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View Full Version : Finishing up my install- question about setting up my Boston Pro60s active?



mikey7182
10-14-2007, 09:42 PM
I'll be running one set of Pro60s off an Alpine MRV-F545. The birth sheet on the amp states ~164w per channel into 4 ohms at 14V. Now in a perfect world I could assume that halving the resistance will double the output, so using that, the 3 ohm mids should see ~246w each at full gain. This may be a tad too much for them as I have heard the 200w arena is where they like to play. Maybe not. My main question is the tweeters... at 8 ohms, they'll still be seeing 82w at full gain. This seems like a bit much as well. I can always set the gains- just curious how many watts (roughly) I should run to the highs.

Another thing is xover points- I have a 9887 HU and will be running them actively through that. Should I leave the amps at full range or set their xovers/filters to the same frequencies as on the deck as 'backup'? That may sound strange but I've had issues in the past where I set a HPF on the deck and the amp on full range and it seemed to want to respond to frequencies lower and quite a bit louder than what I set the HPF at on the deck. Maybe I didn't slope them steep enough- who knows.

What points have people set the xovers at running the bostons actively? I've thought about ~3.5khz... just not sure about the slopes, etc. I was thinking crossing off the mids at 3khz@-12db/oct and the tweeters in at 3.5khz@-12db/oct.
Sound okay? Obviously it is all in how it sounds to me- I just don't want a huge spike in sound around 3200hz and this is my first time running components active. Any suggestions would be appreciated.

Mike

Makaveli7haDon
10-14-2007, 09:55 PM
http://www.bostonacoustics.com/car/tech_faq.aspx#1
your welcome

DejaWiz
10-14-2007, 10:19 PM
http://www.bostonacoustics.com/car/tech_faq.aspx#1
your welcome

And the following statements should make anyone with more than 2 brain cells to rub together a little wary of the information:



The first point is that the typical active crossover does not allow nearly the flexibility of a passive design.

The second point is that we often stagger or overlap the crossover points to achieve a flat response.

First, I want to know how the heck an active setup isn't nearly as flexible as a passive crossover?

Second, I want to know which active crossover won't let you stagger or overlap the crossover points?

mikey7182
10-14-2007, 10:49 PM
I could stagger or overlap the xover points just using my amp, let alone the 3 way xover on the deck. They are awfully proud of their components... God. They won't even mention xover points or anything because it would be like asking Honda how to build a VTech? Nice deflection. That's kind of annoying. I'm nowhere close to understanding all the intricacies of car audio in terms of technicalities, but for them to say that a passive crossover allows more possibilities or is more flexible than an active system seems a bit obtuse to me. You'd figure they'd want to be a little more customer-friendly and realize there are people out there who may not be satisfied with Boston's xover points and slopes as it pertains to their vehicle. They couldn't possibly replicate or account for the acoustics in every vehicle and build that design into one crossover.

thefunkybunch
10-14-2007, 10:53 PM
boston in particular puts a lot more R&D into their crossovers than a lot of companies do. it's not just a typical cap and coil setup. and their crossovers in particular also address a lot of different issues such as phasing issues for on and off axis mounting tweeters, tweeter protection, and AMD (which believe it or not, makes a huge difference). the pro tweeters especially tend to be a bit on the bright side, but not overly harsh to the point where you can't listen to them. without the AMD, you won't want to listen to the tweets.

i'm not saying that its impossible to run the pro's active, but to achieve the same results as using boston's passive crossovers youre going to need more processing ability than is available in 99% of the radios out there.

i'd just use the passive crossovers and bi-amp them that way. you'll still reap from the benefits of running it 3way, and having individual time alignment from the woofer to the tweeter seperately, and save yourself a whole lotta trouble. trust me, i've been in the same situation with the Z6's, tried actively; fought it and fought it, and fought it; couldn't get it to sound quite right. used the passive crossovers, biamped them with a shltload of power, and never looked back again. and i knew exactly what frequencies and slopes boston used on the Z's at the time.

DejaWiz
10-14-2007, 11:03 PM
Try them both passive and active to see which you like best.

Makaveli7haDon
10-15-2007, 12:15 AM
And the following statements should make anyone with more than 2 brain cells to rub together a little wary of the information:



First, I want to know how the heck an active setup isn't nearly as flexible as a passive crossover?

Second, I want to know which active crossover won't let you stagger or overlap the crossover points?

Finding an active crossover that will allow you to adjust each of these points independently and tuning it correctly is going to be difficult but not impossible. Just as a note: designing a passive network takes our team of experienced engineers several months to complete.

You will get better performance from your system by paying more attention to the installation techniques and driver placement rather than pursuing the use of active crossovers. There is no substitute for proper speaker placement and solid installation.

That pretty much sums it up right there

DejaWiz
10-15-2007, 12:30 AM
Finding an active crossover that will allow you to adjust each of these points independently and tuning it correctly is going to be difficult but not impossible. Just as a note: designing a passive network takes our team of experienced engineers several months to complete.

You will get better performance from your system by paying more attention to the installation techniques and driver placement rather than pursuing the use of active crossovers. There is no substitute for proper speaker placement and solid installation.

That pretty much sums it up right there

I absolutely agree with you about proper speaker placement and installation. And when good speaker placement and installation is attained, the differences between the type of crossover is going to matter little if the time is taken to properly tune the system as well. With an active crossover, the scope of the tuning range becomes much broader than with a fixed frequency passive crossover, imo.

mikey7182
10-15-2007, 12:33 AM
So because of the separate xovers, I can still bi-amp them (tweeters on front channels and mids on rear or whatever), but do I still need to have the deck set to 3 way if I do it this way? Or do I just HP the fronts and rears at 80Hz or whatever, and let the xovers do the rest? Because if the passives determine the xover points for the mids' LPF and the tweeters HPF, there wouldn't really be a need to run them actively except for the bi-amp part, which doesn't require I run them actively, right? I guess I can try it both ways. I just primarily wanted to be able to run quite a bit of power to them.

genxx
10-15-2007, 06:18 AM
Finding an active crossover that will allow you to adjust each of these points independently and tuning it correctly is going to be difficult but not impossible.

Finding a x-over to do this is very easy to come by. Here is a small list off the top of my head below. Active is not that hard, why are you making it sound like its this super hard thing to accomplish. Its all about doing a little research before you start the process. Now building passives from scratch you better know what the hell you are doing.

HU and process with the capability-Alpine 9855, 9835, 9887, P9 combo, H701/C701 combo, Zapco DSP-6 or DC amps, Eclipse 8455, 8053, 8454, 8443, 7000, 7100, Clarion DRZ9255, 955MC, DXZ775USB, 880PRS, AudioControl, 6XS, DQX, DQXS, ARC MX-3 and IDX, Coustic, PPI OMX-432 and DCX-730, Rockford 3sixty.

There are a ton of amps out there that have built in x-over's that are flexible enough to run active also.

This list could be much much longer if I started during research rather then just of the top of my head.

I am not saying one is better than the other we all have our own preference on that one.

I agree 100% that your install is the biggest part. If you do a crap install no matter how much processing power or passive set you have you more than likely will not be able to achieve the desired results.IMO

You adjust the power using your gains do not be overly concerned about having x power on tap. This only holds true with having more power than needed, if you are trying to run the mids with a 5w power amp then you may have some issues. I hope that made sense. Just make sure you set the gains properly and you will be ok.

On setting your amp gains check DejaWiz setting amp gains tutorial out. Its in his sig just click it.

mikey7182
10-15-2007, 06:22 PM
Is there an effective way to set gains without that instrument DejaWiz mentioned? I've never really had an issue with it... I've got a pretty good ear for the slightest bit of distortion, but I'm sure there may be some that occurs before it is actually audible that may still cause harm. I don't know that with 240w/side for the mids and 80w/side for the tweeters that I will ever get close to clipping them as I won't have it up quite that loud but there is always a chance! lol :D