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Loudspeaker EQ

Printed From: Graham Slee Hifi System Components
Category: DIY AUDIO
Forum Name: Owner's Hot-Mods
Forum Description: Tell us how and why you hot-modded your audio gear
URL: https://www.hifisystemcomponents.com/forum/forum_posts.asp?TID=3008
Printed Date: 10 Aug 2022 at 8:59pm
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com


Topic: Loudspeaker EQ
Posted By: Fatmangolf
Subject: Loudspeaker EQ
Date Posted: 22 Aug 2016 at 10:37pm
I have a relatively small living room with large speakers so sit closer to them than the manufacturer probably intended. I have fitted a switch on the underside of the cabinet (on the crossover access panel) that can reduce the tweeter output by about 2dB. The manufacturer had used a 1 ohm wirewound to feed the HPF part of the crossover which is about 8 ohms impedance including the ribbon tweeter, probably to balance the speaker response for expected use in a large room. I inserted a new 2.2 ohm w/w resistor in series with a switch that shorts it out when it is in the forward position.

PMC build a similar switch into the Fact 8 speakers I heard at Phil's place, although his were in a large room and sounded great on 0dB. For my speakers it is a subtle change that allows more toe-in without too much treble at close range.


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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.



Replies:
Posted By: JamesD
Date Posted: 23 Aug 2016 at 6:37pm
I did something similar to my speakers when they were in a small room. Now they're in a big room the switch and resistor have been taken out again.

I notice however that my old "bedroom" Pioneer receiver from 1967 (that was their first transistor design and cost the equivalent of £3000 today) has tone controls that must have served a similar purpose.... 😉

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Aren't ears brilliant


Posted By: DaveG
Date Posted: 23 Aug 2016 at 7:04pm
I think the same kind of switchable treble response is common in studio monitors too. Makes sense in a smaller room where larger speakers are a bit more difficult to get right. They do often have a sense of effortless dynamics that u rarely get in smaller speakers so probably worth the extra effort.

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Dave

Michell Gorbe + HR PSU -> Cadenza Bronze -> SME V -> Elevator -> Accession -> Proprius -> B&W CM6 s2 | Cusat 50 & Spatia cables ->


Posted By: JamesD
Date Posted: 23 Aug 2016 at 8:12pm
If someone cares to give me some 15" Tannoy Monitor Golds to show me effortless dynamics I won't be offended.

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Aren't ears brilliant


Posted By: Fatmangolf
Date Posted: 23 Aug 2016 at 9:39pm
Originally posted by JamesD JamesD wrote:

I did something similar to my speakers when they were in a small room. Now they're in a big room the switch and resistor have been taken out again.

I notice however that my old "bedroom" Pioneer receiver from 1967 (that was their first transistor design and cost the equivalent of £3000 today) has tone controls that must have served a similar purpose.... 😉


Thanks James, I'm relieved I'm not the first to retrofit this kind of switch and I too thought "treble cut" was easier in the old days!


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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: morris_minor
Date Posted: 24 Aug 2016 at 5:03pm
My Dad used to have some Tannoy III LZ speakers which had a couple of controls on the back for treble energy and slope (?). At the time neither he or I knew what to do with them! Shocked

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Bob

Majestic DAC/pre-amp
Accession MC/Enigma, Accession MM, Reflex M, Elevator EXP, Era Gold V
Solo ULDE, Novo, Lautus USB and digital, Libran balanced, CuSat50
2 x Proprius + Spatia/Spatia Links


Posted By: Fatmangolf
Date Posted: 25 Aug 2016 at 10:14pm
I'd never thought much about speaker EQ before as I thought the w/w pots for tweeters in 1970's and 80's were a gimmick and I'd lazily assumed the Tannoy controls were specific to their drivers. It was the graph PMC give for their HF shaping that clicked for me - resistor in series to reduce tweeter level not change the crossover slope.



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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Fatmangolf
Date Posted: 16 Sep 2016 at 8:48pm
Since that change in crossover/passive EQ I have been able to have my speakers quite close and toed-in to almost point straight at me. They were slightly too bright before to do that and get depth behind. I am enjoying the new sound more, even if it's just a slight treble cut.



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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Ash
Date Posted: 16 Sep 2016 at 10:46pm
I judge the sound of my MA Alpair 12P drivers by their on-axis balance when slightly toed in so their centre axes face my ear pinnae. The dispersion field of its treble is narrow compared to everything else it produces but they still sound great at wide off-axis listening positions.


Posted By: Fatmangolf
Date Posted: 20 Sep 2016 at 7:58pm
With only driver on each side there should be no lobbing/comb effects between drivers in the same cabinet. I suspect from my own speakers and what I have read that the right toe-in will depend on both the speakers and the room so please experiment till to get the best sound field.



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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Ash
Date Posted: 20 Sep 2016 at 8:44pm
I have two pairs of Alpair 12PW that I can use to assist my single pair of 12P below 100Hz. This is so I don't have to use a conventional box to get really low bass in the nearfield. Don't yet know much about crossover designs but won't apply any crossover to the 12P; shall just shallow-slope filter the 12PW so they produce nothing above 100-150Hz. As bass frequencies are more omnidirectional, hopefully shouldn't get any lobing problems with two adjacent 12PW. If I do, I'll just use one and build a partial box for it. Will be able to level control the one or two 12PW using a second Proprius pair.


Posted By: Fatmangolf
Date Posted: 30 Oct 2016 at 9:11pm
Some time ago I made a cheap test rig so my copy of REW 5 could measure the Thiele-Small parameters of the drivers in my GX300 speakers and I could consider the alignment used. Yes it is BB4 and Fb = 32 Hz if you are interested.
 
This weekend I got round to exploring an option I considered back then. It was to measure and compare the LF impedance curves of the two enclosures. I then matched the two pairs of woofers to get the reflex/speaker alignments as close as possible in the two cabinets. They now have virtually the same impedance peaks and same Fb. The effect is probably limited to a slight difference in rolloff but they are now very close in their sub bass response. I'd be lying if I said I could hear it!
 


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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Fatmangolf
Date Posted: 13 Nov 2016 at 12:10pm
Incidentally I worked out that the drivers' efficiency bandwidth Product EBP was about 90 so close to the threshold between suitability for closed box and for ported box. The box volume Vb and two speakers' compliance Vas and Qts gave me Qtc of 0.70. So with the port plugs in I have a really good alignment for transients and slow bass rolloff. With the ports open I have plenty of low frequency oomph in my listening room.
 
My latest EQ exploration is boosting the midrange output slightly. I do this by putting an extra resistor in parallel with the 3.3 ohm one that connects the HF+ input to the first capacitor that filters the signal getting to the midrange driver. Clipping a lead onto that capacitor and feeding it out of the port tube has allowed me to connect a 10 ohm resistor in parallel to boost midrange by just over 1dB ohm. It's just (!) audible and a nice option to have IMO when combined with the HF cut written about above. I found 4.7 ohms and 2.2 ohms too much, although 4.7 worked well with the HF on full to give a 'detailed' sound.
The idea of trying midrange boost came from the way the sound I heard changed as the volume is turned up. My speakers have a slight bass boost and rising treble which works well at moderate levels but less so if I am listening to music loudly when I notice the extremes more. I concluded it was probably due to the equal loudness contours (showing low and high frequencies are perceived as quieter at lower sound pressure levels than the middle range of sound) and I think background noise inside and outside the house is a factor too.
 
When doing these comparisons I also try switching one speaker only and listening to the impact on the soundstage. Unsurprisingly the 10 ohm had limited effect on positioning left to right where the 6.8, 4.7 and 2.2 ohm resistors spread/smeared the positioning of voices (overlapping the bass to mid crossover) and guitars/strings (mid and treble).
 
Just an experiment at the moment. However I think I will probably be changing the switch I put in for the HF cut to a double pole unit so I can include a midrange option. I will do some more listening first!
 


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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Fatmangolf
Date Posted: 14 Nov 2016 at 10:52pm
Well I have identified three settings that I like enough to hard wire them into a three way switch:
 
Full HF plus the 4R7 and 3R3 in parallel so about 2.5 dB middle boost compared to stick - "detail excavator"
HF on -2dB, no mid-boost - "comfy slippers"
HF on -2dB, 10R and 3R3 in parallel for about 1dB mid-boost - "balanced when loud"
 
 


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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Fatmangolf
Date Posted: 27 Nov 2016 at 2:51pm
In the end I kept the HF and MF switching apart. on midrange I went for 0dB (stock wiring), +1dB (10R in parallel), and +1.8dB (4R7 in parallel).
I have also been having a first stab at blending my big REL subwoofer in with the GX300's. Their Fb is about 32 Hertz so they go quite low to start with. Their reflex design has a faster roll-off, typically 24dB/octave so blending my main subwoofer will be interesting. When the reflex port is plugged on each box plugged they are closed boxes with a Qtc of about 0.7 and Fc=58 Hertz, handy because their rolloff is just under 12dB/octave which is the slope of the REL's low pas filter. So it should be easier to blend.
 
I soldered up a high level cable for the REL, spades for speaker terminals and Speakon to go into the Q400's socket. Then followed the usual set up procedure: start with sub crossover and level to high, switch phase from 0 to 180 to find which setting is loudest. In theory I would set the sub's LPF on the speaker's -6dB frequency (about 42 for closed box, 32 for reflex), but it's a relatively small listening room of 40 m3. My conclusion this time was I preferred the GX300's alone!
 


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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Drewan77
Date Posted: 27 Nov 2016 at 4:30pm
If you have a mic to measure and can set time delays on the sub (example below: main speakers +2 subs), it does make a big difference Jon...



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Older than I once was, younger than I'll be
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Andrew


Posted By: Fatmangolf
Date Posted: 27 Nov 2016 at 6:00pm
Yes I agree Andrew. I think I wrote on the forum about my past efforts measuring with REW to generate EQ solutions for an old Behringer digital unit I pressed into service to feed my subs when I had the GX100's at the front. I had to get the MIDI cables out! Shocked


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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Fatmangolf
Date Posted: 09 Nov 2017 at 5:37am
I revisited my work on the GX300 crossover in Spring 2017, finding the mid-boost feature was helpful on some congested mixes. I found the +1dB quite subtle and going straight to +2dB made them more like monitors but a bit full-on for relaxed listening! So I am thinking about resusing the switch but for one boost in between and trying a cut option. I may try +/- 1.5dB

The sub-bass I have addressed by trying positions nearer the back wall and prefer the sound to blending in a subwoofer in my room. Changing from spikes has helped too.

After a lot of experimenting I splashed out for a set of Gaia III isolation feet and am very glad I did. Significant improvement in the sound, clearer with more precise positioning of instruments, and better bottom end which I put down to the floorboards not joining in!



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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: ICL1P
Date Posted: 09 Nov 2017 at 8:23am
Originally posted by Fatmangolf Fatmangolf wrote:


After a lot of experimenting I splashed out for a set of Gaia III isolation feet and am very glad I did.


Do they just screw in in place of the spikes?

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Ifor
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Reflex M & ACCESSION M, CuSat50, Majestic DAC, a Proprius pair.


Posted By: Fatmangolf
Date Posted: 09 Nov 2017 at 6:01pm
Yes if you have M8 standard spike fittings or M6 or 1/4 inch, which are all in the box. The GX300 have an odd pitched M10 so I improvised.
 


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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: ICL1P
Date Posted: 09 Nov 2017 at 9:06pm
They are horrendously expensive. £400 for a pair of speakers!

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Ifor
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Reflex M & ACCESSION M, CuSat50, Majestic DAC, a Proprius pair.


Posted By: Fatmangolf
Date Posted: 09 Nov 2017 at 10:48pm
Yes I agree if the price is compared to a set of standard spikes or some gel pads - both products are fine at what they do and much cheaper. However £400 is not expensive compared to similar products to the Gaia, like Townshend Seismic bars, Stillpoints, etc.

Sadly unlike HFC there isn't a loan scheme but I would have returned the Gaia feet if they didn't work very well.


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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Fatmangolf
Date Posted: 13 Feb 2019 at 9:56pm
In January I started to look again at my GX300 crossovers. I use a handy program called Passive Crossover Designer which I feed with measurements taken with REW v5.1, both are freeware and really good in the latest versions in my opinion. I bought a U-MIK test mic recently and downloaded the calibration curve for my serial number and it led me to do a lot of driver and speaker testing before being ill.

REW's response curves, waterfalls, and other graphs are really interesting. I've written about them before in the room acoustics context so will not digress. I started to look at the distortion analysis this time and have been measuring various speakers in my collection with the sine wave sweep and also with two tone/intermodulation tests. Very interesting, especially when comparing closeup readings with listening position. The latter picks up more of the room's contribution obviously but also shows how being off axis can reduce the closeup distortion.

On my GX300, which I still enjoy, I am toying with adding the missing inductor to make the midrange LPF third order to match the third order HPF on the tweeters. I have rigged the extra part up to listen and to measure the impact, still not sure it's worth the admittedly limited effort to make the change properly. Temptation may overcome me yet...



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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Fatmangolf
Date Posted: 19 Feb 2019 at 9:21pm
Apologies for leaving this hanging. I will follow up on this potential development when I have a chance.


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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Fatmangolf
Date Posted: 02 Jul 2020 at 10:03pm
I did eventually rig up an A/B switching arrangement for that inductor feeding the midrange speaker. Very short cables which stayed in circuit but shorted out the new inductor.

I used a fixed position for a calibrated microphone and REW software to measure the frequency response and THD with and without. Miniscule difference, slighlty steeper rolloff and about 0.2% less THD. Which is probably inaudible. So I reverted to stock crossover, moved the test gear away, popped the inductors into one of my spares boxes, and then played more music which was nice.



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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Fatmangolf
Date Posted: 02 Jul 2020 at 10:10pm
An obvious development was wiring a low value resistor in front of the + terminal on the LF side of the crossover. I worked out that 2R7 would give me a gradual rolloff to about -3dB at around 50Hz, and it did. Subtle but audible on some records.

It is very similar to the approach above with the switchable resistor in front of the tweeter filtering of the crossover. The switchable response on the PMC Fact speakers inspired my experiments.



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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Fatmangolf
Date Posted: 10 Jul 2020 at 6:34pm
Now an interesting finding: you can make a simple tone control using your loudspeakers, essentially a 'tilt' control where you subtly alter the balance of bass and treble extremes. Please don't try this if your amp's manual has warnings about speaker connections or you are nervous about breaking something by getting the wiring wrong.

I am assuming the speakers have separate LF and HF terminals and you normally link these together.

Please leave the link between the black or minus terminals in place and take out the red or positive link. You may wish to lower the volume on the amplifier first or put on standby if it is a valve amp. Check carefully that you are not shorting out the amplifier, the resistor should go where the link was between the two red/+ terminals. I take no responsibility if you do something silly or dangerous. If in doubt you shouldn't try this but take care and you may like the result.

Lets say you want to have more bass...
  • Plug the red/+ plug on the speaker cable from the amp into the LF+ terminal
  • Join the LF+ to HF+ using a 2.7 ohm high wattage resistor (7 or 10 watts wirewound will do for the test, you could use a higher value like 3.3 or 4.7 ohms for 8 ohm speakers)
  • Do this on both speakers sit down and listen for a while.
  • Then put things back the way they were and listen again.
The opposite wiring approach applies for getting more treble than bass, the red+ plug on the cable from the amp goes to the HF+ terminal and the resistor joins this to the LF+ so there is less bass.



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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Ash
Date Posted: 10 Jul 2020 at 6:43pm
You are using resistance to shelf one driver response above the other in a two-way? How does this affect the overlap of their responses at the crossover frequency? Raises XO point with more bass and lowers XO point with more treble?


Posted By: Fatmangolf
Date Posted: 10 Jul 2020 at 9:44pm
Roughly speaking yes Ash. I should add that lots of passive crossovers have a resistor to balance the two drivers' outputs. Nothing is perfect.
 


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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.


Posted By: Ash
Date Posted: 10 Jul 2020 at 9:52pm
Yes, very different types of driver so the easiest way to equate their sensitivities.


Posted By: Fatmangolf
Date Posted: 18 Mar 2021 at 7:14pm
I am preparing to hard wire in some of my mods to the GX300's. I'll probably make the 2R2 on LF switchable, perhaps with an extra cut option for late night listening. The MF boost switching is rarely used to I'll probably just keep the +2dB option as a midrange spotlight but I have been enjoying a lower MF crossover so may add this as a switching option. On the tweeter I do occasionally use the -2dB teble cut and am thinking about a similar boost by switching out the stock resistor.

Today I tried out a lot of the options in order to find which ones were interesting and listenable with the right material. Other options were either inaudible or not to my liking.



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Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.



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