2-way project

[Dan2]

Hi guys.

I aquired a pair of AIWA speakers, i found the specs on another forum while searching the model number.




Speaker System 3 Way, Built-In Subwoofer (magnetic shielded type)

Speaker Units - Subwoofer : 160mm cone type : Full Range : 100mm cone type : Super Tweeter : 20mm ceramic type

Impedance 6 ohms/8ohms

Sensitivity 87 dB/W/m

...and from the box.....

2 x 130W (Subwoofer) 2 x 40W (Main)
2 x 75W 2 x 75W (RMS)
2 x 60W 2 x 20W (DIN THD 1%)






this sounds exactly like what i have- but i don't have the HI-FI that came with it so i want to build up a semi-decent 4ch amp with active variable crossover.

i also have an old sony amp, model TA-V70. this thing gives out absolutely no bass, but i am hoping if i replace the caps it will be good as new.

inside the amp are 2 sanyo STK4034X chips, which are rated at 45W each which i want to use for the subs, and then build 2 more chip amps for the mids.

as for the crossover, i already tried a fixed frequency XO, crossed at 300hz but that sounds horrible on these speakers - crossed way too high. unfortunatly i don't know what the XO frequency should be, but i would guess around 150hz, which is why i would like to be able to vary the XO freq.

i am also a bit worried that these speakers only sounded good because the hi-fi had lots of equalisation (lots of bass and treble boost). i might need to build some kind of extra boost into the XO.

the amp has multiple source inputs and an equaliser which i would like to use if i can locate where the pre-amp output is. the question is: in order to get this amp sounding good again do i have to replace the caps in the preamp too?? 'cos there are quite a few.


any advice/ suggestions before i attempt to mod this amp??

below is a pic of the speakers with the hi-fi

[Dan2]

......also the datasheet for the chips.


oh yes, and how much power should the mid amp give out? i just want it to be able to keep up with the subs.

i know this is a lot of guesswork 'cos i don't hav much info. sorry

[PeteMcK]

youv'e actually got 2 projects here: 1, the amp - I'd recap all the circuitry which is in the signal path you're going to use.
A matching mid-high amp should ideally have the same power capability for maximum headroom, although you could get away with less power or a lighter power supply.

2, the speakers. It unlikely that you're going to get great sound from these, but you won't know until you test them fully for a TS parameters, and run a frequency response test and an impedance curve.

ARTA http://www.fesb.hr/~mateljan/arta/download.htm
ARTA Jig - http://zobsky.blogspot.com/2008/01/s...t-jig-for.html

[Dan2]

thanks Pete, that ARTA program looks like a really usefull program to have.

when i test the drivers, do i test them in the enclosure or must i take them out of the box? the subwoofer has a port right in front of the speaker, so i'm sure that will change the characteristics of the speaker.

as for the speakers , i have heard them before with the hifi. although the sound quality is not perfect, i liked the sound of them, plus they are relatively compact. they will mostly be used for music (mp3) and gaming.

man oh man you got to love these old amp's, the PCB's are so clearly marked out- i think this is going to be easy!
each power amp chip has its own input connector from the pre-amp.

[901Fixer]

This is pretty ingenious of AIWA, a "FAST" system with a super tweeter. The SubWoofer should be crossed much lower than 300hz say around 100hz or lower but since they are close to the fullrange driver there should be no combing or phase issues. Part of the reason they sound so good is no crossover in the critical frequency which the fullrange driver allows to happen.

A buddy of mine had an AIWA Karoke system and I was amazed at how full and clean it sounded for a WalMart plug and play fully contained boom box for the bookshelf at a very affordable price.

[PeteMcK]

It's usual to test drivers on a large baffle.
However, if you like the sound of the speakers as they are, why not just put some extra padding inside the box to reduce resonances (not too much), and upgrade the crossover capacitors?

[Dan2]

.......well there is no crossover at the moment. the speakers are bi-wired, which is why i want to convert this old sony amp to a 4 channel and build an active crossover.


901Fixer, i would also say the subs need to be crossed over at 100 hz. i think i might just build an XO at that freq and see what it does.

i hav a major problem with the amp tho - there is no way i can unplug the cables from the PCB's, they just don't come off! but im gonna hav to make a plan there.

i am thinking of getting a chip amp of about 20W output for the mids, and using the amp's transformer. i don't need this system to tear the house down - and will prob use it to about half of its output at the most