flat freq resp + large box?

[mchello]

Dear Infinite Baffilians:

This is my first post to this forum; apologies for possible cluelessness.

I'm contemplating a subwoofer project for my personal recording studio -- a subwoofer pair (left-mono + right-mono). The control room is 1,990 cubic ft, rectangular, soon to be well-treated with bass traps, broadband absorption, and diffusors.

The monitoring options at present include Canton GL260/Bryston 4B-ST nearfields, Tannoy 800A powered nearfields, Mission 770/McIntosh 2100 midfields, and KRK Rockit 10 subs (left and right). The KRK subs are switchable in/out, to be paired with any of the other loudspeakers.

The Cantons and Tannoys, with or without the subs, usually serve just fine for mixing decisions (the Cantons are mercilessly accurate; the Tannoys basically honest but more forgiving); while the Missions with the subs do a good job of sounding big and dramatic when all I want to do is have fun.

When mixing, I check the subs to make sure I'm not missing low frequency noise. But the music itself doesn't go any lower than a kick and a four-string bass.

So what I'd like to do is have my cabinet-maker friend build me some glorious boxes, and fill them with some appropriate drivers, and cross them over 24 dB/oct Linkwitz-Riley to the other boxes.

My present subs sound muddy and indistinct. I'd like to replace them with something that is, by design, extremely flat in freq response, something that extends quite low, yet with low distortion. I'd like for the transient response to be good as well, insofar as that is possible. And given that this is a DIY thing, I hope to end up with something that performs way better than the money spent!

One of the things I have going for me is that I have the space for really sizable boxes: about 12 cubic ft. Another thing that may make the design challenge easier is that I do not need or desire high-SPLs. Instead, I'm talking about a system capable of reproducing ultra-low bass clearly and articulately, free of frequency-repsonse anomalies, and as musical overall as possible.

I wonder if a brute-force approach might work: each 12 cubic foot box loaded with something like a MacCauley 6174 (Fs = 20 Hz; Vas = 25.9 cubic feet), with extensive internal bracing, very heavy and low-resonant construction materials and methods, an internal structure to suppress standing waves, etc.

So I'd have a pair of boxes about 48" high x 24" wide x 19" deep, maybe 175 lb each, and 500 watts per channel into 8 ohms powering them, if desired (Crest 7001). But I also have a Carver PM300 available, which is 100/ch @ 8 ohms, and given the modest levels I like, probably would be absolutely fine.

So that's all the background. Now for my question: given that I like SPLs that allow me to comfortably talk and be easily heard. And given that I have no interest in going with a smaller box size. And given that I care about flatness, low extension, naturalness, and transient response: instead of the above-mentioned single 18" driver per cab (infinite baffle), would it be worth attempting to achieve comparable performance in the same size boxes but with an array of smaller drivers? And if so, what would you suggest? What would be the pros and cons?

Thanks in advance,

mark

[FOH]

Two things;

First, unless you're mixing LFE, I'd never recommend attempting to integrate a subwoofer system into a monitoring scenario. If you need stronger LF response in studio, there's no need to look past your mains.

Second, what you've described is not an infinite baffle design. Even though the individuals that contribute here have the skill-set to help in this endeavor, there are much more appropriate forums for you to solicit ideas.

The DIY forum at AVS would be a good source;
www.avsforum.com/avs-vb/forumdisplay.php?f=155


Good luck

[chrisbee]

Apr 16, 2011 7:18:00 GMT -7 FOH said:

First, unless you're mixing LFE, I'd never recommend attempting to integrate a subwoofer system into a monitoring scenario. If you need stronger LF response in studio, there's no need to look past your mains.

Perhaps you'd like to expand on this. I'm not arguing but I feel your advice needs supporting argument.

[mchello]

Thanks foh and Chrisbee.

Foh, during mixing I want to be able to make sure that I haven't allowed any weird, unwanted low-freq noise to creep in (e.g., rumbling, etc.). Other than that, I don't actually need accurate lows. I may play around with electronica and then it would be nice to have such a capability; but for now the music I do doesn't require it. But I _want_ it just for fun. My present subs, KRK Rockit 10's, are flat down to 34 (+/-1dB), if the published specs are to be believed. Another huge variable is that I haven't got the bass traps in the room yet, and this should make a huge difference in tightening up my existing setup. But I would like to see if I can improve on the transient response, articulation, and overall musicality of the KRKs. So maybe I'm on a fool's errand. But I will learn from the process even if the buid is a flop. Then I can try again!

The mains are fine for "impressing the client" -- except that it's a private studio, so the clients are me and my friends. In other words, it's all a lark. The Tannoy 800A's and Canton GL260's do the real work. Everything else is for instant gratification!

I'm not wedded to a sealed cab, only trying to achieve the maximum flatness, transient response, and musicality I can, consistent with extension down into the lowest audible octave.

I would much rather try a homebrew effort than simply buy a finished product. I have admired the Velodynes, for example. But part of the satisfaction here would be the process itself.

regards,
mark

[chrisbee]

If you only want to monitor for unwanted infrasonics there is no reason for a subwoofer to be fully integrated with the speakers for reproduction. All you need is reasonable calibration. Or matched levels between your subwoofer and your speakers. You can even switch off the speakers to monitor the lower frequencies in isolation. Perhaps I am oversimplifying your needs?

[FOH]

Apr 17, 2011 11:10:40 GMT -7 @chrisbee said:

Apr 16, 2011 7:18:00 GMT -7 FOH said:

First, unless you're mixing LFE, I'd never recommend attempting to integrate a subwoofer system into a monitoring scenario. If you need stronger LF response in studio, there's no need to look past your mains.

Perhaps you'd like to expand on this. I'm not arguing but I feel your advice needs supporting argument.

Properly integrating a sub into a monitoring system is a monumental task. Really,..in my opinion, to achieve absolute seamless integration, a total commitment to a tedious task must be given. The OP states the accuracy of the sub LF isn't critical, that makes it a much easier proposition. Studios mixing multichannel audio typically mix thru full range boxes, with an independent LFE channel low passed at 120hz.

However, they should always check the final mix over a bass managed, 80hz Xover system, purposely and separately config'd to check for potential problems. Just as the OP stated the lack of perfect integration, in the studio the same thing applies. The secondary bass managed rig, although I'm sure it's damn good, it's real purpose is just to check to see if a typical home rig w/bass management won't create problems. Merely as a safeguard, not as a mixing tool.

All this said, I'm sure there are many bass managed primary monitoring rigs out there, I just don't think it's the norm. Also, full disclosure,...I'm not in the loop anymore, so I may be entirely wrong. Separate from home music studios, I'd really enjoy touring a first rate dubbing stage, whereby a large scale and wide-bandwidth monitoring rig resides. Like many things, upon seeing it, hell many home rigs may blow them away!

Anyone know of any good articles/interviews along these lines? ..ie, large scale, full surround +LFE monitoring rigs?



Thanks and good luck

[chrisbee]

One must presume that monitoring is a rather more demanding task than merely listening (critically) for pleasure.

Otherwise several million subwoofer owners are wasting their time. (and money)

[FOH]

Chrisbee,
I don't understand;... am I way out in left field on this, or is your experience consistent with my post? Will you elaborate?

Take a big active three way Genelec, or Quested. Consider all the R&D, engineering, and voicing that went into integrating one section to another. Once that design is fully realized, it's put forth into their lineup. IMO, the same degree of difficulty and due diligence must be put forth to fully optimize the transition to an outboard LF reinforcement sub-woofer.


Thanks

[chrisbee]

Your knowledge of the subject quite obviously eclipses my own. I'm just hoping for greater understanding why a monitoring system should be sans family jewels. Particularly with the emphasis on bass in recent music thanks to the extended FR of CD. How else is one to monitor sub 30hz content for accuracy and balance?

Genelec have been making quality subwoofers for years. Presumably for studio monitoring. Many recording studios use subwoofers and have done so for years. I have even heard of studios installing IBs to better understand what they are putting on their music disks.

Is it only in the context of the OP's system that you object to the introduction of larger/better subwoofers for monitoring?

[FOH]

First, don't assume I'm more knowledgeable wrt studio equipment than yourself. I've never worked in a studio. I've been with acts while they're tracking in the studio etc., ..that's it.


It's my understanding, studios producing 5.1/7.1 work are going to have LFE subs. And for these Low Frequency Effects, this system should be quite capable. However, so is (6), or (12) 15's spread across the front with dual/quad 15" soffit mounted monitors. They need enough swept area to cover an element fully panned hard into themselves. Additionally, when mixing surround, all speakers are to be identical. I don't no how effective bass management would be unless the sub system even had more displacement than all the mains.

A large monitoring rig like that would be hugely expensive, and yes a bass managed/smaller system would be more economical, and yet highly capable.

Perhaps the subs we see in studios are for bass management verification, or LFE duty. Or maybe they're more prevalent than I thought for mains duty. It just my experience that big studios, typically run the soffit system full-range, sans subs,...however with the family jewels relatively intact.

Interesting; www2.grammy.com/PDFs/Recording_Academy/Producers_And_Engineers/5_1_Rec.pdf

Any link on the IB studio rig?

[chrisbee]

Subwoofer manufacturers have been bragging about which studios use their kit for years. Presumably surround sound was not always part of their daily bread. So they were recording (and monitoring) music. REL Studio. B&W 800 series. Genelec 7073A Veodyne 1812 etc..

The studio IB was a rumour I read somewhere online.

[FOH]

I asked about a custom studio IB, it reminded me of a brief story.

I remember as a young man of about 18 or so, I went to a local studio to price time for an act I was working with. They weren't busy so they took me into the main control room and played a track through the big soffit mounted mains. I had never heard anything so effortless. Solid LF and natural cymbals,..I mean cymbals sounding like cymbals. I really wish I was more prepared, because it was quite the audio moment looking back. I knew right then than big speakers matter, and there is no such thing as too big. Thinking back, they may have been Westlakes, or custom Westlake knockoffs.

I remember stuff being everywhere. No tidiness here,...ashtrays overflowed, beer bottles from a previous session, cables, instrument cases, just stuff everywhere.

Anyway, I was trying to be cool, and act like I did this all the time and I had a little knowledge of DIY, etc. But, I clearly remember looking down at the lower wall section below the big mains and there was a portion of the wall missing just about 1 foot square. I point it out coolly and inquire "is that the bass reflex port for the mains?" This dude 'bout fell off his chair laughing. He said "no, that's just a hole in the wall". I was really embarrassed

[chrisbee]

I think you were and probably remain much too hard on yourself. It was a very reasonable question. IMO. Think of it rather as your attempt to understand how speakers were able to reproduce such remarkable bass.

Those who get amusement from the embarrassment of others usually have little to offer. They are usually so full of themselves that they assume there must be little left to learn. Their arrogance blinds them to the possibility that those around them have anything to offer.

Others go on learning until death or disability intervene. Every day is a valuable addition to the sum of life's accumulation of knowledge. A driving curiosity maintains interest in every facet of life's rich tapestry. (or words to that effect)

For example: Your posts have reminded me of the benefits of flush mounting. Something I seem to have forgotten over the years. (like so much else)

We usually flush mount our IBs. Thus we have one more reason to continue doing so. It may be that the working wavelengths are so long that they have little effect on refraction induced delay. While the bass gain from flush mounting is probably well worth having.

www.customaudiodesigns.co.uk/articles/soffit.htm

[mchello]

Guys, I appreciate the relaxed and cordial tone of the exchanges here! The thread wanders and drifts a little, but it seems our interests are broad enough that that doesn't seem to be objectionable to any of us.

Foh, if you admired the big Westlakes, and hold that a loudspeaker cannot be too big, then I'm thinking you might empathize with my interest in a massively over-spec'd sub system. What I'm contemplating would ordinarily be capable of very high SPLs; so my hope is that if run at a fraction of its capabilities there might be significantly reduced distortion.

By the way, guys, I don't do any multichannel work -- it's all stereo.

I'm high-passing the entire mix to eliminate true infrasonics; but I'd like to leave open the possibility of musical content at least down to the low B string of a 5-string bass, which I think is 32 Hz. And maybe some synth bass sounds even lower. But I agree, Chisbee, that integrating subs _properly_ (and 'tuning'/treating a room) are not trivial, but as you said, monumental tasks. So much so that I don't aspire to make the room truly bass-accurate, in the sense of depandably getting the ultra-lows so they translate. If I ever need that I would work with a mastering engineer who is certainly set up properly to dial in the lows definitely.

My reason for having a second pair of subs as an alternative to the KRKs is that it would be fun, and hopefully musical, even if not accurate in the rigorous sense.

The MacCauley drivers in 12 ft3 boxes should have a -3db of around 15 Hz. I just think that it would be fun. If that kind of extension is just absurd for me, then all the better, because it suggests that I could use small drivers with less moving mass, and hence, hopefully better transient response, no? My common sense, if I have any left, suggests that flat response down into the low 30's is probably all I could reasonably wish for in the context of my system. However, I can't help aspiring to a more hi-fi sound than I get from the KRKs. I won't know what they can really do until I've bass trapped the room. But there does seem to be a consensus that the KRKs leave a whole lot of room for improvement. Hence, my DIY mission here!

regards,
mark

[FOH]

You would get superior advice, wrt a box sub, at the AVS-DIY section I linked to above. That's what they do. It's a mixed bag, however there are some very bright individuals contributing there that are well versed in all aspects of box subs.

That said, your statement about high passing everything is puzzling. If a vented sub needed protection for over excursion, I can see that, but not otherwise. Why not build an IB? Remove the box from the equation.

[ThomasW]

Apr 19, 2011 13:34:26 GMT -7 mchello said:

because it suggests that I could use small drivers with less moving mass, and hence, hopefully better transient response, no?

Small drivers = fast bass is a myth.

I'm high-passing the entire mix to eliminate true infrasonics; but I'd like to leave open the possibility of musical content at least down to the low B string of a 5-string bass, which I think is 32 Hz.

Here's a plot of the low E from a string bass, seems to indicate why people might want to use subwoofers....

Attachments:

[mchello]

Foh, thanks for that link. I will check it out. But this feels like a pretty good place too, so I won't make too hasty a departure!

You wrote, "your statement about high passing everything is puzzling. If a vented sub needed protection for over excursion, I can see that, but not otherwise."

I'm very sorry -- I failed to be clear. What I meant to say, should have said, is that when doing a mixdown I send the entire 2-bus mix through a highpass filter set to eliminate anything far enough below the musical content that, factoring in the slope of the filter, could serve no musical purpose, and indeed might contain infrasonic nonmusical content which I definitely wish to exclude from the recording. The Speck ASC-V, e.g., has a shelf at 25 Hz with -15 dB gain reduction. Or I could do it with a plugin. But I'm not doing this to protect the woofer, or otherwise affect the performance of the control room monitor speakers. Rather, I'm doing it to keep that super-low stuff out of the recording itself.

But other people's recordings which I may be playing for fun or edification may indeed have meaningful musical content down in the lower reaches, and in this case I wouldn't be using such a filter in the playback chain.

You asked, "Why not build an IB? Remove the box from the equation." I am new to IB designs so I guess my excuse is pure ignorance. But I hope to stick around here and learn stuff.

ThomasW, you quoth: "Small drivers = fast bass is a myth."

The stuff I don't know could fill a large volume! I don't know where or how I came to hold that as some kind of established principle; but given what you say, I take this as a sign that I have a lot more to learn. And that, after all, is why I'm here. So thank you.

regards,
mark



"Why not build an IB? Remove the box from the equation."