20w amp speakers? also, can i attach bass and tweeter

Breakout boards, sensors, other Adafruit kits, etc.

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
arjunmenon
 
Posts: 27
Joined: Thu May 08, 2014 2:10 am

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by arjunmenon »

Hi
Require advise while selecting/comparing speakers.

Image

Specification description of
- Power capacity(RMS)
- Power capacity(peak)
- Maximum Excursion
- Resonant Frequency
- Total, Electrical, Mechanical Q
- Xmax
- Compliance

Any other notes.

(source - http://www.madisoundspeakerstore.com/ap ... lder-pads/)

User avatar
adafruit_support_bill
 
Posts: 88087
Joined: Sat Feb 07, 2009 10:11 am

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by adafruit_support_bill »

For use with this amplifier, you want the RMS power capacity to be 10W or more for an 8 ohm speaker and 20W or more for a 4 ohm speaker. The "sensitivity" tells you what sound pressure level you can expert per watt of input.

The other parameters are useful for designing enclosures and crossovers. That is beyond the scope of this forum, but there are plenty of books on the subject, as well as DIY audio forums specializing in speaker building.

arjunmenon
 
Posts: 27
Joined: Thu May 08, 2014 2:10 am

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by arjunmenon »

Hi
I had a discussion with one engineer of Maxim Integrated about clipping.
He advised to place a diode-resistor network(BAV99 and R3) b/w the capacitors C22/C23 and the resistors R8/R9.
Link for ref - http://pdfserv.maximintegrated.com/en/an/AN4551.pdf

Can you please help me verify the integrity.

Also, the said diode is a switching diode with 3 pins. If you approve, how can I connect it. Shorting 1 & 2 pins connected with 100 Ohm R? Right.

Thanks.

User avatar
adafruit_support_bill
 
Posts: 88087
Joined: Sat Feb 07, 2009 10:11 am

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by adafruit_support_bill »

That should work to limit the input signal. The circuit shown is for a single channel amplifier and the diode/resistor network is wired between in+ and in-. For a stereo amplifier like the MAX9744, you would need two of these circuits. One would go between INL and AGND and the other between INR and AGND.

arjunmenon
 
Posts: 27
Joined: Thu May 08, 2014 2:10 am

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by arjunmenon »

I cant seem to figure out the exact placement in the PCB layout. In the schematic however I presume it should be placed as if, the BAV99 output pin no. 3 to be b/w C22/R8 and pin 1&2 with R of 100 Ohm connected to AGND.
Then another output pin of BAV99 b/w C23/R9 and the other pins with AGND. I hope you can make out.

But I cant figure out with the PCB layout. Can you guide me through.

(Online paint - http://svg-edit.googlecode.com/svn/bran ... ditor.html
to help me explain, if required)

arjunmenon
 
Posts: 27
Joined: Thu May 08, 2014 2:10 am

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by arjunmenon »

Can someone tell me what can I do to create a voltage booster. I need to know the current requirement for the amp. Pls assist.

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by adafruit_support_mike »

Your previous questions were about a diode limiting circuit to keep the input within a certain voltage range. Are you using the term 'voltage booster' to refer to the same thing?

arjunmenon
 
Posts: 27
Joined: Thu May 08, 2014 2:10 am

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by arjunmenon »

Nope its not that.
I want to see if the amp can be powered by batt. Since Li-Pol Batt are of standard values and well below the min voltage of amp, so I would require a voltage booster to get it within the range. But I checked the datasheet to know the min current. I wont go high with voltage - 5v or max 8v. But cant get the current rating for it. There a dozen ICs for that range but the current rating is around 200mA or 300mA. Will it be sufficient.

Also, what about joule thief, can it deliver the required ratings. The voltage can go high with cheap and less components.

Pls advise.

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by adafruit_support_mike »

The minimum supply necessary to get 20W through a 4 ohm speaker is 9v @ 2.25A.

The Joule Thief is a simple flyback converter, but you'd have trouble getting more than about 50mA out of one. Flybacks are better at high voltage than high current. If you want a self-oscillating boost converter that can work in the 2-3 amp range, you'll probably end up using a Royer circuit. It will probably be easier to find a chip that can handle that power range though.

Regardless of what circuit you use, you'll need at least a 5500mAh cell for your supply. Power stays the same no matter how you arrange the voltage and current, so even assuming 100% conversion efficiency it will take about 5.5A @ 3.7v to produce a 9v @ 2.25A supply suitable for driving speakers. LiPos are generally rated to discharge safely in 1 hour, so the amount of current you can pull from one depends on how much energy it can hold.

It would probably be easier to get an 11v LiPo pack used for self-powered airframes than fuss around with a converter.

sleeper42
 
Posts: 2
Joined: Tue Jul 08, 2014 11:23 pm

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by sleeper42 »

I just built a Bluetooth speaker using this amp. It is enclosed in a subwoofer box. One of the drivers came with the sub, and I mounted another "full range" driver on the other side of the box. Its not too bad, but some of the low/mid frequencies are muffled and not great.

My question is: is there a way for me to send a mono (Left and Right combined) signal to both drivers? That way I can put a low pass filter on the sub speaker and hopefully improve the overall sound? The signal going into the amp is stereo from a Bluetooth USB receiver. I'm guessing the signal going into the amp would be need to be dual mono?
Any help, thoughts, recipes would be appreciated. Thanks!

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by adafruit_support_mike »

@sleeper42: Your question doesn't seem to be related to the ones in this thread. Please start a new thread and we'll help you there.

arjunmenon
 
Posts: 27
Joined: Thu May 08, 2014 2:10 am

Re: 20w amp speakers? also, can i attach bass and tweeter

Post by arjunmenon »

Got a general idea.

Thanks.

Locked
Please be positive and constructive with your questions and comments.

Return to “Other Products from Adafruit”