honestly i just read it somewhere and it makes sense to me. i'm not looking to compete in SQ or SPL shootouts but the way i have my system set up sounds great to me and everyone else that has heard it says the same. i do probably have my bass(63hz and lower) up a little high for an SQ competition but i like it.

 

I believe it's because of the steepness of the slope. You want the frequencies to all be covered equally if possible and by mixing slopes it's like boosting certain frequencies so they'll end up being louder and it won't sound as good. That could be wrong but I believe that is why you don't mix slopes.

 

LOL, very glad to see you stated "that could be wrong", because it is.

I asked the question in order to try and understand why he decided to adopt the opinion (that you shouldn't mix slopes), and he adequately answered it. While I was hoping he might have the knowledge required to elaborate on the technical pros & cons of such, I actually got the response I'd expected. I'm not sure why people read things like "never mix slopes" and take it as gospel when they aren't provided or don't understand justification for it, but people do, as we've seen here.

If a person is going to make such a claim as "you don't mix slopes" without explaining why, or even if they do provide a brief rationale, it still begs several questions;
- What if it's a 3 or 4-way system, is it only necessary to use the same slope between 2 drivers (say 12dB LP for sub and 12dB HP for mid), or must it be the same between all drivers (implying you'd also have to use 12dB LP for the mid and 12dB HP for the tweeter)?
- What if you use the same slope, but different alignments for each filter (such as 12dB L-R LP for the mid and 12dB Bessel HP on the tweeter), are you implying it's no concern as long as the slopes are the same?
- What if the components and environment acoustical measurements indicate better results could be acheived using slopes of differing rates between drivers, then do you still not mix slopes simply because "you don't mix slopes"?

Ok, enough making fun and kidding around. It's obvious I don't believe it, and feel it's perfectly fine to 'mix slopes' (prefer to say 'use different attenuation or rolloff rates") if that's what the "system" calls for. There are too many variables in audio, and if you're seeking accurate sound reproduction, all components in the system and the environment they're installed in must be adequately considered. I even have a couple of old Sony crossovers that have 3rd order LP and 2nd order HP, but with Chebyshev and Bessel alignments respectively. There have been other brands and models that did the same, and they were used in award winning competition cars back in the day, so there's an example of how it can be ok to mix slopes.

Everyone likes to stick with whatt works for them, and as long as they're happy, I think that's great. However, "you don't mix slopes" is one of those things I hope people take with a grain of salt, because it's not so simple, and not necessarily the best thing for everyone to follow for every system in any environment. Don't misunderstand, there are some simple technical incentives why people might like to always use the same slopes (primarily phase considerations, but that's a big topic itself and I don't have time right now), but there can be equal incentive to mix them.

 

Actually the reason for not mixing slopes is because of the phase shift involved at the crossover frequency. When you mix slopes you have a different phase shift on each end of the crossover frequency and can have weird cancellation problems. If you know what to listen for though you can use it to your advantage with tuning to eliminate the need for excessive EQ.

 

I liked to be humbled.

 

Yes, I really meant 31hz Low Pass for the subs. It is a very low crossover point, not only for the subs, but for the mids as well. The midbass are clearly carrying the bulk of the audio load - and the Seas Lotus 6.5"s are an AWESOME speaker.

I'm using a two way front stage (Seas Lotus 6.5" + tweeter), and a pair of 12"s from Critical Mass in a 2.3CF sealed enclosure.

This year for IASCA competition, they're doing what's known as "RTO" Real Time Output. Essentially you crank up your system between 100 and 110dB using pink noise. You'll get 0 points for 100dB (or less), and up to 10 points for 110dB. Then they flash the RTA - and your score out of 30 + your dB (0-10points) is your RTO score. I scored a 108dB and a 28 on the RTO at the last show...pretty impressive for a Sound Quality DSP setting!

USACi allows you to burp your system - and of course I changed the xover points and output for maximum output - and hit a 139.1dB at 45hz.

This past weekend, I placed 1st at the Denver IASCA/NOPI show for Semi-pro Street class.

 

I understand the first part of your post (and mentioned phase considerations previously), but am not sure what it is you're implying with that last sentence, so it'd be great if you could clarify and possibly provide an example.

Since you brought up phase, and you likely know 2nd order is the most common attenuation rate, with Butterworth being the most common alignment, I'm curious what you think about the phase issues with such a network.

Using such a xover between mid & tweeter (as an example), with both drivers wired in phase, their output will be in phase within the xover frequency region, but out of phase at all other frequencies. If you wire the drivers out of phase, then their output will be out of phase within the xover frequency region, but in phase at all other frequencies. This poses the potential for cancellation within the band that the driver outputs overlap, yet the same slope is used for both, so using the same slope doesn't address nor resolve that issue.

Additionally, if mixing the slopes/rates resulted in cancellation to the extent it was cause for concern (as you implied), then why do so many companies produce xovers with different slopes for each driver? I'm sure they know what they're doing, but that seems to be an indicator against your point.

 

Thanks for the info, I wasn't aware that's what they were doing now, as I haven't kept up much with the competition scene for several years. Interesting how the different organizations have changed their testing & scoring for RTA & SPL over the years, as I recall it going through a few iterations prior to this latest you stated.

That's such an insane range for those 6.5" woofs, I don't recall ever hearing of anyone who used a driver to span >6 octaves, or at least not beginning at 40Hz. It's hard to believe, but I guess it must be true based on your results...maybe everyone should start using them! Which woofers do you have, the PW or RW series? Looking at the specs, specifically Fs and the req'd volumes for flat response, it really seems like either of the woofers would be well into their acoustical rolloff at 40Hz, but I guess cabin gain must be making up for it, in order for you to get such a response from them. Of course using 2nd order on the subs helps too, since they're only -12 @ >60Hz.

Congrats on your latest win. Sure is nice to see such good dB at a decent frequency, rather then ~60Hz that's so typical with the SPL-only fiends.

 

Prior to building my car, Matt suggested we go listen to some high end home audio speakers at the Rocky Mountain Audio Fest www.audiofest.net - and nearly every speaker system that used Seas drivers we liked...a LOT. Matt had some other very high end drivers around for us to try in the Scion (Accuton, ScanSpeak, Dynaudio, Hiquphon, Audio Technology, ATD, Micro Precision, etc.), but we quickly narrowed down to the Seas - they're amazing sounding speakers. To use a single word: "smooth".
I'm using the Seas Lotus Reference speakers (without passive networks):

http://www.mobilesq.com/shop/product...roducts_id=163

Matt's a dealer and rep. for Seas.
http://www.mobilesq.com/store/information.php?info_id=1

...and we're on Team Seas:
http://www.mobilesq.com/store/galler...&g2_itemId=550

I should clarify that this year USACi's changed their rules for SQ competition - maximum points are earned for a burp reaching 130dB.

I've changed my subwoofers from Arc Audio's "ARC" series to a pair of Critical Mass "SS" series, and doubt we'll ever change anything in the system from here on; they're EXCELLENT subwoofers.

I poke fun at Matt for rebuilding HIS car due to how well mine has turned out. He'll be competing in IASCA's Pro-Ultimate class once his car is complete. Currently it looks like there's more of his car in our house than installed in the car. He'll be using a similar speaker setup, but he's fiberglassed a shallow 12" subwoofer in the footwell/floorpan area on the passenger's side. What's really neat is you can't tell it's there! It looks factory!

Here are some pics of the most recent Denver IASCA show:






Cheers!
Robyn

 

the pics don't work anymore and i wanna see 8's in the doors.

can the op refresh these pics?

or does anybody else have pics of 8's in the doors?

either once i kill my current speakers, or just feel the itch to upgrade, 8's are an option. either 8's or adire extremis 6.4's.

 

I don't have 8s but 7s it is:

Dayton RS180

 

what did you have to do to make them fit? anything special or just dropped right in with a baffle?

 

drop in w/baffle cutout.

 

i wonder if i can get the RS225's (the 8 inch version) in pretty easily. mate them with some seas neo aluminum tweeters. should go fairly well together.

 

I dont see why not. the hole in the door frame is big enough, just gotta cut the baffle a little bigger thats all!