BSR DR-SW15x2

[haromaster87]

Hey guys,


So I bought this BSR passive subwoofer today for my living room system. It's a sealed enclosure with a 15in driver. 20 Watts minimum, 150 watts max, and has a built in 120hz crossover. 4ohm resistance, but the guy had the resistor pack that came with it to make it 8ohm. From what the guy said it was from about '89 or so.

It was made when subwoofer outs weren't very common yet, so it has speaker inputs from the amp and then speaker outputs, to go to the main speakers and use the internal crossover.

My pre-amp has a sub out though which I was going to run to a power amp and run to the sub. I believe the preamp crossover is 80hz which is better than 120hz. This all seems simple enough except for one thing.

On the subwoofer, next to the speaker terminals, there is a warning label that says not to plug it in and use it unless you had the main speakers hooked up to it, as running just the inputs to the sub with no speakers on the outputs will apparently damage the sub.

Can anyone think of why? Perhaps a design in the crossover that needs the load of the speakers? This sub is probably the most well taken care of piece of equipment I've bought, so I don't wanna hook it up in a way that will damage it, but I don't want to run any of my main speakers through it.

What would likely be my best solution here? I'm guessing maybe remove and set aside the crossover and just make a new plate to screw in place of that with just a set of speaker terminals going to just the driver with no crossover since the preamp has the crossover. Any other ideas before I get to work on that?

Thanks guys!

-Tony

 

[dragondad]

Looks similar to the one I had for a long time, mine was a down firing 15" passive with a built in floor in a 18x18x24 box and had the "dbx" lable on it, got it from a DAK catalog.

I really enjoyed it, used it with a couple radioshack bookshelf speakers in my bedroom for many years. I could knock stuff off the walls in my brother's room with a modest vintage receiver. One of my friends got one too, but he had a much more powerful amp, you could hear it at the end of the block. The shear output of this thing when given some power is pretty spectacular. Not the most accurate or lowest but was a great bang for the buck.

The reason the warning is there, is the sub was designed to be used by everyday people with an everyday receiver. With your choice of typical 8ohm speakers used as the satellites, combined it would present a reasonable load to the receiver. Without the satellites attached, the impedance presented to the receiver is much lower and could burn out a typical inexpensive receiver of the day.

The other result of not having the satellites attached is it changed the crossover point and let higher frequencies to the sub. This does not cause damage, but muddies the overall sound.

Sounds like the reason the previous owner made it 8 ohms is because he wanted to run it without satellites and not have the above mentioned problems

If your pre-amp has the crossover and you have an amplifier that can handle the lower impedance of each voice coil , then I would agree the best solution is to remove the crossover and wire directly.

Since it is a dual voice coil driver, you can power it from 2 channels of an amp, or from a mono/bridged amp wire the voice coils in series. I would not wire them in parallel and drive them from a bridged/mono amp as it will be too low an impedance load for any but the most robust amplifier.

Also, don't be fooled by the modest size of the magnet, it is a rare earth material and very strong.

You will enjoy this sub, I know I did!

 

[haromaster87]

Wow, thanks for all of the great info! Now I'm really excited to get it hooked up. haha

I think I worded my original post poorly. The resistor pack is actually something BSR included with the subwoofer to bump it up to 8-ohm as you mentioned for certain receivers.

But yeah I think everything else you said made perfect sense. I'm going to grab an AudioSource Amp 100 and run the Subwoofer out to it. That amp will do about 150 watts bridged, which is the max that sub will take, so I figure I'll have plenty of potential for volume! haha

If that's the case, I'll pull the driver out and see how I need to wire it for the best resistance. I work with DVC car subs enough to be good on that. This was my first foray into Passive home subwoofers with a built in crossover.

 

[dragondad]

Be carefull. If the voice coils are 4ohm and you wire them in parallel it will present a 2 ohm load, and if you bridge the audiosource it is effectivly a 1ohm load. Some car amps can handle that, most home amps can not. Don't let out the magic smoke

 

[sensei91]

I own two of these. One I purchased new for $ 99.00 from DAK in 1980 I believe. At the time, I had it hooked up to a Yamaha CR-640 receiver , and some JBL L100's. I still have th eL100's as a rear channell in the HT.

When I wired them up , as 4 ohm, they would cause the Yamaha to clip. After calling DAK, they sent me some 8 OHM resistors for free to solve the problem. I used them for many years. After the surround rotted on the woofer, I replaced it, and at that time stuffed it full of acoustic material. I then contunued to use it from time to time in a basement system.

I saw another for sale last year for $ 30.00 on Craigslist, and I couldn't resist. I now have two of them running of of the LFE from my Oppo DVD player. I am actually using the Yamaha CR-640 , that I bought new in 1980, to drive them. I think I have one hooked up in reverse polarity, if I remember correctly.

They aren't close to " high end" and actually not even worthy compared to the rest of this HT system, which has a MaCintosh PreAmp , Amp and Definitive Technologies speakers etc. But it does give off some nice low bass, and since it is in a finished basement, with thick concrete floors, not much room vibration and actually sounds pretty clean, considering. I just leave the Yamaha at 12 o'clock, and let the program material light them up. The funny thing is that the bass from the 45 WPC Yamaha gives it plenty of punch and volume, even keeping up with the main amp when it is pushing 125 WPC listening level.

I could afford to buy another , more expensive sub, but I am not motivated to do so. These work decent enough for the concert videos , which is all I play on this system.

 

[getter365]

I would use the supplied resistors to represent "satellite" loads, keep the crossover points correct, and leave the crossover in place, unless you will never go back and power it with the full audio spectrum and not sub woofer outputs through a power amp.

I have learned that if you have plenty of power, there's no need for a separate sub woofer amp and the passive sub with satellites is actually a nice simple, yet functional setup.

But if you don't want to tax your amp with bass and want to use a separate amp, then just add the resistors to the satellite outputs.

I have used my Cerwin-Vega SW12B (a passive 12" DVC sub with built in stereo crossover for satellites and also from DAK) both ways with great results. Using a separate sub amp gives you more control too. But I left my sub's crossover in place.

My setup now is a classic tube integrated using a separate solid state sub woofer amp with bass level control that sends the bass to the sub and the rest to the satellites since it has a built in crossover. I have some 5 Watt (I think 8 ohm) resistors on the satellite terminals of the subwoofer.

Good luck with your setup. Either way, you'll have some great sound!

 

[Diablita]

Thanks everyone! Just found this thread and decided to go forward with replacing the 15” surround and giving it a listen. Thanks for the resistor recommendation to replace the satellite speakers. I’ll try it both ways!