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mathiasb

Maximum SPL for a given external volume?

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Hi,

I am doing a bit of research and trying to figure out what if any gains I can get from say 16...18Hz - 80Hz by moving away from the dual Ultimax 18" flat packs (build thread here @ AVS). MiniDSP 2x4HD is used, and the receiver is setup with no subwoofer (integration, xover etc. done with the DSP). The mains are the HSU Research bookshelves powered by a Behringer NU1000DSP. The room, which is shared with the kitchen, is approximately 7ft8in tall, 23ft deep and 20ft5in wide, for a volume of roughly 3600 cu ft / 102 cu m.

I do not think a ported design is possible due to the limitations of the external dimensions. The flat packs are 23" H x 20" W x 20.75" D, or 5.52 cu ft, and I can go up to 25" H x 21" W x 21.75" D, or 6.6 cu ft.

First, I was looking at building new ported boxes for the current subs, but I cannot find designs that fit within 6.6 cu ft externally. PRs also get expensive, but it might be worth it (around $900 shipped for 4x). I was eyeing the SI SHS-24 which is on sale right now, but the cabinet just cannot be made small enough. So, I think I have to stick with 21" drivers. The IPALs would not be a great fit for sealed enclosures I believe, so I would have to look for other 21's.

Am I on the right track here? Using multiple smaller (potentially ported) drivers would also be an option perhaps, but stepping down in overall area doesn't seem to be that efficient.

 

Edit: To give you an idea of what the room looks like, this is the living room, picture taken from the kitchen.

 

 

livingroom.jpg

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Without some effort (doing research / simulations), I can't say whether ported or PR at 18 Hz is really a worthwhile upgrade in those dimensions.

To get substantially more from a sealed enclosure that size, you need a super subwoofer.  Only a handful are likely to fit the bill.  Get ready to open your wallet!  Candidate include the Rockford Fosgate T3-19 and the driver I'm using, which used to be called the Funk Audio UH-21v1 but appears to have been renamed (and possibly updated) to the Ridge Audio vU-21.  Note that you'll need a bit more than 21" width if you want front-firing with the RA because it has a 21.3" diameter.  You'll want some serious power behind either of these options, like 3-4 kW each.  If you want something turn-key, Funk Audio can build something.  Otherwise, you could look into a beefier 18", but you're probably not going to gain much over the Ultimax.

As another thought, have you considered upgrading your mains before your subs?  I used Hsu Research HB-1 and HC-1 (MK2 on both models) for years.  (I still use an HB-1 pair for surrounds.)  They are indeed good speakers for being as cheap as they are, but a single 6.5" driver can only do so much.  Something with a bit higher sensitivity is likely to help a lot at higher levels.

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SME, that is a good point. I know even less about mains than I do about subwoofers. The HTM-10 kit from DYISG is not too large and might be something to look into - I don't know if there's anything else on the market that would be equivalent.

https://www.diysoundgroup.com/home-theater-speaker-kits/home-theater-series/home-theater-monitors/htm-10-kit.html

Quote
Speaker Kit Information

 

  Model:      The HTM-10
  Designer:      Matt Grant
  Frequency Response:      60hz - 20khz (+/-3db)
  Power Range:      10 - 500 watts
  Sensitivity:      95db - 2.83v/1m
  Impedance:      8 Ohm
  Tweeter:      Denovo Audio DNA-325
  Crossover Point:      1500hz
  Woofer:      Eminence 10" Deltalite
  Enclosure Type:      Ported
  Dimensions:      15" W x 19.5" H x 9" D
       
  Assembled weight:      About 28 pounds

 

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Once you are restricted to a certain cabinet size the only options for "more"  are drivers with higher efficiency, more excursion, higher power handling, and more powerful amplifiers. Notice the trend there? All of those things increase the cost. It gets expensive quickly and you quickly reach a point of diminishing returns for ever higher performance. A few of us go down this path but most just make room for bigger or more cabs.

The suggestion for stronger more efficient mains is on point. You might be surprised how much it seems to improve your bass range too. Even though it may not be putting out the real bass frequencies it can make things like kick drum and bass guitar seem to be a lot fuller. There's a LOT of content in the 80-200Hz range including upper harmonics from the bass range and that's where small woofers start to struggle.

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That makes sense. I just placed an order for the HTM-10's - a bit more cone area, and a step up without going bananas in terms of size. I'll report back in a few weeks once I've got them assembled and dialed in.

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I haven't heard those speakers, but I expect they will be a good fit for you.  I believe the DIYSG SEOS designs are generally quite good, and a 10" woofer will be a real step up for you.  Hopefully that'll add a bit more "kick" to your bass and overall clarity to the sound.  :)

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What was it you were looking to improve most with your setup? Are you mostly listening to music or HT or maybe gaming?

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On 3/23/2019 at 5:43 AM, Ricci said:

What was it you were looking to improve most with your setup? Are you mostly listening to music or HT or maybe gaming?

It's mostly movies / TV shows. But I do listen to music as well, and I'd like to get closer to the chest thump from bass guitars and kick drums. Hopefully this is a step in the right direction!

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On 3/22/2019 at 11:42 AM, Ricci said:

Once you are restricted to a certain cabinet size the only options for "more"  are drivers with higher efficiency, more excursion, higher power handling, and more powerful amplifiers. Notice the trend there? All of those things increase the cost. It gets expensive quickly and you quickly reach a point of diminishing returns for ever higher performance. A few of us go down this path but most just make room for bigger or more cabs.

Exactly the issue here.  While mentioned previously, the best value is to try and find more space elsewhere, and in the right spots.  Take a sealed sub and move it around the room to any possible locations, even if a smaller box is needed.  You might find that a few locations are 6dB more efficient over a significant range vs another location.  That's like using a woofer with 2x the excursion vs in a less effective location.  Sometimes a handful a 12-15" subwoofers in the right locations can deliver much better results, even if at more cost than a couple of refrigerator size options.  The key is for the application, you can end up with more gross subwoofer box volume than a single, size limited box.  More gross volume will be more efficient down low, and likely will allow more displacement.  

If you come back to the single box mentioned, and looking for a significant bump in output, you're probably looking at a pair of opposed, sealed 18s with LOTS of power.

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I have  design going now that is 5 cubic feet. Uses a pro 18 and a long throw single PR. this is about the max you can do in that volume but can work well if you have a high BL , low Q 18 that can drive the PR. With a pro amp you can get some serious SPL out of that size box with that set up. Adding ports just becomes too big and if you go sealed you spend a lot more on power and driver(s)

 

 

 

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