Martin Poulin
Nov 2022
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I have been living in this house for about 15 months now and despite being on a virtual HI-FI pause, I listen to my living room system quite a bit.
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My main living room is constantly in use for background music, movies and occasional gathering, I said to myself that TV speaker aren't cutting it and I shall improve the sound.
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I had started with my JBL 305P suspended against the front wall, but they severely lacked bass punch and I didn't wanted to go with bigger speaker to fill the quite big living room. Home decor is somewhat important for me.
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I moved up slightly to my modified JBL 306P on makeshift platform above my TV. They provided a bit of improvement in punch and dynamic, but needed more help in the bass, I went shopping for subwoofers and restricted myself to buying 2 relatively small subwoofers.
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Bought a pair of USED Dayton RSS315HF-4, each housed in a 100 liters vented enclosure tuned at about 25 Hertz.
Builder fabricated them on a budget with Presswood 3/4-inch material used around. Nice real veneer made the enclosure look great despite being fairly cheap and without serious internal bracing. The good old knock test was an epic fail.
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Bought a Yamaha WXC50 preamp with Subwoofer output. (No adjustment provided for the subwoofer except the gain) and a Crown 1502 XLS to drive the subs. The Crown XLS gained me an adjustable subwoofer crossover adjustment, that helped a bit.
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Sound quality was lackluster still. Room acoustic, without any surprise, is poor. The 1502 XLS lack DSP capacity and my JBL 306P were still playing fullrange from the Yamaha preamp.
What a mess it became when I increased the SPL to level I love, the acoustic of my reverberant living room couldn't take it.
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I chose to tackle my room acoustic the lazy way and glued very thin absorbent panel on the ceiling and went to buy a MiniDSP 2X4HD. The panels on the ceiling aren't enough to affect the sound below maybe 1000 Hertz but still helped in treble and mid-range. Remember the MiniDSP 2x4HD is cheap by DSP standard, but for the living room, I've figured it would be enough.
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I've bypassed the analog section of the Yamaha WXC50 Streamer and fed the 2X4HD directly from the Toslink output of the Yamaha. The MiniDSP gained me some proper crossover for the 306P, the dual subwoofers and I've used mild overall DSP correction. I must stress that any DSP can't do anything to correct reverb and time domain anomaly and my living room doesn't have enough serious acoustic treatment to sound uniform even if I maximise DSP use.
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The JBL 306P playing only from 70 Hertz and up sounded significantly better than fullrange. The 306P room placement is pretty much the worst place one can position loudspeakers, almost in a Tri-corner placement.
Despite the better sound I got from those changes, the dual Dayton subwoofers kept sounding poor. They are OK, but they aren't relaxed and accurate by any mean.
I've sold the Dayton boxes within few months and sought a pair of 18'' subwoofer to replace them. Bigger diameter drivers engage the air much better and tend to sound more dynamic than smaller 12'' subwoofers.
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While I was looking for some high-end modern units, I've remembered that my living room isn't properly treated, and my bass quality will always suffer because of my acoustic bottleneck. My home decor is important and there was no way I would hang more acoustic treatment in the living room.
Moreover, any 18'' drivers require at least 200 liters enclosure to become interesting. Even at 200 liters volume, depending on the driver parameters, it may be way too small of an enclosure still.
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My memories of my Infinite Baffle in a previous house was still fond. Since they were my first IB build, they had issue with mounting wall structural rigidity. Yet, they still sounded superb without any perceived dynamic loss. With hindsight, facing the subwoofers forward proved to be sub-optimal unless the supporting wall was made of concrete.
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The solution for wall rigidity issue is to not require any wall rigidity whatsoever. Here comes the Push-Pull arrangement in a manifold that solve this important issue.
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I've scored a pair of vintage JBL 2241H and constructed a Push-Pull manifold in my lobby closet to create an infinite baffle system.
The JBL 2241H have a higher Fs than I've wanted but with some EQ and limit to how low I will operate them, they will suffice. The 2241H Qts of 0.40 was slightly low for an unequalized IB application but my MiniDSP would correct any frequency response rolloff.
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I use the JBL 2241H from 26 Hz to 68 Hz, the JBL 306P kick-in above that.
Minor DSP adjustment are required to even out the frequency response of both the subwoofers and the mains.
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WOW, how I did I listened to those sub-par Dayton subwoofers for so long is a mystery to me. The JBL 2241H in infinite baffle configuration are accurate, relaxed and surprisingly more efficient.
Compared to the Dual Dayton subs, Frequency Response isn't as even as before when you walk around the room, the FR change a lot as a single subwoofer can't ever provide uniform room pressure. Corners have way more bass than the center of the room.
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Yet, I would describe the overall sound quality as better.
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Panel made of thin fabric to hide the subwoofer manifold