Pro speakers at home

[Jon Kros]

Hi,
I got a deal on some QSC Cinema screen speakers. SC-424. Left, Center and Right.
I’m part a hot Rod car club in a small warehouse and me and the boys are thinking of building a make shift theater using these. The room is 15ft x 20ft.15ft is the screen side. We will probably get the QSC side and rear surrounds also. We already have a consumer set up but no projector. Just a 65” TV, a Marantz AV-8801, some QSC and crown amps and Atlantic Technology speakers.

Keep in mind, we are trying to keep the budget low as we can. so when I read on how the system works, I saw it’s very complex needing at least a triamp set up and the DPM-300. And quite a few DCA amplifiers. This adds up fast. I’m trying to figure out if there is a way to run the speakers passively and use an our consumer Marantz AV8801 to do all the decoding/conversion and output by xlr to separate QSC amps which will power the speakers. And use the built in room calibration on the Marantz. I have a ISA450, ISA750 and possibly can get a deal on a CXD4.5Q

for the screen looking at a 100” perforated.
Not sure which projector yet.
And we will probably build a baffle with access to an equipment room behind it.

as for the set up, I know it won’t be optimized as if we had the whole QSC pro set up, but just trying to find a way to get this going for not too much money.

is this possible ?

thx

[Ryan Gallagher]

will three of those even fit behind a 100" screen? You might need a bigger room (or screen). ;-)

I suppose the subs are less critical, but even those MF horns are 30" wide. Did you mean a 100" width screen?

with a 15ft wall why are you you only aiming to cover so little of it with screen? Are there doors to avoid?

[Jon Kros]

Hi, 100” only because of budget. Maybe future So only the center channel would be behind. The Left and Right channels wouldn’t. Not ideal but this is by no means meant to be a perfect set up.

[Ryan Gallagher]

Hi, 100” only because of budget. Maybe future So only the center channel would be behind. The Left and Right channels wouldn’t. Not ideal but this is by no means meant to be a perfect set up.

If you are going through the effort to do perforated screen, it seems remiss to place L & R outside the screen. That is more "home cinema" thinking in terms of layout. Depending on the projector and if it has motorized/automatable lens shift and zoom, your best viewing experience is going to be a constant-height scope screen (2.39:1 ratio) that is as wide as the room will allow with a little buffer for aesthetics, with some black curtains you can move for side masking of narrower formats.

If you end up putting a 1.78:1 or 1.85:1 constant width screen, all your scope widescreen films are gonna feel tiny compared to your available wall space and screen. And then it opens a can of worms if you wanted to actually mask down to a scope ratio. Because movable bottom or top masking is far more complex than just curtains typically.

But like you said, it's about budget. Personally I would nab a cheap used 5.1 digital cinema processor, and then all you are missing is the array of suitable amps for those cabinets, does not have to be QSC stuff, spend your main money on the projector and screen. Your existing surrounds may be fine when you are tuning for a room that size, can always add those later.

EDIT, I say that, but then as an afterthought, some other ratio screen that better fills both your width and height would make both flat and scope ratio films max impact, but as soon as you deviate from the scope screen you start to also need the often more complex top or bottom masking.

[Jon Kros]

Hi, ok so for the audio part. the sc-424 are 4way. With a built in passive crossover for the very high frequency tweeter. I was thinking to get 3-way passive crossovers for each screen channel. Based on QSC recommended crossover points. I can have those designed and built.Then connect them to the drivers. Then use my Marantz AV8801 processor/preamp’s balanced outputs to mono bridged power amps (1500W). One for each screen channel. And round side and rear on two stereo amps (500W/Ch)Then use the AV8801’s built in audyssey calibration to tune the room.

not ideal but it should work ?

But before that, what I need to figure out is once I have plugged up all the drivers of each screen channel as one unit, with the passive crossover, the nominal speaker impedance will be lower than 2ohms. Hmmm that is low

I’m sure some amps can handle this but 4ohm nominal would be better. Another way is I can split the L C R channel outs from my AV8801 and feed 2 separate amps for tops and woofers. 8ohm amps for the tops and 4 ohm amps for the woofers.

thoughts?






Thx

[Steve Guttag]

Personally, as much as I love the SC-424 (I use them as my go-to speakers in all new installations, if the size makes sense), I wouldn't use them in the home. You aren't going to be far enough away from them for the three sections to converge. You have crossover points around the vocal range and you'll get, at best, what I call "big-sound." That is, when the sound seems unnaturally large compared to what you are seeing.

The spread from HF to LF is over 4-feet with even the spread between HF and MF nearly 2-feet. The Mid and Highs don't converge for nearly 18-feet in front of the speaker. This isn't to say you won't get mid and high but that is the point where it really starts to function as a single speaker rather than a collection of components. The horns have a 40-degree vertical dispersion so you will get some of each earlier than that, but it won't be ideal and as you move about the space, you will get a decidedly different sound experience.

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If you are getting passive crossovers designed...part of the design is determining the sensitivity of each section and then building in padding to have them balance out for a flat response. Part of that is to also present an impedance to the amplifier that is optimal. They don't all wire in parallel, as you imply. The crossover is in-line with ALL of the pieces and separately. If you look at an impedance graph on a multi-way speaker, you'll see it have peaks and lows that corresponds to each driver. Part of the challenge in a good crossover is to have the impedance uniform throughout the frequency range. It is an impossible task due to how drivers work and the fact that the LF cabinet is ported...etc. Regardless, part of good crossover design is to minimize that. You want the amplifier to see it as a single speaker (or really a resistor), not as a collection of things. It is quite challenging to get right.

You could buy an "off-the-shelf" crossover that is a near-miss:

https://www.parts-express.com/PRV-Au...869?quantity=1

It would work, after a fashion and allow you to use your Marantz AVR or roll you own as there are crossover design programs out there but I still think you are setting yourself up for disappointment except for the "WOW" factor of having a 6-foot speaker in your home theatre system.

You'd be better off snagging a decent 2-way speaker...like a retired JBL 4622/4722, QSC SC-322/422, SC-412 would even be better (you don't need a double-15). From the older JBL, 4673 or possibly the 4671. I get that you have the SC-424s. They are great speakers but they are just not the best choice for the space.

[Jon Kros]

Hi,
thx for reply
yes I see what you are saying. It’s just that we have the SC-424 already. It would probably cost more to get the other speakers. Yes we could sell these. And they were really cheap so we would probably be able to pay for the other type of speakers you mention without having to add extra funds. But it’s a hard sell.

There’s a company here in Montreal that can design a passive optimized crossover for the SC-424. And they would probably be better than off the shelf crossovers. What would be the ideal size of the room for SC-424?
Would having the 2x15 Left and Right channel cabs next to the horns instead of under be possible ?




Thx

[Steve Guttag]

It is possible but not desirable. There is a reason that speaker companies orient their drivers in a vertical line...if horizontal, the response will change as you move laterally off center.

As for an ideal space for the SC-424...oh...a real movie theatre! Seriously...something that is 40-80-feet deep is going to be in its sweet spot. The SC-444 can handle the deeper rooms.

Another cinema speaker you might happen upon that could be great in a home cinema...the SR-1590 (and even the SR-1290) with bass management would outperform in the space you have.

I have no skin in the game here. You do whatever makes you happy.

[Jon Kros]

I guess since we have them we can give a try and then take it from there. I know it won’t be anywhere close to ideal but hey we can always can always change the speakers eventually. Or go back to our old ones.
maybe we can fly them from the ceiling so we can get them at a certain angle to get the sound to the listening position. ?
Thx.

[Josh Jones]

FWIW, I was planning to put a pair of SC-412C's in my screening room, however QSC discontinued them last year. I am seriously considering having clones made using B&C drivers and horns.

Josh

[Steve Guttag]

Yeah, QSC canned most, if not all of the 2-way speakers. I know that I, personally, wouldn't can the SC-422, despite never have used it. I have used that style of speaker, however,

FWIW, QSC, on their April 2025 price sheet (so VERY fresh) is showing them as EOL with-stock (the SC-412C). So, if you still want them, now's your chance.

[Mark Gulbrandsen]

I wouldn't really call them Pro Speaker as much as I'd call them Cinema Speakers, since they are job specific. Pro speakers are more to do with sound reinforcement systems and such. Different quantities of different pieces of pro speakers can be put together based on a jobs requirements, where Cinema Speakers systems are designed according to room size.

[Sean McKinnon]

By the way just FYI the CXD4.5Q amplifier you mentioned wouldnt help you as the "Q" denotes a Q-Sys amplifier and you would need a Q-Sys core to use it (or atleast to configure it but I still would'nt do it)

[Steve Guttag]

I missed on the CXD4.5Q...I wouldn't touch it. That is from the explode-o-matic line of amps (the 4.3 and the 4.5). Plus, for home use, you'll likely find that the "Q" amplifiers (well, all of the QSC Class-D amps) are too noisy (both fan noise as well as hisssssssssss). The CX-Q are still noisy but much more reliable. I'm hoping the next generation are not so noisy.