Seas Loki crossover

[spendorspain]

Hi,

I’m building the Madisound “Loki” loudspeaker kit, based in the SEAS H1333 6in. coaxial driver with a two-way crossover (also designed by SEAS) made with Bennic/Solen poly caps and Sidewinder air core inductors, sold already mounted in a pcb by Madisound. Because I need to place it very close to the rear wall, I’ve discarded the original reflex design in favour of a sealed-box of about 7.5 liters of internal volume and a Qtc of 0.74. I’ll use it as surround loudspeaker in my music/cinema system and I hope the lean tonal balance (the WinISD predicted –6dB point is around 50Hz) will be compensated with the rear wall gain in the bass. The front baffle will be covered with a 5mm non-varnished cork sheet for flush-mounting the driver and reduce diffraction.

The kit is very easy to build, but I have a doubt regarding the crossover. The designer says that the 3.0uF cap in the treble section is optional and when used in parallel with the non-optional 2.5 ohm resistor “it lifts the response above 10kHz slightly” (see attached images). The tonal balance of my front loudspeakers (Spendor SP1/2E) is rather mellow and I very much prefer a non distracting, soft and subtle sound for rear channels. I’d also like to avoid (if possible) a L-pad (more resistors) for attenuating the surround treble level. Do you think the removal of the 3.0uF cap will be enough for soften the surrounds? Is there any other modification for the crossover that I can try?

Thanks in advance

Regards
Jose

[spendorspain]

and this is the bass section crossover schematic

[Cal Weldon]

Sound is so subjective, it's difficult for us to answer that for you. I would suggest trying the removal first and if that is not enough, the next step is to reconsider padding the tweeter.

[sreten]

Hi, I would simply omit the capacitor, /sreten.

[spendorspain]

Thank you for your comments. Audio quality is, of course, very subjetive (and perhaps more so with loudspeakers) and I know I prefer a laid-back and subtle sound rather than upfront and agressive. I'll desolder the 3.0uF cap (isolating the remaining leads) but leaving it in place, glued to the XO pcb.

Having read the posts here about cork baffle treatment, I'm also decided to use it for the front bafle finish.

Best regards
Jose

[Ron E]

I heard these last tuesday, and they sound very nice. They sounded perhaps a bit "hotter" than the other speakers that day, but very transparent (no pun intended - the cone is transparent). Standing in front of one, about 1.5 meters away, the other speaker ~3 meters to my right was plainly audible. I wonder if removing the cap and increasing the resistor 0.5 to 1 ohm might not make them more to my liking. Hard to say without measuring and modeling.

Putting them in a smaller sealed box may change the baffle step and your set may sound somewhat different.

[spendorspain]

Hi, Ron

I believe, for what I have read, that the Seas kits are very transparent and detailed but also perhaps a little bright, hence the thread I’ve post here. If the rear loudspeakers call attention by themselves, the surround effect is less convincing and I’d like to avoid this. In your post you said that increasing the series 2.5 ohm resistor to the tweeter 0.5 to 1 ohm can soften more the response. Is it as easy as fitting a 3, 3.5 or even 4 ohms 10w resistor in place of the original? Can be this done without modify the rest of the treble filter? If so, it would be ideal, as the high frequency response could be adjusted to my taste and loudspeaker placement without resorting to add another series resistor in a L-pad attenuator.

Also, it is true that the bass crossover is very simple, 2nd order with no baffle step compensation (which will need another inductor paralleled with a resistor in series with the woofer, I think), but I hope that the mounting on the rear wall will compensate this (btw, the front baffle width of my sealed box is 25 cm)

Regards
Jose

[Ron E]

The woofer inductor is ~1.8mH, right? That is big enough to do some baffle step correction and correct for rising woofer response as well. You really should measure them before tweeking the crossover further. A small change in the series resistor shouldn't matter much, but model it (perhaps in Speaker Workshop) and see what it does.