big bandpass The fatboy

[SimontY]

Excellent, I bet he's very happy listening to them!

 

[TMHutson]

After reading this thread, I couldn't help but compare these to the old RP400 speakers (Yes, the RP400 are monsters).
After seeing this thread, I am almost considering the undertaking with bandpass. Good info, thanks.
Todd

Magnat Sound-Studio 1979 - 1990

 

[Helmuth]

After reading this thread, I couldn't help but compare these to the old RP400 speakers (Yes, the RP400 are monsters).
After seeing this thread, I am almost considering the undertaking with bandpass. Good info, thanks.
Todd

Magnat Sound-Studio 1979 - 1990

I made a virtual new design FATBOY MKII for people how are interested. It is also good to understand the background of design choices.

The part that is interesting do do well is the filtering of the sub-bas to the mid bas. I use winisd this helps to show the group-delay of both drivers also with filter. So we do not suffer losses by phase problems.

 

[Helmuth]

Virtulal design fatboyII

The design.

The old design was 156 litre the MK2 is 182litre to be really Fat.

 

[Helmuth]

The part I use are high quality and low price.

A big 12" peerles subwoofer with high x-max of peerless with sturdy aluframe.

A peerless polypropylene Highly damped cone almost no breakup at high frequency and sturdy aluframe.

And the Monacor DT300 a very good performing 28mm dome tweeter with back chamber at bottom a price.

partlist

 

[Helmuth]

Virtulal design fatboyII

The fatboy displays what is needed in a speaker design small bas-mid and a big subwoofer because there the most energy needed. With a big volume it is possible to create good sub-bas at normal efficiency.

Here the simulation of the bas to mid. Inclusive filter so that the group-delay of woofer and mid-bas is the same.

The filter is at two different point because the impedance rise of the drivers compensate impedance faults caused by this configuration.

 

[Helmuth]

Spl at 100W 110dB flat to 30Hz is very good, this is a design for people who like to hear quality sub-bass. this in combination with the fast mid subbas of the peerless bassmid driverwill sound great.

The basmid driver has also bassreflex loading to control xmax at the low end and there for keep THD and doppler effect low.

 

[Helmuth]

Drivers.

Monacor DT300
MONACOR INTERNATIONAL😛roduct detail page

Peerless 830860

http://www.tymphany.com/files/HDS-P830860%20Rev1_0_0.pdf


Peerless sls315
http://www.tymphany.com/files/SLS-P830669%20Rev1_0.pdf

 

[Helmuth]

Virtual design fatboyII

Filter design.

 

[Helmuth]

Responses of used drivers.

Regards Helmuth

 

[Helmuth]

virtual design fatboy MKII

Alternative filter with attenuation of tweeter and impedance compensation.

I would say try what you think sound better pure or with attenuation.

To improve the response of the DT300 further place a 2,7uF parallel over R4.

Note: here mid and low is in phase this is also the case by the other filter posted because the BR tube inverts the phase.

 

[Helmuth]

People maybe notice that the sub-bas is 2dB more efficient. This is done because bass radiates in full space.

The bass energy is spread over 360 degrees.

This means that bass looses efficiency on bigger distance compared to mid frequency witch radiates in half space 180 degrees. So the mid has on bigger distance more efficiency.

This explains that a flat response on 1meter doesn't sound right on listening distance because the behavior on distance is mutated due radiation pattern.

 

[Helmuth]

People maybe notice that the sub-bas is 2dB more efficient. This is done because bass radiates in full space.

The bass energy is spread over 360 degrees.

This means that bass looses efficiency on bigger distance compared to mid frequency witch radiates in half space 180 degrees. So the mid has on bigger distance more efficiency.

This explains that a flat response on 1meter doesn't sound right on listening distance because the behavior on distance is mutated due radiation pattern.

NOTE:When a speaker is placed near a back wall low frequency can only radiated in half space so efficiency is compensated by that.

Only thing is I think reflected sound of back wall has phase problems with direct radiated sound and we notice that. So it is better to place this speaker free from walls to have a open sound.

 

[Helmuth]

A bass reflex tube shout be 1/3 Sd or bigger if the it doesn't becomes to long.

This to reduce air speed in port and there for reduce losses and air noise.

The Fatboy mkII has a big vent. See here the size of the port and air speed 1W and at 100W.

1Watt = 1mtr/sec

100 Watt about 10mtr/sec

drawing

 

[Helmuth]

As building material I advise 18mm birch plywood. For it excellent characteristic. And it is easy to work with and a transparent finish looks great.


So the total cost to build these speakers with high quality (expensive) filter-parts will be around 1000 Euro's.

 

[Helmuth]

virtual design fatboy MKII

Phase behavior simulation sub and bas-mid inclusive filter. About 25 degrees phase fault only a very little fault so very good phase behaivior.

 

[SimontY]

I like this design, one just needs to possess a large living room to put them in.

Subjectively speaking, how does this type of bandpass loading sound compared to ported, PR, sealed, TL, horn and dipole? I've heard these types but only really heard bandpass in cheap PA speakers e.g. Bose so don't have a good or real impression.

I recall reading a review of the Kef Coda 9 in the 1990s where they complained of a disjointed bass response (bandpass loading), though they also praised the "slam" of the speakers.

 

[Helmuth]

I like this design, one just needs to possess a large living room to put them in.

Subjectively speaking, how does this type of bandpass loading sound compared to ported, PR, sealed, TL, horn and dipole? I've heard these types but only really heard bandpass in cheap PA speakers e.g. Bose so don't have a good or real impression.

I recall reading a review of the Kef Coda 9 in the 1990s where they complained of a disjointed bass response (bandpass loading), though they also praised the "slam" of the speakers.

Fatboy I sounded first not tight enough, that problem was solved by a bigger port. A to small port creates energy storage in your system, what had be to radiated.

After that a had the chance to compare the band pass to the super tight measuring D'appolito I made for my colleague. That one sounded more dynamic but sounded like less bass. Overall the bandpass had the best result I think also the Titanium mid drivers helped a lot.
The bass of the bandpass went down 20 Hz, I could hear it on low level when even the door vibrated to the 20Hz. The sound I would compare to good bassreflex and it sounded warm and had power at subbas level.

I think this fatboy I sounded OK due limited group delay like the MK2 does. It is easy to have a to huge groupdelay with a bandpass design and a filter will even increase groupdelay.

 

[SimontY]

Thanks for the insight and explanation, which is really interesting. I've read so little about this bass design in practise.

 

[Helmuth]

Thanks for the insight and explanation, which is really interesting. I've read so little about this bass design in practise.

The sound much much better then the to small cheap surround sets with plastic to small huge group delay bandpass design with high WAF we al know.

Fatboy I had al ready good bass at low signal level I would say it is a advantage of the bandpass.