Three-way cabs

[JPJ]

So years ago I used to run an SWR Triad which was the sweetest sounding if underpowered cabinet I’ve played through. Then I got my hands on a Schroeder 21012 which whilst probably more a two-way cab was the best single cab room filling solution.

When Alex started Barefaced he placed a lot of store in three-way designs with a dedicated mid-range driver although he’s subsequently moved away from that approach. 
So given the advances in loud speaker design would a modern three-way design be viable as a single cab solution (I’m thinking a 1200W Triad)? 

[BigRedX]

For a 1kW+ system you'll need to run your crossover for the bass and mid-range drivers before the power amps.

[JPJ]

8 minutes ago, BigRedX said:

For a 1kW+ system you'll need to run your crossover for the bass and mid-range drivers before the power amps.

Ah that might explain it then - not having much electronics know how is this because of the physical size of the crossover components that would have to be used in the cabinet?

[BigRedX]

3 minutes ago, JPJ said:

Ah that might explain it then - not having much electronics know how is this because of the physical size of the crossover components that would have to be used in the cabinet?

 

And the amount of power that you'll lose as heat in the process.

[Dan Dare]

Modern bass/mid drive units and tweeters/horns extend into the midrange so well that a dedicated mid driver is a bit redundant these days. As BigRedX says, the need for a complex and power absorbing crossover (if you go passive) makes it difficult to do well. An active system is probably best if you really want to go that way, but you need additional power amplification and an active crossover, which can work out expensive. Unless we're trying to be Billy Sheehan, many of us tend to roll off mids anyway, rather than boost them.

[Bill Fitzmaurice]

46 minutes ago, BigRedX said:

For a 1kW+ system you'll need to run your crossover for the bass and mid-range drivers before the power amps.

Not necessarily. For one thing you'd need at least two premium fifteens to handle even 800w. Passive crossovers can handle that.

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because of the physical size of the crossover components that would have to be used in the cabinet?

The crossover wouldn't likely be below 800Hz, so the size and price of the components wouldn't be a problem.

Quote

And the amount of power that you'll lose as heat in the process.

The amount of power loss with a well designed crossover is insignificant. Bi-amping and tri-amping make sense with large PA systems, but where electric bass cabs are concerned it's an unnecessary level of complexity.

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When Alex started Barefaced he placed a lot of store in three-way designs with a dedicated mid-range driver although he’s subsequently moved away from that approach.

That was probably because they didn't sell well. My preference is for a 2 way, albeit crossing over to the HF element at 2kHz. The typical 2 way bass cab crosses over at 4kHz, resulting in poor off-axis response in the 2kHz to 4kHz octave. There's also no reason for having response above 8kHz. Even slap and pop doesn't go higher than that.

[BigRedX]

Thanks for the correction Bill.

 

I ran a bi-amped system in the 90s with a 1x15 bass cab and a home made 2x8 cab based on the speaker housing from my favourite guitar combo, but that was mainly so I could have extreme chorus, flange and delay effects on my bass without sacrificing any of the bottom end clarity. It worked very well and wasn't any real hassle apart from having to educate every PA engineer that they shouldn't run both channels of bass DI at the same volume to get the correct bass sound. Eventually we got our own sound engineer and even that problem went away.

 

Because of this I'd always assumed that putting the crossover for anything other than tweeters before the power amps was a more efficient way of doing things.

[Bill Fitzmaurice]

Way back when 25 watts was a big amp bi-amping was employed to give more power to the system, and to save HF drivers. When a full range amp was pushed to clipping, which was common when the power available was so low, that clipping resulted in harmonic levels far above normal, and that would toast high frequency drivers. That's no longer an issue today, but modern digital crossovers allow very high filter slopes. 24dB/octave is the practical limit with passives, while 48dB/octave is common with digital signal processing. Very high slopes allow running high frequency drivers to lower frequencies, for better system dispersion, and much better driver protection.

 

Your example is one where b-amping is worthwhile. Effects, be they time based or distortion based, work in the mids and highs, so ideally they go though their own amp and speaker, with the lows remaining unprocessed through their own amp and speaker. Chris Squire more or less invented this technique, using a bass amp for clean lows and a cranked Fender Twin for the distorted mids and highs.

[BassmanPaul]

The acme B2 2x10 is a three way design and I own four. I use two of them in a vertical 4x10 stack and they are wonderful. I can hear them easily and have no desire to migrate to another make/style of cabinet. The way they handle my Low B string has to be experienced!

Edited July 1, 2022 by BassmanPaul

[Jack]

We've just bought two of these at school, they're to be installed as pa in a few weeks but I had to test them first. They do make excellent bass cabs, although there's a little too much low end for my taste. 

 

 

Edited July 2, 2022 by Jack

[Phil Starr]

On 01/07/2022 at 13:58, JPJ said:

So years ago I used to run an SWR Triad which was the sweetest sounding if underpowered cabinet I’ve played through. Then I got my hands on a Schroeder 21012 which whilst probably more a two-way cab was the best single cab room filling solution.

When Alex started Barefaced he placed a lot of store in three-way designs with a dedicated mid-range driver although he’s subsequently moved away from that approach. 
So given the advances in loud speaker design would a modern three-way design be viable as a single cab solution (I’m thinking a 1200W Triad)? 

So you are tri-curious then

 

It's an interesting proposition, there are fundamentally two reasons for splitting the frequency response of any speaker and two reasons why you don't do it if you don't have to. Producing lots of bass needs a big heavy cone both to push lots of air and to lower the resonant frequency of the speaker, high frequency reproducers need to move quickly so lighter is better. The other factor is dispersion, when the speaker diameter becomes larger than the wavelength it starts to beam the sound. The arguments against are cost and the problems associated with the crossovers, they are difficult to design well, almost impossible to make flat around the crossover point with the two drivers interfering with each other and of course also add weight and expense.

 

Of course an electric bass is not a full range instrument, surprisingly there isn't usually much deep bass because of the positioning of the pickups and not much top end because the impedance of the pickups rises with frequency so depending upon the PUP will have little signal above 5-6kHz. The pickup itself is acting as a low pass filter. The tiny horns you see on most bass designs aren't doing much good, a lot of them only give an output above 4kHz especially those horrible piezo tweeters and few of them have a proper crossover. To really usefully smooth out the response and sort out the dispersion problems for bass you really need to crossover below 2,000Hz, the lower the better. This is where the mid range comes in. If you run something between say 500 and 5000Hz then you can use a dedicated bass driver with a really big heavy cone and a horn and driver ideal for the upper frequencies. In fact do you really need a tweeter for bass if 5000Hz is all you need to reach? 

 

There are a few options you could purchase, none of them cheap. The Fearless F115 has a 6" mid and is a nice design. It's just a design though there are some licenced builders  and they come up used occasionally. Genzler sell a 12-3 with an array of mid /top drivers, really just a 2 way design and you could go FRFR with a PA cab like the RCF ART745 which has a massive 4" compression driver crossing over at 500Hz. I suppose you could also look for one of the older 15/6 or 12/6 designs.

 

The reality is that a 3-way design properly done would be way more than twice the price of a single speaker design and more than a 2 way of comparable quality. I've heard the Fearless and it sounds fabulous but it isn't small and it ain't cheap. Good modern design makes a 2 way design possible that will come close to or exceed a 3 way design at a lower price unless you are really prepared to pay silly money. Of course 'better' is also a matter of taste.

[Dan Dare]

An easy way to get what is effectively a 3 way rig is to use your amp with a small main cab ((10+horn or even 8+horn) and add a powered sub. I tried this once, using one of my PA subs and the sound was quite impressive. You retain the character of the sound from the smaller cab and add low end weight via the sub. I wouldn't go to the trouble of taking it on gigs, but it did sound rather good at home.

[fretmeister]

On 01/07/2022 at 15:44, Bill Fitzmaurice said:

Not necessarily. For one thing you'd need at least two premium fifteens to handle even 800w. Passive crossovers can handle that.

The crossover wouldn't likely be below 800Hz, so the size and price of the components wouldn't be a problem.

The amount of power loss with a well designed crossover is insignificant. Bi-amping and tri-amping make sense with large PA systems, but where electric bass cabs are concerned it's an unnecessary level of complexity.

That was probably because they didn't sell well. My preference is for a 2 way, albeit crossing over to the HF element at 2kHz. The typical 2 way bass cab crosses over at 4kHz, resulting in poor off-axis response in the 2kHz to 4kHz octave. There's also no reason for having response above 8kHz. Even slap and pop doesn't go higher than that.

 

 

I've always wondered why some bass cabs go to 20kHz.

 

My Super Twin tops out at 4kHz and that's plenty for anything other than really cutting Marcus Miller top end - which I don't like anyway.

[JPJ]

On 07/07/2022 at 17:59, Phil Starr said:

So you are tri-curious then

 

It's an interesting proposition, there are fundamentally two reasons for splitting the frequency response of any speaker and two reasons why you don't do it if you don't have to. Producing lots of bass needs a big heavy cone both to push lots of air and to lower the resonant frequency of the speaker, high frequency reproducers need to move quickly so lighter is better. The other factor is dispersion, when the speaker diameter becomes larger than the wavelength it starts to beam the sound. The arguments against are cost and the problems associated with the crossovers, they are difficult to design well, almost impossible to make flat around the crossover point with the two drivers interfering with each other and of course also add weight and expense.

 

Of course an electric bass is not a full range instrument, surprisingly there isn't usually much deep bass because of the positioning of the pickups and not much top end because the impedance of the pickups rises with frequency so depending upon the PUP will have little signal above 5-6kHz. The pickup itself is acting as a low pass filter. The tiny horns you see on most bass designs aren't doing much good, a lot of them only give an output above 4kHz especially those horrible piezo tweeters and few of them have a proper crossover. To really usefully smooth out the response and sort out the dispersion problems for bass you really need to crossover below 2,000Hz, the lower the better. This is where the mid range comes in. If you run something between say 500 and 5000Hz then you can use a dedicated bass driver with a really big heavy cone and a horn and driver ideal for the upper frequencies. In fact do you really need a tweeter for bass if 5000Hz is all you need to reach? 

 

There are a few options you could purchase, none of them cheap. The Fearless F115 has a 6" mid and is a nice design. It's just a design though there are some licenced builders  and they come up used occasionally. Genzler sell a 12-3 with an array of mid /top drivers, really just a 2 way design and you could go FRFR with a PA cab like the RCF ART745 which has a massive 4" compression driver crossing over at 500Hz. I suppose you could also look for one of the older 15/6 or 12/6 designs.

 

The reality is that a 3-way design properly done would be way more than twice the price of a single speaker design and more than a 2 way of comparable quality. I've heard the Fearless and it sounds fabulous but it isn't small and it ain't cheap. Good modern design makes a 2 way design possible that will come close to or exceed a 3 way design at a lower price unless you are really prepared to pay silly money. Of course 'better' is also a matter of taste.

Thanks Phil,

 

Very helpful explanation. 

[Bill Fitzmaurice]

On 07/07/2022 at 15:11, fretmeister said:

I've always wondered why some bass cabs go to 20kHz.

That goes to the history of tweeters in bass cabs. They were added to enhance high frequency response at the lowest possible cost. Midrange drivers would have been a better choice, but they were much more expensive, so tweeters were employed instead and the die was cast.

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My Super Twin tops out at 4kHz and that's plenty for anything other than really cutting Marcus Miller top end - which I don't like anyway.

4kHz is fine if your style works with that. I prefer at least 8kHz myself. But even Marcus doesn't need anything above 10kHz.