Sub crossover question

[spiralmind]

Hello, all. Just hooked up my tiny little sub (Def Tech Prosub 100) and was wondering what to set the low pass crossover knob at? It has a setting from 40 to 150hz. My speakers are DefTech BP10s (old model) and my integrated amp is a Marantz PM5005. Yes, the speakers are lined out of the sub, the sub is not hooked up separately. Is there a certain hz setting that works best, or is it up to personal preference? The setup is used mostly for listening to music, not movies or TV. Not sure if that helps. Thanks

 

[don philipe]

I would say set it to what sounds best to you.

 

[Grenadeslio]

I believe your BP10's actually play deeper than the sub if not mistaken.

Here found this on the net:

The BP 10 has a rated frequency response of 20 to 28,000 Hz, a nominal impedance of 6 ohms, and a sensitivity specification of 89 dB. It is recommended for use with amplifiers rated between 20 and 300 watts per channel: Price: $1,100 a pair.

Now back in the day I auditioned a pair of the BP20's, they literally rattled the windows in the retail store, that's thick glass. I'm not seeing how you will benefit from the sub but I would set the low pass filter as low as it will go and tweak from there.

 

[spiralmind]

Well, that's up in the air as a lot of my songs seem to lack substance in the lower frequencies. Maybe my integrated amp does not have sufficient power to drive the speakers? That would be a shame as it is a Marantz (PM5005) but still one of the lower-powered models.

 

[Poultrygeist]

A desirable characteristic of subs is the bass weight they add.

 

[enginedr]

If your speakers go down to 20hz I would use the sub to help tune the bass response in the room . Check out the U tube video Dr Earl Geddes distributed bass

 

[spiralmind]

A desirable characteristic of subs is the bass weight they add.

Agreed. The change is a subtle one, but don't most audiophiles look for subtle changes?

 

[n8dogg]

Hi spiralmind, I had a somewhat similar question to you and got some great information on this and on sub set-up in general. Not sure if you saw the post, you can find it here

http://audiokarma.org/forums/index.php?threads/trying-to-get-into-a-sub.829093/#post-11761405

(Anybody: please set me straight if I didn't post the link correctly...first time doing so)

 

[bimasta]

Maybe my integrated amp does not have sufficient power to drive the speakers?

Maybe not enough power to driver the woofers; they're hungry. Your sub has its own amp and can probably take up the slack.

I have NHT 2.9 speakers. Each has a 10" woofer, for frequencies below 100Hz (down to 27Hz). I'm only using a 75W amp currently and, just like you, don't like the bass. I've bypassed the woofers, and use 2 powered subs instead. Much better, vastly better. Also, without the 10" woofers, the NHT is a small 3-way monitor — the 75W amp drives them beautifully, truly ravishing — when it doesn't have to struggle with those woofers.

 

[donprice]

I would go with 60 to 80 Hz.

 

[spiralmind]

Maybe not enough power to driver the woofers; they're hungry. Your sub has its own amp and can probably take up the slack.

I have NHT 2.9 speakers. Each has a 10" woofer, for frequencies below 100Hz (down to 27Hz). I'm only using a 75W amp currently and, just like you, don't like the bass. I've bypassed the woofers, and use 2 powered subs instead. Much better, vastly better. Also, without the 10" woofers, the NHT is a small 3-way monitor — the 75W amp drives them beautifully, truly ravishing — when it doesn't have to struggle with those woofers.

Thank you, quite a wealth of information there. Do you have a low pass crossover? If so, what is it set at?

 

[bimasta]

Do you have a low pass crossover? If so, what is it set at?

Yes. It's set at 80Hz now, but still experimenting.

I don't know the extent of your knowledge in audio, and don't want to sound condescending. Speaker drivers don't just "cut off" at their specified frequency extremes. They roll off gradually. Their roll-off "slopes" can often be found in their specs, especially with a serious company like DefTech. It's expressed as "-6dB per octave" or "-12dB per octave", etc. The sub also has a slope. I try to find the midpoint of the two slopes, so their combined slopes level matches the speakers as a whole. If DefTech gives you the slopes, a simple arithmetic calculation will give you a very good starting point, then it's fine-tuning by ear. (BTW, 80Hz is the standard THX xover point for subs — I do pay observance to "standards", but not obeisance.)

Also, you have only one sub, so you will be losing stereo below a certain xover point. Doesn't matter much for movies, but it does for music.

My NHT's need 150W for the woofers to sound right. Even 100W didn't cut it, and my 75-watter not at all. But its SQ is superb so I stay with it, augmented with subs. Your Marantz presents the same problem. Using one sub will half-fix it. But that may be good enough; most people only use one sub. I think your sub costs about $500, so that would be the cost to have a second sub for full-stereo. You must weigh that against the cost of a more powerful amp to get better bass from your mains.

But as mentioned above, one sub may sound awesome when all adjustments are right. At no additional cost. And I think your sub has a 750W amp, so volume won't even be a concern.

Let us know how it works out!

 

[toxcrusadr]

^^ spot on. The problem with the previously stated frequency response of the speakers (20 - 28,000 Hz) is that such numbers are ALWAYS based on a limit such as -3 db or -6 db from the average response over the entire spectrum. In other words how far had it dropped off before they picked the lower limit frequency. When they report it without that number it's fairly meaningless. -10db would mean the output at that frequency is 10 times lower than the average over the rest of the spectrum. Hardly usable. I suspect the output of your speakers at 20 Hz has to be at least 6 if not 10 db lower, unless they are extraordinary speakers. Hence the suggestion to find more specific data or published response curves on them.

At 89 db those are not very sensitive speakers and it's very possible the amp is running out of gas trying to reproduce very low bass.

The 60-80 Hz suggestion sounds good to me as a starting point, in the absence of any other data. If it's too much even after fiddling with the sub's volume, I would go a bit lower rather than higher.

I assume you've checked polarity of your wiring so you're 100% sure you don't have a cancellation thing going on.

 

[Grenadeslio]

^^ spot on. The problem with the previously stated frequency response of the speakers (20 - 28,000 Hz) is that such numbers are ALWAYS based on a limit such as -3 db or -6 db from the average response over the entire spectrum. In other words how far had it dropped off before they picked the lower limit frequency. When they report it without that number it's fairly meaningless. -10db would mean the output at that frequency is 10 times lower than the average over the rest of the spectrum. Hardly usable. I suspect the output of your speakers at 20 Hz has to be at least 6 if not 10 db lower, unless they are extraordinary speakers. Hence the suggestion to find more specific data or published response curves on them.

At 89 db those are not very sensitive speakers and it's very possible the amp is running out of gas trying to reproduce very low bass.

The 60-80 Hz suggestion sounds good to me as a starting point, in the absence of any other data. If it's too much even after fiddling with the sub's volume, I would go a bit lower rather than higher.

I assume you've checked polarity of your wiring so you're 100% sure you don't have a cancellation thing going on.

They are extraordinary speakers, check out their reviews, these were marketed as not needing subs. They definitely reach down to 20hz without breaking a sweat.

 

[bimasta]

@spiralmind — I just saw photos of your BP10s. I had a chance to buy them at a Thrift shop about 10 years ago. Mint. But they were asking $500. Maybe a good price, but not a Thrift shop price. I negotiated, charmed, argued, begged — she wouldn't budge. So I didn't get them.

Three hours later a friend called, to boast about his new speakers. Yep, the BP10s. And what did he pay?

$100. That b---h at the thrift shop dropped the price by 400% when they didn't sell. And I'm much handsomer than my friend! He invited me over to hear them — "No effing thanks!!!"

Man was I mad! If you can't trust a thrift shop b---h, who can you trust?

 

[Grenadeslio]

Well, that's up in the air as a lot of my songs seem to lack substance in the lower frequencies. Maybe my integrated amp does not have sufficient power to drive the speakers? That would be a shame as it is a Marantz (PM5005) but still one of the lower-powered models.

Power plus speaker placement. Now I've never auditioned the BP10, but I have heard (felt) the BP20 reproduce gut wrenching bass to 18hz that put subs to shame, the 10 is just the little brother. I would play with speaker placement, these being bipolar makes this very critical. Then if still not getting enough bass from "certain" select music then maybe it's just not in the recording?

Also, once tweaking placement, if you have a buddy with a more powerful amp see what a couple of hundred watts on tap will do.

 

[E-Stat]

Yes. It's set at 80Hz now, but still experimenting.

While 80 hz is the generally accepted threshold for localization, note that speaker xovers are not of the brick wall variety like CD players.

Try this - play some vocal content and turn the main amp off with just the sub playing. Can you articulate anything? If so, I would lower the xover. If yours offers switchable slopes, another option would be to use 24 db/octave vs 12 db/octave. I have two set at 50 hz in the HT.

 

[Salomon]

I'm tinkering with the crossover on my EV Sentries and have a question about bypass caps for the woofer (28 - 600Hz 12db/octave) They have two 30uf caps on that leg of the crossover.

I'm new to altering crossovers. I bought Jantzen Superior Z-Caps in the mid leg and I'm wondering what you guys think would be appropriate for the woofer leg.

 

[toxcrusadr]

If those speakers are so great - and I don't dispute it - why does the manuf. not put out more complete data on them? Even the current model only has the owner's manual available online, which has the same type of description for the freq. response range - no -db points, no curves. There are not many speakers that can reach 20 Hz with usable volume, especially that size of speakers. They ought to crow about it, and one way to do that is to publish usable data.

But I digress. What was the question?

 

[Grenadeslio]

If those speakers are so great - and I don't dispute it - why does the manuf. not put out more complete data on them? Even the current model only has the owner's manual available online, which has the same type of description for the freq. response range - no -db points, no curves. There are not many speakers that can reach 20 Hz with usable volume, especially that size of speakers. They ought to crow about it, and one way to do that is to publish usable data.

But I digress. What was the question?

I can only speak from personal experience.

At one time, 27yrs ago to be exact the BP20 was high on my list, they were highly touted by the rags of the time. I auditioned them, the bass output was phenomenal, but I was also interested in purchasing Carver gear and they carried Adcom. This led me to another sound store, my intention to return for the BP20's if the other store couldn't get them for me. Instead I was made an offer i couldn't refuse on a complete Infinity Modulus system, stands included. The Infinitys are still with me they're that great, I made a great choice.

I've always wanted to get a pair of the Def Techs, especially the small Monitor 450, another I've heard, and it's tiny size just amazes me the bass output.