Bass Cabinet as Woofer?

[Quilly]

Quick Question,

I've an 800W / 4 ohm oldish Schroeder cabinet, could this be repurposed as a woofer to accustom PA tops. I have an 800W thomann power amp. Would I just destroy the drivers with kick drum etc?

     

 

[Bill Fitzmaurice]

You might not destroy it but it won't give the results that a real subwoofer will. Depending on what you have for tops its response may go only slightly lower, if at all.

[Quilly]

29 minutes ago, Bill Fitzmaurice said:

You might not destroy it but it won't give the results that a real subwoofer will. Depending on what you have for tops its response may go only slightly lower, if at all.

As far as I know the tops are general purpose 300w pa speakers , if the additional powered bass cab would give the overall sound a little “push” I’d be happy enough 

[Baloney Balderdash]

3 hours ago, Quilly said:

As far as I know the tops are general purpose 300w pa speakers , if the additional powered bass cab would give the overall sound a little “push” I’d be happy enough 

Might work this way actually, depending on the specific bass cab and which speaker(s) is/are in it, though I would properly throw in a HPF set at around 40Hz or so on the bass signal, iedeally placed somewhere towards the end of your signal chain, after eventual effect pedals, to decrease the risk of damaging the speaker(s) by using it/them as a woofer. 

Edited October 1, 2020 by Baloney Balderdash

[Quilly]

29 minutes ago, Baloney Balderdash said:

Might work this way actually, depending on the specific bass cab and which speaker is in it, I would properly throw in a HPF set at around 40Hz or so on the bass signal (after the crossover?) to decrease the risk of damaging the speaker by using it as a woofer. 

I’m beginning to think it’s probably less risky to use a subwoofer with a built in crossover 

[Bill Fitzmaurice]

You wold need some method of high passing the tops in any event, assuming they don't have it built in.

[Marvin]

I used to have the Schroeder 1212L (800w). It had a real mid-range kick to it. It was considerably less 'bassy' than say, the Ampeg 410 I had.

[Phil Starr]

bass cabs aren't really designed to do what PA subs do. You don't really need a lot of subsonic bass out of a bass cab, there's a limit to how mush bass a bass pickup puts out so the actual amount of deep bass is fairly low often they don't go much below 50Hz and frequently they can't handle full power over the next octave. They also have to cover the full range of a bass and this means a compromise in the lower frequencies. The speakers in a sub only have to cover a couple of octaves and nothing over 150Hz so they are specialist one trick ponies and they can do that well as a result.

However if you have them and you lack bass from your PA you have nothing to lose by trying them, you'll need a crossover to limit the frequencies you send to them and probably to limit what goes to the tops. If you can borrow a crossover it will let you experiment and you can see if it works for you. It won't be perfect but if it is an improvement then why not?

However there is another possible route. If you can send the kick and bass feed out through an aux channel on the mixer you could send them through your Schroeders freeing up the tops from having to deal with any deep bass. Aux fed subs are an accepted technique which might be worth a try. You can then filter everything else through the mixer at 80Hz, which you should be doing anyway.

[Dan Dare]

Bill's advice is good. If you just want to add a bit of low end weight to a mainly vocal PA (I've done it in situations that didn't call for my main PA and subs), a bass cab can work, but watch the volume and don't try to put high levels of kick, bass, etc through it. As well as high passing the signal to the amp that powers the top cabs, you'll ideally need to remove mid and high frequencies from the send to the amp that powers the bass cabs. If you have a digital mixer, this is all simple to do, of course. Some analogue mixers can provide a low passed signal for subs and you can use a graphic to remove low frequencies from the signal to the tops. Reasonable active subs can be picked up quite cheaply used. Most have on board processing which will provide a high passed signal for top boxes.

[JohnDaBass]

All interesting information, thanks to everyone. 

What about the other way round?

Say adding a PA woofer to a BF One10? 

Amp into sub out of sub to the BF One10. 

Sub filters the lows below 180hz leaving the One10 to cover the rest. Would it not help the One10 to perform more efficiently & if the sub was 8ohm the amp would push more when presented with a 4ohm load.

Just interested in views. @Phil Starr, @stevie, @Bill Fitzmaurice, @Chienmortbb

Edited October 7, 2020 by JohnDaBass
Error

[Bill Fitzmaurice]

Unless the BF One10 is particularly anemic in the lows, which I doubt, the best bet if one isn't adequate is to add another.

[Phil Starr]

If you are going to use a crossover at 180Hz then you won't be running into 4ohms. Below 180 you'll be running into the sub and above that  into the One 10, both at 8 ohms. At the crossover point the impedance of the crossover in series with each speaker effectively makes them both 16ohms (sort of) and so the overall 8ohms is maintained all the way. No free watts I'm afraid

 What you will do is change the sound, hence Bill's suggestion you go for a second One 10. The One10 is designed to be 'old school' compensating for the lack of deep bass with a bit of bass boost baked in at around 100Hz, which i for one really like. If you colour in the missing frequencies it will change the balance of the speaker. You'll get more deep bass probably as you'd expect, you might find one of the speakers is more efficient than the other and will dominate. What you will get is the possibility of better power handling as the power is split between the speakers. with everything below 180Hz diverted away from the One 10's you could possibly double the amp power, or just trde that for the same amp with less distortion.

If you have the woofer then the proof of the pudding is in the listening in this case, give it a try and if you like it try it more  If you don't then save up for a second One 10

Edited October 7, 2020 by Phil Starr

[JohnDaBass]

So I did some "Proving of the Pudding" today and, as usual, Phil Starr was spot on with his analysis and advice.

Connected one of the EV-SB122 subs to my Fender Rumble HD 800 and the BF One 10 and sure enough the whole character of the sound changed dramatically. Set the amp EQ flat and A/B 'd with & without the EV-SB122.

The One 10 has a lovely olde school warmth with my Fender P's and it truly is a joy, but adding the Sub added a huge girth and deep bottom end push to the sound. No loss of the natural One 10 sound just more thunder in the low end.

So, in conclusion, to my ears, adding the sub increases the output performance of the setup making it sound sort of "Bigger". I generally use the BF One 10 & Fender Rumble 500 for Pub Jams and home use, on it's own it struggles even at rehearsals with our noisy Gittaaarist , keys & drums but I just think it may well cope with the added Sub.

The EV-SB122 subs were recently purchased to add to the EV Z1s to improve the performance for the 3 Vox so they will not be used for my bass setup. ( Main Bass rig is 1 or 2 BF Super Compacts with either the Fender Rumble HD 800 or a Mesa Subway D800)