GK 400RB 4 vs 8 Ohm & HPF query ?

sifi2112

sifi2112

Feb 5, 2009
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#1
Hi all,

I have a series II GK 400RB .. will it sound best running at 4 Ohm opposed to 8 ? I’m sure I read somewhere before that the 400RB really ‘shines’ at 4 Ohm !?
And does it have any HPF ? A couple of years ago I asked Jason@GK about the 400-IV I had at that time & he said it did have a HPF but what about the older original 400 ?

Thanks in advance as always my TB friends :)
 
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#2
sifi2112 said:
will it sound best running at 4 Ohm opposed to 8 ?
Click to expand...

Hi sifi2112 :)

The difference between 4 and 8 Ohms,
will be the like the differnce between the two sounds you need for Rock & Roll :D

loud and louder! :laugh: (identical cabs?)

Personally I prefer two 8 Ohm cabs (= 4 Ohm load)
to one 4 Ohm. (mooooove some air! :hyper::hyper::hyper:)

On gigs with FOH and monitors you can leave one of them in the car.

Does your GK have a HPF? I don' t know!

A lot of modern amps have an inbuilt HPF (non adjustable, fixed to 30 - 35 hz)

Maybe ask GK? Call Jason he will know! ;)


so far my 2 cents


may the bass be with you

Wise(b)ass
 
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#3
Thanks Wisebass .. I‘m looking to have a one cab solution & have actually built a 115 cab but not bought the speaker as yet, which will be a FaitalPRO 15PR400, which comes in 4 or 8 Ohms. If I want more volume I’ll probably add a separate poweramp & run two cabs. 400RB is pretty loud as is but I do like to drive it hard to get it to grind/growl lol 4 string standard tuning passive jazz btw
 
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#4
sifi2112 said:
Hi all,

I have a series II GK 400RB .. will it sound best running at 4 Ohm opposed to 8 ? I’m sure I read somewhere before that the 400RB really ‘shines’ at 4 Ohm !?
And does it have any HPF ? A couple of years ago I asked Jason@GK about the 400-IV I had at that time & he said it did have a HPF but what about the older original 400 ?

Thanks in advance as always my TB friends :)
Click to expand...

Does yours have the "String Bass" button? If so, it's a boost of several dB at around 20Hz. Supposedly, it's the "5 string" button. So, if you play 4 string, I would definitely leave that out. It should tighten up your low end a bit.

I don't remember any more details about it. The store I worked in over a decade ago briefly carried GK and I remember reading that in the manual.
 
#5
No 4/5 string button like 400-IV has .. Jason said in 5 string mode it just lets more signal thru, 4 string mode engages HPF. I didn’t have this older version when I asked him.
 
#6
sifi2112 said:
No 4/5 string button like 400-IV has .. Jason said in 5 string mode it just lets more signal thru, 4 string mode engages HPF. I didn’t have this older version when I asked him.
Click to expand...

My understanding is that the older RB models are most similar to running the later models in "4-string mode".

As a reference, Bob Gallien has been quoted as stating that the 800RB has a "bass frequency roll off that begins gradually at around 100 Hz and then really falls off quickly at 40 Hz". The reasoning for this is that modern amplification tech better allows for the lower frequencies that aren't rolled off as much by the 5-string button to be better reproduced.

Given that it appears that the biggest shift took place with the addition of the 5-string button, I'd assume that your earlier 400RB would work similarly to the 800RB.
 
#7
sifi2112 said:
Thanks Wisebass .. I‘m looking to have a one cab solution & have actually built a 115 cab but not bought the speaker as yet, which will be a FaitalPRO 15PR400, which comes in 4 or 8 Ohms. If I want more volume I’ll probably add a separate poweramp & run two cabs. 400RB is pretty loud as is but I do like to drive it hard to get it to grind/growl lol 4 string standard tuning passive jazz btw
Click to expand...

As for the impedance thing, IME it does make a noticeable difference with these RB amps - especially lower powered versions. Not really so much in total volume, but in how much distortion you'll be getting with each at the same volume.

Obviously, if you ever would want to pair it up with another cab, then 8ohm is the obvious choice, but if (like me) you're desiring a one-cab-solution, and plan on going with a single high-performance 115 (also like me), it all comes down to whether you'd like more, or less distortion at any given volume level.

The 400RB is a relatively low powered amp, and I'd expect it to get grindy very fast regardless even at moderate volume levels when paired with a single 15. What are your volume needs like? Music/drummer style?
 
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#8
Thanks Kro ... music style is heavy rock & drummer does hit hard however I’ve used a single Bagend 112 @ 8 Ohm in practice & had to turn down lol, probably not too much low end coming off that 112 tho .. my main tone is grindy, with other amps I’ve used a Darkglass B3K to add grit but kinda don’t need it when cranking the little GK .. so am still thinking 4 Ohm 115 is the way to go :) Mainly stage volume & pa can handle the rest ..

Kro what 115 do you pair it with ?
 
#9
The older 400rb heads don't roll off like the 800rb's. I would assume the 400's are more like being set to 5 string on the later versions.

For cabinets, I run my first series with either one or two series 1 gk neo 112's..... I've even run through my Ampeg 810. It really sounds good with the 112's.
 
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#10
sifi2112 said:
Kro what 115 do you pair it with ?
Click to expand...

I use an 8ohm Greenboy Fearless F115, though I don't personally own a 400RB of any sort. I do, or have owned both versions of the 700 and 1001RBs, which is where I'm basing my assessments as to how the various wattage levels will perform with rigs at different impedance.

I've chosen the power level of the 1001RB-i as my primary amp that I pair with my F115. I like having enough volume on-tap to handle outdoors shows with no support though, my pairing let's me do that for my needs.
 
#15
IME, the 400RB II is pretty effectively HPF'ed, which helps account for its high volume capability - no power wasted on frequencies that can't be reproduced by most cabs, and would otherwise demand a lot of the available power. The 400RB II is HPF'ed higher than the MB500.

I hear no tone difference between 8 and 4 ohm loads. It's slightly louder into a single 4 ohm load, but significantly louder into two 8 ohm cabs in parallel (as expected). You can get some grind at lower volumes into 8 ohms.
 
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#18
I run mine through either an 810 or a Hartke 210 8 ohm. It's plenty loud with the 210.
If you're just using one smallish cab I'd stick with 8 ohm. You can always add another if needed. Not so with 4 ohm, and I don't think the volume difference would be noticeable.
 
#19
AstroSonic said:
Not the 1st and 2nd sen.
Click to expand...

I really think they do...

Filters.jpg
 
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#20
Power
8 ohm 125w
4 ohm 200w

You often have two 8 ohm cabs to get a total of 4 ohms. If you double your speaker area you get 3dB's louder.

Maybe these are the things that make the amp "shine"?

Anywayz it's a fine amp!
 
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