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Stereo speakers for TV  

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edfuller
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08/08/2019 8:58 pm  

Hi,

I'm looking to build a bluetooth speaker that I can plug into my TV to improve the sound. This is my second ever speaker build so I'm trying to keep it simple.

I have this amplifier board:

https://www.parts-express.com/dayton-audio-kab-230v3-2x30w-class-d-audio-amplifier-board-with-bluetooth-40--325-103

and am using a pair of Dayton PS-95 drivers. The box will be about 0.2 cubic ft with a port to tune it to about 80ish Hz. Not that low but if all works out I might go for a 2.1 system in the future but for this build I'm keeping it simple.

The box will be a combination of Walnut with a Maple baffle and I'm thinking about having it turn on with the TV by running a 5v relay to the power feed of the speaker which gets activated by the USB port of the TV.

So, questions 🙂 My amp is 30w per channel, I fired it up last night with one driver connected (just loose, not in an enclosure) and it was nowhere near loud. The driver is 8Ohm so I guess that drops the 30w to 15w? Sensitivity is around 86db so at 15w that should bring it to just under 98db if my calculations are correct. Now, the driver wasn't in an enclosure and I was using a 12v 3amp supply, if I put the driver in an enclosure and upped the power supply to 20v 5amp would that make all the difference do you think? Our lounge isn't huge so I'm hoping these will have enough guts to fill it. I'd like to prove the theory of what I'm doing before I invest a lot of time in building the box, would be really disappointing to throw it all together only to get a pretty lackluster result.

So I guess another question would be, does this setup sound reasonable? Bearing in mind I don't want to build crossovers for this project but I could get some off-the-shelf ones if that would help.

Another thought, I have 2 spare Hivi M4Ns, has anyone ever run different speakers in parallel? Ie a PS-95 and M4N per channel? Or would that sound horrible due to differing frequency responses? Just throwing ideas out there 🙂 Any inspirational ideas around combing all 4 drivers in the one project?

Thanks


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Douglas Blake
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08/08/2019 9:25 pm  

One of the reasons that open driver on a table thing is less than impressive is that you are getting cancellation from the back of the speaker.  When a woofer moves out it creates two things... pressure at the front and rarification at the back. The opposite happens when it pulls in. With no baffle to isolate these two effects they will cancel and the sound level is drastically reduced throughout the bass and midrange. The treble is less affected but it still gets some cancellation. Even cutting a hole in a cardboard box is going to be a better test than operating the speaker in free air.

Also please allow me to suggest that if you are working in a room any bigger than about 10 x 10 feet a 3.5" driver just isn't going to move enough air to get the job done. Nick and the others will be able to advise you better but I would suggest you look into either 5.25" or even 6.5" drivers for an average living room.

Check the voltages on the bulk (big) capacitors (the photo shows 35 volts) if they are rated higher than 25 volts you should consider running it on a 24 volt power supply capable of about 4 amps. This will bring the amp up to full 30 watt x 2 power for you. At 12 volts, you will be lucky to get 5 watts per channel from it and it will clip prematurely causing a lot of distortion.

Please note that Dayton Audio only specs that amp board from 110hz ... It is likely to be a bit bass deficient no matter what you do. 

You should also note that of the TPA line the TPA3118 is not rated for 4 ohm use.  At 4 ohms it is very likely to overheat and shutdown on you, so be careful with your driver selections.

I'm not saying there's anything wrong with your choices ... certainly almost anything is better than the speakers in most TV sets... but before you invest too deeply into the project you may want to spend a few minutes looking at other options.


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edfuller
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09/08/2019 12:55 am  

@douglas-blake

Thanks for your reply, this is exactly the sort of information I was looking for. The lounge is pretty small, I don't know the exact dimensions, so they may be ok but I don't think think anyone ever regrets going with bigger drivers. My PC needs some speakers so maybe I'll re-purpose the PS-95s for that instead. I didn't realise this board dropped off around the 110hz mark either.

Would this be a better option for the lounge?

https://www.parts-express.com/dayton-audio-dta-21bt2-100w-21-class-d-bluetooth-amplifier-with-sub-frequency-adjustment--300-3831

Paired with some larger drivers and a sub?

Or I could go Sonos Beam for the lounge and use the PC speakers as a project.

 


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TVOR-Ceasar
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09/08/2019 1:45 am  

Where's the specs stating 110 Hz? all I could find is here:

https://www.daytonaudio.com/index.php/kab-230v3-2x30w-class-d-audio-amplifier-board-with-bluetooth-4-0.html

Looks like 22-20k +-3 dB

Is there a frequency plot out there I don't see?

-Charlie


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123Toid
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09/08/2019 2:17 am  

@edfuller I am going to respectfully disagree with @douglas-blake.  I use those boards quite often and haven't noticed any bass deficiency.  Having said that I usually use these in smaller builds without much bass anyway.   I am not sure where he got the 110hz, but the site states 22hz-20Khz.  They are actually this exact same board from Sure Electronics.  Maybe he can clarify what he meant.  I don't know what you mean by small, but I don't think you would have a problem with sound.  The main problem you will have is bass.  I know you said you don't do crossovers, but I would at least consider a Baffle Step Compensation circuit or a subwoofer like the Voxel or my redesign of it.   

As far as the speaker choice.  The PS95 are great speakers and should do well in a smaller sized den.  I use some 4" full-range with a subwoofer. in my own only powered by 30 watts and it is just fine.  Your main issue will be the 8ohm load.  I think the speakers will still be okay, but might lack a little. If you do want to change it up, I would try the RS100-4.  I can confirm they get really loud at 30 watts of power.  That is basically what I am giving them in the Dinas and they can get louder than you need.  Some of that will depend on the source of course.  

As far as an amplifier, I think you are fine with what you have.  Like Douglas said, I would upgrade to a 24V power supply or at the very least 19v 4.74a.  But if you wanted something with a remote, you could check out these options. 

https://www.parts-express.com/21-amplifier-50w-x-50w-x-100w-with-built-in-bluetooth-30-backlit-lcd-screen-and-ir-remote--320-63 6" target="true">DIY Box Option

https://www.parts-express.com/dayton-audio-dta-pro-100w-class-d-bluetooth-amplifier-with-usb-dac-ir-remote-and-sub-outpu--300-383 5" target="true">Dayton Audio

https://www.parts-express.com/smsl-q5-pro-stereo-amplifier-usb-optical-coaxial-dac-with-subwoofer-output-2x40w--230-21 0" target="true">SMSL

My final advice.  If you are going to end up using these either in the computer room or living room.  I would just build them and see what you get.  If they don't fill your room enough, put them at your desk.  If they do, then you get a new project for your desk 😉 


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Douglas Blake
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09/08/2019 2:22 am  

@tvor-ceasar

Can I plead "Confusion", here?  I just checked both links and they do indeed say 22-20k ... The 110hz was for the drivers... My bad... Sorry.


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123Toid
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09/08/2019 2:28 am  

@douglas-blake

No worries.  We just thought you saw something we didn't.  I would have been glad to learn something.  


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Douglas Blake
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09/08/2019 2:28 am  

@123toid

LOL... Apparently I did... 🤔 


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Douglas Blake
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09/08/2019 3:29 am  
Posted by: @edfuller

@douglas-blake

Would this be a better option for the lounge?

https://www.parts-express.com/dayton-audio-dta-21bt2-100w-21-class-d-bluetooth-amplifier-with-sub-frequency-adjustment--300-3831

Paired with some larger drivers and a sub?

Or I could go Sonos Beam for the lounge and use the PC speakers as a project.

 

That Amp is probably a better choice. Although I would suggest staying with a stereo (2.0) amplifier and using a powered sub-woofer only if you actually need it. In many cases you will find you don't. 

I don't even want to guess how often I've been into systems where one of two things is happening... either the Sub-Woofer is sitting silent 95% of the time ... or ... the crossover is set so high the thing is actually producing mid-range sounds, just so it makes noise.  I would advise you to try simple stereo for a while before even considering a sub-woofer.

Remember, the goal is good, proportionate bass, not a lot of boom and thud that ends up giving you headaches.

Maybe try one of the Linkfor amps.  I have one running in my living room for evaluation purposes and it's doing a bang up good job, so far. I especially like the tone controls, nice feature, even though they are currently set "flat". A little tweak on that bass control might be all you need.

I have nothing against 2.1 amps, if you know you need a sub-woofer. But it's often better to add a powered sub if and when you actually need it.

Driver wise, I will defer to Nick's advice to go ahead with your build and then decide where they will land after some listening. But I would still suggest you consider something bigger, for a future build. For an average listening room I seriously doubt really small drivers will win any trophies.

Don't worry too much about designing crossovers. It's an interesting challenge but there are plenty of "off the shelf" boards you can get and most of them will work just fine. You can always replace them when you are ready to design your own.


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edfuller
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09/08/2019 5:03 am  

Hey, thanks for the advice guys, I think I've got a plan. I was pondering this on my commute home tonight, I have about 1.5 hours on the bike every day so plenty of time to think about stuff. As Nick suggested I will go ahead with the original plan but with a slight amendment, I will make them bookshelf speakers and run them on the TV initially. Once they're in place I'll start work on the "proper" TV setup and then relegate the bookshelf speakers to the computer room. Regarding the power, I have a 20v 5amp laptop supply that I could use but I don't like power bricks sitting around so ideally I would house the power supply inside, I guess this coupled with the board means I will have to make the enclosure slightly bigger though. 25 * 15 * 15cm gives a compact form and about 0.1 ft volume but with all the stuff inside I'll increase that slightly, plus I've not drawn it out yet so I may adjust it depending on what looks good. I don't suppose you can get "wall warts" that run 20v 5amp? I did a quick google but couldn't see anything, probably a bit too much power for a small unit.

Regarding the enclosure, is it worth porting?

Good advice about the 2.1 setup Douglas, I hadn't thought about that and it makes perfect sense, I will probably stick with stereo initially.

Thanks again for your help guys, I've got a much better idea of what i'm doing now, and thanks for the links, I'll start looking through them properly now.


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Kevin Kendrick
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09/08/2019 10:34 am  

Have run the numbers on the PS95-8's guys and I'm thinking he's going to need a HP filter around 80 hz. Without it, the driver is going to breach x-max after 3 watts. At 3 watts, you would be at 92db without BS compensation, even lower output with it. If someone else would like to look at the numbers, please do and chime in, perhaps I've made a mistake. For reference, modeled it in BassBox and these are the numbers in my simulation. VB .11cf, FB 87hz, F3 72hz. 1" flared port, 2.125" long.

Just trying to help you out here Ed, hope you're ok with it.  


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TVOR-Ceasar
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09/08/2019 10:49 am  

@douglas-blake

No biggie Douglas. I'm guilty of mis-seeing things from time to time too. Lol

-Charlie


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TVOR-Ceasar
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09/08/2019 11:16 am  

@kevin-kendrick

I'm still using the BASIC programs I adapted and modified from W.R.Hoffman's articles in Popular Electronics (in the 90's) and verified via the books I had at the time. They are not as detailed as the newer programs, so I can't check Xmax excursion, etc.

However...

Using PE's #'s, your box size and port diameter, I get:

Fb of 79 Hz

F3 of 62.5 Hz 

1" Port @ 2.35" L

Peak response of 1.5 dB above baseline.

Put them in a sealed box of the same size and:

QB = .79

Fb = 132 Hz

Sealed box with Q = Qts (.72) and it'll be 0.6 c.f. and Fb =Fo 119.8 Hz

-Charlie


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Kevin Kendrick
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09/08/2019 11:42 am  

@tvor-ceasar

Interesting. Let me go back and check the driver parameters again, I may not have their latest measurements in my software.

There have been comments on other forums about BassBox software not matching other Simulation softwares like WinISD. The differences were only minor as I recall.


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Kevin Kendrick
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09/08/2019 12:06 pm  

@tvor-ceasar

Double checked the parameters, looks like I've got the latest from their spec sheet in my software. I'm not familiar with the software you are using Charlie, there are a lot of different ones out there. Thanks for taking a look at it in your software. Looks like you're coming in almost 10hz lower on the FB and F3 in the same enclosure. When you say "peak response of 1.5db over baseline, is that essentially saying any more than that would lead to over-excursion?  


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