400W Cabs with 900W amp!

[sunfish]

I'm happy with the sound of my TC RH450 amp going through two stacked Markbass 102 P traveller cabs (both 8 ohms rated 400W). Its a great amp and much more versatile that some reviewers think. I've arrived at the Markbass cabs through the pursuit of being lightweight and affordable. 

Anyway, due to mainly GAS and the constant desire for improvement/change, I've thought about changing to an RH750 head for more headroom to allow a cleaner sound at high volume (playing with loud drummers and at some venues). Then this thinking leads to looking at other amps up to 900W.

I've then got the issue of putting a 900W amp through cabs rated at 400W. I know I'm not really looking to be louder, just have more clarity so won't be driving the cabs hard. But it's still not good practice.

Any one who uses 900W amps - what cabs do  you use? Is it just a no-no to miss match amp and cab output potential.

 

Cheers

 

[Bill Fitzmaurice]

Anywhere between 1/2 and 2x the speaker rating is good for amp power. What manufacturers don't tell you is the mechanical power capacity of cabs, which can be as low as half the thermal rating. Very few have mechanical capacity equal to thermal capacity. To get a meaningful increase in amp headroom requires a 6dB increase. That's four times the power.

[lemmywinks]

The RH series have a baked in sound which seeks to emulate old school valve warmth and has always on compression, if you're after clarity then you probably won't get it with the RH750.

 

The actual power of the RH750 is most likely less than half their stated rating as well, can't remember the exact figure from when they got found out originally but I suspect if you search you'll find it, not that it matters in terms of the sound and volume being enough for you. EDIT - apparently both the RH450 and RH750 are 236w amps.

Edited June 23 by lemmywinks

[sunfish]

Very interesting regarding theRH450. I've never not been loud enough. But I have occasionally struggled to hear myself in a gig with loud drummer and keyboards. I've thought my sound muddier/compressed at higher volumes. So I'm interested in finding more headroom to keep my sound but at higher volumes (if you know what I mean)

Hence looking at the 600 - 900W amps. But was concerned that this means I'll have to also change my cabs.

[lemmywinks]

5 minutes ago, sunfish said:

Very interesting regarding theRH450. I've never not been loud enough. But I have occasionally struggled to hear myself in a gig with loud drummer and keyboards. I've thought my sound muddier/compressed at higher volumes. So I'm interested in finding more headroom to keep my sound but at higher volumes (if you know what I mean)

Hence looking at the 600 - 900W amps. But was concerned that this means I'll have to also change my cabs.

 

I think that's just how those amps sound tbh, they have plenty of volume so loud isn't an issue, there's just lots of APM and digital trickery to get there so the more powerful version would essentially be more of the same. Plenty of people like that baked in sound but plenty of people don't.

 

There's a few micro heads on the market that use the ICEpower 700AS1 modules, Quilter, Markbass etc do them. I've been looking at the Harley Benton Block 800B recently as my rehearsal cab is a bit too power hungry for my little TC BH250. There's also a Genz Benz Shuttle 9.0 in the classifieds:

 

[sunfish]

I had a Shuttle 3.0 a while ago. I used to gaffa tape it onto my cab in case it got pulled off with my cable. Also needed a pair of tweezers to turn the knobs😄. But I could get a good sound out of it. Then had a Mark bass LMii, then an Eden (not great. very clinical) before getting the RH450 which is a great amp. Love the presets. Very useful. And the built in tuner. Love it.  Before all that lot, I used an Ashdown MAG 150W. Which was fab and plenty loud enough even in a blues band. Still got it. One of the old ones Made in England. Maybe I should go back to that!!  😬

[lemmywinks]

17 hours ago, sunfish said:

I had a Shuttle 3.0 a while ago. I used to gaffa tape it onto my cab in case it got pulled off with my cable. Also needed a pair of tweezers to turn the knobs😄. But I could get a good sound out of it. Then had a Mark bass LMii, then an Eden (not great. very clinical) before getting the RH450 which is a great amp. Love the presets. Very useful. And the built in tuner. Love it.  Before all that lot, I used an Ashdown MAG 150W. Which was fab and plenty loud enough even in a blues band. Still got it. One of the old ones Made in England. Maybe I should go back to that!!  😬

 

I tried the Shuttle 3.0 when they sold it with the 1x10 cab with the head in the detachable cage thingy, this was before mini cabs were popular and it made me buy a tiny 1x10 bass rig. I do like all the features on some TC amps, I wish more manufacturers would incorporate that line of thinking into their designs.

 

Ashdown have some clearance Rootmaster 800 heads at the moment, think they're usually around £800:

https://ashdownmusic.com/products/like-new-rm-800-evo-ii-head

Edited June 24 by lemmywinks

[sunfish]

Interesting 

[Phil Starr]

23 hours ago, sunfish said:

Is it just a no-no to miss match amp and cab output potential.

It's fine (and BFM's 2x power is good advice) amps and speakers are rated differently so there is no real equivalence.

 

Expressed simply it works like this (there are all sorts of standards and practical issues and the engineers will be wincing at my simplifications)

 

Speakers are rated by how much heat they can build up before failing. An artificial constant signal is fed into them and the power increased until they fail or reach a particular temp, it's nothing to do with music which has loud and quiet bits but it's easy to measure objectively.

 

Amplifiers are measured effectively by the voltage they can swing before distorting, you connect a load to the amp and look at the waveform on an oscilloscope. Once they reach full power you can see the nice sine wave chopped off at the top and that is the amp's rms limit.

 

So the 900 W amp can swing around 85V but those peaks will only hit the speakers for a few thousandths of a second and it won't heat that quickly and cools down in the quiet bits. However that voltage will move the cones a long way and 85V of frequencies below 100Hz will push most speakers beyond it's limits so how you get on will depend upon how much deep bass is in your signal. Fortunately there isn't much deep bass coming out of your pickups.

[sunfish]

Thanks for that. Great explanation.

[chris_b]

I used an RH750 with 2 Berg 112 cabs, 300 watts each. In spite of the nonsense that surrounded the RH amps they are as loud as their supposed rating.  The RH750 is loud and clear, but even in loud bands I never had it above half on the gain and master. My Bergs never missed a beat and that was with a 5 string bass. IMO your MB 112's would be fine.

[chris_b]

. . . . also the RH750 runs down to 2.67 ohms. That means you can add a third 112 which would give you a better sound and adds an extra 400 watts to the equation.

[jrixn1]

On 23/06/2024 at 11:45, sunfish said:

I'm not really looking to be louder, just have more clarity

 

19 hours ago, sunfish said:

I have occasionally struggled to hear myself in a gig with loud drummer and keyboards. I've thought my sound muddier/compressed at higher volumes.

 

How are you setting your eq?  RH450 is semi-parametric, with unusual defaults (e.g. low shelf at 280Hz).

 

[tauzero]

On 23/06/2024 at 11:45, sunfish said:

Any one who uses 900W amps - what cabs do  you use? Is it just a no-no to miss match amp and cab output potential.

 

BassChat 112 (300W), or my Plenty cab with a Deltalite (250W), or the BC house jam micro cam (100W), all with a Tecamp Puma 900. The throttle volume control goes both ways.

[sunfish]

Yes. All this is making me think about my settings on the RH450. I use mostly Jazz bass bridge pickup and set the amp up with  a lot of bass and slightly less mid bass. Less middle (scooped, I guess) and knock the treble up as I need it . I use the presets to give me a selection of settings. Very useful at a gig. You can alter the freq. range for each knob. So long ago since I set it , I can't remember what I did. I will definitely have a play about at the next opportunity.

 

[sunfish]

8 minutes ago, tauzero said:

 

BassChat 112 (300W), or my Plenty cab with a Deltalite (250W), or the BC house jam micro cam (100W), all with a Tecamp Puma 900. The throttle volume control goes both ways.

I ned to investigate these BC cabs!

[warwickhunt]

I may have said this before but I've ran 2400w power amps into 100w speakers and never come close to destroying the speaker... every amp I've ever used has a marvellous feature for controlling this; a volume or gain control.  

 

Conversely I've ran 60w amps into 1600w speakers and despite dire warnings from others, neither amp or speaker has come to harm.

 

If you use your ears and 'ideally' a HPF (even the bass control on the EQ not being pushed), you shouldn't need to worry about amp or cab ratings... unless you use the type of speakers that they mount in cars; in which case you deserve what you get!      

[Bill Fitzmaurice]

37 minutes ago, warwickhunt said:

Conversely I've ran 60w amps into 1600w speakers and despite dire warnings from others, neither amp or speaker has come to harm.  

+1. That's the myth of underpowering, the notion that clipped signals will kill speakers. If that was the case there could be no such thing as distortion effects. Distortion can toast tweeters, but not because the amp lacks enough power. It's because the abnormally high harmonic content over-powers them.

[agedhorse]

It depends on how good your judgement and common sense is. I see a fair number of speakers damaged from too much power (generally mechanical damage) because of poor judgement, false sense of security regarding power handling capacity, or an unfortunate accident like a plug partially coming out of the bass. 

 

If you are careful it's fine, how careful becomes a judgement issue.

[Alan Wilkes]

There is a thread going around where you can have a ratio of 2 watts amp to 1 watt cab and they 'll be fine. I was also in a live music course in stroud and the guy running it said virtually the same, speaker will put up with a lot more than the specs, meaning i suppose the speaker will be running at full efficiency.

[chris_b]

4 hours ago, Alan Wilkes said:

There is a thread going around where you can have a ratio of 2 watts amp to 1 watt cab and they 'll be fine.

 

So 600 watts into a 300 watt 112 cab? I don't think so.

 

My ROT ratio is 1 amp watt to 2 or more cab watts.

[Bill Fitzmaurice]

4 hours ago, Alan Wilkes said:

There is a thread going around where you can have a ratio of 2 watts amp to 1 watt cab and they 'll be fine.

You can have a ratio of a ten watts amp to one watt cab and they'll be fine, just don't turn the amp up past the point where the speaker distorts.

[tauzero]

56 minutes ago, chris_b said:

 

So 600 watts into a 300 watt 112 cab? I don't think so.

 

My ROT ratio is 1 amp watt to 2 or more cab watts.

 

By that reckoning I think I'd need a stack of all the cabs I've ever owned to cope with my 900W amp, which I happily use with a 100W cab.

[lemmywinks]

It's been about two decades since I last matched amps to cabs based on watts, besides you can blow a driver with an "underpowered" amp if you're an idiot, I have a knacked Deltalite I can stick in the post if you don't believe me. £60 when I bought it and £120 when I looked for a replacement, there was a lot of swearing involved mostly directed at myself.

[Japhet]

I'd recommend using a High Pass Filter. Lower and inaudible frequencies gobble up the amps power and make the drivers in your cab flap about. Using a HPF cuts out those damaging frequencies and allows your amp to only produce the stuff you can actually hear. I've found that using a Micro Thumpinator enables me to get masses of volume out of a little Fender Rumble 100, easily enough for smaller pub gigs without blowing it to bits.