First Speaker Build, Help!

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First Speaker Build. (UPDATE -- Project On Hold)

Hi,

I'm about to start my first speaker design and I've chosen to build a Sound Bar that looks more like a center speaker, because the TV and stand will have to sit on it. (See Pic) The goal behind this project is to produce something that sounds a lot better then the speakers built in to a 32'' Samsung TV, so that can't be hard, right? My targeted audience are my parents who have found the sound quality on their Samsung to be less then adequate, which is true for pretty much every flat screen I guess.

When I visit (at the wrong time due to some soap being on) my mother will often comment on how the tiny TV in the kitchen sounds better then 'That Thing', and she's not wrong, even after extensive tweaking it still sounds pretty awful. Of course there’s more to it then just a poor sounding TV. Neither of them are getting any younger so their hearing isn't what it used to be, it comes to us all.

I'm considering using a 25W @ 4 Ohm TDA7492 Class-D Audio Amplifier (14v-19v 3A) by Sure Electronics along with a pair of 4'' full range Dayton RS100-8's in a ported box. I believe the amp/speakers to be well suited for a ported boxes with a Volume of around 0.10.- 0.17 ft3, although I haven't worked out the port size yet.

Like I said this is my first build so I'm not trying to take on Pioneer and their EX series speakers. I understand there's a lot more to speaker building then putting a speaker in a box, in fact I've read so much over the last few days that I'm going have to read it all again, then again...

Any and all advice will be much appreciated, for example the pics I've provided here show how the SB will look. However, each one is different inside. Are round surfaces inside a speaker box a really bad idea due to resonance, even though it will be packed with good quality acoustic sound dampening? Are these voids within the box going to be an issue?

My budget will be around £150 for this project.

Although I expect [FONT=Verdana, Helvetica, Arial, sans-serif]there is no single "right" or "wrong" way,[/FONT] what are the do's and don'ts for newbies such as I?

Thanks.

J Smith.

 
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Curved surfaces within speaker cabinets are just fine; the main reason they're not widely used is the difficulty in construction relative to flat slabs. Obviously the material you build the box out of doesn't want to flex too much, and absolutely mustn't rattle or buzz – which involves using lots of glue, mainly.

I see no acoustic requirement for anything beyond your first proposition; indeed, just one lump running front to back separating the space should suffice (unless they're essential bracing to stop the box vibrating, or you're intending to mount the amp in the centre space).

You're not going to get much stereo effect, but as long as it's not music programs you're probably not going to miss it much.
 
Thank you for the change in pictures; I can now (just) read "amp here".

I assume you'll have a cover on this, not just the TV set? Then your amp is going to need ventilation, or heat sinks on the outside of the box, or it's going to overheat (nothing, neither power supplies nor amplifiers, is 100% efficient, and the waste energy always ends up as heat. It will probably need a connector panel, too, so as not to have loose wires trailing, with an on/off switch, and if this gets a bit warm that's just how it goes. If the heatsink/connector panel can be taken out of the back, complete with the amps, you can glue the top panel on as the speakers can be unscrewed from the front (and it's always easier to make an airtight seal with glue than with screws.
 
Thanks for the reply's.

Those Pics I've attempted to add to the original post are not the finished design, just the basics of the speaker shape, my main concern was using curved surfaces instead of right angles. I've added some links to this post (hope these work) to give you a better understanding of my design, again these are not by any means the final design.

My first stumbling block in all of this is getting the ellipse shapes cut, either the local family run DIY shop on the corner street is to small to have a CNC router, or those local companies that do have a CNC router can't be bothered with such small fry like myself.

Never the less, I'll carry on in my quest to produce this sound bar!

J Smith.
 

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J Smith,
I think the base part that sticks out in front of the baffles will worsen the sound quality. The sound will bounce off of those and right back up at the drivers. Secondly, as for the central amp compartment... Anything you can do to recess the front part of that - move it back from the baffle - will improve sound quality. You parents will want to make out the TV dialog, and so I think these are important issues. Perhaps you can make some kind of a vent, such as out of slats, recessed, in the center part of the baffle, also to provide air flow for the amp there as well? With venting, I think you could go with an amp that does not use a fan.

Do you intend to cut a stack of oval pieces and glue them all together? It looks like a very ambitious bit of work. Best of luck to you!
 
Ook, I should add, "the top as well a the base will stick out in front of the baffles". These are both going to do the same thing - add distortion and make it harder to make out the people on the TV. Perhaps you can consider a baffle that is slightly in front of the base of the TV, and which keeps its flat baffle, but is not purely oval in its finished shape?
 
Thanks for taking the time to reply Markgm.

You are absolutely right in saying it looks like a very ambitious bit of work and correct in pointing out the flaws in the design. In fact the more I read about speaker building and the more I talk to good people like yourself the more I realise I'm making a big mistake here. I think this project is a classic case of a newbies excitement and enthusiasm getting the better of him.

The penny sort of dropped after a few CNC companies got back in touch with me over the weekend saying they can certainly do the cuts (for a price) but were concerned on how I was going to stick it all together, and more importantly how it was going to stay stuck together. I also spoke to a chippe (a joiner) last night who had a few sharp intakes of breath.

Needless to say this project is now on hold until I have more experience, lots more.

I've seen the light, I found The Speaker Building Bible. My first project is now going to be a cheapish off the self DIY kit.

Thanks for the info guys.

J Smith.
 
Hi J,
Well, I think your speakers idea looks like very creative and cool-looking. If anything, you could frame the above, in terms of outside shape and dimension, but where it has no walls and is hollow, and wrapped with grill cloth. Then, you could put a pair of DIY speakers, each in their own cabinets, inside that box. And an amp. Or something to that effect.

I'm new to DIY, but old with audio and acoustics enthusiasm. For example, in the other thread here about an 'acoustic boombox' - that is my first DIY speaker - its a kit, and carrying rack. You could stick a pair of those speakers into a shell like what you have depicted, but say 10-12" tall, with a little space left over to place 9" tall speakers inside of it.

As someone else mentioned here, there won't be a whole lot of stereo effect with the two speakers so close together. However, The sound will always appear to be coming from around the TV itself, which could be a boon for TV watching when not using 5.1.

It's all good. Cheers,
Mark
 
I'll work something out, another headache for me was making it aesthetically pleasing for my parents, you know what they are like, 'I'm not having a speaker there, I'm not having all them wires' etc etc. That's why I was going for the Sound bar (center speaker look) approach.

Now my house is a totally different story, The B&W based 5.1 set-up is the boss in my living room )

J.Smith
 
Well, you've got an aesthetically pleasing look, there. If you build a couple of speakers 5" high, and put them inside a box like what you have designed, but which is maybe 8-10" high, and which has sufficient framing to hold the weight of the TV, and which has grill cloth wrapped around at least the front half, you'd have my vote for this particular application. Isn't that where all the various designs come from - from the various applications?

As far as room acoustics go, my experience backs this up, and the word of very skilled others is where I got it from. It goes like this... First, left speaker on the left, right speaker on the right. Get them in phase. Next, clear the 3' radius around the front center of the baffle on each. I like to look at it spherically. Inch by inch, the closest are the most important. Clear the area of any objects that can reflect sound back at the drivers, which will distort what is coming out of them at the time. Then, the area between the speakers, and really, the whole sound stage. And then, make the whole room for audio and nothing else :)

A couple of years ago, I had success with a friends really cheapie little 5.1 speakers ($5 plastic things). He would set the front ones on top of the TV. To make out the dialog better, I put thin little boards on top of the TV so they stuck out a few inches in front of it, and set the speakers on the ends of those. We agreed the dialog was noticeably clearer.

So where I'm leading up to is this... If you do not impose surfaces, like shelves, tabletops, walls, floors - that sort of thing, or in the above example, the top of the TV, within the first few inches of the baffle, you'll more than likely gain a noticeable improvement. Other objects, like a strip of wood won't be the same as a shelf of wood, particularly a sanded/rounded one. Sound can and does go around objects, too. The sound off the front of a speaker typically goes right around the side and off the back, as the speaker radiates spherically.

I digress... With framing material inside your box idea, there is the questions of what it does to sound coming off of the speakers inside. So, some tricks would be to make the framing material smooth, to have a smaller footprint. Other approaches would be to trap that sound instead of reflecting it, or to act like a horn and with (calculated) clean dispersion. I mean, you could put horns inside of the outer box. I surely digress.

I'll be curious what you come up with for your parents needs. A little experimentation along the way could go a long way in experiencing the effects of actual this-and-that.
 
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