Hoffman Amplifiers Tube Amplifier Forum

Other Stuff => Cabinets-Speakers => Topic started by: kagliostro on June 20, 2014, 01:49:59 pm

Title: Which 15" Speaker for a Bass Pneumatic Cab ?
Post by: kagliostro on June 20, 2014, 01:49:59 pm

Do you have suggestions for a 15" Speaker to use for Bass in a Pneumatic Cab ?


Thanks


K

Title: Re: Which 15" Speaker for a Bass Pneumatic Cab ?
Post by: thermion on June 20, 2014, 03:39:07 pm

I searched for the term (pneumatic bass cabinet) and found almost nothing...how is this design different from a typical/ ported bass cabinet?

Title: Re: Which 15" Speaker for a Bass Pneumatic Cab ?
Post by: kagliostro on June 20, 2014, 05:58:01 pm

Pneumatic is the literal translation of Pneumatica in italy with Sospensione Pneumatica

we mean a completely closed cab, no Bass Reflex or other holes

May be in english pneumatic isn't the right word  ....... ???

K

Title: Re: Which 15" Speaker for a Bass Pneumatic Cab ?
Post by: thermion on June 23, 2014, 01:04:41 pm

From your explanation I would consider pneumatic to mean sealed. I looked and found this advice from Anthony "Big Tony" Lucas with Eminence:

Quote

A parameter called EBP (calculated by dividing FS by Qes) is often used to determine if a speaker is best suited for a sealed or ported enclosure. An EBP close to 100 usually indicates a speaker is best suited for a ported enclosure. An EBP closer to 50 usually indicates a speaker is best suited for a sealed enclosure. A speaker with an EBP 50-100 might work well in both types of enclosures. This is purely a general rule of thumb. Many great designs violate this.

Title: Re: Which 15" Speaker for a Bass Pneumatic Cab ?
Post by: thermion on June 24, 2014, 04:11:03 pm

Dr. Gonzo, please pardon my brevity.

EBP = efficiency bandwidth product
Qes = electrical Q factor at FS
Fs = resonant frequency of the driver, also listed as Fo on some literature.
Fs and Qes are Thiele-Small parameters and hopefully can be obtained from the manufacturer, for example here:
http://assets.peavey.com/literature/manuals/lowrider_specs.pdf (http://assets.peavey.com/literature/manuals/lowrider_specs.pdf)
for a peavey low rider 15 sub.
So for the PV speaker, EBP = Fs/Qes = 33.9/0.364 = ~93. From Big Tony's advice, the low rider 15 should be comfortable in a ported enclosure. These low rider speakers are heavy, can cause structural damage to your house and make you lose control of your bowels...they don't need the cushioning effect of a sealed (pneumatic) enclosure to keep them from destroying themselves. They are also about $200 apiece.
Now let's contrast the PV with these speakers:
http://www.mcmelectronics.com/product/55-2974?scode=GS401&catargetid=530004080000290736&cadevice=c&gclid=CKa254ezk78CFabm7AodxzkA7Q (http://www.mcmelectronics.com/product/55-2974?scode=GS401&catargetid=530004080000290736&cadevice=c&gclid=CKa254ezk78CFabm7AodxzkA7Q)
For the MCM offering, Fs/Qes = 32.5/0.5591 = ~58. These speakers would benefit from the pneumatic cushioning of a sealed box to extend their life, and are about 10% of the cost of the PV.

So Franco, it looks like you can get away with some pretty affordable 15" speakers if you are putting them into a pneumatic/ sealed box. Please do not interpret this as an endorsement of MCM, I have never used those. I do have experience with the PV in the afore mentioned ported enclosures.

Title: Re: Which 15" Speaker for a Bass Pneumatic Cab ?
Post by: kagliostro on June 25, 2014, 01:31:30 am

Thanks for the info and councils


K