cab design for 10" markbass drivers (B&C)

globert

globert

Mar 15, 2017
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New Zealand
#1
Hi. My first post. Hoping someone can help with my speaker design dilema:

I have aquired 2 new 10" markbass drivers. They are B&C 10/134B-16, a 16ohm neo design. I can make a cab but do not have theile small parameters.

1. speaker data would be fab. Some threads sugest the markbass driver is the same as the B&C 10HPL64 (in my case the 10HPL64-16). But the 10HPL64 fs=61Hz. And the markbass specs for their 2x10 cabs are 40Hz or 45Hz. So I'm not so sure it is the same.

2. If someone can pass on the port length of a markbass 102HF enclosure, I could replicate that cab.

3. I'd ideally like to make two 1 x 10" cabs - but will go 2x10 if that guarantees a result (e.g. a 102HF replica). Any insights on what dimensions to use (cab and port) to get to 40Hz? I've tried winisd but it does not let my load my own data; other softawre did not let me tune the port and see the result (this appraoch assumes the 10HPL64 is close).

Thanks :)

By the way, I've read lots of posts here to help chose pickups and a head - thanks for sharing!
 
#2
First make a couple assumptions...then reverse engineer the cab to find out the volume they are using per driver.

the assumptions are that usually typical manufactures use 1 cubic feet per driver for 10" speakers.
majority of that decision is for power handling so they keep it on the small side. trade off is the typical bass bump or high ripple response on the low end which yeilds the typical " bloom" with some notes
although the ripple response of Q of 10" speakers usually would want 1.3 to 1.6 to get a better response and would flatten out that ripple.

One thing markbass has done which is impressive, Is they build rather large deep cabinets and that is going to give better performance and a nice flat ripple response.

That factory driver is probably a cross between 2 different drivers and since the factory is using a very nice lower tuning. thumbs up to markbass again for producing a reflex/ported 10" cabinet that isnt tuned to annoying high tunings like 50 or 60hz....blahhh

after modeling alot of 10" speakers for years now you find many similarity's with ripple response depending on the Fs of the speaker and its bandwith.

for the most part 10" speakers with higher sensitivity and average Fs of 49/54hz tend to like smaller boxes and require higher tuning. usually as i mentioned .8 to 1 cubic works well with these drivers. sealed or ported will use these volumes and average tuning is 50hz which is close to the higher Fs of those speakers

Some drivers will trade sensitivity and have longer gaps in the 3.5 to 4.5 mm range and will also incorporate a overall lower Fs which can be impressive for a 10" speaker. Fs can be as low as 33 to 42hz. and in general these speakers will also be looking for a larger box to get ideal ripple response. in the range of 1.3 to 1.8 cubic feet per driver. again ported or sealed the volume would be on the larger side and likewise with a lower Fs tuning would be lower towards 40/45hz

Judging from the large markbass cabinet and its lower tuning its probably using a driver similar to the second description i mentioned . designed for bass obviously with a longer gap and lower Fs. Im sure some experts will scream bloody murder and say this is a krapshoot and all is lost and nothing can be done without Ts parameters blah blah blah.

when in fact its rather simple to reverse engineeer the cabinet and find out what volume they are using for these drivers. and likewise id advice using their approach and designing a rather deep cabinet and using the well choosen lower tuning of 40hz. since this factory driver has a lower Fs than the average 50hz 10" driver. and you will have a more than fine reflex cabinet.

Likewise since winisd has parameter error checking system its not letting you save the driver info you have entered. its a annoyance as much as a benefit. so would like to point you in the right way to juggle parameters so winisd will let you save the driver info your entering.
if winisd gets a parameter which is not possible it will give you a error warning. and sometimes your info is correct but its not seeing a value to the decimal point it wants to see. with small signal and large signal parameters because of their relation you can have missing parameters and with the parameters you have you can calculate the missing parameters. so winisd will calculate these for you. this is related to your problem cause what you can do. is erase a parameter you have entered and let winisd auto calculate it for you. then you make sure it has auto calculated the parameter close to the value you already have. but in this case it has auto calculated to the value it wants to see and then will let you save the driver.
 
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#3
BB, fab info - thanks for passing on your experiance.

By my rough calc, the markbass 102hp is about 1.8 cu.ft per driver.
Assuming fs=40ish sounds like a good plan. I could use this to design a port that is in the ballpark and tune by ear.

For info, I notice the smaller markbass cab is 45Hz; the larger 40Hz.

Thanks for the winisd tips. My problem was not being able to enter any custom data at all. www.ajdesigner.com/speaker/ajvented.php works for the basics and I'll try that.

Any thoughts on tuning ports by ear?

Thanks!
 
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#4
and since im bored as heck here is my best reverse engineering on the 102HF

lets start with the outer dimensions 23.4 x 21.6 x 18.9
looks like they are using 3/4 inch construction so we have to subtract .75 for all outer dimensions and the rear panel and the baffle.
after doing those subtractions the volume is

4.43 cubic feet

not done yet the baffle is setback into the cabinet for grill spacing so we need to subtract that, i dont have the cab to measure that but typical setback is either 1inch or 1.5inch so we need to subtract that from our volume.

if 1inch = 4.18 cubic feet
if 1.5 inch = 4.05 cubic feet

not done yet lol. ther is a shelf port taking up volume 23.5 minus the 2x .75 sides. 22 inch wide shelf. looks like a 1 inch actual opening. then a second .75 inch piece is needed to make the actual shelf. so far were looking at 22x1.75
now the depth of the actual shelf which i cant measure. but a typical 1" x 22" port would have to be about 5 to 7 inches lone to get 40 to 45Hz

so 22 x 1.75 x 5 = .11 cubic feet
22 x 1.75 x 7 = .15 cubic feet

so with 2 baffle guesses and 2 port volume guesses you get.

4.05 - .15 = 3.9 cubic feet
4.05 - .11 = 3.94 cubic feet

4.18 - .15 = 4.03 cubic feet
4.18 - .11 = 4.07 cubic feet

so your looking at about 3.9 to 4.07 cubic feet

lets give ourselves a 15% error factor

so .585 or .619 or something idk hate math but whatever
lets just go for .6 error factor

3.9= 3.3
4.07= 3.4

so yeah 3.9 to 4.07 cubic feet with error factor averages out to 3.3 / 3.4 cubic feet

or 1.6 to 1.95ish cubic feet per driver

i would shoot for 1.6 to 1.8 per driver basically the larger size i mentioned above.

and yes depending on the volume of port, volume of driver and volume of bracing your basically got to make a bigger box to accommodate all those extra things. so 3.2 cubic to 3.6 plus extra .5 to .7 depends again if your using shelf or multiple round ports
 
#5
tune it to 40 hz its not really by ear its where the reflex starts to reduce cone movement so just go as low as you can go.
at Fb or tune frequency there is no cone movement the port takes over. so your looking to try and produce as much bandwidth as possibly by actual cone movement. the mark bass driver for all we know goes lower than 40 hz so we could tune lower. but its risky so be good idea to stay as low as possible assuming the Fs of that speaker is probably 34 to 46hz so shoot in the middle or basically feel safe using the lowest markbass tuning
 
#6
in winisd to calculate your port lengths you dont need a specific driver. the volume of the box and the area of port opening and length is what determines the actual Fb of the box. basically the box size and port size determines the tuning. usually you would use the actual model of the driver to see the effects it has on that specific driver. but once you have a design volume winisd will calculate lets say 4x3" round ports or one or even 2 slot ports. its up to you. i like ported designs with equal pressure so i would personally use 2 slot ports on both sides of the driver or 4 equally spaced round tube ports, or one round port per corner with a total of 4 round tubes. whatever size fits. you might have to use say 4x 2.5 inch round tubes to fit within whatever dimensions you use. but for the most part your trying to get17 to 20 m/s port velocity at full power where the speaker hits xmax or 10% distortion. assuming your using a 4mm ish driver in 1,8 cubic feet. your looking at 70 to 90 watts per driver or 140 to 180 for a pair system power for 10% distortion. so using generic driver try to get 17 to 20 m/s port velocity with 180 watts as your power applied and view the port velocity screen. usually using 4x round tubes will yield the lowest velocity.

i already know 4x 3" round tubes in 3.8 cubic feet will get 18 to 19 m/s with 180 watts. with slot port or smaller ports youll probably hit 22 to 28 which is higher and ok..ish i wouldnt wanna go higher than 30 m/s
 
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#7
Fab & nice worked example.

i will try tuning to 40Hz.

I will make two single 10" cabs. The first will be a prototype. I'll start with 1.8cu.ft and a sloted port at 1" x 22" = in the range you estimated at 5.75" port length (using port length calc at Port Length Calculator).

BTW, I had downloaded winisd beta - winisd pro (also free) works fine for me! :)
 
#8
Thanks - I missed the post about multiple ports. I'll run with multiples ...

... two ports on a 1 x 10", or in your experiance, stick with 4 ports? I was thinking a slot would double as extra bracing. I guess I can add bracing whether tubes or slots.

Thanks. I'm off to bed!
 
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#9
yes very true the slot port does provide extra bracing. its just my opinion but yes equal pressure can help so 2 slot ports on either side would work or just a single its up to you and the limitations of physics lol cause i dont think a 1x22 slot port in 1,8 cubic feet would work it would have to be very long to work. i would check your numbers i think a single slot that size would work in 3.6 cubic volume to be depending on end/flare correction it would be yes 5.75 to 5.90 in length. but in 1.8 cubic i think the slot would have to be much much longer. ill check. later cause yes i have to go to sleep/ work too lol
 
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#12
I've built a cab. First I ran it as a sealed box/no ports - I thought it was even across all notes on 4 string bass. After adding ports ... a MUCH fuller sound - feel emersed in bass but still reasonably clear. I still need to add bracing and more fill.

For anyone interested, here are the dimensions I used (I'm converting from metric, so excuse the odd dimensions):
- 13.2W x 18.7H x 18.8D (336W x 475H x 478D)
- 1" battens on all edges (24mm x 24mm)
- almost 3/4" thick mdf panels (multi veneer birch too expensive) (18mm)
- 2 x pvc tube ports: internal diamter 2.5" ; 7.1" long (63mm x 180mm)
- screwed and glued everything except the back panel
- 1.81 cu.ft (51.3 litres)

Very happy. I have an old high quality rcf n281 compresion driver and ~ 8" x 4" rectangular flared horn that sits on top of the cab. Crossed over with a first order filter at 3.3kHz filter at the moment. I will make it a 2nd or 3rd order crossover. I chose the crossover point because markbass use 3.5kHz.

I'll report back with a photo and update when I've added bracing in the weekend.

Thanks heaps BB for your help.
 
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#13
For info and help problem solving:

I made the 1x10 cab and I thought it sounded very clear and controlled and full for home use, except for a slight hump at and slight rolling off below D2 / C#2 (i.e. 73 to 69 Hz).

Then scrapped it and made a 2 x10 using the B&C drivers - and it sounds bad.
(My speaker was 16 ohms and I had ordered a 8/4 ohm only tube amp, so i decided to bite the bullet and make a 2x10 cab to get 8 ohm. I followed the Markbass hp102 dimensions. I did not know the port length so used winisd to tune).

The 2x10 sounded more pronounced at D2/C#2. And rolled off below this point more dramatically than for the 1x10 - not full at all. And bloated / woolly
To get a feel for impedance, I tried something new for me, and measured the peak voltage drop across serries resistor while changing frequency: Peaks were at approx 71Hz and about 33Hz. I changed the port length from about 160mm to 260mm and 71Hz peak stayed the same; lower peak moved about 3Hz.

The cab is well cross- braced with 12 1/2"x12" timber braces. 1"polyseter is on 1/2 of internal surfaces and away from the port.

- I'm wondering what to try next. If any ideas I'd be greatful - Worse comes to it, I'll by an already made cab. It may be that the speakers fs is too high - but 70Hz seems too high.


Thanks :)
 
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