Bang for the buck 18"/15" subs?

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#4
The bargain you asked for

mr. doom said:
Looking for some better drivers for my BR boxes. Kappalites are on sale for $200 and this 18" is under $100, what other bargains are out there?
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Greetings,
In my opinion based on 39 years experience, this woofer model from PE is about the best bang-for-the buck performer:

Dayton Audio ST385-8 15" Series II Woofer 295-130

One driver per channel adaquate for medium sized rooms, but 2 per channel
in a reaction-canceling enclosure would be almost world class.
 
#5
I have 700 watts to throw at it.

jeeracing said:
I have a Kappalite 3015lf and this is pretty great for music, around 200 liter box
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The 3015LF is my first choice but I am exploring cheaper options.
This will be used for live sound and DJ work so I only need to cover 40-100hz.

I can build another box but already have a 200 liter box and a 175 box with $25 bargain basement 15"s loaded in them (not really subwoofers).

Sensitivity: 98dB (W/M)
Impedance: 8ohm
Re: 7.2ohm
Le: 1.37mH
Frequency response:
32Hz~2KHz
Fs: 32Hz
Qts: 0.41
Qes: 0.475
Qms: 2.9
Vas: 232 liters
Xmax: 3.75mm

About anything will be an improvement.:yes:
 
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#6
Ordered the Kappalite before another round of neo price increases. (I should have bought four back when they were $160)
Not sure what type of problems I will create if I run my pair of low budget boxes @250watts each and the 3015fl @500watts but I will have fun finding out.
 
#8
"Could be a bargain if it has a true 7.5mm of travel. "

Divide that by two, it's a misprint. The catalog description says:

* Sensitivity: 97dB (W/M)
* Impedance: 8ohm
* Re: 7.2ohm
* Le: 1.619mH
* Frequency response: 32Hz~3KHz
* Fs: 32Hz
* Qts: 0.39
* Qes: 0.437
* Qms: 3.3
* Vas: 286 liters
* Xmax: 3.75mm
* Overall frame diameter: 15.28"
* Required cutout: 13.94"
* Mounting depth: 6.30"
 
#10
Isn't anyone going to ask what is the volume of Mr Doom's cabinets and what the port is tuned to? And are you willing to re-tune the port if necessary?

The woofer's potential is irrelevant. All that matters is how it will perform in your cabinets with your crossover. The folks at Madisound and Parts Express and probably other vendors will be able to help you select a woofer that best suits your needs. You would be lucky if the best woofer for your cabinets was also on sale.

Good luck.
 
#12
Builder here, tuning is no problem.

ByronInLawrence said:
Isn't anyone going to ask what is the volume of Mr Doom's cabinets and what the port is tuned to? And are you willing to re-tune the port if necessary?

The woofer's potential is irrelevant. All that matters is how it will perform in your cabinets with your crossover. The folks at Madisound and Parts Express and probably other vendors will be able to help you select a woofer that best suits your needs. You would be lucky if the best woofer for your cabinets was also on sale.

Good luck.
Click to expand...

I am sitting of a few sheets of ply so fabricating a new box is no problem. I have built about forty boxes over the last 20 years and although I love to model and build "really decent" speakers the real satisfaction comes when I can construct something at a lower cost than can be found commercially or on the craigslist. These budget drivers look good on paper and will probably work fine with the 135-175watts I will feed them

It will take two of these budget drivers to compete with my kappalites but I can buy six of these for the price of a premium transducer and move four times the amount of air, for some applications where size is not as important as cost/output this can be valuable information.

When modeling driver/box interaction you learn everything is a trade off and that no "perfect" box exists. Loudspeaker modeling programs help eliminate some of the more egregious mistakes but as a DIY'er you learn through experimentation, and when lucky, through the failures of others. I will let you know if my experiment is complete failure as I have a kitchen table full of speakers and the sawdust is about to fly.
 
#14
"Just got a E-mail from MCM, the datasheet from the manufacturer is correct and website is being updated."

And you believe them?

Another of their PA drivers was recently tested on a Klippel.



MCM 55-2952 Real T/S Parameters measured via Klippel

Electrical Parameters #1
Re 8.26 Ohm electrical voice coil resistance at DC
Le 0.623 mH frequency independent part of voice coil inductance
L2 0.860 mH para-inductance of voice coil
R2 9.38 Ohm electrical resistance due to eddy current losses
Cmes 981.24 µF electrical capacitance representing moving mass
Lces 15.24 mH electrical inductance representing driver compliance
Res 18.62 Ohm resistance due to mechanical losses
fs 41.2 Hz driver resonance frequency

Mechanical Parameters
(using laser)
Mms 58.935 g mechanical mass of driver diaphragm assembly including air load and voice coil
Mmd (Sd) 51.689 g mechanical mass of voice coil and diaphragm without air load
Rms 3.225 kg/s mechanical resistance of total-driver losses
Cms 0.254 mm/N mechanical compliance of driver suspension
Kms 3.94 N/mm mechanical stiffness of driver suspension
Bl 7.75 N/A force factor (Bl product)
Lambda s 0.059 suspension creep factor

Loss factors
Qtp 1.453 total Q-factor considering all losses
Qms 4.726 mechanical Q-factor of driver in free air considering Rms only
Qes 2.097 electrical Q-factor of driver in free air considering Re only
Qts 1.452 total Q-factor considering Re and Rms only

Vas 107.6013 l equivalent air volume of suspension
n0 0.344 % reference efficiency (2 pi-radiation using Re)
Lm 87.56 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)
Lnom Zn missing dB nominal sensitivity (SPL at 1m for 1W @ Zn)

rmse Z 2.30 % root-mean-square fitting error of driver impedance Z(f)
rmse Hx 1.75 % root-mean-square fitting error of transfer function Hx (f)

Series resistor 0.00 Ohm resistance of series resistor
Sd 547.39 cm² diaphragm area



Electrical Parameters #2
Re 8.14 Ohm electrical voice coil resistance at DC
Le 0.592 mH frequency independent part of voice coil inductance
L2 0.966 mH para-inductance of voice coil
R2 10.07 Ohm electrical resistance due to eddy current losses
Cmes 701.90 µF electrical capacitance representing moving mass
Lces 19.51 mH electrical inductance representing driver compliance
Res 24.45 Ohm resistance due to mechanical losses
fs 43.0 Hz driver resonance frequency

Mechanical Parameters
(using laser)
Mms 58.453 g mechanical mass of driver diaphragm assembly including air load and voice coil
Mmd (Sd) 51.207 g mechanical mass of voice coil and diaphragm without air load
Rms 3.407 kg/s mechanical resistance of total-driver losses
Cms 0.234 mm/N mechanical compliance of driver suspension
Kms 4.27 N/mm mechanical stiffness of driver suspension
Bl 9.13 N/A force factor (Bl product)
Lambda s 0.045 suspension creep factor

Loss factors
Qtp 1.159 total Q-factor considering all losses
Qms 4.637 mechanical Q-factor of driver in free air considering Rms only
Qes 1.543 electrical Q-factor of driver in free air considering Re only
Qts 1.158 total Q-factor considering Re and Rms only

Vas 99.3444 l equivalent air volume of suspension
n0 0.492 % reference efficiency (2 pi-radiation using Re)
Lm 89.12 dB characteristic sound pressure level (SPL at 1m for 1W @ Re)
Lnom 89.05 dB nominal sensitivity (SPL at 1m for 1W @ Zn)

rmse Z 2.09 % root-mean-square fitting error of driver impedance Z(f)
rmse Hx 1.89 % root-mean-square fitting error of transfer function Hx (f)

Series resistor 0.00 Ohm resistance of series resistor
Sd 547.39 cm² diaphragm area
*****************************************
MCM claims:

Specifications:

* Sensitivity: 97dB (W/M)
* Impedance: 8ohm
* Re: 7.2ohm
* Le: 1.34mH
* Frequency response: 38Hz~2.5KHz
* Fs: 38Hz
* Qts: 0.34
* Qes: 0.385
* Qms: 2.8
* Vas: 108 liters
* Xmax: 3.75mm

Not even close.

************************************

How do I know that the 7.5mm x-max is fiction on the 55-2963?

Simple, it has a 3" coil and only 67oz of magnet. The Eminence Kappa Pro 15LF-2 has a 3" coil and a 120oz magnet and can only manage 6.7mm x-max. A Kappa Pro 15A has a 3" coil and an 80oz magnet with 3.2mm x-max.

The MCM might be 3.75mm, but the probability of it meeting the other claimed T/S parameters is highly improbable.
 
#16
I will have to test it the old fashioned way.

I will throw it in a box and run some sweeps.

djk said:
"Just got a E-mail from MCM, the datasheet from the manufacturer is correct and website is being updated."

And you believe them?

How do I know that the 7.5mm x-max is fiction on the 55-2963?

Simple, it has a 3" coil and only 67oz of magnet. The Eminence Kappa Pro 15LF-2 has a 3" coil and a 120oz magnet and can only manage 6.7mm x-max. A Kappa Pro 15A has a 3" coil and an 80oz magnet with 3.2mm x-max.

The MCM might be 3.75mm, but the probability of it meeting the other claimed T/S parameters is highly improbable.
Click to expand...

I am not sure to what extent magnet weight and voice coil diameter have to do with voice coil overhang but I can see where your coming from. MCM just gives the specs they get from the manufacturer (whoever that may be) and are not trying to pull a fast one any more than their neighbor Parts Express. The MCM 55-2421 8" driver considered a great budget DIY driver BTW.

For the price of the Kappa pro units I can get four and a half MCM drivers and for my purpose, (low powered bass bins), they should work fine. If they are as functional as the $25 15"s I bought last year I will be happy, they exceeded my low expectations and didn't blow.
The drivers look nice with cast baskets, here it is next to a kappaliteLF that now cost seven times as much as the MCM.

P1080290.JPG
 
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#20
The point is that you had better measure the driver before trying to design a box.

"I am not sure to what extent magnet weight and voice coil diameter have to do with voice coil overhang "

It's about gap volume, flux in the gap, and coil length. The MCM numbers don't add up.
 
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