Making amp32 louder?

[legend95]

Hi, at the moment I am using my amp32 with a 4ohm 6.5" car speaker with a sensitivity of 92db. The audio source is from my iphone and it is being powered by an 11.1v lipo battery. However, it is not quite as loud as i want it to be. Therefore to make it louder I thought getting a more efficient speaker would work because I heard that increasing the speaker sensitivity by 3db is the equivalent of turning up an amplifier up twice as much. Parts express has several highly efficient 6.5" speakers.
This speaker: http://www.parts-express.com/pe/show...number=290-682 has a sensitivity of 99.8db, however its impedance is 8ohm. I was wondering if the higher impedance would effect how loud the speaker would be by a significant amount, and if this speaker should be louder than my current speaker? What is the more important factor: speaker impedance or sensitivity when considering volume?
There is also this speaker: http://www.parts-express.com/pe/show...umber=292-2584 however it has an impedance of 3ohms, would the amp32 be able to cope with that low impedance and if not, would adding a 1ohm resistor help? If anyone knows of any other 6.5" highly efficient and quite slim speakers I would really appreciate it.
Another way of making the amplifier louder would be to add a preamplifier, however what is the maximum audio input the amp32 can handle?
Is there is any other way of making the amp louder without changing the power supply?
Thanks, any advice would be very helpful

[gnome]

yeah you're only going to make it louder by making your speakers more efficient, the problem is that as speakers get more efficient they do it at the expense of bass, if you look at the frequency response plot you can see that the aplha 6 is useless below 500HZ.
Another way is to increase surface area, ie install two drivers instead of one, this has the benefit of halving the impedance aswell so you get more power, I do understand that 2 Ohm is okay for the amp32, if you only have space for one driver than your best bet is that 3 Ohm Pyle

[V-bro]

Yes, the 3 ohm Pyle looks the most promising of the two, yet might still be a bit bass shy. Like Gnome says higher efficiency is always at the expense of bass response. It's much like gear shifting, off course the engine determines the performance in the first place, but then the chose gear will make it either accelerate fast or run higher top speed. This in a speaker is done by the voice coil winding length. A shorter coil will move less far, thus will raise the efficiency. A longer wound coil will make a longer hub, thus lowering the resonsance frequency, but this will eat the efficiency...

If your aim is mainly loud at the expense of pleasant sound the Pyle looks good, but for more pleasant sound you might want to shop for something in the middle.

Another guy at the forum was looking at these and I found them pretty interesting, and more affordabel too!
https://www.madisound.com/store/prod...roducts_id=554

Here I posted a simulation in a sealed box:
http://www.41hz.com/forums/showthrea...p6-basic/page5

But like Gnome mentioned adding more moving surface helps a lot as well!

Then the AMP32 gain, what resistors are on there now?

[legend95]

Thanks for the advice i think I'll go with the Pyle then. I think I am using the 22.0kohm resistors. When you say more moving surface, I don't have any space for another 6.5" speaker but what if I added two small 3" speakers, would this make a noticeable difference to the sound?

[gnome]

yeah there will be a difference, it'll sound worse because you're going to send the same signal to two different drivers with vastly different responses and you'll get cancellations and additions, ie a mess, and while they are trying to keep up with the 6" there is also the possibility that you'll toast the 3" drivers.

[gnome]

btw is this in your car?

[V-bro]

Exactly!

No, get the Pyle, I'm pretty sure they'll be loud!

But the 22K got is just one part... There are two resistors in there per channel. If you've got four 22K in there no wonder it's not very loud... I recommend ~12K Rin and ~82K Rfbk for such an application.....

[legend95]

I'm not using this in a car as I'm just 15 and don't have a car yet. I'm using this in my school bag, which doesn't have very much space because I need to fit all my school books in there as well. It also means there is not enough space for a speaker box, so I'm not too worried about the speakers not having a good bass response because there won't be much bass without a box anyway. The speaker will be mounted on some polyurethane foam (at least I think thats what it is) because it seems to enhance the sound a little, its lightweight and provides an easier way of mounting the speaker onto the fabric of the bag. However, the back of the speaker is left open which means that all sound behind it is wasted, so I was wondering if it would help if I were to seal the back of the speaker so less sound is wasted? This was one of the reasons I liked the alpha 6 because it had a sealed back. Also, is there any other way of getting a good sound out of a speaker within a limited space and without a proper enclosure?

Oops, I think I did solder on four 22k resistors, I just followed the BOM in order and by the time I reached the alternative values I had already soldered on the 22k resistors. Are the 12k and 82k included in the kit as alternative values or would I have to buy them. if I have to buy them what size do I need to buy so they will fit on the board and where would I buy them from? Also I am not sure where to place the resistors so would it be possible the post a sketch or photo showing where I need to solder the resistors. Damn its going to be fiddly unsoldering those resistors! Thanks

[FFF]

If it's to difficult to take out R-feedback (R5+R6), then you could try soldering a 22k (or whatever you might have) over/parallel-to R-in (R2+R4).
Impedance will drop by half but will still be acceptable I think. Gain will double.
Edit:
Iphone is connected on headphone-out I suppose: so you could go down lot more, like 4k.....use a 5k then.
Gain will be 47/4= 12 as apposed to 1. No need for new speakers then.......
Try with a 10k-ish first, then if need be....another 10k. Push that amp32!
(within limits: power-supply voltage + speaker impedance)
PS
Try to use metal-film resistors, but that will be a whopping 20cts more....

Oops, I think I did solder on four 22k resistors, I just followed the BOM in order and by the time I reached the alternative values I had already soldered on the 22k resistors. Are the 12k and 82k included in the kit as alternative values or would I have to buy them. if I have to buy them what size do I need to buy so they will fit on the board and where would I buy them from? Also I am not sure where to place the resistors so would it be possible the post a sketch or photo showing where I need to solder the resistors. Damn its going to be fiddly unsoldering those resistors! Thanks

[V-bro]

You'll notice on AMP32 that as soon as you re-do the solders the resistors start moving before you know. The traces are so tiny that there is hardly any effort necessary to melt both ends. Normally this is not so advantageous!

Indeed you can solder the two 22K which are now nearest to the tripath chip on top of the other two to get 11K. Then there should be 47K in the bag, you can first try what that does.... That should already be plenty louder!

Then a speaker without enclosure will not even be able to reach under a few hundred hz anyway.... 500 perhaps... So then forget really pleasant sound. Do you want to keep the speaker incognito? Otherwise you could also choose for placing a speaker on the outside of the bag? If you want to make it a really smart system you could perhaps make a speaker box which can be opened to fit school books!