair, i'm going to pinch a couple "feet" from dead G5 iMacs.



And that wouldn't be my 1st choice for 3" driver...

The Virtue amps with the built in sub amps are a decent choice.

[chris661]

A little late to the party, but here goes...

Why not use a Tripath amplifier (41Hz Audio). I built the amp-6b, which sounds brilliant, especially considering the cost. I had many comments at a recent audio meet that it didn't sound like a SS amplifier (they were valve nuts), and that it was very easy to listen to.

Power is 15w/ch into 8ohm, 25w/ch into 4 ohm. I used a 60 watt SMPS with it, because it was cheap (£20). The whole thing cost me around £50.

You'd need another amplifier for a subwoofer, but a pair of small woofers and another one of those amps would probably suffice.

ohh, here's a thought.

If you used the amp9-basic, you could bridge one pair of the amplifiers, to give a subwoofer output (you'd need to cross it over, but that could be done actively, on the cheap), and you'd have an ideal 2.1 amplifier, but you'd need a bigger power supply.

[lersince1991]

Originally Posted by chris661

A little late to the party, but here goes...

Why not use a Tripath amplifier (41Hz Audio). I built the amp-6b, which sounds brilliant, especially considering the cost. I had many comments at a recent audio meet that it didn't sound like a SS amplifier (they were valve nuts), and that it was very easy to listen to.

Power is 15w/ch into 8ohm, 25w/ch into 4 ohm. I used a 60 watt SMPS with it, because it was cheap (£20). The whole thing cost me around £50.

You'd need another amplifier for a subwoofer, but a pair of small woofers and another one of those amps would probably suffice.

ohh, here's a thought.

If you used the amp9-basic, you could bridge one pair of the amplifiers, to give a subwoofer output (you'd need to cross it over, but that could be done actively, on the cheap), and you'd have an ideal 2.1 amplifier, but you'd need a bigger power supply.

This looks really interesting thanks for the input. Will have a look into it and try and get my head around it.

Thanks to everyone for the info!
Luke