[mcgsxr]

I have been using my current OB speakers for about 6 years now.

They include 1x Visaton b200 and 1x MAW 12 per baffle.  The MAW 12 is a cast basket woofer, originally for use in cars, but I have repurposed it.  It is DVC, but I have been using only 1 of the VC, effectively doubling the QTS to around 0.54 or so.

My current baffles are large winged 36x42 mdf.





I am thinking about a U shaped bass section, and a mostly flat upper section - if you have seen pics of the Ronin (http://www.6moons.com/audioreviews/nomad/rpd.html) that is the general idea.

I am not a technical guy, I have done all my design to date via trial and error, and playing around. 

My idea is currently:

Total H - 33 inches
Total W - 14.5 inches
Total D - 12.75 inches

Effective width for the b200 section is - 14.5 actual baffle width, plus short wings to help stabilize the top section of 2-3 inches in depth - expecting effective baffle width around 17 inches.

Effective width for the MAW 12 section is - 14.5 actual baffle width, plus wings of 12 inches - expecting effective baffle width of around 36-38 inches.  I will brace this U shape, and am willing to (hold your noses people) box the woofer in ultimately, if that works better.

I run a biamped system - b200's run off an old Magnavox single ended EL84 amp.  Bass driven by a BASH 300 sub amp (http://www.creativesound.ca/details.php?model=BASH300).

I use an active Xover - a Reckhorn B1 (http://www.creativesound.ca/details.php?model=B-1).

I am thinking void free 18mm Baltic Birch for the main baffles, and 3/4 inch mdf for the remaining sections of the build.  I will round over the edges front and back, of the upper section.

The goal is to reduce the overall footprint, and retain great sound!

Thoughts?  Best Xover point to the bass drivers, given my baffle design?

Not bought any wood yet, still using my current baffles until I settle on a design and build them, and will keep the current baffles until satisfied with the new design etc.

Thanks guys!

[Rudolf]

Total H - 33 inches ??
This would put the B 200 at max. 28 inches. Are you sure about that?

Can you tell us the current X-over frequency of your sub-amp and your settings on the B-1?  That would make it easier to understand what your current state is. Are there any passive elements (coils/caps) in the system that have not been mentioned yet? What is the height of the B 200 now?

Rudolf

[mcgsxr]

Good questions, I will do my best.

First of all I misrepresented in error - I have the Reckhorn B1 - http://www.creativesound.ca/details.php?model=F-1M).  Xover set at 100Hz on all 3 dials at present.

My b200 is centered at 28 inches off the floor now.  Perhaps my listening chair (Ikea Poang) is lower than some others?

I am willing to change the H up to 36 but not much more - want a smaller presentation of the speaker this time around.

No passive elements anywhere in the system.

I currently use a pro power amp as my sub amp, but will be moving to the stated BASH300 - I own one in my HT now, and it can be used with no Xover - it has a direct input for use with an HT receiver etc.

[mcgsxr]

I am also considering a local Craigslist buy of a Panny SAXR-50 for use with this system - would allow a simpler system, as the B1 would be out of the loop then.  It would also give me a lot more power, and I could play around with some of the filters that other folks have been using with the b200.

I am just looking to play around with my speakers a bit, not expecting perfection or anything.

Ideas are welcome!

[Rudolf]

The Panny and the F1 both allow to lift the sub crossover up to 150 Hz (the Panny even up to 200 Hz). That would allow to reduce the main baffle width to 14.5 inches. But the narrow baffle will pronounce the 5 dB step at 1000 Hz inherent to the B 200, which has been concealed by the wide baffle. You would probably need a filter to even out that step and loose 5 dB efficiency that way.

The U frame will need a 6 dB low pass filter to EQ its rising response. Do you have the Thiele-Small parameters of the woofer? They would help to find the best size of the U frame.

The unknown influence of the massive insulation batting on the walls will be a limiting factor in any simulations, so you probably need to go by trial and error.

Rudolf

[mcgsxr]

I would be willing to play around with a passive filter on the b200 if I go to the Panny - it has roughly 100wpc, vs the 4-5wpc of my single ended Maggie!

Specs for the MAW 12 are:

Power Handling: 350 watts RMS
Sensitivity: 87db (2.83 volts)
Impedance: 4 + 4 Ohm
Outside Diameter: 31.8cm (12 1/2")
Mounting Diameter: 28.3cm (11 1/8")
Depth: 14cm (5 1/2")
Recommended Box Sizes
Sealed: 29 litres (1 cu. ft.)
Ported: 51 litres (1.8 cu. ft.) 28Hz tuning

T/S Parameters (coils in series)
Fs = 23.3 Hz
Re = 8 Ohms
Qes = 0.30
Qms = 3.03
Qts = 0.27
Mms = 144 grams
Rms = 6.96 kg/s
Cms = 0.324 mm/N
VAS = 76.6 litres
Sd = 408 cm2
Xmax = 13 mm
Cone Diameter = 22.9 cm

[Rudolf]

This is the smallest design I can do:



It is 32 x 14.5 inch with the B 200 at 28 inch. The frequency response does not look too shabby:



But there are some caveats:

The TSP of the MAW 12 lack the BL and Lvc values, resulting in some incertaincy regarding the woofer response. This will not affect the X-over region, but the response below 100 Hz.

The MAW needs to be protected from frequencies below 40 Hz, because excursion will sky rocket below.

The real response of the B 200 is not considered fully considered yet. This will have to be added by a boxsim simulation for the OB.

This simulation is for the MAW with only one voice coil driven, lowering its impedance to 4 Ohm.

Last, but most important: The crossover has to be done with 12 dB filters (probably passive). There is NO way to get a good crossover with the steep 24 dB filters of the F1. So the Reckhorn would be obsolete.

Making the design wider or taller doesn't change things much. But you are free to position the B 200 at any height you wish. In any case the baffle should end just above the driver.

I would like to get your (or others) opinion before starting to find the passive crossover values. What you see in the diagrams are active 12 dB LR filters at 100 Hz (MAW) and 400 Hz (B 200).

Rudolf

[Rudolf]

Found a measured BL value for the MAW 12. Things become more lifelike. This is a realistic response for the U frame:



Don't mind the red curve for the B 200. The passive filter spreadsheet does not allow for correcting different driver efficiencies. Since the U frame response above 100 Hz doesn't differ much from the previous sims, the combined response above 100 Hz will stay roughly as in the earlier simulations.

Rudolf

[mcgsxr]

Cool to see some of the science behind it, and appreciate very much your assistance!

Could I ask what the dimensions of the wings for the U baffle on the MAW 12 are?

From the looks of the passive components, and the associated drop in efficiency for the b200, I will have to change amps...

[Rudolf]

Could I ask what the dimensions of the wings for the U baffle on the MAW 12 are?

The U frame is not just wings. It is an open (to the rear) box with the OB as the front side. Then there are top, bottom and side panels. Measured at the inside the U frame is 16 cm deep. 6.5 inch would be the same. This is implying that you mount the woofer from the front.

Width and height are just large enough to get the driver into the frame.

From the looks of the passive components, and the associated drop in efficiency for the b200, I will have to change amps...

The coil and cap which I mentioned are for the MAW only. Please check out the cost for a 10 mH iron core inductor. They don't come very cheap. http://www.parts-express.com/pe/showdetl.cfm?Partnumber=266-580 Of course you are free to change to a higher quality.



The components for the B 200 still have to follow. But there is a probability that a tube amp will not suffice.

[mcgsxr]

Thanks for the clarification around the depth of the U baffle, I understand it now.

As for the components in the Xover for the woofer, it appears that both the cap and coil may be costly.  Too bad I cannot just use the Xover in the Panny SAXR50, that would save me over $100!

The response curve is decent, floor bounce will always affect OB drivers.

[jonners]

Making the design wider or taller doesn't change things much. But you are free to position the B 200 at any height you wish. In any case the baffle should end just above the driver.
Rudolf

Rudolf -

What is the thinking behind your advice to end the baffle just above the driver, please?

[lowtech]

As for the components in the Xover for the woofer, it appears that both the cap and coil may be costly.  Too bad I cannot just use the Xover in the Panny SAXR50, that would save me over $100!

The proposed XO doesn't include a zobel, so the 12db/octave target will not be realized.  Be prepared to add a couple more passive components to correct for this.  IMO an electronic XO would be a better solution...

[Rudolf]

As for the components in the Xover for the woofer, it appears that both the cap and coil may be costly.  Too bad I cannot just use the Xover in the Panny SAXR50, that would save me over $100!

Any active subwoofer Xover with 12 dB/oct would be helpful indeed. 24 dB/oct is useless. I could not find the filter order in the SAXR50 manual. But I doubt that it is below 18 dB.

If you have to pay more than 50 $ for both woofer Xovers, I would be interested to know where those costs come from.

The components for the B200 Xover would be this:



BTW: At every frequency the efficiency of the B200 in this configuration is up to the efficiency in your old configuration. A problem could only arise from your tube amp having difficulties to drive the changed impedance of the Xover.

[Rudolf]

The proposed XO doesn't include a zobel, so the 12db/octave target will not be realized.  Be prepared to add a couple more passive components to correct for this.

Only for clarification: A zobel (which should not be too costly) could be necessary with a tube amp for the B 200. For any SS amp the design target will be reached without a problem.
 

IMO an electronic XO would be a better solution...

Indeed. But it has to be 12 dB/oct if you are talking about plain Xovers. DSP solutions would be beyond the target of this thread IMHO.

Rudolf

[Rudolf]

What is the thinking behind your advice to end the baffle just above the driver, please?

Equal distances from the driver to the baffle edges enhance the dipole pattern of peaks and dips in the frequency response on axis. You want as much variation in these distances as possible to get a smooth response.
Many people move the driver sideways on the baffle to smooth out the 0° response. But that will result in different radiation patterns to the left and right side. I prefer to compromise the top/bottom pattern instead. It is already spoiled by the speaker sitting on the floor.

Rudolf

[lowtech]

Only for clarification: A zobel (which should not be too costly) could be necessary with a tube amp for the B 200. For any SS amp the design target will be reached without a problem.

I'm not talking about a zobel across both drivers (which would flatten the Z seen by the amplifier).  Rather, I'm referring to a zobel used across the woofer.  If is missing, the woofer's increasing inductance will cause your proposed 2nd order filter to not roll-off at a 12db/octave rate.  (This is basic passive crossover design theory).

DSP solutions would be beyond the target of this thread IMHO.

I mentioned an electronic XO because the OP mentioned that his Panny receiver has one built it.

[jonners]

OK, thanks Rudolf, I see your point. But I would think that since the outer edges of the baffles will be closer to the side walls (mine are only 25cm away), the radiation patterns will be different anyway?

[mcgsxr]

I recall that the Reckhorn F1 might actually be a 12 db/oct Xover? 

I recall there was some discussion about it, and I thought it ended up that model was 12db. 

http://www.audiocircle.com/index.php?topic=41018.0 - here is the thread where someone references that a person measured the unit as 12db/octave.

Reckhorn may have changed the newer models, this one is from 2007.

[Rudolf]

I recall that the Reckhorn F1 might actually be a 12 db/oct Xover?

Yes, you are right. The F1 filters are 12 dB. I have the measurements at hand. Never trust the manufacturers specs.

The new sim for the active Xover:



Note that the lowpass for the MAW 12 is 70 Hz nominally. Looking at the measured filter curves at hand, the frequency control of the F1 should be at the middle position. The effective Xover frequency will be above 300 Hz. You probably will need to split the single subwoofer channel into two separate ones, as suggested by Erling/scorpion.

The 400 Hz Xover for the B200 can not be handled by the F1.

It looks like you just change one problem for another when going active.

BTW: Changing to a lower Xover frequency would need to EQ the low end of the B200. Nothing that I can recommend.

Rudolf