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Double Bass Speaker Woes

Whit Townsend

Whit Townsend

Jan 24, 2006
435
68
Hartselle Alabama
#1
I guess I should post this in the amp section but since I also play some rockabilly on the upright I thought Id str here. Mods feel free to move it if you want.

My main bass cabs for 6-7 yrs has been two pretty inexpensive 1-12 Hartke HyDrives. The cabs and speakers are very light and rated for 300w RMS each.
About a year ago one of the cabs started distorting and quickly became unusable. Figuring the driver was shot I contacted Hartke and got a replacement speaker which solved the issue.....until now the other cab's speaker has failed and the 1 yr old speaker has started up with some faint buzz, so it wont be long for the world either.
Shame, because these cabs sound really good with my upright and are extremely light and portable. Plus it handles any BG need just fine as well. The combination of the alum cones and tweeter bring out the high end if I need it to hear myself, and also the slap if I want it. But I'm not gonna order two more replacement HyDrives from Hartke that keep frying. I usually run the Carvin head at 300w & 4 ohms total load so theoretically these speakers shouldn't be failing. Its not like the amp is ever cranked past halfway, and thats extremely rare. Usually it runs at 3 1/2-4 on the master vol and if I need more vol I just turn up the preamp gain a little on the Shadow Rockabilly Pro.

I guess I either need to replace the speakers with something more robust and keep the cabs, or just buy something else that can handle the power and headroom I need for the upright to compete with an enthusiastic drummer, and handle the BG in a rock band context. I really like the two 1-12 set up for the versatility and portability. But at this point I just want something that works for the upright and BG in a higher vol situation, isn't a huge hassle to transport, and will hold up.

Any ideas?
 
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#3
AGCurry said:
Do you have a high-pass filter? It might be subsonic impulses which are killing your drivers.
Click to expand...
I always keep everything under 150k completely shelved off with the graphic eq on my head, so Im not so sure thats the prob. I think the Hartkes are just too lightly built and cant fully handle their rated power. Although they did manage to hold up for 3-4 years of regular 2x a month gigging before the first one crapped out.
But this new one hasn't even been on a real gig, its only been used in low to moderate vol practice and its still failing.
 
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#7
So is there a high power 1-12 speaker out there that will work in theses cabs, like from Eminence or similar?
Is my graphic not shelving off enough sub freq?
I really dont wanna spend $1500-2000 if I can help it. The rock band thing is kinda just a sideline I usually play in acoustic or lower vol Americana type situations.
I guess I could just get a used 4-10 that could probably handle it, heck Id love a big tube SVT and 6-10s, but Im an old man, lol.
 
#8
Replacing low-frequency drivers with different ones - successfully - is largely a matter of math, involving the characteristics of both driver and cabinet. If we don't have the numbers, any answer will only be a guess..
There's a very-knowledgeable guy who posts in the BG department here: @agedhorse . Perhaps you could inquire of him.
 
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#9
IMHO you are making a lot of assumptions that may not hold true.

Whit Townsend said:
I usually run the Carvin head at 300w & 4 ohms total load so theoretically these speakers shouldn't be failing.
Click to expand...

AFAIK Hartke does not post mechanical power ratings for their cabs. Unfortunately mechanical power handling is often significantly less than the RMS power rating. The RMS power rating relates to how much power the voice coil(s) can dissipate without overheating. Mechanical power handling relates to how much the drivers move around, which is called cone excursion. At mid range frequencies, excursion is relatively small. As the frequency drops to a lower frequency, excursion tends to increase. If excursion exceeds the driver's Xmax, it degrades the suspension and eventually results in failure.

The Hydrive 112 is a ported cab. Ported cabs have sort of an S-shaped excursion plot.

This excursion plot is for an Eminence 2512 in a 1.5 cu ft box tuned to 55hz. Sorry, I don't have a model of the Hydrive 112.
1727480126581.png

As you notice, excursion decreases from about 95hz to about 55hz. This is dues to the port resonance (Fb = 55hz). This driver has a 250W RMS power rating, but in this cab design it's mechanically limited to 175W and requires a steep HPF set to 40hz. Without the HPF, excursion will exceed Xmax at 40hz with 175W. Xmax = 4.9mm. Excursion also get's fairly close to Xmax around 95hz.

Using an HPF should help protect your drivers from over excursion below Fb. But you may also be pushing them beyond their limit above Fb. Most likely you need twice as many cabs. When you double the cabs and double the power, you get +6dB more headroom.

Whit Townsend said:
Its not like the amp is ever cranked past halfway
Click to expand...
The position of the controls does not tell you how much power you amp is making. Many amps clip before the volume is turned to half way.

Whit Townsend said:
I guess I either need to replace the speakers with something more robust and keep the cabs
Click to expand...
You can't simply buy random drivers with a higher RMS power rating. Drivers and cabs work as a system. So you must select a driver that is compatible with the way the cab is tuned.

If you buy different cabs, consider the cab's sensitivity rating as well as their power rating. Usually sensitivity is expressed as the SPL measured at a distance of 1 meter with 1 Watt applied. So you might see something like 97dB 1W/1m.

Note: Unfortunately, I don't believe Hartke publishes Sensitivity ratings for the Hydrive cabs.

Each time power is doubled the calculated SPL goes up 3dB.
1W = 97dB
2W = 100dB
4W = 103dB
8W = 106dB
etc

At 300W a speaker rated 97dB 1W/1m has a calculated SPL of ~122dB.

When you double the speakers, the sensitivity goes up approximately 3dB. So a pair of 97dB cabs sharing 300W will make ~125dB.

If the power doubles to 600W when you add the second cab, you get another +3dB, so the calculated SPL is ~128dB

Another way to achieve 128dB is to use a cab with a higher sensitivity rating. For example if you find a cab with a 104dB 1W/1m sensitivity rating, the calculated SPL at 300W is ~129dB.
 
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#10
^lThanks, thats way over my head but to sum it up best I can decipher, Im putting too much juice into a too small container so somethings gotta give, and just replacing the speakers is gonna require an engineering degree or at least more brain power than I'm equipped with, lol.

I cant afford a Fearful or some other new $1500-$2000 lightweight high powered cab, so Ive just resigned myself to find a used 4x10 refrigerator locally that can handle it. It wont move that often, and if it does I'll just have to bring a hand truck and suffer for arts sake.
For lower volume situations I still have my old 100w SWR WM12 combo.
 
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#13
Bottom Line Up Front:
With only 300W you need a fairly efficient cab. My personal target is a rig rated for 124dB minimum calculated. So I would want a speaker setup with at least 100db 1W/1m sensitivity. 300W translates into 124.8dB calculated.

A GK Neo 212 IV might do the trick. I believe they can be ordered in 4 or 8 ohms. Power handling is 800W RMS and weigh is 43.4lbs. I don't think they have posted the sensitivity for the Neo IV series, but I believe the previous generation Neo 212 was rated 101dB 1W/1m. It's definitely not a cheap cab though at about $1050 new.


Additional Discussion (possibly TLDR):

This is from the Hydrive OM.
1727580557338.png


-3dB to 35hz is a bit unusual. Compact cabs that are essentially flat to 35hz tend to be pretty inefficient. For example I used to own an Acme Low B2 that was rated -6dB to 31hz. The sensitivity for the Low B2 is only 93dB 1W/1m. The RMS power rating is 350W, but I believe they are mechanically limited to 300W at ~31hz.

Calculated SPL at 350W is 118.4db.
Calculated SPL at 300W is 117.8. At 31hz the response is down -6dB; so 117.8 - 6 = 111.8dB.

I enjoyed playing through my Acme Low B2, but I often wanted more headroom. I suspect I would have been a lot happier with pair and a big power amp.
Calculated SPL for a pair of Low B2s at 700W = ~124.5dB
Calculated SPL at 31hz with 600W = 117.8dB

My last touring rig had a 260W per channel power amp and I typically ran a single Eden D210XLT. The D210XLT is rated 350W and the sensitivity rating is 103dB 1W/1m. Honestly I think the sensitivity rating is a bit optimistic, but it was a very efficient cab. Calculated SPL at 260W is ~127dB. The D210XLT did not play as low as the Low B2, but it was way louder. I don't ever remember pushing the amp to clipping.
 
#14
If you've got the same Shadow set I have (dual pickups, and their preamp) there is an HPF that's variable on it. Try playing a bit with that, but if the drivers are already sounding troubled the damage may be done. Checked the battery lately though?
 
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#15
I haven't been able to get my Shadow preamp to play nice with any of the other preamps I have. I either run it into a small mixer or into an fx return of an amp.
Do you know for certain the problem is the cab(s) and not slamming a (second) preamp with the Shadow's preamp causing gain problems?
 
#16
basscooker said:
I haven't been able to get my Shadow preamp to play nice with any of the other preamps I have. I either run it into a small mixer or into an fx return of an amp.
Do you know for certain the problem is the cab(s) and not slamming a (second) preamp with the Shadow's preamp causing gain problems?
Click to expand...
Ive never had a prob with the Shadow playing nice with other preamps, just have to get the Shadows gain in the right place.
Its not the preamp, The problem appeared when I was playing a passive Jazz, wasnt even using the upright when the buzzing started.
 

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