[gringo117]

Hi guys,

A regular subwoofer amp has RCA (L+R) inputs and also single LFE. It might have High Level inputs, but they are also L+R (so generally speaking same as RCA). Here I am not talking about the LFE which is single input. How does the amp processes the Left and Right input signals into one output (amplified) signal? Does the output contain the stereo (both signals)?
The reason why I am asking is because of dipol/ripol subwoofers, that have obviously 2 woofers in one enclosure. In Ripol they are opposite to each other and to reap the benefits of cancellation of the back and side waves the signals from both of them have to be exactly the same.
Therefore I doubt that one (very powerful) regular amp can be used, because left channel would go to one subwoofer and right channel would go to the other subwoofer. And those are different signals and would not cancel each other out.
So splitting the L+R signals from the preamp to two subwoofer amps which each feed one subwoofer with the same amplified signal.
Yes, there is also the possibility to use one single subwoofer amp and connect the subwoofer drivers in parallel. But, I am about to use 4 ohm drivers and using them in parallel would require a subwoofer amp that can handle 2 ohm loads. And I know of no such amplifier.
Here are the 2 subwoofer amps that I found that might suit me: Dayton Audio SPA500 / SPA1000.
Only what bothers me is that they do not have a stepped phase correction, only 0 and 180.
Here are regular amps that might be used for each drivers separately: crown XLC2800 / Crown XLS 2502 , Dayton Audio SA1000. The dayton has also stepped phase regulation. If I knew how to connect the regular amps to the drivers, I would have more options.


Any ideas?

Thanks in advance for reading all the way till the end.


PS: I plan to build a ripol sub with 2x Scan-Speak 32W/4878T00 drivers.

[dwmaggie]

Gringo, have you considered wiring them in series?  The amp will then see an 8-ohm load.

[gringo117]

Yes, I have considered it. I just forgot to mention that also in my initial post.
When wiring them in series, yes the amp sees 8-ohm load, however its power rating to one subwoofer drives goes to 1/4. Example: Amp is 500W in 8ohms and 1000W in 4 ohms. So when used with one 4 ohm driver, it can handle 1000W. When a 8 ohm driver used then 500W is provided by the amp. And when the two drivers are used in series, you have to divide the 500W to each driver. With that each driver would receive 250W. Instead of 1000W at 4 ohms, you would get 250W in 8 ohm to each driver. And for a subwoofer that is not a lot of power. Or at least that is how I understand this. Please correct me if I am wrong.

I have just found out that the Dayton Audio SA1000 is summing up the L+R input channels into 2 sets of mono outputs. I have just wrote them to confirm what is the power rating of each mono channel output as from the manual it is not clear. That has stepped phase correction. It can handle summ of 4 ohm load, so that would be also used only for single 4 ohm driver.
When I get the answer I will post it here.

[Jazzman53]

I'm driving two Ripole subs with a single stereo amp.   Each sub has two 12" Peerless SLS woofers wired in parallel and same phase (push/push, 4 Ohm load)-- sounds fabulous. 
 

[dwmaggie]

From what I can recall, using 2 4-ohm speakers in series for an 8-ohm load does not divide the power.  The combined 8-ohm load will still be 500 watts for each speaker.  I used to trick the old car stereo amps (mid 1970s) by dropping the impedance down to 2 ohms and theoretically doubling the power, ie.. 2 4-ohm speakers in parallel to a 2-ohm load.  You should be fine with the combined 8-ohm load, with no loss in volume.

[gringo117]

I'm driving two Ripole subs with a single stereo amp.   Each sub has two 12" Peerless SLS woofers wired in parallel and same phase (push/push, 4 Ohm load)-- sounds fabulous.

Thanks for the reply. I already saw your posts and the web site with the info about the build of your system. Very nice. Building planar speakers is technically to much for me, but ripol I will try. 
Your subwoofer ripol connection with the amp makes sense for the Peerless SLS 12". I checked the specs of those drives: they are 8 ohm and something around 100W. So when you have an amp (does not matter now whether stereo or subwoofer mono with 2 outputs), if it can handle 4 ohm load at least of 200W per channel, then yes I believe you that it sounds great.
And why it does not matter whether the amp is mono or stereo? Well let us say that it is stereo. The left channel is fed to one ripol sub to two drivers with the same left signal. The other channel feeds the other sub (both drivers) with the same right signal.

I was not considering building 2 ripol subwoofers, but because of the advantage of amplifier possibilities that  open up, I might.

If I build just one sub then:
The sub will be built with 2x 8ohm drivers. It will be much easier to drive them with the amp.
Driver    : Peerless XXLS-P830845
Amplifier: Dayton Audio SA1000  . Here they already answered me and in one youtube review of that unit it was also mentioned. The two outputs are actually in parallel, so the signal is split in two within the amp. So 1x950W into 4ohms when used only with 1 driver, any of the outputs can be used. But I will drive 2x8hms in parallel is 4 ohms: so each driver will have 475W at disposal. No clipping from amp is expected there. 

If 2 subs just like you Jazzman53, then because the amplifier chosen the drivers can be 4 ohms:
Drivers: Scan-Speak 32W/4878T00
Amplifier: Crown XLS 2502. It can handle 1200W at 2ohms, 775W at 4 ohms per channel !!! What a beast.

[JohnR]

You don't need that much power, according to the specs the 32W reaches Xmax at 30 Hz with 200W (in free air).

[gringo117]

You don't need that much power, according to the specs the 32W reaches Xmax at 30 Hz with 200W (in free air).

That is true. So a rating of 400W in 2 ohms per channel should be sufficient for the 32W.
I could get the Crown XLS 1502, which is also still plenty powerful (775W in 2 ohms) and somewhat cheaper. The XLS 1002 is where I live almost the same price as the 1502.

[gringo117]

I'm driving two Ripole subs with a single stereo amp.   Each sub has two 12" Peerless SLS woofers wired in parallel and same phase (push/push, 4 Ohm load)-- sounds fabulous.

Cold you plese provide the blue print for the 12'x ripol subwoofer. The sizes etc.
Thank you in advance.