Sub Advice

[pitdiver]

Guys a question. I am thinking on purchasing a powered sub perhaps a QTX 15SA. However I am not sure how I can connect it to the Mixer/Amp set up. As I understand it you can use a crossover and go down that road but at the moment that is on the back burner. Am I right I can run a powered sub from a line level output on the mixer. eg Booth on my Numark M6 for instance.

Ocasionally on small functions where basically I am just supplying music I use my Numark M101. Can I use the Headphone output for the Powered Sub in this case.

RH

[Andy P]

When I use one of these I just connect it in line before the speaker on one side. As bass is 99% of the time recorded mono it doesn't need a stereo feed or to pick up both channels.

[Excalibur]

Guys a question. I am thinking on purchasing a powered sub perhaps a QTX 15SA.


When I use one of these I just connect it in line before the speaker on one side.

Normally I'd advise against this, but as far as I can tell from reading up about the QTX sub on an earlier question, it doesn't filter the output to the tops. Thus, both top cabs will still be getting in effect the same signal, ie full range. No extra crossovers needed.


As bass is 99% of the time recorded mono it doesn't need a stereo feed or to pick up both channels.

Correct. However, if you get a sub such as the Alto series, they have two inputs. This means you connect your two mixer cables straight into that, no problem. Then you have two options. You can connect your tops to the filtered outputs, so that they don't have to reproduce the low frequencies which muddy the sound and sap power.
Alternatively, if you simply want to add bass, you can still feed the tops with a full range signal from the sub. Whichever sound you prefer is fine.

I usually recommend the Alto, as it's about the cheapest cab with this facility. Spend more money, and the choice is vast. Spend less, and it's rocking horse poo time, unless you find something s/h at a bargain price. :D

Edit: Cheap subs are going to add to the overall sound, and will usually make it sound fuller and clearer. They won't shake the optics off the bar, or have your flaxen locks blowing in the breeze. That effect requires the expenditure of quite a bit of power, and similar amounts of cash.

[pitdiver]

I just want to add a bit of bass. No optic shaking or anything like that. My problem is feeding it from the mixer, Can I take a feed from the "record" outlet on say a Numark M2 mixer

[Excalibur]

I just want to add a bit of bass. No optic shaking or anything like that. My problem is feeding it from the mixer, Can I take a feed from the "record" outlet on say a Numark M2 mixer

I fear you have misunderstood the thrust of my argument. Presumably, you have two main out sockets which you feed your existing speakers with. I assume they're active speakers. With an Alto sub ( other brands are available ) :D :D you simply connect your mixer to the sub instead, and then from the sockets on there to your tops.
If you have passive tops and an amplifier, the same applies, just feed the amp with the outputs from the sub. Regard the sub as a mixer, if you like.

Using the rec outlets to feed anything of this type is not a good idea, because they usually bypass the tone control circuitry, and have a much lower output.

As long as you're using actives, Andy's suggestion of just using one sub in line with one top will work acceptably well with a single channel sub, such as the QTX, but it's not ideal. In this case, you're better with two, to match things up, and by that time, you're aproaching the cost of an Alto, which is far better equipped. If you're using passives, it's not at all a good option.

[pitdiver]

No I use passive speakers, a the moment KAM ZP12's with a KAM KXR 300V2 amp. This is the kit I will be using until possibly next year. If fitting in a sub is going to cause agro I think I may well as forget it for now. As I said in a previous post just wanted to add an extra bit of bass.

[pitdiver]

I have just been offered an Alto ZMX122 mixer. This apparently has an output to "Control Room" could I use this as a feed for a powered sub.

[Andy P]

Using control room is not ideal as it often lacks any eq. I may be wrong but you can feed into the sub before the amp is using none powered tops. The output from the sub should only be carrying signal.

[Nakatomi]

If you don't have any way to roll off the bass end on the tops things could get a bit muddy if you're not careful. As far as I know you can limit the upper range of the qtx active sub so that would help, assuming the active sub rolloff can go as high as your tops low end.

Active subs with filtered mid/top outputs cost a wee bit more than the qtx though.

[Retrodisco]

Run it off the line level output on the mixer if you have one free.

Booth output I've used before.

[Excalibur]

No I use passive speakers, a the moment KAM ZP12's with a KAM KXR 300V2 amp. This is the kit I will be using until possibly next year. If fitting in a sub is going to cause agro I think I may well as forget it for now. As I said in a previous post just wanted to add an extra bit of bass.


I have just been offered an Alto ZMX122 mixer. This apparently has an output to "Control Room" could I use this as a feed for a powered sub.




Active subs with filtered mid/top outputs cost a wee bit more than the qtx though.


Run it off the line level output on the mixer if you have one free.

Booth output I've used before.

For the third time, if you get a sub like the Alto ( or equivalent) you need no repeat no extra outputs. Nil. Not any. Zero. None.
Mixer into sub, outputs from sub into your existing amp, piece of cake, job's a good 'un. You'll also have a choice of running your tops with high only, or full range.

Adding one sub to passive cabs, the answer's always an active sub.

[ckpr2]

I just run a 15 inch sub in parallel with a full range speaker.
I know I should have a crossover but it sounds fine as is.

[ukpartydj]

When I use one of these I just connect it in line before the speaker on one side. As bass is 99% of the time recorded mono it doesn't need a stereo feed or to pick up both channels.

I go to the speaker first then the sub. Same as you - just on the one side - originally thought it'd be a bad idea and always brought 2 of these subs bit realised one day that I never turned one of them on and it sounded fine!
Now I mostly use 1!

There is a frequency adjustment so I always set mine to what I think is 80hz so I'm only adding low bass which my 10“ speakers cannot do rather than adding more mid bass.

[pitdiver]

Thanks for all what appears to be contradictory advice. However taking it all on board I think I will go with what Excalibur advises and get the Alto. As I have only a relatively small kit what Alto Sub is recommended. Is this one suitable for instance
http://www.getinthemix.com/pa-sound/subwoofers_1/alto-truesonic-ts-sub-12-active-subwoofer.htm

[Excalibur]

Is this one suitable for instance
http://www.getinthemix.com/pa-sound/subwoofers_1/alto-truesonic-ts-sub-12-active-subwoofer.htm

Since you're using 12" tops, it is acceptable. Better results will come from a 15", which costs around £300. They come up s/h around £200 if you keep looking. Not quite £200 (http://www.ebay.co.uk/itm/Alto-Truesonic-TS-SUB15-TSSUB15-Truesonic-PRO-15-Active-Subwoofer-/291453396204?pt=LH_DefaultDomain_3&hash=item43dbf9e4ec)


There's a pair of 18" Altos currently at £300, now that would work! :D

[Nakatomi]

It's still worth pointing out here that merely running subs in parallel with mid/tops, if they're not matched maybe isn't a good idea. It isn't just about the load impedance the amplifier sees it's to do with frequency response.

Say you have an all passive pa and your mid/tops go down to 70Ha and the subs reproduce up to 150Hz. The overlap can produce a hump in the overall system frequency response. In some cases if the cabs are well matched it can work well, but if not, your bass end can be uneven & boomy on some notes.

The same applies if you can't tune active speaker frequency response too. An active crossover either on the sub or independent, can alleviate this. The alto sub does indeed have a true active crossover meaning that audio at the input is split between the sub and mid/tops around the crossover frequency. The QTX sub on the other hand passes all frequencies to the 'through' output as far as I can tell meaning that you can't roll the bass end off the mid/tops unless they have a control onboard to do this themselves. You can adjust the highest bass frequency the qtx sub reproduces but that isn't as good as a proper crossover. Also, the alto active subs can take a stereo signal into one sub and output mid/top to a stereo pair. The qtx subs cannot.

There's also a question of the true power of those qtx subs. Dicky has found that 600Watts is a very optimistic figure for one particular model where it uses an amp chip capable of maybe 60WRMS, assuming the power supply is up to the job (and it looks like it isn't!).

I like the idea of the alto subs, and 300 quid for a pair 2nd hand is better value than 150 or so for a new pair of the qtx.

[Excalibur]

Typed on mobile, so please excuse any typos. Juski is absolutely correct in all the above. Only thing I wish to add is about the power output of the Alto subs. It's wildly optimistic, and I looked into boosting it a bit. That wasn't cost effective.
It adds to the overall sound, and can allow your tops more leeway, as they're not reproducing the bass frequencies which take a lot of power. Also it reduces the range of frequencies it's producing, which should mean clearer sound.

If you want to hit people hard in the chest with a pounding bass, it's useless. If you want an easily portable unit to add bass and clarity to a smallish rig, it's perfect

[Nakatomi]

Typed on mobile, so please excuse any typos. Juski is absolutely correct in all the above. Only thing I wish to add is about the power output of the Alto subs. It's wildly optimistic, and I looked into boosting it a bit. That wasn't cost effective.
It adds to the overall sound, and can allow your tops more leeway, as they're not reproducing the bass frequencies which take a lot of power. Also it reduces the range of frequencies it's producing, which should mean clearer sound.

If you want to hit people hard in the chest with a pounding bass, it's useless. If you want an easily portable unit to add bass and clarity to a smallish rig, it's perfect

I was wondering about the output when I was looking at the specs. They quote 45Hz low response at -10dB - I'm really not sure how much bass extension they'd give my Mackies, if any. I can cut the SRM450s off at 70Hz (or 75Hz?), but it's still not taking much load off the mid/tops. Then again, I've seen single Mackie powered subs for less than £400 on the Fleabay lately. I've heard SRM450s with subs & they blew me away compared to those without - but 450s with 2x Mackie subs would be way too much for a wedding of 120 guests in a small hotel with bedrooms above :lol:

Mind, I'm pretty sure I wouldn't get away with even one SWA1501 - not at 45 kilos - then there's the size of the thing.. I'm gonna be using the family Ford Focus estate for transport to start with. Methinks I'm a gonna need to do some serious audio auditioning before I make up my mind

[pitdiver]

Further on from earlier posts I have a slightly different question to ask. For arguments sake let's assume I have two separate PA Systems both with power amps and matching passive speakers. Let's also assume I have an inexpensive mixer similar to the Alto ZMX122. How could I connect the two system to the one mixer.

One output could come from the main mix output but what about another feed would that be from an Aux out or from the control room feed.

The reason I ask is that I sometimes do gigs in a particular venue where I would like to use two different inputs eg from two different laptops playing two different types of music in two different areas. Perhaps this is not possible with different inputs but can it be done with a common input but to two different systems, to two different areas

Hope that makes sense

[Excalibur]

How could I connect the two system to the one mixer.

That can be easy. Many modern amps have two sets of sockets in the back. Plug your mixer into one set as normal. Then connect cables from the remaining pair into the inputs of your second amp. Called Daisy Chaining. Let us know what amps you have, and we'll see if that's a runner.


The reason I ask is that I sometimes do gigs in a particular venue where I would like to use two different inputs eg from two different laptops playing two different types of music in two different areas. Perhaps this is not possible with different inputs but can it be done with a common input but to two different systems, to two different areas

Hope that makes sense

Same sound to both, exactly as above, no problem.
Different sound to both, well that's trickier. The Alto may struggle, I haven't read, learned, and inwardly digested the manual. :) Larger mixers would have the facility to pass different channels to different outputs. I can't give an example off the top of my head, but the larger Behringers usually make less than £100 s/h, and I know for sure my 1832 would do it. Possibly the 1204 would, but I'd have to check that, I'm not at all confident that it would. The 1222 almost certainly would.

Hold the front page! Perhaps it's possible with the Alto. Perhaps. You have dials marked " Aux send ". Possibly, if you turned these up, and the corresponding ones at the bottom down, it could work. Your second set would be fed by the Aux Send socket. It's possible to test this with just one system. Feed the left channel of the amp with the normal output, and the right with Aux send. Play different things into each channel, and see if it works as we hope.

You'll be restricted by the fact that effectively, you've only got two line channels on the Alto. That explanation is complicated, if you're baffled by any of it, keep asking. The only silly questions are the ones that don't get asked.

[Twinspin]

How I understand it you would need a BUS built in the mixer (Can route specific audio signals) to a specific output

[Nakatomi]

You can do this kind of thing if the mixer has an Aux bus, or aux sends. Sometimes they're only mono though, so watch out for that.

[pitdiver]

Here is the spec for the Alto
http://www.altoproaudio.com/products/zmx122fx

As for amps KAM KXR 150V2+ KAM KXR 300V Remember guys I tend to do very small gigs in our local Village Hall and also supply PA for Bingo night and the such like.

[ukpartydj]

It's still worth pointing out here that merely running subs in parallel with mid/tops, if they're not matched maybe isn't a good idea. It isn't just about the load impedance the amplifier sees it's to do with frequency response.

Say you have an all passive pa and your mid/tops go down to 70Ha and the subs reproduce up to 150Hz. The overlap can produce a hump in the overall system frequency response. In some cases if the cabs are well matched it can work well, but if not, your bass end can be uneven & boomy on some notes.

The same applies if you can't tune active speaker frequency response too. An active crossover either on the sub or independent, can alleviate this. The alto sub does indeed have a true active crossover meaning that audio at the input is split between the sub and mid/tops around the crossover frequency. The QTX sub on the other hand passes all frequencies to the 'through' output as far as I can tell meaning that you can't roll the bass end off the mid/tops unless they have a control onboard to do this themselves. You can adjust the highest bass frequency the qtx sub reproduces but that isn't as good as a proper crossover. Also, the alto active subs can take a stereo signal into one sub and output mid/top to a stereo pair. The qtx subs cannot.



I'm pretty sure it doesn't roll the bass off ... however it works for some people like me because:

Mackie SRM450's tail off at 80hz ....... 45hz it's -10db
RCF 310a tail off at 85hz ........ 65hz it's -10db but more importantly at 80hz it's -2db

I use the RCF's with the QTX subs so by setting the maximum reproduced by the QTX subs to 80hz (roughly) the amount of crossover between the two is barely anything at all.
With my RCF's I'm not trying to take the load off them though, I'm trying to add bass.

When I do larger events the RCF tops always go through the RCF sub with the crossover.

Actually thinking about it ... the Mackie SRM450's are -10db at 45hz, and the Alto's are -10db at 47hz ... isn't that worse than the mackie ??? Is that what you were trying to say?
Might as well but a mackie on the floor and put a low pass filter on it!

[Nakatomi]

I'm pretty sure it doesn't roll the bass off ... however it works for some people like me because:

Mackie SRM450's tail off at 80hz ....... 45hz it's -10db
RCF 310a tail off at 85hz ........ 65hz it's -10db but more importantly at 80hz it's -2db

I use the RCF's with the QTX subs so by setting the maximum reproduced by the QTX subs to 80hz (roughly) the amount of crossover between the two is barely anything at all.
With my RCF's I'm not trying to take the load off them though, I'm trying to add bass.

When I do larger events the RCF tops always go through the RCF sub with the crossover.

Actually thinking about it ... the Mackie SRM450's are -10db at 45hz, and the Alto's are -10db at 47hz ... isn't that worse than the mackie ??? Is that what you were trying to say?
Might as well but a mackie on the floor and put a low pass filter on it!

On paper it doesn't look as if even the alto sub would add anything. Unless I'm proved otherwise I'll be saving for something better.

Do your qtx subs make a difference worth having? I'm guessing that almost an extra octave of low end will improve the sound but is it worth it for the extra lugging around & wiring up? I need a demo, I think.

[Andy P]

Having used the QTXs myself I would definitely say the add something even if on paper the frequency range isn't increased. On the flip side after a year they do self destruct inside

[ukpartydj]

On paper it doesn't look as if even the alto sub would add anything. Unless I'm proved otherwise I'll be saving for something better.

Do your qtx subs make a difference worth having? I'm guessing that almost an extra octave of low end will improve the sound but is it worth it for the extra lugging around & wiring up? I need a demo, I think.

Well the RCF 310a's have very little bass in my opinion so it may not be the best example. When I pack away I sometime leave a track on in the background and when I turn the sub off you really notice the difference.
I'd imagine with the SRM450's you don't need as much of the mid-bass added so my theory is you could achieve more volume from the QTX sub... maybe?

If I'm feeling it at the weekend I might use my Mackies and the QTX to see if they work well together.

[Nakatomi]

Well the RCF 310a's have very little bass in my opinion so it may not be the best example. When I pack away I sometime leave a track on in the background and when I turn the sub off you really notice the difference.
I'd imagine with the SRM450's you don't need as much of the mid-bass added so my theory is you could achieve more volume from the QTX sub... maybe?

If I'm feeling it at the weekend I might use my Mackies and the QTX to see if they work well together.

Yup. I think I'm definitely going to need to have a demo with my SRM450s somewhere. I can't see me carrying around two 45 kilogram subs until I've got a van & a little helper.