Subwoofers for dummies

[alexk0il]

Looking to add my 1st sub to a pair of RP-150M Klipsch's.

Did a bit of background reading, learned about dsp room correction, crawling, room treatment, etc. So, here how it goes. My room is untreated and is going to stay like that, it's oddly shaped, and I won't have budgets for Tinnov or Dirac correction.
Still have a couple of questions.

1. I naively assume that freq response dips/peaks can be corrected by a deducated multi band equalizer for the 10-200Hz freq range. Yet I can't find such products, except for cheap and likely useless ones for car audio. What did I miss?

2. Is it possible to correct room with raspberry pi and REW? There should be the DIGI+ I/O board with digital inputs/outputs. Can't see many people doing it. Maybe one-two posts... Why? What did I miss?

3. What's better for low inputs in terms of audio quality, dedicated low input signal or speakers out lowered through a Kicker subwoofer adapter? Cable length 3-5m.

My first post here, please be patient and gentle.

 

[pjn]

Looking to add my 1st sub to a pair of RP-150M Klipsch's.

Did a bit of background reading, learned about dsp room correction, crawling, room treatment, etc. So, here how it goes. My room is untreated and is going to stay like that, it's oddly shaped, and I won't have budgets for Tinnov or Dirac correction.
Still have a couple of questions.

1. I naively assume that freq response dips/peaks can be corrected by a deducated multi band equalizer for the 10-200Hz freq range. Yet I can't find such products, except for cheap and likely useless ones for car audio. What did I miss?

2. Is it possible to correct room with raspberry pi and REW? There should be the DIGI+ I/O board with digital inputs/outputs. Can't see many people doing it. Maybe one-two posts... Why? What did I miss?

3. What's better for low inputs in terms of audio quality, dedicated low input signal or speakers out lowered through a Kicker subwoofer adapter? Cable length 3-5m.

My first post here, please be patient and gentle.

Physics will be your problem - room modes are quite apparent at lower frequencies. Google "sub woofer crawl" as positioning the sub will key. Esssentialy put the sub in your main listening position and play sweeps between 30-300Hz crawling around on your knees until you find the best sound. That's where you put the sub. Yes, it is undignified so best done while home alone!
It is quite surprising how moving speakers and subs just a few inches one way or another will make a difference - you can picks specific problem frequencies and monitor response at the listening position. It took me months to get my room to a point where I wouldn't go "I wonder whether...." and pull out a microphone to obtain some more measurements.
I re-read your post and I may be preaching to the choir...

 

[DVDdoug]

1. I naively assume that freq response dips/peaks can be corrected by a deducated multi band equalizer for the 10-200Hz freq range.

The dips are a problem, especially where room reflections cause the soundwaves to cancel. It can take almost infinite amplifier power and infinitely large subwoofers to overcome the cancelation.

Similarly, if the sub is weak at very-low frequencies where you can't boost the output enough without driving your amp or the sub into distortion.

2. Is it possible to correct room with raspberry pi and REW? There should be the DIGI+ I/O board with digital inputs/outputs. Can't see many people doing it. Maybe one-two posts... Why? What did I miss?

That should be OK.

3. What's better for low inputs in terms of audio quality, dedicated low input signal or speakers out lowered through a Kicker subwoofer adapter? Cable length 3-5m.

Typically you want a full crossover to send the low frequencies to the sub and to block those frequencies from the main speakers. The easiest way of doing that is with an AVR which always has "bass management" built-in. Or some powered subs have a line-level crossover built-in.

 

[OldHvyMec]

I think your approach is backwards. You take some measurements and you treat the room. You don't have to spend a fortune but you have to know
the peaks at least and treat them. Play with DSP all you want, there is still a proper way to a lot better sound.
With little or no treatment is more like noise than music. I'll stick with the verbage "SOUND", at this point.

Case and point: You want good sound but you limited 50% of the issues you have. "The Room". I'd like to say it would work but it never does.
The best DSP can do is still a pretty poor substitute for the real thing. I use passive materials and Helmholtz adjustable resonators at about 2
per 100 sf of floor space. Curtains, rugs and placement. Simple tone controls are still forever easy once you learn about "BASS MANAGEMENT".

Bass Management that I'm referring to is not in an AVR/AVP box. It is a system that should work with any speaker, less 300hz and below.

I'm 100% analog from 10hz to 20 + khz. I do have an option for correction, the difference is I don't need it. Not even a rumble filter is used.
with the heaviest of bass tracks. Servo subs are a TT friend.

I don't care what the source is, LP, Reel to Reel, Cassette, CD, or Streaming, you can't make chicken soup out of chicken$hit.

My best in any case.

Regards.

 

[MarkS]

My room is untreated and is going to stay like that

So ignore the people who say you MUST treat your room. Plenty of us here have untreated rooms (including, I believe, our host Amir.)

1. I naively assume that freq response dips/peaks can be corrected by a deducated multi band equalizer for the 10-200Hz freq range.

No. You need precise control over both the center frequency and the width ("Q") of each correction.

2. Is it possible to correct room with raspberry pi and REW? There should be the DIGI+ I/O board with digital inputs/outputs. Can't see many people doing it. Maybe one-two posts... Why? What did I miss?

I don't know, I'm not a computer audio guy. There should be some sort of parametric EQ ("PEQ") available. See Amir's speaker reviews for how he uses it sparingly to make corrections. Many rooms have a single worst mode, cutting just that can make a big difference. Filling in standing-wave nulls with EQ is generally not possible.

3. What's better for low inputs in terms of audio quality, dedicated low input signal or speakers out lowered through a Kicker subwoofer adapter? Cable length 3-5m.

I don't know what a "Kicker subwoofer adapter" is. All subwoofers have built-in low pass filters for the sub, but if possible you also want to do a complementary high-pass on the main speakers. AVRs do this, very few 2-channel pre-amps or integrated amps do it. Some subwoofers also allow high-pass to mains, but again very few. But it's not absolutely necessary to do this. In that case, you need to low-pass the sub to match the mains natural low-frequency fall-off as best as possible.

 

[DJBonoBobo]

Looking to add my 1st sub to a pair of RP-150M Klipsch's.

What is the source for the music?

1. I naively assume that freq response dips/peaks can be corrected by a deducated multi band equalizer for the 10-200Hz freq range. Yet I can't find such products, except for cheap and likely useless ones for car audio. What did I miss?

A parametric equalizer is rarely a piece of hardware, but rather a software or a feature of the hardware you use. A PEQ is part of Digital Signal Processing (DSP). The signal path is roughly source -> DSP -> speakers, but the DSP can be built in the source, in the speakers or it can be a standalone device (i.e. MiniDSP). Some speakers, preamps/amps and AVRs have the capability. If you use a PC you can either use a player software with a PEQ or a systemwide tool ("EqualizerAPO").

You need to know which values you have to type into the PEQ (position, width and loudness of peaks in your frequency response so to say). For this, you have to make a measurement, for example with a UMIK-1 measurement microphone and the software Room EQ Wizard (which is not a PEQ- or DSP-software, but only a measurent-software to find out the right values).

Example: You make a measurement in REW (darker blue line) and set a target (brightest, straight line), REW can calculate then the values you need to get the FR as close to the target as possible and predicts how it will measure after applying EQ.
For example -2.7dB at 20Hz with a Q (width) of 3.5 and -8.5dB at 32Hz with a Q of 3.5. You can then enter these values in the software or device that has a PEQ feature.

 

[OldHvyMec]

So ignore the people who say you MUST treat your room. Plenty of us here have untreated rooms (including, I believe, our host Amir.)

This is bad advice period. "Plenty of US" does not include me. If I'm offering advice at least make it good advice and proven
time after time by more than a few HERE. Just because using inexpensive equipment or not being duped by "magic beans"
BS is the goal, FACTS are FACTS. A treated room is better no matter what you think others do. That does not = good sound.

Why don't you preface that with "Can you afford it" or "Are you renting" or "Do you have a shrew for a partner?" or "Are you unable"
or are you a LAZY person giving out bad advice?

The SysOp Amir also has a Reel to Reel and a few pieces selected for the pure curiosity and nistalaga.
It in no way negates the fact that room treatment is VERY important, because you don't see a room full of it.
What you can't see in Amir's room is the that by design some acoustical physics apply. Is the room a standard 3-500sf room
with 8, 10, 12 foot ceilings. DSP can make some very good decisions in those rooms.
In weird shapes and limiting it to no room treatment is like settling for a boom box.
Get TWO and call it a stereo.

Apples to Apples not grapefruit?

I use to think room treatment was just a pain. I was a lot less experienced, lets say. As you grow in your music listening journey
hopefully you're eager enough to get off your duff and treat the "ROOM" and really enjoy the difference vs the INDIFFERENCE
to Facts. I'll admit it is your Burger, "you can have it your way". It's still fast food and it ain't worth a $hit though.

Please don't shoot the pigeon, he/she just delivered the mail. They could have left something else though. Pigeon poop! Close to BS.

Maybe the room treatment fairies will visit and leave some nice curtains from a local theater and drop off some resonators and a rug or two.

What is the value? Priceless!

 

[droid2000]

This is bad advice period. "Plenty of US" does not include me. If I'm offering advice at least make it good advice and proven
time after time by more than a few HERE. Just because using inexpensive equipment or not being duped by "magic beans"
BS is the goal, FACTS are FACTS. A treated room is better no matter what you think others do. That does not = good sound.

Why don't you preface that with "Can you afford it" or "Are you renting" or "Do you have a shrew for a partner?" or "Are you unable"
or are you a LAZY person giving out bad advice?

The SysOp Amir also has a Reel to Reel and a few pieces selected for the pure curiosity and nistalaga.
It in no way negates the fact that room treatment is VERY important, because you don't see a room full of it.
What you can't see in Amir's room is the that by design some acoustical physics apply. Is the room a standard 3-500sf room
with 8, 10, 12 foot ceilings. DSP can make some very good decisions in those rooms.
In weird shapes and limiting it to no room treatment is like settling for a boom box.
Get TWO and call it a stereo.

Apples to Apples not grapefruit?

I use to think room treatment was just a pain. I was a lot less experienced, lets say. As you grow in your music listening journey
hopefully you're eager enough to get off your duff and treat the "ROOM" and really enjoy the difference vs the INDIFFERENCE
to Facts. I'll admit it is your Burger, "you can have it your way". It's still fast food and it ain't worth a $hit though.

Please don't shoot the pigeon, he/she just delivered the mail. They could have left something else though. Pigeon poop! Close to BS.

Maybe the room treatment fairies will visit and leave some nice curtains from a local theater and drop off some resonators and a rug or two.

What is the value? Priceless!

OP says up front, "My room is untreated and is going to stay like that"

 

[alexk0il]

So ignore the people who say you MUST treat your room. Plenty of us here have untreated rooms (including, I believe, our host Amir.)

I surely will. Thank you for your support.

Many rooms have a single worst mode, cutting just that can make a big difference. Filling in standing-wave nulls with EQ is generally not possible.

Got it, makes sense.

I don't know what a "Kicker subwoofer adapter" is. All subwoofers have built-in low pass filters for the sub, but if possible you also want to do a complementary high-pass on the main speakers.

REL recommends to always speakers out/high inputs for music with their subs. Specifically high inputs over LFE or over low inputs. Presumably due to higher voltages, less noise, not sure, maybe it's all pure marketing to justify their proprietary cable.

Some subs however only have low inputs.
Hence is my question for such subs, any advantages/disadvantages of feeding these subs with from speakers through a high-to-low adapter? As opposed to the standard and intended for that purpose pre-out feeds.

https://www.kicker.com/speaker-wire-rca-converter

AVRs do this, very few 2-channel pre-amps or integrated amps do it. Some subwoofers also allow high-pass to mains, but again very few. But it's not absolutely necessary to do this. In that case, you need to low-pass the sub to match the mains natural low-frequency fall-off as best as possible.

Using a recently serviced ~50 y.o. G class receiver as source, love it's sound despite it's laughable by modern standards specs. So no crossovers or high/low pass filters.

Hopefully the dsp on Raspberry Pi will help to further smooth out the crossover.

 

[alexk0il]

What is the source for the music?

TV/CD/LDAC Bluetooth Receiver -> DAC -> fully serviced G-class receiver from late 70s

A parametric equalizer is rarely a piece of hardware, but rather a software or a feature of the hardware you use. A PEQ is part of Digital Signal Processing (DSP). The signal path is roughly source -> DSP -> speakers,

I assume it's DAC -> DSP -> amp -> speakers in my case.

Example: You make a measurement in REW (darker blue line) and set a target (brightest, straight line), REW can calculate then the values...
View attachment 285532

I see how filters smooth out the peaks, bit dips are untreated. Are these measuremenrs done at full sub power?

If not, would it make sense to max out the sub power to raise the dips and then use the dspbfilters to flatten everything around the level of the dips and to fix the crossover?

 

[Chrispy]

What receiver is it? Does it have a processing loop or pre-out/main-in connections? If so, you could insert a miniDSP 2x4HD into the mix for bass management.

 

[MarkS]

REL recommends to always speakers out/high inputs for music with their subs. Specifically high inputs over LFE or over low inputs. Presumably due to higher voltages, less noise, not sure, maybe it's all pure marketing to justify their proprietary cable.

No idea why they say that, but it's wrong. It's always best to do signal manipulation on low-voltage signals.

Using a recently serviced ~50 y.o. G class receiver as source, love it's sound despite it's laughable by modern standards specs. So no crossovers or high/low pass filters.

No problem. I like SVS subwoofers which have built-in DSP and recommendations for how to blend with most speakers on the market without using high-pass, and also don't say stuff that's obviously wrong.

 

[OldHvyMec]

No idea why they say that, but it's wrong. It's always best to do signal manipulation on low-voltage signals.

Well you would think that. The fact is they "prefer" you use that type of hook up, with their plate amps.
I was never a REL fan when they had a bottom firing passive radiator and no slot. They were horrible to decouple unless you added a 20.00 Butt plate.
Then they went to an IB design. They were better. Then the "STACK". The price went through the roof.

I read their testing and recommendations about how to place and what to place their cabinets ON. Yikes!

If you like to feel the vibration through the floor and your bottom, couple the cabinet to the floor. 1990s tech. Decouple and use servos 1970s tech.
The industry went backwards from better to worse BUT not according to REL.

Springs, Pods or Air Ride and a design that uses a bottom slot or IB design.

REL does have nice paint/dip/? or whatever it is though.

 

[FrantzM]

This is bad advice period. "Plenty of US" does not include me. If I'm offering advice at least make it good advice and proven
time after time by more than a few HERE. Just because using inexpensive equipment or not being duped by "magic beans"
BS is the goal, FACTS are FACTS. A treated room is better no matter what you think others do. That does not = good sound.

Why don't you preface that with "Can you afford it" or "Are you renting" or "Do you have a shrew for a partner?" or "Are you unable"
or are you a LAZY person giving out bad advice?

The SysOp Amir also has a Reel to Reel and a few pieces selected for the pure curiosity and nistalaga.
It in no way negates the fact that room treatment is VERY important, because you don't see a room full of it.
What you can't see in Amir's room is the that by design some acoustical physics apply. Is the room a standard 3-500sf room
with 8, 10, 12 foot ceilings. DSP can make some very good decisions in those rooms.
In weird shapes and limiting it to no room treatment is like settling for a boom box.
Get TWO and call it a stereo.

Apples to Apples not grapefruit?

I use to think room treatment was just a pain. I was a lot less experienced, lets say. As you grow in your music listening journey
hopefully you're eager enough to get off your duff and treat the "ROOM" and really enjoy the difference vs the INDIFFERENCE
to Facts. I'll admit it is your Burger, "you can have it your way". It's still fast food and it ain't worth a $hit though.

Please don't shoot the pigeon, he/she just delivered the mail. They could have left something else though. Pigeon poop! Close to BS.

Maybe the room treatment fairies will visit and leave some nice curtains from a local theater and drop off some resonators and a rug or two.

What is the value? Priceless!

I understand that the ideal is to treat the room... What should a person do, if she/he/they are not able to, e.g. a living room shared with a spouse? EQ can help. It will not make the system ideal but can, if judiciously applied and with the proper choice of equipment, make it much better (even not far from ideal..) . It can heightened the music listening experience. EQ is not a panacea but is a good solution. I believe this is what the OP is asking. Room Treatments is not a simple affair and is out of reach for most people.
Now... to the OP
I would even go as far as recommend Digital Room Correction (DRC). It is in fact available in many AVRs. Audyssey (I am familiar with it ) and DIRAC (I know nothing about it) are more than EQ; these are very capable Digital Room Correction software and are very common. Also... I'd advise, if that is possible to replace the Klipsch by ... something else, there are several reviews in ASR to guide you... You are in the UK, what about the Kef Q150, same ballpark in term of price and IMHO, a better speaker? then you add a sub.. I tend to prefer multiple subwoofers but ... get one... for now...
A good AVR, say a Denon X-3600 or 3700 or 3800.. plus advices from the people here would take you very far. You may have to purchase one more item: the miniDSP UMIK-1 and ..come back here and ask questions... No! We will not , for the most part, at least in the beginning talk about Room Treatment.. promise..

Peace.

 

[alexk0il]

I understand that the ideal is to treat the room... What should a person do, if she/he/they are not able to, e.g. a living room shared with a spouse? EQ can help. It will not make the system ideal but can, if judiciously applied and with the proper choice of equipment, make it much better (even not far from ideal..) . It can heightened the music listening experience. EQ is not a panacea but is a good solution. I believe this is what the OP is asking. Room Treatments is not a simple affair and is out of reach for most people.
Now... to the OP
I would even go as far as recommend Digital Room Correction (DRC). It is in fact available in many AVRs. Audyssey (I am familiar with it ) and DIRAC (I know nothing about it) are more than EQ; these are very capable Digital Room Correction software and are very common. Also... I'd advise, if that is possible to replace the Klipsch by ... something else, there are several reviews in ASR to guide you... You are in the UK, what about the Kef Q150, same ballpark in term of price and IMHO, a better speaker? then you add a sub.. I tend to prefer multiple subwoofers but ... get one... for now...
A good AVR, say a Denon X-3600 or 3700 or 3800.. plus advices from the people here would take you very far. You may have to purchase one more item: the miniDSP UMIK-1 and ..come back here and ask questions... No! We will not , for the most part, at least in the beginning talk about Room Treatment.. promise..

Peace.

Thanks for your help.

Rented property, C-chapped room occupied by stairs, dining area and kitchen with kitchen island are going to complicate the treatment. Thought I might be the first one to build a sound treated kitchen. I'm sure my landlord will fully appreciate it.

Also not sure about Kefs, if anything Klipsch have a marginally better base, 7db more sensitive and I simply love the sound of those horns. And I will still bave to deal with the lack of the bass.