Speaker decision

[The Admiral]

2 Amps => Kustom B200 100w@8 ohms, and a Little Mark II 300w@8 ohms. The Little Mark II is also rated at 500w@ 4 ohms. The cab into which I want to install new speakers is the original Kustom-style 2x 15" enclosure, the salient point being that although it is a ported cab, the back end is sealed quite heftily. The upshot of that, in turn, is that convenient switching between series and parallel speaker connections won't be possible without modding the cab. And I don't want to do that unless it makes way too much sense to want to do that. My goal is to have 2 speakers in the cab that I can drive with either the Kustom or the Little Mark II head. FWIW, I am not going to lay out all my reasoning for wanting this, there were a lot of factors to consider, just assume that I am sane and playing live shows (i.e. this isn't for at-home). And also that I am wiring in parallel. My thought was to throw in a couple of Eminence Delta 15B's (16 ohm 400w 15", 100 SPL).
Here is my concern/thoughts: If I do that, I can dime my rig on the Kustom head and not even come close to clipping the speakers, BUT - and this is where my knowledge of power matching vs. RMS power vs. SPL actual (not rated, but the actual decibels put out by a given speaker for the actual input wattage, as in, what you hear) is still not enough - looking at it the opposite way, can I expect to get the volume required to fill your average 120-person venue? Will my effects have range or will I always be at that threshold presence of all or nothing? Bottom line: can I play normally?
And, lets say I have reason to throw the Little Mark II on instead, I am pretty sure that as long as I don't dime the rig then I won't blow speakers on the heavy parts, and even if I somehow accidentally dimed the rig, I would have to bang out some heavy notes to damage the speakers.
To summarize... I am thinking yes to the Eminence Delta 15B's with the intent of being able to use either head. Concurrence? Yes? No? …..?

 

[BassmanPaul]

Speakers have to go into an enclosure that supports their TS parameters to work at their best. The likelihood that a particular driver chosen at random will suit your cabinet is small. You will have to measure, carefully, the inside dimensions of your box and input them into a design program to discover likely candidates. I understand that Speaker Hardware will do this for you and provide a recommendation of a suitable driver. If this advice is not followed you could end up with a downgrade from the originals.

 

[abarson]

The Kustom B200 is a ported cabinet. Cabinets cannot be both ported and sealed, only one or the other. As @BassmanPaul pointed out, you cannot stuff random speakers into cabinets and expect useful results.

Powering one speaker in the cabinet from one amp and the other speaker in the same enclosure with the other amp is a guaranteed recipe for failure. The speakers will be fighting each other instead of working in tandem. If this is indeed your plan, then all the talk about series/parallel is gibberish. It doesn't matter what your considerations are. Harsh, I know...

Leave the poor cabinet alone. Or better yet, sell it and get something that will meet your needs.

 

[The Admiral]

The likelihood that a particular driver chosen at random will suit your cabinet is small.

Not to be smarmy (seriously), but no, I don't. I am not attempting to go for the original sound, my research says that is basically impossible short of a small miracle (namely, 1} finding dupes of the original drivers that 2} the current owners are willing to part with, and 3} I can pay). So why bother when I'm not a purist in this instance? Also, rest assured that there is nothing random about this. A significant amount of effort has gone into getting this far, not the least of which has been to talking to both Kustom gearheads/owners and even the friendly folk at Kustom regarding original design intentions (plus their schematics are available online and thanks to the Navy I'm an electronics guy who knows what they mean). I absolutely appreciate your input, but I don't see how it addresses my question. To restate, with those amps powering Eminence Delta 15B's, will I have a use-able volume range on the Kustom, AND how close to or over the edge am I getting to causing bad clipping and/or distortion with the Little Mark II if I am at high vol/gain? Corollary question: If I dimed the Little Mark II, could I outright blow the drivers? And that is a hypothetical, I never dime, I just want to know what my arena looks like.

 

[agedhorse]

Your problem isn't going to be power handling. Your challenge is going to be selecting drivers that have parameters that work well with your cabinet. Power handling is way down the list of concerns.

This has been discussed a lot on TB, there are some good conversations that you might find helpful in making your choices. Nobody can say if those drivers are a good choice or not without knowing the internal volume of the cabinet and the port properties (# of ports, the area of each port and the depth of each port).

 

[Downunderwonder]

It can be hard work convincing the converts from guitar sometimes.

 

[Downunderwonder]

I put some much higher power Eminence tens in my 210 for fun. Ooops. It wheezed like a 50 year old asthmatic.

 

[Wasnex]

Not to be smarmy (seriously), but no, I don't. I am not attempting to go for the original sound, my research says that is basically impossible short of a small miracle (namely, 1} finding dupes of the original drivers that 2} the current owners are willing to part with, and 3} I can pay). So why bother when I'm not a purist in this instance? Also, rest assured that there is nothing random about this. A significant amount of effort has gone into getting this far, not the least of which has been to talking to both Kustom gearheads/owners and even the friendly folk at Kustom regarding original design intentions (plus their schematics are available online and thanks to the Navy I'm an electronics guy who knows what they mean). I absolutely appreciate your input, but I don't see how it addresses my question. To restate, with those amps powering Eminence Delta 15B's, will I have a use-able volume range on the Kustom, AND how close to or over the edge am I getting to causing bad clipping and/or distortion with the Little Mark II if I am at high vol/gain? Corollary question: If I dimed the Little Mark II, could I outright blow the drivers? And that is a hypothetical, I never dime, I just want to know what my arena looks like.

The Delta 15B datasheet says it is more of a mid bass driver. This is supported by the Xmax spec which is only 1.6mm. If you look at the attached cabinet tuning document, you can see how the Delta 15B performs in cabs designed around its T/S parameters. The first cab is a medium vented box of 2.85 cu ft tuned to 67.38hz. This gives a 3dB down point of 64.18hz. The frequency response plot shows a pretty significant peak at about 125hz. Also, note the design is displacement limited to 50 watts, and it should be run with a high pass filter to limit low frequency excursion. Throwing the driver into a random box that is not properly tuned to the driver will likely give worse results. If you're looking to use your cabs for bass, I would suggest looking elsewhere.

The correct way to select a driver is to measure the internal dimensions of your cab, and also the dimensions of the ports. There is free software that this information can be plugged into, along with a drivers T/S parameters. The software allows you to model how the driver will perform in the cab. If you take the cab measurements, some people here may help you model some drivers. Also some speaker shops can take the cab info and tell you which drivers are likely to work best. It may be possible to modify to tuning of the cab slightly by changing the dimensions of the port.

Good luck.

 

[JimChjones]

Not quite clear on what you want to do, but I'd advise against anything smart and ingenious like systems to run two amps into the same cab or switching of different impedances. When such things go wrong, if you are setting up in a rush, you have a helpful assistant who doesn't quite understand instructions, or any number of other scenarios, then they can go horribly and expensively wrong. Be smart, don't be 'smart'!

Two 16 ohm speakers in parallel will give you an 8ohm cab. That's the way to go, you can use that with either (but never both) amps. Next you have the problem of getting it to sound good, which will probably involve a lot of measuring, then altering ports, and also, IME even more important, experimenting with internal damping with wadding and the like. Basically an extensive R&D exercise. Others have said what needs to be said above. If that sounds like fun don't let us dissuade you, but if it sounds like a damn nightmare maybe it will be better to move on and buy a complete system that the makers have done the development for.

 

[The Admiral]

So I was trying to figure out "Where am I going wrong? Why did only one person answer the question that was actually asked?" Then I had it! Thus =====> Since I actually have real gear, why not hypothesize a potential driver for the sake of argument, then hopefully I can understand something better. Bad move on my part, now you want to 'fix' my 'problem.' So, I have no gear. None whatsoever. No gear, no 'situation,' no project. In reality, I do have the gear, and I do need to pop in new drivers on this cab, and my concern beyond that is none of anyone's business. However, I know you mean well, so thank you. FWIW: 9.5" deep x 33" h x 20.75" wide, insulated interior, 2 circular vent tubes 4 3/8" long and 3.5" in diameter, note that many think these Kustom cabs are sealed due to the way the backplanes are attached, they are in fact ported cabs, and I aim to install 2x 15" woofers. Nobody needs to understand what I am trying to accomplish or presume what it is I know and don't know to answer the questions. I know you think you do. You don't. I am just a horribly bad question-asker and don't understand humans at all. So, to restate, hopefully better this time; For a given driver...
- assume correct impedance matching between drivers and amp
- assume the driver has been correctly selected according to cab measurements and whatever else
- consider a mismatch between nominal amp power and driver rated power, as measured in watts
- assume that despite the aforementioned power mismatch, it is not a complete and total mismatch, there *IS* a range on the volume control where the amount of clean sound produced is use-able. Since use-able is difficult to define, think of it as a thing where a note value of some sort (as opposed to 'that noise') can be distinguished through the effect of a stomp box such as a flanger, instead of the signal merely triggering the effect and you hear the effect more than the note.
- Considering decibels produced per watt for a given volume control range (please do not 'teach' me the relationship between wattage and decibels, and if you interpret this as an invitation to do so, you're not paying attention, stop, go back, start reading again) with no farting, clipping, or distortion ===>

Situation A: Amp power is under-matched compared to driver load (e.g. amp is 100W, drivers are rated at 400W)
Situation B: Amp power is over-matched compared to driver load (e.g. amp is 300W, drivers are rated at 700W)

For a given amount of mismatch (situation A has that mismatch at 300W, situation B at 400W) in either direction, at what point do you have complete and total non-useability? Like, in situation A, at what driver power rating will I never, ever get sound from that 100W amp. What driver power rating would give me sound when the amp volume knob is between 5-10. Or, in situation B, for the same 300W head, at what driver power rating would I be unable to even take the volume above 2 without shredding them. Above 5 without distortion.

Hopefully that clarifies.

 

[Element Zero]

You claim what you do with your own gear is nobody’s business, yet post about your business on a free public forum that anyone can look at and reply to...

 

[lz4005]

Situation A: Amp power is under-matched compared to driver load (e.g. amp is 100W, drivers are rated at 400W)
Situation B: Amp power is over-matched compared to driver load (e.g. amp is 300W, drivers are rated at 700W)

For a given amount of mismatch (situation A has that mismatch at 300W, situation B at 400W) in either direction, at what point do you have complete and total non-useability? Like, in situation A, at what driver power rating will I never, ever get sound from that 100W amp. What driver power rating would give me sound when the amp volume knob is between 5-10. Or, in situation B, for the same 300W head, at what driver power rating would I be unable to even take the volume above 2 without shredding them. Above 5 without distortion.

Hopefully that clarifies.

It clarifies any doubts about your level of understanding of how amps and cabs work, certainly.

 

[Downunderwonder]

9.5" deep x 33" h x 20.75" wide, insulated interior, 2 circular vent tubes 4 3/8" long and 3.5" in diameter,

that's the only bit worth reading. If you drop the attitude someone might put it through a calculation for you.

Very small 2x15 cab very short of porting for post 1960"s bass work. You might be better to seal it.

 

[ctmullins]

I’ll take a stab here.

Situation A involves an amp rated lower than your drivers. Result is no driver damage, but possibly not enough SPL to fill the room. Solutions: more of the same drivers (wiring series/parallel to maintain a suitable impedance) or different drivers with a higher sensitivity across the passband of interest.

Situation B (despite what you wrote above, I believe you meant) involves an amp rated higher than your drivers. Result is possible driver damage, but only if you abandon sense and crank it past the point where the drivers are complaining. Below that, you're fine. If you use distortion, it can be difficult for the ears to hear drivers complaining.

Note that a 100W amp and a 300W amp will, most of the time, be putting out the same wattage, since the vast majority of "normal" playing only uses between 20W and 100W. This is a gross generalization, since two players will have different "average SPL" levels; my point is that a 1000W amp only puts out the full 1000W when it's driven at max, with sufficient input signal to reach that level. Most listeners (including your bandmates) will find this objectionable well before you've reached the limits.

To use an automotive analogy - even if your car has 600 horsepower, you don't need to use all of that power to drive to the grocery store. Around town you're only using perhaps 50 horsepower, with the rest "in reserve" should you need it.

Some of your questions I find confusing. "at what driver power rating will I never, ever get sound from that 100W amp?" Well, you won't get sound from the driver (amps don't make noise) when the amp isn't generating enough voltage to move the cone, which is something ridiculously low, like 1W or less. This is regardless of the driver's power rating. "What driver power rating would give me sound when the amp volume knob is between 5-10?" Ignoring the fact that the position of the volume knob tells you nothing about the wattage being delivered, all drivers will produce sound when the amp is running above minimum. You might not like that sound, but the drivers will respond to the voltage that the amplifier is feeding them, and if that happens to be more voltage than they can take, then you risk damaging the drivers. "at what driver power rating would I be unable to even take the volume above 2 without shredding them?" Relatively low - in situation B, the amp has more wattage available than the speakers are rated for, so for your theoretical 300W amp, I'd guess (and it's a rather wild guess) that the driver power rating you posit would be perhaps 50W apiece.

Additionally, driver power ratings refer to their capacity for thermal energy. Nowhere in this discussion have you mentioned the real danger to bassists: mechanical driver damage, which usually happens with significantly less wattage than their thermal rating.

How'd I do?

 

[Wasnex]

This is good info:

9.5" deep x 33" h x 20.75" wide, insulated interior, 2 circular vent tubes 4 3/8" long and 3.5" in diameter, and I aim to install 2x 15" woofers.
​

If the dimensions are exterior, how thick are the panels, so interior dimension can be extrapolated?

FYI. The LittleMark II is rated at 300@ at 8 ohms and 500W 4 ohms. I believe the Kustom B200 is 100W at 4 ohms. Old School: 1960’s Kustom Model 200 “Tuck & Roll” Bass Amplifier

The other bit of data would be whats your budget?

Hopefully with all the data, someone with some modeling skills will chime in and make a recommendation.

Best of both worlds would be to install relatively efficient speakers that can handle the full power of the LittleMark. Your budget and the dimensions of the cab will probably place limits on the possibilities.

 

[Downunderwonder]

This is good info:

9.5" deep x 33" h x 20.75" wide, insulated interior, 2 circular vent tubes 4 3/8" long and 3.5" in diameter, and I aim to install 2x 15" woofers.
​

If the dimensions are exterior, how thick are the panels, so interior dimension can be extrapolated?

FYI. The LittleMark II is rated at 300@ at 8 ohms and 500W 4 ohms. I believe the Kustom B200 is 100W at 4 ohms. Old School: 1960’s Kustom Model 200 “Tuck & Roll” Bass Amplifier

The other bit of data would be whats your budget?

Hopefully with all the data, someone with some modeling skills will chime in and make a recommendation.

Best of both worlds would be to install relatively efficient speakers that can handle the full power of the LittleMark. Your budget and the dimensions of the cab will probably place limits on the possibilities.

Look at the dimensions. It's about half of my 115 but supposed to be 215. Yeah, nah.

 

[Downunderwonder]

Btw, we are all assuming you intend this cabinet have some kind of use for bass guitar since we are in Talkbass Forums > Bass Guitar > Amplifiers forum.

 

[Wasnex]

Look at the dimensions. It's about half of my 115 but supposed to be 215. Yeah, nah.

That's why I wrote "...the dimensions of the cab will probably place limits on the possibilities."

 

[agedhorse]

What's with all the disrespect and attitude lately?

Sorry man, I'm out.

 

[JimmyM]

Deltas and Betas are kind of the go-to for old school cabs such as your Kustom. I've got Deltas in my B-15 cabs and they sing. Mine are the A's, though, not the B's. Still, I think they're your best overall choice out of what's out there.