QSC SC-2150 Clone - Page 3

Hey guys, I don't use any eq whatsoever. I did not boost the low end, that is with my lfe settings about 10 db's lower than my other speakers. I have what you call crazy room gain down low. That is the reason I went sealed. Look where the peak is, 7-25 hz. Room gain is great down there because that is the infrasonic stuff.

NEO Dan, I could only assume that my processor lets the lfe go up higher than 20 hz and full range so I have some overlap and why it peaks around 20 hz then add my room gain which is significant. My question is it possible to bring that down or bring my other speakers up. It sounds fantastic on full range with more clarity than ever. I gained more defined punch but lost spl in the punch area. Any suggestions?

It depends on what your goals are but the easiest way to flatten the combined response would be to move the crossover back up above where your room gains starts, say 60Hz or higher. Then you'd only need a single EQ on the subs to flatten them out -- IF that's what you want. I'm not a big fan of a 'house curve' that boosts the lows but some people like it.

Is a house curve typical of boosting 7-Hz or higher than that? Can EQ tame 7-20 Hz?

My graph for my crossover at 80 Hz and all speakers small.



BTW I tried lowering the bass(sub out) 10 more dB's and it did flatten out. What makes it weird is that it makes my subs or sub out's trim level 25 db's less than my other speakers which is far from flat when using test tones.

Sure, your response is flat from 7-20. You just need to adjust the stuff from 20-60 to match it and then set the sub level so the overall response is flat. If you're using pro amps for the subs, you can use their gain controls to help balance things if you don't have enough trim control in the prepro/receiver.

Yes, I have done this since(with processor trim lower) my last post.

Pro audio woofers like the ones used in your mains are of better quality than the ones in your subs.

So your room is 100% sealed with nuclear submarine like doors? How do you get oxygen in there? lol

Can't you just increase the gain for all your other channels leaving the subwoofer channel intact on your processor? I had a problem with using a yamaha PA speaker as a center, it was way too efficient needed to bring all my other speakers up and had the PA speaker at the lowest possible setting, about 9db difference.

MK's gain is really because his room pressurizes very easily. Sealed rooms have that trait....to tame it he should maybe keep the doors open.

Penn, Great suggestion, I will open the doors and then take another measurement, too late right now for high spl sine wave test, shakes the house more than movies since very low frequencies are guarenteed. I did lower my LFE trim and it did reduce the 7-20 hz level anyway. My processor can lower the trim of anyway speaker as far as need be so I don't have to touch the gain on my amps.

Hey Chucky, I checked on the parts for a DIY clone of my speaker and I would save some coin but how does one get the parts for the price actually listed by JBL? The dealer I usually use charges twice as much.

Thanks DL
I think you'll be just fine with those drivers, especially since you intend to HPF.

MK,
can you post just LFE and just fronts, that may make things easier to look at.
Also take care not to go too low or high with the digital trims you can run into SQ problems at either end of the adjustment ranges, digital clipping and muting if you drop below the least significant bit(noise floor).

We are really jacking this thread, should we relocate these posts to one of your threads?

Thanks, that makes sense.

NEO Dan, I agree. I posted all over the place to get some info. Thanks

Still thinking about going the JBL 2226H route, prefer US made speakers. I could build a single 15 with a big horn with an active crossover and possibly acheive better performance with a smaller box although more costly. What do you people think?

Why not TD15Ms? US made, John is an AVS member and we have the measurements for them.

Are you following Augerpro's build? He did a 12" but there is no reason a 15" couldnt be used.

Not really following anyone, I just want a LOUD distortionless speaker system with good frequency response, but augerpro's build is something along the lines of what I want, doesn't need to be as good looking I just want imposing black box's. But I do want 15 inch woofer's, they look more bad ass than 12's and ofcourse they need to do less work.

I like the JBL 2226H because of its reputation, I keep hearing about it everywhere and the praise it gets. The 2.5 inch voice coil on the TDM15m's is sort of ticking me off, the JBL has a nice big 4" coil. What are peoples thoughts on the JBL 2226H and TDM15m? I don't mind either one if I can be convinced their both as good as each other regardless of voice coil size.

The Euro brands are also excellent, such as BMS, B&C, Beyma, 18Sound, RCF and many offer comparable or better performance depending upon the driver and application.

Hi Guys,

My names is John Brodie, I am a Loudspeaker Engineer for QSC Audio and I designed the horns that you guys are using. Just thought I would say 'Cool Stuff' and make a few comments. First off, the primary role of our service parts store is for supporting QSC products, although we are aware that a few people are buying the parts for DIY. Provided that the numbers are small, buying a few parts shouldn't be a problem. Please be aware that we don't stock huge quantities of each part. QSC prides itself on being a good citizen within the audio world and "doing things right", but the amount of support we can give this kind of project is obviously limited (but I couldn't help chime in).

A few notes regarding the HPR horns and DIY in general:

- All of our components are designed for use in very specific products. We have the luxury of designing and selecting all of the components as a system. For instance, in the HPR series, we have precise control over the EQ, crossover and limiting on each driver's band. This systems approach yields great results, but the individual components might be harder to use for DIY than parts that are designed expressly for DIY use. It's a good idea to buy the SC-2150 crossover and matching drivers and horns. NONE of our crossovers are even close to 'off-the-shelf', they are all designed using lab measurements, good software and many hours of listening. Don't expect to drop in a stock catalog crossover and get good results.

- We buy drivers from several manufacturers, including Celestion. A few of these drivers are standard catalog parts, but most of them are designed by our in-house transducer experts. 100% of the drivers that we use are measured at the end of the production line and checked against rigorous standards.

- Buy some measurement equipment. Given the choice between 1000$ in parts and no measurement capability, or 200$ in parts and 800$ to spend on a microphone and analyzer (and books). The analyzer, combined with proper knowledge and skill will win every time (and be more fun). CLIO, Praxis etc. will all get you there with a little practice.

Best regards,

John Brodie
QSC Audio Products

Mr. Brodie, welcome to AVS and thank you for chiming in. There's a lot of attention here towards QSC products, particularly wave guides. I hope you decide to stay a while because I'm sure there will be plenty of folks (including me) that can learn a thing or two from you.

It's always nice to hear from another professional here on the forum. If you guys ever decide to closeout certain models and have spare stuff left over for old build designs......let us know on the forum. I'm sure there are many guys here that would be interested in purchasing some of it for DIY projects.

Hey Chucky, very cool build! I was pricing out the parts on QSC's store and two of the part numbers you listed didn't return any results. Did you have to call to order them? The two were for the crossover and the terminal plate (Crossover Part #: PA-000210-00 & Terminal Plate Part #: WP-002157-00).

Good point. Can you comment on the cost of the crossover and terminal plate?

Hi Guys,

Thanks for the enthusiastic response. I'll keep an eye on the forum from time to time.

cheers,

John

Thanks for posting, any free advice is welcome

Have you read Augerpro's thread, he did some great measurements and it shows the QSC waveguides having the qualities that Geddes talks about in his designs! Or my Waveguide thread, its a general waveguide discussion?

I have the waveguides/CDs from your HPR-152i and HPR-122i speakers and Im currently building both but I will use a DCX for my crossover (with measurements).

Hi chucky08016,

From the photos, it looks like you intend to use the QSC2150 crossover for your surrounds. If so, you may want to rethink that as the crossover needs to be designed for a specific enclosure and set of drivers. But maybe I'm missing something.

Mike

btw, Im a fan of your appoarch!!! I love it, I have many of the same QSC parts. Sadly, Im extremely slow at building on my speakers to redo my HT room Im stuck worrying about finishes instead of just getting them all built.

Do you like those Celestion CD/10" round waveguides?


btw, I was looking to get Linkin Park this week I need to upgrade my collection, we like the same music. Foo Fighters Live in London is what I have listened too the most in my room actually. I only have about 10 music DVDs....and about 10,000 songs ripped.