Sub design question

[Shovelhead]

I'm building a pair of compact subs for a classic rock band. The drivers are Eminence Magnum Pro LF 18". The cab will be a bass reflex cab.

 

The objective is to keep the boxes compact enough to haul around in an SUV, along with the rest of a compact sound system. I'll be powering them with 750 watts per cab.

 

The question is:

 

How much lower than 40 hz response would you expect to see in subs for a system like this? I'm using Eminence Design software, and can make them go to 35 hz, but there are compromises in output that I'd have to make at the 40 to 60 hz range. I'm thinking that maybe having more output at the 40hz and above might be more effective for a classic rock band.

 

Any thoughts?

[Craig Vecchione]

For the most part anything below 40Hz is going to waste power, not be very clear, and be likely cause problems with response above 40Hz. Unless you're designing a cabinet for theatrical special effects, don't be too concerned with boosting this part of the curve.

[Shovelhead]

 

Originally posted by Craigv For the most part anything below 40Hz is going to waste power, not be very clear, and be likely cause problems with response above 40Hz. Unless you're designing a cabinet for theatrical special effects, don't be too concerned with boosting this part of the curve.

 

 

Excellent!

 

Thanks.

[VSpaceBoy]

I agree for the most part, but does the bass player play a 5/6 string bass? If so that can reach down to 30hz +/-.

[Steve_B]

By your comments about compromises in output at the 40Hz to 60Hz range I assume that you have been looking at the predicted maximum output. If this is so then you are in a good position to decide on the compromises you are willing to accept.

 

Winisd shows this dip in a 162 litre cabinet tuned to 41Hz. And a 38Hz -3dB point. The dip is not excessive at 3dB. Reducing the the cabinet size to 111 litres and tuning to 52Hz lifts the -3dB point to 47Hz but there is virtually no excursion limitation and between 55Hz and 80Hz there is up to 5dB more output available. However at 40Hz the larger cabinet has 8dB more output.

 

The eminence software might give slightly different results depending on how it calculates things and what assumptions the programmers wrote in to the software, but your figures should be similar to those above.

 

If it were me I

[Craig Vecchione]

 

Originally posted by VSpaceBoy I agree for the most part, but does the bass player play a 5/6 string bass? If so that can reach down to 30hz +/-.

 

 

But most of the actual sound you'll be hearing from that bass will be harmonic content at 60Hz and above. A lot of very well regarded bass cabinets don't have much usable response below 50-60Hz but still sound fine with low-B instruments.

[agedhorse]

Just be careful with the maximum power. 750 watts is the limits of what I would feel comfortable with, assuming a45Hz HPF.

[tlbonehead]

Originally posted by VSpaceBoy I agree for the most part, but does the bass player play a 5/6 string bass? If so that can reach down to 30hz +/-.

Yes,but most of what you want in the mix will be overtones,not the fundamental frequency. Too much super lowend can be hard to deal with from the muddiness it can create. And the kick drum is the thing that benefits most from subs in a small gigging rock band,IMO,and usually their fundamental frequency is in the 50-70hz range. I like my system to be able to achieve flat response down to 40hz but I also drag four sub cabs around that are 36x36x24 and weigh probably 140lbs.

[Shovelhead]

 

Originally posted by Steve_B By your comments about compromises in output at the 40Hz to 60Hz range I assume that you have been looking at the predicted maximum output. If this is so then you are in a good position to decide on the compromises you are willing to accept.   Winisd shows this dip in a 162 litre cabinet tuned to 41Hz. And a 38Hz -3dB point. The dip is not excessive at 3dB. Reducing the the cabinet size to 111 litres and tuning to 52Hz lifts the -3dB point to 47Hz but there is virtually no excursion limitation and between 55Hz and 80Hz there is up to 5dB more output available. However at 40Hz the larger cabinet has 8dB more output.   The eminence software might give slightly different results depending on how it calculates things and what assumptions the programmers wrote in to the software, but your figures should be similar to those above.   If it were me I

[kevinnem]

sounds fairly resonable, .. but I would run teh high pass with a very steap slope.

[Steve_B]

I guess the concept of compact is relative.

 

I have put the figures that you gave into winisd to see if they look anything like the response that you came up with. The grey response is for the details that you gave and apart from the slight peak (less than 3dB)at 50Hz is OK. Lowering the tuning would get rid of this peak and shift the -3dB point down a few HZ. winisd calculates a -3dB point of 38.7Hz but in reality things aren

[Shovelhead]

Steve,

 

Wonderful info - thank you!

 

I might play with my dimensions a bit more, just to fine-tune. I've put together 3 or 4 models to compare, and your invormation will really help me to finalize my plans. Much appreciated!

 

Thank you, thank you.

 

 

 

[kentC]

Remember that build quality plays a large part in achieving the models. Dadoed edges and bracing, you know, all the good stuff.

[Ear Abuser]

You might want to have a look at the Peavey Lowrider 18- it models pretty well in smaller boxes.

[Steve_B]

Remember that build quality plays a large part in achieving the models. Dadoed edges and bracing, you know, all the good stuff.

Whilst I don

[Ear Abuser]

I like to use biscuits joints- The biscuits help align the pieces when it comes time to assemble the cabinet and everything is covered in glue. Also they add a little more strength than a simple butt joint.

 

Lots of glue is the key, though.

[tlbonehead]

Originally posted by kentC Remember that build quality plays a large part in achieving the models. Dadoed edges and bracing, you know, all the good stuff.

Dadoed esges really aren'y a bonus . A butt joint could be just as effective. I use small cleats ion almost all my corners. Plus,if you'd seen Don's guitar cabs,you'd know that you don't have to preach build quality.

[kentC]

No, dados aren't required, and I like biscuit joins as well as splines for smaller boxes. It was more a comment on gereral tightness of the box. I have had boxes I built fall off the top of the stack during a very wild mosh pit and they just kept playing. I tend to over build because I am not gentle to speakers and assume any pro environment is going to be tough on boxes. I assume that most in this forum know how to put together nice boxes.

[Dan Magers]

Someone throw Steve B a biscuit. Always a great post!

[TimmyP]

 

Originally posted by tlbonehead Yes,but most of what you want in the mix will be overtones,not the fundamental frequency. Too much super lowend can be hard to deal with from the muddiness it can create.

 

 

There are very few subs that can actually do any real low end, and I doubt that many of us here have any of them. And few subs can do 40Hz at any usable SPL level without having so much distortion that the harmonics are louder than the fundamental. (Ever notice that those few cabinets that actually spec distortion do so at 1/10 power or less?) Most every system I've heard has a peak somewhere between about 60 and 80. Eq it out and the mixman says "you took all my bottom end!". Turn up the Lows on the channel strip and the mixman says "Oh!".

[Dan Magers]

 

Originally posted by TimmyP There are very few subs that can actually do any real low end, and I doubt that many of us here have any of them. And few subs can do 40Hz at any usable SPL level without having so much distortion that the harmonics are louder than the fundamental. (Ever notice that those few cabinets that actually spec distortion do so at 1/10 power or less?) Most every system I've heard has a peak somewhere between about 60 and 80. Eq it out and the mixman says "you took all my bottom end!". Turn up the Lows on the channel strip and the mixman says "Oh!".

 

 

Four LAB subs here. No problem with the "real low end".

 

Although, My back could use something a bit smaller, lighter.

[agedhorse]

 

Originally posted by TimmyP There are very few subs that can actually do any real low end, and I doubt that many of us here have any of them. And few subs can do 40Hz at any usable SPL level without having so much distortion that the harmonics are louder than the fundamental.

 

Not true. A properly designed sub with a properly sized box using quality (and suitable) drivers can easily achieve a 35Hz -3dB point without anything more than a -3dB reduction in maximum SPL.

 

To do so requires that you know what you are doing and that you use a properly configured HPF.

 

The big problem is that many boxes are undersized to achieve that kind of tuning. The subs I use in my line array system are tuned this way and I do not have any problem with getting a nice deep solid low end.

[Steve_B]

 

Not true. A properly designed sub with a properly sized box using quality (and suitable) drivers can easily achieve a 35Hz -3dB point without anything more than a -3dB reduction in maximum SPL.

I know the get out here is and suitable drivers but here are a few thoughts.

 

Whilst a badly tuned cabinet can sound bad, in my opinion the cabinet tuning only augments the bass output over a narrow frequency bandwidth. The actual output is restricted by the loudspeakers displacement capability which is a function of the diaphragm surface area and the amount that the diaphragm can move, commonly known as xmax.

 

To give an example I

[agedhorse]

That comment may be confusing... yes the subs are from the line array system are adequately sized, not undersized and the box is somewhere around 10-12 cubic ft w/ a single 2241 driver.

 

Your graphs also show exactly WHY i tend to be conservative with judging power claims. Take that same driver and call it a 600 watt RMS driver and I think you would end up with some believable and accurate numbers.

 

Also, for the larger box, try a tuning a little higher and see what happens to your X-max limitation graph.

[Steve_B]

I just wondered if it was a custom line array you might throw some light on the subject not particularly the subs.

 

Back with the subs, I wasn