MTM and Two Chanel amp

[Chrispy61]

As above, what would be the best way to wire this all up. The mids are 6 ohms and the tweeter is 8. The amp is a tda4792 Bluetooth amp.

I was thinking running one mid and tweeter in parallel off one channel and the other mid on its own channel.

 

[ewollowe]

Hi Chris,

I think most people would run the mids from one channel and the tweeter from the other. Much easier to make a crossover that way.

 

[Chrispy61]

Hi, thanks for the reply.

I understand the way you mean but wouldn't you be losing a lot of wattage doing it that way? The amp is rated at "50 watts" a channel so that's split between the two mids and the other 50 all for the tweeter, some of which will be reduced with the crossover

 

[ewollowe]

Speakers are all about compromises, most design choices have pros and cons. Keep researching.

 

[adason]

Hi, thanks for the reply.

I understand the way you mean but wouldn't you be losing a lot of wattage doing it that way? The amp is rated at "50 watts" a channel so that's split between the two mids and the other 50 all for the tweeter, some of which will be reduced with the crossover

At normal listening level, you will likely be using 0.5 watts...

 

[rabbitz]

The amp is the TDA7492 (not familiar with it BTW)?

Running the MTM woofer in parallel will give 3 ohm which will probably kill the amp and in series will give 12 ohm where the amp would have lower power.

Suggest a TM or TMM or TM 2.5 way with one amp driving the TM and the other driving the second woofer M. This will place a better load for the amps.

 

[Chrispy61]

I think this is the way I might go. If I run the tweeter and a mid off of one channel in parallel, could I still use a crossover or would I have problems?

Thank you for the reply

 

[rabbitz]

You still need a crossover and the crossover to the midwoofers would be different from a MTM to a MT+M. The tweeter would be the same but each woofer would now need it's own crossover with the original values changed..... inductor x 2 and cap divided by 2 (see pic).

 

[Chrispy61]

Thanks for the reply.

This is my project so far, needs a few coats of Matt black paint and the crossover needs sorting out but happy with the progress.

 

[Hybrid fourdoor]

By separating the 2 woofers and the 1 tweeter it also gives you the ability to adjust the volume of the 2 sets individually. The tweeter will probably be different volume than the woofer. The woofers should be the same to each other. So put the woofers together on one channel and then put the tweeter in its own channel. Now you can use a volume control of some kind (like a diy preamp) to adjust the “left” (woofers) & “right” (tweeter). And if the amp has a volume control, it probably adjusts both together which is fine once they are trimmed independently.

 

[Chrispy61]

Conflicting advice as to what's the best option.

I will have to weigh up my options and decide what I want to do as far as crossover design.

My woofer's are spl 84db and the tweeter is 91 so it will definitely need to be brought in line.

 

[rabbitz]

By separating the 2 woofers and the 1 tweeter it also gives you the ability to adjust the volume of the 2 sets individually. The tweeter will probably be different volume than the woofer. The woofers should be the same to each other. So put the woofers together on one channel and then put the tweeter in its own channel. Now you can use a volume control of some kind (like a diy preamp) to adjust the “left” (woofers) & “right” (tweeter). And if the amp has a volume control, it probably adjusts both together which is fine once they are trimmed independently.

Have a look at the impedance of the woofers (see post #1&6). That's the reason for the odd bi-amp arrangement.

 

[Chrispy61]

Is the impedance of the tweeter even relevant, I thought because of the small voice coil the woofer would always have presidency as far as the amp can see?

 

[rabbitz]

No, the xo takes care of that. It's when you start to parallel woofer drivers or run them in series you can place unreasonable loads on the amp or have the impedance too high for best amp performance.

BTW.... nice job on the speaker.

 

[Chrispy61]

Thanks rabbitz. It's actually a project someone has asked me to build for them. It sounds great without any crossover but I feel it could be better.

It's the electronic gubbins I can't get my head around but some good information here that will definitely help.

 

[Chrispy61]

My woofer's are rated 65-6500hz 6ohm and the tweeter 1000-20,000hz 8ohm. I wanted to cross them over at 3000 but also lower the tweeter by 7db.

What's the best way to go about it?

I've waxed the oak and sprayed it black now

 

[PeteMcK]

L pad calculator - attenuation dB damping impedance decibel loudspeaker speaker voltage divider - sengpielaudio Sengpiel Berlin

 

[Chrispy61]

I can work that part out it's how you combine this with a crossover as I want to lower the volume but also have it cut off at 3000hz.

 

[rabbitz]

You will need to advise the brand and model of the tweeter and woofer. With that, someone may be able to help you.

 

[Chrispy61]

The speakers are made by DROK but unfortunately all I have is some ts parameters and some basic information.

Can a crossover and a lpad be combined into one circuit?