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Alto TS315 - normal for it to hiss?
Old 2 weeks ago
  #1
Gear Head
 

Alto TS315 - normal for it to hiss?

Apologies if I've posted this in the wrong forum area, - mods please feel free to move if appropriate.

I've just taken delivery of my first PA speakers, two Alto TS315. I bought them to use as monitors at home for my Roland TD-17 electronic drum kit.

I was previously using a hifi stereo amp and a pair of Bose 301 Series II to surprisingly good effect, but thought I ought to get something with a bit more excursion capability and headroom to do the kick drum justice. Two TS315 are probably overkill but there wasn't a huge price difference between it and the smaller TS and TX models and I thought I may as well go for the one with the deepest low frequency extension.

These are my first active speakers, and my first PA speakers, so I have no idea what to expect. I hooked them up to my main hifi system just to make sure they were functioning properly. The first thing I noticed was how much these bad boys hiss, even when the gain is set really low. It is very audible from a distance of 2 metres and still quite audible from 4 metres. Is this normal for high-power PA speakers? By comparison, I can only detect hiss from my passive loudspeakers (even my 95dB/1W sensitive Tannoy Monitor Golds) if I put my ear an inch from the tweeter, and even then it's barely audible.

I've spoken to someone who recently bought a single TS312 for his TD-17 drum kit and he says he only hears hiss from it when he cranks the gain up almost full, so I'm wondering if my TS315s might be faulty (I suspect that's unlikely given that both of them hiss)? Do the TS312 and TS315 share the same internal electronics?

I took a frequency response measurement of each speaker from 50cm distance:



They seem pretty well matched according to the graph with a 1.5dB difference between the two in the mids and bass. Both exhibit a strange null/peak at 9kHz-10kHz. I thought it may have been an artefact from measuring at too close a distance but I'm pretty sure I can hear the discontinuity at a normal listening distance. Do you know if this is a characteristic of the tweeter used in the Altos?

Thanks in advance.
Old 2 weeks ago
  #2
Gear Nut
 

Yes, a certain amount of hiss will be inherent in any PA speaker system beause of the high sensitivity drivers... that CD could be 30db more sensitive than the tweeter in the 301s, and entry level systems like this are often a bit worse than average. Something to check... do you get the same level of hiss with nothing connected to the speaker? If not then a device with balanced outputs to drive the speakers would likely deliver better results.
Anytime speakers are measured indoors the room contributes, so some of the notches and peaks could be from that particularly at the low end, but the notch at 9-10khz is likely an artifact of the horn or the horn/driver combo.
Old 2 weeks ago
  #3
Gear Head
 

Quote:
Originally Posted by paul o View Post
Yes, a certain amount of hiss will be inherent in any PA speaker system beause of the high sensitivity drivers... that CD could be 30db more sensitive than the tweeter in the 301s, and entry level systems like this are often a bit worse than average. Something to check... do you get the same level of hiss with nothing connected to the speaker? If not then a device with balanced outputs to drive the speakers would likely deliver better results.
Anytime speakers are measured indoors the room contributes, so some of the notches and peaks could be from that particularly at the low end, but the notch at 9-10khz is likely an artifact of the horn or the horn/driver combo.
Yes, the hiss is present even when no input is connected and gain is set all the way to zero. It remains constant until the gain is cranked to 2/3rds and then it starts getting even louder (I wouldn't dream of cranking it this loud, just under 9 o'clock is plenty loud for me!).

Here is the farfield measurement from my listening seat in a room measuring 22 1/2 ft x 15 1/2 ft x 10 1/2 ft. The 9kHz dip is still present but the 10kHz spike is no longer an issue. Overall a remarkably well behaved frequency response. I am however quite surprised at the steepness of the LF rolloff below 55Hz. Does the TS315 have a built-in high pass filter that I'm not aware of?! It looks like EQing the bottom end will be a futile endeavour...

Old 2 weeks ago
  #4
Gear Head
 

Hi, I have the same speakers and I havent noticed any hiss.
Have you tried the ground lift buttom, or connect them to another power socket?

What cables are you using? Mono, stereo?
Old 2 weeks ago
  #5
Gear Head
 

Quote:
Originally Posted by jallejulius View Post
Hi, I have the same speakers and I havent noticed any hiss.
Have you tried the ground lift buttom, or connect them to another power socket?

What cables are you using? Mono, stereo?
I'm using mono 1/4" cables but the hiss is there regardless of whether a cable is plugged in. The ground lift button makes no difference to the level of hiss. I've tried them on different power sockets in different rooms and the hiss remains constant.
Old 2 weeks ago
  #6
Gear Head
 

1) Do they sound OK while playing?
2) dB level of the hiss?
Old 2 weeks ago
  #7
Gear Head
 

I have mine in my garage (1 car garage ~40 m^2).
I used an app called Decibel X to measure the noise/hiss from my speakers and I got the following results:
Woofer: 37 dB
Tweeter: 43-44 dB
Room noise with the speakers on: 30-31 dB measured in the middle of the room
Room noise with the speakers off: 30-31 dB , so no difference there. I can barley notice any hiss ~3 meter away from them
Old 2 weeks ago
  #8
Gear Head
 

Quote:
Originally Posted by jallejulius View Post
I have mine in my garage (1 car garage ~40 m^2).
I used an app called Decibel X to measure the noise/hiss from my speakers and I got the following results:
Woofer: 37 dB
Tweeter: 43-44 dB
Room noise with the speakers on: 30-31 dB measured in the middle of the room
Room noise with the speakers off: 30-31 dB , so no difference there. I can barley notice any hiss ~3 meter away from them
I'll check tomorrow and report back. How close did you have the mic from the drivers for the 37dB and 44dB measurements?

An ambient room noise of 31dB is exceptionally quite, is your garage an anechoic chamber?!
Old 2 weeks ago
  #9
Gear Head
 

Quote:
Originally Posted by ToTo Man View Post
I'll check tomorrow and report back. How close did you have the mic from the drivers for the 37dB and 44dB measurements?

An ambient room noise of 31dB is exceptionally quite, is your garage an anechoic chamber?!
I had my iphone's mic directly on the grill of the speaker, barley/almost touched, so as close as I could Cant tell how precise or scientific this test was but at least it's something

hehe I have carpets all over the floor since it's where we have our band practice
Old 2 weeks ago
  #10
Gear Nut
 

Quote:
Originally Posted by ToTo Man View Post
I am however quite surprised at the steepness of the LF rolloff below 55Hz. Does the TS315 have a built-in high pass filter that I'm not aware of?! It looks like EQing the bottom end will be a futile endeavour...
Yes that is typical for a PA speaker lowend extension is traded for high SPL capability. To get significant output down into the 30-40hz range a dedicated sub is required.
Old 2 weeks ago
  #11
Gear Head
 

Quote:
Originally Posted by paul o View Post
Yes that is typical for a PA speaker lowend extension is traded for high SPL capability. To get significant output down into the 30-40hz range a dedicated sub is required.
So the TS315 definitely has a fixed high pass filter built into it?

I checked out the specs for the TS315S (15" subwoofer) and the -3dB is 44Hz, the TS318S (18" version) is also -3dB @ 44Hz. Unless I'm missing something, that only extends the TS315 bass by a mere 6Hz (the TS315 -3dB point is 50Hz).

The modestly priced BK XXLS400 subwoofer I use in my hifi system is flat down to 20Hz with no user EQ applied (I suspect there must be EQ built into the amp plate to achieve such impressive extension). Am I barking up the wrong tree expecting a relatively compact PA system to deliver comparable levels of bass extension given the vastly higher SPLs required from PAs?

Old 2 weeks ago
  #12
Gear Nut
 

Quote:
Originally Posted by ToTo Man View Post
Am I barking up the wrong tree expecting a relatively compact PA system to deliver comparable levels of bass extension given the vastly higher SPLs required from PAs?
Yes. For the most part response that low is undesirable in a live music environment, larger rooms tend to have much longer reverb times which transforms naturally slow sub bass into nondescript mud. As a result very few PA subs reach much below 35hz and a 50hz f3 is common in "fullrange" PA speakers.
Old 2 weeks ago
  #13
Gear Nut
 

Quote:
Originally Posted by ToTo Man View Post
So the TS315 definitely has a fixed high pass filter built into it?
Likely yes, the woofer in this box would have very little excursion capability... maybe only 3-5mm so it needs all the protection it can get.

Quote:
Originally Posted by ToTo Man View Post
I checked out the specs for the TS315S (15" subwoofer) and the -3dB is 44Hz, the TS318S (18" version) is also -3dB @ 44Hz. Unless I'm missing something, that only extends the TS315 bass by a mere 6Hz (the TS315 -3dB point is 50Hz).
With a sub in the system the mains would typically be high passed at anywhere from 80-120hz depending what models are being used. This effectively converts the system into a 3-way which means there is no need for anything larger than an 8"-12" "mid" depending how much overall SPL is desired. The 15" 2-way PA speaker and especially cheap versions are really only good for those that want the loudest and easiest to deploy one box solution, they trade away every other performance parameter to achieve that which would make you think they wouldn't be very popular, but the irony is they are probably the best seller in every manufacturers lineup.
Old 1 week ago
  #14
Gear Head
 

Here are RTA measurements taken in RoomEQWizard using a calibrated UMIK-1 USB mic. The first two graphs are with the mic 1cm away from the Altos tweeter and show the difference between the background noise of the room with the speaker off vs speaker on. As you can see, the hiss causes the noise floor to increase by more than +20dB at some frequencies:





The third graph shows the difference in noise floor at the listening seat when both speakers are off vs both speakers on. There doesn't appear to be much difference, but I suspect this is because the electrical noise floor of the UMIK-1 is masking the true acoustical noise floor of the room. The noise floor with the speakers powered on sounds much louder to my ears than just a +2dB difference.

Old 1 week ago
  #15
Gear Head
 

Hm, that seems like a lot more than what I got?

Do they sound fine while playing?
Old 1 week ago
  #16
Gear Head
 

Quote:
Originally Posted by jallejulius View Post
Hm, that seems like a lot more than what I got?

Do they sound fine while playing?
They sound great when cranked, very clear any dynamic, but at 'background music' levels the hiss tends to intrude on the music. Of course, these kind of speakers aren't supposed to be used at low volumes I suppose! I've sent an email to Alto for advice.
Old 1 week ago
  #17
Gear Head
 

Quote:
Originally Posted by ToTo Man View Post
They sound great when cranked, very clear any dynamic, but at 'background music' levels the hiss tends to intrude on the music. Of course, these kind of speakers aren't supposed to be used at low volumes I suppose! I've sent an email to Alto for advice.
That's very strange. I often use these speakers at moderate listening volumes when I'm doing work (avoiding family ) in my garage, and I haven't noticed any hiss. My best guess is that it has something to do with your power outlets, but I have no idea. Have you tried to connect them to another room, or with/without any other devices turned off/on?
Old 1 week ago
  #18
Gear Head
 

Quote:
Originally Posted by jallejulius View Post
That's very strange. I often use these speakers at moderate listening volumes when I'm doing work (avoiding family ) in my garage, and I haven't noticed any hiss. My best guess is that it has something to do with your power outlets, but I have no idea. Have you tried to connect them to another room, or with/without any other devices turned off/on?
Yep, I've tried them in different rooms and connected to different power outlets and get the same thing. My house supply is pretty clean, none of my other audio equipment produces any hiss or hum.
Old 1 week ago
  #19
Gear Head
 

Have you listened to these Altos anywhere else, like in your local shop or at a friend's place?
Old 1 week ago
  #20
Gear Head
 

Quote:
Originally Posted by jallejulius View Post
Have you listened to these Altos anywhere else, like in your local shop or at a friend's place?
Unfortunately I don't know of anyone local that has them.

On Monday I emailed Alto's technical support for advice, I also emailed their UK distributor. No reply from either as of yet...
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