4 ohm bass cab

[great bleudini]

I have a silverface bassman 100 I might want to start gigging with. I have a 2X15 cab but that thing is a beast to move around. Can you recommend a 4ohm 1X15 cab I could use that won't kill my back? I see the Fender Rumble cabs online but they all look to be 8 ohm. What do you think?

 

[Wasnex]

Does it have to be a 15? Why? Honestly, I don't think you will find a modern 4 ohm 115 unless you have one custom made. Given current design practices, a 4 ohm 115 doesn't make sense for most situations.

I believe Aguilar used to offer a 4 ohm SL115. I couldn't find one in stock anywhere. Not sure if they can still be special ordered. They are not cheap.

It's a good idea to get a 4 ohm cab. AFAIK the amp can probably tolerate an 8 ohm cab, but the power will be reduced and the tubes will wear out faster.

100W is not a lot of power. I suggest getting a 4 ohm cab with the highest sensitivity you can find. Unfortunately, I don't believe Fender publishes Sensitivity ratings for the Rumble cabs.

Speaker Sensitivity is normally expressed as the SPL measured at 1 meter with 1 Watt applied. The spec might look something like this:

Sensitivity 97dB 1W/1m
1W is applied and you measure 97dB at 1 meter.

There is a 3dB rule. Basically, we assume the SPL increase 3dB each time the power is doubled. So getting a cab with a 3dB higher sensitivity rating gives you the same result as doubling the power of your amp.

Calculated SPL for 200W into a speaker rated 97dB 1W/1m = 120dB
Calculated SPL for 100W int a speaker rated 100dB 1W/1m = 120dB

Sensitivity may also be expressed at 2.83V. You might see something like

Sensitivity 100dB 2.83V/1m at 4 ohms

FYI 2.83V at 4ohms is 2 Watts. To convert a Sensitivity of 2.83V at 4 ohms to a 1W rating, simply subtract 3dB.

100dB 2.83V/1m at 4 ohms = 97dB 1W/1m

2.83V at 8 ohms is 1W. So no correction is required.

 

[MIMike]

My Bassman 100 came with a 4x12 cab with the angled baffle. Since it didn’t have any drivers in it, I wanted to make a cab that made me happy with a combination of portability and quality sound. I already had a pair of 8ohm 12” drivers in an old SWR Bigfoot cab. They were non original Eminence Deltalights with neo magnets. I liked the footprint and the look of the original cab, so I contacted Eminence with the width and depth of the Fender cab and asked how tall I needed to make the cab for a pair of those Detalight drivers. I got the pecs and port size I for directly from them and modified my existing cab. The results were fabulous in all three areas; sound, look and portability.

Maybe consider taking what you have and reworking it into a more usable 1x15 (if you can find a 4ohm driver) or 2x12 format.
I agree with Wasne (not just because he has a TON of knowledge) that you should aim for the 4ohm load to get the best out of the head.
I have a bunch of pics of the process, but I have added a couple below.

 

[great bleudini]

Does it have to be a 15? Why? Honestly, I don't think you will find a modern 4 ohm 115 unless you have one custom made. Given current design practices, a 4 ohm 115 doesn't make sense for most situations.

I believe Aguilar used to offer a 4 ohm SL115. I couldn't find one in stock anywhere. Not sure if they can still be special ordered. They are not cheap.

It's a good idea to get a 4 ohm cab. AFAIK the amp can probably tolerate an 8 ohm cab, but the power will be reduced and the tubes will wear out faster.

100W is not a lot of power. I suggest getting a 4 ohm cab with the highest sensitivity you can find. Unfortunately, I don't believe Fender publishes Sensitivity ratings for the Rumble cabs.

Speaker Sensitivity is normally expressed as the SPL measured at 1 meter with 1 Watt applied. The spec might look something like this:

Sensitivity 97dB 1W/1m
1W is applied and you measure 97dB at 1 meter.

There is a 3dB rule. Basically, we assume the SPL increase 3dB each time the power is doubled. So getting a cab with a 3dB higher sensitivity rating gives you the same result as doubling the power of your amp.

Calculated SPL for 200W into a speaker rated 97dB 1W/1m = 120dB
Calculated SPL for 100W int a speaker rated 100dB 1W/1m = 120dB

Sensitivity may also be expressed at 2.83V. You might see something like

Sensitivity 100dB 2.83V/1m at 4 ohms

FYI 2.83V at 4ohms is 2 Watts. To convert a Sensitivity of 2.83V at 4 ohms to a 1W rating, simply subtract 3dB.

100dB 2.83V/1m at 4 ohms = 97dB 1W/1m

2.83V at 8 ohms is 1W. So no correction is required.

Thank you! No, it doesn't have to be a 15. I just like the sound from my 2X15 cab. I also have a Rumble 200 with a 15. I might be better off using the Rumble but I just joined a band (surf) where the aesthetic is vintage Fender tubes. The Rumble more than does the job with any scenario I have been in but I was curious if any options were available to use the Bassman head without killing my back.

 

[gtirard]

Why do you want a 4ohm 1x15"?

For info, GR Bass offers all their cabs in either 8ohm or 4ohm, so you can get a AT115 @4ohm for example, although I don't understand why 4ohm.

The AT115 only weights 10,2 Kg - 22,5 lbs, so you might buy two for a modular rig. Maybe the 8ohm version then, so you get a 4ohm modular 2x15?

 

[gtirard]

Thank you! No, it doesn't have to be a 15. I just like the sound from my 2X15 cab. I also have a Rumble 200 with a 15. I might be better off using the Rumble but I just joined a band (surf) where the aesthetic is vintage Fender tubes. The Rumble more than does the job with any scenario I have been in but I was curious if any options were available to use the Bassman head without killing my back.

The Barefaced Super 24 could be a great choice then.
It's a 2x12 cab, in a 4x10 sized enclosure, compatible with large heads.
Lightweight, loud, full range, 4ohm.

 

[Wasnex]

Thank you! No, it doesn't have to be a 15. I just like the sound from my 2X15 cab. I also have a Rumble 200 with a 15. I might be better off using the Rumble but I just joined a band (surf) where the aesthetic is vintage Fender tubes. The Rumble more than does the job with any scenario I have been in but I was curious if any options were available to use the Bassman head without killing my back.

I suggest setting a budget. to help us give you better recommendations.

It's possible to get a 215 that doesn't break your back. I have a Greenboy Dually loaded with a pair of Faital 15PR400s. Mine is a tilt back design. It has casters on the back, bottom corners. It also has a handle centered on the top, back edge. It's light enough that I can actually lift it with one hand to clear curbs or small sets of stairs. This is a very vintage sounding cab. If it's in your budget and you can find a builder, you could get one made with Fender cosmetics.

Mine looks pretty similar to this one:

Greenboy also designed a Bassic 15 which is half of a Dually and was available in 4 or 8 ohms.

 

[bherman]

From my experience, there's not a huge difference between 4 ohm and 8 ohm cabinets as far as output. I have a pair of 9 ohm 112 cabs (RevSound) that I use with a Mesa head. Most of the time a single cab is fine, when I use two it can get louder but not by that much. Two cabs gives a fuller sound and more dispersion, but one usually does the job. The advantage of going with an 8 ohm is that you can always add a second cab if you find that one isnt enough. FWIW, I had a RevSound 115 cab (25 lbs) and it sounded great by itself. If you can afford it, look beyond Rumble cabs and look at the higher quality ones mentioned so far in this post - Barefaced, Mesa (their Subway 115 is killer) or RevSound. Rumble cabs are ok but not at the same level of quality.

 

[agedhorse]

The Fender power amp applications were pretty liberal in their matching requirements.

Their speakers tended to be in the higher side of nominal impedance which more or less split the difference for matching purposes.

I haven’t seen any issues using an 8 ohm cabinet on this particular amp family, in spite of the math.

 

[jnewmark]

Schroeder makes cabs, including 115's in 4 or 8 ohm, pretty lightweight. I have been using the PL115, 4 ohm, for many years now, with no complaints.

 

[agedhorse]

Another important part of this equation is that a 4 ohm version of a driver generally has a lower sensitivity than the 8 ohm version due to the tradeoffs required by the design parameters of the motor.

Wire gauge increases, number of turns decreases, all the associated parameters are difficult to balance out within a fixed gap dimension.

 

[LHbassist]

I own two 4 ohm Carvin BRX 10.2 cabinets with early Eminence neo drivers. I really like these cabs. Trouble is, most amps I would buy now, are 4 ohm minimum. I have three Carvin BX heads, which will do 2 ohms, and a Genz Benz Shuttle 9.0 head. All are really excellent amps. I also own a bunch of 8 ohm cabs. If I want to use a 600 watt BRX at 4 ohms, I cannot use the Shuttle, as it is 900 watts at 4, and 450 at 8 ohms. I ended up blowing two of the later Carvin Chinese made neo 10's, and that taught me a lesson. I thought I could be 'sensible' with my playing, but you cannot know what is actually going on inside electronic components even being 'careful.'
My point that I'm going to make here- is with most amps and cabs, impedance is really important in that you don't want to 'bust' the operating parameters- like too much power for the drivers, or go below the combined cabinet impedance that an amp can handle. I have really not heard much of a difference between 8 ohm, and 4 ohm cabinets of the same type, perhaps some can.. but for the gigs most of us play, you're likely not going to hear it.

 

[Bodeeni]

If it was me I would try out 2x10 cabs. I have been gigging with an SWR goliath 2x10 for 30 years. I would go for one of the hundreds of lighter one available today. There are some awesome compact and light 2x12s too. I think an 8ohm cab would not give you enough volume

 

[Averell]

If you stick with 15, Eich makes some light ones. And it comes in two different sizes, 4 or 8 ohms, and in two different colors. Less than 15 kg for the small one.

I have a 115L, pretty happy with it.

Eich 115XS | EICH Amplification

www.eich-amps.com

 

[Nebadon2000]

I may be wrong but it seems Bassman 100 is a hundred watts at 8, 4 or 2 ohms

So no advantage using 4 ohm and somewhat a negative based on sensitivity

PS: If you are content with Rumble 200 overall performance and that level of budget the Rumble 1x15 is good choice

There is also Fender Bassman 1X15 but more $ and 54lbs

Yes there are plenty of options for 1x15 Cabs that won't break your back

 

[Wasnex]

it seems Bassman 100 is a hundred watts at 8, 4 or 2 ohms

Bassman 100T is 2,4,8 ohms. From the OM

Vintage Bassman 100 is 4 ohms. From the schematic