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Discussion Starter #1
I've got a couple of basic home theater jobs lined up and I'd like to build the subs myself. For these I'm looking for something foolproof I can setup and not have to worry about. I am open to ported, sealed or LLT but not over 6 ft^3 exterior dimensions. I'm literally looking for BANG for the buck on this. I'd like to be around $500 for the sub and plate. If it's going to need equalization, make sure the plate amp can do it.

James
 

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6ft^3 external will only leave you around 4.5ft internal. Too small to do anything ported other than a 12". Maybe a PR build but that'd be hard to do with your budget since the PR's will eat up part of it.

Perhaps a 12" Shiva X with the 500w Bash plate amp ported.
 

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Discussion Starter #3
I understand that bigger isn't always better. I would rather have a smaller driver implemented properly, than the next size bigger needing crazy equalization. Any high excursion 12's ( FiCar Q12 maybe)that would move as much air as some 15's and work in this size ported enclosure. Please give a plate amp recommendation with your response.

James
 

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I second the shiva and maybe the Oaudio 500w plate amp to go with it. www.oaudio.com
 

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I modeled the Shiva-X, Fi Q12, CSS SD12 and the IXL-12. With a Parts Express Bash 500 amp, the Shiva-X has the most output. The high pass filter needs to be changed to 16.2 hz on the amp. In 4.5 cu.ft.net volume porting is two 4 inch flared ports 34.5 inches long each. The amp is $228 and the Shiva-X is estimated at $195, both plus shipping.
 

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Discussion Starter #6
What is the best source for the Shiva-X. I'll load the T/S parameters into my WinIsd pro and see what it looks like. I'm kinda new using the program, but I'm learning every time I fire it up. Is this the same amplifier as the OAudio Bash 500watt?

James
 

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Discussion Starter #8
Thanks for the input Mike. I'll take a look at some of this tonight. How do you change the filter on the plate amp?

In one application, I may have space to go with a 15" ported design and could probably spend up to $600 on driver. I would probably still want to stick with a plate amp for simplicity sake. Any ideas would be appreciated.

James
 

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You change the filter by changing 2 resistors. Here's the document for the boost and filter settings.

http://www.parts-express.com/pdf/300-752.pdf

And here s a pic of where the resistors are on the board.

Bash 500.JPG

As for the 15" ported design, give us the maximum external box size and we'll take it from there.
 

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Discussion Starter #10
Great info. Thanks for taking the time to answer ALL my questions. I'm kinda going along with you entering your recommended designs into Winisd pro to see what they look like.

I could go up to about 10 ft^3 on one of them. Any ideas on a 15" driver that would work well using a plate amp with a $600-$700 budget.

James
 

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Discussion Starter #12
Mike,

I thought I read that port velocity shouldn't exceed 25 m/s. The SDX15 is showing just over 31 m/s. Is the 25m/s for unflared ports? I'm guressing the heavily flared "precision port" style ports can handle higher airflow without port noise?

It seems you really like the Bash amps. Anything wrong with the PE HPSA's? They seem to be very flexible too, with user adjustable high pass filters and the parametric EQ.

James
 

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26 m/s is where port compression starts. Port noise won't be an issue at 30 m/s if flared ports are used.

The Bash 500 is nice because of the different HPF combinations that can be used to optimize the amp for a specific sub requirement. With the HPF set at 13.9 hz you are getting the most possible from the SDX15. The Dayton HPSA500 has a HPF fixed at 18 hz. Below is a comparison of the two amps with the SDX15 in 8 cu.ft. tuned to 18hz. Green is the HPSA500 with the HPF at 18hz. Both models are with 500 watts input power.
The HPSA500 does offer 6dB of boost or 14.5dB of cut between 18 hz and 80 hz. In this case 3 db of boost at 18 hz would help raise the low end response, but a 3 db boost requires twice as much power from the amp, and the amps output maxes out sooner. The HPSA500 would definitely work with the SDX15, I find the Bash 500 a better "fit" in this application.

hpsa.JPG
 

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Discussion Starter #14
Mike,
I found some interesting info on modifying the high pass filter and parametric EQ on the Parts Express HSPA 500 and 1000 amps.

http://www.parts-express.com/pdf/modifying-the-subsonic-filter-and-eq.pdf

I've been doing some media rooms for friends and really like the idea of having a plate amp with moddable onboard high pass filter and parametric EQ to take care of any big peaks or dips you may need to work out. Most are on a budget and would trip out on talk of pro amps and BFD's.

I sold my Earthquake Kompressor 12(400 watts) and will be going with a pro amp and BFD when I get my own project under way. I'm considering the Mach 5 IXL18 or the FiCar Q18 in an LLT enclosure.

I'll have about 22 wide 22 deep and 48 tall which is about 13.4 ft^3 outside. I think I would end up with around 10 ft^3 net available for this bad boy.

Here is a quote from Steve Callas and you (Mike P.) that have me thinking about the IXL18.

Mach5 IXL18 in 10 cubes with an 8" port that is ~36" long giving you a ~18hz tuning. You will then want a 12hz highpass. Less expensive overall sub that offers more performance.
They should be back in stock in about a month or so. 12.5 cu ft. tuned to 15 hz would be the optimum size for going without a HPF.
James
 

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Correct me if I am wrong but I don't believe you need to change the filter or do any mod on the O audio 500w bash so why not just use that instead?
 

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The O-Audio amp has 4 specific HPF's. 25, 20, 16 and 12 hz. It's estimated the boost applied is 0 db, 4 db 6db and 8 db respectively. O-Audio refuses to give any information as to the exact amount of boost applied. After numerous attempts to get the information, the only response I got from them was ""refer to the posted graphs"". It was recently pointed out to me that the EQ can be applied to eliminate the boost. That being true, the performance would be the same as the PE Bash 500, the advantage being the PE amp is cheaper.
 

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Discussion Starter #18
Taking what's been said, it seems to me the OAudio may be better suited to a sealed enclosure where you would welcome the boost to help with the low end extension. That same low end boost would be a negative to the ported enclosure that needs the high pass filter to protect from over excursion with extreme low frequencies.

I talked to the technical people at PE and they told me the HSPA amps don't have a large bass boost built in like the Oaudio Bash amp. The high pass is moddable from 8-18hz without a significant amount of boost. The parametric EQ can be set to range from 18-80hz(factory setting) or 12-55hz with the change of a few components.

These are just my thoughts. I could be wrong. I've been that way before.

James
 

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The O-Audio amp is an excellent amp for sealed subs as you stated. If the EQ can be used to negate the boost then it would work well for ported also. The problem is the documentation doesn't state at what frequency range the EQ is effective. I've sent another email to O-Audio requesting the information. Hopefully they'll respond.

Credit has to be given to P.E. for the information supplied for the HSPA amps. They state the EQ can do a 6 db boost, 14.5 db cut, and from 18 hz to 80 hz. With this information you know exactly what you're getting and how it will perform.
 

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Well I actually got a response from O-Audio. I asked if the EQ was boost, cut or both and at what frequency range. The reply was:

The PEQ is designed to tame room modes so it is cut only. Center frequency coverage is 20hz to 80hz, depending on how Q is set will determine how narrow/wide the notch is around the center hz, higher the Q adjustment the narrower the notch. (lower Q setting wider the notch) The subsonic EQ provides a selectable bass boost so a PEQ with boost is not needed.


It appears the boost applied at the 20 hz HPF can be defeated, but not the 6 db of boost at 16 hz or the 8 db of boost at 12hz. So if you have a ported sub where the frequency starts to roll off about 25 hz and it can handle 4 db of boost at 20hz, or if you need a HPF at 20 hz with no boost, then the O-Audio amp would be a good match. At least now with the above information the amp cam be compared to another amp when modeling to see which amp would better match a specific sub.
 
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