FL8 or FL12 for Acoustats?

[LabLover]

I have the Acoustat Spectra 33's and they are a great speaker. My biggest gripe about them is that they are not very punchy in the lower regions. A friend had the Spectras as well and is using a dual set of the much smaller F8's. He said it makes an improvement, but can't really tell that they are playing. Do you think a set of of F12's would suit me? I do miss the low-end slam with prior speakers that I have had, ie: big Infinity's, Talons, etc. This would be for music only. I wiah Rythmyk amde them in 10's. Thanks for any help Jeff

 

[WaynePflughaupt]

Not sure exactly what we’re talking about here, because a search for “F8 subwoofer” gets totally different results than “FL8 subwoofer." Same with F12 / FL12.

That said, it should be a no brainer that generally speaking a 12” sub will blow away an 8” sub. Most decent 8-inchers bottom out at ~40 Hz, while most reasonably capable 12-inchers can easily get down to 20-25 Hz. Hopefully you can correlate that information to whatever kind of music you like to listen to to help make a decision.

Regards,
Wayne A. Pflughaupt

 

[TLS Guy]

We have had this come up with Acoustats before. I have researched the problem again.

Since you are using your speakers full range make sure the crossover switches on the back of your speakers are set to off.

First I need to discuss a misconception. What people perceive as deep bass is not. It is between 80 Hz and 600 Hz.

Now you friend failed with a commercial sub and you will too. There is likley NO commercial sub that will solve your problem.

Electrostatic speakers like your Acustats are di-pole radiatiators. That is to say the radiate equally front and back but with the front and back radiations 180 degrees out of phase. This out of phase condition creates a null at the sides and the characteristic figure of 8 radiation pattern. The rub is that this only occurs down to a frequency determined by the width of the panel. Below that point side of the panel transitions from a 1/2 space to a full space radiation. In other words two omnidirectional radiators out of phase, with severe cancellation. Your speakers are 31.5 inches wide, so this transition point is a little over 150 Hz.

To have decent bass each panel would need to be 12 ft wide!

In addition electrostatic panels exhibit severe dynamic compression in the lower octaves due to displacement limitation. This is why they sound thin and lack slam as you say.

In addition your speakers have a cap in the power supply cutting them off pretty much below 60 Hz to prevent damage.

So to work you need a crossover in the 150 to 200 Hz range and two subs with bandwidth from at least 30 Hz, and preferably lower out to 1 KHz, placed in close proximity to each speaker.

Acoustat used to produce a sub like this. The high pass filter is switched in by the switches in your speakers. The subs which contained the low pass filters connected to the speakers from the full range sub output jack.

Here is the measured response of this set up from stereophile.

You can see there are combined electronic and acoustic slopes creating a crossover centered on 300 Hz. To make this work the sub does need a response to 1 KHz as you can see. This one just got in under the wire, so to speak, as the sub cone has a break up mode between 1.2 and 1.8 KHz. That sub gained useful extension to 30 to 40 Hz range.

Ideally a sub for an electrostatic panel should be a di-polar sub like the one produced by Gradient for the Quad 63 ESL. Constructing this for your speakers would be a complex undertaking.

However you could reproduce the original Acustat solution and improve it.

You would need forward facing subs with linear output to 1 KHz. It needs to be passive.

You need a preamp and a couple of two channel power amps. You will need a two channel two way electronic crossover like this one.

I don't think you will find an off the shelf passive sub that will do this, but you might if you look.

If you can accomplish this you will succeed where your friend failed.

Remember electrostatic loudspeakers are not high spl devices and totally unsuited to rock music.
http://www.music-group.com/Categories/Behringer/Signal-Processors/Crossovers/CX2310/p/P0132/Features

 

[Irvrobinson]

First I need to discuss a misconception. What people perceive as deep bass is not. It is between 80 Hz and 600 Hz.
range.

Mark, I don't know anyone who knows anything about audio and thinks 80Hz is deep bass. What are you thinking? The thwack of a bass drum? A bass drum does have higher frequencies along with the deeper stuff, but few of us are so naive as to think 80Hz is deep.

 

[TLS Guy]

Mark, I don't know anyone who knows anything about audio and thinks 80Hz is deep bass. What are you thinking? The thwack of a bass drum? A bass drum does have higher frequencies along with the deeper stuff, but few of us are so naive as to think 80Hz is deep.

I agree with you entirely about long time members of this forum understanding this. However the the point is that this poster thinks a traditional sub will solve his problem. It won't like it didn't for his friend.

 

[DukeL]

Researcher James M. Kates did a study that was published in the Journal of the Audio Engineering Society in which he showed that dipoles have smoother in-room bass than monopoles. And smooth bass = "fast" bass. Unfortunately dipoles can't pressurize a room, so while dipole subs are certainly smooth, they don't deliver the impact that good box subs can. I used to own Gradient dipole subs with my Quads, and while they blended well, they didn't have solid impact.

Now suppose we start out with a virtually perfect subwoofer, +/- 1 dB across the bass region, but then place it in a room. No matter how carefully we position it, we cannot escape the room imposing huge peaks and dips on the response, such that we may well end up with +/- 6 dB or worse. So unless we take the room into account somehow, it really doesn't matter how good the sub is all by itself. While there are audible differences between good subs, those differences pale in comparison to what the room does to them. The main problem is the room, so let's deal with it.

How about bass traps? Long wavelengths are hard to absorb, so the amount of real-world improvement we'll get from bass traps is modest in relation to the magnitude of the peaks and dips the room is inducing.

How about EQ? We can equalize the response to be very smooth at the microphone location (assuming we have enough headroom to fill in the dips), but the response will become worse elsewhere in the room, because the room-interaction peak-and-dip pattern changes significantly from one listening position to another within the room.

You are already well ahead of the game to be thinking in terms of using two subs, because (if they are spread out) they will each produce a unique peak-and-dip-pattern, the sum of which will be considerably smoother than either one alone.

So two subs will be smoother than one, but still not as smooth as two dipoles. However, four subs will be comparable in smoothness to two dipoles, and therefore will blend well and extend the dipole's "speed" (remember smooth bass = "fast" bass) all the way down, but with impact. That smoothness won't be limited to the sweet spot either, but will hold up well pretty much throughout the room.

So my suggestion is, take it to the next level and look into four small high-quality subs as a more dipole-friendly and room-friendly alternative to two more powerful subs.

 

[davidbeinct]

We have had this come up with Acoustats before. I have researched the problem again.

Since you are using your speakers full range make sure the crossover switches on the back of your speakers are set to off.

...

Electrostatic speakers like your Acustats are di-pole radiatiators. That is to say the radiate equally front and back but with the front and back radiations 180 degrees out of phase. This out of phase condition creates a null at the sides and the characteristic figure of 8 radiation pattern. The rub is that this only occurs down to a frequency determined by the width of the panel. Below that point side of the panel transitions from a 1/2 space to a full space radiation. In other words two omnidirectional radiators out of phase, with severe cancellation. Your speakers are 31.5 inches wide, so this transition point is a little over 150 Hz.

To have decent bass each panel would need to be 12 ft wide!

In addition electrostatic panels exhibit severe dynamic compression in the lower octaves due to displacement limitation. This is why they sound thin and lack slam as you say.

In addition your speakers have a cap in the power supply cutting them off pretty much below 60 Hz to prevent damage.

So to work you need a crossover in the 150 to 200 Hz range and two subs with bandwidth from at least 30 Hz, and preferably lower out to 1 KHz, placed in close proximity to each speaker.

Acoustat used to produce a sub like this. The high pass filter is switched in by the switches in your speakers. The subs which contained the low pass filters connected to the speakers from the full range sub output jack.

Here is the measured response of this set up from stereophile.

You can see there are combined electronic and acoustic slopes creating a crossover centered on 300 Hz. To make this work the sub does need a response to 1 KHz as you can see. This one just got in under the wire, so to speak, as the sub cone has a break up mode between 1.2 and 1.8 KHz. That sub gained useful extension to 30 to 40 Hz range.

Ideally a sub for an electrostatic panel should be a di-polar sub like the one produced by Gradient for the Quad 63 ESL. Constructing this for your speakers would be a complex undertaking.

However you could reproduce the original Acustat solution and improve it.

...

Remember electrostatic loudspeakers are not high spl devices and totally unsuited to rock music.

Thanks for that detailed explanation, I came here because I am currently searching for a subwoofer solution for my Acoustats. I have some questions based on your post. I have Acoustat Model 3s, which are, I am pretty sure, similar in size to the Spectra 33.

Firstly, let me say that I am not attempting to get into any internet arguments. I recognize the limits of my knowledge, but I also don't understand if what you have posted above applies equally to all 'stats.

First question, do all Acoustats have the cap of which you speak? I ask because mine have useful bass, according to a cheap AT RTA on my iPhone, down to 32 Hz (albeit not a lot, like 10 dB down). They definitely have bass, quite a bit, both measured in my seating position and right in front of the speakers, at 63 Hz, so that leads to question two, how does that jibe with what you are saying about bass cancellation from the transition point of 150 Hz?

My current thoughts are to start with on SVS SB-13 Ultra, and as funds and WAF become available, move to a second. I have a semi-dedicated music room so funds are a bigger issue than WAF, but that does matter too.

I have more questions but rather than belabor the point I'll stop for now and ask, should I start a new thread or continue in this one? It seems pretty darn close and I think I and the OP are looking for a lot of the same answers.