Low Pass filters

[Monckyman]

I`ve been experimenting with lots of different cabs lately, trying to find a nice combination.
What I`ve been finding is using a 15" with either a 210 or 410 is producing a large peak in the low mids, at a guess somewhere between 160Hz and 400Hz.
This is because both cabs are quite good at reproducing those frequencies
I can roll this off the amp and it sounds flatter, but I don`t like having to use valuable eq on the amp to correct a flaw in my choice of cabinet.
I know the Boffins will be here soon enough telling me not to mix my drinks, but to put it simply, I want to.
And from what can tell from what you lot are using, you do too.
So, with that in mind, has anyone tried using a low pass filter either inline (built into a cable for instance) or switchable in/out on the back panel?
Or simply available on one input, while the other input remains full range.
I`d try it at 160Hz initially.
I realize this won`t be the most efficient use of the cab with the filter on, but it would enable the use of that cab in a much more versatile way, ie: in a combi stack, or on its own.
From what I can tell from people on here, they mainly [i]add[/i] a 15" to add that depth at low frequencies and not for definition or clarity.
Does this make sense to anyone?
I`m tempted to either make or buy one off the shelf and try it out, you never know, it might make all the difference.
MM

Edited June 24, 2011 by Monckyman

[xgsjx]

Why not put the LPF between bass & head? Get a moog MF-101.

The large peak in the low mids is most likely due to different sized soundwaves bumping into one another. What sounds good in one venue may sound guff in another tho due to room acoustics. The reason having same sized drivers is suggested is so that you don't get pleasent & unpleasent surprises, just the same at everywhere.

[JTUK]

I have used 15" on the bottom of other cabs but now I use 2x210's which is far better for me. You don't get the mud of a 15".....everything is clearer all round, IMO.

Not saying you should do this....as you have your own ideas, but just that I wouldn't add a 15" to a stack. The last thing I want is more bass..I can add that anytime I like. It is getting rid of unwanted bass that is/can the problem.

[escholl]

[quote name='Monckyman' post='1281231' date='Jun 24 2011, 04:53 PM']I can roll this off the amp and it sounds flatter, but I don`t like having to use valuable eq on the amp to correct a flaw in my choice of cabinet.[/quote]
er, what? that's what EQ is there for...

valuable, maybe, but not worth anything if it's not being used!

[Monckyman]

All reasonable answers but,
Yes I understand the concept of crossover points and the overlapping of certain resonant frequencies, that`s what I`m trying to negate.
1/I don`t subscribe to the same brand theory. thousands of bassists use different brands all the time quite happily.
2/You can only add so much bass into a couple of 210 before it reaches it`s limits.
I suppose what I should say is SUB bass. If you need a nice fat dub sound, it`s not going to happen at the volume required.
I understand most of the time a cleaner more defined sound is preferable, and for 50% of my set, I`m with that.
But I need the capability to wind in that sub.
I have considered going 2x15, but that rig probably won`t be tight enough to cover the funk/pop stuff.
3/I could use the EQ to flatten off yes, but then when I need that EQ for another job, it`s gone just making the stack work. So half a solution.
I could stick a graphic eq across it I suppose, but you`re right, it does seem ridiculous.
4/ I don`t want a b-amped rig, though that would work the best I think.
What I`m suggesting is a cheap workaround in preventing unwanted frequencies getting to the lower cab.
There are many multi speaker cabs arranged exactly like this.
OK, again, thanks for the replies. Much to consider.
I definitely think it`s worth trying an LPF out, if only to convince myself I`m talking out of my arse.
MM

[xgsjx]

If it's sub you're after then why not add a sub?
I've long been toying with the idea of adding a folded horn sub (maybe a BFM Tuba) for getting that low end moving more things.

A good 2x10 can give you just as much "bass" as a good 1x15. It's not so much what size the driver is, but how well tuned the cab is.

[Monckyman]

[quote name='xgsjx' post='1282222' date='Jun 25 2011, 03:54 PM']If it's sub you're after then why not add a sub?
I've long been toying with the idea of adding a folded horn sub (maybe a BFM Tuba) for getting that low end moving more things.

A good 2x10 can give you just as much "bass" as a good 1x15. It's not so much what size the driver is, but how well tuned the cab is.[/quote]
Yep, can`t argue with that.
I just wanted a possible cheap way of preventing frequency overlap when using the 15" as an add on.
Seemed to me a LPF would allow that, and not be permanent or expensive.
I`ll go and have a good think.
Ta
MM

[escholl]

[quote name='Monckyman' post='1282227' date='Jun 25 2011, 04:03 PM']Yep, can`t argue with that.
I just wanted a possible cheap way of preventing frequency overlap when using the 15" as an add on.
Seemed to me a LPF would allow that, and not be permanent or expensive.
I`ll go and have a good think.
Ta
MM[/quote]
If you LPF one cab, you are going to further change the phase relationship between the cabs, which may be helpful or not but will be difficult to predict. I really think you should just use the EQ -- it's what it's there for. Or get a different cab, or something -- I'm really not convinced this is the solution.

However, I've been wrong before so if you get it working do please let us know

By the way, does this happen in a variety of rooms, even very large ones? I only ask because 160-400 Hz are very common small to medium sized room resonances -- if you've only tried it in small rooms, it may not be the cabs at all.

[Monckyman]

Thanks for the reply, yes I understand how it may be the context that`s emphasising certain freqs, and I can cut them reasonably well on the amp eq.
I`ve asked a P.A firm friend to see if he has something knocking about that I can try out.
I`m fully expecting to be proven wrong but it`s just an idea I want to try.

MM

[Mr. Foxen]

[quote name='xgsjx' post='1282222' date='Jun 25 2011, 03:54 PM']If it's sub you're after then why not add a sub?
I've long been toying with the idea of adding a folded horn sub (maybe a BFM Tuba) for getting that low end moving more things.[/quote]

Bear in mind with a horn, you have to high pass everything else, because the horn will be the equivalent of the length of the horn behind everything else, so can be tons of phase fun, its like 15 feet or something in the big BFM horns.

Edited June 25, 2011 by Mr. Foxen

[Phil Starr]

[quote name='Monckyman' post='1282252' date='Jun 25 2011, 04:37 PM']Thanks for the reply, yes I understand how it may be the context that`s emphasising certain freqs, and I can cut them reasonably well on the amp eq.
I`ve asked a P.A firm friend to see if he has something knocking about that I can try out.
I`m fully expecting to be proven wrong but it`s just an idea I want to try.

MM[/quote]
a good quality LPF isn't going to be cheap and without some way of measuring you could end up trying at the 'wrong' frequency to get the result you want. If your PA friend can lend you a stereo amp and an active crossover you can try different frequencies and different roll off slopes really quickly, then you can decide what frequency you want to crossover at and whether you want to use a high pass filter on one cab a low pass on the other or a full crossover. Use your bass amp as a pre amp if you have the right output (but use a dummy load if it is a valve amp).

Have fun

[Wally]

Re Phil Starr's advice above

Stereo amp with variable freq crossover here -

[url="http://basschat.co.uk/index.php?showtopic=140865&hl=megabass"]http://basschat.co.uk/index.php?showtopic=...amp;hl=megabass[/url]

Don't let the watts put you off if interested as those are old school american watts though does need 4 ohm cabs

[dannybuoy]

If you have 2 amps or 2 channels you could also try the sfx X&M, I believe there's one going in the classifieds. It's a crossover and mixer in pedal, if you just use the crossover half you can send your highs to one amp and your lows to another.

[dannybuoy]

If you have 2 amps or 2 channels you could also try the sfx X&M, I believe there's one going in the classifieds. It's a crossover and mixer in pedal, if you just use the crossover half you can send your highs to one amp and your lows to another.

[Monckyman]

Thanks for the replies.
I have someone sourcing me a filter.
It needs to be the same ohmage and watts (or more) than the cab it is intended for.
I`ll give it a wiz and report back if it`s any use.
MM

[LawrenceH]

Hi,
I suggest using a high pass filter on the top cab would be better - you can then get away with setting it at the high end of the frequency range so keeping the cost/weight of large passive components down, also it will protect your top cab from overexcursion. In all probability it's not contributing much useful to the real lows anyway.

By the way I would expect phase to be a non-issue, in rough'n'ready bass guitar terms, given that the frequencies we're talking about are a bit too high to be affected by correctly tuned reflex ports. It'll be an issue in the 40-150-ish region which you don't seem to find problematic anyway, but if you use an HPF then that issue will disappear as well.

[voxpop]

I did a similar thing with a trace rig some years ago. I had a 2x10 with a 15 and wanted the 15 to just handle the very lowest frequencies. I put in a hand made induction coil from Wilmslow audio with a cut off of 100hz. Only frequencies below 100hz get into the cab. Simply wire it in-line inside the cab. Cost was about £50 if I can remember......

[attachment=83731:DSCN1433.JPG]

I made a small box and put the inductor into the cab and filled it with silicon to stop it moving and to deaden down any vibrations.... you can still see some of the silicon stuck to the coil.

Hope this helps.

Edited June 30, 2011 by voxpop

[alexclaber]

Although you can try to use an inductor as a passive speaker level low pass filter, the problem with using one that low down is that you're very close to the box resonances, so the theoretical low pass transfer function based on the nominal impedance is nothing like what you really get due to the interactions with the impedance peaks. It will however successfully cut off higher frequencies but in the process it makes the low frequency response go a bit haywire. That's a pretty big coil, no wonder it cost so much!

[Monckyman]

Thanks all for your replies, we`re getting somewhere now!
Voxpop, the crucial question is, did it improve your sound?
Alex, if I understand correctly you are saying a filter wouldn`t just passively prevent frequencies above the roll off point getting to the driver, but would distort the response of the remaining frequencies the cab produces unpredictably?
Hmmm.
I will look into the high pass alternative also.
MM

[voxpop]

[quote name='Monckyman' post='1287369' date='Jun 30 2011, 09:56 AM']Thanks all for your replies, we`re getting somewhere now!
Voxpop, the crucial question is, did it improve your sound?
Alex, if I understand correctly you are saying a filter wouldn`t just passively prevent frequencies above the roll off point getting to the driver, but would distort the response of the remaining frequencies the cab produces unpredictably?
Hmmm.
I will look into the high pass alternative also.
MM[/quote]

Yes it dd improve the sound. It sounded like a 2x10 with a sub.... Punch with deep bass.

[LawrenceH]

If the OP is right about which frequencies are problematic, then they're a bit high to be typical reflex port-related phase shifts combining badly. It's probably just a volume thing.
However, adding a filter will introduce its own phase shift - I just don't think it'll be that much of a problem in practice. Best solution is proper bi-amping with an active 2-way crossover. Next up, passive, but it'll be expensive to do properly.