Active Cabinet as Uright Bass amp

[URBass]

Hello All,

Forgive me if this is a lengthy post.

I'm new to this forum and to speaker building and was hoping I might be able to get some advice and opinions on a project I'd like to build.

I play an upright bass that I need to amplify. Most bass amps I've tried have a too much low end on them and don't reproduce the acoustic sound of the bass very well (not to mention that they are expensive). Upright basses put out plenty of low end. I understand that the pick-up/mic makes a big difference (I will be using both a pick-up and small mic). That aside, I thought a powered PA cabinet might be a better choice. I'm not looking for tons of volume, just something for small jazz/acoustic gigs. My other reason for wanting to build my own cabinet is money savings. My design parameters are small size, expandable, light weight and cheap. I'm sure I'm asking too much.

So here's what I thought I'd try. I started by looking for speakers suitable for this. From other forums, I get the impression that 8" or 10" drivers would be preferable to 12" or 15's" for upright bass cabinets. I started looking around and found the Eminence Beta 10CX. With a coaxial tweeter it has a good frequency range in a small package and can handle a fair amount of power. I modeled the speaker in WinISD and felt I could get away with a fairly small cabinet. I should say that I'm not looking for flat bass at the extreme - just tight bass down to as close as the lowest note on my bass as possible - (low E which I think is around 82Hz). Then I found the kit for the Adire HE10.1 - a high efficiency speaker design using the BETA 10CX with their tweeter and crossover. The box design is a very compact size. Next I found a mixer/amplifier from Parts Express (part number 300-797). This is a 150W @8ohms/250W @4ohms amp with two mic pre's, one line input and a slave speaker output. This amp was designed for active speakers so I could bolt to the back of the speaker cabinet. I understand I would probably have to increase the volume of the cabinet to accommodate the volume of the amp. I know this is probably not the greatest amp, but this is a live sound application not meant for my living room. The slave output means I can build a second cabinet for the times when I need a little more volume and take advantage of the 250w/4 Ohm output. Price for the components (excluding the cabinet) would be around $325. Not too bad.

So what do you folks think? Is this a totally insane idea? Will these drivers be appropriate for this type of use? Any input/comments/opions are greatly appreciated.

Thanks,

Chris

[454Casull]

FYI the lowest string on the string bass is roughly 41Hz.

[URBass]

Looks like I was an octave away. Thanks!

[sreten]

Well other than low E on a bass is 41Hz I can't see your problem.

If you can afford a decent standup and decent pickups then
I'd suggest a good standup bass amplifier is not expensive.

You obviously need to avoid electric bass amplifiers.

You should hunt out a valve combo designed for standup,
unfortunately finding one described as such is very difficult.

There's no way you could do better.

Other options are a valve bass head and a separate cabinet.

You really can't go wrong if you know what you are looking for.

In this case a proper compact bass cabinet is difficult to find.

Given the amplifier you describe IMO forget it, go valve.

Of the speakers you describe you should be looking at
a port frequency of ~ 40Hz, anything higher will not do.
Sealed is usually far better than high tuned ports.

Also IMO a coaxial for bass is simply not necessary.

So
1) find a nice valve bass amplifier head.
2) find a cabinet to match or build one.

For compact cabinets you should be looking at
the Eminence Gamma Series as far as I can tell.

50W/70W valve head with a good cabinet should be enough,
but in this case with drivers optimised for medium cabinets.

IMO you need a good 12" or 15", preferably an overdamped 15",
but if you want to do something different a 4x6.5 or 4x8 is not
unreasonable if well chosen, being equivalent to the 12"/15".

sreten.

[454Casull]

I'm not sure how high up the harmonics extend for a string bass, but this 1500Hz should be enough to preserve the integrity of the sound.

http://www.partsexpress.com/pe/pshow...number=295-085

[azira]

I'm with sreten on this. I love DIYing stuff. I like doing my own speakers and amps and furniture and anything even if it ends up costing me more than a commercial set up.

But I play bass and guitar and I know how those things go too. If your goal is to get something together that is custom and learn in the process, by all means DIY it, but if your goal is to get a quality reliable gear on a reasonable budget, I would really suggest that you get a nice acoustic bass amp with a good preamp on it instead of DIY.

For recommendations, Trace Elliot makes some fine acoustic amps. I play electric bass (but would love to play upright). I play on a Fender Bassman which I wouldn't recommend for acoustic but I rather like it or my electric. I think the preamp would make all the difference on your gear. With the budget you quoted, you should be able to get a pretty nice amp that should take in both a mic and line mixable signal which would allow you to blend your pick-up and mic to fit the venue.
--
Danny

[fmeynert]

Acoustic stand up basses and acoustic bass guitars have noticable hamonic content at up to 6khz. A lack of high frequencies will make the bass have a lack of presence, particularly when playing along in a group of other instuments.
Franz

[BAM]

How about the Adire Hurricane cabinet design? That might be the option if you need high SPLs, but also fidelity.

[Eva]

In my little experiencie, the signals you get from a bass guitar through a pickup and a mic doesn't sound well when linearly amplified

The signal from the pickup tends to seriously lack harmonics and sounds 'too much low end/no presence' when linearly amplified. The mic picks up all sorts of stage undesirable noise and is prone to feedback ['can' sound]. Also, the signal from the mic usually cancels the pickup signal in some frequency ranges when they are directly summed, ruining the result even more

Equalising the pickup signal may make things better but the lack of harmonics is allways here and if you add too much MF/HF boost then slapping will hurt your ears

The trick seems to be using an intentionally non-linear preamp capable of distortig the LF signal to generate MF harmonics and enhance presence [that's why people suggest valve preamps/amps that are designed with this fact in mind]

[URBass]

Thanks everybody for your replies.

Azira and sreten, I understand where you are coming from.

I've read about many of the popular amps for upright bass and while many of them seem to be great choices (acoustic image, G&K, Euphonic Audio) , they are all upwards of US$1000 and more. That's about what I paid for my bass with the pick-up. At this point in my musical career (barely above beginner) I don't have the budget for that kind of amp.

One of the amplification systems I've heard great things about is the Schertler Pub 2/280 (http://www.schertlerusa.com/pub.htm). This is a small 2 way active speaker with an 8" woofer. I've read on upright bass forums that this is a very nice sound with this cabinet alone - no subwoofer. In the back of my mind, that's what I was trying to create. Granted, the system I was thinking about was not as high end, but I kind of liked the 'hi-fi' approach rather than a bass amp. I think there is enough sonic information in an upright bass that is above 1500hz to justify a more full range system. It's these harmonics that define the acoustic sound and give the instrument the presence that fmeynert refers to. If I were playing rock-a-billy, I would have no problem going with a more traditional bass amp.

I should probably state that while I have little experience building speakers and I'm a relatively inexperience musician, I have plenty of pro audio experience. I no longer work in the music business but I used to be a recording engineer in Nashville. Hence my preference for a mic'ed sound to capture a truer acoustic sound.

Having said all that, you are all probably correct that I would be better off with a commercial amplifier. The reliability alone would justify that along with the fact that my system is an unknown - it could sound great or it could sound terrible.

Once again thanks for all your replies.

Chris