Bessel vs Low Q for sealed sub, Also Amp Nady or QSC ?

[Jose_L]

Hi everyone,

I'm building a sub w/ a RL-p15d2 driver, I see alot of similar boxes w/ a 3.55^ft internal volume.(bessel)

But I'm told that using 4.5^ft for a lower system Q would sound better ?

What's the difference ?

Does a smaller size 3.5 have stronger bass w/ pop/electric music ?

Is a larger volume 4.5 better w/ orchestral/organ music ?

Which would be better for a mix of 50/50 HT/music ?

Now for a amp, I need a quiet amp because the amp will be mounted on the back of the enclosure w/ the faceplate facing up. I only have coax ran to the location where the sub will be placed.

Of course there is the K1 for $1050, but I'd like something less expensive.

What do you think of these amps ? quiet ?

Nady XA-2100 $280 2100w mono

QSC 1450 $400 1450w mono 4 ohm

QSC PLX1202 $600 1200w mono 4ohm

BTW, I plan on getting a Bassis later.

Thanks for all the help.

Regards,
Jose

[ThomasW]

IM(not so)HO one shouldn't target the performance of a sub for HT or music. A good sub is just that, good for any application. (My apologies to those in marketing trying to sell targeted to demographics :wink: )

If you use one of the box modeling programs it's pretty easy to compare the anechoic response for any "Q".

On the surface 0.707 looks like a nice choice for HT. But the models are anechoic. In the room the effects of room gain can make that alignment a bit boomy. If you choose a lower "Q" and later want more 'umph' it's no big deal to dial in a bit of boost to replicate the sound of a higher "Q" alignment.

All the amps you listed are all fan cooled. The Nady is probably the loudest.

Other than raw power output I doubt that your hear a noticable sound quality difference between any of them if all they're doing is powering a sub.

[Jose_L]

I think I found my amp.

How's this: Yamaha P2500S 1300w 4ohm mono

I went to a local music shop and it's virtually silent.

Anyone have experience w/ this Yamaha amp ?

Regards,
Jose

[---k---]

I was just about to post the amp question myself. I was wondering if any of the similar powered amps have more grunt per amp. You know, with receivers, we always hear that H/K and Denon are conseritive with thier ratings while Pioneer and some of the other lowend brands are a lot more agressive whith thier ratings. Everyone has probably heard that I clip my Nady XA-1100 when driving my two RL-P15 very hard. I wonder if one of the better brands like Crown or QSC would be any better than the cheep Nady. Do any of the amps hold up under heavy load better? Are the QSC amps worth the premium they demand? I've heard that Behringers are copies of QSC, are they?

Does anyone have any thoughts on the Crown XLS amps? Musiciansfriend.com has the 402 for $249 and 602 for $349 right now. (On friday, the 602 was mistakenly listed for $249 - I'm hopig my order doesn't get canceled.)

[ThomasW]

For Jose,

The Yamaha has a variable speed fan. You need to listen to the amp operating under load.

Ryan,

Your situation is two fold. Bad room issues EAT up power and you like to have the volume control to "11".

Watts are usually watts regardless of who's making them. Word is that the Crown CE and XLS amps aren't that good. Get a EP2500 and understand it has more than enough power to completely destroy your drivers.

[---k---]

Thomas,
You are of course correct about my two issues.

Good to hear your opinion of the XLS amp. I've heard some people elude to the same, but the number of Crown fans far outnumbers those with bad experances. The 602 is backordered for a month, so I need to decide if I should cancel the order, or screw with ebay try and make a $100 or so.

[ThomasW]

Crown makes some VERY VERY good gear. But the CE and XLS aren't stellar examples of their art. The designs where basically forced on Crown after Harman Int bought them and wanted to compete in the 'cheap' amp market.

People buying these 'think' they're getting a low cost version of the high-end Crown amps and they aren't. All they're basically doing is paying a premium for Crown's warranty, and getting an amp not significantly better than a Nady or Behringer..... :roll:

[Jose_L]

Ryan,

I did get to hear the QSC PLX 1202 at the music shop also.
It's very loud.

I think I'm all set, Yamaha P2500S $399 local. And I'll build a 21.5" cub w/ 1 1/2" mdf walls and a X type brace .. 3.6^ft roughly... w/ a RL-p15d2 ..

Thanks everyone for the help.

Regards,
Jose

[Ludvig]

I think I found my amp.

How's this: Yamaha P2500S 1300w 4ohm mono

I went to a local music shop and it's virtually silent.

Anyone have experience w/ this Yamaha amp ?

I have driven several of my old subs (Shiva, Peerless XLS, closed box and W-frame dipole) with this amp. The bass was muddy and not that detailed. It has also problems delivering power into 4 ohms load. Never got my amp deliver more than 130 W/ch into 4 Ohm. Maybe the low power output/muddy sound was because of something wrong with the unit. I didn't investigate it more before I sold it.

/Ludvig

[Jose_L]

Man,,,,,,

This is bumming me out ...

So I'm left w/ either a Dayton 1000w plate amp w/ a 20hz filter or a $1050 Crown K1 amp ..

Anyone know of a near silent pro amp ?

Thanks everyone..

Jose

[---k---]

Mod a pro amp using a computer fan, or by inserting a resistor???

Lots of people do it. I did it, and it worked well to quiet my Nady down. Here is how Chuck modded his behringer amp, the one Thomas told me to shut up and buy.

http://www.htguide.com/forum/showthread.php4?t=19024

[dyazdani]

I was going to suggest the same thing - that would open up more options.

You could also deal with the local place on the Yamaha, see if they'll let you get another amp if that one is a problem.

[ThomasW]

There are no fanless low cost prosound amps. Your plate amp options are Adire or the one from PE.

[steve nn]

On the surface 0.707 looks like a nice choice for HT. But the models are anechoic. In the room the effects of room gain can make that alignment a bit boomy. If you choose a lower "Q" and later want more 'umph' it's no big deal to dial in a bit of boost to replicate the sound of a higher "Q" alignment.

After having a chance to view allot of material in different Q's, I would highly suggest you not let this quote slip by Jose. .55 is what I rested on myself with a curve. I can make the twins sound very close to vented options I've had in the past, but .55 to .6 really stands out imo with a little boost in the lower FR's.

[Jose_L]

steve nn,

So if you did it all over again you'd go say 4.5^ft ?

Thomas,

I may breakdown and get a K2, but will the K2 power
2 sep. sealed subs w/ a Bassis ? I know it will do 1 sub , but I want to make sure it will do 2 subs fine.

Because I wouldn't be able to afford a second amp..

Can someone explain the following taken from crown specs pdf :

"5.1.2 Out of Band Filtering

An 8hz high pass filter protects the amplifier and loads from subsonic frequencies. A 30kHz low pass filter offers protection from ultra sonics frequencies. "

Does this mean the operating range for this amp is 8hz-30kHz ? What happens if you set your crossover higher ?


Thanks everyone, your help is greatly appreciated.

Regards,
Jose

[ThomasW]

I may breakdown and get a K2, but will the K2 power
2 sep. sealed subs w/ a Bassis ? I know it will do 1 sub , but I want to make sure it will do 2 subs fine.

A K2 bridged will deliver up to 2500 watts when driving a 4 ohm load. That should be enough power for anyone unless you live in a concert hall

[steve nn]

So if you did it all over again you'd go say 4.5^ft ?

Nope! 4 cu ft per driver is just fine.

Does this mean the operating range for this amp is 8hz-30kHz ? What happens if you set your crossover higher ?

What you would wind up doing is disabling the filters so they don't get in your way. The K2 at 800 per channel would be very nice...If you go with the mono BASSIS.. even better. Pretty spendy though! I wish I had the K2.


RMS Power Output K-1 K-2
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4W Bridge-Mono 1,500W 2,500W
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Data Sheet 332k pdf 318k pdf
Thermal/Current Info 105k pdf 105k pdf
Owner's Manual Complete Owner's Manual For K Series Amplifiers
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[Mark Seaton]

Can someone explain the following taken from crown specs pdf :

"5.1.2 Out of Band Filtering

An 8hz high pass filter protects the amplifier and loads from subsonic frequencies. A 30kHz low pass filter offers protection from ultra sonics frequencies. "

Does this mean the operating range for this amp is 8hz-30kHz ? What happens if you set your crossover higher ?

It means exactly what it says. The amp starts to roll off near 8Hz. For most practical purposes it's virtually ruler flat to 10Hz. I'm not sure what you mean by crossing over higher? You did note that it says 8-30,000Hz, correct?

So far as in-box Q, once you plan on using a basis or other significant EQ, the absolute significance of the Q diminishes. There are some trade offs, particularly with the Fb of the driver in box, but if you're under a Q of 1.0 and you're going to be applying much EQ to extend the response, the resulting sensitivity vs. frequency is more important. A lower Q alignment for a given driver will of course usually be more efficient below Fb while a higher Q alignment can provide more output around Fb.

[ThomasW]

Although rated to 30kHz, our resident amp guy (Jon-what's his name?) was part of the design team for the Crown K series amps. He recommends limiting it's use in home audio to subwoofers or applications where the passband is lower than ~360Hz.....:wink:

[steve nn]

He recommends limiting it's use in home audio to subwoofers or applications where the passband is lower than ~360Hz.....

We could be approaching the edge of it's limit then. :lol:

[Jose_L]

Sorry, I was reading 30kHz and thinking 30Hz. ops:

So at least my box is set, 19x19x20" internal dimensions. ~4.18^ft ..

Now to mull over my amp decision. :Z

Thanks all,

Regards,
Jose

[steve nn]

19x19x20"

Without checking, that seems a little small Jose?

[steve nn]

That's only 2.75 cu ft Jose,.. factoring 1.25 for thickness. Cant go any less. You must of made a mistake in posting the dimensions or something?

[Jose_L]

Those are internal dimensions.

19 x 19 x 20 = 7220 ^inches = 4.18^ft

the walls will be 1 3/8" (3/4 + 5/8 ) mdf and the front baffel will be 1.5" mdf. That would make the outside dimensions:
21 7/8 d x 21 5/8 w x 22 5/8 h

I think this is right ?

Regards,
Jose

[ThomasW]

Yes, you're correct. People usually assume the published dimensions are OD, so you fooled everyone ....:wink:

Remember to compensate for the space occupied by the driver, any bracing, etc if the goal is to keep the internal space 4 cu ft

[Jose_L]

Thanks,

Man I just lost 2 chances on ebay for a K2. They sold for $730 and $799.

Regards,
Jose

[SteveCallas]

If you do get a Crown K series amp, make sure to leave plenty of open air above it. I had heard that they get warm, but I was at JonW's this weekend and we were testing his sub which is powered by a K1, and it was downright HOT! :E

[Jose_L]

Well, after looking at the EP2500 mod. It doesn't look hard to do.

Does the EP2500 take a computer fan ? I have several Panaflo 80mm L1 fans. It's a 12vdc fan.

http://www.directron.com/80l1a.html

Or I could put a Zalman fanmate which is a vari-speed controller between the stock fan.

Regards,
Jose