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Class D Switching Power Amplifiers and Power D/A conversion

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Old 15th March 2013, 01:12 PM   #3581
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Location: Copenhagen, Denmark
Quote:
Originally Posted by ekbaird View Post
The version where the speaker chambers are tilted 90 degrees so they are vertical instead of horizontal, resulting in a taller and narrower box - does it affect sound or anything?

Is it ok to use a 1/2" roundover bit on the inside/outside of the ports and edges of the box in addition to the speaker holes? or should they have a smaller radius curve..
Obviously it has a huge negative impact on sound quality and especially stereo imaging. But if it's the only way to fit your requirements for space then it's far better than the alternative, ie. not building one at all.

If you can manage it. Use the recommended epoxy glues, and better still, have made interlocking cabinet edge. Then I highly recommend using a 1/2" round over tool everywhere. But it basically means that you can't use screws anywhere which makes the construction more tricky. But ultimately also more rigid and durable.
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Old 15th March 2013, 02:13 PM   #3582
axebay is offline axebay  Sweden
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Originally Posted by Saturnus View Post
Changing the input cap to a 470nF WIMA cap (part no. MKS0C034700E00) which fits in the original hole pitch of 2.54mm (1/10") will both improve sound quality and completely eliminate power-on pops.
Does it has to be this particular cap?
I've already ordered these caps https://www.elfa.se/elfa3~se_sv/elfa...tem=67-256-51&
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Old 15th March 2013, 02:19 PM   #3583
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Originally Posted by axebay View Post
Does it has to be this particular cap?
It's the one that I use so I know it works perfectly well. Also better than "ultra hi-end audio grade" Jensen paper-in-snake-oil ones.

The WIMA is also the only polyester/polypropylene cap (that I know of) that fits in the 2.54mm pitch.

Last edited by Saturnus; 15th March 2013 at 02:22 PM.
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Old 15th March 2013, 02:23 PM   #3584
axebay is offline axebay  Sweden
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Originally Posted by Saturnus View Post
It's the one that I use so I know it works perfectly well. Also better than "ultra hi-end audio grade" Jensen paper-in-snake-oil ones.
Ok, then I'll hope that my "not even a trail of snake oil" caps, aluminum electrolyte, will work fine as well
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Old 15th March 2013, 08:26 PM   #3585
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Default 1st photos of my build - Baffles

Hi

I thought I'd post a photo of my build so far.....

Have routed holes for the HP10W's and rounded off with 6mm roundover bit... Routed the insets for the PHT-407N's so they fit flush, awaiting delivery of hole saws to finish off. I have cut the port slots with a 30mm flat wood borer and joined the holes up to form a slot with a jigsaw. I still have to glue them all together, sand and finish off with the roundover bit......
To the right of the photo you can see the circle cutter jig that I made for the hole cutting and the inset routing for the tweeters.
I shall be ordering the PHT-407N's next week and start gluing up the speaker grills and drivers to the baffle. As far as I can tell, I wont need to make any mods to the tweeters like the piezos? I shall of course use sealant when I mount them to make sure they are airtight.......
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Old 15th March 2013, 09:51 PM   #3586
ekbaird is offline ekbaird  United States
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Thanks Saturnus for the answers it helped ..almost 1/2 done with build phase..
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Old 16th March 2013, 11:41 AM   #3587
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Default battery charge meter

Hi

I'm a bit of an old skool analog lover so I'd like a little nod to that in my boominator.... I'm thinking of fitting this battery charge indicator (without wiring the backlight to save power)

Universal Battery Charge Indicator | eBay

but I'm wondering if it would be a drain on the battery compared to a little colour changing led indicator, anybody enlighten me on this?

BJ
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Old 16th March 2013, 12:45 PM   #3588
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Originally Posted by Saturnus View Post
In principle, no.

On the Boominator however that implies you're making the reflex port smaller which in turn will increase air speed in the reflex port, so here, yes, it will bring a fair bit of problems.

If you're just making it shorter without decreasing the area then you're making the tuning frequency and Qs much higher which brings many other problems.

In both cases, a basic understanding of how a reflex cabinet works will help you realize what problems and how they can be overcome, so I suggest you search the internet for some information on this, if you want a more thorough explanation.
So I can have a short vent as long as I keep an eye on the port air velocity so it doesnt exceed the "chuffing speed" for the choosen diameter of the port. OK sounds good to me.
I just have a some questions left, then ill leave you alone Saturnus :P
1. If my cone excursion doesn't exceed Xmax, do I still need a highpass filter? If yes, which capacitator and resistance would you use for a vented box with Fb=70Hz and F3=64Hz.
2. You keep mentioning the Q of the box. The only Qbox I can find is a formula for calculating an appropiate Vb for a closed enclosure. The formula for calculating an appropiate Vb for a vented enclosure is:
Vb = 15*Vas*(Qts^2,87). So what's the Qbox for a vented design?
And trust me, I've searched the internet for answers to avoid going onto peoples nerves, but can't find the answers for these questions. So it would be kind of you if you could answer these questions
/André

Last edited by aml417; 16th March 2013 at 01:09 PM.
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Old 16th March 2013, 01:19 PM   #3589
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Quote:
Originally Posted by brummiejon View Post
Hi

I'm a bit of an old skool analog lover so I'd like a little nod to that in my boominator.... I'm thinking of fitting this battery charge indicator (without wiring the backlight to save power)

Universal Battery Charge Indicator | eBay

but I'm wondering if it would be a drain on the battery compared to a little colour changing led indicator, anybody enlighten me on this?

BJ
Personally I think that is rather dull looking gauge. It's cheap though.

Search google, amazon, or fleabay for "voltmeter gauge" for a vast selection

Power consumption will typically be 100mA with the backlight, and 10 to 1000 times less without it. It entirely depends on construction. 100-200uA seems to be typical without backlighting though. That's 0.0012-0.0024W at 12V.
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Old 16th March 2013, 04:35 PM   #3590
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Default Battery charge indicator

Thanks Saturnus
I agree that the battery charge meter I used as an example is a bit boring, I didn't think to search for "voltmeter", there are a lot more choices under that heading. So it seems that it wont be too much of a drain on my battery, that settles it, I shall be fitting one.....
This afternoon I have been gluing together the port/handle assembly, Tomorrow, when the epoxy is fully set, I shall be tidying up the ports with a file, finishing off with sandpaper and routing the edges of the port hole with my roundover bit......
every week gets a little closer to finishing......
BJ
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