Ok i have built the enclosure and I have the amp (TDA7498). The mids and highs are very good, but im getting barely any bass at all, imagine turning a bass knob all the way down to 0, that is how much bass I get.
But with one speaker plugged in, I get a very good bass output, but as soon as I plug the 2nd one in, almost all bass disappears. It seems like it is cutting of at like 150 Hz. I'm not even getting a mid-bass thump.
I have tested with another class D amp I have laying around (TDA7492P). It's much less powerful than the TDA7498 but I still get the bass I desire with that amp, with both speakers connected.
What is going on? Any suggestions?
EDIT: Okay now im really confused. With both speakers connected and playing (with the abnormally low bass output). I can hear the bass again, if i just slightly push and hold on one of the speakers while they are playing music. The same with the other speaker. If i were to push and hold both speakers while playing, there is no difference, only when doing it on one of the speakers.
But with one speaker plugged in, I get a very good bass output, but as soon as I plug the 2nd one in, almost all bass disappears. It seems like it is cutting of at like 150 Hz. I'm not even getting a mid-bass thump.
I have tested with another class D amp I have laying around (TDA7492P). It's much less powerful than the TDA7498 but I still get the bass I desire with that amp, with both speakers connected.
What is going on? Any suggestions?
EDIT: Okay now im really confused. With both speakers connected and playing (with the abnormally low bass output). I can hear the bass again, if i just slightly push and hold on one of the speakers while they are playing music. The same with the other speaker. If i were to push and hold both speakers while playing, there is no difference, only when doing it on one of the speakers.
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Solved it.
After some deep breaths and many thoughts, I came to the conclusion that both the amp and the speakers are fine, and should not be faulty. So according to my brain, it had to be something at the input signal, maybe the ground isn't making full contact. Checked all the connections and they looked good.
Started thinking a bit more, then I realized I also have a 3.5mm extension cable connected to the amps 3.5mm cable, since it's so short. Unplugged the extension cable and plugged the 3.5mm jack from the amp directly to my phone and the bass is back to tickling my pubic hair.
All this trial and error and the issue was a 3.5mm cord. I will now set fire to the cable multiple times, toss it in the river and hope an octopus swallows it.
After some deep breaths and many thoughts, I came to the conclusion that both the amp and the speakers are fine, and should not be faulty. So according to my brain, it had to be something at the input signal, maybe the ground isn't making full contact. Checked all the connections and they looked good.
Started thinking a bit more, then I realized I also have a 3.5mm extension cable connected to the amps 3.5mm cable, since it's so short. Unplugged the extension cable and plugged the 3.5mm jack from the amp directly to my phone and the bass is back to tickling my pubic hair.
All this trial and error and the issue was a 3.5mm cord. I will now set fire to the cable multiple times, toss it in the river and hope an octopus swallows it.
The speakers are wired correctly. On the input terminal on the amp, I have 3 pins. One for ground, left and right channel. If all three are connected, as they are suppose to, I get barely any bass.
If i unplug either the right or the left channel, the bass comes back, although now, only in one speaker obviously. The whole output dB drops as soon as the bass hits.
Solved it before by replacing the 3.5mm cord, but the problem is back. Tried with a third 3.5mm cord and still the same. Not sure what to do.
This strongly implies that one is wired opposite polarity, so acoustically ~cancel out.
In looking at fig. 5.1, this clearly shows isolated negative speaker outputs, so why only a 'three pin' connection, ergo how are the speakers wired to the returns? http://www.st.com/web/en/resource/technical/document/datasheet/CD00244535.pdf
GM
edit: Have you disconnected the speakers and used a 1.5 V battery to confirm that their terminals are correctly marked? It's not that uncommon for inexpensive drivers to be mis-marked since a QA station may only be testing one out of a hundred or more.
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I've checked the connections and they are wired correctly. I even tried wiring one of the speakers in reverse polarity to the amp in purpose, and it would just spit out loud buzzing noise, so I shut it off immediately.
I will try checking the terminals with a battery.
With the other amp im using right now, the speakers are playing just fine, with the same wiring. I only unplugged from one amp and connected the speakers to the other.
Conclusion:
I have two bass/mid-range drivers, but only of them produces bass. It's not even producing any mid-bass thump. As if the bass-driver was a tweeter.
I now bought a proper adapter for the 3-pin to aux, but the problem is still there.
I tried switching the input cable around on the amp, which makes the left speaker the right channel, and the right speaker the left channel. The issue is then still there, only now, it's the other driver that is not producing bass. So the speakers are fine. Both speakers play equally when tested on another amp.
Would that result in the issue being the amp itself? I tried with different power adapters as well, one is 12V 1A with DC-DC converter to 32V. The other one is 24V 2.5A. Maybe they are too weak for the amp to be able to produce enough power to drive both speakers to equal bass? Or is that completely irrelevant?
If it is the amp, is there any modifications I can do to turn both channels into mono, if that would somehow solve the issue?
I have two bass/mid-range drivers, but only of them produces bass. It's not even producing any mid-bass thump. As if the bass-driver was a tweeter.
I now bought a proper adapter for the 3-pin to aux, but the problem is still there.
I tried switching the input cable around on the amp, which makes the left speaker the right channel, and the right speaker the left channel. The issue is then still there, only now, it's the other driver that is not producing bass. So the speakers are fine. Both speakers play equally when tested on another amp.
Would that result in the issue being the amp itself? I tried with different power adapters as well, one is 12V 1A with DC-DC converter to 32V. The other one is 24V 2.5A. Maybe they are too weak for the amp to be able to produce enough power to drive both speakers to equal bass? Or is that completely irrelevant?
If it is the amp, is there any modifications I can do to turn both channels into mono, if that would somehow solve the issue?
When coupled, only one of the bass drivers has movement. Although when I put my hand against the cone, i can feel small vibrations.
Although It's possible that it's not playing at all and the small vibrations I feel is from the enclosure which might be vibrating the cone a small amount. I can feel a lot of vibrations and movement on the speaker that is operating correctly.
When plugging the aux cable to my PC, with both speakers connected and playing, I turned down the volume on the channel with the correctly operating speaker and left the "faulty" speaker's channel on 100%. I then only hear high frequency sounds (maybe upper mid-high) frequency. But there is no bass what so ever.
When reversing this and leaving the channel at 100% volume on the speaker that is operating correctly, and turning down the channel volume all the way down to zero on the speaker that is not, I hear all frequencies, including all the bass.
It's possible that I only hear the tweeter when only playing the "faulty" speaker. The tweeter goes down to 4000 Hz so i'm not sure if the speaker is even playing at all.
That "vibration test" may be confirming that the second driver is not receiving any significant electrical signal.
That prompts me to ask:
Is connecting the second interconnect somehow shorting the input signal so that only one amplifier is receiving a valid signal?
Can you measure the input and output signals of the amplifiers for all the different interconnection options?
That prompts me to ask:
Is connecting the second interconnect somehow shorting the input signal so that only one amplifier is receiving a valid signal?
Can you measure the input and output signals of the amplifiers for all the different interconnection options?
Unfortunately I don't have any measuring equipment, but if i come across any, i'll make sure to do that.
Now the amp only costs $15 so it doesn't matter all that much really. But I really liked the sound quality of it and the power it can produce, so I would like to order a new one. But I want to rule out everything else, so i'm certain that it's the amp that is faulty before I order a new one. Since they ship them from china and it takes a decade until it arrives.
Well, not from my part at least. If you are talking about the amplifier itself, as in I should follow/measure the connections to look for any errors that could possibly be shorting the connections?
Do you have the acoustic specs? Or just the blurb on the website? (It does not even cite a typical resonant frequency. It does say "midrange", not mid-bass.)
You won't go wrong with this rule of thumb. Multiply the advertised diameter by 1.1. Cube that. Build a sealed box that size for each speaker.
6.5" * 1.1 = 7.15
7.15^3 = 365 cubic inches (0.21 cubic feet, 6 liters)
You can go 20% smaller or up to twice as large-- usually other factors govern what you want to do.
With small speakers, ported means a much larger box and some real math, including figuring cone-slap below Fb. A six-inch worked LOUD will usually be better as a sealed box.
"300 Watts" for 20 bucks is preposterous-- do not believe the "specs" on low-price speakers.
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