Peerless 3" computer speakers

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It is a 2.8L cabinet with a 190 x 300 baffle, this is probably a bit large it was just a baffle I had a simulation for.

If you tell me the actual dimensions you plan to use I can check the correction simulates right and adjust if required. Also if you plan to use these close to a wall give me an estimate of the distance and I can try to factor it in. You get quite a lot of bass lift off a close wall and it could end up sounding a bit bass heavy.

Good to know there are some more audio fans in the area.

Andy
 
Hi, thanks again, that would be great. I had imagined the following:

120mm wide
290mm high
140mm deep

using 12mm Ply or MDF

I would prefer the speaker to sit at the top of the baffle so there is equal distance between the driver and the sides and the top, or certainly nearer the top than the middle.

the speakers will sit an inch or so from a screen that is behind the desk. the screen goes about 470mm higher than the desk.

Typical usage will be fairly low level, talking volume. i'd prefer too much bass than not enough.

thanks again for your help.

Andy
 
Hi,


I have done two version for you both based on your new dimensions. I have treated the box as if it is anechoic as the effect of your screen will be difficult to include. The driver position has been optimise to reduce diffraction ripple. You can see the location of the driver in the view box. If you move it away from this location you will see increase ripple at high frequencies and the dip after the mid range bump will become deeper. I have assumed sharp box edges as that is worst case if you can round them off it will be even smoother.


You can see the filter components in the top corner of the diagrams.

I have set them up to have a high bass output compared to the mid top on axis, the first still has fairly high mid range output in terms of the room power. The fist uses the Box roll of and matches the rest of the response to it. The diagram shows which component control which parts of the response, increasing the value will cause this region to be decreased in volume. This has a slightly forward mid range response in room but is flat on axis.


The second option has a trick I pinched from the KEF Coda3 which uses a large capacitor to extend the bass response. The problem with this particularly for a full range is all the audio will be going through a electrolytic capacitor. So if you try this and find the audio is a bit distorted a polypropylene in parallel of 3.3 - 10uF should help to pass the high frequencies. It will shift the bass a little but so little that it won't matter. I have tried to balance the room power to be slightly falling which is normally considered good practice. It still has a basically flat on axis response it is just slightly downward tilted. So this might still sound a bit mid forward. If it does the 6.8R resistor (the one in parallel with the whole filter) adjusts the mid range and increasing it further will drop the mid range. This is very in efficient so do not play it loud and keep an eye on the bass driver excursion if you turn it up.


I hope this helps. If you would like the file to try out PM me an email address and I will send them over.


Regards,
Andy
 

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Hi, that's great, thanks.

A few questions though....

1) the 330uF capacitor adds the extended bass correct? I could, in theory, add a switch to the back to bypass this?

2) the 5.1 ohm resistor in series with the inductor, is this the coil resistance? or a resistor itself? are the other resistors shown, all actual resistors?

3) If you have the time, could you recommend a supplier for the parts? Ive use Europe audio before I think...

Thanks again
 
Yes you can switch the 330uF in and out.

It is a 0.51R resistance and yes it is the coil resistance you could go higher it will reduce sensitivity further but make the coil cheaper. 0.47 to 0.68 is a typical resistance for a cheapish coil. All the other resistors are seperate physical parts.

Loudspeaker freaks / Europe audio seem to be one of the best places to get these parts. You might find some of the capacitors a bit cheaper at Digikey but they do not sell the large bipolar electrolitics and resistors were cheaper at Europe Audio.
 
Rough foil is a etching method used in electrolitic capacitors to increase the plate surface area without increasing capacitor volume. So basically yes it is the same its another type of electrolitic capacitor.

Clarity cap should be good for this application if its on sale I would go for that.

The parts you have identified look like they are suitable.

As resistors are comparatively cheap it might be worth buying values one up and down from those suggested in case you want to adjust the response. It is unlikely you need 20W parts in this application as they will not see all the power, its shared with the speaker itself, especially if you don’t plan to play them loud. 10W would be fine and you can probably get away with 5W.

I will send files when I am back at my computer. I would recomend you try adjusting the values in the simulation to get a feel for how they affect the response before ordering any parts.

Andy
 
Great, thanks again. Will have a play today if i get time.

I did think 20W was a bit excessive, but as you say, they are cheap enough.

one more thing, you said "So if you try this and find the audio is a bit distorted a polypropylene in parallel of 3.3 - 10uF should help to pass the high frequencies. It will shift the bass a little but so little that it won't matter." would 3.3 or 10uF be more effective? or should i go somewhere in the middle?

Thanks
 
10uF will be better, basically the larger you go the better the bypass will be. I stopped at 10uF as if you go larger than that in polyproplene they get very expensive.

Eventually it would also get large enough to affect the bass response significantly so you would need to reduce the size of the non polar electrolytic.

Regards,
Andy
 
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