Hey guys,
I'm working on restoring an old boombox I've had lying around and hit a huge wall at speakers. Currently I've replaced the tuner board with a raspberry pi with i2s dac, that's hooked up to all the stock gear and it all runs well over wifi from 6 D cells. Problem is it doesn't really sound too good.
I've decided to take it a step further and ordered an amp6, got modification for 12v battery power sorted and a few other bits and pieces. The last piece of this puzzle is some speakers to replace the stockies. The box is 11ish L and potential mounting depth maxes out at about 4"
Not too knowledgeable when it comes to speakers and I'm having difficulty finding something which will fit and falls into what has been mentioned to work well spec wise.
I'm working on restoring an old boombox I've had lying around and hit a huge wall at speakers. Currently I've replaced the tuner board with a raspberry pi with i2s dac, that's hooked up to all the stock gear and it all runs well over wifi from 6 D cells. Problem is it doesn't really sound too good.
I've decided to take it a step further and ordered an amp6, got modification for 12v battery power sorted and a few other bits and pieces. The last piece of this puzzle is some speakers to replace the stockies. The box is 11ish L and potential mounting depth maxes out at about 4"
Not too knowledgeable when it comes to speakers and I'm having difficulty finding something which will fit and falls into what has been mentioned to work well spec wise.
I assume the boombox is a typical plastic variety with leaky enclosure with the usual slots and grill all over the back side? If this is the case you want to look for a driver with a high Qts at least 0.9 or more to get reasonable bass. Usually this means the driver will be less expensive as the magnet is smaller. Car audio speakers are good for this - a 6.5 inch coaxial with dome tweeter would work well and not cost much. Pioneer makes a nice one for about $40/pair. If you want a true full range look at the Visaton FR series or look at MCM for their budget priced drivers in this size range and with higher Qts. I am not familiar with Amp 6 but the current high performance low price low power consumption amp king is the TPA3116D2. Check that thread out - $20 50w/ch amps sound very good.
Yep pretty standard boombox config, and on the small side too, its a sanyo m9935k. I did pick up a pair of visaton FR 6.5 but not sure if they'll work too well with the amp6, they're an ok fit but a little modification will be required.
Read up a little on the king amp you suggested and given the price have ordered one that suits my available voltage, it seems as though it may better suit those FR 6.5s.
Also have an entire car system spare however those speakers always have crazy watt specs on them - are these hugely relevant or are there other figures which are of more importance?
Read up a little on the king amp you suggested and given the price have ordered one that suits my available voltage, it seems as though it may better suit those FR 6.5s.
Also have an entire car system spare however those speakers always have crazy watt specs on them - are these hugely relevant or are there other figures which are of more importance?
Wattage specification is the maximum amount of power you can stick in there before the smoke comes out. You can put any amount of power you like in, up to and including the maximum rating, and it'll be fine. Going beyond the maximum power rating involves voodoo, and is best left to those that want the last bit of performance, and are willing to put the longevity of their equipment to the test.
FWIW, car drivers rarely live up to specs. A 9x6 coaxial capable of 1000w? Not a chance. Electric heaters dissipate 1000w (or more). That little voice coil would burn before you got close. Look for RMS ratings - that 9x6 co-ax is probably 50w RMS, which represents something like the true power you can put in for any length of time.
HTH
Chris
FWIW, car drivers rarely live up to specs. A 9x6 coaxial capable of 1000w? Not a chance. Electric heaters dissipate 1000w (or more). That little voice coil would burn before you got close. Look for RMS ratings - that 9x6 co-ax is probably 50w RMS, which represents something like the true power you can put in for any length of time.
HTH
Chris
thanks for the pointers - so as an example for 20w RMS 40w max speakers, id generally be better off using the 25w amp which come closer to RMS, than the 50w amp which is closer to max?
might I get a little more out of them using the 50w and taking a little care with the volume control? at the price tags on speakers i'm using for current projects it certainly wouldn't be the end of the world if I blew one, but if it's certain death then I might as well not bother.
might I get a little more out of them using the 50w and taking a little care with the volume control? at the price tags on speakers i'm using for current projects it certainly wouldn't be the end of the world if I blew one, but if it's certain death then I might as well not bother.
Chances are it'll start sounding bad before the drivers blow. Even with the 50w amp, unless you're playing incredibly compressed music, the amp will clip before you hit the continuous rating of the speakers.
If it were mine, I'd probably play it safe and go 25w. Its still plenty enough.
Chris
If it were mine, I'd probably play it safe and go 25w. Its still plenty enough.
Chris
I don't know if most amps now clamp when they reach clipping. If the amp doesn't clamp, a clipped waveform can considerably exceed the amp's rated output which is stated for a certain percentage distortion.
One of the class D amps like the tpa3116d2 or 3110d2 can run from supplies ranging from 6 to 24v. If you power it with a 2amp 12 volt wall wart you can't exceed 25w. But really more like 22w with efficiency losses. Use smaller supply and you should be safe.
Maybe for a 2 amp 12 volt situation, but since a typical wall wart has no current limiting it may provide much more current until it burns itself out. Without thinking I once blew a 100 watt speaker with a 50 watt amp by overdiriving it. I failed to realize that when approaching a square wave only the capacity of my power supply was limiting the output to the speaker.
The SMPS wall warts that I use don't have the ability to drive more than they are rated for. I guess I have never had an issue with blowing a 30 w driver with a 50 watt amp.
SMPS wall warts may be more limited since they are a bit dinky but thrift stores still have many linear supply wall warts lying around. I think I only have one SMPS wall wart in the house.
Of course I didn't blow my driver with a wall wart or a class D amp, it was with a Kenwood receiver. Funny thing is that I knew better, but just wasn't thinking about what is happening with clipped waves and when rms falls by the wayside. Without giving it any analysis I just casually assumed I was safe since the speakers were rated higher than the amp.
Of course I didn't blow my driver with a wall wart or a class D amp, it was with a Kenwood receiver. Funny thing is that I knew better, but just wasn't thinking about what is happening with clipped waves and when rms falls by the wayside. Without giving it any analysis I just casually assumed I was safe since the speakers were rated higher than the amp.
I assume in the case of a battery it can draw whatever it wants? Causing problems for speakers, amp and the battery?
It pretty much can, yes.
Though I'd always put a fuse in series with anything like a SLA battery. If shorted, they go out with a BANG. With the fuse mounted as close as possible, all you'll do is blow a fuse.
If you exercise some sensibility with the volume control, ie, "its sounding a bit rough, so I'm not turning it up any louder", everything will be fine. You could put a fixed attenuator in there, so when everything's turned right up, you're just about clipping.
Chris
Though I'd always put a fuse in series with anything like a SLA battery. If shorted, they go out with a BANG. With the fuse mounted as close as possible, all you'll do is blow a fuse.
If you exercise some sensibility with the volume control, ie, "its sounding a bit rough, so I'm not turning it up any louder", everything will be fine. You could put a fixed attenuator in there, so when everything's turned right up, you're just about clipping.
Chris
cool thanks for the advice, will throw a fuse in the plans.. as far as fixed attenuator what am I looking at, I'm familiar with the use of a gain dial but that's about as far as it goes
Couple of resistors in series with the input would do the job, though you'd need to experiment a little.
Or you could put in a pair of those PCB-mount little potentiometers in there, run the external volume wide open and turn those down until it sounds clean-ish, and then call it good.
Chris
Or you could put in a pair of those PCB-mount little potentiometers in there, run the external volume wide open and turn those down until it sounds clean-ish, and then call it good.
Chris
- Status
- Not open for further replies.