Which Amp(s) for my setup?

[Buzzyll]

Hey!
I have outdoor stereo I build a few years ago. The speakers I use are:

2x Eminence Delta 15C
https://www.musicstore.de/en_RO/RON...ker-400Watt-4Ohm-48Hz-4kHz/art-PAH0013794-000

2x CELESTION | TF-0818MR
8" mellanregister - Celestion TF-0818MR

4x MONACOR | MPT-016
Diskanthorn - Monacor MPT-016

Now I have them running on a bi-amp setup with these:
4x100W Class D Audio Amplifier Board - T-AMP-Sure Electronics AA-AB009 | eBay and Sure AA-AB32189 2x100W TDA7498 Class-D Amplifier Board | eBay

I am useing an active filter to control the low, mid and high. I do not like the setup since it is to much stuff going on... I use 2x 70ah 12V car batteries for the power.

I would like to have a different setup that is "easier" to control and connect. I would love to have a volume knob included if possible. Would be nice to maybe skip the active filter aswell and build passive filters instead. I am looking for high volume, the bass in most important. Trying to maintain a good power/battery life ratio. I had some thoughts of running the mid and high on one amp with some passive filters, and then running the 15" alone on a stronger amplifier (with passive filter aswell).

Anyone have any ideas on some amplifiers that would fit my needs? Any tips around the setup and build is appreciated.

Thanks in advance!

 

[ICG]

Ah, well, while piezos can sometimes sound good, I'd definitely get rid of them at your project. Besides that, class D and piezos will not become a happy couple without quite some effort (-> impedance at high frequencies).

 

[Buzzyll]

Ah, well, while piezos can sometimes sound good, I'd definitely get rid of them at your project. Besides that, class D and piezos will not become a happy couple without quite some effort (-> impedance at high frequencies).

Thanks for the reply. I am currently using a 4,7 uF capacitor in serie with the positive line (which was suggested by the seller). Not sure how much difference it makes though...

Anyway if I am going to use the piezo or not is a later problem I guess. The main thing here is that I want to change the amplifier setup. I guess the dual amp is just stupid... Now I have like 6 channels (3 right, 3 left). Maybe it is better to just use one amplifier (2 channels) and connect 1x Bass, 1x mid and 1x high to the right channel and vice versa? And instead of the active filter I use now, just use passive filtering on everything. Now I have so many RCA cables running everywhere between the active filter and the 6 channels...

Is it possible and better to do it the way I am trying to explain?

 

[Khron]

More often than not, i've heard / read of a series RESISTOR being used with piezo drivers - those are, in effect, capacitors in themselves. Adding further series capacitance won't do much of anything (constructive, at least).

If the many RCA cables are a problem, perhaps a better idea would be to slightly alter the amp setup, in order to have one set of amps for the left side, and one set for the right side (along with the active filters for each side). That way, you'd minimize both the signal wiring, as well as the speaker wiring length.

At least some 4-channel class-D amps can be configured as 2.1 setups (2x single-ended and one bridge-tied load). The two single-ended outputs could go to the mid and high-frequency drivers respectively, and the bridged one to the bass driver.

Switching to passive crossovers would be a step backwards, not to mention being an immense (and tedious) headache, to get the slopes and phasing and everything right. Plus there's the signal loss in those...

 

[Buzzyll]

More often than not, i've heard / read of a series RESISTOR being used with piezo drivers - those are, in effect, capacitors in themselves. Adding further series capacitance won't do much of anything (constructive, at least).

If the many RCA cables are a problem, perhaps a better idea would be to slightly alter the amp setup, in order to have one set of amps for the left side, and one set for the right side (along with the active filters for each side). That way, you'd minimize both the signal wiring, as well as the speaker wiring length.

At least some 4-channel class-D amps can be configured as 2.1 setups (2x single-ended and one bridge-tied load). The two single-ended outputs could go to the mid and high-frequency drivers respectively, and the bridged one to the bass driver.

Switching to passive crossovers would be a step backwards, not to mention being an immense (and tedious) headache, to get the slopes and phasing and everything right. Plus there's the signal loss in those...

Thanks for a long reply!
To make things clear about my active crossover, I have this one: BX55 - Boss Audio Systems
wired like this: https://s32.postimg.org/gvvlehqd1/Kopplingsbild_stereo.jpg
(haha pro paint)

I am not even sure the crossover can do the work I am looking for. I use the "subwoofer" output for the 15" the bandpass for 8" and tweets for the highpass. Some people have said the subwoofer output is useless since the speakers is not subwoofers. I know they are not real subwoofers and more like mid/bass. But my thoughts is that it is only a lowpass filter anyway, so it should do the job. Maybe I am wrong? The wiring around this crossover is really confusing, and it takes a lot of RCA cables... I would like to get rid of it and actually use some sort of passive filtering that takes less room. The problem with the active ones is also that they require wiring from the batteries aswell.

About the amplifiers, maybe this would be something?: 200W+100W+100W TDA7498 2.1 Channel Digital Power Class D Amplifier Board DC 24V | eBay

 

[Khron]

I can't comment on the prices, but i think stuff like the MiniDSP crossovers would do the trick quite nicely, for such projects. Either that, or perhaps some PA crossover / speaker management unit, if you can get one for a good price.

The trouble with chinese listings of (relatively advanced) technical stuff is that, in many cases, some of the information is (or at least can be) inaccurate. For example, at least from the block diagram in the datasheet, the TDA7498 amp chip contains two bridged amplifiers. As in, hard-wired bridged, so i doubt you can use one half of it to drive two single-ended channels. The block diagram shows a differential in/out buffer which leads me to believe that, but i could be wrong.

Something like this, though, would definitely do the job: TPA3116 50W*2+100W 2.1 Class D Digital Power amplifier Completed board New M8P3 | eBay

As far as i can tell, there's two TPA3116 chips on that board - one wired as stereo bridge-tied load (ie. two separate bridged amplifiers), and one wired as parallel bridge-tied load (where the two bridged amplifiers are paralelled, for greater current delivery capability). One of these per side should do you just fine, and it would appear that they also have some form of adjustable filters included.

That being said, i've read several accounts that the "crossover" included can be a bit odd, or some components have the wrong values etc.

 

[Buzzyll]

I can't comment on the prices, but i think stuff like the MiniDSP crossovers would do the trick quite nicely, for such projects. Either that, or perhaps some PA crossover / speaker management unit, if you can get one for a good price.

The trouble with chinese listings of (relatively advanced) technical stuff is that, in many cases, some of the information is (or at least can be) inaccurate. For example, at least from the block diagram in the datasheet, the TDA7498 amp chip contains two bridged amplifiers. As in, hard-wired bridged, so i doubt you can use one half of it to drive two single-ended channels. The block diagram shows a differential in/out buffer which leads me to believe that, but i could be wrong.

Something like this, though, would definitely do the job: TPA3116 50W*2+100W 2.1 Class D Digital Power amplifier Completed board New M8P3 | eBay

As far as i can tell, there's two TPA3116 chips on that board - one wired as stereo bridge-tied load (ie. two separate bridged amplifiers), and one wired as parallel bridge-tied load (where the two bridged amplifiers are paralelled, for greater current delivery capability). One of these per side should do you just fine, and it would appear that they also have some form of adjustable filters included.

That being said, i've read several accounts that the "crossover" included can be a bit odd, or some components have the wrong values etc.

I am still trying to figure out how to best control my system. I really appreciate that you take the time and link some stuff you think should work.

But in the end, what difference does it really make to change to the amplifier you recommended. I guess the ones I already have can give as much power, and since the 2.1 amplifier still need to be filtered in some way (the knobs only control the sound volume), I can not remove my electric crossover.

Of course I want the system to sound good. But for now it is also very important that I can eliminate as much components as possible. The big electric crossover is hard to fit in the new box I am going to create etc. What would you (or someone els here) recommend to make this work? Like I said before it would be a lot easier with for example just one amplifier and passive filters, just to reduce the wiring from the batteries and all the RCA cables. Is that possible to make or anything similar?

 

[Khron]

Well, in my humble opinion, "hardwiring" the crossover points would be a step in the right direction. Rod Elliott, over on his website, has circuit boards for sale, of Linkwitz-Riley crossovers, along with a little piece of software to determine passive component values.

Surely you won't need to have the crossover points continually adjustable forever, if you have a fixed set of speakers, do you?

And i don't suppose it's feasible to split up the system into two, ie. perhaps a piggyback-box on the rear of the speaker boxes, with a battery, 3-way crossover and a 3-channel amplifier (or 2-3 separate smaller amps), is it?

 

[ICG]

Thanks for the reply. I am currently using a 4,7 uF capacitor in serie with the positive line (which was suggested by the seller). Not sure how much difference it makes though...

Anyway if I am going to use the piezo or not is a later problem I guess. The main thing here is that I want to change the amplifier setup.

No, that's something you have to plan in advance. The problem is, the extreme impedance interacts with the output filter of the class-D amp and changes the response a lot.

This is what it looks for 'normal' impedances, from 4 to 16 Ohm:

(Taken from this site)

It can vary how the response will look like, depending on to which output impedance the filter is optimized, different impedances will always lead to different responses though.

And this is how the impedance of a piezo tweeter looks like:

You can see, the impedance is around 100 Ohm at 10kHz. That's a vastly high impedance for a class-D amp. The interaction between the piezo and the output filter will give you a huge peak. If you want to use piezos you should either compensate for the impedance or use a non-class-D amp for the tweeters or swap the output filter of the amp (not suggested for just piezo use).

 

[Buzzyll]

No, that's something you have to plan in advance. The problem is, the extreme impedance interacts with the output filter of the class-D amp and changes the response a lot.

This is what it looks for 'normal' impedances, from 4 to 16 Ohm:

(Taken from this site)

It can vary how the response will look like, depending on to which output impedance the filter is optimized, different impedances will always lead to different responses though.

And this is how the impedance of a piezo tweeter looks like:

You can see, the impedance is around 100 Ohm at 10kHz. That's a vastly high impedance for a class-D amp. The interaction between the piezo and the output filter will give you a huge peak. If you want to use piezos you should either compensate for the impedance or use a non-class-D amp for the tweeters or swap the output filter of the amp (not suggested for just piezo use).

I dubblechecked how it was wired. And it was actually a 47ohm resistor in serie with the piezo (no capacitors). I digged through my email and found the conversation with the store I bought the speakers from. They told me the following about the piezo:

"The 8 ohm resistor is only for the capacitor to split at the correct frequency.

As you are using an active filtering, you can skip 8 ohm resistor and capacitor. If you are going to connect 3 pcs in parallel, connect a 47 ohm resistor to each tweeter + connector, so that the amplifier will get a reasonable load.

Good luck"

So that is how it is wired right now. I gladly change it, if someone helps me with the components. I am planning to use the piezos I have.

 

[OffGridKindaGuy]

Short the Piezo drivers with a 33 ohm resister. (5 watt?) Add some series resistance between the source to the driver(s) Start with ~80 ohms and decrease to increase SPL. Be careful.. A couple of ohms makes a noticeable difference..

You can add a cap to choose a frequency range but design with the total resistance of the circuit..