again in dylema...but to cut down the cost of the woofer amp.TDA 7294 or LM3886?

rhythmdiy · 30th October 2007, 06:56 PM

Ive been planning to drive Vifa PL26W 8ohm woofers with chip amplifiers. But I wan to cutdown the complexity of the amp but I still need good quality sound for recording studio. Ive been checking over the net and I found that NORH subwoofer uses TDA 7294 chip single to drive the subwoofer. The PL26W is just the next size of the driver used in NORH sub..
http://www.madisound.com/catalog/pro...oducts_id=1142

the one that I want to use is

http://www.madisound.com/catalog/pro...oducts_id=1144

just the next size of the same category woofer but with almost same specs...

so my question is TDA and LM3886 chip amps has got similar of 70 watts RMS into 8 ohms so if the TDA chip can drive the woofer efficiently then do two of the LM3886 chips can be sufficient enough to drive the 10 inch woofer? I mean can it go till 125 watts? or shall I stick on to the TDA?

Ive been fiddling with the thought and I was thinking of going with the BPA 200 to drive the chip but it will become way too complicated in almost every aspect.. like trafo, heatsink, DRV circuits etc etc etc...

so friends tell me what makes it to drive the woofer better...?

2 LM3886 chips in parallel?
2 LM3886 chips in bridged?( one chip for positive cycle and vicevarsa)

4 chips in parallel?
4 chips in BPA200 mode?

1 TDA 7294 chip?
2 TDA 7294 chips in parallel?
2 TDA 7294 chips in bridged?

please friends help me....

But I want ultimate quality since im using premium woofers...

thanks,
Ken

Cro maniac · 30th October 2007, 08:33 PM

I think that even one LM3886 or TDA7294 would be ok for powering your Vifa driver due to it's very limited Xmax. You don't really need 125 W just because your driver can take it thermally. Simulate the driver in the box you are planning to use using some program like WinIsd, apply some power and watch for excursion. My last sub had inexpensive 12" Westra driver in it and I powered it with only one TDA 7293 (newer version of TDA7294), and it very easily bottomed out.

I made a lot of amps based on LM3886 and TDA7293 and found that it is much easier to make the PCB's for LM's because of their much simpler pinout, so for simplicity you could go that way.

If you eventually decide that one chip doesn't have enough power for your needs, bridging would be the way to go because Vifa is 8ohm driver.

At the moment I use 2 LM's bridged to power 12" Peerless driver with 3x displacement of yours and 90% of time I find them enough strong for the job.

LM's and TDA's sound much different, so it is also a matter of music taste when choosing a chip.

Hope this helps !

udderslate · 30th October 2007, 09:22 PM

Ken

before you get too deep into amp choices , if you haven't already,
toss the speaker params into WinISD Pro ( free BTW ) .
Look at cone excursion for your desired power .
I see the spec on this woofer is 4mm Xmax .

I just put together a dissapointing 8in Sub . ( 6mm xmax )
I didn't note xmax limited power of 25W at 30HZ
this speaker was "rated" at 80W ...arrrgh .

Wayne

rhythmdiy · 31st October 2007, 02:57 PM

yeah I ve checked with the WINISD alpha program and its true it shows max excursion at 50watts even though its rated at 125RMS...

Quote:

At the moment I use 2 LM's bridged to power 12" Peerless driver with 3x displacement of yours and 90% of time I find them enough strong for the job

wow are the chips getting hot? did u use any DRV134 or SSM chips to convert unbalanced to balanced?

how long you have been using the LM3886 chips to drive those massive babies?

are you getting chest pounding bass with these two LM chips in Bridged mode?

whats ur power supply trafo and caps? did u use toroidal?

thanks,
Ken

rhythmdiy · 31st October 2007, 03:09 PM

Ive been searching all over the net to find the X max for the PL26W driver but I couldnt find it ... even on the tymphany website... how did u get this info?

Cro maniac · 31st October 2007, 03:52 PM

Quote:

yeah I ve checked with the WINISD alpha program and its true it shows max excursion at 50watts even though its rated at 125RMS...

So, you got a very simple situation, go with only one chip and enjoy.
If you provide adequate heatsinking you can go few volts above what's stated in the datasheet to extract few watts more, especially with TDA.

Quote:

Ive been searching all over the net to find the X max for the PL26W driver but I couldnt find it ... even on the tymphany website... how did u get this info?

It is listed on a link you gave in first post.

Quote:

wow are the chips getting hot? did u use any DRV134 or SSM chips to convert unbalanced to balanced?
how long you have been using the LM3886 chips to drive those massive babies?

No, I use just plain TL072 to get inverted signal.
Something like this: http://sound.westhost.com/projects-9.htm
Chips are never getting too hot, but when I push the limit too far, the SPIKE protection kicks in on music peaks.
I've been using this configuration for 8 months now, I plan to build something stronger soon, but I'm too lazy at the moment.

Quote:

are you getting chest pounding bass with these two LM chips in Bridged mode?

It can go pretty loud, but I wouldn't call the sound chest pounding because my sub is crossed lower than those chess pounding frequencies, it is more like "furniture moving" bass (deep).

Quote:

whats ur power supply trafo and caps? did u use toroidal?

Those amps are configured as monoblocks so each chip has its own 200VA trafo and stabilised supply. Supply maybe is an overkill, but one thing that I really hate is when supply voltage drops under load.

More info on the amps:
6 monoblocks finished

rhythmdiy · 31st October 2007, 05:54 PM

hello cromaniac can u please mention the 12 inch peerless subwoofer model no... is it XLS or XXLS etc.. which one specifically...?

but anyway thanks alot for the info...

but im still struggling regarding bass tilt circuit can u help me how the cricuit will be? pls....

thanks,
Ken

Cro maniac · 31st October 2007, 10:29 PM

It is 12" XXLS model 830844 with 12" passive radiator model 830844.

You can see the pic of the sub in this thread:
My XXLS Subwoofer building thread...

I don't understand the term "bass tilt". Is that some kind of shelving filter ?

rhythmdiy · 1st November 2007, 05:59 PM

Quote:

I don't understand the term "bass tilt". Is that some kind of shelving filter ?

I dont know... I believe it is but i didnt find the exact match for the bass tilt circuit...

how about the gain control circuit... like i want to control input gain using a opamp or so... in -1db to -6db.... I think you are an expert i got few links from other forum members but i need a clear circuit diagram to control it..if you know please guide me...

thanks,
Ken

Cro maniac · 1st November 2007, 06:19 PM

rhythmdiy, if you only want to adjust the gain to match the sensitivity of the midrange driver, try this:

http://linkwitzlab.com/filters.htm

Look at the paragraph 10 - Variable gain. That's what I am using in preamp to adjust sensitivity between midbass and tweeter.
If you decide to use circuit A, note that it inverts the signal, so take that into account when designing your bass preamp/crossover circuit.

30th October 2007, 06:56 PM	#1
rhythmdiy diyAudio Member Join Date: Dec 2006	again in dylema...but to cut down the cost of the woofer amp.TDA 7294 or LM3886? Ive been planning to drive Vifa PL26W 8ohm woofers with chip amplifiers. But I wan to cutdown the complexity of the amp but I still need good quality sound for recording studio. Ive been checking over the net and I found that NORH subwoofer uses TDA 7294 chip single to drive the subwoofer. The PL26W is just the next size of the driver used in NORH sub.. http://www.madisound.com/catalog/pro...oducts_id=1142 the one that I want to use is http://www.madisound.com/catalog/pro...oducts_id=1144 just the next size of the same category woofer but with almost same specs... so my question is TDA and LM3886 chip amps has got similar of 70 watts RMS into 8 ohms so if the TDA chip can drive the woofer efficiently then do two of the LM3886 chips can be sufficient enough to drive the 10 inch woofer? I mean can it go till 125 watts? or shall I stick on to the TDA? Ive been fiddling with the thought and I was thinking of going with the BPA 200 to drive the chip but it will become way too complicated in almost every aspect.. like trafo, heatsink, DRV circuits etc etc etc... so friends tell me what makes it to drive the woofer better...? 2 LM3886 chips in parallel? 2 LM3886 chips in bridged?( one chip for positive cycle and vicevarsa) 4 chips in parallel? 4 chips in BPA200 mode? 1 TDA 7294 chip? 2 TDA 7294 chips in parallel? 2 TDA 7294 chips in bridged? please friends help me.... But I want ultimate quality since im using premium woofers... thanks, Ken

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30th October 2007, 08:33 PM	#2
Cro maniac diyAudio Member Join Date: Feb 2004 Location: Zagreb, Croatia Blog Entries: 2	I think that even one LM3886 or TDA7294 would be ok for powering your Vifa driver due to it's very limited Xmax. You don't really need 125 W just because your driver can take it thermally. Simulate the driver in the box you are planning to use using some program like WinIsd, apply some power and watch for excursion. My last sub had inexpensive 12" Westra driver in it and I powered it with only one TDA 7293 (newer version of TDA7294), and it very easily bottomed out. I made a lot of amps based on LM3886 and TDA7293 and found that it is much easier to make the PCB's for LM's because of their much simpler pinout, so for simplicity you could go that way. If you eventually decide that one chip doesn't have enough power for your needs, bridging would be the way to go because Vifa is 8ohm driver. At the moment I use 2 LM's bridged to power 12" Peerless driver with 3x displacement of yours and 90% of time I find them enough strong for the job. LM's and TDA's sound much different, so it is also a matter of music taste when choosing a chip. Hope this helps !

30th October 2007, 09:22 PM	#3
udderslate diyAudio Member Join Date: Oct 2007	Ken before you get too deep into amp choices , if you haven't already, toss the speaker params into WinISD Pro ( free BTW ) . Look at cone excursion for your desired power . I see the spec on this woofer is 4mm Xmax . I just put together a dissapointing 8in Sub . ( 6mm xmax ) I didn't note xmax limited power of 25W at 30HZ this speaker was "rated" at 80W ...arrrgh . Wayne

31st October 2007, 03:09 PM	#5
rhythmdiy diyAudio Member Join Date: Dec 2006	Ive been searching all over the net to find the X max for the PL26W driver but I couldnt find it ... even on the tymphany website... how did u get this info?

31st October 2007, 05:54 PM	#7
rhythmdiy diyAudio Member Join Date: Dec 2006	hello cromaniac can u please mention the 12 inch peerless subwoofer model no... is it XLS or XXLS etc.. which one specifically...? but anyway thanks alot for the info... but im still struggling regarding bass tilt circuit can u help me how the cricuit will be? pls.... thanks, Ken

31st October 2007, 10:29 PM	#8
Cro maniac diyAudio Member Join Date: Feb 2004 Location: Zagreb, Croatia Blog Entries: 2	It is 12" XXLS model 830844 with 12" passive radiator model 830844. You can see the pic of the sub in this thread: My XXLS Subwoofer building thread... I don't understand the term "bass tilt". Is that some kind of shelving filter ?

1st November 2007, 06:19 PM	#10
Cro maniac diyAudio Member Join Date: Feb 2004 Location: Zagreb, Croatia Blog Entries: 2	rhythmdiy, if you only want to adjust the gain to match the sensitivity of the midrange driver, try this: http://linkwitzlab.com/filters.htm Look at the paragraph 10 - Variable gain. That's what I am using in preamp to adjust sensitivity between midbass and tweeter. If you decide to use circuit A, note that it inverts the signal, so take that into account when designing your bass preamp/crossover circuit.

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