Bass blockers with DB series drivers

Andy_M

I just bought Polk db series speakers to replace all the drivers in my Porsche Boxster audio system. DB400 for the front, DB650's for the doors, and db351's for the rear deck speakers. I have an Alpine CDA-9885 HU running through a Swiss Audio SMX-6600 amplifier, which is capable of 100wpc RMS. I do not have a sub in the system right now. The db650's will produce the bottom end.

The db351's come with bass blockers, but I was wondering if bass blockers are recommended for the db400's and the db650's as well ? If so, would the best be 600 or 800 hz for the db400's, and would 150hz be right for the db650's ?

I should add that the Alpine has a HPF selectable at 60,80,100,120,and 160 hz. Also it has a selectable sub out which can be set at 60,80,100,120,and 200 Hz. Sub is currently set at 100 and the HPF is set to 160.

PoweredByDodge

The Swiss is a cute lookin amp... very 'no bs' casing. While I've no experience with or opinion on Swiss (as I've never heard of it), it looks pretty.

That being said, you should not run the db650's off the subwoofer output of your head-unit. Run the Alpine's front R and L output into the R and L input of the amplifier for stage 1 and stage 2... run the Alpine's rear output R and L into the R and L input of the amplifier's 3rd stage. Tie the DB400 and 650 to stages 1 and 2 respectively, and the 351 to stage 3. That way you preserve front / rear fade, but you'll have to tweak the gain for stage 1 and stage 2 so that you get a good blend between the DB400's in the front (dash I'm guessing) and DB650's in the front doors. Use the head unit's fader control to balance out the rear 351's.

Now... you may have already figured all that out, but I just wanted to be clear. To answer your question, I would say this...

CROSSOVER POINTS (for high power)-->
30 to 55 wrms...........................................DB-351 = 150 hertz @ 12 db/octave
30 to 55 wrms...........................................DB-400 = 135 hertz @ 12 db/octave
50 to 80 wrms...........................................DB-650 = 60 hertz @ 12 db/octave


CROSSOVER POINTS (for low power)-->
5 to 20 wrms...........................................DB-351 = 100 hertz @ 12 db/octave
5 to 20 wrms...........................................DB-400 = 90 hertz @ 12 db/octave
15 to 50 wrms...........................................DB-650 = 45 hertz @ 12 db/octave

Note: none of the above are specifications. Rather, they are recommendations based upon my personal opinion and experience dealing with sizing and filtering speakers for various power levels.

With regard to bass blockers. A typical 'bass blocker' bought from a retail store or online and labeled 'bass blocker', 'bass stopper', 'speaker protector', etc., will be nothing more than a single capacitor to be placed in line with the positive speaker wire. These are only 6 db / octave filters. Rarely, if ever do they suffice. A 150 hertz 6 db bass blocker on a 3.5 inch speaker will, driven at moderate to high power, will typically result in a 'muddy' or 'distorted' sound and possibly damage to the speaker. However, 200 - 220 hertz at 6 db will typically protect the speaker, but sound very badly due to the decreased midrange response.

As I see it, you've got two options.

1- Harrison Labs F-Mod inline filters: these are placed on the input of the amplifier and can be had in various sizes. They electronically filter out the unwanted information at 12 db / octave. They are about 25 dollars (US) per pair... you would need 3 pairs (since you have 3 sets of inputs), for a total of about 75 dollars. It is the most expensive, but best 'sounding' fix. I would put their 50 Hz high pass Fmod on the DB-651's, and put the 150 Hz high pass Fmod on the DB-400's and DB-351's
http://store.hlabs.com/pk4/store.pl?section=9

2- build an appropriate filter... if you are handy with soldering / electronics, you can build six individual crossovers inside of a small package with terminals, and hide it out of sight. If you wish to pursue this route, let me know, and I'll give you links to appropriate parts and such... I estimate a 50 to 75 dollar cost.

3- yes I know I said 2 options, but in the event that you can set the rear output of your head unit to "high pass 60 hertz" (or 50 even) [to run the DB-651's], and the front output of your headunit to "high pass 150 hertz" (or even 125 and see how it is) [to run both the DB-351's and DB-400's], then you can probably get away without using ANY EXTERNAL CROSSOVER AT ALL.

In any event, whichever of the 3 above choices you pick, you will NOT be using the included bass blockers from polk. Don't throw them out though, save them 'just in case you need them for something, someday'.

Andy_M

Thanks for the help PoweredByDodge. Hooked everything up as you suggested and set the HPF on the 351's and 400's to 160 Hz, and 60 Hz on the 651's. Speakers sound great, and the 100 wpc amp delivers enough headroom power for top down - highway speed music with clarity and presence.

FYI, the Swiss didn't have super numbers, but pretty decent, and the price was right. It sounds pretty clean and will definately do the job for now. Eventually I will probably upgrade - maybe to a couple of C400.4's and add a small sub somewhere. Not too much room for one in a Boxster though.

Thanks again.

PoweredByDodge

no problem brother, it's what i do