2x 21W/8555-00 + 10F/4424G00 - Will it work?

[rskriver]

Iv'e got 6 scan-speak units lying around. 4 pieces of 21W/8555-00 and 2 pieces of 10F/4424G00

Thinking of putting them in my test closed cabinet with ~54litres resulting in a Q of ~0,8 for 2x 21W/8555-00 woofers in parallel.

Also considering if I should go with a MTM or TMM construction. For a crossover-newbie, which of these is most likely to be least troublesome in the crossover design phase?

Are there any obvious indications why these units won't work well together, that I am missing?

Best regards.
René, Denmark

 

[rskriver]

Links for the units:

http://www.scan-speak.dk/datasheet/pdf/21w-8555-00.pdf

http://www.scan-speak.dk/datasheet/pdf/10f-4424g00.pdf

 

[LineSource]

A TMWW would probably give you the best sound by adding a tweeter like the Vifa XT19 or Vifa OX20SC00-04 without a bezel frame using a LR4 Xover ~3Khz. Adding a tweeter will both provide clean extended treble to 20Khz, and an improved controlled directivity function by removing early beaming from the 10F/4424G00 if it was used full range.

The Sony SS AR1 is a good mix of engineering and style, of form and function. A tall, 13" wide cabinet will have a baffle step ~ 300-350Hz. If the 10F/4424G00 Xover is at the baffle step frequency ~3?0Hz it will not need to reduce SPL for the baffle step compensation, and allow a simple, clean Xover circuit. The two 21W/8555-00 can supply the 4-Pi baffle step SPL energy, and this also allows a simple BSC room tune resistor.

A speaker worth keeping... a speaker you can use for measurement and Xover study.

 

[Inductor]

As a start-up for a 2/3-way test speaker, for your drivers, have the FR (calculated as 92.1 dB/2.83V/m) in a small sealed enclosure of 1L (ok) to 2L (maybe to big) with a 150 uF cap and the woofers in parallel with a 1.2 mH coil, (94.4 dB/2.83V/m for 2Pi and 90.4 dB/2.83V/m for 4Pi), just as a reference for initial crossover components. Just an idea to what you are doing.

 

[rskriver]

Thanks for the answer guys.

LineSource: Yeah I am aware of the fact that adding a tweeter would perhaps improve the overall sound, but since I am a newbie in constructing passive crossovers, I think I'll go with the 2-way concept for starters and see if I can make that work whilst gaining some experience in the progress. The current test-cabs are only 10" wide, giving a baffle step of ~460hz. Will that be too high for the woofers even with a LR4 filter, I wonder? They do seem to cone break up rather early...

Inductor: Wouldn't it be wiser to start of with a higher order crossover? My guess is I'll run into trouble with an LR1, at least with the woofers.

 

[Face]

A LR2 filter @ 400hz or above will allow plenty of headroom for the 10F.

Having used the 10F in a couple of applications, I would also suggest that a tweeter should be used.

 

[Face]

Fyi, the R2004 would be a great match for those drivers, I can help you with the crossover as well if you decide to go that route.

 

[rskriver]

Will the 10F sound harsh in the top if I don't implement a tweeter to take care of the high frequencies?

Face: Thanks for the offer to help with the crossover mate, it is greatly appreciated. I will write you if I decide to fit in a tweeter in the construction, though i don't know yet which one it will be. (Probably an SB-Acoustics tweeter, good value for money it would seem)

 

[Face]

Harsh no, dull yes.

 

[LineSource]

The current test-cabs are only 10" wide, giving a baffle step of ~460hz. Will that be too high for the woofers even with a LR4 filter, I wonder?

I do not think you will experience woofer cone breakup with a 460Hz LR4 Xover. The SPL graph for the 21W/8555-00 looks flat and well controlled up to 800Hz. Since 460Hz is in the critical vocal range, you may want to also experiement with a LR2 slope which spreads out the handoff between woof-mid.

As the physical size of the 10F/4424 cone starts to create beaming, more acoustic energy is spread into the reverberant room, and less acoustic energy is directed at the listener. Most listeners would note a reduction in clarity and dynamics. To get the flattest high frequency SPL from the 10F/4424 you should experiment with a 30 degree off-axis rotation wrt the listener.

This ratio of direct vs. room acoustic energy is part of the religious choice between horns(9db direct gain), dipoles(4.77db direct gain) and conventional box speakers.

I have a computer equalizer in my system, and a 20db drop at 10Khz(SPL graph) is very noticable. You could design and construct a box such that you can add a dome tweeter.

 

[Inductor]

...
As the physical size of the 10F/4424 cone starts to create beaming, more acoustic energy is spread into the reverberant room, and less acoustic energy is directed at the listener. Most listeners would note a reduction in clarity and dynamics. To get the flattest high frequency SPL from the 10F/4424 you should experiment with a 30 degree off-axis rotation wrt the listener.

This ratio of direct vs. room acoustic energy is part of the religious choice between horns(9db direct gain), dipoles(4.77db direct gain) and conventional box speakers.

Makes me think of the originals 301/601
(images sources below for reference or fair use copyright)
Bose 301: ?udiozavar.com Bose 301 -?????
Bose 601: bose 601 in good shape - AudioKarma.org Home Audio Stereo Discussion Forums