Crossover Mods to Increase Bass Level?

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I bought a set of speakers (Sony SS-M7A) that have less bass that I'd ideally like. I'm not talking about going below its spec'd low limit of 50Hz. I'm talking about just increasing the relative level of output coming from the bass driver.

The midrange/bass crossover point is 300Hz, so the bass driver covers ~50-300Hz.

The crossover for the bass driver seems to be limited to a couple of caps and a couple of inductors. The small caps, I believe, are bypass caps for the bigger electrolytic caps.

I don't know anything about crossover design, but is it possible to increase bass output by modifying the crossover component values?

Pic of crossover is attached
 

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I'd forget about adjusting the crossover without measurements.

Are they sealed or ported? If ported, you could make the port shorter. It will increase the level but at the expense of low frequency extension.
If they are sealed, reducing the internal volume of the bass driver will have the same affect as shortening a port.
 
And here he is! LOL

I was wondering if these are sealed or ported myself, Matt. :)

Not everyone likes closed box, but they may be bassier near a wall.

I hear tell these are Peerless polycones, well that is fairly interchangeable with Vifa P21WO-20-08 in the Tymphany world:
Vifa P21WO-20-08 Diameter 215mm

That driver is capable of doing reflex well enough. Must be about 1.5 cubic feet. And I suppose you could do some crossover adjustment for more bass subjectively. But that presupposes far more detailed knowledge of the system design than most people can garner.

For sure, this is a highly competent speaker. My Sony amp has a button called DBFB, Dynamic Bass Feed Back IIRC, which turns any speaker into a bass monster!
 

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+1 for measurements.

Keep in mind, to increase bass, you have to loose everywhere else. That is, you need to loose sensitivity in the rest of the speaker. It is not impossible to do, but you need an entirely new crossover, and to do that you need to be able to analyze the drivers.

You are much much better off with a tone control or EQ.

Best,

E
 
Can't imagine crossover components affect deep bass at all. It just whizzes straight past the filter at low frequency.

I do learn that Sony's DBFB button is very much a deep bass control.

Amusing picture of some Sony speakers here. It resembles a family photograph in some weird way. I think these have low WAF. The whole setup is something only the geekiest could love. :D
 

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Hi Steve!

Captouch is not expecting to affect the deep bass, just hoping to increase the relative level of output from the bass driver over its operating range.

I once re-capped a Wharfedale E50. The old ELCAP capacitor in the bass circuit was replaced with a new electrolytic.

The owner reported an increase in bass level and stated that he no longer needed to use the amplifier's loudness control!

I suspect that the old ELCAP was well out of spec.
 
Forgot to mention, replacing shunt caps with low ESR shunt caps can have unexpected consequences. Ideally you want to be able to measure the ESR before attempting replacements.

You can inadvertently reduce the impedance to the next driver up, causing a new depression in the FR.

Having said this, a number of people have reported improvements by creplacing electrolytics with film in this location, so I believe it is worth the effort and cost, if you don't go nuts with cap costs.
 
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Recapping might help if the bass capacitors have aged:

689694d1530461723-crossover-mods-increase-bass-level-ss-m7a-bass-crossover-jpg


I think I see a 50-100V NP wet electrolytic 68uF Radial there. Those are hard to find, because they are mostly axial types with a lead off either end. But if they are failing, it would increase the mid level in an unpleasant way.

We should mention that audio crossovers need non-polar aka bipolar types. Regular polarised electrolytics are entirely different animals. A polypropylene in 68uF would be expensive and large and tonally slightly different.
 
Thanks for all the answers. Replying to each below:

I'd forget about adjusting the crossover without measurements.

Are they sealed or ported? If ported, you could make the port shorter. It will increase the level but at the expense of low frequency extension.
If they are sealed, reducing the internal volume of the bass driver will have the same affect as shortening a port.

They're sealed. Hmm, not sure I want to compromise the low freq extension though. I was hoping to have my lunch and eat it too! ;)

And here he is! LOL

I was wondering if these are sealed or ported myself, Matt. :)

Not everyone likes closed box, but they may be bassier near a wall.

I hear tell these are Peerless polycones, well that is fairly interchangeable with Vifa P21WO-20-08 in the Tymphany world:
Vifa P21WO-20-08 Diameter 215mm

That driver is capable of doing reflex well enough. Must be about 1.5 cubic feet. And I suppose you could do some crossover adjustment for more bass subjectively. But that presupposes far more detailed knowledge of the system design than most people can garner.

For sure, this is a highly competent speaker. My Sony amp has a button called DBFB, Dynamic Bass Feed Back IIRC, which turns any speaker into a bass monster!

I think you have the driver pretty close to what's in this speaker. Pic of bass driver attached. It says P21WO-06, made in Denmark. This isn't my pic, but from someone who took apart the same speaker. I assume mine is the same.

+1 for measurements.

Keep in mind, to increase bass, you have to loose everywhere else. That is, you need to loose sensitivity in the rest of the speaker. It is not impossible to do, but you need an entirely new crossover, and to do that you need to be able to analyze the drivers.

You are much much better off with a tone control or EQ.

Best,

E

Yeah, I was hoping for just a level boost of the bass driver, but it makes sense that you would lose something in that effort. I think an EQ or tone control is probably the best way to address this too.

The photos on the net show the SS-M7A crossover fitted with polypropylene capacitors.

I wonder if this electrolytic version was an earlier variant?

To be clear, the midrange/tweeter crossover does use polypropylene caps, but the woofer crossover uses electrolytic probably due to the larger values. I didn't show the mid/tweet crossover because I'm very happy with the sound there, but it does use film caps with each one appearing to be bypassed with a smaller film cap. I uploaded a pic of the mid/tweet crossover so you can see what I mean. There actually are a couple of electrolytics (looks like 60uF and 150uF) in the mid/tweet crossover, but mostly film caps.

Accept the speaker as is and try to look for solutions in amplifiers. Simple tone control (bass boost) is possible.

Yes, I think that's what I'll have to do. More pragmatic approach.

Can't imagine crossover components affect deep bass at all. It just whizzes straight past the filter at low frequency.

I do learn that Sony's DBFB button is very much a deep bass control.

Amusing picture of some Sony speakers here. It resembles a family photograph in some weird way. I think these have low WAF. The whole setup is something only the geekiest could love. :D

Ha, ha, that's my room, though that was never intended as a permanent setup, just a family photo.

I thought/think the speakers actually look pretty cool and artsy, but then again, I am a geek, so who knows. My room doesn't look exactly like that anymore, but those are all my speakers. In all, from the Sony SS-Mx line, I currently have:

1 pair SS-M3 bookshelves (shown in pic), now in my office setup.
1 pair SS-M7 (shown in pic), now in another system
1 pair SS-M7A (subject of this thread)
1 orphan single SS-M7A (picked up earlier and used in a mono system)

My main system speakers are Aerial Acoustics Model 7B's now with no plans to change. But I do like the Sony SS-Mx line.

I plan to compare the SS-M7's to SS-M7A's over time and sell one of the pairs because as much as I love the line, I don't need THAT many. :)

Hi Steve!

Captouch is not expecting to affect the deep bass, just hoping to increase the relative level of output from the bass driver over its operating range.

I once re-capped a Wharfedale E50. The old ELCAP capacitor in the bass circuit was replaced with a new electrolytic.

The owner reported an increase in bass level and stated that he no longer needed to use the amplifier's loudness control!

I suspect that the old ELCAP was well out of spec.

Thanks for that feedback. I think given the age of the speaker, it's definitely worth recapping the electrolytics anyway. If it gives me a bass boost, that'll be a definite bonus.

Forgot to mention, replacing shunt caps with low ESR shunt caps can have unexpected consequences. Ideally you want to be able to measure the ESR before attempting replacements.

You can inadvertently reduce the impedance to the next driver up, causing a new depression in the FR.

Having said this, a number of people have reported improvements by replacing electrolytics with film in this location, so I believe it is worth the effort and cost, if you don't go nuts with cap costs.

I think the values are large enough that it may not be practical to replace the bass crossover caps with film, so I'll probably stick with electrolytics. I can't read the values, but I think they're probably pretty high (100uF or higher).
 

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Recapping might help if the bass capacitors have aged:

689694d1530461723-crossover-mods-increase-bass-level-ss-m7a-bass-crossover-jpg


I think I see a 50-100V NP wet electrolytic 68uF Radial there. Those are hard to find, because they are mostly axial types with a lead off either end. But if they are failing, it would increase the mid level in an unpleasant way.

We should mention that audio crossovers need non-polar aka bipolar types. Regular polarised electrolytics are entirely different animals. A polypropylene in 68uF would be expensive and large and tonally slightly different.

Yeah, I'll recap those. Can't hurt and given the age, probably a good thing to do regardless.

I've recapped quite a few speakers, so I'm aware of the need for NP/BP caps in crossovers, but I can see (and have heard of) people using polarized electrolytics in crossovers by mistake. Thanks for pointing this out.
 
This is all good fun, Captouch. You are evidently the Number One Sony speaker fan. And why not? They seem decent. :D

Lots of rugs and thick drapes help room acoustics IMO.

Thanks to your delving we might conjecture that the woofers are just some tiny OEM variant of the Vifa P21W0-20-08 Woofer: Vifa P21W0-20-08 Woofer

You could measure the magnet to be sure it's the same, but its certainly feasible that an approx. 6cm wide X 13cm long rear port in about 50L will get you an extra octave of bass. In fact reflex drivers do badly in closed box IIRC, because it pushes the Fc higher than the Fs.

I am no great shakes on ports, just usually look at similar drivers for the figures, here a very familiar one: W 200 S - 8 Ohm | Visaton

Fc= Fs X Qtc/Qts= 28 X 0.7/0.33= Approx 60Hz in optimal closed box according to my guesstimate based on Morgan Jones' splendid article on closed box speaker calculations.
Arpeggio Loudspeaker - diyAudio

Ports are OK to try. Worst that can happen is you block them if they don't do what you hope. Reflex definitely produces some thunderous bass.
 
And here he is! LOL

I was wondering if these are sealed or ported myself, Matt. :)

Not everyone likes closed box, but they may be bassier near a wall.

I hear tell these are Peerless polycones, well that is fairly interchangeable with Vifa P21WO-20-08 in the Tymphany world:
Vifa P21WO-20-08 Diameter 215mm

That driver is capable of doing reflex well enough. Must be about 1.5 cubic feet. And I suppose you could do some crossover adjustment for more bass subjectively. But that presupposes far more detailed knowledge of the system design than most people can garner.

For sure, this is a highly competent speaker. My Sony amp has a button called DBFB, Dynamic Bass Feed Back IIRC, which turns any speaker into a bass monster!

I have to correct my earlier post. The woofer in my units aren't marked P21WO-06 like the ones in the picture I posted earlier.

Mine are labelled with the P/N: Sony 1-505-738-11 8ohms

Anyway, I'll be ordering the new electrolytics soon and will try them out.

No choice that I see except to order axials and bend one lead all the way around to get it around to the other side. . .or bend both down and mount the axial horizontally and put some insulation on the wires bending around and down.
 
You might be able to gain a little bass (0.5-1dB or so) at certain frequencies by replacing the air core inductor in the bass filter for an Iron core with significantly lower DC resistance.

That said, you are much better off just using tone controls / EQ at the amplifier to increase the amount of bass.
 
I have to correct my earlier post. The woofer in my units aren't marked P21WO-06 like the ones in the picture I posted earlier.

Mine are labelled with the P/N: Sony 1-505-738-11 8ohms

Anyway, I'll be ordering the new electrolytics soon and will try them out.

No choice that I see except to order axials and bend one lead all the way around to get it around to the other side. . .or bend both down and mount the axial horizontally and put some insulation on the wires bending around and down.
I'm not holding my breath on the capacitor fix. Old electrolytics hold their act together even after 30 years in my experience.

Whatever Sony currently call that bass, it's either a Vifa P21WO or it isn't. "A rose by any other name would smell as sweet..." as the Bard of Stratford put it. :D

Let's summarise. Closed box has a rolloff that is very characteristic in sound. I quite like it. Reflex at 24dB/octave works for most people these days. It can get more deep bass performance out of a smaller box.

Tone controls might be good, but it's still closed box at 12dB/octave. Really, the only game in town here, the main chance, for more bass is the reflex conversion. Everything I have seen so far suggests the bass is suitable.

These sort of threads often descend into Fear, Uncertainty and Doubt. The perfect being the enemy of the good because it never arrives. In fact 90% of the threads here disappear into inaction. We should mention that reflex works better with less box stuffing. The air has to be able to move.
 

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The Bass inductor will probably have a significant DC resistance being air cored and built to a budget, and also could be measured for inductance.
I found a cheap inductance and capacitance meter invaluable when trying to assess crossovers.
I have replaced a bass inductor with one with lower DC resistance in the past with pleasing results. Subjectively sounding much better to me!
 
The Bass inductor will probably have a significant DC resistance being air cored and built to a budget, and also could be measured for inductance.
I found a cheap inductance and capacitance meter invaluable when trying to assess crossovers.
I have replaced a bass inductor with one with lower DC resistance in the past with pleasing results. Subjectively sounding much better to me!

Lowering DCR in a coil is not in and of itself a good thing though.

Sometimes that is part of the baffle step compensation, at least how Troels and I do it. In other words, I carefully slect the DCR, as opposed to going with the lowest.

OP:

I should also mention I've heard good things of using Mundorf bipolar s, certainly a lot cheaper than film. :)

Best,

E
 
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