Cab LPF

[Doodaddy]

I need a pretty gentle sloped (maybe 6db max per octave) LPF around 3-3.5khz for two 8ohm 3012HOs wired parallel to 4 ohms.

What's an easy route to accomplish this?

[dincz]

A 3012HO has a usable frequency range only up to around 4KHz anyway, so I wonder why you'd bother.

[Doodaddy]

Originally Posted by dincz

A 3012HO has a usable frequency range only up to around 4KHz anyway, so I wonder why you'd bother.

I'd bother as I'm finding the two in a standalone application to be overly bright and harsh "up to around 4KHZ" or not. I'm seeing if I can tame it a bit before I trash them all together.

[bongomania]

You could make a simple passive tone filter and insert it in the preamp stage.

[wcriley]

Or use an active crossover with nothing connected to the high pass section.

[Passinwind]

Originally Posted by Doodaddy

I need a pretty gentle sloped (maybe 6db max per octave) LPF around 3-3.5khz for two 8ohm 3012HOs wired parallel to 4 ohms.

What's an easy route to accomplish this?

Turn down the tone control on either your amp or your bass.

[bongomania]

Dude that would be too easy, it's like cheating!

[Passinwind]

Originally Posted by bongomania

Dude that would be too easy, it's like cheating!

[wcriley]

Yep.
Everyone knows the EQ knobs need to always be set at "noon".

[Doodaddy]

Well, this problem is consistent through every bass I've played through it. Incredibly dead strings to fresh in age.

I can't simply eq out the harshness that is being produced; been there, done that. I'm glad I'm not that stupid.

[john m]

Cut the highs on the way in or get a used active cross over and insert it between the preamp and the amp (effects loop?).

A basic low pass filter is a coil, but copper is expensive and the coil would have to be sized to handle the wattage of your system.

Electronic components are cheap, light, and easily tweeked.

[Doodaddy]

Seriously guys? The first assumption made is that I haven't tried "turning the highs down"? Turning a tone knob? That's absolutely retarded and completely wastes of posts.

Originally Posted by john m

get a used active cross over and insert it between the preamp and the amp (effects loop?).

A basic low pass filter is a coil, but copper is expensive and the coil would have to be sized to handle the wattage of your system.

Electronic components are cheap, light, and easily tweeked.

An electric crossover would definitely be the most capable solution offering the most options with little ease. You're definitely right in that suggestion.

I wouldn't automatically say the cheapest, but in any event, I don't rack my head nor do I want to add bulk to the gear. That is the reason why I'm looking at a passive route and mounted inside of the cab itself. As far as power goes, this isn't a high powered system so I wouldn't think it would be too pricey to handle ~300 watts on a larger scale.

If I already carried a rack, I would have immediately went the active route for certain.

[Passinwind]

Originally Posted by Doodaddy

Well, this problem is consistent through every bass I've played through it. Incredibly dead strings to fresh in age.

I can't simply eq out the harshness that is being produced; been there, done that. I'm glad I'm not that stupid.

A passive first order low pass in your cabs will not be any more effective than decently capable active EQ, far less so in most cases. Look at the impedance curve of your drivers around where the 2.5K spike lives. The response curve of the low pass will track that curve and still leave a nasty spike. I'll be happy to graph that for you presently, as I am helping beta test the Windows version of Passive Crossover Designer. Does your cab have a tweeter BTW?

Sorry you didn't take my initial advice in the spirit it was intended in. It works for me every time.

[john m]

Go to a car stereo shop and purchase a choke between

.2 and .4 mH. Put it in series with the input of your cab.

Design guys, please correct me if my values are not correct so I can learn something today.

[Doodaddy]

Originally Posted by Passinwind

A passive first order low pass in your cabs will not be any more effective than decently capable active EQ, far less so in most cases. Look at the impedance curve of your drivers around where the 2.5K spike lives. The response curve of the low pass will track that curve and still leave a nasty spike. I'll be happy to graph that for you presently, as I am helping beta test the Windows version of Passive Crossover Designer. Does your cab have a tweeter BTW?

Sorry you didn't take my initial advice in the spirit it was intended in. It works for me every time.

I do know that the crossover will be limited in its affect on the overall response curve. If I had a selectable frequency high shelving option on either a bass or on the amp, I wouldn't want to cross at the cab. However despite any on board eq on any bass I have or the active or passive section on my Walkabout, I'm not able to tame the cab's very prevalent high frequency presence.

What I'm really hoping to accomplish with the lpf is to really open up my ability to utilize the eq section of my amp/bass instead of anchoring it down by trying to accomplish what I think the LPF would.

One thing that I am concerned about is that 3khz may not be a low enough point to cross at.

I doubt you remember, but a few years ago I had a thread where I was trying to decide on either using the 3012LF or 3012HO in an application very similar to this. I was initially leaning towards the LF, but feared it to be too dark by not extending high enough. Ironically, I feel I'm on the opposite spectrum now. If I could sit right in the middle of those two drivers, I feel I'd be ok. But if the LPF idea doesn't quite work, I'm highly considering the Impero driver. Heck, I still may do it anyway.

Originally Posted by wcriley

Here's a passive crossover at 3K:
http://www.parts-express.com/pe/show...number=260-144

And one at 3.5K:
http://www.parts-express.com/pe/show...number=260-146

Both are 12dB/octave, but might work for what you want.

Thanks, I forgot those existed. While they're considerably steeper than I am really wanting, they're still an option to keep in mind.

[Doodaddy]

Originally Posted by john m

Go to a car stereo shop and purchase a choke between

.2 and .4 mH. Put it in series with the input of your cab.

Design guys, please correct me if my values are not correct so I can learn something today.

Funny you suggest that route. That was really one of the first things I wanted to try as it would be cheap and easy to do. I know that they wouldn't handle the power of a realistic "live" setting, but they may prove functional enough to be a good indicator in a testing environment.

[Passinwind]

Originally Posted by Doodaddy

I doubt you remember, but a few years ago I had a thread where I was trying to decide on either using the 3012LF or 3012HO in an application very similar to this. I was initially leaning towards the LF, but feared it to be too dark by not extending high enough. Ironically, I feel I'm on the opposite spectrum now. If I could sit right in the middle of those two drivers, I feel I'd be ok. But if the LPF idea doesn't quite work, I'm highly considering the Impero driver. Heck, I still may do it anyway.

The OEM 3012 versions I've heard that sit between HO and LF are my favorites, for sure.

[bongomania]

I understand what you're saying about freeing up the EQ knobs for other purposes, so that part makes some sense.

But you already know that a tone knob on a bass is an LPF, and the high-shelving EQ knob on a preamp is an LPF, so I don't know why you think you would get some specially different results if you install yet another LPF. Yes it can (depending on the design) have a different slope than the tone pot on the bass or the high EQ on the amp---but do you know for a fact what those slopes are? Have you scoped those LPF's already? If you haven't, and you don't know those slopes, then how do you know which slope will give you different results?

Also, most people find it perfectly easy to get a dark deep tone with no treble harshness, just using the bass and amp tone/EQ controls. So why is your situation different? I mean physically, materially---why are you NOT able to get those results? That's not a jab at all, that's a real question to ponder. Answering it will lead you to a real solution.

[Doodaddy]

Originally Posted by bongomania

I understand what you're saying about freeing up the EQ knobs for other purposes, so that part makes some sense.

But you already know that a tone knob on a bass is an LPF, and the high-shelving EQ knob on a preamp is an LPF, so I don't know why you think you would get some specially different results if you install yet another LPF. Yes it can (depending on the design) have a different slope than the tone pot on the bass or the high EQ on the amp---but do you know for a fact what those slopes are? Have you scoped those LPF's already? If you haven't, and you don't know those slopes, then how do you know which slope will give you different results?

Also, most people find it perfectly easy to get a dark deep tone with no treble harshness, just using the bass and amp tone/EQ controls. So why is your situation different? I mean physically, materially---why are you NOT able to get those results? That's not a jab at all, that's a real question to ponder. Answering it will lead you to a real solution.

Well, not every bass I have has a tone knob. The ones that do, don't cut enough. My Lecompte has a boost only active pre so I can't cut highs there. The Walkabout doesn't have a shelving knob. So to say I'm expecting different results would be a little inaccurate as I'm not able to accomplish that quite yet as it is.

And you're right. Most people are able to get a dark enough tone. I always have been as well. Specifically with these drivers in this application, I am not able to do that currently. It's odd and it's surprising to be honest. I fully expected to plug, play, and love it. That didn't quite happen. I waited for the drivers to break in, that hasn't really helped either. I waited a good bit of time before starting this thread as I know the direction I'm curious about taking is an unorthodoxed manner.

Originally Posted by Passinwind

The OEM 3012 versions I've heard that sit between HO and LF are my favorites, for sure.

......................those exist? Do tell....

And I forgot to mention earlier, no, there is no tweeter. This is a quick and ugly snapshot of the cab and aesthetically, it's not entirely finished. I still need a grill, but I decided to wait until I was totally happy with the sound.

[Arjank]

Originally Posted by john m

Go to a car stereo shop and purchase a choke between

.2 and .4 mH. Put it in series with the input of your cab.

Design guys, please correct me if my values are not correct so I can learn something today.

Those values won't do much to kill that spike.
If you want to get rid of that spike with passive components you should add an parallel-LCR in wired series with the 3012HO.

You can use the following values:
L = 0,82mh(try to find an air-coil that can handle enough power)
C = 4,7uf (250v dc minimum)
R = 22ohms (use one with a high power rating or wire several resistors parallel)

The value for R can be increased to increase the reduction of the 2.5khz spike. The current value is good for -6dB.