Stock subs, 50 watt rms or peak?

[J Wikoff]

I'm piecing together a shelf stereo for my garage. I have an amp that has a sub channel stable to 4 ohm at 68 watts. Don't know if that's peak or rms just yet. I thought I might use one or both of the old stock G8 subs which are 2 ohm and have 50 watts stamped on the back. I figure I'd have to use both, wired serial to play nice with the amp, but I'm not sure if the power will be sufficient. If they are 50 watts peak, it might be ok. Thoughts?

[STL_G8GT]

I'm piecing together a shelf stereo for my garage. I have an amp that has a sub channel stable to 4 ohm at 68 watts. Don't know if that's peak or rms just yet. I thought I might use one or both of the old stock G8 subs which are 2 ohm and have 50 watts stamped on the back. I figure I'd have to use both, wired serial to play nice with the amp, but I'm not sure if the power will be sufficient. If they are 50 watts peak, it might be ok. Thoughts?As long as you don't drive the amp into clipping you should be just fine, rms or peak, the numbers are close regardless. At that power level, no issues.

Building an acceptable enclosure will be the greater challenge... Id build the biggest box possible and adjust port length based on performance, 3" or 4" dia.

[J Wikoff]

I should be fine with just one 2 ohm sub, or with two in series?

[norm8332]

FYI: I left the stock subs in and installed an amp. I regularly (years) have put 150W peak (measured) into the stock subs without any kind of degradation or failure. They are pretty forgiving with music power. Like said above, just keep it below the level of when the amp or speakers clip.

[J Wikoff]

So 50 is likely their RMS. That helps to know. Thanks!

[STL_G8GT]

I should be fine with just one 2 ohm sub, or with two in series?You need to wire both subs in series to get 4ohm load.

Amp sub channel + to sub 1 +, then sub 1 - to sub 2 +, then sub 2 - to amp sub channel -.

[J Wikoff]

I tried last night, with one stock G8 sub and this amp. It sounds decent in lower volume situations, but when I turn it up the sub pops somewhat. I'll try wiring the second sub in series this evening and see how that goes.

https://www.parts-express.com/dayton-audio-dta-21bt-100w-class-d-21-amplifier-with-bluetooth-and-power-supply--300-3830

[norm8332]

Does that amp support two ohms? Yeah try them in series.. That amp is not going to be able to put out 2X50 Watts (100W) when it only comes with a 48W power supply Watts=Voltage times Amperage with DC.


The specs claim 4 ohm minimum. They are a bit sketchy if you ask me.

Specifications: • Speaker power output: 50 watts x 2 • Subwoofer power output: 100 watts • Impedance: 4-8 ohms • Amplifier input voltage: 24 VDC • Amplifier input amperage: 4A • Power supply voltage: 100-240 VAC, 50/60 Hz • Power supply amperage: 2A

Note that it says Amplifier input amperage 4A, but it only comes with a 2A power supply.

[J Wikoff]

The amp manual says 4 ohm min, but the data sheet for the chips in the amp say 2 ohm, and some reviews say they use 2 ohm just fine. So I thought I'd give it a try.

[norm8332]

Yeah, I think it's not an adequate power supply it's only 48W. How do they expect to get 50W X 2 and 100W sub woofer is beyond me. And you could only get 48W continuous on one channel if the amp was 100% efficient and it is not, more like 80% for class D. That means 38W total combined continuous output in real life. I think that amp is "creatively rated". It would probably work better with a 24V 5A power supply.

[J Wikoff]

It came with a 24 volt 4 amp output power supply.

Dayton is supposedly a decent name. That's why I bought it as opposed to some random Chinese named thing.

[J Wikoff]

I found a 5 amp supply on Parts Express.

[J Wikoff]

I wired in the second sub. The sound maybe got a little cleaner. But I think the speakers are the weak link. So my next decision is another box to hold the second sub, or spend a little more and get one better sub.

[norm8332]

Might as well get another sub if you think they are the issue.

Since I have the equipment I usually feed a sine wave to the amp with an oscilloscope and a dummy load to find out the amp clipping wattage for a given load. Then if clipping is heard prior to reaching that wattage, it's the speakers.

[J Wikoff]

I'm going to try this one.

https://www.rockfordfosgate.com/products/details/p3sd2-8/

[norm8332]

I just want to mention that the SPL of those speakers is a bit low at 82db. It requires exponentially more power to increase DB so you want to start with speakers rated of as high an SPL that is within your budget and requirements. I usually start being interested in speakers at an SPL of 85db and up. The higher the better. They go into the 90s with top specs. It makes a huge difference in the power needed for a given loudness output.

http://www.acoustics.salford.ac.uk/acoustics_info/decibels/

[J Wikoff]

I put the sub in today. It sounds much better. I'm still waiting on the boxes for the 6 1/2" speakers. I did try the 5a power supply. It didn't seem to make any difference, but since it's only running the sub, I don't know yet if it isn't able to keep up with just the 4a supply. I'll play around when I get the other speakers wired up.

[J Wikoff]

Got the boxes today and wired in the 2 ways. On heavier bass songs, it does run out of steam somewhat when loud. At levels I'll probably usually have it, it should keep up fine with the 5 amp adapter. Haven't tried the 4 amp yet, since I already had the 5 amp connected and heard the results.

[J Wikoff]

I was looking into a way to dial back the volume, and maybe the power, the 2 ways use. An L pad or attenuator looks like a good option, but I can't seem to find one in 4 ohm. It looks like I can got a stereo 8 ohm unit for each speaker and wire each on in parallel basically to make it 4 ohm. It would cost me like $40 though. I thought about just adding a 2 or 4 ohm resistor in series instead. But many say that muddies the sound.

[J Wikoff]

Here is what I put together.

http://i66.tinypic.com/mtp2y0.jpg

http://i63.tinypic.com/2hqqn0l.jpg

[STL_G8GT]

Are you saying the mids are too loud relative to the sub?

[J Wikoff]

Somewhat, yes. They also pull enough power when turned up that the sub seems to pull back.

[norm8332]

You might be able to add a NP capacitor to the mids so they aren't getting the full range if they are getting a bass signal. That would reduce their load in the bass area.

https://www.parts-express.com/cat/non-polarized-electrolytic-capacitors/1385

https://www.youtube.com/watch?v=70zCiaU_ABU

[J Wikoff]

The amp has a fixed built in 180 hz crossover or lowpass filter. I might try that anyway. Thanks!

[norm8332]

Here is a good SPL vs Watt calculator I use when looking at speakers for your future reference.

https://geoffthegreygeek.com/calculator-amp-speaker-spl/

[J Wikoff]

I ended up going the simple route and added a 4 ohm resistor to the + speaker input. It balanced out the sound noticeably and it sounds just fine.

[J Wikoff]

Update:

I ended up replacing the Dayton amp with a Nobsound amp that is rated for about 50% more power. It doesn't have quite the quality that the Dayton did (pops on power up, and a whine if I don't have the power plug positioned just right, had to warranty one because it lost the sub channel after a few days, and the new one lost the bluetooth function more recently but i can work around that), but if I don't fiddle with the knobs, it sounds really nice in my garage. I put an Echo Input on it and usually stream Amazon music.

Old Dayton amp:
https://smile.amazon.com/gp/product/B076CW8LJ5/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Newer Nobsound amp:
https://smile.amazon.com/gp/product/B07BFV7WFD/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1