Crate TX30 guitar amp for double bass?

[Rosie C]

I have a need for a small battery powered bass amp to supplement my double bass. I expect this wouldn't work but here goes...

 

I was thinking about making the basschat speaker cab project, but with an extended cabinet for a 12v battery powered amp. Then I got to thinking about the elderly Crate TX30 battery powered busking amp I have. I'm guessing if I just plug a bass in I'll blow the speaker very quickly. I could swap the speaker for a bass one, but is that likely to work? e.g. is the cabinet size different for lower frequencies, or does it need a port?

 

 

[Bill Fitzmaurice]

Try it. The speaker will distort at levels far below what it would take to damage it. If it does turn it down and/or reduce the bass EQ.

[Rosie C]

Thanks Bill, I'll give it a go and report back!

 

[Rosie C]

Reporting back as promised. I tried the Crate amp as it was with my upright and a lifeline pickup. It sounded alright, but was lacking bass / depth. A mandolin-playing friend loves these amps and I didn't want to damage the speaker cone, so I bought a generic bass speaker and swapped it in:

The old speaker was in a machined rebate, and another 1mm diameter and the new speaker wouldn't have fit, but it worked out OK. The new speaker claims a rating of 45W RMS, response 30Hz-4kHz, sensitivity 90dB. I wasn't sure about the dB value, but the price was low enough to try it. 

 

Initial results are good. There's a much deeper tone, though notes on the 'E' string distort unless I play gently. So my next step will be playing with the EQ on the amp, and adding a GEB-7 EQ pedal to my signal.

 

Before:

 

New driver:

 

 

Grille removed, and it turns out there is a port, though I guess not the right size for bass:

 

New speaker fitted:

Edited March 28 by Rosie C

[Matt P]

It might be worth trying a HPF in the signal chain to filter out the very bottom end, should give the amp and speaker a better chance, i'm going to be trying a similar thing using a Trace acoustic cube as a personal monitor for EUB, i've got a HPF and an eq pedal to cut lots of bottom end as i'm mainly using it to keep myself in tune.

 

Matt

[Rosie C]

Thanks Matt, I'll look into that. My own use is playing in a Morris band - outdoors with violin, accordion, etc. 

[Chienmortbb]

You do not say what the new speaker is, but I suspect it will go very low but is very inefficient. The rubberised surround suggests big Xmax, low efficiency. Without modelling it, the results may not be as expected and as experienced designers will tell you, modelling really only gets you 90% of the way there and if the cabinet is tuned incorrectly, that 45 watt rating may be too optimistic.

[Rosie C]

49 minutes ago, Chienmortbb said:

You do not say what the new speaker is, but I suspect it will go very low but is very inefficient. The rubberised surround suggests big Xmax, low efficiency. Without modelling it, the results may not be as expected and as experienced designers will tell you, modelling really only gets you 90% of the way there and if the cabinet is tuned incorrectly, that 45 watt rating may be too optimistic.

 

I don't know much about the speaker. I originally ordered one from Blue Aran, but after a few days it was marked unavailable and I got a refund. I struggled to find much in the way of 8" bass speakers, and ended up getting this one which is unbranded: https://www.ebay.co.uk/itm/355768432655  

I'm sure you're right about the power rating - and the amp is only rated at 30W. Hopefully it will do though - if this doesn't work I can put the original speaker back in and sell it on and use the proceeds for a proper battery bass amp. 

 

 

 

 

[Bill Fitzmaurice]

That's a hi-fi speaker. The main drawback is it has lower sensitivity than a pro-sound speaker, so it won't go as loud with the same amp.

[-asdfgh2-]

On 28/03/2025 at 13:35, Rosie C said:

Reporting back as promised. I tried the Crate amp as it was with my upright and a lifeline pickup. It sounded alright, but was lacking bass / depth. A mandolin-playing friend loves these amps and I didn't want to damage the speaker cone, so I bought a generic bass speaker and swapped it in:

The old speaker was in a machined rebate, and another 1mm diameter and the new speaker wouldn't have fit, but it worked out OK. The new speaker claims a rating of 45W RMS, response 30Hz-4kHz, sensitivity 90dB. I wasn't sure about the dB value, but the price was low enough to try it. 

 

Initial results are good. There's a much deeper tone, though notes on the 'E' string distort unless I play gently. So my next step will be playing with the EQ on the amp, and adding a GEB-7 EQ pedal to my signal.

 

Before:

 

New driver:

 

 

Grille removed, and it turns out there is a port, though I guess not the right size for bass:

 

New speaker fitted:

90dB sensitivity is really low. I'd look for something with higher sensitivity, although that's.a pretty tiny box so tuning it might be tricky in a ported enclosure. Maybe a high pass filter?

Edited 15 hours ago by -asdfgh2-

[Paddy Morris]

I would be tempted to take the electronics and chassis of the Crate and mount it in a different, maybe larger enclosure.  Or have you considered a PJB double-four?  I have used that with upright bass for busking type gigs, and you can run them from a powertool battery.

[Rosie C]

I did have a PJ double-four for a while, but the DI was noisy and I managed to blow the pre-amp, so while they do have a good reputation, I'd not have another one.

 

I was going to post an update as it was used for the first time properly on Thursday - our local British Legion hall for a Morris dance practice. It was loud enough, and while not as deep as tone as I'd like, it was acceptable. 

 

However, it was strangely directional - from where the dancers were it was very loud, but to the sides the other band members could barely hear it. I've not experienced that before with bass. Next rehearsal I'll take my Crush 25B instead and see how it compares.

 

A new enclosure is an idea. I started this project thinking about building the basschat cabinet project, but with an additional compartment for my amp. Seeing how I unwittingly bought a hi-fi woofer instead of a bass guitar speaker, it would be an opportunity to move up to a 10" driver. Also moving away from a heavy lead acid battery to power tool is a great idea - I already use a Screwfix Erbauer battery for my pedal board...  

 

1 hour ago, -asdfgh2- said:

90dB sensitivity is really low. I'd look for something with higher sensitivity, although that's.a pretty tiny box so tuning it might be tricky in a ported enclosure. Maybe a high pass filter?

 

Thanks for the comments, which broadly are the same as @Paddy Morris  I feel a woodwork project coming on!