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Discussion Starter · #1 ·
I'm planning a room change and it seems that multiple smaller subs might help to supplement an existing pair of sealed 15" subs I have already built in particular to help with 60Hz and 90Hz nulls. This is based on room measurements and comparing with the REW room sim, which is pretty accurate in my room. It seems the ideal locations for the rear subs is high up the rear wall, so I'm limited by size of the cabinet.

I'm thinking of multiple subs using the Peerless XLS10 driver in a 22 litre cabinet, possibly using some commercially available 'in wall' versions for two positions that are more visible (since they come with neat grilles which saves me making them).

Most of the talk on here seems to be using larger drivers, but I don't have the space where they need to be placed for larger subs. Since it's more 'mid bass' that is the issue then I'm hoping that 8 of these drivers spread around the room will give plenty of headroom and the 'ULF' will be covered by the two 15" placed together at the mid front wall position. The 15" pair already give me enough SPL down to 10Hz for my requirements (113dB at the MLP, and I tend to listen about 10dB down from reference), unfortunately they suffer the 60Hz null in the front mid wall position, but are fine below that (with eq to pull down the two main peaks at around 53Hz and 27Hz).

What issues am I up against using a mix of larger and smaller subs? I already use an iNuke 6000DSP for the 15 pair and 8 of the XLS10 could be powered from another 6000DSP (two channels of 4ohms), so will have good control over delays and parametric eq/crossover control between the ULF and 'mid bass'. I'm thinking to roll the 15s off at 40Hz, so the XLS10s will take over from 40Hz to 90Hz (I'm using on wall MK Sound MP150 LCR and matching S150T surrounds). The overall eq will be done by Dirac, but experience so far has been to optimise the subs manually first and use the DSP to pull down the big peaks individually on each sub.

Does anyone have any experience of this driver (even if used as part of a main loudspeaker)? I can get them for £90 each so not a King's ransom to build a pair to try out and use my existing iNuke to power them for testing, but any advice would be useful.
 

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What does "high in the rear walls" actually mean? In my head I have a picture of drivers being mounted between wall joists in various locations at least 6' from the ground, which is something that strikes me as rather extreme. If so, I don't imagine that would end well from a SQ perspective.
 

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Sounds like a good plan though I would start with only 2 additional subs. No direct experience with the Peerless (I read everywhere that my Scanspeaks are supposedly XLS clones but the T/S are notably different so I can't really comment). Depending on availability and cost, the Dayton RSS265HF's are also good quality drivers for your intended purpose.
 

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Discussion Starter · #4 ·
Yes you are correct, two of the the rear subs would be mounted high up at 1/4 way in from each side. The other two would be the in wall ones at 1/4 width and 1/4 height position. I can't do a true DBA because there is a window in the rear wall, so the upper subs have to go higher. Also due to the window I can't have any acoustic treatment on that wall. I don't have 'wall joists' as all four walls are breeze block and or brick cavity walls, the IW300 subs I have found are designed specifically to fit into a cavity wall.

At the front of the room it will be a false wall about 18" forward of the existing wall, those subs will be at 1/4 width 3/4 height mounted onto the existing wall/raised on wood stands, with the 15" pair at the front middle on the floor.

Having done extensive testing with REW I trust the sim, so it's a question of working out how to achieve these locations. I do know that I won't get the low end extension from the XLS10 drivers, hence the idea to keep the existing 2 x 15" pair crossed over at 40Hz.

Daytons aren't easy to get hold of over here and I don't want the hassle of trying to import. I can get Peerless or Celestion drivers easily, but the Celestion models I've looked at don't seem to perform as well in WinISD in the smaller cabinets I want to use. Plus sticking to the same driver as the bought in IW300 seems to make sense as I'm already mixing two types of driver.

As suggested I may just start with the pair of IW300 at the rear and do some measurments, but the room will be in chaos so detailed listening won't be possible. It would give me chance to do some testing with the mix of subs and setting crossovers, delays, etc.
 

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Yes you are correct, two of the the rear subs would be mounted high up at 1/4 way in from each side. The other two would be the in wall ones at 1/4 width and 1/4 height position. I can't do a true DBA because there is a window in the rear wall, so the upper subs have to go higher. Also due to the window I can't have any acoustic treatment on that wall. I don't have 'wall joists' as all four walls are breeze block and or brick cavity walls, the IW300 subs I have found are designed specifically to fit into a cavity wall.
So the drivers are being mounted on (into?) a concrete/stone wall??? I thought a standard joist setup would be tough, but that sounds even more difficult.

Unfortunately I got nothing for you. I've never even heard of that myself. I'm going to keep watching this thread though, just in case someone who has done this can provide some insight. Now I'm curious.
 

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Discussion Starter · #6 ·
I've previously fitted my centre speaker 'in wall' as I have it behind my TV which raises up on an electric lift (there is a window above and I don't want the TV stuck up in the window when not in use). The IW300 should be similar to do, so it's not unfamiliar ground for me; the inner breeze blocks are quite soft so can be cut into with a bolster chisel or a drill. The steel casing of the IW300 will act as a support for the blocks above, which is preferable to me making an MDF housing to do the same job.

This is the IW300 web page.

http://www.bkelec.com/hifi/Sub_Woofers/iW300.htm

I already have another BK sub in my second system that I found out today is the same driver, the XLS200. I can therefore use this sub as a 'mule' to help with testing. They also confirmed that the XLS10 they sell as a separate driver is the same one used in the IW300/XLS200 so my eight subs will be consistant. I will need to work out the volume of the IW300 cabinet so that my DIY MDF ones will achieve the same Qtc and overall response. At £90 per driver, plus the MDF box it's alot cheaper to build the remaining boxes myself than buy 8 off IW300. :smile:

The REW room sim screenshot is attached, but note it is for half of the subs (since the sim is limited to 4 subs). I have positioned the (left) speaker for the centre position at 1/2 height and 1/2 width. The MLP is 1/2 width and 1/5 from the rear wall (not ideal, but it isn't a dedicated room so some consideration for furniture layout has to be allowed for :wink2:). I can achieve a slightly better response if I invert the rear subs, but there is a bigger seat to seat variation, so I think the all in phase option would work out better. I have a Dirac DDRC-88A room eq, so it is possible to have upto 4 eq options, so I can have one optimised for 'my' seat as well as a larger area one.

My biggest worry is how hard it might be to integrate the existing 2 x 15" subs (they will both be front middle, where the single sub is shown in the lower 'ULF' sim). The deep 63Hz dip is the reason for the sprinkling of 10" drivers around the room, but due to room gain (those 4 breeze/brick walls help) I get a really good boost for the below 30Hz region. If I crossover from the ULF to the XLS10 around 40Hz then hopefully I will get the benefit of both responses (the ULF one takes away some response above 70Hz when combine with the XLS10 in the upper sim).
 

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You've obviously done your homework and thought this out, which bodes well for success.
 

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Thanks for sharing that info. Very good work going on here. I wish I had some free time to run a simulation of your room with all of your subs.

I see your room modal distribution lacks in the 63Hz region so you need to fill-in with lots of direct sound. The ones on the back wall are really helping you here.
 

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Discussion Starter · #10 ·
I've got the house to myself tonight, so I'm going to try some REW measurements using a single 15" in the front centre wall and my XLS200 sub (via the high level input so I can use the DSP in my iNuke) at the back of the room. I can put the XLS200 in the various rear positions to compare with the REW sim, but I obviously can't measure two 10" together at the moment.

My main focus tonight will be seeing if I can sort out the crossover between the small and larger sub. The few search results I've found seem to indicate that this is where my problems may lie. I've got a few ideas of how to approach it, hopefully at least one iteration will work out, otherwise it'll be back to the drawing board.

If I have time I might run a single point Dirac calibration, then measure with REW to see how it looks.
 

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My main focus tonight will be seeing if I can sort out the crossover between the small and larger sub. The few search results I've found seem to indicate that this is where my problems may lie. I've got a few ideas of how to approach it, hopefully at least one iteration will work out, otherwise it'll be back to the drawing board.
Is the issue possibly due to the slope? Have you tried 4th order? The faster those subs get out of each others way the cleaner the integration should be.
 

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Discussion Starter · #12 ·
I'm just going on the limited threads I found when I searched on here and elsewhere. My iNuke has a very steep slope setting of 48dB per octave, so I will try that. I agree that getting them out of each other's way seems a good idea, especially in the audible 50Hz region, plus there is some cancellation according to REW around 80-90Hz when I have the ULF and the rear 10" on. If I crossover at 40Hz then the ULF sub will be 48dB down by 80Hz which should help with the cancellation.

Going to start testing soon. :smile:
 

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Discussion Starter · #13 · (Edited)
Well I spent about 2 hours tonight trying out various settings using the single 15" at front centre and the XLS200 at the 1/4 width 1/4 height rear position. It really does look promising. :) I found that a 24dB/oct LP filter on the ULF sub at 45Hz worked best, with the XLS200 left 'full' range bar using an LS12 roll off at 20Hz to protect the driver from over excursion.

I tried both subs rolled off and it didn't work well, neither did using the 48dB/oct LP filter on the ULF, but I think the above set up would be a good starting point with the 2 ULF plus 8 XLS10 drivers in various cabinets. I also tried a 4dB boost at 65Hz on the XLS200 and this completely took the dip out of the response, leaving only a dip at 105Hz which may yet be filled in by the other 10" sub positions. I ran all the sweeps without the main speakers as I couldn't move them to the correct locations (just over half wall height), so the response naturally trails downward due to the 80Hz crossover from sub to satellites.

Anyway, enough text, here are the sweeps. Red is the XLS200 only, blue is the 'ULF' sub (with the 45Hz roll off) and green is the combined result. very similar to the REW room sim predications. :smile:

An added bonus is that the combined response has a higher SPL right down to 25hz compared to either of the single responses, bar the 52Hz peak, which Dirac will pull down anyway. I guess that's good news in terms of headroom and therefore distortion.
 

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Discussion Starter · #14 · (Edited)
Just to add the comparison between the predicted sim response using just the two subs and the measured response. Some of the peaks higher up swing further in the sim, but I haven't altered any of the absorption settings which might even things up, plus in the sim both subs are outputing signal without the low pass on the ULF one. The main focus being the below 80Hz region.
 

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Well I spent about 2 hours tonight trying out various settings using the single 15" at front centre and the XLS200 at the 1/4 width 1/4 height rear position. It really does look promising. :) I found that a 24dB/oct LP filter on the ULF sub at 45Hz worked best, with the XLS200 left 'full' range bar using an LS12 roll off at 20Hz to protect the driver from over excursion.
24dB/octave you say? So like a 4th order, eh? Wonder where I heard that before. :dontknow: :D

It seems you ended up with quite the "house" curve. Does that over-emphasize the low end, or is that what you were looking to achieve?
 

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Discussion Starter · #16 · (Edited)
Sorry I don't know the meanings of these 'order' filters, but it seems your '4th order' was correct. I couldn't really listen to this set up as the main speakers aren't in the right spot. I'm going to be reversing my room 180 degrees, so it was just the sub measurements I wanted to check tonight and the crossover to the ULF. I put the mic in the spot where the new MLP will be.

Don't forget that the response is only the subs with the 80Hz crossover in the AVR so it will be exaggerating the house curve without the main speakers being run. In practice I don't think I'll have it quite so steep once all the dips have been filled in, though I do run the current set up about 5dB 'hot' that's partly due to the dip around 60Hz with the current 2 sub arrangement.

I'll have plenty of headroom judging by tonight's measurements so I'll have the option to run hot if I want to; 8 XLS10 will be nicely matched to two channels of the iNuke 6000DSP (2 x 'banks' of 4 ohms at 1200 watts per 'bank'). The ULFs take at least 1500 watts each (Fi Q series drivers 4ohms each), so ideally I'd get a bigger amp for them. I'm still debating getting an iNuke 12000DSP for the ULFs and using my existing 6000DSP for the XLS10 drivers, might not be much difference though for the levels I listen at. I'm getting a separate 32 amp (230 volt) circuit put in to supply my AV rack, so power won't be a problem.
 

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Sorry I don't know the meanings of these 'order' filters, but it seems your '4th order' was correct.
Each "order" is 6dB per octave. What that means is 1st order is 6dB, 2nd is 12dB, 3rd is 18dB, and so one. The higher the order, the steeper the slope.

I suggested 4th because that often leads to the quickest roll-off you can achieve without any audible shortcomings; too slow and there could be an overlap, but too fast and you could suffer a phase issue. You seem to have found the sweet spot though, which is ideal.
 

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That's a pretty good response. With EQ you will have the headroom for any realistic house curve you like. With such measurements, I'm still wondering why 8 XLS10 are still needed... It will really make things more complicated (and expensive) for little gain. Anyways, just my 3cents (CDN currency).

I like the way you compared REW predictions and measurements. I wish JohnM could add a feature to export the predicted response in a text file to compare predictions and measurements of any kind. Like you said, the modes are well predicted but the damping is to be "calibrated". This is still impressive for such a straightforward/user-friendly analysis.
 

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Discussion Starter · #19 · (Edited)
Since the XLS10 will be carrying it all above the ULF roll off I thought I'd need more headroom. Otherwise I could do two IW300 at the back and a pair of XLS10 in DIY boxes at the front (at the 1/4 width, 3/4 height positions).

At £90 per driver and around £120 for the extra two cabinets having 8 drivers rather than 4 is an extra £480 give or take...not a huge amount on top really. There would be a small saving as I could get an iNuke 3000DSP instead the second 6000DSP if I only have 4 XLS10 to drive, but I'd hate to think 'what if' after I get all the decoration done as it won't be being redone for a long time after this.

Going back to the REW sim: If I don't have the high rear sub then the response seems worse once I add the matching front XLS10. That is the first screenshot below. The middle screenshot shows the rear height sub added, which smooths the response further. Also to simulate the effect of making the front height sub a 'twin' I have increased the level of that sub by 6dB in the bottom screenshot. I have a feeling that it's important to match the number of XLS10 front and rear, but putting another XLS10 at the 1/4 width, 1/4 height at the front brings back that 60Hz dip again, hence making the upper one a 'twin' instead.

What isn't visible in this sim is that having the 8 subs spread out at 1/4 width and various heights seems to help when I move the MLP around. Especially if I keep the rear subs in phase with the fronts. This bodes well for better seat to seat response (though obviously I'll focus on getting the MLP the best as that's my seat :wink2:).

My target would be to be able to hit reference level down to 10Hz. Currently the two ULFs alone manage that at 113dB, but they are diagonally opposite in the current set up. Hopefully having them co-located will help and the XLS10 will add a small amount at that frequency too. Above 60Hz it'll just be the XLS10, but 8 should leave me plenty of headroom to allow for lower distortion and room for house curve tweaking.
 

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Discussion Starter · #20 ·
I've just been comparing some older REW sweeps of my current set up against Friday night's testing. I don't know if it's to do with using a later version of REW, but my current set up had a peak 19% THD reading around 25Hz when doing my standard -20dB (master volume) sweep. The readings taken on Friday were considerably lower than this, in fact I had to change the scale on the distortion chart as I couldn't see any of the harmonic or THD plots! I know that the early sweep had the crossover set much higher, so it doesn't roll off as steeply as the recent sweeps, but the worst distortion has typically been below 30Hz, which the SPL is comparable on both plots.

For the same -20dB MV sweep using the test mixed ULF and XSL10 I get 0.34% THD at around 25Hz (the peak in both measurements).

Not sure if I'm missing something here, but this looks really promising if it is correct (or perhaps REW has just been improved since I took the 'current setup' sweep). Both sweeps have been loaded into the current version of REW though.
 

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