Speaker Selection for Detuned Cabinets for Bass

[makinrose]

I've built some detuned cabs for guitar amps and really like them.  I have been planning on eventually building one for bass and made the mistake of reading online to see what other people had used for speakers.  With guitar you can find lots of positive experiences. 

 For bass I mostly found a bunch of people suspicious of the concept but not educated on it nor had they tried it. Bass players seem far more married to traditional cab designs and software modeling of frequency responses than guitarists are.    However, one point came up over and over.  It the concern that the speaker would over extrude unless without the pressure on the cone of sealed back or tuned bass reflex design.  I'm skeptical of this notion since standard bass speakers are not hi-fi acoustics suspension speakers but I'm curious as to whether selection of speaker for a detuned bass cabinet requires any special consideration.  

Is there anything special I should be looking for in bass driver for detuned cab?

[FabTone]

I built a detuned 4x10 and a 1x12 from Kevin's book. Both have Tone Tubby Alnico's (25W) so have to be careful about volume/clipping. I used the 4x10 once on stage with Bass guitar through an AC-15 clone at low volume - it sounded great - no one complained it sounded weak! If I was building one specifically for Bass (or for loud, distorted guitar tones) I'd use speakers that can handle a lot of power.

[K O'Connor]

Hi Guys

For a detuned cabinet, it is best to use drivers with high power ratings even if you only intend to drive the cabinet with a low-watt amp.

There is a fashion with bass-oriented cabinets to use extremely high-power-rated drivers in small boxes and pump in as much power as you can afford and that the drivers will handle. The approach throws away driver efficiency and sometimes tone to merely have high power numbers. The drivers themselves may not be quite as efficient as lower-rated drivers. Does it make any sense at all to have 12" or 15" drivers rated for 1,500W ? I believe the goal is to make the loudest driver possible - highest possible SPL, which is kind of ridiculous. If you need more loudness use more drivers and position them properly. More drivers in the same cabinet is a false economy of materials.

In my detuned 12" cabinet, a very good driver to use for bass is the EV Force-12 rated at 1500Wrms but capable of handling 600W peaks. In the detuned application, effective power handling is reduced but you do not need the power handling here. The driver will reach its maximum SPL at a lower input. You do not have to drag around as much power although the detuned box is quite large already. I've maximised efficiency and tone at the expense of power handling.

As an extreme example, you could have a 300W driver mounted on a flat panel of 4'x8' and achieve maximum SPL with somewhere way less than 25W, if that. The same driver in a box just big enough to hold it will need every watt of its rating to do so and the tone will be less than desirable. Stepping back from the super-tight box to a critically-tuned box may boost a small bit of low-frequency output but again the midrange tones will be sorely lifeless.

Each player should learn how to use their gear within its limits and also how to find the sweet spot for the performance they need. If you change your guitar or your mp or your speakers then you are starting from day-one again, relearning how your new combination of gear interacts. There will always be legions of players who brutalise their equipment, and fortunately for them there is a lot of gear designed just for them. The detuned design is not for them; rather, it is for players more interested in tone.

The EV Force-series are out of production and it is difficult to find samples, although a have a small number of 15s... The next best driver would be the more bland EVM-12L. It is a general purpose high-SPL PA driver rated at 300W continuous. Basically, any high-wattage driver that appeals to you will suffice here. The PA-oriented drivers tend to have masiive magnet structures and good venting for heat management.

You have to remember that you only need enough sound on stage to monitor your own playing. The sound man wants minimal leakage from the stage so he can use the PA to control the house sound more ideally. If you want the band to hear you, then set your cabinet for side-wash rather than back-wash. The days of playing direct-cabinet from the stage are long gone except for the smallest venues, where it makes complete sense. The upshot is that you can use a single driver and have an excess of loudness capability similar to using a quad of drivers. The detuned cabinet will provide a fuller tone when playing quietly than does a sealed box. I believe this makes the detuned approach more versatile inasmuch as you can use the same equipment everywhere you play.

Band sound is always a compromise of egos until those egos sublimate themselves into THE BAND, then there is hope of achieving good tone for everyone at sane loudness levels. I designed and used the detuned cabinets when playing direct off the stage was the norm BUT we kept overall loudness low while dispersing each instrument's sound using multiple cabinets. This meant every instrument could be heard and the band sound was balanced. If only my playing were as good as the tone - hehe. In 1980 I had 300W of drivers fed by a 100W amp that I never turned up past 10-20W. The bass player had about 600W of drivers and a 100W amp that was not straining. In 1974 I used a 2W and then a 10W amp through symmetric cabinets and definitely could disturb the peace.

[makinrose]

Kevin,
Thanks for the answer as always! I really value all the real word experience with speaker cabs. I going to read through that carefully. I'm definitely trying to get my tone at low volumes so I'm sure the detuned cab will work for me.

I actually have an EV force 15 waiting for a cab---I think I'll use that....

[K O'Connor]

Hi Guys

Driver size is influential on the final tone and loudness. 10" drivers for bass are almost always used in multiple as a single unit cannot move too much air, so even were it a 1kW driver it would not be as loud as, say, a 12" driver. For me, 12" is the ideal for bass. It combines good attack with sufficient area to move a lot of air.

I got into 15s for guitar early on, partly from wanting to get the most bang for my cash, and partly from pics of Slade's set up. They had a raunchy tone but used 2x15 faux-horn cabinets for rhythm guitar. Bass used folded horn cabinets and lead guitar was via 2x12 faux-horn cabinets.It looked very cool in 1974. I started with 8" drivers, one per cabinet in a symmetric system, then moved to a single 15" then to symmetric 2x15s, then to symmetric 1x15 detuned boxes.The single-15 was a Radio Shack driver for MI, which quickly got destroyed by my first attempt to build a split-rail PA, and then I got the Force-15s and used only tube amps or AC-coupled amps.

There is a lot of lethargy regarding driver-numbers in cabinets inasmuch as a 2x or 4x is considered "serious" and "necessary" for use on stage. 1x boxes are only used for portability and generally lack good tone. I strongly encourage construction of 1x detuned cabinets as loudness is not an issue. If you need even more SPL, build a second box. Cabinet placement is key to ultimate sound control.

A high-watt 10" driver can be pretty heavy, so even though it is smallish, you may not want two in a detuned box considering the box will be big already. That said, smaller drivers are more useful in multiples in a detuned box than are larger drivers. Also keep in mind the box just has to be rigid not heavy and it should be nonresonant.

Add the vertical disffusor to the cabinet so the sound is more even all the way around the front of the cabinet. This makes the box disappear. Since the thread began with respect to bass guitar, the depth of the cabinet should be 16" NOT 12". The shallow cabinet will be brighter and will lack low-end balance overall.

[makinrose]

You mentioned for bass keeping the depth 16" is important to better sound. that make perfect sense to me.

With guitar or another instrument with less low end say a harmonica can you get away with less depth? is 12" enough for some rigs? I imagine this question also have to do with the types of drivers. Lighter drivers or smaller drivers with less low-end response might not require as much depth?

[K O'Connor]

Hi Guys

The cabinet depth influences bass output more than does the driver capability in a detuned design. The difference between 12" and 16" depth is acoustically quite remarkable. Personally, I use the deeper cabinet for all instruments.

You can always dial bass back in the electronics, but trying to compensate for a lack of cabinet capability will lead to driver damage.

[FabTone]

I tried cheating on the dimensions of a 1x12" detuned cab by slanting the front panel, 13" depth at bottom to 11" at top and it sounded a bit congested. I converted it to a 1x10" baffle and with the bigger internal volume it sounds fine, big and open sounding with plenty of punch. Next time I plan on following the directions!

[makinrose]

I tried cheating on the dimensions of a 1x12" detuned cab by slanting the front panel, 13" depth at bottom to 11" at top and it sounded a bit congested. I converted it to a 1x10" baffle and with the bigger internal volume it sounds fine, big and open sounding with plenty of punch. Next time I plan on following the directions!

Thanks for sharing the experience you had.  I think I'd better keep the cabs I build nice and deep.

[FabTone]

I have a 15" EV Force reconed driver and I want to build a 1x15 detuned cab. Its for a YGL-3a head I recently bought. Question is: If i keep the same internal volume but build it horizontal so the 27.75" Traynor cab alines on top nicely can I mount the driver in the center-top and have a rectangular port along the bottom without compromising the design? It would be app. 27.75' W x 24" H x 16" D. Haven't calculated the port yet but it would be pi x R squared of the usual cutout for a 15" driver.

[K O'Connor]

Hi Guys

Since much of the appeal of the detuned design stems from its "non-critical" requirements, builders have leeway in how they execute the build.

If you start with the single-15 proportion and simply turn it on its side, you have a cabinet wider than the Traynor head: 36 x 22.5 x 16. Keeping the depth the same means we want to retain the baffle area but shrink the width to 27.75; height becomes 29.2. There is lots of vertical space here to have a rectangular opening of approximately 143 sq.in. Alternatively, the driver can be offset and the port be beside it, which might be slightly stronger. If there is a grille covering, the asymmetry would not be noticed.

Have fun

[FabTone]

Thanks Kevin! Math was never my strong subject - and as they say you should measure twice and cut once! 
I like the idea of an offset - I was thinking the port was better near the bottom and the driver nearer the top.