Stereo speaker distortion issue

[camdoogy]

Greetings. I have a dumb question, and I have searched and cannot find the answer. I have a 2ch system with dual subs, a Schitt Freya preamp, and Schiit Vidar amp. I stopped running monoblocks a month prior thinking it would help my issue. I noticed that during some scenes in movies my tower speakers can't handle the bass and they get "distorted". What is my best option to implement a crossover for my Polk signature ES60 towers? I think that's the issue from what I have read, and I do not feel the need to put money into an AVR that I will not fully make use of. Thanks in advance for any solutions to this issue.

 

[DVDdoug]

I assume your subs are active/powered?

Many active subs have a built-in pass-through crossover that cuts the bass to your main amp.

If your subs don't have a crossover, you can buy an active crossover or the miniDSP is popular with people here.

and I do not feel the need to put money into an AVR

With an AVR you'd get the "point one" LFE channel with movies. Without a surround decoder you're only getting the regular bass.

 

[camdoogy]

I assume your subs are active/powered?

Many active subs have a built-in pass-through crossover that cuts the bass to your main amp.

If your subs don't have a crossover, you can buy an active crossover or the miniDSP is popular with people here.


With an AVR you'd get the "point one" LFE channel with movies. Without a surround decoder you're only getting the regular bass.

Thank you. I'll look into the miniDSP.

 

[Chrispy]

How are you determining this "distortion"? A crossover would be a good start in any case for bass management.

 

[OldHvyMec]

I would make sure all the driver securement screws were tight, and there were no air leaks, or mechanical issues FIRST. You might be surprised. I've fixed or tighten at least 100+ drivers for people through the years. A few of those were Polks too. I've fixed at least 20 pairs that were tossed because of loose drivers too.

Is it both speakers or just one and can you recreate the distortion by replaying the scene/music?

THEN set the XO to block from 60 hz down to the mains.

I personally would never use a head preamp that didn't have basic tone controls and at least some type of rumble filters for turntable or poorly recorded CDs/Records with bloated sub/bass. I can think of one person/album in particular who is known for WAY too much BASS. Tammi Neilson "Rainmaker" I think she was trying to blow out people's subs/bass drivers.

I picked up a Fosi ZP3 to see how they are built/work. Bass, Treble, and Balance. Neutral as can be with everything set flat. XLRs/RCAs. I think it has sub out in RCA. I didn't use sub out, I split the XLRs R/L for a pair of subs. I'm using VMPS 626R with a pair of Fosi ZA3s power amps in mono. The 626s can seem bass-heavy if you get them to close to a front wall. They are rear ported. That is something else to look at if it was too bass-heavy with most music, whether in movies CDs, records, etc.

But distortion, rattling, or just in general sounding bad or off, I always look to mechanical issues FIRST. Loose drivers, blown or loose surrounds, reconnect the speaker cables and make sure everything is tight, no straggler wire on stranded cabling. A good looking over and make sure everything is correct/tight.

BTW you can use a 1/4-3/4" hose to listen for air leaks or to locate rattles/noise in a cabinet or at the port opening. Just turn the sound down and slowly move the end of the hose around the drivers edge with the other end close to an ear. Check the port for rattles and the speaker binding post area. Check ALL the drivers including the tweaters in case they are using a sealed back motor vs a cabinet enclosure/pocket.

Happy hunting and fixing.

Regards

 

[Wesseling Audio Lab]

What do you get when towers are run without the subs

 

[camdoogy]

How are you determining this "distortion"? A crossover would be a good start in any case for bass management.

It’s a “crackling sound” during heavy bass scenes.

 

[camdoogy]

What do you get when towers are run without the subs

No change.

 

[Wesseling Audio Lab]

What I'm thinking about is a 3way that I designed that has only one 6-1/4" basic woofer crossed at 150hz to a 5-1/4" mid woofer. It can go quite loud without audible signs of stress. I can't imagine any high volume issues with the ES60 design.

Maybe defective woofer? Twice I've experienced defective woofers. Recently with a new 6-1/4 Dayton woofer that was crackling with the right bass energy.

 

[MAB]

No change.

Both Polks? Or just one?

Do your subs use a high-pass crossover to filter the bass from your Polks?

 

[camdoogy]

Both Polks? Or just one?

Do your subs use a high-pass crossover to filter the bass from your Polks?

Both of them. I have the subs connected via RCA from the preamp. No crossover in use.

 

[MAB]

Both of them. I have the subs connected via RCA from the preamp. No crossover in use.

OK. I’m fairly certain you are overdriving the Polk woofers at high SPL and you are hearing the woofers bottom out.

If so, this has the potential to damage the woofers, depending on the motor design.

What make and model subs do you have? You should be using a high-pass crossover on your mains, combined with a low-pass for the sub. Is this possible with your subs?

 

[camdoogy]

OK. I’m fairly certain you are overdriving the Polk woofers at high SPL and you are hearing the woofers bottom out.

If so, this has the potential to damage the woofers, depending on the motor design.

What make and model subs do you have? You should be using a high-pass crossover on your mains, combined with a low-pass for the sub. Is this possible with your subs?

I have a SVS PB-1000 Pro and a PB-1000. Same subs, but the pro can use the SVS app for settings. I think I need a separate piece of gear to use a crossover. This is frustrating because I’ve had receivers in the past but I sold them because music quality became a priority for me so I went 2ch. Now I feel like I should’ve kept them or got an AVR with pre-outs so I could still use my amps.

 

[OldHvyMec]

A list of inline HP RCA filters, for line-level adjustments. Just work the problem and don't throw money at it untill you have an idea what is wrong. Again make sure you don't have a mechanical issue and tone controlls go a long ways IF you don't have broken parts in the speakers. Locate the noise using a 1/4-3/4 hose. 8 bass drivers including the two subs is a lot of sub/bass potential.

The Polks are a 2 way right? Physically push the driver cones all the way in and make sure something is not rubbing. Be gentel but don't worry about doing it. I've never hurt one and I've installed a lot of surrounds and checked for clearance even more times than that. I remove drivers and give them a shake too. You can break stuff loose like glue/adhesive in the VC pocket and like I said it can be in both cabinets. A good visuall inspection goes a long ways.

I've had to fix speakers more than one time for customers that managed to harm the same drivers in both cabinets at the same time. Don't rule out something mechanical untill you locate the niose first.

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Regards

 

[MAB]

I have a SVS PB-1000 Pro and a PB-1000. Same subs, but the pro can use the SVS app for settings. I think I need a separate piece of gear to use a crossover. This is frustrating because I’ve had receivers in the past but I sold them because music quality became a priority for me so I went 2ch. Now I feel like I should’ve kept them or got an AVR with pre-outs so I could still use my amps.

Sorry, I neglected to look at your signature.

I see, the SVS subs don't have high-pass crossovers.
Also, makes sense that with and without subs results in the same noises coming from the Polks.

You have great speakers, amps, and preamp. The subs are very limited in features for integration.

An external crossover might be cheaper than starting over with an AVR.

Here is the likely problem. The Polks have good bass to below 80Hz, shelved down a bit.

The port maximum output is at ~40 Hz. It does a good job of making a nice shelved bass response that allow the speaker to be placed near room boundaries and sound good. In fact, the woofer barely does any work at ~40 Hz, the port is providing the majority of the bass output at the is frequency. Here is an example, a simulation of a single 6.5" Audax driver with my attempt at similar tuning:

Below 40Hz, the port and woofer no longer work together so nicely, and the woofer excursion becomes uncontrolled. Here is the excursion of that Audax woofer at just 10 Watts:

This Audax woofer is very unhappy with more than 10 Watts of power at 30 Hz. It's unlikely your Polk woofers have more than 5 mm of excursion. Most music doesn't have much content below 30 Hz. Movies do go well below 30 Hz.

I am hesitant to encourage you to spend more money. But here I go: A proper crossover is the best way to go with the SVS crossover set to flat. Using the mains without a high-pass crossover is just not going to provide the best bass. Alternately speakers with more SPL capability, but that won't fix your mains / subwoofer integration problem, and may actually sound worse.

In the meantime, you need to keep the Polks from hitting their limits. Plugging the port will help a bit. Here is the excursion of that Audax with the port completely sealed (solid blue line) compared to the port open (dashed turquois line):

 

[camdoogy]

Sorry, I neglected to look at your signature.

I see, the SVS subs don't have high-pass crossovers.
Also, makes sense that with and without subs results in the same noises coming from the Polks.

You have great speakers, amps, and preamp. The subs are very limited in features for integration.

An external crossover might be cheaper than starting over with an AVR.

Here is the likely problem. The Polks have good bass to below 80Hz, shelved down a bit.
View attachment 494294
View attachment 494287
The port maximum output is at ~40 Hz. It does a good job of making a nice shelved bass response that allow the speaker to be placed near room boundaries and sound good. In fact, the woofer barely does any work at ~40 Hz, the port is providing the majority of the bass output at the is frequency. Here is an example, a simulation of a single 6.5" Audax driver with my attempt at similar tuning:
View attachment 494293

Below 40Hz, the port and woofer no longer work together so nicely, and the woofer excursion becomes uncontrolled. Here is the excursion of that Audax woofer at just 10 Watts:
View attachment 494295

This Audax woofer is very unhappy with more than 10 Watts of power at 30 Hz. It's unlikely your Polk woofers have more than 5 mm of excursion. Most music doesn't have much content below 30 Hz. Movies do go well below 30 Hz.

I am hesitant to encourage you to spend more money. But here I go: A proper crossover is the best way to go with the SVS crossover set to flat. Using the mains without a high-pass crossover is just not going to provide the best bass. Alternately speakers with more SPL capability, but that won't fix your mains / subwoofer integration problem, and may actually sound worse.

In the meantime, you need to keep the Polks from hitting their limits. Plugging the port will help a bit. Here is the excursion of that Audax with the port completely sealed (solid blue line) compared to the port open (dashed turquois line):
View attachment 494319

Wow! I appreciate the detailed reply. Gonna start looking for an external crossover that won’t break the bank haha.

 

[MAB]

Wow! I appreciate the detailed reply. Gonna start looking for an external crossover that won’t break the bank haha.

Try stuffing the ports. It may help the excursion problem for movies.

Are you using the Vidar bridged?

 

[camdoogy]

Try stuffing the ports. It may help the excursion problem for movies.

Are you using the Vidar bridged?

Not at the moment. I thought going stereo would reduce the watts and help with the woofers bottoming out haha.

 

[MAB]

Not at the moment. I thought going stereo would reduce the watts and help with the woofers bottoming out haha.

It's quite a bit of power even in stereo to be fed a full-range movie, as can be seen from the simulation of the single Audax woofer. In your case, you have 3 of them playing bass. Still, they will go bananas with well under 100 Watts of 20 Hz movie effects.

The simplest setup would be something like a MiniDSP 2x4 HD with just one Vidar amp in stereo. The 2x4 HD (for example) would allow adjustable crossovers for high and low, and also a sharp cutoff below 30 or even 40 Hz to prevent the excursion.

More complex is a crossover with balanced outs if you want to use both Vidar amps in mono mode. You will have tons of power, but with the right crossover and filter settings, you can eliminate the bottoming out. The risk then would be frying tweeters.

I wish there were alternatives to MiniDSP. That being said, I am a big fan of their company and the gear they make. It's just a bit of a learning curve for some, since it has lots of features and it is easy to miss the basics. It helps to have a measurement microphone and analysis software like REW to evaluate what the heck is going on, and what you might do about it. One member @Keith_W has an eBook here on that topic.

TBH, I would try stuffing the ports first, just to see if I am making up a big story. If I am right, stuffing the Polk's ports should significantly reduce or even eliminate the distortion you hear on bass-heavy content. Find a track that distorts with the ports clear, then replay the track at the same volume with it sealed as best you can. Be very careful, but it is a test I think is worth doing before throwing good money after bad.

 

[camdoogy]

It's quite a bit of power even in stereo to be fed a full-range movie, as can be seen from the simulation of the single Audax woofer. In your case, you have 3 of them playing bass. Still, they will go bananas with well under 100 Watts of 20 Hz movie effects.

The simplest setup would be something like a MiniDSP 2x4 HD with just one Vidar amp in stereo. The 2x4 HD (for example) would allow adjustable crossovers for high and low, and also a sharp cutoff below 30 or even 40 Hz to prevent the excursion.

More complex is a crossover with balanced outs if you want to use both Vidar amps in mono mode. You will have tons of power, but with the right crossover and filter settings, you can eliminate the bottoming out. The risk then would be frying tweeters.

I wish there were alternatives to MiniDSP. That being said, I am a big fan of their company and the gear they make. It's just a bit of a learning curve for some, since it has lots of features and it is easy to miss the basics. It helps to have a measurement microphone and analysis software like REW to evaluate what the heck is going on, and what you might do about it. One member @Keith_W has an eBook here on that topic.

TBH, I would try stuffing the ports first, just to see if I am making up a big story. If I am right, stuffing the Polk's ports should significantly reduce or even eliminate the distortion you hear on bass-heavy content. Find a track that distorts with the ports clear, then replay the track at the same volume with it sealed as best you can. Be very careful, but it is a test I think is worth doing before throwing good money after bad.

I appreciate all of your insight and resources. I’m going to throw some t-shirts in there. They are odd down-firing ports that a pair of tube socks won’t fit, unfortunately.