stereo to mono problem

[SentinelAeon]

Hello, i am trying to convert stereo into mono on my bluetooth amplifier/receiver, since i am using a woofer + tweeter setup. I included a picture of how i solder the pins together. Right now the pot is up to a maximum, which means the pins are effectively shorted together. I know ur supposed to use a resistor but i am looking for a max SPL, even if the amplifier dies after a few months. The amplifier chip itself is TPA3116D2. The amplifier board is ZK-502C hifi.

Problem 1: Even when the pins are shorted together, i get on average about 4-5dB less SPL than i would otherwise and i dont understand why since i am not using any resistors and pot doesnt offer any resistance.

Problem 2: When pins are shorted together, the speaker amplifier will shut down and restart if the pot is over 80% volume. This happens even if the speakers are not connected ! I am really wondering why.

Question: Is there any way to get around this since i need every single last dB i can get, so i cant lose even 1dB, let alone 3dB.

 

[audioguru]

A speaker is not a 6 ohms resistor, it has inductance that causes its impedance to rise when the frequency rises. Your little woofers might resonate at 150Hz in their enclosure then they "boom" at that mid-bass frequency and they cut lower frequencies.
But above the resonant frequency the impedance is 6 ohms maybe at 500Hz and at your very high 5kHz crossover frequency the speaker produces cone breakup that is what a crossover should eliminate and the impedance is maybe 20 ohms. Your "crossover wizard" uses parts for a 6 ohms resistor, not for a 6 ohms woofer that is maybe 20 ohms at the crossover frequency. The crossover circuit needs extra parts to work properly.

 

[pako202]

What would you advise me to do? What crossover do I install?

 

[audioguru]

Most people use Name Brand speaker drivers that have a detailed datasheet like most speaker drivers at Parts Express.com. Then the cone-breakup frequencies are shown on a graph and a tweeter that works well at woofer cone breakup frequencies and above can be selected. Then a "speaker zobel network" (look it up) is added to the woofer to make its impedance less at the crossover frequency.

Here is a 5" woofer graph from Parts Express:

 

[Nigel Goodwin]

I remind you that a portable speaker

https://www.amazon.com/-/es/Marshall-Altavoz-Bluetooth-inal%C3%A1mbrico-Woburn/dp/B07HPM264C?th=1

I've no idea of the relevance of that?.

NIGEL el sony que tengo tiene esta referencia 1-505-235-13
I have measured the sony and they are 6ohm

If you measured it's resistance (with a multimeter) then they are 8 ohm speakers, 8 ohm (impedance) speakers have roughly 6 ohms resistance.

 

[audioguru]

This copy of a speaker system uses woofers that are only 5" and is mono because it is portable.
The original speaker system has a very old appearance and design that are very old.

I have seen modern very small portable speaker systems that produce wideband loud sounds.

 

[pako202]

They have an old design because Marshall makes them that way.
but from your comments I see that you have never heard it..... I would like you to listen to them or see the reviews. those who listen to them are hallucinated by the sound quality it has

 

[pako202]

Marshall Woburn Bluetooth Speaker Review - What Monkey Says

I have been looking at speakers a lot over the last couple of years. I’ve been making do with some small Polk satelites and a large subwoofer hooked up to a modern Denon receiver for several years now. But I finally got too frustrated with all the wires trailing behind desks and the sheer bulk […]

www.whatmonkeysays.com

 

[pako202]

here its interior

 

[pako202]

the problem is that I can't find the characteristics of the sony wofer to know the frequency of rupture....
1-505-235-13 come from. Sony SS-H771 (15cm / 6ohmi / ~50W / 40HZ-14KHZ)

 

[SentinelAeon]

I am happy that my topic is helping another person and for once, oh god i am happy i am not the one asking the questions. Reading through the posts it's all so complicated to me and i have so much to learn. I have been avoiding 2nd order for the past 2 years for the sole reason that i am so extremely cheap: i have 10s of coils at home from power suplies and other electronic components and i just cant order an audio coil for crossover knowing i have 10s of coils at home that i will throw away. At the same time, i have no idea if those coils would even be usable for crossover nor how to check if they are.

I am in no position to give advices. All i can say is that when i started, i wanted to use speaker cones from old speakers that people would just throw away. Most people i know would be ok with that, they simply dont care, some of them listen to music using mobile phone speaker ... but as soon as you want to make a decent speaker, you have to find a speaker that has a datasheet so you can calculate port and enclosure size.

pako202: Just out of curiosity, the image you posted in the previous post ... slika0009.jpg. Is that your native language ?

 

[pako202]

no, i am spanis
Would it be better to buy this kit and make the enclosure for it?

 

[audioguru]

The videos say that the Marshall Woburn speaker is LOUD and distorted.
Guitar amplifiers produce lots of distortion like the old vacuum tube amplifiers produced.
The speaker is not portable and has no battery.
The enclosure is a ported bass-reflex that matches the detailed specs of the woofers.

How will you design the enclosure size and ports when you do not have detailed specs of your Sony woofers?
Do you have detailed specs for your tweeters to select a suitable crossover frequency> 5kHz is too high since the woofers will have "screaming" cone-breakup at 3kHz to 6kHz.
The Sony speaker has bass, midrange and tweeter speakers so the woofer does not play midrange properly or the tweeter does not play midrange properly.
The car speaker kit has 4" woofers that play no bass frequencies.

I cannot find printed detailed specs for the speaker. 20Hz to 20kHz means nothing without saying "plus or minus how many decibels". 'How much distortion at what power output"? "Noise level at no input"?

 

[rjenkinsgb]

Guitar amplifiers produce lots of distortion like the old vacuum tube amplifiers produced.

Sorry, but you know nothing about guitar amps and just keep endlessly parroting the same nonsense and false claims.

eg. These are the specs of one of my guitar amps, an Ashdown rated 250W RMS out (400W in)

INPUTS High Input Impedance 3.9M Ohms Input range 150mV to 20V p-p
Low Input Impedance 10K Ohms Input range 300mV to 40V p-p
Effects Return Impedance 22K Ohms Input level 0dBu nominal
OUTPUTS Tuner Output Impedance 10K Ohms Level 0dBu nominal
Effects Send Impedance 22K Ohms Level 0dBu nominal
D.I. Output 600 Ohms balanced Level -20dBu nominal
Speaker Outputs Minimum Impedance 4 Ohms
Frequency Response -3dB at 22Hz and 25kHz
EQUALISATION Bass +/- 15dB @ 100Hz Lo Mid +/- 15dB @ 340Hz Middle +/- 15dB @ 660Hz Hi Mid +/- 15dB @ 1.6kHz Treble +/- 15dB @ 7kHz Shelving Deep + 8dB @ 50Hz Bright + 10dB @ 10kHz
Signal to Noise Better than 80dB (EQ Flat)
Distortion Less than 0.5% THD

Note these lines:
Frequency Response -3dB at 22Hz and 25kHz
Signal to Noise Better than 80dB (EQ Flat)
Distortion Less than 0.5% THD

How is that "Lots of distortion"?

Many guitar amps do allow you to select between "clean" and "overdrive" modes - but the overdrive distortion is the users choice, not fundamental to the amp!

Cheap "toy" grade amps may be bad, but that's the same with anything and not a fundamental of guitar amps in general.

 

[audioguru]

61 years ago I built my first audio amplifier as a kit. It produced audible 0.5% distortion that was measured by the Macintosh Amplifier Clinic after its vacuum tubes were broken-in for a few months. I replaced the tubes and had distortion measured again and it was clean, measuring less than 0.1% distortion. A few months later the tubes produced 0.5% distortion again until they were replaced again.
Likewise, some bands replace their tubes before each gig.

Your old amplifier is typical of an old amplifier. The sales sheet for a VERY expensive Ashdown AGM-5C amplified speaker has no audio specs but says it produces 5W.

The Marshall Woburn little amplified speaker has no audio specs.

 

[pako202]

I have designed the drawer following the advice of a forum, with a kid with the same.

Amplificatoare si boxe home-made - Pagina 58

Din cate stiu eu Dj_Dog comercializa intr-o perioada astfel de difuzoare, deci este in masura sa recomande incinte pentru acest difuzor (si aici nu vorbesc doar de grafice ci

www.mygarage.ro

 

[pako202]

I think I'm going to put this active crossover and put 1 amplifier for wofer and another for tweeter

https://es.aliexpress.com/item/1005003340422996.html?spm=a2g0o.detail.1000014.11.765450bbSfk6nt&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.40050.281175.0&scm_id=1007.40050.281175.0&scm-url=1007.40050.281175.0&pvid=15d6a2f3-7ffc-4237-82c4-b9a29643286d&_t=gps-id:pcDetailBottomMoreOtherSeller,scm-url:1007.40050.281175.0,pvid:15d6a2f3-7ffc-4237-82c4-b9a29643286d,tpp_buckets:668%232846%238111%231996&pdp_ext_f=%7B%22sku_id%22%3A%2212000025302211656%22%2C%22sceneId%22%3A%2230050%22%7D&pdp_npi=2%40dis%21EUR%2118.96%2113.27%21%21%21%21%21%40211b442216729786170738706e638b%2112000025302211656%21rec

https://es.aliexpress.com/item/1005003734059207.html?spm=a2g0o.detail.1000014.4.5f333aecCiBWI8&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.40050.281175.0&scm_id=1007.40050.281175.0&scm-url=1007.40050.281175.0&pvid=c0e6f40d-af20-4b4d-89c2-9592ceb45640&_t=gps-id:pcDetailBottomMoreOtherSeller,scm-url:1007.40050.281175.0,pvid:c0e6f40d-af20-4b4d-89c2-9592ceb45640,tpp_buckets:668%232846%238111%231996&pdp_ext_f=%7B%22sku_id%22%3A%2212000026977343338%22%2C%22sceneId%22%3A%2230050%22%7D&pdp_npi=2%40dis%21EUR%2110.8%218.64%21%21%21%21%21%40211b423c16729662441118220e8721%2112000026977343338%21rec

https://es.aliexpress.com/item/1005003734051085.html?pdp_npi=2%40dis%21EUR%21%E2%82%AC%2012%2C83%2110%2C26%20%E2%82%AC%21%21%21%21%21%40211b5a9616729657860125837ebb1f%2112000026977306506%21btf&_t=pvid%3A1e240a36-466c-413a-9885-bd5e24629b24&afTraceInfo=1005003734051085__pc__pcBridgePPC__xxxxxx__1672965786&spm=a2g0o.ppclist.product.mainProduct&gatewayAdapt=glo2esp

 

[audioguru]

1) The enclosure and its port size must be calculated with the specs of the woofer, not by random.
2) The 3-way crossover needs an additional midrange speaker.
3) The 2-way crossover has a crossover frequency of 330Hz which is much too low for any tweeter.

 

[rjenkinsgb]

The sales sheet for a VERY expensive Ashdown AGM-5C amplified speaker has no audio specs but says it produces 5W.

That is an overpriced toy gimmick for valve / tube amp nuts with far more money than sense!
It's a joke, in fact - a "Valve amp for purists" - with digital reverb built in... Audiophool bait.

And, It has no relevance at all to the big solid state Ashdown I have. Not an "old" amp at all, by the way, it's rather newer than my Carlsbro GLX100 solid state, which also has excellent quality in "clean" mode (but I cannot find the formal specs for that at present).

If my Ashdown is 0.5% worst case at full 250W output [which I'd never use] the distortion will presumably be much lower at more reasonable volumes, quite likely 0.1% or less?

You are still trying to criticize equipment you have no experience with, by picking out oddities rather than serious equipment.

 

[audioguru]

Pako is talking about making a copy of a Marshall Woburn amplified guitar speaker that has fairly low output power and no audio specs. He said he wants ot for playing all kinds of music at home. I do not know why he said for it to be portable.

Most people use a hifi amplifier driving hifi speakers at home or portable, not one amplified guitar speaker system.

 

[pako202]

It is not a guitar, it is a 90w rms auto amplified speaker, 50w for wofer and 20w for each tweeter and a frequency cut at 2800Hz