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Placing speakers on top of subwoofers

andreasmaaan

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#61
So if I keep my ATCs, would a pair of these do the trick? Would I effectively be building something like the Revel F208s? I can then place the ATCs on top of these subs.
Without looking at the link in-depth, certainly looks like they would :)

Before you invest in new gear though, I'd see what improvements you can make with your current sub. Try making the crossover slopes steeper, and raising the crossover frequency, and see whether that gives you an improved sense of dynamics.

6dB/octave @ 80Hz is too low/shallow a crossover slope for a 6" woofer if you want to do more than moderate levels IMHO.
 

sergeauckland

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#62
So if I keep my ATCs, would a pair of these do the trick? Would I effectively be building something like the Revel F208s? I can then place the ATCs on top of these subs.
Those subs don't have any filtering for the mains, so you would still need some way of keeping frequencies below 100-120Hz out of the mains, and with a decent rolloff like 24db/octave. For that, a two way active crossover will be needed, or at least a high pass filter.

S
 

March Audio

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#65
I was thinking of the mid to tweeter transition, which in most two-ways is somewhat compromised. To get decent bass, the bass/mid unit will be larger than needed for MF, so by the crossover to the tweeter will probably have started beaming somewhat. This can be avoided by a tweeter that goes down to a few hundred Hz, but those are rare beasts (Manger for example) and certainly that's not the case with the ATC's tweeter or any similar two-way. A three-way loudspeaker will have crossover frequencies at around 300Hz and 3kHz with an MF unit of perhaps 4-5".

Incidentally, that particular ATC loudspeaker has an unusual bass/mid driver as the 'dust cap' is almost the size of the whole cone so will have much less of the beaming issue than other two ways with more conventional drivers. This is an excellent example of cat-skinning, insofar as if one can't get the tweeter to go down low enough, make the bass/mid go high!

S.
The dome arrangement probably won't make much difference to the dispersion, it's more about the size of the driver.

My research into into drivers when I was designing my 3 way DSP speakers found that two ways are always going to be a compromise. Also many 3 way speakers employ mids that are too large. My 7.5 inch bass drivers dispersion is only good up to about 1kHz, the 2inch mid just makes it to 5khz. Any larger mid would mean a lower crossover slap bang in the middle of our most sensitive hearing range.

I XO at 800Hz and 4800Hz
 
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sergeauckland

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#66
The dome arrangement probably won't make much difference to the dispersion, it's more about the size of the driver.

My research into into drivers when I was designing my 3 way DSP speakers found that two ways are always going to be a compromise. Also many 3 way speakers employ mids that are too large. My 7.5 inch bass drivers dispersion is only good up to about 1kHz, the 2inch mid just makes it to 5khz. Any larger mid would mean a lower crossover slap bang in the middle of our most sensitive hearing range.

I XO at 800Hz and 4800Hz
My, possibly flawed, understanding was that beaming was due to air particle movements caused by different parts of a cone causing cancellation by interference depending on the path length. As a dome pushes air away from its surface rather than pushing air into a 'focus' point in front, there would be far less cancellation, although still some. This is why dome tweeters have wider dispersion than cone tweeters, and indeed, dome midrange drivers more than normal cone midrange drivers.

If this isn't how it works, I'd like to know more.

S.
 

andreasmaaan

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#67
I think you're both correct here actually. Domes do have wider dispersion than equivalent sized cones, but only towards the upper end of their range (i.e. the frequency range at which the wavelength approaches the diameter of the diaphragm). So @sergeauckland I believe what you're saying here is spot on.

However, in terms of the frequency range at which the tweeter crosses to the mid, what @BE718 is saying is correct - there is unlikely to be any significant difference in dispersion as a result of the dome geometry, as the wavelengths in this range will be much wider than the diaphragm's diameter.
 
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stunta

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#68
Missed that!. That unit looks a 'proper' preamp! No phono stage though........
:)
S
Its a good preamp with a built-in DAC (including USB input). It lets you add filters which can be an advantage if you have multiple sources - back at my old place, I had filters applied for TT as well (signal converted to digital and back to analog). I wish it had a phono stage built in RIAA correction done in the digital domain since its anyway converting to digital.

Without looking at the link in-depth, certainly looks like they would :)

Before you invest in new gear though, I'd see what improvements you can make with your current sub. Try making the crossover slopes steeper, and raising the crossover frequency, and see whether that gives you an improved sense of dynamics.

6dB/octave @ 80Hz is too low/shallow a crossover slope for a 6" woofer if you want to do more than moderate levels IMHO.
I took measurements and applied filters which has dramatically improved the bass. I've also taken your suggestion and I using a 24db slope. Unfortunately I am unable to discern any difference at this point because I have serious issues with the room. There is a lot of smearing due to what I think is echo (or flutter?). If I clap my hands in the room I get this ringing like echo. The room has almost no furnishing right now (no floor rug either and the floor is laminate) . I will start a separate thread on this.
 

andreasmaaan

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#69
Its a good preamp with a built-in DAC (including USB input). It lets you add filters which can be an advantage if you have multiple sources - back at my old place, I had filters applied for TT as well (signal converted to digital and back to analog). I wish it had a phono stage built in RIAA correction done in the digital domain since its anyway converting to digital.



I took measurements and applied filters which has dramatically improved the bass. I've also taken your suggestion and I using a 24db slope. Unfortunately I am unable to discern any difference at this point because I have serious issues with the room. There is a lot of smearing due to what I think is echo (or flutter?). If I clap my hands in the room I get this ringing like echo. The room has almost no furnishing right now (no floor rug either and the floor is laminate) . I will start a separate thread on this.
Glad to hear the bass has improved at least :)
 

stunta

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#70
I am seriously considering buying two Rythmik FM8s and using them as stands for my ATCs. And oh, get some bass as well :).

FR for the two modes of interest:


Given the above, even if I use the subs in midbass mode (and use my current REL sub to fill in below 50Hz), will relieving my ATC speakers of sub-250Hz frequencies be a noticeable improvement?

Also, would I be better off using the FM8s in low extension music mode (would prefer this so I don't have to use a 3rd sub)?

Generally, I am thinking if this works, it will be easier to swap bookshelf speakers in and out versus getting a large pair of floorstanders.
 
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#71
Hey.

I believe in the pro audio world they refer to placing speakers on top of subs on the floor as GROUND STACKING. I believe this is common with some type of bracket that separates or isolates or decouples the speaker from the sub and the speaker is not in direct contact with the sub.

I just did the international Emmys Monday and they had a K Array setup this way.

Cheers
 

andreasmaaan

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#73
I’d go with the two subs in low extension mode. Much more likely to work well than trying to get so many different drivers crossing over correctly in such a narrow frequency range, and better in terms of room integration to have two subs producing low bass than one.

250Hz would appear to be too high a crossover point for those subs though. I’d try in the 120-150 Hz range.

I can’t recall whether you said you had a measurement mic?
 

stunta

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#74
250Hz would appear to be too high a crossover point for those subs though. I’d try in the 120-150 Hz range.
From 80Hz (current crossover), going up to 150Hz -> is that going to be a significant enough relief for my ATCs to make this worthwhile?

I can’t recall whether you said you had a measurement mic?
Yes, I do.

Thanks!
 

andreasmaaan

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#75
From 80Hz (current crossover), going up to 150Hz -> is that going to be a significant enough relief for my ATCs to make this worthwhile?


Yes, I do.

Thanks!
Moving the crossover point up an octave will make a significant difference - yes. You will reduce driver excursion by about half, which will take a lot of stress off the ATCs :)

And the measurement mic will be helpful in setting the crossover point/slopes and integrating the subs in-room.
 

watchnerd

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#76
I am trying hard to win the "dumbest question on ASR" award, so here goes...

The seating I have is low enough that if I place my ATC SCM-19 on my REL Storm III subwoofer (I have just one now and looking for a 2nd), the tweeter should roughly be at my ear height. Would this be a bad idea and if so, why?

Thanks

You're fine,

Studios do it all time. Audiophiles might worry about it. Pros don't:

 

svart-hvitt

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#77
From 80Hz (current crossover), going up to 150Hz -> is that going to be a significant enough relief for my ATCs to make this worthwhile?


Yes, I do.

Thanks!
Adding a sub or two with a crossover at say 100 Hz will add considerably (5 dB?) to your system’s SPL capability, and thus lower distortion when played at lower SPLs.

Make sure the subs can go as high SPL wise as main speakers...
 

stunta

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#78
Moving the crossover point up an octave will make a significant difference - yes. You will reduce driver excursion by about half, which will take a lot of stress off the ATCs :)
I did not realize this. Thank you!

There are two models - F8 and FM8. FM8 seems to give more flexibility so I can start its low end at 50Hz. This will allow me to play around with using my current sub to fill in below 50Hz. Pricing is roughly the same for the two models. So I am thinking of getting two FM8s. Anything I haven't thought of?
 

andreasmaaan

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#80
I did not realize this. Thank you!

There are two models - F8 and FM8. FM8 seems to give more flexibility so I can start its low end at 50Hz. This will allow me to play around with using my current sub to fill in below 50Hz. Pricing is roughly the same for the two models. So I am thinking of getting two FM8s. Anything I haven't thought of?
Having looked at the product page for those subs, it does seem that they may play ok up a bit higher than 150Hz like you first said. My bad. Anyway, you can play with the crossover point between 120 and 200Hz or so and see what works best. If you're going to try to cross them over to the larger sub at 50Hz, a higher crossover point to the ATCs is likely to work better.

I'm still not convinced you'll end up with better results with the 50Hz crossover, but there's no harm in experimenting.

I don't see anything else obvious that you've overlooked at this stage. I'm not hugely familiar with all these subs and speakers though. It definitely sounds like you're on a good path though.

Keep us posted...
 
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