Help me improving my portable sound system

[komig]

Hallo Diyaudio.

Thanks for the great community helping each other. I have spent a lot of time here and now I hope you will help me. 🙂

Last year I rebuild my sound system, designed from the Boominator concept. (The fourth version, improved every year since 2010)

It looks like this:
Soundsystem

I designed it like that because I need it to fit in my cargo bike so I easy can get it around.
CargoBike 1
CargoBike 2
CargoBike 3

I’m generally satisfied with it but I like improving it and make it better. This year I can’t decide what to improve and therefore I ask you for help.

Often I find that its lacking bass and when it’s played loud the sound quality is not that great. That’s two things I defiantly would like to improve.

At the moment the components in the build are:
Player:
Raspberrie Pie B 2

Dac:
E-DAC 24 bit Miniature USB DAC

Amp:
41Hz AMP9 (TA4100) (Bought from Vbro, 41hz forum)

Speakers:
4 * P.audio HP-10W 8 ohm
4 * Piezo Tweeter MPT-001

Power Source:
12V Acid battery + 12V – 24V inverter. At the moment I’m planning to order lifepo4 batteries.

When I bought the amplifier from Vbro he made a step-up/gain device that also split a phono to 2 x phono.

Here is an image showing the wiring:
Wiring

Last year I bought a Fiio MONT BLANC-E12 and used it as a pre-amp. It did not give the better sound and bass I wanted.

The two golden rules is portable (needs to fit the cargo bike with space to a battery) and energy effective (AMP9 consumes around 35W at 100% volume (loaded with 4 Ohm) there is room for a higher power consumption but I need to know how much to calculate my power usages).

I made 7 ideas and I want your input what could be the best solution.

1. Better Amplifier
Is there a more suitable amplifier on the market today? If I found a 100W-200W with two channels could it solve my problem? Maybe one running with higher voltages then AMP9.

2. Mini DSP
If bought a Mini DSP could it solve my problem? At the moment I have no crossover.

3. Re wiring
Could I re wire the speakers to get 2 Ohm? Or can I bridge the output of the AMP9 to gain power?

4. Extra (bass) speaker
Not much space are left but if I could build one or more speakers on the system and rewire the system what could I possible gain?

5. Better speakers
Are there some speakers out there that are more effective and have the same size?

6. New design
I love my current design but if you think that is my problem let me know.

7. Pre AMP
Would gaining the input signal give me any advantages?

If you have any other idea please let me know and thank you for taking your time to read my post. 🙂

 

[lutkeveld]

That's not a Boominator, that's a construction with similar drivers. The Boominator is a specific setup with the drivers mounted magnet to magnet in a specific cabinet volume with a specific bass reflex port (the handle).

1) That's not where you can gain the most. You will lose cash and play time for a minimal increase in output. Also you would have to have speakers that can handle more power.

2) MiniDSP won't do much at the moment. Do you have a resistor in line with tweeters?

3) Nope, with 4 8ohm speakers you can only get to 2x 4 ohm.

4) You could do that; a Cubo12 or Cubo15.

5) Meh, not really

6) Yeah, build a real Boominator

7) Not unless your signal is too weak to max out the amp. But you already used a pre amp without any succes right?

 

[komig]

1) That's not where you can gain the most. You will lose cash and play time for a minimal increase in output. Also you would have to have speakers that can handle more power.

There is no other Amplifier using around 30-40W power that can output more then AMP9? The AMP9 is a 100W amplifier but around 50W the THD+N gets very high. The speakers can handle 100W so a amplifier with a low THD+N at could be nice.

Datasheet of TA4100

2) MiniDSP won't do much at the moment. Do you have a resistor in line with tweeters?

I have no resistor at the moment. Every speaker is directly plugin to the amplifier as showed in the wiring draw.

3) Nope, with 4 8ohm speakers you can only get to 2x 4 ohm.

My thought was to bridge the amplifier so it got two channels then somehow wire the speakers and twitters to make it run 2 ohm.
Because of the the four channels it should in theory could power the double amount of speakers then the AMP6.

4) You could do that; a Cubo12 or Cubo15.

I will look more into that. Need to find out if it will fit the cargo bike.

6) Yeah, build a real Boominator

How much gain do you think I will get? My design is calculated with the program WinISD. The volume and bass reflex port should be calculated after four p.audio hp10w speakers

7) Not unless your signal is too weak to max out the amp. But you already used a pre amp without any succes right?

The sound quality did not increase with the Fiio MONT BLANC-E12

Thanks for your respond. 🙂

 

[lutkeveld]

The AMP9 uses ~20W. It already has lots of output, you're on the border of what the P.audio HP10W's can handle.

You might consider to put a 47 ohm resistor in series with the tweeters to reduce harsness and increase amp stability.

How many liters is your enclosure and what is your tuning frequency at the moment?

 

[komig]

The AMP9 uses ~20W. It already has lots of output, you're on the border of what the P.audio HP10W's can handle.

You might consider to put a 47 ohm resistor in series with the tweeters to reduce harsness and increase amp stability.

How many liters is your enclosure and what is your tuning frequency at the moment?

The power usages i got from Saturnus calculation in the boominator topic, 20W is lower then I calculated. 😀
The P.audio HP10W is running 100W RMS and 200W peak correct?
Because from the TA4100 datasheet the AMP is not running nice after 50-60W.

If you look at my wiring Wiring link
How would you do the wiring with the resistor? I know the wiring with the AMP6 but with four channels i can't get it to fit.

My enclosure should be close to 215L and turning freq 48.85 Hz

Here is my calculations i used to build the box:
Calculations

I know the sound system is not a box but I calculates the roof in the box and therefore we have the 215L.

 

[komig]

Here is my Bass Reflex tube.
Bass Reflex tube

I got four of them in the build.

 

[lutkeveld]

It's around 35W at 24V with 4 ohm drivers, but you're using 8 ohm drivers so consumption is 'only' 20W.

You should wire it up so that it has one woofer and one tweeter on each channel. Then a 47 ohm resistor in series with each tweeter.

Your calculations are probably done with Q=0.707, which gives maximum flat response indoors. Outdoors you want a more peaking response to compensate the lack of room gain. The Boominator has the 4 drivers in a total of ~55 liter with a ~65Hz tuning.
If you want to reconstruct your current setup without any significant cost you could rewire the speakers and make the tuning higher.

If you want to go all out you can build a proper Boominator paired with a Cubo 15.
Be prepared to spend a lot of time and money but in exchange for a ballin' setup ;p

 

[komig]

It's around 35W at 24V with 4 ohm drivers, but you're using 8 ohm drivers so consumption is 'only' 20W.

You should wire it up so that it has one woofer and one tweeter on each channel. Then a 47 ohm resistor in series with each tweeter.

Your calculations are probably done with Q=0.707, which gives maximum flat response indoors. Outdoors you want a more peaking response to compensate the lack of room gain. The Boominator has the 4 drivers in a total of ~55 liter with a ~65Hz tuning.
If you want to reconstruct your current setup without any significant cost you could rewire the speakers and make the tuning higher.

If you want to go all out you can build a proper Boominator paired with a Cubo 15.
Be prepared to spend a lot of time and money but in exchange for a ballin' setup ;p

I thought when you put two 8 ohm speakers in parallel it gave me 4 ohm but the tweeter does not count as a speaker correct?

That means that the AMP9 actually can drive two Boominators?
Channel 1+2 to the 8 speakers like the AMP6 then Channel 3+4 for a set more?

Then you suggest building the real Boominator plus a Cubo 12 or 15? 😛

I have build the mini Boominator:
Mini Boominator

I will consider rebuilding it but first i would take your advice and rewire each channel with a tweeter and a speaker plus the 47 ohm resistor.

Is there a reason why we only put a resistor on the tweeters, don't they both require to cut off some frequency for best quality?

A big thank you for using your time to help me. 😀

 

[lutkeveld]

Piezos are a capacitive load, not a resistive load as most tweeters. Their main spec is in nF instead of ohm. I don't know how power consumption would work out in your case. With normal tweeters you put a capacitor (C) in front of the tweeter (R) to create a 1st order RC high pass filter. With a piezo you put a resistor (R) in front of the tweeter (C) to create a 1st order RC high pass filter. It cuts of the typical 5khz 'piezopeak' which makes them sound plasticy.

Boominator with a Cubo would give the best performance in the smallest form factor. If you just want to improve your current setup you have to buy 4 resistors and new bass reflex ports. Rewire it and tune it higher. If that doesn't give satisfactory results you could cut to the chase and do a complete rebuild.

Quick MSpaint drawing on the wiring:
(W)oofer, (T)weeter. Black box is the resistor.

An externally hosted image should be here but it was not working when we last tested it.

Nice job on the Mini! Do you have more pictures for me?

 

[komig]

Piezos are a capacitive load, not a resistive load as most tweeters. Their main spec is in nF instead of ohm. I don't know how power consumption would work out in your case. With normal tweeters you put a capacitor (C) in front of the tweeter (R) to create a 1st order RC high pass filter. With a piezo you put a resistor (R) in front of the tweeter (C) to create a 1st order RC high pass filter. It cuts of the typical 5khz 'piezopeak' which makes them sound plasticy.

Boominator with a Cubo would give the best performance in the smallest form factor. If you just want to improve your current setup you have to buy 4 resistors and new bass reflex ports. Rewire it and tune it higher. If that doesn't give satisfactory results you could cut to the chase and do a complete rebuild.

Quick MSpaint drawing on the wiring:
(W)oofer, (T)weeter. Black box is the resistor.

An externally hosted image should be here but it was not working when we last tested it.

Nice job on the Mini! Do you have more pictures for me?

Does that mean when i'm put two P.Audio HP10W on channel 1 & two P.Audio HP10W on channel 3 that i have 4 or 8 ohm? And no load on the on 2 & 4? That sounds like it could damage the AMP? 😱

I will start looking at building a Cubo and then the Boominator on top.

Yes, let me see:
Gallary
I can take some more later. 🙂

The speakers is of curse identical on both side. It have a Bluetooth module build ind and i manage to wire the AUX so it works both as IN and OUT. 😀

 

[lutkeveld]

No, read it again. One woofer and one tweeter per channel.

 

[komig]

No, read it again. One woofer and one tweeter per channel.

I know. I will change it so it have one woofer and one teeter per channel. 🙂

I talk about the current setup i have been running the last two years. I just heard that if there is no load on the AMP9 on some of the channels it can damage it.

Because at the moment with two woofer on channel 1 & 3 that one should run 4 ohm or? and channel 2 & 4 with two tweeters each how no load or a different kind. 😕

 

[lutkeveld]

Now 2 channels have a resistive load (speakers), the other two have a capacitive load (tweeters). The AMP9 isn't made for a capacitive load, it can causes issues. So it's better to wire it up the way I posted it. Having no load can also causes issues.

After wiring it up correctly and tuning it higher; report back to tell us if / how much the sound improved 🙂 Should be a big difference.

 

[komig]

Now 2 channels have a resistive load (speakers), the other two have a capacitive load (tweeters). The AMP9 isn't made for a capacitive load, it can causes issues. So it's better to wire it up the way I posted it. Having no load can also causes issues.

After wiring it up correctly and tuning it higher; report back to tell us if / how much the sound improved 🙂 Should be a big difference.

Great! I will do that ASAP and hopeful get a good result. 🙂

 

[komig]

You should wire it up so that it has one woofer and one tweeter on each channel. Then a 47 ohm resistor in series with each tweeter.

Your calculations are probably done with Q=0.707, which gives maximum flat response indoors. Outdoors you want a more peaking response to compensate the lack of room gain. The Boominator has the 4 drivers in a total of ~55 liter with a ~65Hz tuning.
If you want to reconstruct your current setup without any significant cost you could rewire the speakers and make the tuning higher.

Okay, I did put in the resistor as you advised me and the sound got better. So that was a good thing for a start. 😀

I still thinking about building doing something with the case.

You mentioned that I build after Q=0.707? What variable should i go for on a outdoor sound system? 🙂