Sierra Ribbon Towers and Safe SPL

[Pogre]

Hey guys, I've had my new towers for about a week now and am really enjoying them. Gorgeous sound.

I'm also using a pair of subs and cross them over at 80 hz, which is working really well. My normal listening volumes are 75 dB for music and usually less for movies and tv. However, I do like to crank up the volume from time to time and push reference levels for a song or 2.

So I did that with Chocolate Chip Trip, a drum solo with an aggressive kick that comes in around 2 minutes.



I sit 15' from my speakers and that song (among others with good bass) really seems to push the Sierra towers right up to the hairy edge of blowing a bass woofer (midrange also). I can see them moving, easily from where I sit 15' away. They move A LOT. The word "alarming" comes to mind... lol. I don't think I heard any clipping or distorting tho. I have a Monolith 7 amplifier and it's rated conservatively at 350 WPC into 4 ohms.

Am I becoming alarmed for no reason? Anyone else feel like they've hit limits with the towers? Dave, what say you? Should I use a higher crossover when turning it up like that?

[Pogre]

Well geez guys, don't overwhelm me with replies!

Okay, so I've made it to page 6 of the tower discussion thread and a couple things Dave said seem promising and I've been a little bit braver the last couple of days.

Loudspeaker power handling = massive! (we have yet to reach the speaker's limits but I would estimate it to be about 350 clean watts)

My amp tops out at just about 350 clean watts into 4 ohms. Not that it's my goal to push my amp to its limits or anything. I'm imposing limits and deciding how much closer I should move the MLP to the front stage.

Also, be sure to run them full range when you get the chance and let me know your thoughts on the bass response.

I agree, the imaging and detail is fantastic and many others have commented on how well they reproduce vocals. Don't be afraid to turn them up

Oh I've been playing them full range and crossed over, however I am a little bit afraid of turning them up due to my seating distance, which is 15'. I calculated (by "I", I mean my friend who put the spreadsheet together ) I would need about 660 watts to hit reference level peaks with 1 speaker, so 330 watts for both?

Calculated results based on Ascend specs, for one single speaker:

Input data required: Input data Unit
1) Speaker nominal impedance (Ohms) 4.00 Ohm
2) Sensitivity in dB/2.83 V at 1 Meter 90.00 dB
3) Seating distance (1 foot = 0.3048 Meter, 1 Meter = 3.281 foot) 4.57 Meter
4) Room gain for speaker placement near walls/corners, enter 0 to 3 dB max., to err on the conservative side 3.00 dB
5) Desired additional amplifier headroom (dB) Recommended minimum is 3 dB
6) Target SPL - THX reference is 85 dB, with 20 dB of headroom 105.00 dB
Calculated values from the input data: Calculated values
Sensitivity loss at seating distance (dB) 13.20 dB
SPL/W at seating distance calculated from the input data 79.80 dB
Amplifier power output based on 2.83 V and the assumed impedance at 1 Meter 2.00 Watt (W)
Power increase in multiples needed to achieve target SPL 331.46
Power increase in dB needed to achieve target SPL 25.20 dB
Calculated amplifier output power required:
For the target SPL at seating distance 663.66 Watt (W)

I'm getting A LOT of excursion from all 3 drivers the couple of times I've tested reference level (each time with 80 hz crossover). Everything still sounds clean and I'm not hearing any clipping, but I can't tell if they're running out of steam or not and I'm kind of afraid to push them that hard.

[racrawford65]

I think this is 660 watts for each speaker not 330.

Also, from the Tower spec page, it's 4 ohms minimum which is different than nominal. If you look at the plot on the measurements page, you'll see impedance looks to be 5 ohms up to 1KHz (with a peak to about 10 between 50 & 90 HZ), and then another peak between 1-3 Khz to about 13 ohms then from 3Khz on up around 8 ohms.

I'd suggest moving closer or, Heaven forbid, turn it down :-)

[curtis]

I usually stay out of thread in regards to "reference level" because the term has lost its meaning, and I don't fully grasp the infatuation with it. Reference level was developed as a movie mixing standard for sound in commercial theaters.

There are even some old forum posts on the internet that has Tomlinson Holman (the TH in THX) stating that reference level in a home theater is too loud because the smaller space. I think he said it should be 4-6 dB lower. Also, reference level in a home theater is the major cause of sibilance. To me, this is clearly audible as you turn up the volume on most movies to "reference".

In fact, as the volume gets louder past a certain point, the worse your ears get at hearing/discerning "quality".

Mixing for a commercial theater vs home is quite different, and I have been told that not many movies are remixed for home release.

As for music, my understanding there isn't a reference level.

OK...off my soapbox.

[Pogre]

Let me simplify then.

I just want to know how loud is too loud for these speakers to handle. A max spl at 1 m would be enough for rme to calculate the rest. Thank you.

[curtis]

Let me simplify then.

I just want to know how loud is too loud for these speakers to handle. A max spl at 1 m would be enough for rme to calculate the rest. Thank you.

I think that would be whatever these two numbers get you at 1 meter:

Maximum Continuous Power*	300 watts
Maximum Short Term Peak Power*	500 watts

[mikesiskav]

I remember this topic coming up in the past. Dave said he crosses over the mid-range to the woofers at a lower frequency than what some other speakers use so that the midrange driver covers as much of the vocal range as possible. This is why the towers sound so good with vocals.

[Beave]

I should add for clarity: My explanation of woofer excursion is for ported designs. So it applies to the tower woofers. But the tower midrange isn't ported. I think it's in its own sealed enclosure. I'm not sure whether it has an electrical high pass filter or if it just uses the enclosure for 'natural' rolloff. In any case that means the midrange excursion plot vs frequency is different from the woofer excursion plot.

I wonder if upping your crossover frequency to something like 120Hz or 150Hz will make a dramatic reduction in driver excursion. You could try it, at the same levels you're playing on the videos, just for curiosity, to see if the excursion is reduced by a lot.

But yea, the real solution is probably just to back off the volume a little! :-)

[mikesiskav]

I don't remember that lol.

[davef]

I don't remember that lol.

At that time, it was the latest Linkin Park release, you (or it was someone else) was impressed with how deep the bass went. It was very problematic for the Song Tower, but it also badly "popped" the woofers in our tower as well. I didn't own that Linkin Park CD so someone brought it here -- don't think it was Mitch but maybe.