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[Paul Walters]

Hey all, I decided to ask this question here rather than register on some bass forum to ask. I trust your technical know-how much more than I would theirs.

I'm a live guy though and through and I'm also a drummer; these are useful skills until I have to know something about setting up a bass rig. So here's the question:

I have a Crown XLS 202 sitting around and my bass player is in need of a bigger amp (practice amp is too small and borrowed amp availability is iffy). Would it be possible to use the Crown as the power amp for a bass rig consisting of a 4x10 (or 2x12 or 1x15) cab rated 400w+ at 8 ohms? I haven't seen any bass rigs built this way, but I figure if rackmount guitar rigs can have separate pre and power amps, why not bass? (Do they even make bass preamps, or would we have to get creative with a botique bass DI?)

Thanks for any help you can provide.

[Milt Hathaway]

Geddy Lee was doing this decades ago with an Ashly preamp and BGW power amps. Sansamp makes a couple of nice rack mount bass preamps that will drive a power amp directly, while also giving a nice feed to the PA. Some players use a Pod to drive a power amp.

There may even be a line out on the practice amp that will drive the Crown.

In other words, yes it will work.

[Paul Walters]

Great! I think a Pod would be a good investment for him anyway.

Now physics question: if the major part of our bass sound is low-low end (he plays a 5 string), would a 4x10 or single 15 be better? I'd be inclined to say 15" since the low string is around 35-40Hz, but maybe 10"s can go that low... after all, Mackie made a 4x10" PA sub that was technically audible at 40Hz (-10dB I think).

[Duncan McLennan]

Lots of pro bass rigs are done like this.  It's a great way to get lots of power to a bass cab, and also have increased flexibility with gear choice (choosing separate pre and power).

[Jared Chrysostom]

I've seen this done plenty of times. Just don't try to make the amp/cab do anything crazy.

The Sansamp products mentioned by Milt are good. Also, Ampeg used to make a single-space preamp called the SVP, which seemed to be the preamp section of the rackmount SVT heads (or something similar). Used ones are not too expensive.

[Steve Hurt]

I'm a guitar player, but I have a bass rig (and drums, keys, extra guitar amps, percussion, PA...) around in case people want to play but don't have instruments with them.

The bass rig is:
Ampeg SVP Preamp
QSC PLX1804 amp
Bergantino HT210 (2 x 10) cabinet
EV TL 606 (1 x 15) w/a B & C Driver

No one has complained yet.

A good PA amp that has the power necessary for the job will do fine when paired w/good preamp/speakers/cabinet.

[Paul Walters]

Ok another guitar/bass amplification question: I assume the "rule of thumb" only applies to PA amp to cab matching. What is the proper way to match this Crown to a bass cab? I've been looking at 4x10s that are 400w RMS, and this Crown does 400w @ 8ohms bridged.

[Greg Cameron]

Duncan McLennan wrote on Tue, 30 November 2010 16:44

Lots of pro bass rigs are done like this.  It's a great way to get lots of power to a bass cab, and also have increased flexibility with gear choice (choosing separate pre and power).

My former bass player who co-founded a once well known LA punk band, had a rig in the 80's that evolved into a double 18" cabinet with a 4x12" cabinet on top, all powered by an H&H power amp and driven with a few different preamps models over the years. The 12" drivers were EVM12Ls and the 18s were JBLs, don't recall the model. What I can tell you is that it was WAY too much rig for most gigs. It infuriated many a sound dude. The addition of dbx 160x compressor sure helped tame it but it was still overbearing in smaller rooms. At one point the preamp was a single rack space mono dbx 1/3rd octave EQ that Dave Rat had installed a small preamp circuit in for the bass pickups with a single gain control added to the front. It worked pretty well. Way more tone control then you could shake a stick at

Greg

[Greg Cameron]

Paul Walters wrote on Tue, 30 November 2010 16:44

Now physics question: if the major part of our bass sound is low-low end (he plays a 5 string), would a 4x10 or single 15 be better? I'd be inclined to say 15" since the low string is around 35-40Hz, but maybe 10"s can go that low... after all, Mackie made a 4x10" PA sub that was technically audible at 40Hz (-10dB I think).

The B string on a 5 string bass is 31.5Hz which is lower than most is not all off the shelf bass cabinets can really reproduce. You need real subs for that, and the Mackie S410 doesn't count as a real sub. But there are enough harmonics generated by the B string to be heard though most bass rigs, just not felt much. A good PA system with subs that go down into the 20Hz range will do some serious justice to a bass with the low B string. Personally I love it.

Greg

[Art Welter]

Paul Walters wrote on Tue, 30 November 2010 18:10

Ok another guitar/bass amplification question: I assume the "rule of thumb" only applies to PA amp to cab matching. What is the proper way to match this Crown to a bass cab? I've been looking at 4x10s that are 400w RMS, and this Crown does 400w @ 8ohms bridged... Now physics question: if the major part of our bass sound is low-low end (he plays a 5 string), would a 4x10 or single 15 be better? I'd be inclined to say 15" since the low string is around 35-40Hz, but maybe 10"s can go that low... after all, Mackie made a 4x10" PA sub that was technically audible at 40Hz (-10dB I think)

Your amp has 250 wpc at 2 ohms, 200 at 4 ohms, 145 at 8 ohms.
If the cabinet is 8 ohms, mono it for the most power.

Not much power, so if you want any sound down low, you need something reasonably flat to the low B.
If the response is 10 dB down, 200 watts is of power is needed to equal the level of 20 watts.

Using the proper HP filter for whatever cabinet you decide on is important to keep the bass from flapping the speakers, many cabinets unload with less than 100 watts at 45 Hz and lower.