Subwoofer insight.


This is new territory to me. Current speakers are 2 way with frequency response of 60Hz-20KHz with +/- 2dB.  Sensitivity rated as 86dB. Chance to purchase a pair of REL 7 tis. I feel like I am missing something but will have to buy the subs to try out. My basic question is this. Does this purchase sound wise? I know what I am willing to spend but do you think I will notice an appreciable improvement.  I know that no one can listen through my ears but this is my first time doing this. Source is 75 watt integrated tube amp, McIntosh MA-2275. Thoughts appreciated. I am leaning towards going forward with the deal but would appreciate some feedback. Room is large and open, 28X38 feet with 9 foot ceilings. Thanks for any feedback.
ricmci
Yes I understand that Barry Ober likes using crossovers especially as he was involved with the JL Audio CR1 crossover.

I have the CR1 in my system and its sounds better than without, blends very well with my speakers.

Horses for courses though as you mention, look at the REL way of doing things for example.

Keep safe....
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@rgmd11

You do not need measuring equipment to set up a subwoofer. Measuring equipment would make the process easier and more precise but you can do it by ear and trial and error. Specially with multiple subs.

Barry Ober aka the “The Sound Doctor”
Barry knows his stuff but he has a different approach. He is a very big proponent of active crossovers. If you are from the school of any extra electronics in the signal path is bad, his method may not be for you. If you subscribe to the thought that a crossover is just another tool in the toolbox and if used properly it can enhance your systems sound, then maybe his approach is for you.

Either way his test/setup CD is probably a worthwhile purchase.
Unfortunately a large proportion of the audiophile community is digital phobic.
also engineering phobic
ieales, thanx for your input. IMHO Neutrik connectors s--k. The plastic used is the cheapest crap they could find. It melts if you hold the soldering iron on the pin too long. A good tech won't make this mistake but still. IMHO the best connectors for home system speaker cables are soldered on spade lugs or pins. 
I forgot about the input capacitor trick. The old Dahlquist DQ-LP1 used this trick. They gave you a fist full of capacitors. You picked the right ones based on your amps input impedance then matched the low pass filter with the dial on the front. I managed to get a pair of RH Labs woofers sounding pretty good with it. Now with digital bass management it is a different world. 
Residential subwoofers in general are pretty bad. Most of them have an enclosure designed to be a musical instrument. A proper subwoofer enclosure has to be very heavy and extremely stiff. Put your hand on the sub while playing at 95 dB. That vibration you feel is distortion. With an ideal sub you would feel nothing. This is a very expensive proposition. 
Not using a high pass filter is just a cheap solution used to pull more people in. I personally would never use subwoofers without a complete two way crossover. You can never match up a sub without one. With a 2 way crossover you at least have a chance. With digital bass/room control you can do it perfectly very time. Unfortunately a large proportion of the audiophile community is digital phobic. 
I think some people in this hobby like to fancy themselves as engineers.  They get off on over analyzing everything in their systems.  Doesn’t matter really what it sounds like....they just love trying to control parameters to achieve a pre determined outcome.  For me, my ears are my guide and sometimes a tape measure.  Infrequently I may also consult the owner’s manual!
Just watched that entire lecture.  Wasn't sure if that was Earl Geddes' theory or @ millercarbon's theory?  If I have to get a microphone and other equipment to start measuring all of this then I am in trouble. Are there any professionals out there who can be hired whom specialize in this? Not asking specifically for my area but in general.  Just like I do something specific for a fee, does this service exist? 
I believe this guy offers this service and is reputed to be very very good

Barry Ober aka the “The Sound Doctor”

https://www.soundoctor.com/whitepapers/subs.htm



I have been using multiple subs in my system for 2 years and learning and improving my set up . Until today after viewing this video I was using a steeper crossover slope . I tried a 6 db per octave and like the result . The one thing that makes my system more flexible is a DSPeaker antimode 2.0 as a sub controller only for the 6 subs . I can control the crossover and volume from a remote control and do a room EQ in the LF domain 
Just watched that entire lecture.  Wasn't sure if that was Earl Geddes' theory or @ millercarbon's theory?  If I have to get a microphone and other equipment to start measuring all of this then I am in trouble. Are there any professionals out there who can be hired whom specialize in this? Not asking specifically for my area but in general.  Just like I do something specific for a fee, does this service exist? 
ever measured a voltage sweep in to the subs?

unless the speakers are resistors or crossover-less, I'll wager it's not flat.
I take a high level output into 2 RELs from a 12wpc (or so) single ended tube amp and it works perfectly...for years...perfectly.
The Speakon connectors on REL subs may be superb but they are still just old timey high level speaker jacks underneath the pomp and circumstance.
Sorry that I do not have anything useful for the op at this time. I am just curious as to how Millercarbon has 5 subs hooked up? What type of connections are used?
@ieales I just love how you cite yourself.  Not only do you think you are really smart, you look to yourself to validate how smart you are!  Is your real name IE Trump?

I’ll reiterate again: Taking a high level output from a Tube Amp is a bad idea.

The speaker impedance controls the LEVEL INPUT TO THE SUB.
See http://www.ielogical.com/assets/Audio/TubeAmpSpkrV.png

The input to the sub is ≈7.7db lower at 20Hz than 60Hz. Blecchh !!

SS amps will exhibit considerably less change, but are NOT immune to LS impedance.

Current which drives the LS is not in phase with the voltage which drives the sub. The sub introduces its own phase errors which is why ALL subs need Continuous Phase and Polarity controls. Without them, unless the sub was engineered for the system, it’s a crap shoot. Mostly crap!

ROLL THE LOW END FROM THE MAINS AND USE THE LOW LEVEL INPUT !!!

@m-db,: no, because the input impedance of the high level input on subs allowing that are at an extremely high impedance---the sub is receiving the output signal of the power amp, but none of it's power. Amazing, ay?

HOWEVER, whatever distortion the amp is producing is part of the signal the sub receives. Some listeners don't mind that (in fact, like it), finding the sub(s) to then share the tonality of the power amp with the main speakers. Rythmik's Brian Ding disagrees (though his non-XLR models provide both low level and high level inputs), feeling the low level inputs (non-speaker binding posts) to be cleaner. The beauty of the Rythmiks is that the listener can try both, and use the one he prefers.

I'm in agreement with the recent posts describing the physical robustness of Neutrik SpeakOn connectors and would add their ease of DIY termination. As a now stunningly unemployed Bass player I have yet to experience a problem with my amplifications SpeakOn connections while still enduring the bane of phone plugs and my lesser peeve, the female IEE power cable termination.

My short experience with using an amplifiers high level output used to source signal to a subwoofer, the audible shortcoming clearly seemed the inclusion of a third input/output between the source and the speaker system and /or the proprietary wire, not the SpeakOn. Wouldn't these various component combinations create a substantial potential of impedance issues?  
For home use, where constant plugging/unplugging is uncommon, the Speakon plug & jack just add another interruption/solder joint/connection to the signal path. Probably no harm for subwoofer use, but I wouldn’t use them with main speakers.
The $50 price comes from markup.

My company installed thousands of Neutric XLRs in the 80's & 90's in pro studios. IMO, Switchcraft is a more rugged connector. SS vs pot metal, but a royal PITA to assemble. SC will with stand a road case rolling over it. Neutrik not so much.

All the stage monitors where I produce our shows use SpeakOns. They are a great connector.


Speakon plugs lock into place, protect against moisture, and are simply a better idea than RCAs, phone plugs, binding posts, and other archaic hookup items. Note that Neutrik makes possibly the best cannon (balanced) plugs also. I'd be happy if more speaker companies (like ZU has already done) adopted them...guitar phone plugs are another thing that should be banned as they come from the world of early 20th century manual switchboards...I wrestle with these things every day as a musician and pro sound tech, and Speakon plugs are simply a great idea.
ieales
There's nothing magical about SpeakOn.
IMO, they're just a $50 FanBoy addon.
Neutrik's Speakon  locking connectors are outstanding, don't claim any magical qualities and don't cost $50 ea.

I bought a Neutrik PowerCon connector when I upgraded the AC cable on an isolation transformer a few years ago. It cost about $5 plus shipping.
SpeakOn is a connector!! It is a locking connector developed for sound reinforcement. It is overkill for a home subwoofer.
It's FanBoy HiFi Jewelry as it serves NO SONIC PURPOSE.

RCA, phone plug, banana all work as well.

Since you're such a fan of the pro SpeakOn, pro systems don't drive the low end in PARALLEL with the range above it.
 

When you have your EE degree, call me back about tracking the amp output.
Rwwear. No they don’t.

He meant HiLevel inputs.

There's nothing magical about SpeakOn.
IMO, they're just a $50 FanBoy addon.
I bought a KEF Kube 10b to use with a pair of LS50s.  I had planned to drive them with speaker-level input from an Ayre A7e integrated that has no other provision for a sub.  But I learned grounding the Ayre amp with connection to a sub could be disastrous.  I might try to return the unused sub to KEF, or use it for HT -- mostly cable TV, and free up a pair of Velodyne HGS-10s to use with the HGS-15s for four sub stereo.

db 
Speakon connectors are just speaker connectors. No different. Almost all subs have them.
When we compared a beautifully crafted over $8k model with two DSP subs, its owner sold it the following week. The words this passionate Irishman used to describe it went well beyond junk.

Simply reading the manual it seemed obvious, they clearly aged out when the first set of preamplifier outputs became available.

I often consider sound reinforcement, recording, post production, and on and on, in other words the majority of the audio industry. Only one end of the high end uses that propitiatory high level subwoofer connectivity. 

That guy? He now has a full of crap DSP sub with thirteen remote controlled auto and manually adjustable parameters and filters within nine frequency bands from 15-125Hz. Six slightly augmented preset equalizations stored in memory for varying recordings or musical taste. Each setting shares a uniquely designed multi band crossover region that was also capable of closely matching his last two choices of main speakers systems sonic presentations rather than the half hearted idea of matching of a subwoofer to a speaker. Topping it off with really long RS-232 cables to two other crawl tested slave units complimenting his all tube vinyl based system. Big analog fan. 
The REL’s are powered geniuses ...they draw almost nothing from the amp via the Speakon connection.  Mains run full range.  No X crossover needed.  No extra interconnects.  No extra boxes with crap in them for the signal to be degraded.  Simple!
Without killing your budget I'm running a pair of small Sumiko S.0 subs with my Totem Tribe towers... It provides the perfect amount of punch needed for my dedicated 2 channel system.


No Electronics.

Passive XO with teflon or polystyrene or polypropylene caps. The best RCAs. Wired with silver plated teflon coated wire and Ag solder.

Listen to something with no low end like a Cecila Bartoli aria or Winton Marsalis solo. I defy anyone to hear it.

With well mated subs, the increase in mid bass clarity has to be heard.

See http://www.ielogical.com/assets/Audio/PassiveXO1.png
Speakon connectors are just old timey high level speaker connections like we used in the old days when receivers didn’t have sub outs. Maybe it’s great but seems archaic. Most subs still have high level connections for older receivers I suppose.

I would still run my mains full range. The less electronics the mains go through, the better they will sound.
^^ Nonsense.
Adding wire to the SpeakOn adds L&C to the speaker main amp circuit.
Using an XO reduces the main amp load, increasing dynamic range and reducing distortion from the main loudspeaker.

I agree there is no free lunch, but High level from the full bandwidth main is not how any pro studio or sound reinforcement system is done.

It's a bad joke foisted on the ignorant looking for a free lunch!


More stuff in the signal path means further degradation or alteration of the signal.  Simpler is better.  The mains and sub(s) should be receiving the exact same signal for maximum fidelity.  REL Speakon connections do that.  Adding EQ and crossovers and more wires and different levels with various impedance mismatches...ugh!!  For Cinema/HT?  Ok 👍. For purist 2 CH Home Stereo...keep it simple.
I did not say REL are junk. They have moved into the HiFi Jewelry market adding things which do nothing for the sound and leaving out things that would.

Phase
=====
To get low end out of a small woofer requires adding EQ to the amplifier which adds phase shift and group delay. Sound has magnitude and phase. This is why an out of phase pair of mains sounds the way it does. The amplitude is the same, but the phase is 180° out. The VECTOR sum is zero except for driver and room anomalies. So to integrate a sub, one needs both level and phase controls for the best VECTOR sum. A 180° polarity inversion is the equivalent of moving the sub ≈14 feet @ 40Hz. And a different distance for every other frequency.

Note that a phase control is not a perfect solution, it's just that it's next to hopeless without it.

See http://www.ielogical.com/Audio/SubTerrBlues.php for further explanation.

Tube Amps
=========
The REL instructions are either written for or by someone with ZERO understanding of output transformers.

Google stereophile phase in Images. Notice how the impedance rises in the low end of most speakers. With an output transformer, when the load impedance rises, SO DOES THE OUTPUT VOLTAGE. Since the REL SpeakOn input is high impedance, the sub output will increase due to the increased voltage even though the amplifier input signal does not change in level.

For the gazillionth time, roll the low end from the mains with a simple 6db/oct passive xover about ½ to 1 octave above the mains -db frequency  and drive a sub with multiple XO slopes, phase and polarity controls into the LINE input.

Follow the interface guidelines under Setup at  http://www.ielogical.com/Audio/SubTerrBlues.php.
There are links to model your room, main and sub placement. REW https://www.roomeqwizard.com/ also has good modelling.
A lot of overly complicated, unnecessarily redundant information being spread around here.  MORE IS NOT BETTER!  Insanity may dictate otherwise, but keeping it simple makes it easier to control the Q in your listening room.  Quality, fewest connections possible and patience with the setup will go far.  REL Speakon connections are THEE best way to add a subwoofer to your system for 2 channel quality sound reproduction.  Use “LIVE” recordings to dial in the presence and atmosphere that your system can deliver.  REL has very good placement advice, but experimentation is key...corners are bad!  Mine faces front and is roughly in line with the mid driver on my main speakers.  Your room will dictate which is best.  Use bass heavy acoustic music to dial the sub in, repeating familiar tracks till you are satisfied.  It’s actually not that hard and fun to do when you have some extra time to tweak:)
That is a big room, you got anything smaller, you can treat without getting the partner upset? Does it have to be that room? There is no fix without room treatment of some kind, or just use part of the room, Can you use partitions? Fold out while in use and back when not. Servo bass? OB servo bass, pressures the room a whole different way.  If I had a room that big, there would be at least a 1000 lb of speakers, just for the mains and another 1000 pounds for bass units. That put it in better perspective...BIG room, BIG speakers, more work...

Regards
MiniDSP could be employed to integrate the subs if one wanted to get more involved than a simple setup. https://www.minidsp.com/
Hi Ric,

I believe what Mr. ieales is trying to tell you is that REL subs are more difficult to integrate into a system than other brands of subs because they do not have variable phase adjustability. Phase in this case basically means that the output signal of the sub starts (or maybe I should say arrives at the listening position) at the exact same time as the output signal of the other speakers (including any other subs) in the system. In a single box speaker this is all controlled by the internal crossover. With a sub woofer and satellite speaker setup that crossover does not exist so that phase/time relationship between the sub and the main needs to be controlled in a different manner. One of the easiest and probably most economical ways to achieve this is by adding variable phase control to the sub amplifier.

REL's phase control allows you to vary the start of the signal in two increments where as other manufactures allow you to vary the start of the signal in as many as 360 increments.  It's kind of like using a ruler with markings at 0", 6" and 12" rather than using one that breaks down each inch into 1/32" segments.

Why REL does not include variable phase adjustability with their subs I do not know, I have a couple of guesses, but ultimately I do not know. OTOH there are a lot of very satisfied REL owners. So what does that mean? Who knows and for that matter who cares. I do know that you don't always need to measure to 1/32" to get the job done but if you can usually the end result will be better.

The bottom line is, do you like what you are hearing? If you do, that is all that matters.
He is trying to say the REL subs are junk and that I have them hooked up wrong, even though I did it exactly as shown by the designer.   Obviously he knows way more than the engineers at REL.    You can tell by his mastery of language. 
https://rel.net/how-to-connect-your-rel-to-a-tube-amplifier/

https://relsupport.zendesk.com/hc/en-us/articles/115005872647-Stereo-RELs-Tuning-Guide

It is common for vacuum tube power amplifiers to have three sets of output connections. Since the REL high level connections draws no current, it is best to use it with taps intended for driving higher impedances such as 8, or even 16 ohms.
We suggest starting by connecting the RED and YELLOW “hot” wires of the REL high level cable to the 8 ohm speaker outputs. This is recommended even if your main speakers are connected to 4 ohm (or 2 ohm) outputs because the gain of RELs is designed to follow the longstanding industry practice of using 8 ohm as a standard. Selecting a lower impedance for the REL connection will result in MUCH lower output. 



I’m so sorry ieales but I don’t understand what you are trying to say. Read it multiple times but still don’t get it. Any chance you could say it without the subliminal messaging?
@soundermn 
I bin doin' dis a long time.
I got da tools.
Tryin' to set up subs w ½-arsed controls is a YUGE PITA.

IME, high level inputs w a toob amp is a bad idea. Transformers are current devices and many speaker impedances are all over the map in the low end, causing similar input vagaries to the sub. Ergo, the sub is mimicking the eff'd up main low end. BTDT.

Roll the low end out of the mains. If they were any good in the bottom, subs would not even be an issue.

My tongue is about an inch short from all the times I've bitten it when subjected to systems with ½-arsed subs.

=======================
As a composer friend once said on hearing my phase correct sub:

Those little speakers aren't putting out all that gorgeous bass?!?!?!?!?

- No, there's a subwoofer at the end of the sofa. -

Every other subwoofer I've ever heard just boomed!

Almost...
=======================

Others on later phase correct systems:
- Joe Pass is sitting right there!
Man, your system is so precise!
- etc.

 
Chaz, - 6 @19hz is getting closer. Now if REL can just go a little lower for less $. The RELs are pretty though.